Since the car is at Buschurs who did all this (engine building, install, Tuning) I am trusting in him to do this. Should I double check his work. Sure I suppose I could but I'm not nearly as smart as he is with Evo's. If you missed it on the first page I said this motor is brand new 0 miles. The car hasn't even left his shop yet but he says the car runs great, and makes decent power. So based off what he said I assume that the timing, gears, etc are all good? Is that a safe assumption?

I'll take a look-see but since the head was dissassembled to port the head to match the 4G64 block I assumed that they didn't see anything otherwise it would have been spoken about in an email or phone conversation.

 

Actually it can. If you have a boost leak, say the compressor is pushing 45 psi of boost and 80 lbs/min of air, but only 40psi and 70lbs/min of air is making it into the engine. So the turbo is doing a lot of extra work which means it has to spin a lot faster. The turbo spinning faster creates more backpressure. On the top end of the operating range, the back pressure goes up faster than the positive compressor pressure. So, with the boost leak, the turbo is doing a lot of extra work creating a lot of extra backpressure due to the turbo spinning much faster having a negative impact on volumetric efficiency. Therefore, no power increase. Is there anything else you'd like to comment on?

 

Just some thoughts

1. Air filter? If you have one, remove it and retest. If possible, use an inlet trumpet as they do help.

2. Wastegate dumps. On the dyno, you aren't getting nearly the airflow through the engine bay. I have seen the wastegate dumps act as EGR valves where exhaust was getting sucked into the inlet of the turbo. The wastegate dumps were extended back behind the oil pan and the car picked up 80WHP on the dyno. It didn't go any faster though down the track because on track, this wasn't happening.

3. Post turbo exhaust. As mentioned, pull the exhaust and see how it goes. Same thing as above though, you need the exhaust to get away from the turbo inlet or it can cause problems on the dyno.


The fact that changing the turbo really doesn't change power tells me it's pre-turbo on the compressor side or post-turbo on the turbine side. Other wise, a bigger turbo would effectively be able to run more boost and still make more power, even though it wouldn't pick up what you are expecting, it would still pick up power.

 

I have done 855-860whp (depending on the day) with the 1.15 housing on a 3794. Housing math would seem to indicate that Josh has plenty left (5/6 * 1.15 = 0.96 single) and it should be spooling far faster ( 0.60 * 1.15 = 0.69 single).

What does the Varex Muffler look like?

 

Aaron, I have one sitting in my garage. 3" in, one small hole for the exhaust to enter the muffler, the butterfly to divert exhaust, 3 inches through, and then out the tip. Straight pipe with no baffling through the muffler. I can text you a photo if you like.

 

Please, but that totally sounds like the issue here.

 

03whitegsr,

Thanks for posting. I'm gonna take your advice for sure and yank the exhaust.

1. No air filter. I wish it was the simple...Man I'd be so happy.

2. Wastegates, I've wondered if the configuration on how the wastegates and dump tubes are situated and if the WG are at the right angle (I think I read they have to be at a certain angle a long time ago).

3. There is a small pipe coming off the turbo that attaches to the downpipe which I may leave on. Otherwise I will just take off the test pipe.

Well going from the 4088 to the 3794 did make more HP just nothing past 33 lbs. It made 50 more or so. 4088 made 675 @ 33lbs whereas the 3794 made 720...You maybe saying but you said it made 624 HP @ 33 lbs. I did say this but this is on Buschurs dyno which is known to be a heartbreaker. So take this car to another dyno and it may be right back up to the 730 hp that I was getting while living in Colorado. So we are not comparing apples to apples in regards to the dyno's.

Good ideas though for sure! Can you think of anything else?

 

Varex Muffler

http://www.maperformance.com/map-sta...cbe-varex.html

 

I'm willing to bet that is your problem, definitly drop that exhaust and see what happens.

 

Wouldn't it be funny if it was that simple. All these yrs, all that money.

 

It's one of those bitter sweet things, it would suck to know all the money and time spent, but on the other hand it would finally be done. In any case I hope you figure it out, I've been down that road before and know it sucks.

 

Josh-
Are you SURE you have a valve in your muffler? I didn't think those were available until recently and your exhaust is older.

Would look like this:

http://www.youtube.com/watch?feature...v=AuvukjbX5-M#!

 

Shawn,

Hey buddy. Good talking to you today been a while. I can say 94% that I have never opened or closed by either a switch or lever or anything like that. Unless ETS had pre-release stuff and dropped this on my order for free. But I've had the same exhaust for 6+ yrs as I got the ETS 3.5 for free.

 

That muffler lost 10whp on a stock turbo car after installation with the valve wide open. Lose that thing like a psycho girlfriend....

....Concrete shoes and the bottom of a lake.

 

So if DB tuned the car to 40lbs as he says he did and then I drop the exhaust at my house, not the dyno and hammer on it is there going to be an issue? Can I go lean, rich = smoked motor? I would assume I could since when the tuning was done there was no change in how much fuel or air was needed since there wasn't an increase in power.