M20 B3x Naturally Aspirated Stroker build past, present and future

[hasa]

Been working on a side project for an ATI vibration damper for the M20 that's essentially plug and play, it is fairly well developed from a design point.

Any news about this?

[digger]

sounds about right for a stock 325i

[bmwmaster81]

Just because a a Lot of discussion hapened already regarding exhaaust an so on. I switched from stock 325i exhaust to custom built, with headers.....xpipe....Sport Cat.....with 2x 2inch Pipes Front to end.

It now Runs 16 sec 100 to 200 km/h and that ist 1.5 sec faster than before.

https://youtu.be/GCX0iUCoNF4

I think It must be an 15hp gain.

And I think a Stock m20b25 surely needs 25sec.

[nando]

Huh, I missed that whole post about your exhaust. Mine almost exactly matches your diagram for the 4th harmonic. I'll almost certainly move that further down next time I redo it, although I have a single exhaust and fitting the cat and 2 mufflers won't be easy that far down the line (maybe I'll just ditch the cat).

[Mr Mpower]

when i had my first exhaust done the BTB2 6-2 headers were 1-5/8" into 1-7/8" collectors and the shop just made the rear 2.25" from where the BTB collectors ended. 2.25" is more common for cats, resonators, mufflers etc so that's really the only reason it is 2.25" this was not by engineering or calculations but i didnt want to change the entire setup so left it.

really nice advise then!, thanks again!

[digger]

thats what i thought at first! thanks! is interesting how usually i see exhaust builds (with close to 0 science or investigation application) more restrictives in the final pipes but you develop the opposite (what i trust definitely), thanks for your help, this friday im going to apply this on my setup!

when i had my first exhaust done the BTB2 6-2 headers were 1-5/8" into 1-7/8" collectors and the shop just made the rear 2.25" from where the BTB collectors ended. 2.25" is more common for cats, resonators, mufflers etc so that's really the only reason it is 2.25" this was not by engineering or calculations but i didnt want to change the entire setup so left it.

[Mr Mpower]

2x2.25”

thats what i thought at first! thanks! is interesting how usually i see exhaust builds (with close to 0 science or investigation application) more restrictives in the final pipes but you develop the opposite (what i trust definitely), thanks for your help, this friday im going to apply this on my setup!

[digger]

2x2.25”

[Mr Mpower]

BTW in this picture, in the 2nd harmonic:

when you write to 2x2" at the first pipe, you are talking about 2 pipes of 2"OD i think

but when you write 2x2 25" in the final pipe, are you refering to 2 pipes of 2,25" OD or 2 pipes of 2" OD and 25" lenght ?? sorry for the silly question but i use metric system and sometimes is tricky to understand some things. Thanks again!

[digger]

late night rethinking about this setup, the m52 is 24v and m20 is 12v, the 2nd harmonic setup you’ve designed should work fine in the 24v config aswell ?

Yeah length is mostly an rpm thing so 2v 4v not a meaningful difference

[Mr Mpower]

Euro m3 headers would be better ;)

late night rethinking about this setup, the m52 is 24v and m20 is 12v, the 2nd harmonic setup you’ve designed should work fine in the 24v config aswell ?

[digger]

i was waiting for a really negative comments about the manifolds, but you are absolutely polite, hahah.

really than your time and effort in all this and waiting for more advances in your build.

Euro m3 headers would be better ;)

[Mr Mpower]

2200mm total from head for x-pipe location. since front 3 and rear 3 are different positions just take average. When you have 2200 mm length a difference of 200 mm is 10% which is not much. but if you had a system with 800mm then 200mm variance is 25% so you need to more accuarte when the system is short but not so much when its long.

i dont think there is a need to stagger cats you cant get the two (2) collectors the same anyway

X-pipe i think is just a better flowing H-pipe, but either will do the same job

i was waiting for a really negative comments about the manifolds, but you are absolutely polite, hahah.

really than your time and effort in all this and waiting for more advances in your build.

[digger]

Ok, i understand, your dedication is priceless period.

By now, the manifolds need to be OEM so this are my primaries and secondaries, giving that like you see in the picture left side is shorter than right side, i need to staggered the kats a bit to have the same leght from the primaries?
In this case where the primaries are so short, the 2200mm total lenght still being the best choice?
i have read you a few times talking really good about the s54 desing but it uses H pipe and you are using X pipe finally, wich is the main reason?

Thanks for all again, this topic must be consider as one of the best guides in the community.

2200mm total from head for x-pipe location. since front 3 and rear 3 are different positions just take average. When you have 2200 mm length a difference of 200 mm is 10% which is not much. but if you had a system with 800mm then 200mm variance is 25% so you need to more accuarte when the system is short but not so much when its long.

i dont think there is a need to stagger cats you cant get the two (2) collectors the same anyway

X-pipe i think is just a better flowing H-pipe, but either will do the same job

[Mr Mpower]

s54 as in configuration not sizes (diameters)

i favour around 1600 mm give or take with a street engine. This is in effect a total length of 2200 mm when primary (assume 600 mm) is accounted. If you use longer primary then retain total length 2200 and shorter the collector a bit and vice versa. E.g. with long tube headers which are like 800mm often then 1400mm will work ok to.

twin 2" is plenty unless its a crappy workmanship i.e. bad bends, misalignment, mismatch etc. A really nice twin 1.875" or 1.75" would also work but need to pay a bit more attention to the details include the muffler, cats, resonator sizes and efficiencies

Ok, i understand, your dedication is priceless period.

By now, the manifolds need to be OEM so this are my primaries and secondaries, giving that like you see in the picture left side is shorter than right side, i need to staggered the kats a bit to have the same leght from the primaries?
In this case where the primaries are so short, the 2200mm total lenght still being the best choice?
i have read you a few times talking really good about the s54 desing but it uses H pipe and you are using X pipe finally, wich is the main reason?

Thanks for all again, this topic must be consider as one of the best guides in the community.