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[Scratch]

Just joined.

Been involved with turbos for a couple of years and would like to gain some more understanding. Hopefully this site can be helpful.

I have a couple of foreign cars that I have been modifying and tinkering with. It has been surprising to me the difficulty in getting some basic info.

Do folks here welcome foreign car people?

So I have an Infiniti g35 that has a JWT basic turbo kit that has been modified. My questions have to do with controlling the waste gates and internal vs external options.

Seems like most kits come with a spring preset actuator of +- 5 psi...where does this number come from?...why 5 psi?

[Big Dave]

Every one is welcome. I personally have rear wheel drive American iron powered by Chevy, but we still talk to Ford owners so we can talk to you as well. Only rule is to be polite.

As to your 5 psi question it can be fiddled with to raise the boost but when you do you have to also raise the octane of the gas you burn. Even a cast piston will last in a blown motor. The difference between the cast piston and the forged piston is how they behave when they fail. The cast goes to pieces leaving a forged steel flail of a connecting rod to beet on your engine, the forged piston gets a hole in i and that is the end of the drama which is why racers love forged parts (no collateral damage).

Big Dave

[clay]

I don't think anybody here has a problem with foreign cars. Can't promise there won't be some friendly ribbing though. My main problem is I might not know any specifics about your setup but I'll be happy to learn and try to help you. Anyway, my guess on the 5 p.s.i. thing is safety, cost and simplicity. Basically you have a lot more room to screw up at that boost level and not hurt anything as far as timing, fuel, etc. Also my guess is the turbo company has much less to do as far as fuel and ignition tuning. Might can run the factory injectors, mass air (if it has one) and this makes thinks simpler and cheaper for the installer / user. External vs. internal wastegate mainly refers to the location of the valve that opens to let the exhaust bypass the turbine. If it's part of the turbine housing it's considered internal wastegate - separate is external. External lets you get the bypassed exhaust gas back into the exhaust stream further down which effects performance less. On a race setup it just gets dumped to atmosphere. By doing this you can increase the pressure differential across the turbine which lets it operate more efficiently. As far as control goes, the spring setup is very simple and effective. There are several types of boost controllers out there. One type either uses a regulator or a bleed valve to modify or bleed off the manifold pressure signal that opens the wastegate. By doing this it now takes more pressure in the manifold to open the wastegate. They are cheap and simple. I use a MSD boost contoller that allows the boost to be ramped up (or down) over time which is necessary on a drag car and it's still fairly simple. There are much more complicated boost controllers for fuel injected race cars that control about everything but they are pricey. Hope I have covered at least some of what you wanted to know. If you have any specific questions, let us know. Welcome to Smokemup. Clay

[clay]

Just thought about this. Dave brought up an excellent point. The 5 pound limit helps save an engine that wasn't designed for boost to begin with. Static compression most likely is a bit too high and like he said, most likely the owner is wanting to run pump gas and that doesn't always turn out too good (ask me how I know that one ). Clay