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Maku
klubiliige
Registreerunud 28.01.03
Asukoht: Eesti Vabariik
Kasutaja on eemal
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postitati 29.01.05 09:56
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Väljalase
Olgu, kui juba küsimiseks läks siis võiks siin teemas need pidepunktid lahti rääkida.
Mis on originaal 20v turbo väljalaske kollektoril viga (mitte RS2)? Samas paljalt kollektori vahetusega need hobused ei tule.
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torque addict / in the real world four wheel drive means safety and traction
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jõuvanker
klubiliige
Registreerunud 21.03.03
Asukoht: Harjumaa
Kasutaja on eemal
Auto: ´11a. A4 avant q. s-tronic 3.0TDI 176KW
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postitati 29.01.05 10:38
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Väljalaske kollektoriga seonduv
Postitust on muudetud Maku poolt
Mis on SMS-i poolt projekteeritud ( RS2-l kasutatav ) kollektori eelis, võrreldes stock S6/S4/S2 ( AAN, ABY, 3B ) kollektoriga?
Asi nimelt selles, et turboviive kui selline väheneb ( heitgaasiturbiini kiirem rakendumine ), heitgaaside pealejooks heitgaasiturbiinile on ühes
tasapinnas, st minimaalsed gaaside peegeldused/suunamuutused. Kuigi miinuseks võiks öelda kollektorikanalite ebaühtlase pikkuse.
RS2 väljalaske kolle 649,44 €
Pilt: ( SMS/ RS2 väljalaskekollektor )
Sellise kollektori puhul saab hetgaasiturbiin kiirema rakenduse, hetgaasid ei pea eriti energiat kulutama suurteks suunamuutusteks ( nagu on AAN, ABY,
3B kollektoritel, kus näiteks esimes ja viienda silindri kanalid on natukene halva tasapinnaga, heitgaasid peavad tegema läbi 90+90 kraadi muutuse, et
jõudaa lõpuks hetgaasiturbiinile )
Pilt ( stock S2/S4/S6, AAN, ABY, 3b )
Milline oleks siis hea ja suure potensiaaliga väljalaskekollektor?
Parimaks võiks lugeda taolist, millel on kõik kollektorikanalid enamvähem ühepikkused ning võimalikult ühes taspinnas just turbiinile jõudmise
taspinnalt. Üheks selliseks võiks olla Spotr Quattro väljalaskekollektor. Dahlbäck andmetel 450-460hp.
Pilt: ( Spotr Quattro väljalaskekollektor )
Liialt pikad väljalaskekanalid ei ole just kõige paremad, kuna toimuks tohutu heitgaaside jahtumine, peegeldused, rõhulangus kokkuvõtlikult jms.
Kuid siiski oleneb, et mis otstarbeks meil kollektorit vaja on, kas sprint ( 1/4 miil, 1/8 miil ) või hoopiski kestvussõit, ringrada? Sellest
lähtuvalt valitakse kollektor ning tehakse vastavad täiustused ( isoleerimine ). Igapäevakasutusse ja vahatevahel ka " paugutamiseks " soovitaksin
SMS-i nn RS2 väljalaskekollektorit või siis juba Sport Quattro väljalaskekollektorit.
Torukollektor
S1 [530 hp (390 kW) bei 7.200 rpm, 740 Nm/4.900 rpm] EVOII kollektor. S2 foorumis on ka teema S1 kolle kohta.
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lapsepõlvest alates meeldinud 20VT R5
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Maku
klubiliige
Registreerunud 28.01.03
Asukoht: Eesti Vabariik
Kasutaja on eemal
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postitati 26.01.06 20:35
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Väljalaskega seonduv
Härrased, räägime natuke summutajatest. Kui võtta kaks 2,5" ja ühe 3" paari meetri pikkust toru, kumma vastusurve ja kumma muratase on suurem?
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torque addict / in the real world four wheel drive means safety and traction
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Ivo
klubiliige
Registreerunud 08.01.05
Asukoht: Pärnu, Helsinki
Kasutaja on eemal
Auto: audi 200 20v quattro +S6 V10
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postitati 27.01.06 08:36
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exhaust system
seda tahaks teada, mida arvatakse kui kaks toru vedada 2,5"
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Maku
klubiliige
Registreerunud 28.01.03
Asukoht: Eesti Vabariik
Kasutaja on eemal
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postitati 27.01.06 10:30
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exhaust system
20v turbo 600+hp projektika summutaja!
Veel ühe projektika summutaja - PILT1, PILT1 (2 metalcatalysators 100cells, exhaust system by MTM & PKM 76mm
stainless, downpipe stainless 76mm modified for mounting the exhausttemp.sensor).
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torque addict / in the real world four wheel drive means safety and traction
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MaQQu
klubiliige
Registreerunud 15.12.02
Asukoht: Tallinn
Kasutaja on eemal
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postitati 27.01.06 11:44
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exhaust system
lihtne arvutus näitab, et 2 x 2,5" kogupindala on suurem kui 1 x 3" seega hingamine vabam. Kuivõrd seda vaja on, oleneb konkreetselt masinast,
mootorist.
Vastusurvetest ja muudest faktoritest tahaks isegi targemaks saada.
edit:
tegin siis need lihtsad arvutused.
1x2" toru = 4051mm2
1x2,5" toru = 6330mm2
2x2" toru = 8103mm2
1x3" toru = 9116mm2
2x2,5 toru = 12660mm2
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Maku
klubiliige
Registreerunud 28.01.03
Asukoht: Eesti Vabariik
Kasutaja on eemal
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postitati 27.01.06 12:00
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exhaust system
| Tsitaat: | Algselt postitas: MaQQu
lihtne arvutus näitab, et 2x2,5" kogupindala on suurem kui 1 x 3" seega hingamine vabam. |
Oleks see asi ainult nii lihtne. Kardan,
et see pole 1+1 matemaatika. Samas, mine sa tea..
