why does everyone want to spin the coyote up to 8000 plus?

[race4food]

When the peak power is almost always at 7500 ish why does everyone want to spin it up so high?
This seems like diminishing returns.

 

[Juice]

'Cause it can.

RPMs are like pounds of boost, the more the better!

My bike STARTS making real power at 7500!! (gsxr)

Any questions?

 

[JEWC_Motorsports]

Because when it shifts it stays in the best powerband. Mine shifts at 8200.

 

[tjm73]

May have something to do with where the revs drop to once the shift happens. Sometimes reving a few extra hundred before shifting drops the rpms where it needs to be to pull harder in the next gear.

 

[Midlife Crises]

What’s that old rule? Torque peek to Horse Power peek, that is the operating range to gear for.

 

[Dino Dino Bambino]

What’s that old rule? Torque peek to Horse Power peek, that is the operating range to gear for.

Yup, that's basically correct. Ideally you want to rev out each gear far enough to bring the engine near peak TQ rpm in the next gear. This almost always mean you'll rev out furthest in 1st gear due to the wider ratio gap between 1st & 2nd.

 

[xeninworx]

My 2006 Civic Si would redline to 8300 RPM. Good times.

 

[race4food]

Yup, that's basically correct. Ideally you want to rev out each gear far enough to bring the engine near peak TQ rpm in the next gear. This almost always mean you'll rev out furthest in 1st gear due to the wider ratio gap between 1st & 2nd.

Exactly which means shift at 7800-8000 tops. Then it drops back to peak power for the next gear. Now if it kept making power up to 8000 then sweet but even with cams and a CJ the power tops off at 7800

 

[eighty6gt]

You cut a slice of the peak on the hp graph and shift on either side of it to maximize area underneath. Nothing to do with torque.

Sometimes you can't do this, moving from a stop, wrong gear acceleration. A vehicle having strong torque characteristics just means it is able to make a lot of horsepower at unfavorable engine speeds.

If you shift where the engine will blow up after a little while, the ability to accelerate suddenly drops off dramatically. This is why I'd be conservative.

 

[Pentalab]

You cut a slice of the peak on the hp graph and shift on either side of it to maximize area underneath. Nothing to do with torque.

Sometimes you can't do this, moving from a stop, wrong gear acceleration. A vehicle having strong torque characteristics just means it is able to make a lot of horsepower at unfavorable engine speeds.

If you shift where the engine will blow up after a little while, the ability to accelerate suddenly drops off dramatically. This is why I'd be conservative.

Oh just get a blower and be done with it. Almost a flat tq curve.

 

[JEWC_Motorsports]

Exactly which means shift at 7800-8000 tops. Then it drops back to peak power for the next gear. Now if it kept making power up to 8000 then sweet but even with cams and a CJ the power tops off at 7800

Stock engine? Gotta be.....

 

[OX1]

I don't. In fact , when it was shifting @ 7300, I asked VMP for 7000 shifts and 7500 rev limit.
Still trapped 130.

 

[race4food]

Oh just get a blower and be done with it. Almost a flat tq curve.

This will be my next post, about the people who insist the answer to everything is boost. Just throw a blower on it and be done. Not everyone likes the noise, the extra vibrations, dealing with cheap gas and hot air in the summer, and some drive on a road course where boost is a liability.

 

[Midlife Crises]

Oh just get a blower and be done with it. Almost a flat tq curve

Even with a blower there will still be a torque peek and a horse power peek and the strongest performance is between those two points.

 

[OX1]

This will be my next post, about the people who insist the answer to everything is boost. Just throw a blower on it and be done. Not everyone likes the noise, the extra vibrations, dealing with cheap gas and hot air in the summer, and some drive on a road course where boost is a liability.

The initial install of my Roush with Phs 1 stock style airbox, Phs 3 pulley, and completely stock exh was stock quiet. No vibes (ever, maybe that's a centrifugal thing??) and no intake noise (with that stock type airbox). Even appears CARB approved (not technically with VMP tune).

