Rev limiter for 4.0s

ashmanjeepxj · Mar 10, 2005

I did a search, didnt find anything.
I have an 88 4.0 and want to add a rev limiter. What options are available?

When Im really gettin it, after the fact I dont recall what RPMS I hit, its almost impossable to watch when your gettin it.

Its never been an issue in the rocks (mostly stalling issues) but in loose dirt, its all out or nuthing.

Yea I need bead locks too, but ti ripped off the valve stem once it got sideways.

BIGWOODY · Mar 10, 2005

I'm in the same boat, I imagine MSD or some other aftermarket ignition system has them build in. As far a staying with a stock set up, on my 2002 race car we ran a rotor button that had and inertia switch type set up, when it reved to a certain RPM(adjustable) the centrifugal force would disengage contact on the rotor button. May sound a little complicated , but actually it was quite a simple design that only required replacing the rotor button, as for finding one for a jeep..I dunno.
I tend to get more concerned with "making " the obstacle then RPMs...as show in the video below..lol

http://www.fototime.com/users/[email protected]/More beating

5-90 · Mar 10, 2005

MSD does make a rev limiter, but it's designed to work with their 6-series (like the 6-Offroad) ignitions. Of course, if you are going for power, you're probably going to stroker or supercharge (or both!) eventually, and you'll want a better ignition.

The 6-series adapts nicely to the RENIX setup - but it does require installing a small set of spacers under the coil so it can be separated from the module, then the MSD is wired to the module terminals and the coil once you can get to both of them. Looks pretty easy - and MSD offers the wiring as a kit, leaving the longer screws and spacers up to you (but you can do that with parts from the local anyhow...)

5-90

ashmanjeepxj · Mar 10, 2005

BIGWOODY said:
I'm in the same boat, I imagine MSD or some other aftermarket ignition system has them build in. As far a staying with a stock set up, on my 2002 race car we ran a rotor button that had and inertia switch type set up, when it reved to a certain RPM(adjustable) the centrifugal force would disengage contact on the rotor button. May sound a little complicated , but actually it was quite a simple design that only required replacing the rotor button, as for finding one for a jeep..I dunno.
I tend to get more concerned with "making " the obstacle then RPMs...as show in the video below..lol

http://www.fototime.com/users/[email protected]/More beating

LOL

That took forever.. I guess it was really wet and sloppy?
Watching the video you can count the 90-89-88-87-86-86-86-85% tread

BIGWOODY · Mar 10, 2005

ashmanjeepxj said:
LOL

That took forever.. I guess it was really wet and sloppy?
Watching the video you can count the 90-89-88-87-86-86-86-85% tread

Tellico ....when its wet it's damn near impossible in spots...

CW · Mar 10, 2005

I run an msd 6 ignition and it works real well with my stroker. You can get rev limiters for them and you can get the install kit that comes with everything you need. It only took me about 20 minutes to install every thing.

ashmanjeepxj · Mar 10, 2005

5-90 said:
MSD does make a rev limiter, but it's designed to work with their 6-series (like the 6-Offroad) ignitions. Of course, if you are going for power, you're probably going to stroker or supercharge (or both!) eventually, and you'll want a better ignition.

The 6-series adapts nicely to the RENIX setup - but it does require installing a small set of spacers under the coil so it can be separated from the module, then the MSD is wired to the module terminals and the coil once you can get to both of them. Looks pretty easy - and MSD offers the wiring as a kit, leaving the longer screws and spacers up to you (but you can do that with parts from the local anyhow...)

5-90

That looks like over kill, and not for emissions controlled vehicles.
http://www.msdignition.com/ignition_10_6600.htm

Thats rated up to 15k RPMs, Im thinking 4-4.5k rev limited would work best on the 4.0.

All it has to do is cut out the spark when the tack goes higher then what you set it at. It only would require a Tack sensor wire input, and a switched power output that goes to your coil. Does something like that exists?

MudDawg · Mar 10, 2005

Just because the MSD is rated for very high rpm, it doesn't mean that is the rpm it will limit to....you adjust the limit rpm with replacable "chip" that plug into the MSD or module adapter....the way it works is as you approach the limit rpm, the module interrupts the ignition signal and the engine "sputters" and won't rev higher (basically put).

5-90 · Mar 10, 2005

The 6-Offroad is exempt under CARB E.O D-40-25, making it 50-state legal. I do not believe that the rev limiter actually requires an E.O number - and none of it really matters if you are not in CA, since nearly everything that MSD does that isn't "Race Only" is 49-state legal.

The rev limit can be set with a plug-in module, which means it can also be changed at will. It comes with modules to drop sparks at 4K, 6K, and 8K - 6K will work for your needs, but you can also get modules in sets per 1000 RPM, with 200 RPM spacing - and you order either an "even" kit (x000/x200/x400/x600/x800) or an "odd" kit (x100/x300/x500/x700/x900.) Would that work for your needs? Module kits carry CARB E.O D-40-29.

Here's part numbers to save you digging around the MSD site (Page numbers refer to the 2005 MSD catalogue, which I have on my desk. Research material for book updates, you know...):

P/N 6470 - MSD 6-Offroad (p.19)
P/N 8769 - Offroad Rev Control (p.19)
P/N 8745 - Modules, 5000/5200/5400/5600/5800 (p.109)
P/N 87451 - Modules, 5100/5300/5500/5700/5900 (p.109)

Installation of the 6-Offroad is electrically simple - and one of these days, I'll figure out just what it takes (right after I quit smoking and drinking, at the rate I'm going :laugh3: ) to "boost" the RENIX coil and let everyone know. Shouldn't be too hard, tho.

