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Old 11-09-2011, 03:12 PM   #1
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Merc 2.4 efi over rev

Has anyone fitted a rev limiter to a 1990 merc 2.4 efi before? during rough races we are having a problem with the motor over reving and then cutting out,i thought by fitting a limiter it would solve this problem but im not sure if its possible to do
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Old 11-09-2011, 04:17 PM   #2
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i cant see any rev limiter being quick enough to limit what is in effect free revving the engine with no load. I'd be more concerned as to why the engine cuts out as the limiter built into those ecu's simply go full rich at a certain revs and shouldnt make the motor cut out
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Old 12-09-2011, 11:24 AM   #3
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I've had that happen before, switched from an A4 7500 limit to an A48 (drag ecu 11500 limit) and it hasnt happened since.

That wasnt the reason we switched the ECU, but noticed now that you mention it that it hadnt happened since.
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Old 12-09-2011, 09:20 PM   #4
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hi alan,sounds like this could solve the problem where did you get the drag ecu from?and what sort of price are they?cheers
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I've had that happen before, switched from an A4 7500 limit to an A48 (drag ecu 11500 limit) and it hasnt happened since.

That wasnt the reason we switched the ECU, but noticed now that you mention it that it hadnt happened since.
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Old 12-09-2011, 09:57 PM   #5
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Trouble is it will also allow your motor to rev to 11500, even if only for a moment, which can be incredibly damaging on a motor that isn't as balanced as a drag spec one.

Am I also right in thinking that the A48 ecu leans out on the way to high revs to heat the block in preperation for the big revs? This wouldn't be good news for a motor usually run at 6-7k
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Old 13-09-2011, 01:58 AM   #6
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Trouble is it will also allow your motor to rev to 11500, even if only for a moment, which can be incredibly damaging on a motor that isn't as balanced as a drag spec one.

Am I also right in thinking that the A48 ecu leans out on the way to high revs to heat the block in preperation for the big revs? This wouldn't be good news for a motor usually run at 6-7k
Thats food for thought, although I doubt it would ever see 11500 even if you kept the pedal down. Do a lot of the ROS motors not have the limiters removed?

I've never heard of the lean out on the drag, I ran that ECU for about a year on my SportCat until the bridgeport did what bridgports do best! And always ran that motor between 6 and 7, ran it to 9 occasionally, funny it died on one of those occasions

Daren, the ECU came on a motor I bought in the states. Im not using it at the moment if you want to try it, see if it cures your problem. Would probably pick one up on S&F. Or look for a Bructto ACU/PCU thats what I want to play with next!

Might actually be worth an Email to Tony Brucatto about your problem.
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Old 13-09-2011, 09:20 AM   #7
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You could always try using the throttle pedal !! They do a really good job of limiting revs !!
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Old 13-09-2011, 09:44 AM   #8
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I thought your prop looked a little small when I overtook you a few times
Then you returned the compliment !-Good racing Leds cant wait for the
Prestigious Herm Race
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Old 14-09-2011, 03:49 PM   #9
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drag ecu's lean out at around 5000rpm to build heat ready for the big push to stupid revs.
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Old 15-09-2011, 09:38 PM   #10
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Quote:
Originally Posted by OCRDA View Post
You could always try using the throttle pedal !! They do a really good job of limiting revs !!
thats the plan bob but when your racing in force5/6 winds and a big swell like last weekend you arent going to get it right all race!!!
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Old 15-09-2011, 09:45 PM   #11
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Quote:
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I thought your prop looked a little small when I overtook you a few times
Then you returned the compliment !-Good racing Leds cant wait for the
Prestigious Herm Race
i dont remember you overtaking us you were well and truly tangoed!! bring on the herm race lets hope the weather is with us this year!!!!
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Old 15-09-2011, 11:26 PM   #12
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Quote:
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drag ecu's lean out at around 5000rpm to build heat ready for the big push to stupid revs.
Well you learn something new every day!
It did run fine on the cat for a long time, although probably explains the lack of balls that engine had in the mid range!
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