exhaust mod hp #'s?

[bmwfan2304]

i was just curious how much hp increase i could expect from doing an exhaust upgrade on my 535i... i plan on making it with my very talented welding friend, we plan on using 3" stainless steel and a 3" glass pack and high flow cat... it won't be anywhere near noise legal but i don't really care. the reason im going as big as 3" is because i plan on going turbo after i take the time to change my valve seals. Anyway, just curious as to what i should expect in terms of power, my compression is great despite the valve seals.

thanks, bryan

[Raj]

You might gain a little hp up top, but will likely lose a considerable amount of torque with a 3" exhaust on a stock m30.

[Guest]

Don't expect much if any increase in HP, but expect a lot of NOISE. You have a stereo in the car ?? If you do the exhaust mod your contemplating you'll have a nice location for a gauge panel, where the Head Unit was located.

IMO Raj is correct about possible HP gains. Maybe, a little something at the top end but you'll destroy the drivability. To maintain some drivability will involve some sort of fuel system tinkering to get the A/F Ratio within the ECU's operating range. If you do the exhaust plan on buying some sort of adjustable FPR, about $250 for a decent one like Cartech manufactures.

IMO, you'd be better off spending the time/$$$s to get the engine ready for the turbo upgrade. Once you have the engine running perfectly in NA mode, TCD's turbo upgrade is pretty close to plug-n-play. If your turbo upgrade is more homebrew like Tj's, then having a well tuned/running NA engine will only help you out.

Rich

[bmwfan2304]

[QUOTE="Rich Euro M5"]Don't expect much if any increase in HP, but expect a lot of NOISE. You have a stereo in the car ?? If you do the exhaust mod your contemplating you'll have a nice location for a gauge panel, where the Head Unit was located.

IMO Raj is correct about possible HP gains. Maybe, a little something at the top end but you'll destroy the drivability. To maintain some drivability will involve some sort of fuel system tinkering to get the A/F Ratio within the ECU's operating range. If you do the exhaust plan on buying some sort of adjustable FPR, about $250 for a decent one like Cartech manufactures.

IMO, you'd be better off spending the time/$$$s to get the engine ready for the turbo upgrade. Once you have the engine running perfectly in NA mode, TCD's turbo upgrade is pretty close to plug-n-play. If your turbo upgrade is more homebrew like Tj's, then having a well tuned/running NA engine will only help you out.

Rich[/QUOTE]

i guess that makes sense then... we are going to do the seals here soon, other than that it runs smooth, has good power, compression #'s are all good, it even idles smoothly. im either going to do a TCD s-2 kit (if i can afford one) or go with a s-2 custom turbo from a local shop that's done a few m30 powered cars. that would be a couple grand less. but if it's going to change the drivability i'll wait untill i do the turbo for this.

what other NA mods could i do that would increase my hp by a little?? i already have a 14.1lb flywheel, but other than that it's all stock, im in the mood for a little extra power to play with lately and can't wait for the turbo...

[Guest]

what other NA mods could i do that would increase my hp by a little??

If you don't have a chip this will help, also consider a ratio change for the differential.

Rich

[bmwfan2304]

what other NA mods could i do that would increase my hp by a little??

If you don't have a chip this will help, also consider a ratio change for the differential.

Rich

If you don't have a chip this will help, also consider a ratio change for the differential.

Rich

the only thing is im not sure if id be willing to lose the tourqe... how much tourqe would i be looking at losing?

[pdx 528e]

[QUOTE="bmwfan2304"]

If you don't have a chip this will help, also consider a ratio change for the differential.

Rich

the only thing is im not sure if id be willing to lose the tourqe... how much tourqe would i be looking at losing?[/QUOTE]

Basically, an exhaust that big moves the torque you DO have higher up the rev range, and since Horsepower is a function of Torque at a given engine speed you make more power, but its not available down low where its good for daily in town driving. I've never seen any dyno information regarding this though.



[Edit by pdx 528e on [TIME]1115912059[/TIME]]

[bmwfan2304]

Basically ane exhaust that big moves the torque you DO have higher up the rev range, and since Horsepower is a function of Torque at a given engine speed you make more power, but its not available down low where its good for daily in town driving. I've never seen any dyno information regarding this though.

[/QUOTE]

ahh i see... that makes sense... so launching wouldn't be as effective then? or since the engine is already revved would it still be able to effectively launch? as far as e28 go Anyway. also, i don't care if i loose power when im not on the throttle fully... that way i won't use as much fuel... but would the exhaust change how smoothly my engine runs by messing with AFR's and all that crap? i don't know too much about tuning... so thanks for the help... it runs perfectly smooth now, but i run it with 94 octane fuel too...

[Shawn D.]

[QUOTE="bmwfan2304"]also, i don't care if i loose power when im not on the throttle fully... that way i won't use as much fuel... [/QUOTE]
That's flawed logic. If maintaining X speed requires Y throttle position, and you lose power via some mod, you will require Y+ throttle to regain the power needed to maintain X speed. Whether or not you increase or decrease efficiency by doing this is an open question. You'll get reduced pumping losses via the increased throttle setting, but will have to be on the throttle more.

[bmwfan2304]

[QUOTE="bmwfan2304"]also, i don't care if i loose power when im not on the throttle fully... that way i won't use as much fuel... [/QUOTE]

[QUOTE="Shawn D."]That's flawed logic. If maintaining X speed requires Y throttle position, and you lose power via some mod, you will require Y+ throttle to regain the power needed to maintain X speed. Whether or not you increase or decrease efficiency by doing this is an open question. You'll get reduced pumping losses via the increased throttle setting, but will have to be on the throttle more.[/QUOTE]

AHHH! im so frustrated... that makes sense too... and it's all common sense, i've pretty much run out of that this week... finals week and im graduating from high school so im pretty much brain dead! lol. Anyway, it seems like it wouldn't bother me much, and id probably drive more efficiently is what i was getting at, although i realize that's not what i said... lol

[Tjn182]

I would wait until you have your turbo system first. Otherwise you'll have to weld/mate up your turbo downpipe to your existing exhaust setup, I would just wait and have it built specifically to your turbo setup.