How hard on an engine is hitting the rev limiter

[CamKing]

In the 90's, the IRL engines had hard limiters on them(10,700rpm). I had almost every car running my cams, but one driver(Buddy Lazier) kept having valvetrain failures. When looking into it to find the issue, we found out he was gearing the car so it would be on the rev-limiter just past the flag stand, so it would transfer the weight towards the front, to get thru the corner, without having to lift.
Figuring that was the issue, we ran the engine on the dyno, with the rev-limiter. Without the rev-limiter, the valvetrain was stable past 11,500rpm. When we put the revlimiter on, it would cause valve float, and shortly after it hit.

After that, we put a soft limiter on, that came on before the hard limiter.

[swampbuggy]

At 6000 RPM
6000÷60seconds in a minute =100 revolutions per second.
In a 4 cycle engine, plug fires every other revolution of crank.
50 sparks. Per cylinder. Per. Second. Mark H.

[202ci EH]

Get it right man, it's Moo Mang, not Mang Mang!

The local burnout boys found their valve trains lasted much longer if they just wound the limiter up out the way - excessive rpm was less harmfull than smacking the limiter hard & often.

That's a new one! Haven't heard of moo mang before.

We call VN s1 shong shongs and ecotecs mangs

[woody b]

My uneducated opinion is that most of the damage caused by sitting on the limiter is due to harmonics caused by the constant, steady RPM. I was one of the first people (that I know of) to use a chip during a burnout. I didn't just hammer the throttle and sit on the chip though, I feathered the throttle, using the chip kind of like a guide. Local races added 3 steps (2, 2 steps at that time) for consistent burnouts and some started having engine problems. The ones having the problems would just hammer the throttle and sit on the chip hard during the entire burnout.

OTOH, I used to use a down track "stutter box" on a timer with as much as 5 or 6 seconds in it with no problems. The rpm was much lower for this, usually 4000 or less. I never had any engine problems then. I suspect the harmonics were much less of a problem at a relatively low rpm.

What do the experts say?

[donclark]

David Reher weighed in on this several years ago, basically saying that laying on the rev limiter during a burnout destroys engines. I instilled in my grandson early on if you cannot do a burnout without touching the rev limiter you have no business driving a drag car. That was seven years ago and I have yet to hear him hit it.

[mag2555]

Harmonics? Hell yes!!!
Let's look at something like 1200 hp motor, 15 to 1 comp , 4.375" Bore making 1800 psi when the plug fires.
This will make for over 27000 psi driving the piston down the Bore!
But now slap the motor into the rev limiter and not have that 27000 psi around at times on some cylinders while others do have 27000 at 7000 rpm or better!
What extremely uneven loads do you think the Crank see's and in turn the main web in the block at times like this,if you look at this in regards to only a 600 hp motor where taking about 13,500 lbs of unbalance !

[Krooser]

Every Saturday night you have thousands of dirt track IMCA racers hitting the Rev limiter on every lap with their crate motors... 6200 rpm.

[randy331]

This engine gets set on the rev limiter every pass, either for traction control or reaction time.
Below it's being used to race in a cross talk bracket class without a delay box in the car. I had tape on the windshield so I could block out all the tree but my bottom yellow and green. As soon as both pre stage and stage lights were on I'd move so the tape blocked the tree and went on the bottom yellow, basically 5 tenths pro tree racing vs cross talk in the other lane, so when I was spotting slower cars it's on the limiter for a while.
If you look through the windshield you can see when my top bulb comes on, but I can't see it yet.

It's still together, but that don't mean it ain't hard on them I guess.

https://www.youtube.com/watch?v=G5q2rRefJco

Randy

[grant6395]

David Reher weighed in on this several years ago, basically saying that laying on the rev limiter during a burnout destroys engines. I instilled in my grandson early on if you cannot do a burnout without touching the rev limiter you have no business driving a drag car. That was seven years ago and I have yet to hear him hit it.

^^^
Couldn't agree more. It's a ness evil for us stick car guys, but camping out on it during the burnout is something I will never understand.

[statsystems]

David Reher weighed in on this several years ago, basically saying that laying on the rev limiter during a burnout destroys engines. I instilled in my grandson early on if you cannot do a burnout without touching the rev limiter you have no business driving a drag car. That was seven years ago and I have yet to hear him hit it.

^^^
Couldn't agree more. It's a ness evil for us stick car guys, but camping out on it during the burnout is something I will never understand.

Anyone have a link to the DR article mentioned above? I'd like to read it.

BTW...it's been a long time since I've been to an actual Pro Stock race but don't they do the burnout on the limiter?

[donclark]

David Reher weighed in on this several years ago, basically saying that laying on the rev limiter during a burnout destroys engines. I instilled in my grandson early on if you cannot do a burnout without touching the rev limiter you have no business driving a drag car. That was seven years ago and I have yet to hear him hit it.

^^^
Couldn't agree more. It's a ness evil for us stick car guys, but camping out on it during the burnout is something I will never understand.

Anyone have a link to the DR article mentioned above? I'd like to read it.

BTW...it's been a long time since I've been to an actual Pro Stock race but don't they do the burnout on the limiter?

http://rehermorrison.com/tech-talk-79-a ... ur-engine/

[bentvalves]

nobody has mentioned the different types of rev limiters and the pros and cons of each strategy.

fuel cut vs. spark cut vs. a combination of both etc etc.

some high-end ECU's can limit rpm in such a delicate manner it sounds like the engine is just hovering at a steady clean 8k. these steady, clean, soft limiters can be devastating to turbocharged engines.

[statsystems]

^^^
Couldn't agree more. It's a ness evil for us stick car guys, but camping out on it during the burnout is something I will never understand.

Anyone have a link to the DR article mentioned above? I'd like to read it.

BTW...it's been a long time since I've been to an actual Pro Stock race but don't they do the burnout on the limiter?

http://rehermorrison.com/tech-talk-79-a ... ur-engine/

Thanks