288/280 vs 280/272 cams.

[digger]

Strange: I have a factory modified head from BMW Motorsport at home (from the original P54B32) and BMW ported the combustion chambers, the valve seats as well as the intake side. Exhaust was not touched. Wondering if I should get that done beofre installing...

that’s probably because the exhaust side is not as important . The focus should always be the inlet side as in getting more air in to enable you to burn more fuel is the goal. It’s harder to get it in as the pressure differentials are much lower by orders of magnitude.

You do need a certain amount of exhaust time area (flow and cam duration) to exhaust appropriately for the power level, but you aren’t trying to maximise the exhaust flow at all as then you end up with too big, slow velocities and poor wave tuning. Too much exhaust flow capability (i.e. size) hurts torque. The balance point is not as much exhaust flow as people think like 60-80% of the inlet can work depending on the cam split and overwhelmingly the trend in top motoropsort is small effcinent exhaust systems and a 4V engine is rarely short of exhaust flow.

Head numbers at ~12mm/0.500” for stock S50b32 are 260/220 85% and s54b32 260/200 77% so the exhaust is not under done on S54 but is overdone on S50b32 and BMW were happy having less exhaust flow on the more modern engine, go figure as they made an extra 39hp with such a configuration. some of the earlier stuff ion 80's had exhaust the same as inlet so a defintive trend can be observed even in OEM.

Stock valve size numbers on the inlet can get to 280 cfm @ 28”, if you have those numbers a mild increase on exhaust is worthwhile but that probably doesn’t require much port work maybe just the valve seats, SSR and bowls with the main part of the port probably untouched as thats not where the flow restricton is anyway. Flow retsrction is where the bend is and most complex geometry

So to answer your question find a head specialist get them to put the head on the flow bench and evaluate it for your application. if they are any good they will look at flow but also velocity and bunch of other things. Most of the porting services for the S54 leave a alot to be desired so dont be going to the name brand ones.

[Altaran]

Don’t really know definitively, but I’ve heard it said many times that there’s some room for improvement on the exhaust side but not much to be gained on the intake
side.

Strange: I have a factory modified head from BMW Motorsport at home (from the original P54B32) and BMW ported the combustion chambers, the valve seats as well as the intake side. Exhaust was not touched. Wondering if I should get that done beofre installing...

[duracellttu]

Thoughts on whether there is any value in head porting with a CSL airbox and 288/280s or even 280/272s?

I had the exhaust side ported on my head when my head was being built with 288/280 cams. (I also have a full SS exhaust with 2.5" sec 1 & 2.) The results were seen in my dyno graph, to which Andrew Lang and Paul Claudes both noticed. At ~6300 rpms my HP slope took a sharp curve upwards. I considered porting the intake side, but didn't because I kept the stock TBs. With a CSL intake you are already getting a lot more air flow to the engine. You might not see the difference with porting the intake unless you also did Dinan TBs, where you could match the new TB diameter. Or if you built the engine out and went with 14mm lift cams, to take advantage of the additional available air.

[stash1]

This is true, i have them in my motor. I paid around 45 euro per follower from Leebmann.

Sooo, about $40 cheaper per follower? That’s significant!

Edit: Nvmd, see the Schricks are available for around $70 ea, sooo...about a $20 savings per follower. Still pretty significant when you factor that you need 24.

[Obioban]

Thoughts on whether there is any value in head porting with a CSL airbox and 288/280s or even 280/272s?

Don’t really know definitively, but I’ve heard it said many times that there’s some room for improvement on the exhaust side but not much to be gained on the intake
side.

[bigjae46]

I think the 280/272s are a better choice for cars that see any street use.
-Better power below ~7800 rpm
-can reuse stock followers, which makes install much easier (and cheaper)
-smoother idle

I wouldn't be tempted by the 288/280 setup unless I was doing an increase compression ratio and/or stroker and/or high revving (8700+ rpm) build. For a "normal" (full exhaust, CSL intake, etc) bolt on build, 280/272 is the way to go IMO.

Thoughts on whether there is any value in head porting with a CSL airbox and 288/280s or even 280/272s?

[BMWahba]

interesting find...

[Martyn]

Ehhh, can anyone else confirm this, and what does pricing look like?

This is true, i have them in my motor. I paid around 45 euro per follower from Leebmann.

[stash1]

There is also an alternative to Schrick followers: E90 320is stock followers. Same design as S54, just coated from the factory. Seems BMW learned from something....
These used to be quite cheap by comparison, but recently they have increase the price.

Ehhh, can anyone else confirm this, and what does pricing look like?

[Altaran]

Hey all, I'm kinda new to the cam world (it's teased me ever since I saw the group buy on the old forum)... I daily my car, so I'd like to go with 280/272- do I need to just buy cams and throw them in? Or are there any other parts I need to buy with 280/272s? I suppose tune as well.

Thanks guys. Some awesome information and knowledgeable guys on this thread.

There was a discussion on the first page of this thread on that. Personally I would always exchange the followers. Even though cams only rotate half the speed of the crank, it is still 4k rpm with these cars and I would not put anything in less than perfect state on it.

There is also an alternative to Schrick followers: E90 320is stock followers. Same design as S54, just coated from the factory. Seems BMW learned from something....
These used to be quite cheap by comparison, but recently they have increase the price.

[EzM3]

Hey all, I'm kinda new to the cam world (it's teased me ever since I saw the group buy on the old forum)... I daily my car, so I'd like to go with 280/272- do I need to just buy cams and throw them in? Or are there any other parts I need to buy with 280/272s? I suppose tune as well.

Thanks guys. Some awesome information and knowledgeable guys on this thread.

[duracellttu]

What power did you get in the end mate ?

Just created a separate thread with my build details and results. See below...

https://nam3forum.com/forums/forum/m...w-dyno-results

[duracellttu]

Interestingly enough on one of the other forums I was on a guy who had a genuine CSL said occasionally he found little blips with it but never with the stock maf version when he had the regular m3

Oh wow, that's new information. Maybe this isn't a much of an issue as it seems.

[digger]

Interestingly enough on one of the other forums I was on a guy who had a genuine CSL said occasionally he found little blips with it but never with the stock maf version when he had the regular m3

[NZ_M3]

I was under the impression that the "CSL hesitation" was something that only happened to MAP-less alpha-n setups? Or maybe I'm conflating two different problems. Is this something that happens on real CSLs?

I have done so many CSL airbox conversions here in NZ for others and I have never ever had a case of the so called hesitation.

I even made a video for someone in the States privately of my CSL trying to replicate the so called hesitation at various gears from 3000rpm and have not been able to replicate it at all.

i have however managed to replicate it via an Alpha N tune I received from the UK so I do know what it is and what it feels like.

A correctly converted car with a healthy engine just doesn’t have this issue. Period.

I have had my converted M3 with the csl airbox also for just over 3 years now and it has 189k km and I have not been able to replicate this issue either with it.