Rev limiter?
Thread Starter
Le Mans Master
Joined: Apr 2000
Posts: 5,713
Likes: 105
From: Manassas VA
Rev limiter?
What are you, with modified motors using for a rev limiter? I have a msd 6al, but after 18 years or so, it is going bad. FWIW I know the chip has built in rev limiting, but it cuts fuel. I want to cut ignition.
Le Mans Master
Joined: Oct 2002
Posts: 7,098
Likes: 378
From: Las Vegas - Just stop perpetuating myths please.
MSD6AL with the little chips is the best solution I have come across. That would be the analog MSD6AL as I think the digital MSD6AL may be different and no longer use the plug in chips. All the other ignition boxes need to have the adjustment with a screw driver to turn a dial which can many times be awkward when you just want to drop off the car for service or whatever. It's been at least 2 years since I searched for a useful rev limiter but didn't find anything in the American market. Found a couple in the UK but they seemed to get complicated.
Yes you only have to have your car joy rided once to motivate you to install a rev limiter.
Yes you only have to have your car joy rided once to motivate you to install a rev limiter.
Melting Slicks
Joined: Mar 2001
Posts: 2,149
Likes: 303
From: Timra, Sweden
MSD6AL with the little chips is the best solution I have come across. That would be the analog MSD6AL as I think the digital MSD6AL may be different and no longer use the plug in chips. All the other ignition boxes need to have the adjustment with a screw driver to turn a dial which can many times be awkward when you just want to drop off the car for service or whatever.
If you want to be sure when leaving the car for service you could mount a plate over the adjustment dial and add a lead tamper seal to see if the plate was removed.
I use an aftermarket ECU (MaxxECU) and I can select both fuel cut and ignition cut. Different RPM for differernt situations if needed.
Last edited by JoBy; Mar 15, 2020 at 05:34 PM.
Thread Starter
Le Mans Master
Joined: Apr 2000
Posts: 5,713
Likes: 105
From: Manassas VA
What are you basing that on, or where did you read it? I would believe the raw fuel is hard on cats, but 2 step rev limiters do this very thing and are used all the time..... I dont want to cut fuel at 7000 rpm and lean the motor out like that. Much better to cut ignition.
Thread Starter
Le Mans Master
Joined: Apr 2000
Posts: 5,713
Likes: 105
From: Manassas VA
MSD6AL with the little chips is the best solution I have come across. That would be the analog MSD6AL as I think the digital MSD6AL may be different and no longer use the plug in chips. All the other ignition boxes need to have the adjustment with a screw driver to turn a dial which can many times be awkward when you just want to drop off the car for service or whatever. It's been at least 2 years since I searched for a useful rev limiter but didn't find anything in the American market. Found a couple in the UK but they seemed to get complicated.
Yes you only have to have your car joy rided once to motivate you to install a rev limiter.
Yes you only have to have your car joy rided once to motivate you to install a rev limiter.
I knew the msd 6al had gone to the digital, but I heard there were some reliablity problems... but I dont have any actual experience with them. I dont worry about abuse from a shop, its been years since anyone worked on it other then me.
Le Mans Master
Joined: Sep 2013
Posts: 6,192
Likes: 750
From: near the thumb in the mitten
What are you basing that on, or where did you read it? I would believe the raw fuel is hard on cats, but 2 step rev limiters do this very thing and are used all the time..... I dont want to cut fuel at 7000 rpm and lean the motor out like that. Much better to cut ignition.
Thread Starter
Le Mans Master
Joined: Apr 2000
Posts: 5,713
Likes: 105
From: Manassas VA
This just simply is not true...... When you cut fuel, ignition continues to fire, as you are setting there on the rev limiter, fuel is cut, both on and off to hold rpm from going above the set limit. This causes a lean condition, which is very hard on the motor......
I believe you have a 93? Factory setting is 57-58 hundred, I think. Try reving it up past that and you will see what I mean.
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Le Mans Master
Joined: Sep 2013
Posts: 6,192
Likes: 750
From: near the thumb in the mitten
GM uses fuel shut off to prevent as they call it "engine over speed". If it would damage engine the engineers would have come up something else. With batch fire it's more dramatic since multiple injectors are turned off. On various models with SFI ECM can randomly turn off injectors during over speed and traction control events. Turning off both RPM and MPH speed limiters is very common with custom chip makers.
Safety Car
Joined: Sep 2001
Posts: 4,153
Likes: 553
From: Glenbeulah Wi
Cutting fuel is the preferred way to limit engine RPM. No fuel is not lean, no fuel is just that no fuel, not lean. Old school rev limiters had to cut spark since they always had fuel with a carb, EFI cars can cut the fuel which is much better. (Assuming you are not running a wet nitrous system)
Race Director
Joined: Apr 2003
Posts: 17,699
Likes: 1,667
From: moraga ca
I have run a MSD 6AL and now a 6AL digital. I had no problem with either unit. It's easier to turn a dial than to swap a chip. To control revs, the MSD units drop spark in alternating cylinders. There is no build up or pooling of fuel.