To rev or not to rev?

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Nightmage82

Nightmage82

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every race in gt3 starts with all the computer players constantly revving their engines VERY annoyingly. is this the best treatment for ur engine? (i mean in real life, clearly in gt3 it makes little difference) but if u are waiting for say a race, would it be better just to floor it and watch the rev needle bounce off the redline, let the engine idle until the last moment, or do what the gt3 people do, REV...REV...REV...REV.... etc?

(oh and as an asside, what exactly happens when u floor it and the revs reach a certain point then roll back, is the engine misfiring or is something twisting to far or what? why doesnt it just stay maxed out at a constant rpm?)

hope thats all clear for anyone who has info :D
 
I dunno about everything else, but to answer this:
Originally posted by Nightmage82
(oh and as an asside, what exactly happens when u floor it and the revs reach a certain point then roll back, is the engine misfiring or is something twisting to far or what? why doesnt it just stay maxed out at a constant rpm?)
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I don't know about real life, but in GT3 that almost always happens because of wheelspin... the wheels won't have very much traction, will spin freely as you floor it, then as you gain momentum the wheels will finally "catch" onto the pavement and slow the engine down. It's kind of hard to explain, but basically the revs start dropping when your wheels regain traction.
 
Well, Sage, basically, when the wheels gain the traction, the engine 'downrevs'*i kno it's very confusing right now*

Ok, so when you start right of the line with the gas floored, the car magically shifts into one and you're off. Since lower gears have alot of torque, the engine will continue to speed up. Sure, you can accelerate, but not very fast. IMO the reason that the cars rev like that in GT3 is just to simuilate real life starts. :confused: I could be wrong.

And, the reason the needle doesn't stay in one place you ask? When the accelerate is floored, there is combustion. If the engine was unbreakable, a car would go as fast as it wants in first gear. However, engines CAN be blown up by too many internal combustions. So how does it tie back to the needle bouncing? well, there is a fuel shutoff in the tach. As soon as you hit that point, the fuel supply gets shut off for a brief period then turned back on. They do this so that you do not go over the point of the fuel-shutoff. Any RPM past fuel-shutoff will severely damage or blow up the engine.
 
All(I think) cars have rev limiters. When you hit the rev limiter, several things will happen depending on the car:
1.revs will bounce up and down a little
2.CPU will cut the throttle/fuel to the engine to cause it to not rev up that high/reduce damage.
3.engine will just stay at high RPM constently till a plume of smoke erupts from the engine and either the engine dies, or you have to let off cause you are breathing in smoke and pass out. :)

On an episode of My Classic Car several months ago, they had an engine burn up contest/test, and they shows to my horror, a 323 like mine going "Vinginginging ing" and eventually there was "inging yeeiengyeaarrrrrrrerereerrrshhhhhhhhhhhhhhhhhhhhhh" and smoke and some poping(hoses probably, and possibly the cylinder head breaking or throwing the crank shaft out the side.

As for is it good to rev before a race or just in plain driving, really, yes. If a car sits for a while, revving it(not all the way up, which isn't good for any car) can break apart the buildups in the engine, sorta clearing it out. In normal driving, it can be beneficial to make high RPM runs/full throttle acceleration. On rotary viehicles(though probably not on the RX-8), it is nearly a necessity to rev the engine to high RPM every so often, and if you don't, they can actually lose power and run worse.

Luckily for me, the 323 isn't fast and to get on the highway a lot of times I go flat out from 2nd through 3rd and it runs great.

What's funny was what happened with my dad's Probe GT. We bought it from an ex-nieghbor, and it wasn't running. My dad got it running, and it ran like crap. My uncle came over to see it, and him, my dad(driving), my bro, and I piled into the car and drove it around going flat out(not constently ofcourse) and letting the engine up to the red line(not rev limiter, though after we got home, my uncle took me for a ride in it and shifted into 1st at about 35mph causing the engine to go up to about 7,500rpm, 500rpm above the red line, though it never hit a limiter)and we noticed an exceptional increase in performance in the matter of 10-15 mins of driving through the nieghborhood(at some illegal speeds and trying to get it to skid since the wide tires were nearly brand new before my dad bought it(before the car stopped running, the guy put tires on it, drove it about 20 miles on the new tires, parked it, and never got it going) and they seemed to grip like mad(until, as we found out, you get on snow)). And now, with 200K+ miles on the original V6, it runs great.
 
Not All Cars Have Rev Limiters

Just before the green light, slowly bring you RPMs to a RESONABLE launch power.

It's not good to sit there and either 1 hit and bounce on your limiter. 2 no reason to constanly rev your engine before a race.

