6cm^2 housing too small?

[seefour]

Long, but I dont want to leave anything out...
Recently I picked up a Forced Performance 18g without the turbine housing. So, like most people, I used my 14b housing thinking it would help spool and cut down on cost. Everything is fine and the car pulls much harder than with the crappy 14b. Then, I take it to the track. My first pass was a 14.5 . (I ran a 13.4 with my old 14b). Ok, im running extremely rich and I just need to tune right? So, with a few clicks of the knobs on the gm-mas and I've got a somewhat decent tune. A few counts of knock at spoolup and maybe 2 counts up top in 3rd gear. Next run, 14.1. This has to be a joke right? Then I decide to look at my boost gauge while I run. Boost spikes to 18ish Psi then settles to 17ish. Then as soon as I hit 5k boost starts to drop to 15Psi and the car runs pig rich. Originally I thought it was my wastegate actuator going bad and getting blown open, so I switched it with James. This didnt help at all. Now I'm leaning towards the motor outflowing the turbo. So my question is, Is the 6cm housing causing the motor to outflow the turbo? I know smaller housing = greater exhaust velocity, so is the velocity too high for the td05 turbine? Will a 7cm housing help at all?
Mods list: 18g, walbro 190, 650's, pocketlogger, Eprom chip with injector compensation, 2.5" exhaust, Evo exhaust Manifold, 25X7X3 FMIC, Maft blow-thru.
-Thanks for any help,
Nick

 

[XakEp]

Smaller housings will help spoolup alot, but will kill top end. Bigger is better. You shouldnt be worried about spoolup at all on that 18g, its not going to be bad at all. Just put a bigger housing on it and be happy.

 

[blcknspo0ln]

your logic sounds right, but i'm going to lean towards your tune. get that on point and you'll probably see better results.

oh, and get a 7cm or bullseye a 6cm is more than likely restricting your turbo from its full potential

 

[BaddAssGst]

Smaller housings will help spoolup alot, but will kill top end. Bigger is better. You shouldnt be worried about spoolup at all on that 18g, its not going to be bad at all. Just put a bigger housing on it and be happy.

Definitely. I run an 18g and I see full boost, 20psi, by 37/3800 rpm. Open up that 6cm housing or if you have funds, go with aftermarket housing that isn't cracked and already flows more air.

 

[seefour]

I'm not concerned with spoolup at all. I can deal with lag. I just wanted to be sure it was the 6cm housing that was causing my boost to drop off and not the brand new turbo that was already dying. I will be getting an evo turbine housing for it soon though, so I will let you guys know how its works out.

 

[BaddAssGst]

I'm not concerned with spoolup at all. I can deal with lag. I just wanted to be sure it was the 6cm housing that was causing my boost to drop off and not the brand new turbo that was already dying. I will be getting an evo turbine housing for it soon though, so I will let you guys know how its works out.

Are you running it with the stock oil feed or the SS line? I've only run mine for like 500 miles and I already have a small amount of shaft play. Not sure is this is common or not, but I wasn't to happy with it.

 

[seefour]

I'm still running the stock line. But would that cause the turbo to die in the upper rpm's?

 

[funniegus]

Try some porting.

 

[Thomas91169]

im going towards running out of flow with the stock housing. definately a larger housing with some port work. maybe port out the evo exhaust manny a little to match the new housing.

 

[seefour]

I forgot to mention the turbine housing is heavily ported to 7cm as well as the manifold.

 

[blcknspo0ln]

I don't think that would do the job..

I've seen the 1g/6cm and they're puny compared to a 2g/7cm.

 

[seefour]

Well i got a evo3 turbine housing on and now 18psi to redline! Now to get some track times. Thanx for all the input everyone!