Anything else I can help with?

5-90

ashmanjeepxj · Mar 10, 2005

5-90 said:
The 6-Offroad is exempt under CARB E.O D-40-25, making it 50-state legal. I do not believe that the rev limiter actually requires an E.O number - and none of it really matters if you are not in CA, since nearly everything that MSD does that isn't "Race Only" is 49-state legal.

The rev limit can be set with a plug-in module, which means it can also be changed at will. It comes with modules to drop sparks at 4K, 6K, and 8K - 6K will work for your needs, but you can also get modules in sets per 1000 RPM, with 200 RPM spacing - and you order either an "even" kit (x000/x200/x400/x600/x800) or an "odd" kit (x100/x300/x500/x700/x900.) Would that work for your needs? Module kits carry CARB E.O D-40-29.

Here's part numbers to save you digging around the MSD site (Page numbers refer to the 2005 MSD catalogue, which I have on my desk. Research material for book updates, you know...):

P/N 6470 - MSD 6-Offroad (p.19)
P/N 8769 - Offroad Rev Control (p.19)
P/N 8745 - Modules, 5000/5200/5400/5600/5800 (p.109)
P/N 87451 - Modules, 5100/5300/5500/5700/5900 (p.109)

Installation of the 6-Offroad is electrically simple - and one of these days, I'll figure out just what it takes (right after I quit smoking and drinking, at the rate I'm going :laugh3: ) to "boost" the RENIX coil and let everyone know. Shouldn't be too hard, tho.

Anything else I can help with?

5-90

I found a 6470 on ebay for $220, That cost will bump this down to low on my priority list for now. How much are the modules?

What RPM limit would be safe on a stock 4.0? I like to lean on the safe side rather then push alittle past the limit.

CRASH · Mar 10, 2005

I rev my Renix stroker to 5,700 -5,800 with no problem. Redline on a stock Renix 4.0 is 5,500 from the factory.

CRASH

jjvande · Mar 10, 2005

On my '88, which just turned 200K, i wont reve it past 4000, theres no point

5-90 · Mar 10, 2005

Let's see...

I've pushed my 88XJ 4.0 w/240K to 6000RPM a couple times for about an hour at a stretch, and it ran fine (that's just under the harmonic, and that's a known issue - but I didn't want to push thru it...)

Torque is greater than horsepower under 5252RPM, where they bcome equal and HP increases as torque falls off...

We tend to like the 4.0 for its solid torque at low RPM...

RENIX 4.0 (per Desktop Dyno) makes good torque right up to about 4000RPM, at which point it falls off sharply...

And, you're probably not going to hit high revs while 'crawling...

I'd run about a 4000-4200RPM module off-road, and swap it for about 5500 when you get back on the pavement. While on the freeway, I'll want all I can get for passing and such - and sometimes hitting the horsepower transition makes the difference. How's that sound?

(I know it's a bit long, but I thought I should give my reasoning behind the decision before I was done.)

5-90

ashmanjeepxj · Mar 11, 2005

5-90 said:
I'd run about a 4000-4200RPM module off-road,

I think that sounds good.

Any cheeper options other then the bling MSD 6?

Kittrell · Mar 11, 2005

Jacobs?

MudDawg · Mar 11, 2005

Anything else is a wanna-be MSD....the only system I know of that is better won't apply to the 4.0 unfortunately. It is a sytem made by a company called Dyna Ignition Inc. I haven't looked in on them in a while, the last time I saw a catalog they only made them for v-twin and 4 cylinder applications. They are digital and have a mad number of features. I think that 2.5 V2/MK1 will get a crank triggered distributorless system to make the ignition completely waterproof.

Purple · Mar 11, 2005

Try Mallory, they have one that does not need chips or anything to adjust rev limit, it has jumpers just like a computer mbo

Kittrell · Mar 11, 2005

MudDawg said:
Anything else is a wanna-be MSD....

Experience the ONE TRUE God, MSD ignition.............

Dr. Dyno · Mar 11, 2005

CRASH said:
I rev my Renix stroker to 5,700 -5,800 with no problem. Redline on a stock Renix 4.0 is 5,500 from the factory.

CRASH

As far as I remember, the stock redline is 5000rpm on the Renix 4.0, 5250rpm on the '91-'96 4.0, and 5300rpm on the '97+ 4.0. Strangely enough, I've seen '04 4.0 WJ's in the Jeep showroom with a 5800rpm redline and '04 4.0 TJ's with a 5650rpm redline. I don't know why they have a redline at such rpm when maximum HP is at 4600rpm and by 5000rpm, the torque curve is dropping off sharply.
My 4.6 HO stroker won't rev beyond 5250rpm because of the factory limiter but going much beyond that seems pointless anyway.

CRASH · Mar 11, 2005

Dr. Dyno said:
As far as I remember, the stock redline is 5000rpm on the Renix 4.0.

I rev my Renix stroker to 5,700 -5,800 with no problem. Redline on a stock Renix 4.0 is 5,500 from the factory.

Rev limiter for 4.0s

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