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Rev limiter

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Emmanuel M6
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Joined: Fri Aug 07, 2015 11:07 pm

Rev limiter

Post by Emmanuel M6 » Thu Aug 09, 2018 11:48 pm

Greetings hope you are all well and that your cars are well. Finally, give thanks to Jah, I can see me getting my car rust free and sprayed. I live in Northampton and have my local BMW specialist in mind to do the job. Notwithstanding, if any members have any recommendations I'd be interested. The work is basically wings off and repaired, any rust anywhere dealt with, and replacing old items with new.
I have one question please; my European m635, what amount ofrevs is the limiter supposed to come in at in first gear? I always seem to hit it when I want to extend the car.
Wishing you all well and your cars also, usual shout out to the don bru6e.
Peace.
Emmanuel M6
1985 M635csi
Location Corby Northants, previously London U.K.

GazM3
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Joined: Wed Oct 26, 2011 12:55 pm
Location: Melbourne, Australia

Re: Rev limiter

Post by GazM3 » Fri Aug 10, 2018 2:05 am

Around the 6900-6950 mark for memory. It feels like the m88 is redlined 1000rpm short. The only major hurdle from 7500rpm is the crank hub. Upgraded ones are available. 😎
BMW’s
74 2002 2.3ltr
84 E24 M635csi
94 E34 540i/6 SC
97 E36 M3 euro SC U/C

OTHERS
02 Landrover D2 td5
08 Holden Ute 6.0
11 Audi S5

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DRPM635CSi
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Re: Rev limiter

Post by DRPM635CSi » Mon Aug 13, 2018 1:15 pm

The gear you're in doesn't matter. The hard cut rev limit is coded in the software on the 28 pin 27C64 EPROM chip in the 055 DME box. Stock it is set to 6900rpm.

There is no conventional reason to bother revving the engine beyond this because at 6,900rpm you're well & truly on the downside of the power curve already & a gear shift will put you on the downside of the torque curve too. Unless you're competing in motorkhana events, there is nothing to gain by revving the engine this hard and if you are competing in such events you'd be far better off in something a lot smaller like a caterham super 7 instead.

GazM3
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Joined: Wed Oct 26, 2011 12:55 pm
Location: Melbourne, Australia

Re: Rev limiter

Post by GazM3 » Tue Aug 14, 2018 3:23 am

Really?

On both my dyno graphs peak power is at the cutout point 6950 and with the fritz chip 7200


The crank hub upgrade I’d have no problems spinning the m88 to 8000rpm assuming upgraded or recent changes timing chain and possibly fresh valve springs.

If driving hard on a track or your favorate mountain pass it’s good to have the ability to rev past peak power as long as power doesn’t drop off too much as then when u upchange you are further into the rev band
BMW’s
74 2002 2.3ltr
84 E24 M635csi
94 E34 540i/6 SC
97 E36 M3 euro SC U/C

OTHERS
02 Landrover D2 td5
08 Holden Ute 6.0
11 Audi S5

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DRPM635CSi
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Posts: 270
Joined: Thu Jul 09, 2015 6:50 am
Location: Perth, Australia
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Re: Rev limiter

Post by DRPM635CSi » Tue Aug 14, 2018 4:11 am

GazM3 wrote:
Tue Aug 14, 2018 3:23 am
Really?
Page 6-09 of your owner's manual. Peak power is at 6,500rpm and then drops steeply off thereafter.

GazM3
Bigcoupe supporter
Posts: 1727
Joined: Wed Oct 26, 2011 12:55 pm
Location: Melbourne, Australia

Re: Rev limiter

Post by GazM3 » Tue Aug 14, 2018 9:58 am

Perhaps the book graph tested in c/1984. Chassis dyno tells otherwise. They are hand built motors so often the factory claims the minimum it will make. Remember back in the 80s and 90s Germany had big taxes on cars making more than 213kw. Magically lots of cars from the time have c/210kw as their maximum.
BMW’s
74 2002 2.3ltr
84 E24 M635csi
94 E34 540i/6 SC
97 E36 M3 euro SC U/C

OTHERS
02 Landrover D2 td5
08 Holden Ute 6.0
11 Audi S5

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