New member here, and I really did search the site, but came up with not quite what I need.

I'm gathering the details needed to swap a 302 into my 240sx and plan on running a turbo setup. I'm pretty well versed in sizing wastegates for turbo 4-cylinders, but have no experience with the V8.

So, my question, what is an appropriate wastegate size for a single turbo, 302 making around 400whp?

Thanks again. Sorry for askin' what is most likely a basic information question, but I couldn't find it searching.

 

Ok, on my current 4-cyl (350whp), I get by with a 38mm Tial WG. This gate will be sufficient up to 450whp. However, this is a high boost application (15psi @ 350whp).

I'm expecting no more than 10psi on the 302 (probably less) through a single, so proportionately, more exhaust gas will be diverted through the gate. So, would it be safe to assume a 40-44mm gate for this application?

Thanks again!

 

I agree, my 38mm was unable to control my 13 psi after I got rid of the flowmasters. I was making 550 rwhp. I am now stepping up to a JGS 50mm wg.

You need to decide what your future plans are and how restrictive your exhaust is going to be. If you don't ever plan on making more than 500 rwhp then you will be fine with a 38mm. If you are planning to go further then I would atleast buy a 44mm as it will leave plenty of room for growth.

If I would have upgraded to the 44mm then I wouldn't be reworking things now. Who knows, the uncontrolled boost creep is probably what contributed to my transmission breakage.

 

WG size also depends on the turbo your tring to use. If its a fairly small turbo with high turbine pressures you can use a small WG.
The high turbine pressure will make the WG flow more.
But if your going with say a MP70 etc. a small WG will raise the minimum boost level and MTL creap a bit on top.

44-50mm is a good size for a 5.0+V8. With exessive displacement (compared to a 4 cylinder) there really isn't a wastegate thats too big.

 

Tial 44 like most kits

 

I have no idea why the WG manufacturers say that their product "will support up to X horsepower." The horsepower goes up as the size goes up. WTF? If anything, they would be more accurate to say, "will support a MINIMUM of X horsepower" with the bigger WGs (since they are able to bypass more exhaust and keep the boost down). If you want to make more power, then run more boost, or let boost creep take over...both of which can easily be accomplished with a small wastegate! lol

I ran a 32mm Deltagate on my 302 with 60-1 hifi, and it was a boost creeping freak in 3rd and 4th gears (14 psi on a 7 psi spring). I switched to a 42mm Racegate, and I was able to keep the boost around 7 psi with no problems.

Mark

 

A HP rating really is a huge guess, nobody actually knows how must will need to be wasted for X setup. Trial/error is sometimes the only way due to the wide range of possible heads, cams, turbos, etc, etc. Turbonetics was famous for putting HP rating on WGs, but these are made with ALOT of assumptions and not true for hardly anybody nowday because the engine parts and turbos have advanced alot. Can you picture a racegate handleing 1000HP with say a 91mm, large AFR heads, etc. ? Maybe if boost creep was the goal.