RPM range good? bad? same?

[wicked1981]

So I was in my brothers 04 Grand Prix last night and noticed his rpm's only reach 7,000 in the Vibe its up to 8,000. Question I have is does that make a difference in performance? I seen other cars that go to 10,000 does it help acceleration? Does it help anything? Does it matter?

[satur9]

the numbers on the tach my say that but most cars dont actually rev over 9000 rpm (race cars and crotch rockets can. this is mostly depended on engine powerband, gearing and a whole lot of other crap. but to put it simply. yes the higher you can rev the more horsepower you can make(in certain engines)

[Faultline]

It seems like like on a lot of dyno's, the peak HP is not always at the peak rpm...but I would have to admit, that making a motor scream at the high rpm is way fun!!....I am even disappointed that my 1zz cuts off at 6400rpm, when the same motor in the celica at least goes to 7000rpms...I am always thinking about how to change this cheaply. ... plus, motors swallow f/i better at the high revs...I do envy the 2zz's ability to make it into 8k range.

[wicked1981]

Quote, originally posted by Faultline »It seems like like on a lot of dyno's, the peak HP is not always at the peak rpm...but I would have to admit, that making a motor scream at the high rpm is way fun!!....I am even disappointed that my 1zz cuts off at 6400rpm, when the same motor in the celica at least goes to 7000rpms...I am always thinking about how to change this cheaply. ... plus, motors swallow f/i better at the high revs...I do envy the 2zz's ability to make it into 8k range. 2nd question is: Would a paddle shifter help the 1zz engine go higher before shifting? Im no mechanic so Im not sure how a padle shifter works hey I didnt even know what it was till about 2 weeks ago

[wicked1981]

Does the 1zz stick make it to the 8,000 range? Or just te 2zz?

[satur9]

the 1zz redlines around 6500rpm.paddle shift is seen lately in electronically contol auto. where you can let the car shift by itself or press a button to shift.on some cars it helps because the computer will shift long before redline.but you can take it to redline if you manually shift with the buttons or stick(autosticks).i personally think most of these systems are gimmick.because they still dont offer the true performance of a manual,but they are a little fun. the true paddle shifters come off cars with sequential trany that cost more than you car,like high end ferraries

[nismo]

If you think about it, there is more sense in having a high reving motor. For one, less shifting involved when in a drag race. And for all who have the 2zz motor, it makes it even better for them because I'm pretty sure your redline is something like 7300. The Honda S2000 is like 8500. So, it makes more sense for people with V-tec and Lift because the longer they can stay in lift, the better. When you drag race, end of first gear is 7300 for the GT and once you drop it into 2nd, u're right back in lift, so you never really escape lift at all. That is why many of these Honda vehicles rev so high.Inder

[Kissfan79]

You can go all the way up to about 8100-8200 with the 2zz engine. In first, it shoots from 6200 where it hits lift to 8100 in a blink of an eye.Jim

[futseal04]

Most of the time it doesn't make any sense to run to redline in anything over 2nd gear. IF you look at HP graphs, then you will see that HP peaks before redline and then falls off. So especially in the upper rev ranges, all you do is make more noise than power. So as a rule of thumb, you usually want to shift about 300 or so RPM past your HP peak. The engine in the GT's can rev higher because of a shorter stroke (less up and down movement), and stronger valve springs (no valve float). Our motors are what they call "undersquare", which is where the Stroke is a bigger number than the Bore. In motorcycle applications, you usually see a bore/stroke relationship of about 1.5:1 (i think...don't quote me on that). With the shorter stroke comes less torque (torque~ Length*force) and that is why they have such deep gearing (i.e. freeway RPM's of 5-6000). Oversquare is then the Bore is bigger than the Stroke. This is usually found in anything V6 and bigger. So with a longer stroke you make more torque (which you can feel anytime you press the gas pedal), but are limited in the amount of RPM's you can achieve.Remember also that HP is merely a mathematical number that shows work over time. (HP=Torque*RPM/5250). So alot of manufacturers get higher HP by making an engine that will rev higher.

