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Not Reving over 6,000 RPMs

Old 06-25-04, 05:44 PM
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Not Reving over 6,000 RPMs

I would really appreciate some help on my problem.



I have an 87 N/A that I have turned into a drag car, ( full cage, sheet metal interior, slicks, 2000 pounds .... )



The injection was completely removed, and has a carburetor setup on it. (holly 650 and racing beat manifold.)



I built my own engine due to lack of money from building the car.



I used an all 91 engine because I like the fact that it has more compression and lighter rotors/flywheel ect...



I also did a mild street port on the engine, nothing major, nothing fancy.



My problem is that when I first built the car, I did a couple test runs up my fathers LONG driveway, and it ran strong and hard, heck, it gave me a nice big smile after building this car for a year to see it run so well.



anyways, back to the problem. it ran strong and hard for a couple passes up the driveway, then the next time I went to test it out, the car will not go over 6,000 RPM's. (unfortunately I discovered this at the Palmdale drag strip)



its like having a revlimiter on at 6,000 but there is no rev limiter in the car.



If I play with the throttle I can get it to go up a little but not nearly what it should be, and obviously not raceable.



Some days its only 5,500 RPMís some days I can hit 7,000. but like I said its nothing like it should be. (when I was at palm dale, my 2,000 pond car ran a 20 second passÖ. Thatís how bad it is.)



the ignition system consist of 3 60,000 volt coils 2 for each primary, and one for the 2 secondarys. (and yes I have tried running it with just the stock 2 coils also)



some trouble shooting I have done is:



8 different carburetors on it

2 different distributors

testing the coils

replace all three igniters twice.

replacing spark plugs, and wires

setting the fuel pressure from 4 to 7 pounds

compression tested ok

leak down test of the coolant system, ( to make sure it was not leaking into the engine )

also tried both stock ignition, and the way I have it now (with the 3 coils)



I just donít get it, it ran good far a day, and runs terrible since then. I really donít know what else to do. I would greatly appreciate any suggestions you have



Have you ever heard of a car with no computer, and no rev limiter, have a problem reving up before?



if you want a better look at the car please go to http://groups.msn.com/ROTORLUTIONRacing
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Old 06-26-04, 03:00 AM
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Advance the timing a little...???
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Old 06-26-04, 08:45 AM
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Does it start to miss and break up or does it just fall flat? Tried a compression test?
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Old 06-26-04, 10:33 PM
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Yes i have tried advancing the timing...

I have done a compression test, and its just fine.

I would say it spits and sputters, but not to bad. I mean its not spiting and sputtering so bad, it throwing flames out the exhaust, or poping, and back fireing. it seriously sounds like its on a rev limiter. to tell you the truth it sounds good, and sounds mean, but its just not supposed to happen.
(and no there is no rev limiter, computer, MSD, or anything to that nature... read above)

thanks for any sugestions you all have.
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Old 06-27-04, 08:02 PM
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The leading plugs can share a coil (and fire at the same time, with a wasted spark), like they do on the stock system. The trailing plugs need independent coils due to their timing (you can't fire the trailing plugs at the same time). Are you sure the ignition system is setup correctly? Your message made it sound like you are using one coil for both trailing plugs.

-Max
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Old 06-27-04, 10:03 PM
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yeah i am running 1 coil for the two trailing plugs, and 2 coils for the 2 leading plugs.
This is how i was told to do it.

if this is wrong though, i do have a question though.... how come the stock system has only 2 coils to fire all 4?

i am not doubting you, infact i do thank you, you are the first one to suggest that. please give me some explanation to this, i will be more then happy to change it, if it means i can get my race car running!

one other question though.... how come when i had it in the stock form it did run ok for one run?

thank you so much!
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Old 06-27-04, 11:39 PM
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The stock system uses three coils. One for each of the two trailing plugs and one one for the two combined leading plugs. The twin coils for the trailing may appear to be one coil because they mount to the same bracket but it is two independent coils. The leading fire in waste spark mode. What that means is that they both fire at the same time even though only one of the rotors requires spark. Hense the wasted spark on the off rotor.
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Old 06-28-04, 09:50 AM
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++ i agree sounds like your trailing are firing at the same time
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Old 06-29-04, 01:35 AM
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the second gen did come with 3 coils yes, but the first gen came with only 2 coils, since i have a first gen distributor, i was talking about how the first gen has only two coils....

what do you think?

thanks again for all your help.
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Old 06-30-04, 11:33 AM
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any ideas?
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Old 07-07-04, 05:56 PM
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nothing?...
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Old 07-07-04, 06:50 PM
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If it's making compression then it has to be fuel or spark. If you think the spark is right then concentrate on the fuel. Could be when it ran right the atmospheric conditions where much different and now it isn't getting enough fuel. Rich will usually give a sputtering, maybe popping, rev. It'll be rough but still rev. Too lean and you can have just what you're getting.

Shot in the dark man.
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Old 07-07-04, 06:54 PM
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thank you for your reply! I will be looking into fuel. then ignition, then engine....
thanks all.
if anyone has an idea, feel free to leave it.
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