stepping down with exhaust sizing
Joined: May 2005
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From: Tallahassee, FL
Can you hear the wastegate opening? Can you tell if that is the source of the leak? There has to be a boost leak somewhere... makes sense with the symptoms. Higher the boost, the quicker it falls. It will probably appear tight, but will "leak" at higher PSI levels. Try spraying your connections with a highly misted water (from spray bottle). That should show you your leak. It will probably only be evident at higher boost levels.
I am having a similar issue now (cant build past 5.5psi), but my car was in a bit of a fender bender (driver's side fender screwed and front bumper torn off the car). The IC pipes all looked to still be in good condition, but I believe one got yanked a bit in the accident. I get the car back tomorrow (hopefully) from the body shop. This is the first thing I am doing. I will post my results.
Can you hear the wastegate leaking at all (I realize its internally gated, and I know that is a bit quieter than my external Tial) during the pulls?
FWIW, I believe a Dyno Dynamics reads somewhere between 7-10% low when compared to a DynoJet. Its known as the "heartbreaker" over at Stage6.
John
I am having a similar issue now (cant build past 5.5psi), but my car was in a bit of a fender bender (driver's side fender screwed and front bumper torn off the car). The IC pipes all looked to still be in good condition, but I believe one got yanked a bit in the accident. I get the car back tomorrow (hopefully) from the body shop. This is the first thing I am doing. I will post my results.
Can you hear the wastegate leaking at all (I realize its internally gated, and I know that is a bit quieter than my external Tial) during the pulls?
FWIW, I believe a Dyno Dynamics reads somewhere between 7-10% low when compared to a DynoJet. Its known as the "heartbreaker" over at Stage6.
John
Joined: Oct 2003
Posts: 1,058
Likes: 2
From: San Diego
Originally Posted by TelosHedge,Jun 24 2008, 03:14 PM
the boost controller works for sure, because after playing with it on the dyno we had the car making 9psi before vtec. its after vtec that the problems arise.
i have the spring pressure set at 5, and the duty cycle at 42%.
every ounce of turbo knowledge in my head reminds me that a 63mm catback is a major problem for holding boost, especially with an internally gated setup at 9,000 rpms. i keep hearing about how these turbos love to creep with too large of an exhaust though, so i'm not interested in that. i am achieving torque numbers that are acceptable (210ft lbs before vtec at 9psi), its just after vtec that is awful. the car dips noticable (~15whp) and the torque curve (and boost) plummets. power continues to rise but never makes it higher than 260. i can upload the chart but that pretty much sums it up. AFR's are tuned to a constant 11.5.
aqua, you mentioned you peak at 9.5-10psi - where in the powerband? and what is your lowest boost you see and where?
i have the spring pressure set at 5, and the duty cycle at 42%.
every ounce of turbo knowledge in my head reminds me that a 63mm catback is a major problem for holding boost, especially with an internally gated setup at 9,000 rpms. i keep hearing about how these turbos love to creep with too large of an exhaust though, so i'm not interested in that. i am achieving torque numbers that are acceptable (210ft lbs before vtec at 9psi), its just after vtec that is awful. the car dips noticable (~15whp) and the torque curve (and boost) plummets. power continues to rise but never makes it higher than 260. i can upload the chart but that pretty much sums it up. AFR's are tuned to a constant 11.5.
aqua, you mentioned you peak at 9.5-10psi - where in the powerband? and what is your lowest boost you see and where?
Former Moderator
Joined: Jun 2003
Posts: 18,852
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From: New York
From what was explained to me, the optimal setup for a turbine is a completely even pass-through from the downpipe back. This means, if your downpipe is 60mm, the exhaust should be 60mm straight through. If your downpipe is 80mm, the exhaust should be 80mm straight through.
Right or wrong, I took this advice, and my car runs perfectly, no creep, boosting what it's supposed to, etc. My exhaust is 63mm straight through.
It has to do with air turbulence. When a 60mm downpipe meets a 70mm exhaust, airflow IS disturbed. The air "flares" out and caves in on itself. With an even pass-through, the air can continue it's velocity without being disturbed.
Right or wrong, I took this advice, and my car runs perfectly, no creep, boosting what it's supposed to, etc. My exhaust is 63mm straight through.
It has to do with air turbulence. When a 60mm downpipe meets a 70mm exhaust, airflow IS disturbed. The air "flares" out and caves in on itself. With an even pass-through, the air can continue it's velocity without being disturbed.
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Registered User
Joined: Jan 2005
Posts: 1,820
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From: LI, NY
^^^ seems possible but it still doesn't explain why my car made no power and dropped boost when i was straight 63 (and i was beforehand)
boost leaks could be a possibility but as we all know they are hard to diagnose. i suppose i could yank the front bumper and tighten everything up one more time.
boost leaks could be a possibility but as we all know they are hard to diagnose. i suppose i could yank the front bumper and tighten everything up one more time.
Former Moderator
Joined: Jun 2003
Posts: 18,852
Likes: 1
From: New York
Originally Posted by TelosHedge,Jun 25 2008, 12:41 AM
^^^ seems possible but it still doesn't explain why my car made no power and dropped boost when i was straight 63 (and i was beforehand)
boost leaks could be a possibility but as we all know they are hard to diagnose. i suppose i could yank the front bumper and tighten everything up one more time.
boost leaks could be a possibility but as we all know they are hard to diagnose. i suppose i could yank the front bumper and tighten everything up one more time.
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