Miks ma seda asja uurin, on see, et milleks panna 3" otsast lõpuni, kui saab parema tulemuse 2x2.5"? Vähe sellest, et vastusurve on väiksem, on ka
müratase talutavam. Näiteks C4 2,2t ongi originaalis lõpuni 2x55mm toru. S2 coupel on aga peale downpipe-i 2 toru ja peale katte suundub üheks toruks.
Turboga autode puhul kehtib minu teada idee, et mida kaugemal asetseb vastusurve turbost, seda parem.
Võtame näiteks Kristjani RS4. Tal on 2x2,5" keskel ja suundub üheks 3" kokku, kus on lõpus reso 3" sisse ja välja ja lõpus on pütt, milles 60mm-sed torud. Ehk
siis keskel on 1/6 võrra väiksema diameetriga torud ja edasi 3" ning viimane pütt on isegi kitsam, kui keskmine osa.
Paar sõna ka RS2 väljalaskest. Vaniko RS2-el (dahlbäck ei vaheta seda ka 360hp kiti puhul) on minu teada originaalsüsteem all. Lühidalt:
1. downpipe;
2. 2x55mm torud kattide kohal (peale downpipe-i);
3. enne eelviimast pütti läheb kokku üheks 2,5"
toruks;
4. eelviimase ja viimase püti vahel samuti 2,5" toru.
Samas ei saa öelda, et asi ainult V mootoris kinni oleks, sest ka S2 Coupel on sama ehitus. Sealjuures kaaluvad 2 toru kindlasti rohkem, kui 1 toru. Sellest lähtuvalt võiks tõesti tõdeda, et
2x2,5" on parem kui 1x3". Samas jällegist, kui lärmakat masinat ei soovi, siis miks mitte lähtuda näiteks RS4 Quattro GmbH loogikast.
BN-Bipes pakub järgmist:
1. Audi S2 Coupe
*Cat-Replacement-pipes, without TÜV, 2x60mm 120,50 €
*Stainless steel Frontsilencer, 63,5mm pipe dia, 363,50 €
*Stainless steel Rearsilencer, 2 x 76mm, 459,50 €
*Stainless steel Complete system 70mm pipe dia. 709,50 €
*Stainless steel Rearsilencer 2 x 76/20°LH/RH 1.421,00 €
*Stainless steel Complete system 2 x 76/20°LH/RH 1.669,50 €
2. Audi RS2
*Edelstahl-Vorrohr ab Turbo mit Serienkrümmer, ohne TÜV, 76/70mm, 562,00 €
*Edelstahl-Metallkat, ohne TÜV, 2x100cpi, 1.441,65 €
*Edelstahl-Vorschalldämpfer, ohne TÜV, 2x60mm Rohrführung, 639,50 €
*Edelstahl-Endschalldämpfer, ohne TÜV, 2 x 76mm, 426,33 €
3. Audi S4/S6/S6+ Type C4
*Stainless-Cat-Exchange-pipes. Only for Turbo! 2 x 60mm pipe dia. 168,20 €
*Stainless steel pipes from Cat to Frontsilencer (Turbo) 2 x 60mm pipe dia. 139,20 €
*Stainless steel Frontsilencer, 2 x 60mm pipe dia. 383,50 €
*Stainless steel Rearsilencer, 2 x 70/20°, 622,90 €
*Stainless steel Cat-back system
Milltek pakub järgmist:
1. Audi S2 Coupe 20v Turbo 5 Speed
*LARGE BORE DOWNPIPE AND HI-FLOW SPORTS CAT [Pipe Diameter: 69.85mm (2.75")]
*CAT-BACK [Pipe Diameter: 63.50mm (2.50"), Rear Silencer Meteor Twin 76.2mm]
2. Audi S2 Coupe 20v Turbo 6 Speed
*LARGE BORE DOWNPIPE AND HI-FLOW SPORTS CAT [Pipe Diameter: 69.85mm (2.75")]
*CAT-BACK [Pipe Diameter: 63.50mm (2.50"), Rear Silencer Meteor Twin 76.2mm]
3. Audi S2 Avant Turbo 6 Speed Avant
*LARGE BORE DOWNPIPE AND HI-FLOW SPORTS CAT [Pipe Diameter: 69.85mm (2.75")]
*CAT-BACK [Pipe Diameter: 76.20mm (3.00"), Rear Silencer Jet Twin 76.2mm]
4. Audi RS2 Turbo 6-speed Avant
*LARGE BORE DOWNPIPE AND HI-FLOW SPORTS CAT [Pipe Diameter: 69.85mm (2.75")]
*CAT REPLACEMENT PIPE [Pipe Diameter: 69.85mm (2.75")]
*CAT-BACK [Pipe Diameter: 76.20mm (3.00"), Rear Silencer Jet Twin 76.2mm]
Tagumiste püttide märksõnad "Jet ja Meteor" tähendab püti ehitust ja "Twin" tähendab, et on 2 summutaja otsatoru (need on siin kõigil 3").
Tobiase lehel on mõni pilt RS2-le mõeldud 3" cat-back süsteemist.
UrS4 omanikele ma soovitaksin sellist lahendust, et asendaksid katid ja eelviimase püti torudega. Kuna seal on all 2 toru, siis ühte kokku viimine on
suurem ettevõtmine. Torudega asendamine on märksa lihtsam ettevõtmine. Igatahes prostam, kui 3" ehitada. K24 puhul vaevalt seal mingit vahet ka
on.
