How many PSI can u boost with stock turbo?

[Turkish]

I have a 88 Toyota Supra Turbo. Hks metal head gaskets, Hks intake, engine strut bar, full 3" exhaust no cats with hks downpipe, electronic boost controller. So my question is how much can I increase the boost to with the boost controller on a stock turbo or should i just leave it at the 7psi?

[robroy32433]

wish I had a metal head gasket...the problem is multifaceted in that the stock toyota intercooler runs at a low efficiency (68% or so)and robs you of boost psi.As you incresase boost psi the losses get even worse.The main problem is that the stock system is set up to cut off the fuel when the boost pressure gets
somewhere over 11 psi.So you can run at a higher boost pressure with the stock turbo but you have to address the heating caused by the inefficient intercooler and most of all have to modify your injectors and fuel pump to give a richer mixture.
you did a good thing in reducing exhaust back pressure for a
start that is the cheapest thing to do.I think however as long as you stay under 11 psi you will be ok with no further mods.I am not an expert at this but that's a safe level.

[bgrieger]

The stockers put out good production up to about 14 PSI, but no one has any maps of the turboefficiency to know what the actual cutoff is, so this is represents the real world tested safe level. Beyond this, the turbo's own efficiency drops too fast to keep going effectively (though some do press them to 18 or so PSI...not for long however). You generate more heat than pressure beyond this point. Upgrading the compressor will net you some extra flow, but the hot side is the real restriction and will get into creep and other issues pretty quickly.

The intercooler is not great, but better than most factory ones. It will run most people fine to the limit of the CT, but of course you would gain some more from upgrading it too.

You'd probably be able to run it a little more efficiently if you tossed the HKS DP and picked up a true 3 inch with an upgraded/integrated elbow.

Bob

[Turkish]

thanks guys could u link me to a better intercooler, injectors, and fuel pump thanks guys

[bgrieger]

Injectors are not worth looking at until you get over fuel cut. Stock, good condition ones will do you fine to there. Injectors also need engine management or a lexus AFM mod to take advantage of them. until you reach that point, don't bother.

Intercoolers...whatever floats your boat. Cartech, Greddy, HKS, Spearco, RRE, etc all make decent upgrades.