Current:

GT35R @ 7.5psi w/ 2.5 inch down pipe, test-pipe, 2.5 inch Nvidia Ti-dual.

Church says If I'm going to upgrade further to say 12+psi and a head gasket I need to go 3" at least to get the full benefits.

What's the easiest way for me to do this, I considered Just doing custom piping from the turbo all the way down to where the pipes turn dual, Once they're dual 2.5+2.5" = 5 inch flow.

OR how about one of those butterfly valves that just dump it to the street when I really want the power? Run 3" down pipe to 2.5" exhaust and have the butterfly split off the downpipe?

Any other good ideas you guys got? What are my best options. Currently its the Rev-hard 2.5" down pipe.


Also I've heard crazy spans of numbers w/ different head gaskets going to 2mm or to 3mm. Inline pro said if your gonna do a head gasket make it 3mm or don't bother. I understand their opinion there of course, and I don't think they make a 2mm lol.

0. stock=8psi max.... (perhaps up to 9.5-10 w/93 octane I've heard)
1. 2mm= max boost? blues2k3 says 21psi safely!!!! I thought it'd be 16psi or so.
2. 3mm= max boost? what then 30+psi?

The 2mm gasket will hold 21psi safely with no concerns. Get someone to tune your car safely and you will be fine. - Blues2k3 <<<< I trust his opinion...his car is insane. If thats fact though why run 3mm? 21psi Is more then I need to put down. He

 

3mm gives you the added headroom for error and little things that you don't plan on going wrong. I'd get it just for the peace of mind.

Dual 2.5" does not equal 5" of flow because duals are much more inefficent at letting exhaust gases out as fast as possible. Getting a 3" single from the downpipe back is the most efficent route to go however it will be loud so be aware of that. However I run it and it doesn't bother me to much....if your coming from an invidia (like I did) it'll be QUIETER

 

Love the dual look..... not often do i put looks before performance but i have an O.C.D. issue with non symmetrical stuff....

I agree its not like 5" but....its gotta be as effective as adding a half inch!

2.5x2 must = ...what 4? ...AT LEAST 3.5 or 3" equivalent. It does have to physically push more air...but ...at less speed.


as far as the 3mm goes..... its gonna make my car suck balls off the boost... even 2mm will make it worse then current.... and if blues2k3 says i can get away with 21psi safely at 2mm???? how about I just run 19psi and be tottally safe.... I'd have to run 27+psi to make up for that 3mm loss over the 2mm.

 

3" Dual

You could upgrade your DP to a true 3" as the 2.5" is definately a restriction with the 2.5" DP. A 3" system might give you the gains you are looking for with out changing the DP too.

What sort of HP are you currently making at 7.5 psi?

 

 

i am running a 3mm headgasket and have no issues around town. The off boost driveablitly isnt't affected at all... at least on my car? Then again its been a while since i had higher compression!

I built my own 3inch DP and got a good deal on a 3inch single exhaust with magnaflow muffler and resonator. The turbo spools up more readily and i get 3-4 psi almost instantly when i floor it around 3k rpms with a 60-1... Its louder than stock and has some drone, but is not as loud as my old T1R 63mm when i was supercharged!

I personally won't boost over 20 psi (am at 18psi as a high boost) on readily available 93 pump gas! But i DD my car and don't put any type of octane booster incase of a bad tank of gas... If your tuning at church, i presume your using cali's 91 octane, so i would be very careful pushing 29ps or 21 psi with a 2mm headgasketi!!! especially on a stock block...

 

I have run 17 psi on 91 octane, but with a fully built low compression motor. It's not worth the risk of detonation IMO for those few extra ponies.

15 psi with a 2mm HG is the most aggressive I would personally feel comfortable on with 91 octane. All it takes is one bad tank of gas. With fuel prices and the availability of 100 octane being scarce at the pump, spiking the tank every fillup becomes impractical for a daily driver, if that is the case. For a 2nd car, it is another story.

 

It isn't as easy as just saying well 2.5x2=...what 4. There are many more factors then just simple diameter (the largest being simply the actual flow ie turns bends, etc) Nothing will be better then a single 3". Its nearly straight through, 1 muffler, and perfect sizing for sub 600+hp atleast.

Duals will have 2 mufflers, non-straight design, and the need for a Y-pipe.


And for the 3mm driveability, have you actually driven a s2k with the compression dropped by a 3mm headgasket? Listening to a random person talking about it (when they probably own a NA s2k) isn't good enough to make assumptions. Many turbo guys (including myself) can attest driveability is HARDLY affected

 

I drove one with 2mm and noticed a "slight reduction" off boost. I figured that another mm would just exaggerate it that much more where it'd go from "slight" to "fairly noticeable" ...Good to hear you don't see much of a power decrease w 3mm though.

I don't get how blues2k3 is sayin safely 21psi @2mm.

lets assume hes on 93 pump vs. my 91. knock it to 19psi to be on the safe side again..... Then add a 1mm addition to the 2mm gasket =3mm and from what he says 3mm should end up being like 30psi of boost. I'm estimating its about a 10psi limit per mm. stock=10 MAXXXX 2mm= 20psi MAX...3mm 30.

the idea makes sense, assume some other variables come into play here, and even so doesn't it seem at 3mm 25psi would be plenty safe on pump if hes hitting 21 safely at 2mm?

Also on the exhaust, I figured i'd chop it right to the Y of the duals. And chop slilghtly into the Y itself to mount the 3" flush to it. sure its a extra bend or two... but if it was only about power I'd just run a 3" down pipe with no exhaust at all, I know that makes the most power.

As far as a stock block goes.....wouldn't that make NO difference at all. I mean were talking top end issues, not bottom end. As far as I see it the bottom end could care less about how the power gets there... Pressure on rods is pressure on rods, no matter if its from high compression or from boost, the power to the rod is the same. (I know that the piston heads back down easier on boost but thats a small factor) Lets assume then that 18psi would be a fairly safe number for me on a 2mm on pump? If we agree on that then why go 3mm...all that'll do is make me loose power across the board especially off boost, I'd see no point in it other then a bigger safety margin which I already made by cutting 3psi of what he said was "safe already". I guess I'd figure a 3mm is only useful with a fully built bottom end. Since 450hp is achievable on safe boost numbers @2mm gaskets. 3mm is just a loose loose? unless you can make use of it by adding boost numbers like 27psi etc.... which makes no point cause my bottom end isn't good for that much.


oh also I have 110 at the pump a block away from me for like 6.20 a gallon. Church was sayin I could run race fuel and at 11.1-1 compression i could get away with 12psi..... amazing power that'd be with that compression ratio.



thoughts on all this?

 

I think you could run at LEAST 15psi on stock compression with race gas considering I ran 10psi no problem on stock compression with 93 octane.