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Power Predictions, please

bigger flapper = more stable low boost control but also less possible peak boost.

increased flapper surface area with same exh mani pressure = wastegate actuator overpowered sooner
 

skivittlerjimb

Well-known member
Joined
Jun 20, 2003
Messages
1,440
Location
Danville, CA
Yeah, I was a little skeptical on the Bullseye housing after having read a bit about them a while ago, but I'd sunk my $ into this turbo a long time ago and figured it was finally time to use it. Might have been better off to use the regular Big 16G that had been on there.

For my purposes 16psi and this power level is good for now. There won't be any events for this car that require extra power until April.

-Jim B.
280/1000
 

skivittlerjimb

Well-known member
Joined
Jun 20, 2003
Messages
1,440
Location
Danville, CA
Drove her back home from DSG today, about 4 hours on the highway at 80-85mph, 21.5 mpg. Big grins. 9.0 compression means more power on tap right now, less lag, more flexibility, less waiting. Power still hits hard at 3.3k or so, and unfortunately it does drop off a bit earlier than it did before, but the gains are dramatic, usable, and real. Also, finally banishing those phantom knock demons (for good, hopefully) make the car much more pleasurable to drive.

Looking forward to making this motor flow and expanding the power band a bit towards the 6.8k or so shift point I used to use or even a bit beyond that. I'll have to get more comfortable with the new powerband, but I'm guessing 6.2k or so shifts make more sense now. A 20G, 272s, 3" exhaust, and a bigger IC unit are the plan for now, but that's a good 6-12 months away.

One unwanted new condition is at tendency to stall when coming down from higher rpms back to idle. I'm guessing the new lightweight flywheel (ACT Street Light, IIRC) is a contributing factor. It still pulls good vacuum at idle (around 22") and when idle stabilizes it does so at 900-1k. I'm wondering if bumping up base idle a bit will help, or if the DSM link might need to played around with a bit to stabilize the idle, or does it just have a leak? /ubbthreads/images/graemlins/dunno.gif Right now I can live with it, but I'd like to track it down so it's not always in the back of my mind when driving.

Either way, more big props for Alex, Matt, Nick, and all the guys at DSG that touched this car and breathed new life back into it.

-Jim B.
280/1000
 

Bimmubishi

Well-known member
Joined
Jul 15, 2003
Messages
5,703
Location
Boston, Massachusetts
No problem Jim. Good thread. I think that in hindsight we should have used your old MHI 16g and not the bullseye one. I've never been a fan of those either. I think that the boost falls off so hard because of the turbine housing design and the power falls off as a result of that and the cams.

There's plenty of potential in the car you need a 3" exhaust and even a MHI Evo III would be better. We could make 350ft lbs with a race gas tune and a turbo that holds 21psi to redline. The Bullseye tapers from 21 to 16 at redline with a couple of different controllers on there. Unfortunate.
 
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