Lisan paar linki:
1. Ise mõõtsin väljalaske S4-al üle;
2. Total Audi Perfomance-i poolt pakutav
väljalase UrS4-le.
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torque addict / in the real world four wheel drive means safety and traction
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MaQQu
klubiliige
Registreerunud 15.12.02
Asukoht: Tallinn
Kasutaja on eemal
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postitati 27.01.06 12:04
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exhaust system
ei ole kuulnud, et keegi vastupidist väidaks kuskil (samas pole asja ka väga sügavuti uurinud, seega ei pretendeeri täielikule tõele.). Ainus, mida
südamele pannakse summutit ehitades on see, et ei soovitata toru painutada, vaid kasutada valmis põlvesi, sest painutades läheb toru lapikuks ja
läbilaskevõime kannatab.
Kodanik "mulk" andis kunagi ka lingi, kus oli enamvähem rusikareegli järgi võetud tabel, kui jäme toru kui võimsale turbomootorile sobima peaks.
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Maku
klubiliige
Registreerunud 28.01.03
Asukoht: Eesti Vabariik
Kasutaja on eemal
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postitati 27.01.06 13:04
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exhaust system
| Tsitaat: | Algselt postitas: ivo196
seda tahaks teada, mida arvatakse kui kaks toru vedada 2,5" |
Sinu auto puhul on üks kitsas koht kindlasti väljalaske kollektor. Mina
pööraksin sellele rohkem tähelepanu kui praeguse 3" ümber ehitamisele. Vastates sinu küsimusele, siis vist nii kipub olema jap, et 2x2,5" lõpuni on
hea variant.
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torque addict / in the real world four wheel drive means safety and traction
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mulk
klubiliige ac aasta auto 2007/2009 võitja
Registreerunud 11.11.03
Asukoht: Nummela/Viljandi
Kasutaja on eemal
Auto: A8 D3 FL2, LR Disco 1, Iveco Daily 40C13V
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postitati 27.01.06 19:43
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exhaust system
| Tsitaat: | Algselt postitas: MaQQu
lihtne arvutus näitab, et 2 x 2,5" kogupindala on suurem kui 1 x 3" seega hingamine vabam. Kuivõrd seda vaja on, oleneb konkreetselt masinast,
mootorist.
Vastusurvetest ja muudest faktoritest tahaks isegi targemaks saada.
edit:
tegin siis need lihtsad arvutused.
1x2" toru = 4051mm2
1x2,5" toru = 6330mm2
2x2" toru = 8103mm2
1x3" toru = 9116mm2
2x2,5 toru = 12660mm2 |
Võrdlus 2X2.5" ja 3" vahel ehk pisut ebaõiglane, 2X2,5" peaks minema juba samasse klassi 4" singel toruga.
Samuti väga palju voolavust mõjutav tegur on toru seina pindala, mis kahe toru puhul tuleb suurem, kui ühe puhul.
Mis oleks minu meelest eeliseks ühe toru puhul:
1. väiksem kaal
2. väiksem toru omahind, kui ka ehitamisel väiksemast töömahust tingitud madalam töö hind
Vastusurvet kui sellist turbomootoriga auto ei vaja, mida vabamalt gaasid peale turbot liikuda saavad, seda parem, piiravaks on pigem sellega kaasnev
müra.Samas on väga lihtne custom summutit ehitades (isegi 3" ga) muuta voolavus teatud reziimil palju halvemaks kui originaal summuti puhul.
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MaQQu
klubiliige
Registreerunud 15.12.02
Asukoht: Tallinn
Kasutaja on eemal
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postitati 27.01.06 20:40
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exhaust system
| Tsitaat: | Algselt postitas: mulk
Võrdlus 2X2.5" ja 3" vahel ehk pisut ebaõiglane, 2X2,5" peaks minema juba samasse klassi 4" singel toruga.
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seda küll, vastasin lihtsalt "Maku" küsimusele, kus ta küsis just sellist võrdlust.
Aga tahaks teada, mismoodi on saadud 3" toru installeerimisega halvem tulemus kui stockis, mis valesti tehtud on?
Olen kuulud, et essi summuteid tehti ka erinevas mõõdus (2x55mm vs 2x60mm vms ???) On see nii, ja mis need täpsed mõõdud on?
| Tsitaat: | Algselt postitas: Maku
Turboga autode puhul kehtib minu teada idee, et mida kaugemal asetseb vastusurve turbost, seda parem |
Kas ei ole nii, et mida väiksem vastusurve, seda parem?
Ja kuna vastusurve peab olema (mingisugune mürasummutus peab ju olema) siis on ilmselt parem, kui see asub turbost võimalikult kaugemal, et mitte
segada turbo tööd.
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Maku
klubiliige
Registreerunud 28.01.03
Asukoht: Eesti Vabariik
Kasutaja on eemal
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postitati 27.01.06 21:00
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exhaust system
Vastasid ise oma küsimusele, MaQQu.
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torque addict / in the real world four wheel drive means safety and traction
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mulk
klubiliige ac aasta auto 2007/2009 võitja
Registreerunud 11.11.03
Asukoht: Nummela/Viljandi
Kasutaja on eemal
Auto: A8 D3 FL2, LR Disco 1, Iveco Daily 40C13V
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postitati 28.01.06 11:52
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exhaust system
Et asja võimalikult odavalt teha, loobutakse põlvedest ja saetakse toru soovitud nurga alla. Sellisel juhul on see "käänak" kahest risti asetsevast
punktist mõõdetuna erineva läbimõõduga. See on üks turbulentsi tekitajatest.
