Which is better and why? The 1/2 seems like it makes more power, but it seems like the 5/16 is more popular, is there a particular reason?

 

1/2" doesn't let you keep the engine cover so lots of ppl opt for the 5/16. power is pretty comparable, u might gain 1-2hp with 1/2"

 

I have the 1/2" because I dont like the engine cover anyway. Seems like it would trap heat under there. Just paint the plenum and the spacer edge and it will look fine.

 

If you opt for the 1/2" and remove the engine cover, wouldn't that make you hear more engine noise...kinda annoying one might think...

Scorcher

 

I have the stillen exhaust with test pipes. I cant hear my engine Actually, just kidding. No difference in underhood noise that I could tell. 99%sure the cover is just cosmetic. The VQ valvetrain is pretty quiet.

 

im going with the 5/16th ill keep the engine cover and take the 1-2 hp loss

 

I have removed my engine cover since installing the spacer. I have not noticed any increase in engine noise that the cover might have insulated.

 

has anyone driven the 2 and felt any difference? are the dyno #'s that different between the two?

 

I think I read somewhere on this forum that the 5/16 spacer makes better power over all the power bands than the 1/2 spacer. However the 1/2 spacer gets a little more power in the upper power ranges.

When I am ready to buy, I will be getting the 5/16 spacer.

 

The question is statement true for just the 300HP or the 287HP?

The 300HP MREV + kit works the best with a 5/16" spacer for midrange torque and loses a few horsepower in the upper RPM range.

However I'm not sure if that a 5/16" plenum spacer works the same way on a earlier 287HP engine. It may be the 1/2" spacer gives the best performance

Anyone care to jump in and set it straight?

 

Oh BTW my car is an 04..