Just wandering If anyone has switched from The Greddy Evo TT exhaust to the HKS true dual exhaust? I want somthing quieter but am afraid I will loose power in the switch. Right now it puts down 571rwhp on 15.5 psi.

 

You can try adding resonators to the exhaust. I'm assuming you are running test pipes. HKS is every bit as loud as the greddy with TPs. Good resonators/mufflers include vibrant and the Greddy SP mufflers.

My friend addeed a greddy SP to his apexi exhaust on his loud RX7, and it quieted it down quite a bit.

 

I had APS true dual 2.5" with my greddy kit and it was a little louder then stock, i loved it , at freeway speeds it was super quiet and no drone, unless your giving it gas.

 

Tony at Motordyne Engineering is coming out with his FI exhaust shortly (the shockwave TDX is already out, I've tested it with no performance hit, but it's about the same noise level as the evoTT although the TDX version I have has no mufflers!):



There will be a VQ TDX axle back component soon. Supposed to be very quiet with little to no performance hit. It's true dual 3" piping throughout. Hopefully I'll be able to get my hands on one soon...

 

Ill keep an eye out for that! I just like the looks of the HKS but performance and noise is number 1 priority. I wonder if resonators will hit my performance much and if it will quiet it out a bit?

 

I was going to do the same thing but a little research led me to believe that to filter out low frequency drone would require something large due to the long wavelength of the sound (even working with subharmonics, like a 1/4 wavelength resonator). Anyway, I know Motordyne puts more R&D into their products that most, so I'm hopeful they'll come through here soon.

 

just turn the boost up if you lose some power with the quieter exhaust.

of just add in a boost controlled cutout. quiet for normal operation. no power loss when you get on it.

 

Thats a thought! I was thinking of a stock style exhaust with cutouts. Loud only when I need it to be! i wish there was some dynograhs of the same FI Z with diff exhausts...

 

If you get an exhaust that is too restrictive and you have high duration cams, reversion may become an issue. Do some research on this before you leap.

 

Turning up the boost with a restrictive exhaust doesn't work. I tried. You lose top end power and it just falls faster when you turn up the boost. I do think you can compensate with BIG turbos (like on the SP TT kit).

Cut-outs are an option, but they take up space and clearance is an issue (don't want exhaust parts being the lowest part of the car).

I just want something with great performance and super quiet. Is that too much to ask for? No one makes quiet performance exhausts, yet.

 

Dont worry Im not a leaper...It took me 8 months to find the right car. I do alot of research

 

You can straight trade your Z with mine.

 

I am def with you on this Raj as i dont want anymore noise.

 

What About Adding an X pipe to the EVO TT ? some people did the same with the HKS Ti to make it more quiet and the HKS clones now ships with X pipe.

 

the aps 2.5" is a better choice than the HKS. supposed to be zero backpressure to 14 psi. I am running mine at around 15-16 psi. It sounds mean at WOT, but as quiet as stock when putting around town and absolutely no drone on the highway

 

+1

Excessive back pressure in the exhaust leads to higher EGT's and a higher chance of detonation.

 

+1 and if you ever go N/A again like i did, the aps sounds perfectttttttttt

 

please define excessive backpressure and tell us the backpressure differences between the HKS and EVO TT.

as bumping generic answers really doesnt help anyone

I know RCdash did a test trying to get back HP after adding cats into the mix. that would definitely cause more backpressure than going from 2.75" pipe to 2.4" pipe. Chris's Max made like high 600s on 2.5" down pipes and exhaust.

 

str8dum1, as you know, the HKS has a piping diameter of 60mm x2, and was designed for N/A applications. The EVO TT has a diameter of 70mm x2. The exhaust with the smaller piping will be more restrictive, and will negatively effect performance on a forced induction vehicle pushing upwards of 550whp. What exactly don't you understand?

 

I think he's asking how to evaluate at what point backpressure becomes significant or problematic. str8dum1, my understanding is that the turbine is the single largest restriction in exhaust flow. It is the pressure differential across the turbine and the flow capabilities of the turbine that determine ultimate maximum power output. With a restrictive exhaust (either very small turbine or restrictive exhaust), you can only increase boost so much before the pressure in the exhaust manifold exceeds the threshold for reversion and even with minimal overlap cams, you have high pressure exhaust working its way back into the cylinders (because it has no place else to go due to flow limitations between the manifold and atmosphere via the turbine and exhaust).

The bottom line is that if you're flowing enough air to make xxx whp, that air mass has to be let out the exhaust at the same rate as its being sucked in. Turning up the boost doesn't help with making more power once you reach your flow limit for the exhaust. In fact, it only makes matters worse (as ttg35fort and Chris@FsP noted) because your forcing more air into the engine and it can't get out. Hope that makes sense...