what boost would 290% tapering to 240-250% be, and is this an average amount of taper? im still trying to find out where my power loss is coming from. i cant seem to find any leaks, but boost drops pretty quickly. ive also not been able to run as much timing as i use to without knocking.

 

Based on your mods and your numbers in your sig, I wouldn't say boost leak. If a leak were noticeable on your setup you'd be seeing 320+ load ... I've seen 340+ load on a stock turbo'd VIII due to leaks.

It could just be the boost controller. Have you considered active boost control via the ECU? That should help with taper.

 

I haven't read up on it too much, but the only thing that seemed a little inconvenient about it is that I would have to reflash the car anytime I wanted to adjust boost

 

my problem started after i installed my o2 dump. the car felt really strong after the install, but it must have been all in my head because when i went to retune, first pull was like 402 or so, 20+ hp loss, torque remained the same at 386. this was about a month after i made 424 on pump, at that time the car was a beast, on the dyno it would take anything we could through at it, now it seems to drop boost rapidly and doesnt want timing anymore. the car did get a few changes aside from the dump, the air filter was changed for a different brand and a different 3" catback. i did find some issues, i found that when i used the turbo nipple for the port of the mbc, the wastegate would open verrrry early, which i assume can attest to the solid 10-15whp drop across the powerband. i still havent fixed that problem, but i did swap pressure sources to the bov line, and the wastegate operate likes it is suppose to now, but it is still dropping rapidly. in 3rd where i use to hold nicely hits about 25 psi and is down to about 19 or so at redline.

a little side question, would a compression test be unnecessary? we did manage to get the power back up to about 420, so we are not too far down, i would imagine bad compression would result in a much bigger drop.

**i have pressure tested, all the way up to 30 psi, until the valve cover gasket started to leak, followed by the tester exploding off the turbo.

 

Is there a chance that you had boost creep keeping the boost up before the dump was installed? Which dump do you have?

 

EPM o2 dump. no boost creep before. boost never held greaaat, still tapered a bit. but not as bad as now. i have a feeling theres some type of exhaust leak around the turbo somewhere. it just really lacks up top, it almost feels like as soon as that dump opens, the power drops.

 

I had the gasket blow between the turbo and the manifold with similar symptoms. Torque was the same, and hp was off a little. Also had a load spike. Look for carbon in that area surrounding that area.

 

this was on stock o2 housing, or dump? the o2 dump doesnt have a gasket, just a spray on copper gasket, maybe the copper gasket wasnt very good. i heard it mentioned that they had a problem with the copper gasket melting off when they were shipped.

this could definatly explain some things, when it was first installed the car was idling as lean as my wideband could read but almost felt like a false reading because the car was rock solid at 900, no dipping or wanting to stall or anything.

what would an exhaust leak there effect though if that exhaust escaping has already gone through the turbo to spool it. i may be wrong but an exhaust leak before the turbo would better explain my symptoms. i guess my question is, would an exhaust leak at the o2 housing effect the boost up top, would it cause the turbo to not work as hard?

 

You're right ... it's more likely a leak before the turbo if a leak at all. What mani are you using?

On a side note, EPM does have a gasket for the O2 housing now. If you think it may be an issue, I'm sure Q would ship you one. I don't think that's your issue though.

 

stock ported. which was not removed when the dump was installed, your right though, i dont think that is the problem. i did get ahold of epm and they are sending a gasket, if i ever get around to pulling off the turbo to see if i can find anything out of whack il throw it on.

no big deal, il get it figured out, we did manage to get the power back up to 420, so it was a loss of only 4hp with a part claiming 15 wheel. im not really too worried about that, my main issue is that i want to go e85, but if im just gonna drop boost its going to be worthless. the day we retuned for the dump, we tried a race gas tune, we were hitting 29 pounds and we were down to 19 pounds by redline.

i think i may give the ecu controlled boost a shot, see if that helps any.

 

Well, I can vouch for the EPM part as I did the testing. Did you only lose peak power or power across the entire rev band? I gained 19 hp/tq in the 5200 area, but only about 5 hp peak.



Jestr has also said that he's made power with the part. I've got a feeling that something else happened with the install.

Have you actually done a boost leak test or have you only checked the couplers and such?

EDIT :: Nevermind ... I saw the line in your post above.

 

oh trust me, i have seen what the part can do. everybody that bolts one up gains power, i dont think that its the part itself, just something that may have went wrong during the install.

it was about a loss of 10-15hp across the band

 

Maybe you should pull the manifold and check it out? I've seen the cost manis crack under extreme use ... it's just not as common as the issues with tubular manis.

 

In my post I say betwen the turbo and the manifold.

 

By doing this the pressure behind turbine is less. So whatever decrease in backpressure (at higher rpm) obtained post turbine will be felt accross the WG.

If this is the case, your probably making better power now than before as boost is tapering. Natures way of keeping engine happy.

This is more common with stock turbo's however