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A good question for the Turbo Gurus


Guest Anonymous

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Guest Anonymous

I just bought a RayJay turbo kit to use on my 75 280z. This kit was originally made for the carborated 240's, but i have a round housing on it that makes it compatible with my FI 280z. This kit was built in the early 80's and the turbo was just rebuilt. Here is my question. It does not have an internal wastegate. Do i need a wastegate? and if so, where can i get one to use (not a 300-900$$). Preferably off of a junk car. But the manifold adapter doesnt have a place to mount one.. So is I it ok to run without one on this small turbo?? Turbo's are new to me.. Thanks all for the help! I have posted a pic of my turbo on my home page.. maybe seeing it will help you understand. Joe75z

http://www.geocities.com/joe75z/75zcar.html

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My gut feel is that you should have a wastegate.

 

However, some of these early turbo kits had the turbos sized such that they were naturally boost limited. While this will be effective in limiting your boost pressure, you should know that this is about the worst method out there for controlling boost pressure. Basically, the turbine is sized such that it chokes itself off above a certain flow rate. The turbo is forced to run out of it's efficient range, and will heat the charge air significantly. Also, this causes a ton of exhaust backpressure (this is bad).

 

If this turbo originally came with the kit, and you are sure that it never used a wastegate, and that it didn't overboost, then you can probably use it as is. Don't expect much power out of it, though. In this case, I'd recommend getting a more modern turbo, and using a wastegate.

 

If the turbo didn't originally come with the kit, then you should definitely use a wastegate.

 

Also, you do realize that you need to modify your fuel injection system to supply the proper amount of fuel for all of that air that you are now forcing though it, right? This is not a trivial task, and the stock FI system will definitely not be able to cope, as is.

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Guest Anonymous

Thanks for the responce but i just found my answer, the early ray-jay (BAE) kits used a 6psi blowoff valve. It says it can make 25 lbs on a v8, so i am going to get a blowoff and start working on my stock injection system, upgrade to turbo injectors, high capasity fuel pump and fpr. Thanks again!

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The blowoff valve as boost boost regulator is also not a very good approach. It is best used as an emergency backup to a wastegate, as was done with the stock zx turbos.

 

You are going to have to fabricate something anyway, you might as well fab the wastegate plumbing. This will give much better results.

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Yeah, a popoff valve may relieve the engine from boost but it will send turbo speeds into the ozone! Most wastegates work by bypassing exhaust energy before it hits the turbo - a popoff valve will simply vent boost and do nothing to slow the turbo down - yikes!

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Guest Anonymous

On a supercharger then, a simple blowoff is ok right? blow-off and pop-off are interchangeable terms, yesno?

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Generally no. Blow off valve is generally the term used for a valve between the turbine and throttle body, to relieve pressure when shifting. Pop-off valve is generally the term used for an overpressure safety device, most often screwed into the intake manifold.

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Actually, the blow-off valve is iin the plumbing between the compressor output and the trottle body. On non-metered (speed density) air systems, these can be vented to the atmosphere, but on stock turbo z'z and those using AFM's or AMS, should be vented to before the turbo to keep fuel at the proper proportion. icon_smile.gif

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Guest Anonymous

i have a what may be a solution a turbo maifold that is setup for a turbo that snails just like your rayjay does. it also has plumbing for a external wastegate.i am having to relocate the outlet on another manifold to fit my particular turbo for my L-6 in my 510 so my loss might be your gain. also check audi 5000 turbos , they have a really trick stock external wastegate.good luck

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