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Maku
klubiliige
Registreerunud 28.01.03
Asukoht: Eesti Vabariik
Kasutaja on eemal
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postitati 05.03.06 21:15
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exhaust system
Täna mõõtsin S2 coupe väljalaske (Hannese sinise oma) üle ja seis selline:
1. downpipe ~70MM;
2. katalüsaatorite asendustorud 2 x ~54MM;
3. peale katalüsaatorite asendustorusid 2 x ~64MM;
4. enne eelviimast pütti üheks toruks kokku 1 x ~70MM;
5. eelviimase püti pikkus ~300MM;
6. eelviimase püti ja viimase püti vahel 1 x ~70 MM;
7. viimase püti pikkus ~450MM;
8. summutaja otsatorud 2 x ~70MM.
Ma ei oska kommenteerida, miks katalüsaatorite asendustorud on ~54MM. Mõistlikum oleks vast, kui nad ka ~64MM oleksid. Mis puudutab väljalaset ennast,
siis paremat väljalaset ma S2 coupele soovitada ei oska. Sõitsin üks päev autoga, kus oli 60MM toru lõpuni ja üks pütt taga. See tegi kordades rohkem
häält ja oli jube häiriv kogemus. Antud coupe väljalase on väidetavalt SKN meeste kätetöö ja ma usun, et nad teadsid, mida tegid. Käiku vahetades
teinekord isegi paugub, aga sõites on väga bro. Vaikne sõites ja kiirendades. Täpselt selline iseloomustus, et "annab sõitjale aimu, et on
sportväljalase, aga pole häiriv".
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torque addict / in the real world four wheel drive means safety and traction
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genekas
huviline
Registreerunud 30.01.03
Asukoht: Tallinn
Kasutaja on eemal
Auto: järgmist plaanimas
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postitati 06.03.06 00:39
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exhaust system
siin lappas ringi mööda "pildialbumit" ja tekkis tunne, et 3B ja ABY mootorite väljalasked on kupeel erisugused, sest nii keskmine kui tagumine pütt
on erinevad (kui mälu ei peta, siis auto all koperdades paistis, et kattide tagant jooksid 2 toru omaette kuni keskmise pütini välja)...
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Silwer
huviline
Registreerunud 11.12.02
Kasutaja on eemal
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postitati 09.03.06 10:14
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exhaust system
Natuke ka OT:
Turbo autodel ei ole see väljalase nii kriitilise tähtsusega kui vabalthingaval.
Vabalthingava summuti kõige tähtsam osa on see kus lõpuks kõikide silindrite väljalaske gaasid lähevad kokku. See üleminek peab olemavõimalikult
sujuv. Kohe peale üleminekut kasutatakse 1-15cm tavaliselt kitsamat toru et saavutada peale gaaside kokkuminekut selles toru osas gaaside kiirendus ja
parem liikumine. Peale seda läheb toru jälle laiemaks tagasi.
Üks näide ka E30 M3 group A summutist:
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BMW 325i E30 2,8 stroker & BMW 328iT E36 & Seat Altea XL 2,0 TDI+DSG
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Maku
klubiliige
Registreerunud 28.01.03
Asukoht: Eesti Vabariik
Kasutaja on eemal
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postitati 06.04.06 10:48
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Natuke lugemist väljalaskest
Exhaust Turbo Performance.
- The maximum exhaust energy should be transferred to the turbine.
Energy expended overcoming flow restrictions means less energy to spin the turbine. Because of this every effort must be made to transfer the max
exhaust energy to the turbo, over a wide band of engine operating conditions. Any efficiency decrease here will increase turbo lag.
The Exhaust Manifold.
- Maximise flow by ensuring internal surfaces are smooth, incl gaskets.
- Machine away slag and extrude hone hard to reach areas. First make sure the internal surfaces are nice and smooth. This encourages flow and
discourages carbon buildup. Casting slag should be removed as should any sharp edges or joins. The manifold should match the exhaust ports and the
manifold gasget should be trimmed back as much as possible. The manifold to turbo joint should also be kept smooth. But be careful not to overly
increase the internal size of the runners, because this will result in lower velocity exhaust gas hitting the turbine.
Tube Manifolds.
- Tuned length pipes can be used to maximise exhaust gas scavenging.
- Steam piping is strong but heavy.
- Stainless steel is strong and light, but turbos will need additional bracing.
For the ultimate in exhaust manifolds we have to ditch the cast manifold and fabricate a multi branch manifold using tuned length pipes.
For heavy turbos, a support system must be employed to carry the turbo.
Manifold Dimensions.
- Choose the minimum pipe size that will give the flow needed.
Anything that adds weight, complexity should be avoided. The diameter of the piping will be dictated by the size of the engine and whether you want
top end power or low and mid range power. Its always best to choose a diameter as small as possible to keep exhaust velocities high and therefore,
keep spool-up times low and responsiveness high. Only when all out top end power is important should bigger diameter pipes be used.
Exhaust Pipe Size.
- Bigger diameter bores are not always better.
Because of the big weights of big diameter exhausts and big diameter silencers, bore sizes should be kept as small as possible while still allowing
maximum flow.
A good guide, based on the experience of tuners is as follows:
1300-1600cc – 2.25 to 2.5in
2000-2300cc – 2.75 to 3.0in
2500-3000cc – 3.5 or 2x2.5in
3500-4000cc – 4.0 or 2x2.75in
5000-5700cc – 2x3.0in
These figures are based on engines developing 120-150bhp per litre.
Rally engines developing 200-250bhp per liter need pipes that are 0.5 to 1.0in bigger.
The tailpipe can be reduced by 1/4in without suffering penalty.
