Does hitting the rev limiter F*ck up your engine?
#21
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Originally Posted by M6HuggerSS
because when your racing, its ideal that when you upshift you want to go from, peak hp then to peak TQ.... so if he shifts at 6K he may be as low as 3500, where he may need to be a 4500 for peak TQ....
pulling that extra, 600rpm on the top end puts him at a stronger rpm when he goes to the next gear......
pulling that extra, 600rpm on the top end puts him at a stronger rpm when he goes to the next gear......
#22
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I have video of what a 3 to 2 upshift and a 4 to 1 downshift at the race track really looks like.. Its not pretty. But engine lived. It should have the link later this week. John
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Originally Posted by M6HuggerSS
because when your racing, its ideal that when you upshift you want to go from, peak hp then to peak TQ.... so if he shifts at 6K he may be as low as 3500, where he may need to be a 4500 for peak TQ....
pulling that extra, 600rpm on the top end puts him at a stronger rpm when he goes to the next gear......
pulling that extra, 600rpm on the top end puts him at a stronger rpm when he goes to the next gear......
Your maximum acceleration will be achieved by maintaining maximum achievable torque at the wheels, right? So, you need to consider how much torque is going to the wheels right before the shift, and right after the shift, to find the optimal shift point.
Gears multiply torque, right? If the engine makes 300 ft-lbs (flywheel) at a certain RPM, and a hypothetical gear is 2.0:1, then 600 ft-lbs of torque will be pumping down the driveshaft (ignoring losses at the transmission) at that RPM in that gear.
When I set out to determine my optimal shift point, I was planning to do some calculus to maximize the area under my torque curve. But then, after considering my statements above, I decided to plot my dyno curve in 4th gear (1:1), and then show the multiplication factor on the curve for the first 4 gears.
In my case, it is obvious that I should shift at the limiter, despite the fact that HP and Torque have fallen off by then. The reason is that the torque multiplication advantage of the lower gear (before shifting) is typically significantly higher than the amount of torque or power fall-off. The lower my gear (1st is lowest), the more true this statement is.
For example, if you look at my multiplication chart (TorqGear.jpg), you’ll notice that I’m showing almost 800 ft-lbs at the wheels in 1st gear near 6000 RPM (well down from a ~900 ft-lb peak), but in second gear, it can be no better than about 625 ft-lbs at ANY RPM. Of course my curves ignore any FURTHER losses outside of 4th gear (which is 1:1, which is how the dyno was run), but I’ve got to believe it’s close!
In summary, my theory is that you need to look at your chassis dyno torque curve, and consider the torque multiplication factor of your transmission gear ratios, to determine optimal shift point. Your optimal shift point MAY be different for a different gear. I suspect, however, that optimal shift point will probably always be engine redline for almost any setup (maximize that torque multiplication factor before shifter to the next higher gear…).
What do you think? Am I crazy? Should we start a new thread to discuss? I’m interested in your comments. Sorry for the long post!
#24
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^ Bah, just shift a few hundred past your peak and call it a day.
If you really want to cut some time, trim your 60' down.
On a serious note, I'm sure you could dig up some shift/rpm threads using search which may help you out.
As for hitting the limiter, I've hit mine more often than I care to admit, but a big *** shift light in my face has cured the problem.
If you really want to cut some time, trim your 60' down.
On a serious note, I'm sure you could dig up some shift/rpm threads using search which may help you out.
As for hitting the limiter, I've hit mine more often than I care to admit, but a big *** shift light in my face has cured the problem.
#25
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Originally Posted by 2002SS#7867
Your maximum acceleration will be achieved by maintaining maximum achievable torque at the wheels, right? So, you need to consider how much torque is going to the wheels right before the shift, and right after the shift, to find the optimal shift point.
Instead of worrying about torque and gearing, just worry about making sure the hp is the same before and after the shift and you don't have to worry about the torque multiplication.
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I always hit mine if I miss a gear, other than that I try to stay away from it, some of the guys around here with Supras use it to shift off of for some reason. I don't think it will damage the car at all really, if fuel is cut completly then there is no burn and no heat so the lean should not hurt really as it is not a true lean since there is 0 burn.
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Originally Posted by KB99WS6
don't you have a TR224? I am surprised your rev limiter is set so high...and your still pegging it? What is the stock rev limiter set at?
Whats the difference between mechaincally over-revving it and hitting the rev limiter. I don't see how you can mechaincally over-rev it...thats what the rev limiter is for... ??
Whats the difference between mechaincally over-revving it and hitting the rev limiter. I don't see how you can mechaincally over-rev it...thats what the rev limiter is for... ??
#28
I hit my rev limiter a lot since my mods. I have the tr 224 112 & I have a shift light. The problem is if I lose traction in 1st or 2nd it hits the rev limiter before I can react. I don't have access to a tuner, maybe I should mail in my puter to get the rev limiter raised.
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Originally Posted by BlackCamaroSS02
I missed the 3-4 shift once and put it into 2nd . I pulled over right after and let the car idle for 30 sec then shut it off and poped the hood to let it cool...i bet it looked pretty cool though when i did it cause the tires started smoking in the back from it breaking loose lol
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Originally Posted by 2002SS#7867
Your maximum acceleration will be achieved by maintaining maximum achievable torque at the wheels, right? So, you need to consider how much torque is going to the wheels right before the shift, and right after the shift, to find the optimal shift point.
Do the math and calculate your points based on a dynograph - shift as high as is mechanically safe within the above guidlines
Here's some reading on this: http://mclements.net/mrc-PowerTorque.html
He explains the concepts pretty well
#32
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Originally Posted by CamTom12
there's no need to shift as you're still achieving optimal acceleration.
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Originally Posted by KB99WS6
Just curious b/c when ever I get into a serious race (which is very rare for the record) I am always hitting the damn rev limiter at least once. basically it jiust feels like there car is running out of gas, but I want to know if it messes things up...
btw it set at the stock setting
btw it set at the stock setting
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Originally Posted by code4
The problem is if I lose traction in 1st or 2nd it hits the rev limiter before I can react.
I hit the rev limiter all the time, it reminds me that I need to shift gears when I'm drunk
#37
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I'm going to echo the shift lite statement. They are cheap and easy to set up. Whenever I get in a race I don't even have to think about the revs or shifting. As soon as I see the light flash I just 'automatically' shift. Drops the risk a lot too, you only have to pay attention to the road, not watching your tach. Plus you'll do better because you'll be shifting at the right place. Hitting the rev limiter is a surefire way to lose a close race. It's like your car hits a wall.
Dope
Dope