[Smokin' Rubber]

I dunno the whole point of shifting at the red line is so that when you do in fact shift, the RPM's only drop to the the bottom of lift, where as if you shift before redline you are more like to drop below lift which costs you a lot of accel. Even if you are past peak HP at 8,200 RPM most of the time you still have much better accel than if the RPM's are below 6,000 (which is around where the second cam shaft kicks in)

[goodvibe]

Our GT motors spin a about 3200 rpm at 70 mph not 5k to 6k and HP is actually the # that matters most since it represents how effectively the torque is utilized. It is right to tune for maximum torque at all rpm but the corresponding hp #s will tell you more about a motors character. On your 1zz it makes as much torque at 3500 rpm as it does at 5500 rpm. It will pull much harder at 5500 rpm because the HP is higher and better represents the power that can be supplied to the wheels. Shifting the 2zz at or past redline works because there is still much more hp at that extreme than at anything under 6400rpm which seems to be the rpm to hit on shift if you can.

[MadBill]

Ideally for maximum performance, given sufficient mechanical durability, good valve springs, etc., you would shift at the RPM above the power peak at which the power had dropped off to the same level as what the engine would make in the next gear at the same vehicle speed. E.g., if your engine made 160 HP @ 7,000 RPM and you shifted at @ 8,000 where it made 140 HP, then after the shift, say at 5,500 RPM, you should also be making 140 HP on the rising portion of the curve. This way, you maintain the "maximum area under the curve" and optimize acceleration. You can work these points out for each gear by referring to a power curve of your engine and a chart of the gear ratios. (details upon request)The reason high performance engines rev higher is that an engine's power is limited by the amount of air it can take in and without a supercharger or turbo this is limited to a maximum of about 95 -105% of the displacement, mulitplied by one half the RPM (since each induction stroke occurs every second revolution) Therefore, if you can double the RPM you can theoretically double the air flow and thus the power. Of course it's pretty difficult to deliver the same amount of air into each cylinder in half the time, so a high RPM engine needs big ports and valves plus cams, exhaust, etc. tuned to the higher speed. Once the engine is set up for this high RPM, it's usually a bit of a dog at low speed, which is where variable intakes, VVTL-i, etc. come in, to try and match both the low and high speed needs of the engine.

[Smokin' Rubber]

Beautifully put Bill now if only we could get a third cam shaft for double lift lol that would be wicked wouldn't it?

[goodvibe]

I couldn't have said it better madbill, and I didn't.

[futseal04]

IF you look at a HP/Torque graph, then you will see that under most circumstances, reving way past redline is not beneficial. Sure, your engine will be making the same 140 at 5500/8000, but the difference lies in that above 7000, you are making less power the more you rev, whereas at 5500, you are climbing into the powerband. Now, on a GT, i can see prolonging a shift to keep the engine in lift, but 99% of everyone else out there doesn't have lift. For example, my 96 cobra made 330HP@ 5800 RPM. Redline was at 6800, rev limiter at 7200. By shifting at 6000 instead at redline or 7200, i shaved .3-.4 sec off of a quarter mile time. I ran it to redline in 3rd, because 6000 in 3rd was about 105, and i wasn't quite through the traps yet, so i ran it to about 6200 to save a long gear shift into 4th.So it really depends on the application. On these high winding 4 bangers with lift, then i would want to keep it in lift by shifting higher. But for a base, I would shift about 300 greater than peak HP.As for airflow, there are a lot of things to take into consideration...like head flow, intake volume, valve size, number of valves, cam lift and duration, etc. In other words.....too many variables.Also.....i thought intake was on every 4th event for a 4 stroke motor. intake, compression, expansion, exhaust. Each event has it's own stroke.......maybe it has just been too long......

[MadBill]

Quote, originally posted by futseal04 »Also.....i thought intake was on every 4th event for a 4 stroke motor. intake, compression, expansion, exhaust. Each event has it's own stroke.......maybe it has just been too long......Yes, intake is every 4th event in the complete cycle, but there are two strokes (one up, one down) per revolution, thus one intake stroke every two revolutions.

[wicked1981]

Quote, originally posted by Smokin' Rubber »Beautifully put Bill now if only we could get a third cam shaft for double lift lol that would be wicked wouldn't it?Yes really WICKED.

[MadBill]

Sort of a three-pronged attack, Wicked? (**looks at the trident Wicked's Avatar is holding**)

[Smokin' Rubber]

Hehe like the nice spikes in the tq/hp bands

[futseal04]

Yes, intake is every 4th event in the complete cycle, but there are two strokes (one up, one down) per revolution, thus one intake stroke every two revolutionsMan I have to clean out the cobwebs......