Old School Says Don't Rev Engine

[bushbean]

Query: Is reving the engine while not in gear by jabbing the gas pedal bad?

My pop says he was taught back in the old days that that was bad for the engine and that reving the engine to high RPM while not in gear is generally bad too. However, he doesn't know why. An old wife's tale, or is there some truth behind this?

[Cheeseburger]

Honda's are reving happy engines

[MessyHonda]

thoes problems are only in american V8s....this guy i went to school with blew up his GMC engine like that....by reving it to like 5k and bringing it down....he did it on 86? and the engine took a crap.

[Oldblueaccord]

Crank flex.

On/off free reving makes the crank flex in the block. Prolly not have to worry to much on Honda's but there is no reason to d it alot.

wp

[2ndGenGuy]

No it won't hurt any engine. That doesn't even make any sense. It's designed to spin up to a certain point. Why would it matter if it's a V8 or a 4 banger?

I'm going to say no unless someone can find some real reason why it's true.

EDIT: The crank flex thing got in just before I posted.

About that though, why would the crank flex more just because the car is in neutral? Most cars engines still have the resistance of the flywheel on it (and quite a heavy resistance at that). And if there was load on the engine, the resistance would cause more flex than if there was no load on the engine if you ask me...

[Hans]

I think that reving the engine is fine as long as you don't go up to high and as long as the rev is smooth. I believe that it will cause premature wear on your engine, but too much of anything generally leads to failure. If you constantly punch the gas and jolt the engine it will def tear it up quickly.

[2ndGenGuy]

I think that reving the engine is fine as long as you don't go up to high and as long as the rev is smooth. I believe that it will cause premature wear on your engine, but too much of anything generally leads to failure. If you constantly punch the gas and jolt the engine it will def tear it up quickly.

+1 Agreed!

[bushbean]

Why do racers rev their engine up and down just before starting? At least, that's what I see in Hollywood movies all the time.

[Ichiban]

It doesn't make sense that a crank would flex more under no-load situations than under a load situation, given both occur within the normal operating range of the engine.

[Blizzard]

Why do racers rev their engine up and down just before starting? At least, that's what I see in Hollywood movies all the time.

Clears the plugs.



Far as the rest of this. Reving the engine out of gear isnt any diffrent than reving it in gear so long as you dont over rev it.
Reving it and droping it in gear on an automatic is bad.

[Oldblueaccord]

I just wrote a 3 parargragh reply that got lost .....
so to make it short at idle your ging from 1k to 5k in less then a second where as under load even in 1st it takes much longer and the drop is much less.

Domestic motor in general were not balanced.


wp

[Hans]

so to make it short at idle your ging from 1k to 5k in less then a second where as under load even in 1st it takes much longer and the drop is much less.

wp

Makes a lot of sense.

[88Accord-DX]

Most of the reason American engines are lower reving is because of typical American driving habits. We don't like the sound and vibrations associated with high revs and we do like torque. Hell, most Americans don't even like to shift gears and thats another reason why we need engines that have more torque, to feed the energy sapping automatic transmission. Torque is created by having a longer stroke and there are limitations on piston speeds and rotational speeds involved with really long strokes having to do with the inertia of the engine components. Americans drive these types of engines because we can. The rest of the world uses smaller higher reving more efficient engines because their gas costs more.

Engines like in your parents van are large displacement engines. They make their power by the tried and true method of having more room in the combustion chamber for the fuel/air package. More package more power. The old saying goes "there ain't no replacement for displacement." These types of engines typicaly have more torque due to a longer stroke required to get that displacement and still get a compact engine size and effiecent fuel burn as well as make American buyers happy. These engines deliver the classic american hot rod experience. Step on the gas and your head snaps back. We like that.

Having said that, the down side of these engines are that they are big and heavy, and generally not as efficient as smaller high reving engines. (all things equal regarding aspiration and construction materials) A smaller 4 cylinder high reving engine is going to produce more HP to it's weight than a comparably equiped V8.

It all comes down to power to weight ratio. Of course you can modify Cameros and Mustangs with even bigger power plants, but you will give up handling. In the case of Nascar you'll notice that while these bigger cars also use V8 engines, and can handle well, those engines are operating at very high RPMs. In general with engineering, if you can operate a system at a higher freqency then you improve efficiency.

[Hans]

[2oodoor]

Just Say No to Reving Engines in neutral !!!
Sure a little reving , controled, sensable... won't make your crank push the pistons out the head. BUT keep in mind there is a tendency to overrev because the engine is not loaded, and all sorts of damage can occur from damaging accessories (ie water pump, alternator, etc.) to spinning rod bearings, fatiguing valve springs, any number of things.
Another example to compare by is AC electric motors, eash one has a load rating. This is accomplished by using an amp probe on the source wire(s) and running the motor with a certain amount of load stated in the specs, a certain amp draw to rpm. If you don't have that correct (too little load or too much) the motor will shortley burn up. Not quite the same I know but there is a reason to the science of that, resistance/friction vs energy /time (current) or combustion in a car engine.. vs excessive energy without a place to go.

Do they measure torque and horsepower on engines by hooking up instruments and letter her rip at neutral... hmmmm in that case you could have a HP guage on your dash.

[Tomisimo]

About thet Lazy American V8. There are no spinn happy engines.
On the ather side of the world, in Germany, they produce V8's with 32valves. F.eks. AUDI and Mercedes. Engines thet produce lots of power with out forsed induktion. In average 330HP to 500HP... Americans stil have to lern how to build a proper engine.

Well, this is how i see it.

