RPM 7000+ How?

[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.

[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 : /

[nando]

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

[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]

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).

[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.

[Kershaw]

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.

[nando]

what I meant was, a "bad" CPS isn't going to read the wrong RPM. it wouldn't read anything at all..

[Kershaw]

haha, thats why i said the tach goes over 9000. i never said the engine. :D

[nando]

put a bad CPS in there, your tach will go to over 9000!!!

:pimp:

I know you're joking, but uhm.. it doesn't work that way.

[Kershaw]

Whats it take to for a M20 to Rev above 7000

put a bad CPS in there, your tach will go to over 9000!!!

:pimp:

[MonkeyMadness]

You'll want a cam that can make power up there, and you'll need supporting mods - headwork, valve springs, rockers, exhaust, intake, etc. So basically a motor that's built from the ground up for a specific powerband. It's not a matter of removing the redline on a stock motor. It would probably do it, but you won't make any power with a stock cam, there wouldn't be any point.

I set my limiter to 7500, mostly to avoid an early shift at an autox. power is good until about ~7300. You want to shift when the power you're making at high RPM is equal to your next shift point, which is another reason for where I have it. Previously it was 7200, but it was still pulling when I hit fuel cut so that was a little too early.

also, why do you want to rev that high? you can design a powerband for a 7k redline and be fine. Keep in mind what gearing you have - with a 3.73, a 7k redline is adequate. I'm stuck with a 4.10s (unless I want to spend $1k on 3.64s, or $500 for a negligible change to 3.91s) so having a higher redline helps me carry out the gears further (33mph 1st, 59mph 2nd, 94mph 3rd, etc).

Thank you this is what I was looking for...
I'm not looking to go above 7000rpm
I was just looking to see what it would take?
I'm new to the M20 and haven't had much time with mine
I just got the Miller kit chip/maf and I can put my rev limit anywear
I plan on boosting soon S/C and I want to know the limit of the motor..
No reason to go past that...
yet...;)

thanks everybody for the nice/good input

[briansjacobs]

It is possible to rev that high but you would have to put a lot of $ and time into your motor. We're talkin about a bigger cam, stroking the motor with a crank that has a longer stroke, as the m52b28(84mm), s50b30(86mm), s52b32(89mm). Custom lightweight forged pistons, stronger rods preferably from an s50 they have the same length as m20b25 135mm but they are lighter, you will need to bore your block max 86mm, head work, stronger valve springs, titanium retainers, stronger rocker arms, eccentrics, +1mm valves (not necessary), and probably a lot more that I am missing, but goodluck

I will disagree with this, the longer the stroke the lower the revs. kind of like putting bigger tires on a car. My stroker motor I am turning 3 seconds a lap faster at most tracks while turning 1000 less RPM then my built 2.5. I generally by 6100 now, where I was shifting at 7000 before.

[2.5-12]

S14b23.

[BlueBMW]

Put an m42 in there it'll rev to 7k no problem!