What's your cam and why?

[Fidhle007]

I'd like to hear from those of you with aftermarket cams, a recent incident has led me to a head rebuild and I'm thinking that as long as I have to take the cam out, I might as well put something more fun back in. I was already running a MarkD 93 Octane chip, CAI (Bav) w/ Lucas Motors heatshield, and custom exhaust (similar to Dinan in flow characteristics I think) but when it goes back together I'll be upping to 19# injectors and possibly headers and a larger AFM. 272 regrinds or IE new billets are cheap but I'm very tempted to go bigger. My biggest fear with a 272 is that if I'll either wish I went bigger than or stayed stock because I won't feel that much of an improvement. My fear with going with a 284 or 288 Schrick is that I'll like it but want more low end, which will lead to a pricey stroker build down the road. Just musing for now, let me know what you're running and why, and why you like, or don't like your setup.

Thanks!
Brendan

[nando]

forget about the myth of losing all your low end with a cam - a 284/272 will gain low end torque, a 288 will be about even with stock and way more up top. if you lose anything at all, you aren't likely to notice. it's not going to turn your car into a peaky 4 cylinder or something.

also, unless your chip is designed for it, forget about the larger AFM as well - they're far more trouble than they are worth.

[lovemy318]

anybody looking for some cheap b25 turbo parts? free mani' if picked up!

[Fidhle007]

anybody looking for some cheap b25 turbo parts? free mani' if picked up!

Get the fuck out of my thread, n00b. :hitler:

It's your loss that you didn't want any of the turbo parts we were trying to give away. I had some sweet shit but Atomic has taken it all now.

[Fidhle007]

forget about the myth of losing all your low end with a cam - a 284/272 will gain low end torque, a 288 will be about even with stock and way more up top. if you lose anything at all, you aren't likely to notice. it's not going to turn your car into a peaky 4 cylinder or something.

also, unless your chip is designed for it, forget about the larger AFM as well - they're far more trouble than they are worth.

That's good to know. I'd just get the MarkD chip for 17/19lb injectors and hope for the best. I have the stock injector chip in now and love it so I figure if I get the other one I'll love it just as much AND I'll finally be able to put those injectors to use that have been collecting dust on my desk for a year. And for what it's worth, I don't think my car had any low end anyway but I'm not sure if that was the chip or the 20lb wheels. I ran a 15.5 in the 1/4 though.

Looking at Turner's site (my shop deals with them a lot because they're pretty local) it seems like they're my best bet for getting a Schrick cam and the 288 just sounds like the most fun. The next question though is are stiffer springs absolutely required or will new stockers suffice? My wallet is starting to hurt the more I think about this little project.

[digger]

forget about the myth of losing all your low end with a cam - a 284/272 will gain low end torque, a 288 will be about even with stock and way more up top. if you lose anything at all, you aren't likely to notice. it's not going to turn your car into a peaky 4 cylinder or something.

also, unless your chip is designed for it, forget about the larger AFM as well - they're far more trouble than they are worth.

Its not myth; it just depends on what cam you use and also the header........... When you rebuild a head this can often bring back performance lost that might negate some bad effects so it’s a good idea to do this also a slight raise in compression from flattening the head surface won't hurt.

Anyone expecting to gain power everywhere from a cam should do some in-depth research into camshaft theory because unless you have a really poor cam to start with (BMW's aren’t poor) it won't happen. If you want to gain top end and midrange be prepared to sacrifice some bottom end that is the fundamentals of the airflow dynamics.

For a 2.7/2.8 a schrick 284/272 is a very torquey cam and would very work well it will make ~85% peak torque at 2500rpm but won’t be a huge top end screamer. A catcam 273 would be another option which is what the UK guys are leaning towards nowadays.

For a 2.5L for streetability i'd be looking at a schrick 272 or catcam 264 (i should point out that catcam use a different method for quoting their advertised duration so that’s why they look smaller but are more aggressive than the duration numbers suggest so don't be fooled). Don't use a Schrick 288 unless you want it to be gutless below 4500rpm the bottom end is not designed to use this cam

I use MM 286/272 (advertised duration) with 11.75mm/11.75mm (lift) 116LSA (lobe separation angle) 1mm lift at TDC (1mm lift during overlap) with at m20B31 bottom end.

This cam is not very torquey at all and works best 4k to 6k, at 2500 it makes ~70% peak torque at 2500rpm and 210whp (this compares to 90% for a 3LM20 with 272schrick but "only" 187whp). It uses a wide LSA so that overlap is low. The low overlap makes for good emissions and idle but possibly some loss of midrange/top end results because exhaust scavenging is limited. This cam relies on inertia filling by closing the intake valve very late in the compression stroke to make good top end (210whp dyno dynamics) at the expense of low end and midrange because dynamic compression is reduced. This cam needs much higher compression than 10.5-11:1 IMO to work more effectively. The MM 286/272 is not even remotely similar to the schrick 284/272 in terms of the way it works but the advertised durations look similar.

The more traditional method by schrick and Dbilas is to use tighter LSA with more duration and this creates alot of overlap which helps scavenging and degrades idle and emissions but tends to narrow the operating region of the cam. These cams don’t have overly large lift.

I am looking at an alternative cam perhaps a catcam283 and the idea is to sacrificing idle and emissions for more midrange if things go to plan.

Hope this helps

[atomic]

Get the fuck out of my thread, n00b. :hitler:

It's your loss that you didn't want any of the turbo parts we were trying to give away. I had some sweet shit but Atomic has taken it all now.

A bit OT but thanks again for the free stuff Fidhle007 and even paying for half of the shipping too... AWESOME DEAL !!


carry on.....

[Fidhle007]

I've had a really hard time finding CatCams so I think I'm stuck with Schrick or IE. Bang for the buck is a consideration as well as timeframe. I snapped a rocker arm so I'm building a new head to swap over to get back on the road asap. I'm sending the head to the machine shop this weekend or early next week so it can be ready to assemble when I get back from vacation on the 1st.

My worry about going with a 272 (Schrick or IE) is that I won't really feel as much improvement as I'm hoping for and I'll wish I just went with a stock rebuild and saved my pennies. My old head had between 155 and 160psi across the board so it seems like it was pretty healthy. I plan to have the replacement head decked as much as possible but I doubt I'll gain that much compression really.

So for argument sake let's ask this: IE 272 or Schrick 284? This is still a hypothetical for now though...

[digger]

I've had a really hard time finding CatCams so I think I'm stuck with Schrick or IE. Bang for the buck is a consideration as well as timeframe. I snapped a rocker arm so I'm building a new head to swap over to get back on the road asap. I'm sending the head to the machine shop this weekend or early next week so it can be ready to assemble when I get back from vacation on the 1st.

My worry about going with a 272 (Schrick or IE) is that I won't really feel as much improvement as I'm hoping for and I'll wish I just went with a stock rebuild and saved my pennies. My old head had between 155 and 160psi across the board so it seems like it was pretty healthy. I plan to have the replacement head decked as much as possible but I doubt I'll gain that much compression really.

So for argument sake let's ask this: IE 272 or Schrick 284? This is still a hypothetical for now though...

I wouldn't go with the IE272 without seeing some decent specs on it which you might find hard to obtain.

Here is a plot of 325i with schrick 284/272, headers and BBTB and standard bottom end. The higher graph is the same but with MAF conversion and ITG airfilter. Unfortunely there is no 100% stock run. The graph is from UK so they convert to bhp using coastdown losses but you get an idea of the torque delivery atleast.