But testing is the only way to go. On group A two litre turbo engines, a 3in pipe will give excellent power but a pipe 3.5in will cause a power drop
and at 4in the power comes back. So testing is the only reliable method for choosing max power setups.
With turbos, the biggest flow restriction is at the turbine wheel and housing. The use of a bigger housing, without suffering further turbo lag will
give better gains than exhaust change. Then next most restrictive area is at the manifold between the turbo and the head, so improvements here will
also give good gains.
Tailpipe Design.
-Can use a tailpipe or use CATs, baffles and silencers.
After the header, we have to consider the rest of the exhaust system. On all out competition cars this can mean just a tail pipe. On road cars to
usually means a cat and one or more silencers. Less tailpipe length will increase top end power and longer tail pipes will yield more low and mid
range power.
This is why some engines will have a tailpipe not much longer than the collector. However, most tailpipes go right to the back of the car.
Tailpipe diameter is determined on the dyno and if a cat is used the diameter after the cat needs to be larger.
A guide to blown and nitrous engines is:
80 to 120bhp – 1.875in
110 to 140bhp – 2in
130 to 150bhp – 2.125in
140 to 185bhp – 2.25in
180 to 220bhp – 2.5in
210 to 265bhp – 2.75in
250 to 320bhp – 3.0in
280 to 360bhp – 3.5in
400 to 500bhp – 4.0in
480 to 630bhp – 4.5in
580 to 750bhp – 5in
As always the entire system must have a minimum of bending and adequate bore size. When ground clearance is a problem then oval exhaust bores
can be used with no penalty in flow. You can reduce the diameter by ¼ in at the end (beyond the real wheels) without incurring any flow
restrictions.
Silencer Design.
- Straight through or reverse flow silencers are best.
A well designed silencer, placed to the rear of the car won’t drop power by anymore that 3-5%. The closer to the engine they are fitted, the
more flow restricting occurs and the more power is lost.
Straight through or reverse flow silencers are the best for power applications. Straight through provides the best sound deadening and are good for
turbo cars. However, on NA cars two silencers or a silencer and a resonator must be used to stop popping occurring on overrun. The quietest silencers
have an open resonating chamber in the middle.
Reverse flow silencers are different and don’t contain any sound deadening materials. This makes them lighter, but poorly designed ones are loud and
cause power loss. The main advantage is that they are good at suppressing popping when you lift off the throttle.
CAT Problems.
- Don’t use CATs if possible.
- Otherwise use performance CATs with twice the flow of regular CATs.
CATS that melt due to excessive temperatures caused by combustion in the exhaust will cause a problem by blocking the exhaust flow.
However, even healthy CATs can cause problems. A poorly designed CAT can impede exhaust flow due to turbulence caused by the gas having to enter the
honeycomb at 30deg angles or more and having to exit the honeycomb at the same angle. To overcome this a performance cat must have a gentle entry and
exit taper of about 10deg. A performance cat will have double the flow rate of a regular cat.
Pumping Losses.
- This refers to the power consumed in pumping the exhaust gas out of the engine.
Power is consumed because exhaust gases have to be pumped out of the engine. As soon as the crank rotates past BDC, the piston starts its way up the
cylinder barrel on the exhaust stroke. During the exhaust stroke it must ram the exhaust gas out past the exhaust valve and through the exhaust
system. This consumes power provided by another cylinder on its power stroke. This means that there is less power available at the flywheel.
There are methods available to cut these pumping losses to a minimum. One way is to open the exhaust valve very early. This provides a net gain in the
upper half of the powerband but causes poor fuel economy at cruise.
A better and more considered route is to ensure that the entire exhaust flow route is free of obstacles and incorporates any elements that promote
positive flow.
Exhaust Pressure Waves.
- The cylinder outlets should be mated to maximise wave resonance tuning.
As mentioned above, wave resonance tuning is the primary means of increasing flow. This means connecting cylinders in a particular order using
exhaust tubing of a specific length to take advantage of exhaust pressure waves to pull exhaust gas out of the cylinders and during valve overlap,
suck fresh air/fuel into the cylinders. When we look at the firing order of the engine, we join cylinders so that exhaust gas from one cylinder won’t
cancel the pressure wave from another cylinder.
EDIT1: Lihtne arvutus näitab, et kui kubatuur on 2,2l ja kuni tailpipe-ni (mis võiks olla ka 1/4 väiksem, ehk siis 2,1825") on
2,91" läbimõõduga väljalase, siis vastab see 308 hobujõule.
EDIT2: Mulgiga kahepeale sõnastasime ka asja iva, miks lõpust võib summutaja toru läbimõõt olla oluliselt väiksem kui eest otsast.
Asi on nimelt selles, et kui õhk on kuum, siis molekulid on paisunud ja neid mahub X ruumalasse vähe. Kui aga õhk on jahe, siis mahub X ruumalasse
rohkem molekule. Kui heitgaasid väljuvad mootorist turbiini labade peale ja sealt edasi downpipe-i, siis on heitgaasid loomulikult kuumad ja tahavad
suurt ruumala. Mida summutaja süsteemi lõpu poole, seda jahtunumad heitgaasis molekulid on ja ei ole enam mõtet sama suure lõbimõõduda torul nagu seda
oli downpipe.
Sama süsteem on sisselaskega. Mida jahedam õhk silindritesse lõpuks jõuab, seda rohkem on X ruumalas molekule ja seda suurem on efektiivsus.
EDIT3: UrS4 downpipe toru lõbimõõt on ca 2,5" ja tema ressurss oleks arvutuste kohaselt ca 265 hobujõudu (264,55). Downpipe-st edasi
lähevad 2 x 55mm torud ja ma ei oska öelda, kas kahe toru korral tehakse arvutusi 1+1 meetodil.