[bushbean]

About thet Lazy American V8. There are no spinn happy engines.
On the ather side of the world, in Germany, they produce V8's with 32valves. F.eks. AUDI and Mercedes. Engines thet produce lots of power with out forsed induktion. In average 330HP to 500HP... Americans stil have to lern how to build a proper engine.
Well, this is how i see it.

The Germans can build awesome V8 engines, but German machines are outrageously expensive. Only the elites can afford them. Americans can build awesome V8, too, but we choose not to for business reasons. I mean, why spend all that money on R&D for an engine that only a few can afford. The Japanese are even smarter business-wise. Most of them chose not to build V8 at all.

[2oodoor]

The Germans can build awesome V8 engines, but German machines are outrageously expensive. Only the elites can afford them. Americans can build awesome V8, too, but we choose not to for business reasons. I mean, why spend all that money on R&D for an engine that only a few can afford. The Japanese are even smarter business-wise. Most of them chose not to build V8 at all.

hey man, the Ford 4.6 liter OHC v8 engine is an awesome base engine, and there are many hi po versions of that design.
Cadillac NorthStar is another one, though not as reliable IMO.

[Estimated Prophet]

Do they measure torque and horsepower on engines by hooking up instruments and letter her rip at neutral... hmmmm in that case you could have a HP guage on your dash.

Isn't this how hp/tq is measured at the crank?

[lostforawhile]

some cars have a torque horepower gauge on the dash,the computer knows exactly how much power the engine will produce under certain parameters,these didn't work on old school engines,because the fuel wasn't as well metered. with modern fuel injection the computer already knows the exact displacment of the engine,the rpm,and every other factor you can think of. it can calculate horsepower exactly. they also measure load on the engine to figure in this equasion,it's all math. as far as hondas hurting to rev the engine,the only ones i've heard damage too,were ricers sitting in parking lots just reving the engine and bouncing it off the rev limiter. some of the earlier honda engines,like the 1200 civic engine,actually had a full stud girdle like a drag car. crank flex didn't exist in those engines. remember these cars,and every other honda were designed down from bikes, i think Mr. Honda knew a thing or two about building a high reving engine.

[2ndGenGuy]

Most of the reason American engines are lower reving is because of typical American driving habits. We don't like the sound and vibrations associated with high revs and we do like torque. Hell, most Americans don't even like to shift gears and thats another reason why we need engines that have more torque, to feed the energy sapping automatic transmission. Torque is created by having a longer stroke and there are limitations on piston speeds and rotational speeds involved with really long strokes having to do with the inertia of the engine components. Americans drive these types of engines because we can. The rest of the world uses smaller higher reving more efficient engines because their gas costs more.
Engines like in your parents van are large displacement engines. They make their power by the tried and true method of having more room in the combustion chamber for the fuel/air package. More package more power. The old saying goes "there ain't no replacement for displacement." These types of engines typicaly have more torque due to a longer stroke required to get that displacement and still get a compact engine size and effiecent fuel burn as well as make American buyers happy. These engines deliver the classic american hot rod experience. Step on the gas and your head snaps back. We like that.
Having said that, the down side of these engines are that they are big and heavy, and generally not as efficient as smaller high reving engines. (all things equal regarding aspiration and construction materials) A smaller 4 cylinder high reving engine is going to produce more HP to it's weight than a comparably equiped V8.
It all comes down to power to weight ratio. Of course you can modify Cameros and Mustangs with even bigger power plants, but you will give up handling. In the case of Nascar you'll notice that while these bigger cars also use V8 engines, and can handle well, those engines are operating at very high RPMs. In general with engineering, if you can operate a system at a higher freqency then you improve efficiency.

I already posted a reply to this in another thread, but here's how I see it:

"I don't know how true that is. How do you define efficent? Is it HP per liter? HP per liter is a mechanical/technological measurement, not an overall car performance trait. What relevancy does that have when it comes to performance of a car? Overall power to weight isn't going to be affected as much with an engine block as other weight reduction methods in a car...

Take a look at the Corvette. The car has gobs of toruqe, 500hp, and still gets 28mpg. Sounds pretty damn efficent to me. One cam, and pushrod-driven valves...

Also, the C6R has gobs of torque compared to most LeMans cars and tends to be a race winner. Also, look at the turbo diesel Audi R10 LeMans car. It also is a huge race winner. Torque seems to be the biggest factor. Waiting for your engine to wind up before you get power can be a killer."

[2oodoor]

Isn't this how hp/tq is measured at the crank?

not exactly, engine only dynos do load the engine.
HP guage ? Yes a modern car with a full body and drivetrain computer could measure hp to a degree but some of the parimeters are built in, the engineers already know what the vehicle will do.

[Blkblurr]

Older engines can be damaged by neutral reving because they don't have fuel cotoffs when redlining like the new ones do. There is nothing to limit the rpms as you do when in gear and moving. Age is another issue with reving in neutral. agian no limit to rpms and loose engines fly apart.

[race12001]

Why do racers rev their engine up and down just before starting? At least, that's what I see in Hollywood movies all the time.

also if they have purge n20 in then they make sure the get most of it out cause if they don then it will spit back through the carb

[Tomisimo]

The Germans can build awesome V8 engines, but German machines are outrageously expensive. Only the elites can afford them. Americans can build awesome V8, too, but we choose not to for business reasons. I mean, why spend all that money on R&D for an engine that only a few can afford. The Japanese are even smarter business-wise. Most of them chose not to build V8 at all.

You say fo business reasons. Thet is just stupid. One example.
Ford have now lounched a GT500 version of their Mustang. Nice car to look at. Sure. But Why put an extra power with out upgradeng the suspention?
They say it will cost them an 500$ extra.
This is the reason why Am-Motors are lazy. Kopitalism