Lost torque with custom exhaust

[gh172]

Not very happy with my 172's performance since having a custom system and sports cat fitted last week. I have always preferred low-end torque over high-end power and was doing quite well on this front with a few minor breathing mods. I even ditched my Hillpower IK because the car was much punchier with the standard airbox.

I'm fairly sure the top-end power is better with the new system: the car revs more freely up into the 7000s (Group N ECU) and the power doesn't tail off like it used to. On the other hand, it feels weaker in the lower rev range.

I've also noticed that the 5K kick is hardly there at all now. Can't understand how that would be the case, as this is basically a mechanical property of the cams isn't it?

I've probably done about 100 miles since the system was fitted. It should be bedded in by now shouldn't it?

Cheers,
Gareth

 

[Ali]

Could be sound deceivin you...My bro's thought the same but it still showed an extra 4.6bhp gain mid range with no loss between 3 and 5k rpm.

 

[thedoc]

what bore is the exhaust?
any plans to get it remapped?

 

[gh172]

what bore is the exhaust?
any plans to get it remapped?

57mm. No plans for remap as I already paid for the group N ecu...

/G

 

[wide]

what is that in inches? if it's less than 2.5, you may well be losing power, i think that's about 2.25". it would have been better if you had bought a 67mm or 2.5"+ bore exhaust. some people on here have found they lost power not gained it with 2" after market exhausts.soz m8y

 

[Ali]

2in bore bein the pipe from cat back yeh? excuse my igorance...

 

[thedoc]

57mm is about 2.25 inches..
thought the optimum was about 67mm..
i ran about with my custom exhaust (64mm bore) for months, noticing only a small gain, then had it remapped and there was a massive difference in torque.

 

[gh172]

bought a pup then?

It's a custom powerflow - would he be able to redo it with larger bore sections but the same silencer and backbox?

 

[Ali]

Powerflow...hummm...

 

[McBunny]

70mm is a nice exhaust dia you can loose some low down torque but the top end on mine well that was fun

 

[Lagerlout]

I have custom exhaust, 2.25" bore and I can't say I've noticed a loss of torque since having it fitted, but have noticed a definite increase up high (4th gear).

I know it's less than the optional diameter for this engine but I couldn't bear it any louder than it already is!!!

 

[M.C..]

thats one of the problems of custom exhausts they just bend a few pipes and weld some boxes in there is no testing to see what the exhaust does

 

[gh172]

What's the bore of the standard pipe?