Is it bad to redline your car?

[Hokiefyd]

Originally Posted By: gathermewool
IMO, the torque being applied is more detrimental to the transmission than the actual speed, which would mean a peak-torque shift would cause more band wear than a redline shift, right?


I don't know the answer to that question. But I think it'd be hard to truly get an automatic to shift at peak torque anyway, even forgetting a powertrain's torque management system.

Say your engine makes peak torque at 4,200 rpm and has a redline of 6,500 rpm. At WOT (100% throttle), your transmission should shift somewhere at or just slightly under 6,500 rpm, which is the indicated redline. For it to shift anywhere below that takes some amount of throttle less than 100%. So to get an automatic to shift down at the engine speed where peak torque would occur at 100% throttle (4,200 rpm in this case), you'd have to be giving it less than 100% throttle (say 75%), so the engine wouldn't be making the rated amount of torque anyway.

 

[d00df00d]

Solution: Floor it until the desired shift point and then quickly let off just enough to trigger an upshift.

 

[Hokiefyd]

Originally Posted By: d00df00d
Solution: Floor it until the desired shift point and then quickly let off just enough to trigger an upshift.

But then you're not at peak torque anymore. You are at the engine speed where peak torque would occur, but without full throttle, you wouldn't be getting the torque peak from the engine.

 

[d00df00d]

Oh, okay. I get what you're saying now. When I responded, I was taking your post out of context. Apologies for the tangent.

 

[Dave424]

The lower your shift rpms the better for the trans. The higher the rpm the bigger the difference in the transmission shaft speed in the next gear is going to... therefore, higher rpm = more friction in the syncros/clutch packs = more wear and more slipping of the torque converter = more heat generated.

 

[SteveSRT8]

Guys, the throttle can easily be at 100% and the engine nowhere near peak anything! You can still command a shift on many slushboxes.

And most cars have so much factory torque management built in that the throttle is pulled and the timing reduced and the shift is MUCH easier on the trans.

Hearing a lot of old outdated info here on slushboxes.

 

[cchase]

Originally Posted By: SteveSRT8
Guys, the throttle can easily be at 100% and the engine nowhere near peak anything! You can still command a shift on many slushboxes.

And most cars have so much factory torque management built in that the throttle is pulled and the timing reduced and the shift is MUCH easier on the trans.

Hearing a lot of old outdated info here on slushboxes.



True, but not everyone has a new vehicle on BITOG.

 

[rslifkin]

^ No, but even my Jeep cuts the timing way back on heavy throttle shifts to save the transmission.

 

[OVERKILL]

Originally Posted By: SteveSRT8
Guys, the throttle can easily be at 100% and the engine nowhere near peak anything! You can still command a shift on many slushboxes.

And most cars have so much factory torque management built in that the throttle is pulled and the timing reduced and the shift is MUCH easier on the trans.

Hearing a lot of old outdated info here on slushboxes.



And there are also some pretty strong automatics out there too. My Expedition doesn't pull anything when it shifts. But the 4R100 doesn't need it to. It was designed to handle full-power upshifts through all gears.

 

[UNC017]

Originally Posted By: SteveSRT8
Originally Posted By: Josh48065

Quote:

I've been redlining (and revving past Redline by 400rpm) since my 2007 Civic Si was new. It now has 110,000 and still runs like new. It has seen track time (time attack racing) and I beat on it daily (check my used oil analysis posts) and all is well.

Enjoy your car. Keep up with maintenance and it will last a long time for you.


Though.. Do you have a manual transmission? A/t seem not to handle high rpm shifts as well


This is extremely platform dependent. Many higher powered AT cars have so much torque management software controlling every aspect of the shift event that it is nearly impossible to harm the trans. You would not believe what's going on in a couple hundred milliseconds!

So just say "some AT's" and not all.


And the really OLD transmissions (like Torqueflite 727s, TH400s, and C6s) are tough enough to upshift at the full power/torque output of anything they were bolted to. Its the transmissions from the mid 70s through the early 90s that tend to hurt themselves- manufacturers were making the components lighter to make them more efficient, but cutting into the margin needed to survive upshifts with the engine producing peak torque all the way through the shift. When torque management algorithms started becoming widespread, transmission life started going up again because the shifts occur at much reduced torque levels.

Some people also think that torque management always means reduced straight-line acceleration, but I think that oversimplifies. Properly programmed, torque management actually lets the shift happen much faster so what you lose by shutting down the fuel for a few milliseconds, you can make up by nearly eliminating the time interval when the clutches are slipping at all.

 

[dailydriver]

Originally Posted By: 440Magnum
Some people also think that torque management always means reduced straight-line acceleration, but I think that oversimplifies. Properly programmed, torque management actually lets the shift happen much faster so what you lose by shutting down the fuel for a few milliseconds, you can make up by nearly eliminating the time interval when the clutches are slipping at all.


True, but still some tuners of drag raced street(ish) cars, still with their stock (but sometimes rebuilt for high power handling), modern slushboxes try to 'write out' all of, or at least as much of, the torque mgt. as they can.

