Had my '05 reflashed and dyno tuned by Shiv last week. I just installed some mods and wanted to get the most of them.

-HKS 264's
-Vishnu cam gears set to -3/-3
-Turbohoses.com IC pipes
-Helix O2 housing
-Tanabe DP, 2.75"
-Helix HFC, 3"

The car made 255 peak hp and (iirc) about 250 lb/ft of torque on 91 octane (Mustang Dyno). I didn't want to make the car any louder than stock, so I left the stock catback on. Shiv showed me on the dyno printout how HP built until reaching 255 early, but then flatlined from there to redline. The engine was trying to make more power, but the restriction of the stock catback was holding it back.

Further research last week indicates I can get a catback not much louder than stock and still free up the exhaust somewhat over stock. So I'm currently looking at some of the quietest ones on the market and I'll be back to Vishnu's for some final tuning.

Took the car to Thunderhill over the weekend and I'm very pleased with the way the car ran. Much stronger throughout the rev range and no hiccups of any kind. Thanks again, Shiv!

Quick question: can I have the idle raised via Xflashing? I find that installing the 264's have created just a hint of lope at an idle of 900rpms. Raising it to 1100rpms smooths things out considerably, but it appears that the idle returns to 900 shortly after I adjust it. Is the factory ECU compensating for any changes I make to the throttle body idle adjustment screw?

Joe
www.joe250.com

 

you need to get catback, I made 277whp 286wtq with about the same mods as you. This was on the same dyno.

 

.....when modding a turbo car.....start at the rear of the car and work your way forward!

 

Thanks for the responses guys. I should have made it clear that I was not surprised to hear that running an aftermarket catback would make more power. This goes without saying. I just thought it was interesting that the stock catback was choking off the HP even with the relatively few mods I'm currently running. And the only reason I wanted to stay with the stock catback is to avoid making my car obnoxiously loud or having a freeway drone. However, I'm being told that it is possible to get a full 3" catback not much louder than stock that will still improve flow - something I didn't think was really possible. There's still some compromise, but I think it is one I can live with.

And ROGERV, your comments agree with Shiv's statement to me that just adding a catback to my current setup would yield 20+hp.

Joe

 

Please keep us informed on the Cat Back that you choose and how it sounds across the Rev range.

 

I've got the HKS Kansai Street spec exhaust and love it. It has a resonator in the IP so it doesn't drone on the highway and is nice and quiet cruising around town. At WOT it gets a nice turbine chopped roar but, it's no louder than a Mustang at WOT with flowmasters.

 

You can check these sound recording for the level you're comfortable with.

click me

 

Will do. I'm currently considering the following based upon recommendations on this board:

-Greddy Evo2
-RMR catback
-Fujitsubo RM01A

Apparently having 1 or more resonators should help to dampen or eliminate a lot of the freeway drone and all of these system have them.

I guess my next question is just how much HP these systems give as compared to louder 3" catbacks.

And lastly, a friend told me that installing just a Perrin 3" catback gave him a lot of boomy resonance on the freeway, but when he later added a Perrin downpipe, most of it quieted down. Hard sometimes to predict the net result of various combinations of mods. So any personal experience is welcome!

 

I have an elcheapo megan TBE....I love the sound and have no drone on the freeway.

 

You could also looking at getting a HF cat. I was really surprised at how quiet Donour's RS remained after we installed a 3" DP and highflow cat. There is definitely some power to be had from a less restricive cat, even when you're keeping the stock cat back. Shiv should have dyno numbers for you on the difference...

l8r)

 

Totally. I have only a HF cat + downpipe installed on my car. I've had it running right beside a stock vehicle and the noise levels are almost identical. It sounds slightly "deeper", but even the discerning ear would not say it's any louder.

I have it sort of off the record from vishnu that it doesn't matter which part of the exhaust your replacing if you're only doing one part (downpipe or catback section). The real power for either small mod is going to come from the HF cat. I do throw the p0420 code every 2-3 weeks though...

EDIT: ludi, remember that we test drove it at 2:30am after 7 hours of working on it. I doubt our ears were functioning correctly at that point.

EDIT2: wait. It seems that you already have a high flow cat. I'm confused.

d

 

Naw, your car was waay quieter than mine. I really did a double-take when we took it for the test drive.

Dude, I wish you could hear my car in comparison ... once it clears 7000 it begins to sing ... only to be rudely interrupted by fuel cut at 8K for now.

l8r)

 

He has a helix 3" HFC

 

THE DYNO TOLD YOU YOU NEED A 5 inch exhaust. WHAT IS YOUR PROBLEM. SCREW TEH COPS.

 

That was you yelling that out, crazy man. PM me and tell me what happened w/ your car.

Joe