On 93, trapped 121 and change @ almost 90 degrees out (and complete crap air) and 125 and change @ 45ish degrees. Nothing wrong with NA, but seems like a lot of work and most likely, an obnoxiously loud car to get where I am at. You also don't need to spin much over 7000.

Yes, I wouldn't use it on road course.

 

[eighty6gt]

Even with a blower there will still be a torque peek and a horse power peek and the strongest performance is between those two points.

False

Where are you getting this?

 

[Midlife Crises]

Where are you getting this?

Are you suggesting that Dino graphs don’t show a torque peek and a horse power peek or are you arguing that an engine should be operated above it’s HP peek?

 

[eighty6gt]

For fastest acceleration, absolutely it should be operated above the HP peak - unless the vehicle is equipped with a cvt transmission. Then it should operate at peak hp. Normally, the RPM's will transition from under to over the hp peak with the integrated area under the hp curve remaining as large a value as possible.

If you have a large ratio spread from 1-2 as my truck transmission has you'll rev the guts out of the engine in 1st. The shift points later on will change based on the ratio difference.

Horsepower has a unit that represents the ability to do work over time. 1hp = "the power necessary to lift a total mass of 33,000 pounds one foot in one minute."

Torque is only a measure of cylinder pressure. A potential to do work. Of course even though torque often drops off with higher rpm, can still do much more work because we take advantage of reducing gearing to harvest more power cycles.

 

[Midlife Crises]

Fascinating!

 

[Dino Dino Bambino]

I'll use my own car as an example to illustrate how it works but you can apply the same principle to any car. At the 6500rpm rev limit it puts down 246rwtq (304rwhp), peak TQ is 330 at 4400rpm, and peak HP is 314 @ 6100rpm. TR 3650 transmission gear ratios are 1st 3.38, 2nd 2.00, 3rd 1.32, 4th 1.00, 5th 0.68. This is how the rear wheel torque and rpm changes as I change from one gear to the next at maximum rpm.

1. 1st gear at 6500rpm = 42mph = 3800rpm in 2nd
The engine is well below peak TQ rpm when I shift into 2nd. I would either need to rev the engine out to 7000+rpm in 1st, or preferably have a numerically lower 1st gear ratio to reduce the ratio gap to 2nd and not have to rev 1st gear so high.

2. 2nd gear at 6500rpm = 71mph = 4300rpm in 3rd

2nd gear at 6500rpm = 246 × 2.00 = 492rwtq
3rd gear at 4300rpm = 329 × 1.32 = 434rwtq

Even though the engine is near peak TQ rpm in 3rd after the 2nd to 3rd upshift, I could still theoretically rev 2nd further than 6500rpm because it's putting down more rear wheel TQ due to the gear ratio multiplication.

3. 3rd gear at 6500rpm = 108mph = 4900rpm in 4th
Now the engine has gone past peak TQ rpm in 4th but let's look at the rear wheel torque:

3rd gear at 6500rpm = 246 × 1.32 = 325rwtq
4th gear at 4900rpm = 322 × 1.00 = 322rwtq

It would appear that an upshift from 3rd to 4th at 6500rpm is almost ideal.

4. 4th gear at 6500rpm = 143mph = 4400rpm in 5th

After the 4th to 5th upshift, the engine is bang on peak TQ rpm. However:

4th gear at 6500rpm = 246 × 1.00 = 246rwtq
5th gear at 4400rpm = 330 × 0.68 = 224rwtq

Again, it would appear that I would either need to rev the engine further than 6500rpm in 4th, or have a numerically higher 5th gear ratio to reduce the ratio gap.

As you can see, determining the optimum rpm to shift up gears is more complex than anyone realises. The critical determining factors are the shape of the torque curve and the transmission gear ratios. You could spend hours having fun playing around with the calculations, and determining which transmission ratios are ideally suited to your engine's torque curve. I've certainly discovered that for optimum performance, I could really do with a closer ratio 6-speed transmission.
You'll note that I deliberately omitted the 3.55 rear axle ratio in the rwtq multiplications because it doesn't change the end result.