OEM Exhaust mod versus bypass pipe?

[Anonymous]

Hi folks,

I'm about to buy a set of back boxes with the intention of doing the OEM Exhaust mod. However, I'd also read info on the bypass pipes...

Is there any info comparing the two, or has any ///M owner done the bypass pipes and has a video?

Many thanks,

James

 

[Fishy Dave]

Hi James,

I've had the bypass pipes added and at first i was pleased, but now i wish I'd saved the time and money and just gone for uprated back boxes such as Stromung or gutted boxes by 'Ducklakeview'. I would say the bypass pipes have added 10% extra noise if that, still, there is no drone at least. I'm not sure a video would really pick up any real differences in sound, except perhaps when cold (and I'm gentle on the throttle then anyway)?

 

[Mangozac]

In the new year I'm going to be fitting exhaust actuators teeing off just before the mufflers and directing exhaust gases straight down. So with the actuators closed I'll have standard, stock exhaust. With them open it will effectively be straight pipes!

I've scored a couple of the actuators used on 340i and M3 exhausts and will be using them.

 

[ShaunKC]

Hi Jad,

When I bought my car it had the exhaust bypass mod; I wouldn't have personally done this and planned to revert back to original. However, I just can't bring myself to do it! The sound is a nice burble at idle and plenty of noise when you put your foot down; there is no drone, and I can't imagine you would want it any louder, although I do also have an eventuri intake so that obviously helps. The best bit is that it can be easily changed back if you don't like it, or if you want to sell the car and the new owner wants it back to standard (like I did!)

If you are ever in West Yorkshire, you are more than welcome to come and have a listen.

 

[Fishy Dave]

Hi Jad,

When I bought my car it had the exhaust bypass mod; I wouldn't have personally done this and planned to revert back to original. However, I just can't bring myself to do it! The sound is a nice burble at idle and plenty of noise when you put your foot down; there is no drone, and I can't imagine you would want it any louder, although I do also have an eventuri intake so that obviously helps. The best bit is that it can be easily changed back if you don't like it, or if you want to sell the car and the new owner wants it back to standard (like I did!)

If you are ever in West Yorkshire, you are more than welcome to come and have a listen.

Not sure if we are talking about different modifications? Do you have the small 3/4" stainless pipes that travel above the backboxes and rejoin by the tail pipes?

 

[ShaunKC]

Hi Jad,

When I bought my car it had the exhaust bypass mod; I wouldn't have personally done this and planned to revert back to original. However, I just can't bring myself to do it! The sound is a nice burble at idle and plenty of noise when you put your foot down; there is no drone, and I can't imagine you would want it any louder, although I do also have an eventuri intake so that obviously helps. The best bit is that it can be easily changed back if you don't like it, or if you want to sell the car and the new owner wants it back to standard (like I did!)

If you are ever in West Yorkshire, you are more than welcome to come and have a listen.

Not sure if we are talking about different modifications? Do you have the small 3/4" stainless pipes that travel above the backboxes and rejoin by the tail pipes?

Yes that's what I have, is this not what you are talking about?

 

[Fishy Dave]

It is, I was just wondering why we have found the sound so different? I'd have thought in my Roadster it would be louder if anything, interesting. Would be good to compare at some stage.

 

[goldbcfc]

My first e85 had back box chopped off and stainless pipes form the cats,sounded great on track days but for general 30mph routes did my head in with all the pops and bangs. My second e85 had cats removed and stainless "powerflow" brand backobx added it sounded a bit better but generally the same still. My 3rd has a normal oem exhaust sounds just right when you go over 3000rpm it gets loud just right

My first was down on power when dyno'd so the exhaust mod may have affected that.

 

[ShaunKC]

Yes I would have thought the roadster would be loud enough with just canvas between you and the exhaust! As I mentioned the last owner did the mod, so I don't know exactly which pipes he used, but the sound is really nice, and certainly loud enough. We will have to do a compare sometime.

 

[MrPT]

Did we ever get an answer to "what's the difference between the bypass pipes mod and cutting some holes before the backbox"? There's high pressure (higher than atmospheric, anyway) through the exhaust tips - is that going to increase bypass flow or impede it?

Just seems silly to add more weight to an already heavy exhaust otherwise.

 

[srhutch]

The cutting open of the silencer has a few incarnations so are not all the same. I've tried to trace where mine came from to establish what exactly has been done to it. No success though :x

 

[BMWZ4MC]

I had bypass pipes on my S2000 back boxes and it brought the car to life but looked entirely OEM. I'd expect similar benefits with the Zed. I fitted Remus back boxes to my Zed in part to improve the sound and in part because I didn't like the silver scrotums hanging beneath the rear bumper with the OEM exhaust

 

[nige bcs]

...just buy a set of my pipes - job done :-D