I suspect that anything more advanced than +2intake is going to result in an extremely funky idle. However, I don't have GSC's but instead HKS, and I run +2i/0e to try to get my JB Red to spoolup sooner. It does like Aaron says ,helps spool but hurts top end power and gives a funky idle. I don't know if my experience with HKS is really applicable to your GSC cams though.

 

physics is physics

 

The reason i ask is bcos while im on stock evo 5 cams i done the same to the intake cam and the idle is real rough but i like it so much and the response is real good but as Aaron said, lesser top end power...

Just wonder can it be done on the GSC S2 cams or just stick it with the factory spec?

 

GSC really encourages 0,0. If you're that worried about spool up get S1s.

 

What is it that you don't understand? There is going to be a power tradeoff if you want to get quicker spool-up and project that rough idle sound by advancing the intake cam timing. There is no free lunch.

 

Evo 8
Same car
Virtually the same boost
S1 is Red
S2 is Green

 

@JohnBradley

Thanks so much for posting this, really illustrates the massive top-end improvement. I think it's the only back-back comparison of S1/S2 on an VIII. Is there any chance you know the mods & fuel on the car?

By any remote chance is there also a stock cam curve with the same / similar mods?

I've got some S2's on order and will post before / after airflows since I don't have access to a dyno.

 

Great comparison graph! That really tells a lot. Even though the pulls of course don't start at exactly the same rpm, you can really see the S1's shine before 5200 and the S2's take over after that with quite a bit more airflow up top

 

92 octane, all the normal bolt ons. I should have the graph off the same car actually.

100rpm is pretty much the same when it starts at 2100 or 2200. But yes, on an VIII there is a difference between S1s and S2s down low that a IX will hide.

aaron

 

So with S2's, you also gain spoolup on an VIII? (everything else being equal)?

 

 

Big bump for English Racing coming through and putting some data to this age-old question / debate.

How does fuel quality figure into cam selection? I'm stuck deep in bad 91 octane land, with no E85 in sight. Is it going to be easier to tune a wide smooth powerband with the big cams since peak cylinder pressure is lower overall, especially down in the RPM range? So far my engine isn't real knocky at high revs.

Are the GSC beehives the goto springs for either setup? I'd like to run the least seat pressure that'll still support 7.5-8k (DD, auto-x, HDPE).

 

Normally it loses a little, I think it was a fluke that this particular one picked up spool over the S1s. The S3s on the otherhand definitely slow things down some.

I would just grab S2s and make it work as well as it can on 91. On a stock turbo anything larger is counter productive it seems. For what you want to use the car for the S2 will give you the best blend of mid range and high rpm at a reasonable boost level on 91 octane. GSC makes springs to match the cams so for 99% of the combinations you'd be using these cams in then its the one I would recommend.

There are only 2-3 or times I would say differently. Neither use an off the shelf GSC cam, both are high lift and high rpm, as well as being high boost.

aaron

 

Nice. Aaron do you still think this would only get me about 12-15whp on my car?

 

damn...maybe now I am second guessing my S1 cams...lol.