I think greddy evo would make more hp/tq at a lower psi vs the HKS making similar hp and less tq at a higher psi.

 

The GReddy Evo TT is making higher whp/tq at a lower psi but it is not allowing the boost to go any higher than 7psi. That's the issue. Having added a plenum spacer, Aquamist system and FI HFC's, I should be at about 420-430whp. The lack of back pressure from the GReddy isn't allowing the 8-9psi required for this higher whp. So in this case, the bigger piping is hurting me.

 

can you run that many hp's without building the engine? doesn't sound very safe

 

Well I think that is about as high as you want to go for reliabilty purposes. Mine actually started to ping and it didn't matter how much fuel we added it was just that the pump gas we have was not good enough.

For longevity I would not go any higher unless you plan to buid the engine in the near future.

 

not true. U bascially maxed out the hp u can get from this setup. U might only get 7 psi from this setup and make 400hp but when u switch back to the hks u might get 9psi but still make only 400hp. It's not going to get u 20-30 extra hp.

Adding the aquamist isnt really going to give u more hp but allow your engine to stay cooler so u wont lose hp as ez. As for the plenum spacers, they usually dont produce hi top end gains but more mid range. U're best bet is getting some headers and hi flow cat.

 

That's not how it was explained to me by Sam @ GTM. I was at 384whp at 10+psi with the HKS exhaust prior to it going back to GTM this second time around. Added to the mix was a plenum spacer, Fast Intentions HFC's, Aquamist meth/water system and the GReddy Evo TT exhaust. The goal was to get approx 420whp but the car wouldn't boost passed 7psi. The combination of the spacer, cats and Aquamist should have easily gotten me over 400whp. But because it wouldn't boost passed 7psi, the whp figure never got passed 400whp. There wasn't enough back pressure because of the GReddy exhaust to help build the boost. And contrary to what you are saying, the Aquamist kit does help make power. Cooler intake temp is going to equal an increase in power. Add a spacer and HFC's and there is no reason why I shouldn't have seen the #'s that we wanted. Sam checked all of the piping and even changed the belt. Everything checked out perfect. There's no other explanation for going from 10+psi to 7psi. It's my bad for not consulting him prior to changing the exhaust thinking that the 2.75 inch piping would help. Once I put the HKS back on and Sam throws it up on the dyno again, I'm very confident that we will see the boost and power #'s come up.

 

so when are you gonna be able to get your hands on another hks? i would've traded with you..............if i was NA

 

Are you using straight water or a 50/50 mix of meth and water?

When are you going to be adding the exhaust and doing to retune? I've been waiting to see some good numbers because I am going to be running a similar setup as yours.

 

Yes, it is a mix called Boost Juice. AS far as the exhaust, I will be getting it as soon as I find someone to buy my GReddy or trade with. Hopefully very soon.

 

when I added my water/meth injection kit, it didn't gain power until more timing was added. It does help keep the engine from overheating or detonating though.

IMO a dual 2.75 exhaust is probably a little on the too big side for a vortech setup with the standard blower and 3.5 liters of engine. I was a little skepical about going to a dual 2.5 exhaust on my car coming from a nismo exhaust, and even then I ended up adding an X-pipe which makes it a little more restrictive. IMO exhausts that have a Y, X, or H pipe design sound better to my ears

 

Sounds like someone should go Fast Intentions......or give your blower setup to me, since I have an FI exhaust.

 

A combination of boost and timing is what makes power on a FI'ed motor. For a supercharger, when there is more flow due to intake and exhaust mods, less boost is acheived (as we all know by now). When there is too much flow, not enough boost pressure is available to create the extra volume within the engine for the extra combustion that forced induction creates (which equals more power).

It is true that with more breathing mods, you can make more power with less boost which is favorable (more efficient). But when you compromise too much pressure due to flow, your car is just spitting out the boost and not holding it in the combustion chamber for the extra power that FI is all about. Finding a happy medium is needed for optimum power. Also, when Sam is advising that Hexx is losing power due to too much flow (i.e. exhaust), I think I would agree with one of the top vq tuners in the country .

 

Exactly, just adding the Aquamist kit probably wouldn't have done much. But Sam did a complete re-tune to take advantage of the Aquamist and other mods that I had GTM install (spacer and FI HFC's) but the boost would not go past 7psi no matter what he did. He initially suspected that it was due to the exhaust being too big. Too make sure, he eliminated everything else that it could have been. Everything else, belts, piping, etc. checked out perfect. This confirmed what he suspected that the exhaust was just too big and not allowing for the boost to go past 7psi. Like I said, I should have consulted Sam first before I did anything with the exhaust so that is my bad. I didn't think 2.75 inch piping would bee too big but I was wrong.

 

Exactly. I couldn't have said it any better myself.

 

there's another vortech guy who's running the 2.75 EVO TT exhaust and didn't seem to have issues though with losing power or losing so much backpressure that it lost power. Though I don't remember what other breathing mods he has

the 2.75 exhaust was developed mainly for turbo setups that need a really open exhaust since the air has to pass through the turbos on the way out. IMO I wouldn't consider a dual 2.75 exhaust until you start getting around a 550whp supercharger setup.

as exhausts get more free flowing, your low end torque takes a bigger and bigger hit, so to me it's about finding an optimal amount of flow throughout all the rpms for your power output - IMO the same idea applies to being NA too, where too big will make you lose power