Does lightly modifying the exhaust on an EVOVIII make the car lose torque in a certian part of the rev range compared to the stock exhaust? Im asking this becuase Akihiko Nakaya of Best Motoring drove a lightly modded EVO 5 around tsukuba in the "Impreza vs Evolution final battle" video, and he said that "The exhaust system of this car has been modified a bit, so the torque around 4000 to 5000 rpm is lost. The nature of a 4WD is to have some power around that area but unfortunatley it's lost. I think the Lancer EVO and Imprezas don't need to be tampered with so much."

Can anyone go into detail as to why this happens?

The mods on the EVO5 GSR were:

Tanabe Hyper medalion exhaust
Olhins Suspension Kit F8kg R7kg
K&N Air Cleaner
Rigid suction pipe
Front pipe (mfr unknown)

 

you have to keep in mind that the wrx engine is much different than ours. the torque loss could be due to their boxer engine style where they have a downpipe and a midpipe and lots of cats inbetween. lightly modding may only mean chaning out midpipe or downpipe or just freeing up catback... in any case the more exhaust gas velocity you maintain the more torque you will get earlier on, but this stifles top end power... so it's a matter of waht your goal is, and what you want out of your car for what purpose. if you're goin' nuts... bigger is the best.

 

Uh dude he was talkin about an Evo not a WRX

Reason for losing some of the torque is you don't have the backpressure and the turbo spools slower making the power band a little bit higher great for upper range hp and torque but just takes a little longer to get into the power.

 

i gained 20+trq dyno proven when they installed my tbe-thats with the stock cat.

 

you gain hp and torque but usually at higher RPM

 

hmmm, i didnt notice that. let me find my dyno sheets

 

I thought the loss of low-end torque applied to NA cars, not turbo ones...you want a less-restrictive exhaust so the turbo spools faster, right???

 

my torque went up throughout the rpm band..MUCH more noticeable in the mid-to-upper gear.

You do lose tq but not much.

I was dynoed with 305 tq no tbe and i believe at 23 psi
I was dynoed with 302 tq with TBE at around 22 psi

so while you may lose peak tq, you gain gobs of tq in the power band. food for thought.

 

Yup...it's the area under the curve, not just the peak #, that makes the difference!

 

yeh, that's odd. around 4 to 5k RPM is where all the power happens for us. Then it tapers off as the rpm climbs.

Maybe modification on exhaust and intake will give your more down torque then up high.

It still don't make any sense. Track driving on high RPM (I have that video of the track racing) and tapering it down to 4 to 5k RPM could of resulted in lost of boost.

Maybe that's what he's talking about. They drove on that track and kept it at above 6000rpm to redline. Only time they came down that low was when they were curving.

 

That's stock...DynoFlash fixes that problem...pulls hard all the way up now!

 

^yeh, off topic. I'm very happy for you.

 

oops... but what i said still applies.