RPM 7000+ How?

[ForcedFirebird]

Stock i motor revving past 7k is like the eta revving past 5k - what's the point?

If you want to rev that high just for sounds, remove limiter and wait for the fuse to finish burning - if you want to make power doing so, you will need to tune all the hardware to match a power-band that high using recommended procedures located above this post.

Matching the flow characteristics of your ports to your cam and balancing the rotating assembly is the common practice of a high-revving motor.

[nando]

i replaced the CPS in a friends car, with an apparently defective unit. because her e30 will now rev past the 6700rpm. im sure its not the engine. i think its just the signal to the tach being fucked up.

nothing else was changed or modified.

so yes, a "bad" cps will give you a fubared tach reading.

The RPM reading comes from the 60-2 tooth pattern on the crank damper wheel. The sensor basically can read it or it can't (a bad sensor will lead to tach drops, power cut, etc). It's not possible for it to output a "too fast" reading, and the tach doesn't get it's RPM signal from the CPS anyway (at least not directly).

[Kershaw]

dude, i dont know what to tell you.

i thought the CPS was bad, so i replaced it, and now the tach will go past the redline. didnt fix the issue she had. that ended up being the cap and rotor. but her original CPS came apart during removal so i cant put it back in.

anyway, if you dont believe me... you are welcome to come drive her e30 and see for yourself. and feel free to bring a good CPS and watch the problem disappear.

:P

[nando]

no, I don't believe you. I know how it works, what you're saying isn't possible.

[AnimalE30]

I bought a 325i that has an upgraded chip in it (stamped ST on it) dont know what it is. Yeah that thing pulled hard past 7000, now I'm replacing a rocker arm : /

[Wh33lhop]

I bought a 325i that has an upgraded chip in it (stamped ST on it) dont know what it is. Yeah that thing pulled hard past 7000, now I'm replacing a rocker arm : /

I doubt a stock M20 would pull hard past 7k no matter what chip you gave it.

[SpecM]

I doubt a stock M20 would pull hard past 7k no matter what chip you gave it.

maybe in 1st gear

[lennon]

But it would still pull less hard at 7k rpm in 1st than at like 5.5k rpm in 1st ;)

[rpob5t]

I had a whole bunch of work in an M20 (header, schrick 284 cam, miller MAF kit IE rockers, headers and exhaust) can't say I really noticed a major difference in power (it was all over 4.5k and torque below that was lost) but rining it to 7k wasn't a major issue. Being that I blew that motor up (valve broke on track, shattered the piston and it went south from there) I might be a little biased but I felt it was a definately NOT worth the money out laid; it was cash that would have been much better spent on a 24v swap or just general maintence and more driving schools.

[StereoInstaller1]

I had a whole bunch of work in an M20 (header, schrick 284 cam, miller MAF kit IE rockers, headers and exhaust) can't say I really noticed a major difference in power (it was all over 4.5k and torque below that was lost) but rining it to 7k wasn't a major issue. Being that I blew that motor up (valve broke on track, shattered the piston and it went south from there) I might be a little biased but I felt it was a definately NOT worth the money out laid; it was cash that would have been much better spent on a 24v swap or just general maintence and more driving schools.

Quoted For the motherfucking Truth!

If you want power out of an M20, apply boost.

If you want high RPM, do a different motor.

[nando]

I had a whole bunch of work in an M20 (header, schrick 284 cam, miller MAF kit IE rockers, headers and exhaust) can't say I really noticed a major difference in power (it was all over 4.5k and torque below that was lost) but rining it to 7k wasn't a major issue. Being that I blew that motor up (valve broke on track, shattered the piston and it went south from there) I might be a little biased but I felt it was a definately NOT worth the money out laid; it was cash that would have been much better spent on a 24v swap or just general maintence and more driving schools.

so you had a bunch of random parts put together on a stock bottom end and you were disappointed? no surprise there. ebay headers ( IE are the same thing)? junk. MAF conversion? it's not a panacea. how about solid headwork? compression ratio (static and dynamic)? the rest of the exhaust? intake? there's a lot more peices of the puzzle than sticking a big cam and shiny headers on and expecting huge gains.