EDIT4: Rallikale ja sõidukale tulevad erinevad koefitsendid. Võtsin kahe koefitsendi keskmise ja siis sain, et 2,5" võrdub 303,27
hobujõuga (rallika koefitsendiga 345,4) ja 3" võrdub 363,9 hobujõuga. Asi on selles, et rallika ja sõiduka koefitsendid on suure erinevusega. Näiteks
rallika koefitsendiga tuleks 3,75" 513 hobujõudu ja sõiduka koefitsendiga 396,8 hobujõudu. Eks siin mängib paljuski rolli, mida veel modifitseeritud
on.
Kui vaadata, milliste hobujõu numbrite juures on Dahlbäck summutajat vahetanud, siis tuleks igatahes ennem rallika koefitsenti uskuda (isegi sellest
jääb Dahlbäcki puhul väheks). Kokkuvõtlikult siis nii palju, et rallika koefitsendi puhul tulevad järgmised numbrid:
1. 2,5" = 341,99 HP;
2. 2,75" = 375 HP;
3. 3,0" = 410 HP;
4. 3,75" = 513 HP.
Nende arvutuste kohaselt peavad Hannese kunagise sinise S2 downpipe-i andmed täiesti paika. Autol oli oletatavasti 280kw ja downpipe 2,75". Arvutuste
kohaselt 2,75" võrdub 276kw-ga.
EDIT: Reverse flow: airflow in the silencer is in the opposite direction to the noise propagation.
A tri-flow (reverse flow or "turbo") muffler takes the exhaust gas on an S-shaped path through the muffler. The exhaust gas travels to one end of
the muffler, is turned through 180 degrees and heads back to the first end. There, it is again turned through 180 degrees before it passes to the
outlet. Tri-flow mufflers normally have three internal chambers.
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torque addict / in the real world four wheel drive means safety and traction
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Maku
klubiliige
Registreerunud 28.01.03
Asukoht: Eesti Vabariik
Kasutaja on eemal
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postitati 06.04.06 15:30
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Kaaperdaja juhtis minu tähelepanu ühele S2 foorumi teemale. Tegemist on Marco nimelisega härraga, kes ise keevitas kokku 3" downpipe-i ja ka tegi
mõned müügiks.
Showed in previous picture is last pipe I've built, which was asked to be without WG merging.
I use the showed die grinder and tools to smooth out and polish joints and mergings. Consider a good cutter (in the range of 15-20 euros) will be good
for only one pipe: SS is very tough to cut and there is a lot of work to be done in the turbo flange-to-cone area and WG-to-downpipe merging.
The cone is about 50-55mm long and its function is to increase duct section from 58mm (turbine outlet) to the 66-72 mm final size fast enaugh, without
causing significant turbulences.
WG pipe is Ø 42mm ID.
I usually start the building from the turbo flange. Before welding the piece (whether it is a straight or a curved piece) I smooth and deburr each
side of it, then weld it, cut and polish internal joints before adding following piece.
I don't have a TIG welder therefore using an inverter type electrode welding machine. I use high quality #308 SS electrodes (there are cheaper ones,
but high quality electrodes make welding much easier).
I'm not a professional welder, and I'm aware my welds don't look that good, but they are strong and reliable, apart from the fact I put much more
effort on the internal smoothness than the outside look.
Some numbers:
in my ~370 Hp RS2 setup the full 3" turbo back system with racing cat converter made me gain 20 hp at peak hp rpm, with gains over OEM system
starting from 3500 rpm on. Turbine spool up time seemed improved to me as well, while off boost low rpm pick up worstened a little.... as it's
supposed to .
IMHO good ID exhaust sizes for various engine outputs could be:
- Ø 62mm up to 310 hp;
- Ø 66mm up to 360 hp;
- Ø 72mm up to 430 hp;
- Ø 76mm up to 480 hp;
- Ø 85mm up to 600 hp;
- Ø 95mm up to 800 hp;
PS: Pange tähele, et härra ütleb "could be". See ei ole sama, mis "are, should be, must be.."!
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torque addict / in the real world four wheel drive means safety and traction
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Maku
klubiliige
Registreerunud 28.01.03
Asukoht: Eesti Vabariik
Kasutaja on eemal
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postitati 01.05.06 11:55
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SJM copy/paste
Exhaust System Issues
You should have the exhaust back pressure checked by a muffler shop if you have low boost conditions and suspect a plugged catalytic converter or
muffler/exhaust system. They can use the pre-catalytic converter sniffer pipe bolted to the intake manifold to do this, or they can drill a small hole
in the exhaust pipe to insert the pressure gauge pipe.
A low pressure (0-10 psi) fuel pump pressure gauge can be used for this. Typically with the car idling in neutral, as you slowly rev the engine to
4000 RPM and hold it at 4000 RPM, the exhaust back pressure should not increase above 1-2 psi. If you run a long hose from the sniffer pipe to a gauge
inside the car, an assistant can check the exhaust back pressure while you drive the car.
Test Example: When the car is driven and under load in 3rd gear at WOT and near redline, it is not unusual to see over 4-7psi of back pressure when
running 1.8 bar of boost pressure. The older catalytic converters can create some of this back pressure and may need to be replaced as the car gets
over 75K miles.
The RS2 type exhaust manifold is recommended for improving the exhaust flow out of the head and rumor has it, to prevent burned exhaust valves
when more extensive ECU and Turbocharger mods are performed. As mentioned, the catalytic converter and muffler system can get plugged or
restricted over the life of a car which may cause poor running with low power.