 

[Vikas]

Is it bad NOT to WOT your car? I don't remember ever WOT'ng my car. There are couple of reasons for it. It has adequate power without mashing the pedal and secondly it will bog down if I open the throttle all the way.

During most of my driving the TPS is staying under 15% and very occasionally will reach 35% if I do quick 80-95 mph run without downshifting.

At least once a week, I will go close to redline on 1-2 shift but that's about it.

- Vikas

 

[ueberooo]

Most gasoline cars run at peak efficiency near the wide open throttle, but not quite at 100% efficiency. (You can do a google images and wikipedia search for brake specific fuel consumption to read up on this subject). For most gasoline engines (except modern direct injection) though, anything from 50% to 95% WOT should be pretty efficient. Idle on my car is about 33% WOT.

Assuming the above is correct, that is 33.33% manifold pressure at idle, this means (through the ideal gas law and the fact that fuel to air ratio is fixed) that my engine uses 3 times the amount of fuel as in idle, per cycle of the engine, when I floor the engine (run at WOT).

I installed a manifold vacuum gauge in order to be able to read the level of throttle--where 100% is the maximal amount of air (and thus fuel, since the fuel air ratio is about fixed) per revolution of the engine. On most modern cars (OBD 2 and whatever it is these days) your computer may be able to tell you or an add on like ScanGauge would. There are two ways I've seen it done: either read the manifold vacuum or the fuel injector duty ratio.

 

[BobFout]

Originally Posted By: Vikas
Is it bad NOT to WOT your car? I don't remember ever WOT'ng my car. There are couple of reasons for it. It has adequate power without mashing the pedal and secondly it will bog down if I open the throttle all the way.

During most of my driving the TPS is staying under 15% and very occasionally will reach 35% if I do quick 80-95 mph run without downshifting.

At least once a week, I will go close to redline on 1-2 shift but that's about it.

- Vikas


There's either something mechanically wrong, or that's evidence of why babied cars develop issues. [bogging down at WOT]

Ever seen a gas car soot? All that [censored] is built up, then when you finally do "GO" it's burned off and expelled.

 

[SteveSRT8]

Originally Posted By: dailydriver
Originally Posted By: 440Magnum
Some people also think that torque management always means reduced straight-line acceleration, but I think that oversimplifies. Properly programmed, torque management actually lets the shift happen much faster so what you lose by shutting down the fuel for a few milliseconds, you can make up by nearly eliminating the time interval when the clutches are slipping at all.


True, but still some tuners of drag raced street(ish) cars, still with their stock (but sometimes rebuilt for high power handling), modern slushboxes try to 'write out' all of, or at least as much of, the torque mgt. as they can.

This is very true but only on certain platforms. You cannot simply say this applies to EVERY automatic because it doesn't.

My car has run identical quarter mile times same day same track with both very aggressive shift programs (which chirp the 1-2 and the 2-3 shifts) and the original stock shift that won't even spill your coffee!

So some manufacturers have worked it out. But my Silverado lops off almost 3 tenths just by shifting harder and more quickly with an aftermarket program.

I'm sure there are many different strategies at work here.

 

[dailydriver]

Originally Posted By: SteveSRT8
Originally Posted By: dailydriver
Originally Posted By: 440Magnum
Some people also think that torque management always means reduced straight-line acceleration, but I think that oversimplifies. Properly programmed, torque management actually lets the shift happen much faster so what you lose by shutting down the fuel for a few milliseconds, you can make up by nearly eliminating the time interval when the clutches are slipping at all.


True, but still some tuners of drag raced street(ish) cars, still with their stock (but sometimes rebuilt for high power handling), modern slushboxes try to 'write out' all of, or at least as much of, the torque mgt. as they can.

This is very true but only on certain platforms. You cannot simply say this applies to EVERY automatic because it doesn't.

My car has run identical quarter mile times same day same track with both very aggressive shift programs (which chirp the 1-2 and the 2-3 shifts) and the original stock shift that won't even spill your coffee!

So some manufacturers have worked it out. But my Silverado lops off almost 3 tenths just by shifting harder and more quickly with an aftermarket program.

I'm sure there are many different strategies at work here.


Yes, I was inferring mostly GM performance-oriented products since that is what I have the most experience with/knowledge of.

 

[k24a4]

Originally Posted By: buster
Why type of engine stress does an engine go through when you bring the rpms up near redline? I 've read it's a good thing to do now and then, but that could be an old myth. Clearing out deposits/carbon buildup was one reason it was supposed to be good.


Buster, why do you ask? Do you reline the Accord? Any issues so far?

 

[lexus114]

I dont do it. Never have. No need to I guess.

 

[morris]

redline? been driving sense 1965. about 12 different cars/trucks. i have redlined each, but not hold high rpm very long, but not a lot. no trouble. my mistreatment was different things. but when the tires spin let off the pedal. i have tryed to use oil a little heavyer then most, but dont go to far.