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exhaust design effect on turbo performance
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63Fiberbuggy
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Joined: January 15, 2007
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PostPosted: Tue Nov 25, 2014 7:51 am    Post subject: exhaust design effect on turbo performance Reply with quote

I recently replaced dual carbs w/Garrett T3 turbo fed w/Weber DCOE-45; and unit came with exhaust system (J-tubes, collector/header, flange to turbine housing). Still working thru tuning process; however, in reading from Garrett website, a question came to mind regarding effect of "unequal" length exhaust runs leading to the collector. Per Garrett, to optimize turbo performance, following is recommended:

- make the exhaust primaries equal length to balance exhaust reversion across all cylinders; and to maintain pulse energy to the turbine; for best power, tuned primary lengths can be used

In measuring mine, lengths vary significantly due to exhaust design; and I browsed photos of samba member's turbo applications, taking note that many appear to be "unequal" as well. So, questions are: how much effect have folks noticed with unequal lengths; any lag/lurch? Any recommendations for suppliers that offer tuned exhaust kits?

Thanks for support getting the most out of my turbo upgrade.
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miniman82
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PostPosted: Tue Nov 25, 2014 9:45 am    Post subject: Reply with quote

No effect whatsoever on the street, mine even sounds like an inline 4. It's mainly race appllications that play with pulse headers/split turbine housings, which does make a big difference.
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Eaallred
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PostPosted: Tue Nov 25, 2014 11:54 am    Post subject: Reply with quote

I heard it makes very little difference. That said, I just switched to an equal length header to feed my turbo, but I've made other changes as well so i'll have no idea if it makes a difference or not.
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modok
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PostPosted: Tue Nov 25, 2014 1:04 pm    Post subject: Reply with quote

It is better to make the tubes as short as possible, and only as large as needed. If you have to lengthen them to make it equal then........... don't.
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fastfil
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PostPosted: Tue Nov 25, 2014 1:07 pm    Post subject: Reply with quote

Unequal length exhaust should give faster spool up but the turbine will choke earlier.
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clonebug
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PostPosted: Tue Nov 25, 2014 8:59 pm    Post subject: Reply with quote

I use a cheap-ass sedan header and homemade up pipe to my turbo and have no troubles with spool.
Could it be better???? Maybe......but I have less than $100.00 into the header and it has worked fine for 4 years now.

Boost comes in at 2500 rpm and I have 15 lbs by 3500 rpm.

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63Fiberbuggy
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PostPosted: Thu Nov 27, 2014 3:57 pm    Post subject: Reply with quote

Thanks for advice guys! I'm gonna stick with what I've got for now. Other mods at time of switch to turbo included: bore & stoke up from 1776 to 2180, counter-weighted crank, FK8 cam, SuperFlo heads w/1.4:1 rockers & dual springs...so, I'm feeling plenty under pedal, just curious if benefit there to tune exhaust.
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