Catalytic Converter meltdown can occur if extremely rich mixture levels occur in the combustion chamber which are not thoroughly burned which allows
high levels of raw gasoline (Hydrocarbons) to pass into the catalytic converter. If this occurs under engine load conditions and is followed by normal
lean running or idling the catalytic converter will get very hot and damage may occur. Ignition misfires can also dump raw fuel or hydrocarbons (HC)
into the catalytic converter and this will also cause meltdown of the ceramic honeycomb material if the engine is driven under load.
If you ever need a reminder to let your engine run after a high boost run, just open up your hood at night and see the red hot exhaust manifold and
turbo! Even with the water cooled turbo you should let the car idle for several minutes.
It may take 10-15 minutes of normal low boost driving before the exhaust manifold/turbo cool down. It is a good idea to avoid high boost
initially after starting a cold engine until the oil temp gets up to 60C (this is recommended in the factory operators manual).
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torque addict / in the real world four wheel drive means safety and traction
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epic
klubiliige
Registreerunud 26.05.05
Asukoht: Viimsi
Kasutaja on eemal
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postitati 16.06.06 23:27
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küsimus
Ehk siis mida arvate sellest asjast ? Kas siiani tundmatu ?
LINK
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mulk
klubiliige ac aasta auto 2007/2009 võitja
Registreerunud 11.11.03
Asukoht: Nummela/Viljandi
Kasutaja on eemal
Auto: A8 D3 FL2, LR Disco 1, Iveco Daily 40C13V
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jõuvanker
klubiliige
Registreerunud 21.03.03
Asukoht: Harjumaa
Kasutaja on eemal
Auto: ´11a. A4 avant q. s-tronic 3.0TDI 176KW
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postitati 28.07.06 14:23
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Midagi väga voolujoonelist:
Tuleb toime isegi 900HJ´ga ning seda probleemivabalt, vähemalt gaasidevoolavus kohapealt.
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lapsepõlvest alates meeldinud 20VT R5
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oleeev
huviline
Registreerunud 23.05.03
Asukoht: pärnu
Kasutaja on eemal
Auto: 2x audi S4tq,VW passat2,8 syncro
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postitati 29.07.06 08:56
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Sai siis ka valmis esimene omatehtud 20v kolle,hetkel veel turboka flants installimatta.
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Maku
klubiliige
Registreerunud 28.01.03
Asukoht: Eesti Vabariik
Kasutaja on eemal
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postitati 13.08.06 20:28
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Jay Kavanaugh, a turbosystems engineer at Garret, responding to a thread on www.impreza.net regarding exhaust design and exhaust theory:
“This thread was brought to my attention by a friend of mine in hopes of shedding some light on the issue of exhaust size selection for turbocharged
vehicles. Most of the facts have been covered already. FWIW I’m an turbocharger development engineer for Garrett Engine Boosting Systems.
N/A cars: As most of you know, the design of turbo exhaust systems runs counter to exhaust design for n/a vehicles. N/A cars utilize exhaust velocity
(not backpressure) in the collector to aid in scavenging other cylinders during the blowdown process. It just so happens that to get the appropriate
velocity, you have to squeeze down the diameter of the discharge of the collector (aka the exhaust), which also induces backpressure. The backpressure
is an undesirable byproduct of the desire to have a certain degree of exhaust velocity. Go too big, and you lose velocity and its associated
beneficial scavenging effect. Too small and the backpressure skyrockets, more than offsetting any gain made by scavenging. There is a happy medium
here.
For turbo cars, you throw all that out the window. You want the exhaust velocity to be high upstream of the turbine (i.e. in the header).
You’ll notice that primaries of turbo headers are smaller diameter than those of an n/a car of two-thirds the horsepower. The idea is to get
the exhaust velocity up quickly, to get the turbo spooling as early as possible. Here, getting the boost up early is a much more effective
way to torque than playing with tuned primary lengths and scavenging. The scavenging effects are small compared to what you’d get if you just got
boost sooner instead. You have a turbo; you want boost. Just don’t go so small on the header’s primary diameter that you choke off the high end.
Downstream of the turbine (aka the turboback exhaust), you want the least backpressure possible. No ifs, ands, or buts. Stick a Hoover on the tailpipe
if you can. The general rule of “larger is better” (to the point of diminishing returns) of turboback exhausts is valid. Here, the idea is to minimize
the pressure downstream of the turbine in order to make the most effective use of the pressure that is being generated upstream of the turbine.
Remember, a turbine operates via a pressure ratio. For a given turbine inlet pressure, you will get the highest pressure ratio across the turbine when
you have the lowest possible discharge pressure. This means the turbine is able to do the most amount of work possible (i.e. drive the compressor and
make boost) with the available inlet pressure.
Again, less pressure downstream of the turbine is goodness. This approach minimizes the time-to-boost (maximizes boost response) and will improve
engine VE throughout the rev range.
As for 2.5" vs. 3.0", the “best” turboback exhaust depends on the amount of flow, or horsepower. At 250 hp, 2.5" is fine. Going to 3" at this
power level won’t get you much, if anything, other than a louder exhaust note. 300 hp and you’re definitely suboptimal with 2.5". For 400-450 hp,
even 3" is on the small side.”
“As for the geometry of the exhaust at the turbine discharge, the most optimal configuration would be a gradual increase in diameter from the
turbine’s exducer to the desired exhaust diameter– via a straight conical diffuser of 7-12° included angle (to minimize flow separation and skin
friction losses) mounted right at the turbine discharge. Many turbochargers found in diesels have this diffuser section cast right into the turbine
housing. A hyperbolic increase in diameter (like a trumpet snorkus) is theoretically ideal but I’ve never seen one in use (and doubt it would be
measurably superior to a straight diffuser). The wastegate flow would be via a completely divorced (separated from the main turbine discharge flow)
dumptube. Due the realities of packaging, cost, and emissions compliance this config is rarely possible on street cars. You will, however, see this
type of layout on dedicated race vehicles.
