After reading a lot of posts out there (mostly from John Bradley at English Racing) I have come to the conclusion that S2's might be better for a stoker 10.5.

I would like to get more in-put though.

I am building a DD so driveability, spool and midrang power is the primary goal. I will be running 93, i dont rev over 8k.

So far the mods are/going to be: TBE, Intake,MBC,10.5 , O2, Ported headers, LICP and WB 255, 9BOV, 18psi WG.

Can i get away with S2's and make more TQ and HP without sacrificing much spool?

Thanks for the input.

 

S2's are overkill for a stock turbo. If you are going bigger, they may be worthwhile, but not on a stock turbo.

 

Thats the general consensus, but the few people that have tried it report good results.

Looking to find more folks that have actually tired it. Basically anyone that has big cams on a OEM turbo.

 

I have S1's with a stock turbo I wish I had gone with the S2's. My car feels kinda stock when at idle. If English or Buschur doesn't object I would jump on the 2's.

 

You are going to lose spool for not much top end power...but to each his own...

 

I have gsc s2 on a stock turbo. I didn't do the springs and retainer an set my redline at 7500 rpm. I got them because I can't really see myself spending 2k for a turbo, so I'm trying to squeeze every bit I can wi bolt ons.

It has an aggressive idle, the car do shake a lil at lights. But I don't mind it. I like the sound and the performance.

I have not experience any of the negatives people say about the gsc s2 on the stock turbo. ie. loose spool or low end drive ability will suck or it won't idle.

 

to be honest go the s2 route, you run the **** out of your stock turbo did it takes a dump, then upgrade the turbo, and now at least for peace of mind, know that your cams wont affect the amount of air flow is capable of coming in and out of the engine. Thats usually what happens smaller set of cams cant keep the consistent airflow that the turbo is pushin through so after a certain horsepower and torque, the cams will be eventually your bottle neck, my motto do it right and spend the money one time on parts, less headaches. Case in point, buy the s2s. I dd mine and they work good, a little rough idle at times, but more top end by far. haha

 

Impossible

 

I don't want to be "that guy", but John Bradley says otherwise. OP, this pretty much answers your question:

https://www.evolutionm.net/forums/ev...tle-turbo.html

Thus, I obviously vote S2s

 

^^ Notice I said spool not power

 

https://www.evolutionm.net/forums/9370920-post237.html

 

S2 will do well,

 

It's pretty well accepted that S2s don't sacrifice spool even on stock turbos. Below is a link to a member's dyno graphs where only cams, springs and retainers were swapped...

https://www.evolutionm.net/forums/ev...ock-turbo.html

Different dynos, both dynojet, pulls were started at different rpm, spool shouldn't be affected dynojet to dynojet. Draw your own conclusions. S1 and S2 produce different curves but spool isn't much different between the two. My vote is for S2...there's a reason why they are the most widely used cam in our cars...very versatile from stock turbo to 35r. If you want a more tame idle or don't want to have to swap out the other valvetrain parts associated with a proper S2 setup, those are legit reasons to choose S1 instead, not spool.

 

so here is what i am hearing:

as far as driveability - S1 less top end gains but meatier mid range TQ (more area under the curve)
S2's slightly less low to mid range TQ but higher gains up top (after 6-7k).

I am building the car as a DD so am leaning towards the S1's, it almost never sees over 7k.

 

I had S1's and sold them before putting them onto my car, I ended up with larger cams and didn't lose any spool compared to stock.