DaveHelmig

Ok, I took my 8 out to straight pipe (just lost the muffler and ran the pipes out to the 2 tips)... now I lost all my torque, and unfortuantely sold the stock exhaust already. Now what?

I assumed going to straight pipe would have increased the torque... definately not. My 8 now has no guts whatsoever.

Question is... what can I do on a budget to get my torque back? The straight pipe sound is nice, but willing to trade the sound for my performance back. I see some cheap mufflers on ebay for like $40 shipped (fireball, etc), but they are the vertical type mount, not a sideways mount with the mid inlet like the factory can and not sure if there is mounting room under there for a length type mount instead of sideways.

Any suggestions?

(I know I was a moron, please refrain from flaming... it's too easy in this case, lol)

delrmx01

iTrader: (1)

Soooo, you don't have a muffler at all? That must be loud as hell.

alnielsen

iTrader: (4)

Computer put the car in "Limp Mode"?

DaveHelmig

Exactly. Computer problem I think, and dont have the $$$ to remap the ECU. Yes, no muffler at all... Actually, it sounds good, it's not overly loud.

Any ideas how to fix it?

kw1k

notice any high end power?

delrmx01

iTrader: (1)

Try clearing the ECU?

TrackAddict

many people on here selling their stock exhausts - put a WTB thread out.

StealthTL

iTrader: (1)

It might be OK if you just reset the computer....

Disconnect the battery, push the brake while it is disconnected, then hook it up again. Turn key on, but don't start, tap brake pedal fast about twenty times, oil gauge should swing to middle then back to zero.

Now start up, and drive around gently. ECU is in learning mode, and will adjust your mixture fuel trims for the leaner "no restriction" situation.

You will probably get a CEL after two dive cycles, due to the secondary O2 sensor reading high, no way around that.

S

zoom44

ripping of the muffler should not result in any noticable decrease what so ever. perhaps ther eis an exhust leak or something? obstruction in the pipe somehow? kink ior crimp in a bend?

TeamRX8

iTrader: (25)

funny, everybody else saw an increase ...

mikefrombarrie

Do you have any pics? I might be intrested in buying your exhaust from you if you want to sell it.

Sounds like a good system for a turbo setup?

DaveHelmig

Looks like resetting the ecu might have took care of it. Did a 10 mile loop after resetting and noticed alot more pep. Will keep everyone posted. Thanks for the tip

ltrx8

Question did you say no muffler at all ...I've been leaning toward replacing cat with straight pipe with o2 fitting ,but retaining stock exhaust..Also once installed and ecu reset will cel effect power if I get one ie from pipe/o2 sensor

mikeschaefer

You guys are saying that the computer figured out that he went from having a muffler to not having a muffler? How exactly do you suppose that works?

To the originial poster: What size pipe did you use?

TeamRX8

iTrader: (25)

absolutely not, a cat-back straight pipe will not throw the computer off ... plenty of people here have run them without issue, and yes it is waaaay too loud, not even remotely civil, like circle track race car loud

yiksing

Pipe diameter too big? Looks like you are losing air stream velocity

TeamRX8

iTrader: (25)

it doesn't matter, you can remove the cat-back section completely without any issue other than dumping the hot gas where the plastic gas tanks are. I know people who just put a simple turndown right off the cat pipe end.

Brice-RX8

If it is anything like a piston engine, you need some backpressure to help create torque. If I remember correctly, when I had an SVT Focus, if you went with a too large diameter pipe for the exhaust you would kill the torque because of lack of backpressure, which I think you are doing here, could be wrong though. Don't get me wrong you want a free flowing exhaust, but I believe there is a happy medium somewhere on this.

KJ238

backpressure to create torque is only applicable at low rpms i think... higher rpms u will usually see an increase...

BTw i use a catless (pretty)straight pipe... sounds great

DailyDriver2k5

Your absolutely right, especially on smaller N/A engines, to large of a pipe and you will lose back pressure which result in a loss of torque down low, but you will scream on top end or wherever you car makes its most HP in the rpm range. Larger diameter pipe are great for turbo or twin turbo application, because your trying get the exhaust gases out as quickly as you can. On my TTZ i had 3" inch setup and saw a increase, one of the N/A Z guys added a 3" exhaust to his car and loss alot of low end pull, but gained a bit in the high end. Unfortunately his car was only good for going triple digit speeds. He went back to a 2.25" ,(stock is 1.77 or 2") and had better overall results, gained his torque back throughout the rev range and gained a few HP on the top end.

I am still learning about rotaries, but i would assume to say , not to go to much over stock with the cat-back or strait pipe.

Terrance26

I removed the muffler too it is a straight pipe for the cat back and I felt a slight increase if anything. And it is not that loud it actually sounds pretty good, everybody tells me that my exhaust sounds great. All I did was remove the muffler and I welded 4" tips on. It really sounds awesome and it is not as loud as everyone thinks. I took the pictures right before I went to work I can take better ones later. Oh and no cel. My pipe size is 2.25

mikeschaefer

I'm glad somebody understands physics.

To the original poster again:

1) What size pipe did you go with?
2) Did you dyno test your car before and after?

IZoomZoomI

TurboXS designed an exhaust with 3inch piping all the way through and netted a pretty good gain (the highest gain vs. many other exhausts in the market), with no type of loss shown on a NA rx8.

Usually you would want some exhaust velocity though by tapering to a smaller pipe size at the end.

guy321

I have a stock exhaust sitting in my storage closet. The tips may be slightly scuffed though. I'm moving, so I could be persuaded to get rid of it so I don't have take it to the new house.. but it IS kinda big and the 8 is the only car I have..

yiksing

Backpressure doesn't increase torque in any cases, backpressure is backpressure; its always bad for performance. Many people are confused about air stream velocity or power scavenging versus backpressure. Tuning an N/A machine is all about maximizing air flow all the way from intake to tail pipe, resonance tuning (sound frequency blaa blaa...). Most likely the original posters exhaust is too big losing air stream velocity. Its like blowing air across a large pipe with your mouth, you don't feel the force at the other end.