And don't listen to what anyone says about Double Clutching, it dosnt always help.
 
Every car engine has a limit to where it will rev too, this is limited by the internals. But manufacturers put in the fuel cut/rev limiter so you can't reach this point, and damage your engine.
 
Originally posted by Larzzon
Please don`t flame me,but what exactly is double clutching?
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I've got no idea, I've heard many different examples of it...maybe one of the 'smarter' members can enlighten us on it.
 
what you see in GT3 is a rev limiter

lots of cars havent got rev limiters (mostly non fuel injected cars)
but some also have a point where they dont rev any higher
because of many possible reasons eg, fuel supply is not good enough, ignition doesnt keep or have problem with valve train like valve bounce

i once had a 6 cylinder car that the engine couldnt get above 5500rpm due to the ignition

double clutching has been explained on these forums many times

most people know double clutching as shifting to neutral releasing the clutch bring the revs up (quickly) and then shift into gear.
double clutching is mostly know for performance driving but also is used for other reasons, like some old trucks require double clutching to shift without grinding gears(bringing up the rev is not required)
 
i wrote a post about it here
if u look on the previous page of that thread i think there is also another post by me about it. that will explain double clutching when ur driving, i guess to help you launch u just let the transmission spin up so there's no major jerk when u finally drop the clutch with the gear in place.

back to the topic,
do ALL cars therefore have rev limiters? even the old-skool ones from the 60's? if not would they just let the needle rise up to the redline and stay there, GRADUALLY creeping up and up until the engine exploded?

as for revving the engine, there seem to be conflicting viewpoints on this subject. when my dad starts the car from cold he always likes to blip the throttle constantly letting the revs rise and fall, whereas i just hit the pedal down once so the revs reach about 1200 rpm and let it stay there for about 30 seconds (normal idle is around 700) though in our particular car if you don't do one of those the engine will cut out when its cold :D. im just wondering which is better for the engine? does it want a constant medium level speedup or does it want to get blipped all the time up to about 2500-3000 rpm?

clearly im not talking about performance cars here but the same principle would apply right?
 
cars have chokes ethier manual or auto chokes they shouldnt need you reving it

cars can explode from over revving aswell
 
Originally posted by Nightmage82
as for revving the engine, there seem to be conflicting viewpoints on this subject. when my dad starts the car from cold he always likes to blip the throttle constantly letting the revs rise and fall, whereas i just hit the pedal down once so the revs reach about 1200 rpm and let it stay there for about 30 seconds (normal idle is around 700) though in our particular car if you don't do one of those the engine will cut out when its cold :D. im just wondering which is better for the engine? does it want a constant medium level speedup or does it want to get blipped all the time up to about 2500-3000 rpm?
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I usually get it to sit at a fairly even RPM.

I have heard a reason why revving it when cold is a bad idea, but I can't seem to remember it. :irked:
 
i keep the revs nice and constant instead of blipping them
 
Originally posted by Larzzon
Please don`t flame me,but what exactly is double clutching?
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Instead of CLUTCH IN > SHIFT > CLUTCH OUT, CLUTCH IN > BACK TO NEUTRAL > CLUTCH OUT > REV (optional) > CLUTCH IN > SHIFT > CLUTCH OUT.
 
Originally posted by Cobraboy
I usually get it to sit at a fairly even RPM.

I have heard a reason why revving it when cold is a bad idea, but I can't seem to remember it. :irked:
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Revving the engine when cold is a bad idea because colder oil has higher viscosity (i.e. more gloopy) and is therefore not so efficient as a lubricant.

Revving the engine immediately on startup is a VERY bad idea because the oil has dropped out of the cylinder head, and so the cams, valves etc have no lubrication.
 
Originally posted by GilesGuthrie
Revving the engine when cold is a bad idea because colder oil has higher viscosity (i.e. more gloopy) and is therefore not so efficient as a lubricant.

Revving the engine immediately on startup is a VERY bad idea because the oil has dropped out of the cylinder head, and so the cams, valves etc have no lubrication.
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WOMEN!!! Giles!!! WOMEN!!!

My mother always revs her engine on start-up, she thinks the engine explodes otherwise or something. And so does my lame sister. :irked:

I hate that.
 
Well I've noticed that a lot of cars, when started, will stay at slightly above idle RPM without you doing anything, untill you kick it down by tapping the gas or shifting into a drive gear(Drive or Reverse, or any gear in a manuel car.

Also, on turbo cars(as seen on my bro's MX-6 and Probe GT, though it aplies to most turbos), it's very bad to rev upon starting. It even says on the visor, "Do not race engine shortly after starting" or something like that. Also, you have to let the car idle for a minute or so before driving off, and you don't let the turbo boost right after you drive off, for several minutes untill the engine warms up.