A large “bellmouth” config which combines the turbine discharge and wastegate flow (without a divider between the two) is certainly better than the
compromised stock routing, but not as effective as the above. If an integrated exhaust (non-divorced wastegate flow) is required, keep the wastegate
flow separate from the main turbine discharge flow for ~12-18" before reintroducing it. This will minimize the impact on turbine efficiency– the
introduction of the wastegate flow disrupts the flow field of the main turbine discharge flow.
Necking the exhaust down to a suboptimal diameter is never a good idea, but if it is necessary, doing it further downstream is better than doing it
close to the turbine discharge since it will minimize the exhaust’s contribution to backpressure. Better yet: don’t neck down the exhaust at all.
Also, the temperature of the exhaust coming out of a cat is higher than the inlet temperature, due to the exothermic oxidation of unburned
hydrocarbons in the cat. So the total heat loss (and density increase) of the gases as it travels down the exhaust is not as prominent as it seems.
Another thing to keep in mind is that cylinder scavenging takes place where the flows from separate cylinders merge (i.e. in the collector). There is
no such thing as cylinder scavenging downstream of the turbine, and hence, no reason to desire high exhaust velocity here. You will only introduce
unwanted backpressure.
Other things you can do (in addition to choosing an appropriate diameter) to minimize exhaust backpressure in a turboback exhaust are: avoid
crush-bent tubes (use mandrel bends); avoid tight-radius turns (keep it as straight as possible); avoid step changes in diameter; avoid “cheated”
radii (cuts that are non-perpendicular); use a high flow cat; use a straight-thru perforated core muffler… etc.”
“Comparing the two bellmouth designs, I’ve never seen either one so I can only speculate. But based on your description, and assuming neither of them
have a divider wall/tongue between the turbine discharge and wg dump, I’d venture that you’d be hard pressed to measure a difference between the two.
The more gradual taper intuitively appears more desirable, but it’s likely that it’s beyond the point of diminishing returns. Either one sounds like
it will improve the wastegate’s discharge coefficient over the stock config, which will constitute the single biggest difference. This will allow more
control over boost creep. Neither is as optimal as the divorced wastegate flow arrangement, however.
There’s more to it, though– if a larger bellmouth is excessively large right at the turbine discharge (a large step diameter increase), there will be
an unrecoverable dump loss that will contribute to backpressure. This is why a gradual increase in diameter, like the conical diffuser mentioned
earlier, is desirable at the turbine discharge.
As for primary lengths on turbo headers, it is advantageous to use equal-length primaries to time the arrival of the pulses at the turbine equally and
to keep cylinder reversion balanced across all cylinders. This will improve boost response and the engine’s VE. Equal-length is often difficult to
achieve due to tight packaging, fabrication difficulty, and the desire to have runners of the shortest possible length.”
“Here’s a worked example (simplified) of how larger exhausts help turbo cars:
Say you have a turbo operating at a turbine pressure ratio (aka expansion ratio) of 1.8:1. You have a small turboback exhaust that contributes, say,
10 psig backpressure at the turbine discharge at redline. The total backpressure seen by the engine (upstream of the turbine) in this case is:
(14.5 +10)*1.8 = 44.1 psia = 29.6 psig total backpressure
So here, the turbine contributed 19.6 psig of backpressure to the total.
Now you slap on a proper low-backpressure, big turboback exhaust. Same turbo, same boost, etc. You measure 3 psig backpressure at the turbine
discharge. In this case the engine sees just 17 psig total backpressure! And the turbine’s contribution to the total backpressure is reduced to 14
psig (note: this is 5.6 psig lower than its contribution in the “small turboback” case).
So in the end, the engine saw a reduction in backpressure of 12.6 psig when you swapped turbobacks in this example. This reduction in backpressure is
where all the engine’s VE gains come from.
This is why larger exhausts make such big gains on nearly all stock turbo cars– the turbine compounds the downstream backpressure via its expansion
ratio. This is also why bigger turbos make more power at a given boost level– they improve engine VE by operating at lower turbine expansion ratios
for a given boost level.
As you can see, the backpressure penalty of running a too-small exhaust (like 2.5″ for 350 hp) will vary depending on the match. At a given
power level, a smaller turbo will generally be operating at a higher turbine pressure ratio and so will actually make the engine more sensitive to the
backpressure downstream of the turbine than a larger turbine/turbo would. As for output temperatures, I’m not sure I understand the question. Are you
referring to compressor outlet temperatures?
The advantage to the bellmouth setup from the wg’s perspective is that it allows a less torturous path for the bypassed gases to escape. This makes it
more effective in bypassing gases for a given pressure differential and wg valve position. Think of it as improving the VE of the wastegate. If you
have a very compromised wg discharge routing, under some conditions the wg may not be able bypass enough flow to control boost, even when wide open.
So the gases go through the turbine instead of the wg, and boost creeps up.
The downside to a bellmouth is that the wg flow still dumps right into the turbine discharge. A divider wall would be beneficial here. And, as
mentioned earlier, if you go too big on the bellmouth and the turbine discharge flow sees a rapid area change (regardless of whether the wg flow is
being introduced there or not), you will incur a backpressure penalty right at the site of the step. This is why you want gradual area changes in your
exhaust.”
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torque addict / in the real world four wheel drive means safety and traction
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Maku
klubiliige
Registreerunud 28.01.03
Asukoht: Eesti Vabariik
Kasutaja on eemal
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