lwood240z Posted December 12, 2009 Share Posted December 12, 2009 Can anyone tell me what the max amount of boost a stock turbo will run? I am planning on around 12-15psi Quote Link to comment Share on other sites More sharing options...
S130Z Posted December 12, 2009 Share Posted December 12, 2009 You can run that boost pressure with the stock turbo, but it will start blowing hot air from then on up. You really would want to run an intercooler if your going that high. First off, what type of power are you wanting to achieve? On a side note, this topic has been covered several times. I really urge you to use the search button before someone rips you a new one about it. Quote Link to comment Share on other sites More sharing options...
Tony D Posted December 13, 2009 Share Posted December 13, 2009 Can anyone tell me what the max amount of boost a stock turbo will run? I am planning on around 12-15psi Anyone will tell you that natural surge point is determined by ambient conditions. Without those being specified, no accurate prediction can be made. Control point is normally 5% below natural surge point. My experiments have shown me around 21-22 psi on a 60% RH day with 25C Ambient Temperature seems to be about the limit. Anything else regarding running close to 16psi will be covered in the archives... such as eating up your thrust bearing, etc... Anything about 10psi is really starting to get out of the design parameters of the stock turbo. You can go further, but it's efficiency drops dramatically. And it's not that great to begin with! Quote Link to comment Share on other sites More sharing options...
Pyro Posted December 18, 2009 Share Posted December 18, 2009 rpms also have a lot to do with it. 20 psi of boost at 5000 rpm isn't the same thing as 20 psi of boost at 6500 rpms. if you are using the stock cam (low rpms) then you can easily run more boost than 15 psi. Quote Link to comment Share on other sites More sharing options...
Tony D Posted December 18, 2009 Share Posted December 18, 2009 I don't know about 'easily'... At 16psi, you are effectively putting 200% more pressure on the stock thrust bearing, and it will not last long. Frankly, I wouldn't waste my time with anything more than 10 psi on the stock turbo. You can use it for more, but the efficency is degraded quite a bit. Anything over 13psi and you start getting into longevity issues because of the stock thrust bearing limitations. Quote Link to comment Share on other sites More sharing options...
MAG58 Posted December 18, 2009 Share Posted December 18, 2009 Tony, is the pressure applied to the thrust bearing linear to the output of the compressor? Quote Link to comment Share on other sites More sharing options...
Tony D Posted December 18, 2009 Share Posted December 18, 2009 It's dependent on area. The original design was suitable for OEM levels of durability (say 70-100K miles) at stock boost levels. But they aren't 'overdesigned' like most other parts of the engine. When you run 10psi, as opposed to the stock 5psi you double the load on the bearing. At 15psi, you've doubled that again. Exponential? One of the biggest things people do to increase longevity at higher boost levels is go to a "360 Bearing" meaning the whole face has a thrust face on it, 360 degrees. Like VW Cam Gears (only one half of the split bearing had a thrust collar on it), for performance loading, putting more bearing there lets it live longer. Halving the loads. Basically, the loading at 10psi on a full thrust bearing would be the same loading of a stock turbo at stock 5psi of boost because the increased bearing surface. Quote Link to comment Share on other sites More sharing options...
Pyro Posted December 20, 2009 Share Posted December 20, 2009 if you have a stock T3 from a first gen 300 turbo then it already has the 360 degree bearing (water cooled center section). Quote Link to comment Share on other sites More sharing options...
Ben Posted December 21, 2009 Share Posted December 21, 2009 Forget trying to work the the original unit up to 1-bar, it's 20 years old. One of the cheapest upgrades to the stock L28ET snail would be a stock RB25DET one. It will come on much faster than the clunky ol' TO3 originally fitted. Ball bearing, ceramic wheel - feed it clean air and oil, keep it under 15psi and it will practically last forever... I'm thinking of using nought more than a high-flow RB25DET turbo on my new forged L28ET. They'll make 250rwkw out of an RB25, and that's more than I want from my engine (the engine should flow reasonable lbs/min too - my P90 flowed 311HP on the bench). Quote Link to comment Share on other sites More sharing options...
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