[rpob5t]

so you had a bunch of random parts put together on a stock bottom end and you were disappointed? no surprise there. ebay headers ( IE are the same thing)? junk. MAF conversion? it's not a panacea. how about solid headwork? compression ratio (static and dynamic)? the rest of the exhaust? intake? there's a lot more peices of the puzzle than sticking a big cam and shiny headers on and expecting huge gains.

You missed the point; how much would you have to spend on head work, custom pistons / stoker kit and the like just to get the motor to 200hp (easily into the $2-3k)? What I spent on the cam, valve springs, and rockers for the M20 is basically what I bought a complete M52 for and it already has 200hp, and I won't spend another $2k getting it into the car (and its going to be a bunch more reliable).

To be honest I wasn't expecting huge gains to begin with, I'm quite realistic with my expectations with a stock head and intake (good KP motors make about 180-ish hp, which component wise is basically what I had) its just the gain's vs what I spent was no where near worth the cash spent. The other caveat is that I feel that the reliabilty of the M20 goes way down when you start breathing on it. While you may not notice this as much on a DD/street racer setup; my car was purchased soely for track/auto-x use and it simply didn't hold up once I started changing parts; with the motor letting go on track as the coup de grace. My personal opinion (objections are welcome) with the M20 is keep it stock or if power is your aim get it the heck out of there...

[nando]

You missed the point; how much would you have to spend on head work, custom pistons / stoker kit and the like just to get the motor to 200hp (easily into the $2-3k)? What I spent on the cam, valve springs, and rockers for the M20 is basically what I bought a complete M52 for and it already has 200hp, and I won't spend another $2k getting it into the car (and its going to be a bunch more reliable).

To be honest I wasn't expecting huge gains to begin with, I'm quite realistic with my expectations with a stock head and intake (good KP motors make about 180-ish hp, which component wise is basically what I had) its just the gain's vs what I spent was no where near worth the cash spent. The other caveat is that I feel that the reliabilty of the M20 goes way down when you start breathing on it. While you may not notice this as much on a DD/street racer setup; my car was purchased soely for track/auto-x use and it simply didn't hold up once I started changing parts; with the motor letting go on track as the coup de grace. My personal opinion (objections are welcome) with the M20 is keep it stock or if power is your aim get it the heck out of there...

actually, you missed mine. My point was you can't expect to slap a bunch of expensive parts together and gain something. You can spend a lot of money and end up with nothing. Just look at Dave Length's 3 liter stroker as a great example.

also, last I checked the original question wasn't "does it make sense from a cost/benefit approach to modify an M20". the answer on this forum is always going to be "no, put a $500 junkyard motor in your car!".

[rpob5t]

I'm not trying to start a war here (I think we're looking at this from 2 different view points) so please don't take this post that way; but I wouldn't call what I did here a slapped together setup; as stated my E30 was purchased with track use in mind; the plan was and still is to eventually take the car racing I was looking at BMWCCA prepared rules (KP is a decent play ground for E30's) which basically limit you to the mods I had on the car, so I picked out the parts I put on the motor with these limitations in mind not just cobbled something together. Also I never said there weren't gains; there were just nothing at an RPM point that the average person on this forum would ever find useful; at a track secnario where minimum engine speeds are about 3.5-4k the cam did wake up the motor (at the cost of torque below that point) so for someone that doesn't use there car in these scenarios its not really a good idea to spend there.

but to get back on topic you can rev the M20 to 7k with a cam, valve springs and chip but don't expect the vavle train to be very stable at those speeds (heck M/S50/52's have stability issues over 6800) so sustained RPM is going to break parts (OE rockers 1st) so I'd turn the rev's down and just try not to money shift the car; if you really want to rev the piss out of your motor research an S54 or Euro S50 swap they have the valve train to handle that type of sustained RPM levels

[MonkeyMadness]

Just got my Miller WAR chip/maf hooked up and took a test drive to mc-d's
and the had the rev limit up to 7000 and it pulled and drove awsome..
Not going to push it till the motor 100% sorted out, but soo far WOW
love the damn thing!..