Interesting thread! Those numbers achieved by Dynotech are really impressive, my conception of 'turbo efficiency' just went down the drain!! I always thought that anything beyond 26-27psi won't be beneficial on a stock turbo due to turbo efficiency limit (increased % of hot air vs cold, increased pressure with limited or no gains in volume) Mitsubishi never published efficiency charts for their turbos, I've seen charts for other larger than stock turbos & many had less than 30psi efficiency!
Is there a good trick for increasing turbo efficiency?

 

Other than the rough casting imperfections being smoothed on the first turbo, nothing was done to the stock turbo. The 2nd replacemet turbo was completely stock and still hit the same boost and power so it didn't really help any.

Other than changing the housings or wheel design, I don't think there is anything you can really do to change the turbos natural efficiency other than minimal back pressure post-turbo. The only thing I think you really can do is to run an equal length exhaust manifold which should help minimize the pre-turbo back pressure by allowing the cylinders exhaust pulses to be more aligned with less turbulance and keep cylinder reversion balanced across all cylinders.

What we did to this poor turbo isn't something meant for longevity. It had a sole purpose and we knew we would be pushing it well beyond its limits. We had a kickass FMIC doing its best to keep air temps at a reasonable level. We never measured pre-turbo back pressure since it wouldn't have mattered since all we were after was maximum power potential and that was easily determined with the dyno graphs.

On a vehicle built for longevity on a stock frame turbo, pre-turbo back pressure is probably the best thing to monitor to see how well the system is doing. We'll be showing some back-pressure results soon when we launch our new back-pressure monitoring kits for '90-'99 DSM's and '03-'06 evo's that we'll be releasing shortly.

-Jamie

 

id say 25-28psi with no leaks is safe.. 30psi u will b rebuilding the turbo very soon depending on driving style

 

I personally ran 30psi for years and I used that car as my test bed for lots of tuning and stock ECU development without any excessive wear on my turbo. Trust me, that turbo got a workout lol.

-Jamie

 

32 psi on 91 octane here. Been running it for a long time. Takes careful thought and smart tuning, but can be done.

 

Jamie: Sorry about all the questions concerning monitoring and logging exhaust pressure. It is only that I was hoping that you had but only because it is a topic of special interest to me personally. I guess I seemed to be a doubter. Not at all. Anyway, I appreciate all of the info that you have provided to our Evo community. I wish you continued sucess. Happy New Year.

 

im gona have jamie tune my evo next month and would love to run 30 psi all day if possible on 93...!??

 

When I ran 30psi it was with the addition of an Aquamist alcohol injection kit. I generally don't recommend 30psi on pump gas generally because of some pretty steep air temps with a less than adequate FMIC and the knock limit of pump gas generally will have the same power result as it would with more ignition timing at lower boost. 25-27psi is generally the most I would ever run on pump gas depending on the setup.

-Jamie

 

Which Aquamist kit were you running and what were you injecting at the time?

 

I believe it was the HFS-6 kit with dual 1mm nozzles spraying all mixtures from straight meth down to 30% meth/ 70% distilled water. Like I said, the car was my test bed for lots of data so it saw a lot of different scenarios in only a few years.

-Jamie

 

Evo 7 turbo w/10.5 hotside

-holds 28 pounds from 4000-5500, falls to 24 pounds at 7k
-93 octane w/ full supporting mods GSC S1 cams, 3.8" garret intercooler, 3" 02 eliminator, FB 70 throttlebody, Rev3 intake etc etc
- 416 WHP, 394 Ft-pounds

 

Relevance to OP's question??

 

Yea, it's off topic, but did any of the Evo 7 models had a 10.5 hotside? I thought all E7s had 9.8 hotside!

 

I've ran 30psi on a stock IX turbo (pump gas, BR Race IC) and i can tell you that at this pressure level don't plan on it lasting to long. I went through 1 a year until I changed to a bigger turbo.

 

The biggest things to make that boost level safest and longest lasting would be proper BOV ventilation, low backpressure,and oiling. 30psi on a 10.5 hotside with minimal backpressure, no BOV or spoolup surge at all and a high zinc and phosphorus motor oil should give you plenty of longevity at those levels. This turbo should be fairly capable of a pressure ratio of 3:1 with a good lifespan. A 9.8 hotside turbo will have greater backpressure and would have more strain.

-Jamie