Aftermarket exhaust bhp/torque increase - fact or fiction?
Discussion
Was just having a read of the Tubi for F430 thread and it got me thinking that, aside from making a nicer noise (or not depending on your preferences it seems!), a lot of aftermarket exhaust manufacturers claim to give you increased torque and or power at varying points in rev range. Has anyone actually proof of this? "It definitely feels more powerful" is not a valid answer 
I'm thinking more along the lines of before & after rolling road figures! If so, were any other modifications made to get the increases?
I'm thinking more along the lines of before & after rolling road figures! If so, were any other modifications made to get the increases?I changed the exhaust on my 355 & 360 (not the 430 tho) tbh you do it for the noise, any increase in power is negligible.. Much of the 'it feels faster' crap is mainly placebo due to the extra noise & more 'racecar' experience..
When I was 17 I loosened the seat bolts in my alfasud, when I accelerated I got that 'pushed back' feeling.. What a tw4t I was..!!
When I was 17 I loosened the seat bolts in my alfasud, when I accelerated I got that 'pushed back' feeling.. What a tw4t I was..!!
I might do that when i am next flying the R44, should be a buzz 
On a normal car (which includes Ferrari, Lambo etc) it makes no real difference (unless the car is really strangled, which most aren't). Even if you add 5bhp, you won't notice it at all when driving.
The only caveat to this is turbocharged cars, as a simple exhaust and intake mod usually releases significant BHP and also allows freer revving.
The only caveat to this is turbocharged cars, as a simple exhaust and intake mod usually releases significant BHP and also allows freer revving.
Mario149 said:
Was just having a read of the Tubi for F430 thread and it got me thinking that, aside from making a nicer noise (or not depending on your preferences it seems!), a lot of aftermarket exhaust manufacturers claim to give you increased torque and or power at varying points in rev range. Has anyone actually proof of this? "It definitely feels more powerful" is not a valid answer I'm thinking more along the lines of before & after rolling road figures! If so, were any other modifications made to get the increases?
I changed the intake and exhaust on my NSX and it gave an extra 15bhp at the hub - as measured on the rototest dyno at TDI. Power gains were all above 5500rpm. I'm thinking more along the lines of before & after rolling road figures! If so, were any other modifications made to get the increases?Edited by NoelWatson on Friday 19th March 19:57
There are quite a few variables on what does and what won't give you any increase in power.
As a very rough guide, this may help.....
Yes - an exhaust can help increase BHP.
And as you probably guessed..... there is a " but" to all of this!
Lets all just assume we are talking about a genuine performance engine (and not a saxo or corsa or even a Rover 25 or similar).
If you were to replace just the back box - any increase (probably none) would be totally unnoticeable = But it would sound fab!!
Cat removal - Possible a very good gain to be had here. Cats strangle the engine!! remove them and it is very likely you'll feel the difference (other plus points here are weight saving and you'll also get rid of a load of heat from the engine bay).
Manifolds - often over looked, but you can squeeze a little more if your standard ones aren't any good!
Do ALL of the above and you should see an increase if it is done correctly.
But - don't forget to look at your induction / air filters. If you have spent a shed load on your exhaust, explore the possibility of fitting K&N's (or similar). It's no good being able to get rid of all the gas if the engine can't suck it up any quicker!
If you are lucky enough to have those old fashioned things called "Carbs" - try playing around with some larger jets to compliment your new exhaust and induction system tweaks.
For some older injected vehicles, if you've done the above - don't forget to check your fuel pressure, if you can adjust it - increase it to the upper tolerance, or if you know it's ok to do on your engine - wind the fuel pressure up over standard!!! (but go too far and you could bugger an injector and / or causing over fueling and introduce running concerns).
Hope this helps
Interesting my Noble has removable cats and with back to back dyno runs there was no difference in power...and that being a turbo car where it should make the most difference.
As others have said there are too many variables. I suspect that when people get big gains from removing cats, they were knackered. Putting new cats in would have had the same results.
As others have said there are too many variables. I suspect that when people get big gains from removing cats, they were knackered. Putting new cats in would have had the same results.
NoelWatson said:
Mario149 said:
Was just having a read of the Tubi for F430 thread and it got me thinking that, aside from making a nicer noise (or not depending on your preferences it seems!), a lot of aftermarket exhaust manufacturers claim to give you increased torque and or power at varying points in rev range. Has anyone actually proof of this? "It definitely feels more powerful" is not a valid answer I'm thinking more along the lines of before & after rolling road figures! If so, were any other modifications made to get the increases?
I changed the intake and exhaust on my NSX and it gave an extra 15bhp at the hub - as measured on the rototest dyno at TDI. Power gains were all above 5500rpm. I'm thinking more along the lines of before & after rolling road figures! If so, were any other modifications made to get the increases?I'm thinking of changing mine, but it's a lot of money for some welded tubing.
Well I know for a fact Tubis are dynoed and they can supply the before/after figures, and in all cases, torque and power does go up a couple of notches. They are also a few pounds lighter, which can only help.
But as said, you're hardly going to feel an extra 5bhp in a car kicking 500. Some users have reported a noticeable improvement in throttle response though, from what I've read.
Basically they're all about the noise I reckon.
But as said, you're hardly going to feel an extra 5bhp in a car kicking 500. Some users have reported a noticeable improvement in throttle response though, from what I've read.
Basically they're all about the noise I reckon.
stephen300o said:
NoelWatson said:
Mario149 said:
Was just having a read of the Tubi for F430 thread and it got me thinking that, aside from making a nicer noise (or not depending on your preferences it seems!), a lot of aftermarket exhaust manufacturers claim to give you increased torque and or power at varying points in rev range. Has anyone actually proof of this? "It definitely feels more powerful" is not a valid answer I'm thinking more along the lines of before & after rolling road figures! If so, were any other modifications made to get the increases?
I changed the intake and exhaust on my NSX and it gave an extra 15bhp at the hub - as measured on the rototest dyno at TDI. Power gains were all above 5500rpm. I'm thinking more along the lines of before & after rolling road figures! If so, were any other modifications made to get the increases?I'm thinking of changing mine, but it's a lot of money for some welded tubing.
I think the biggest difference on a modern cat car would be by putting on a high flow cat and altering the induction and engine mapping to suit the altered dynamics of air and exhaust flow. Tricky to get it right though
Paul
xx
paulqv said:
I think the biggest difference on a modern cat car would be by putting on a high flow cat and altering the induction and engine mapping to suit the altered dynamics of air and exhaust flow. Tricky to get it right though
Paul
xx
I've fitted the high flow cats but not had a chance to get it back on the dyno. Did OK at VMax but very hard to compare different days.Paul
xx
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