As for double clutching, I don't see a benefit. You can just push in the clutch with the gas, shift, and let off the clutch and get the same effect in a lot less time. Either way, if your clutch is warn you would be much better off just shifting and then hitting the gas once in gear. My dad has to do that in his Probe cause going from 1st to 2nd flat out, if he shifts, it'll stay right at the redline for a bit then drop off slowly as the clutch gets a grip on it. :)
 
OK, this subject has gone pretty far afield. I will try to help clear some of it up.

1) The race cars in GT3 rev like that because racecars don't idle well. In order to tune for maximum high-rev HP, they sacrifice smooth low end running. A 2.0-litre touring car race engine may make 400 HP, but it will not idle below about 2000 rpm. On a street car, there is no reason to pulse-rev the throttle like that, particularly not on a fuel-injected car. For all the reasons stated above, you also shouldn't dirve your car hard while it is cold.

2) Double-clutching is a throwback to 40 years ago and there is almost never a reason to use it these days. As sn00pie said, the technique is to let the clutch out while the car is in neutral, blip the throttle, then put it back in to complete the shift. The reason for this was to get the output shaft and the input shaft spinning at approximately the same speed before engaging the gears. This was necessary in the old days before synchromesh transmissions. However, every manual car transmission made since about 1970 has synchronizers that do this for you, and come into play automatically as you edge the lever toward the correct gear. In the early days of synchros, and with very high-rpm/power applications, it was possible to wear the synchros or break them, so under some conditions it may still be advisable to double-clutch, but 99.9% of us will never see them unless we drive an old MG or a dump truck on a regular basis.

This is not to be confused with heel-and-toe shifting, where you blip the throttle with the clutch in while braking as part of a single-clutching downshift. This is done to ease stress on the driveline and to avoid upsetting chassis balance.

3) Rev limiters really only came into being with the advent of electronic ignition and fuel injection. Mechanical governors existed before then but were not common in automotive applications. The "bouncing tach" phenomenon in GT3 is representing the rev limiter, where the engine manager cuts off the fuel supply to prevent the driver from overrevving the engine and damaging it. Once revs fall to a safe level, fuel is restored and the car accelerates again. in a real car, this only works when accelerating - if you stuff the car into too low a gear at too high a speed, the wheels will overdrive the engine and no rev limiter in the world will save it.

Drag racers often use what's called a "two-step" limiter or "stutter box". This is a second rev limiter that can be set by the user to the desired launch revs, say 4000 rpm. Holding a button down activates this limiter and holds the car at 4000 rpm even with the throttle floored. When the tree drops and the driver launches, he lets go of the button, allowing the car to rev to peak for the run.
 
Originally posted by neon_duke

Double-clutching is a throwback to 40 years ago and there is almost never a reason to use it these days. As sn00pie said, the technique is to let the clutch out while the car is in neutral, blip the throttle, then put it back in to complete the shift. The reason for this was to get the output shaft and the input shaft spinning at approximately the same speed before engaging the gears. This was necessary in the old days before synchromesh transmissions. However, every manual car transmission made since about 1970 has synchronizers that do this for you, and come into play automatically as you edge the lever toward the correct gear. In the early days of synchros, and with very high-rpm/power applications, it was possible to wear the synchros or break them, so under some conditions it may still be advisable to double-clutch, but 99.9% of us will never see them unless we drive an old MG or a dump truck on a regular basis.
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Granny shiftin' not double clutchin' like you should !
 
thanks for that post neon duke, lol at vin in the post after :P

my car is old and the synchro is worn and double clutching helps very much in the lower (more worn) gears. double clutching from 4th to third at speeds also makes stops the car lurching forward if im driving too fast for that gear, however maybe im just speeding up the driveline like you said rather than the transmission.

and finally,
Originally posted by VIPERGTSR01
cars have chokes ethier manual or auto chokes they shouldnt need you reving it

cars can explode from over revving aswell
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point one, my car is old but has neither a manual nor automatic choke. it may have had an automatic choke once but its most definitely dead now. if you start it but don't push ur foot half way down the accelerator then use cunning foot movments to keep it running without over revving the engine, it will die. this isn't always as easy as it sounds since i don't have a rev meter either :P

oh and not that im one for correcting people, but i think u mean ENGINES can explode from over revving :D i'd hate to be killed carbomb style if my girlfriend decided to have a heavy foot one day hehe
 
yeah i meant the engine

older cars that have auto chokes(pre fuel injection) the choke usually play up and dont work

some older trucks even when new required double clucthing
i believe double clutching in cars pointless and people do it to jsut show off a bit
 

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