timg

I have run 0.63 and 0.82 a/r turbine housings on my GT3076R. Just from the tuning results and my driving impressions, I heartily recommend the larger turbine housing.

Tim

timg

Oh yeah, if that noise you're hearing is compressor surge, the larger turbine housing can help.

Tim

sgd

More info regarding the compressor surge line....


http://www.rbracing-rsr.com/turbotech.html

Surge line: The map width is limited on the left by the surge line. This is basically "stalling" of the air flow at the compressor inlet. With too small a volume flow and too high a pressure ratio, the flow can no longer adhere to the suction side of the blades, with the result that the discharge process is interrupted. The air flow through the compressor is reversed until a stable pressure ratio with positive volume flow rate is reached, the pressure builds up again and the cycle repeats. This flow instability continues at a fixed frequency and the resultant noise is known as "surging".

fperra

One way to overcome the compressor surge is to add water/methanol injection to the compressor inlet. This changes the compressor map sufficiently to increase the HP capabilities of the turbo. There is a long and informative write-up on this in the water injection forum:

http://www.aquamist.co.uk/phpBB2/viewtopic.php?t=267

Guerillah

Correct way to get rid of it is to get a bigger turbine housing, its not matched properly for the airflow requirements of the motor.

slimjim8201

I think it matches the airflow characteristics of the motor beautifully. I only get the surge at about 20-25% throttle in high gears, at low engine speeds. Anything above or below and there is no issue. No surge occurs at any other point and what little does occur is minimal compared to what I hear on other cars.

I think this is a case of the turbine being sized such that the system spools very readily. I seriously do not think the turbo selection is undersized and I think the restrictive exhaust is the main reason for the torque drop at higher RPM.

A restrictive exhaust will have a MUCH larger impact on the performance of a smaller turbo, as it is that much closer to the upper end of it's efficiency curve anyways. Refer back to my dyno comparison with Kleecker's car. My engine is making a LOT more power for almost the entire operating range. Only in the last 1000 RPM or so does his surpass mine. Granted, his turbo will ultimately be capable of quite a bit more HP when the boost is turned up, but for a street setup of around 400-425 rwhp, this turbo is just plain badass.

Guerillah

You can have turbos that spool quickly and still not surge, on my evo9 I hit full boost around 3200rpm, 300ft/lb tq with zero surge. Its getting the right combination of compressor wheel/turbine wheel/ A/R size which all have an impact on compressor surge. But like you said, it only happens in high gears at low speed, so it shouldnt really be a problem. Sounds like its fun, good luck.

slimjim8201

I adjusted the BOV a little bit and it eliminated a lot of the surge. I'm going to further reduce the spring force tonight and see what happens.

alleykat

I just hit the dyno yesterday.Numbers were:

400.12WHP
300??+TQ

Running custom kit with a gt35r at 14psi.Something was wrong with the dyno and it stopped reading torque when it was gonna hit 300.Im guessing a low 300.Maybe 310ish for sure.Im using
aem ems
1000cc injectors
600hp intercooler
3bar map
3in. downpipe exits thru side
topmount mani
dumptube
50mm bov
44mm wastegate

When the new headgasket comes in were definitely turning it up just a little.Maybe to like 18psi.Right now 14psi is more than enough.Pics coming soon..

geists2k

I agree.

My current Precision 76/60 spools around 3500 and I have zero surge.