RPM 7000+ How?

[MonkeyMadness]

Whats it take to for a M20 to Rev above 7000 with out problems?

Ok so let say you don't have a rev limiter on your car, and you can't seem to let off the gas in time to shift before 7000rpm
And your looking into building a motor for some high reving fun.
Whats it take to get above 7000+ rev with out having to get a broom and dust pan to pick up parts later?
parts combo, cams, wtf?...

[5KWattson]

In all honesty the +7k rev might not be best depending on what you intend to use the car for and how long, not havin a whole lot of m20 info I'll leave it to someone else but rev'n that high with a m20 might not do much other than waste gas and make noise since the power band will prob dip before that, and if your not making power why rev up that high? But like I said m20's I have a very limited knowledge on.

[akinswonder]

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

[e30trooper]

More info here: http://www.e30tech.com/forum/showthre...
E30 with naturally aspirated but highly modified M20 engine does 0-240km/h on the Haapsalu old Soviet army airfield. Was recorded on the event One Mile Challange. Real thing - without any tricks. In case of any doubts - look my other videos.



bmw e30 325i, M20 2,8 stroker, naturally aspirated, in dyno 08.05.2009. Measured 224hp (164,4kw) and 292,3nm. Sorry for bad sound quality...

[nando]

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).

In all honesty the +7k rev might not be best depending on what you intend to use the car for and how long, not havin a whole lot of m20 info I'll leave it to someone else but rev'n that high with a m20 might not do much other than waste gas and make noise since the power band will prob dip before that, and if your not making power why rev up that high? But like I said m20's I have a very limited knowledge on.

please do.

[jlevie]

Assuming a stock M20B25 engine and Getrag 260 transmission, a good approximation of an optimal shift point for the higher gears is 6100rpm. The optimal shift point is determined by the torque curve and gearing. So there's little point in raising the rev limit unless you modify the engine to change the torque curve.

[BlueBMW]

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

[2.5-12]

S14b23.

[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.

[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

[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:

[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]

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

[nando]

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

[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.