Where is the point (RPM) of maximum acceleration

[A Atwood]

But, CVT systems are noted for their poor power transmission resulting in power losses of up to 50%. Now the correct ratios become even more important.

Understand that. I use the CVT transmission in discussions mostly to get my point across. If there was a good one available, Pro-Stock would use them.

My Kingquad has a CVT, but is a belt drive set up. I'm sure it is quite wasteful. The Honda has a CVT called the Hondamatic, and is not a belt drive. It has a lot of patents on it and is probably much more efficient.

ARN

[David Redszus]

David,
When I used 1.0 for my dyno correction I did not get the same results as you did. I just went back and check and that was because the parameter file I read in has a 2.2:1 rear ratio and not 2.11:1 A much smaller difference is power lose where you used 14% and I reduced power by 6% and took that result and reduced it by 8%.

► (100 * .94) * .92 = 86.48

With these adjustments made our numbers were about identical.

Stan[/quote]
Stan
Does that mean we are both correct or both wrong?

[Stan Weiss]

David,
When I used 1.0 for my dyno correction I did not get the same results as you did. I just went back and check and that was because the parameter file I read in has a 2.2:1 rear ratio and not 2.11:1 A much smaller difference is power lose where you used 14% and I reduced power by 6% and took that result and reduced it by 8%.

► (100 * .94) * .92 = 86.48

With these adjustments made our numbers were about identical.

Stan

Stan
Does that mean we are both correct or both wrong?

David,
For this parameter set we are both correct.

Stan

[Troy Patterson]

This is just a random graph I pulled up of a drag car launching and making a 1/8th mile pass which shows G-Force. This car was launched at 3000 RPM (with a 1050 on a 406 SBC) and shifted at 7000 RPM. That's 4000 RPM this engine is working.

I happen to know this engine makes peak torque at 5100 RPM with a different, smaller carburetor and peak horsepower at 7000 RPM. Interesting that this drag racer launches 200 RPM below peak torque - isn't it Makes you wonder what would happen if he launched at peak torque!

As one would expect when launching from a standing start, measured G-Force will be very high initially, then as RPM increases - once the vehicle is under way measured G-Force slowly declines:



Hey, look how uniform the EGT numbers are with that thing reving up

Troy Patterson

Poorly tuned carburetor / engine aside (and not by me) - the owner stated this poor tune represented the highest G-Force measured from his car at launch (with a Weber Power Plated carb) - clearly he's left a bunch on the table yet still exceeded his own carburetor's performance by an impressive margin.

Back to topic, using the G-Force trace after launch and once the vehicle is in motion, you can choose RPM points or ranges to make comparisons between where and how much energy is present to generate the greatest amount of acceleration. If a person argued wind resistance was a factor, then two points could be chosen within say a 200 RPM of each other so differences in wind resistance would be insignificant.

Some would argue there is a greater amount of stored energy in the engine's reciprocating assembly, flywheel and so forth at a higher RPM and therefore a stronger launch / reduced 60' and ET can be achieved as a result - which would require the engine to already be operating at WOT when the load is applied. If the engine is not at WOT when load is applied, the engine is not producing a maximum amount of torque or horsepower defeating and negating any gains launching at red line for example, is claimed to produce.

[MrBo]

Troy, that data log graph is for an automatic transmission. It has a torque converter with its own internal torque multiplication. Apples and oranges.

[Troy Patterson]

Troy, that data log graph is for an automatic transmission. It has a torque converter with its own internal torque multiplication. Apples and oranges.

No matter, once the car is in motion it's all the same - close enough to make the point.

[Stan Weiss]

Troy, that data log graph is for an automatic transmission. It has a torque converter with its own internal torque multiplication. Apples and oranges.

X2

Stan

[Procision-Auto]

Troy, that data log graph is for an automatic transmission. It has a torque converter with its own internal torque multiplication. Apples and oranges.

X2

Stan

X3

[Troy Patterson]

Troy, that data log graph is for an automatic transmission. It has a torque converter with its own internal torque multiplication. Apples and oranges.

X2

Stan

X3

The difference without distinction. Make your argument.

[MrBo]

Troy, that data log graph is for an automatic transmission. It has a torque converter with its own internal torque multiplication. Apples and oranges.

No matter, once the car is in motion it's all the same - close enough to make the point.

How about apples and 500 pound pumpkins?

[Stan Weiss]

Troy, that data log graph is for an automatic transmission. It has a torque converter with its own internal torque multiplication. Apples and oranges.

The difference without distinction. Make your argument.

The job is yours to do not ours.

Stan

[David Redszus]

A massivly heavy flywheel reved to a high rpm will store copious amounts of kinetic energy. When released, it will produce a substantial surge in acceleration....momentarily until the stored energy is dissapated.

And then...if there is not sufficient torque available from the engine (through the drive train) the car will bog down until adequate force is obtained. But now the heavy flywheel becomes a power consumer as the engine rpm is increased and reduces acceleration forces.

It makes much more sense to gear the vehicle properly given the torque available, its weight, and the traction limit.

[MadBill]

Hmmm..If a vehicle is sufficiently underpowered, a thousand pound flywheel wound up via 15 sec. of WOT before launch might be just the ticket, like a giant friction toy..

[David Redszus]

Hmmm..If a vehicle is sufficiently underpowered, a thousand pound flywheel wound up via 15 sec. of WOT before launch might be just the ticket, like a giant friction toy..

Many years ago, a renowned engine builder who shall remain nameless, used a very large flywheel to measure inertia forces on an engine dyno. One day, while testing at 8000rpm, the massive flywheel came loose and rolled through the brick wall, across the parking lot and imbedded itself in the side of a parked car. End of dyno test.

If memory serves, didn't Chrysler develop a car based on flywheel inertial energy storage? I think it was called the Patriot. I wonder what ever happened to it?

[Troy Patterson]

Troy, that data log graph is for an automatic transmission. It has a torque converter with its own internal torque multiplication. Apples and oranges.

The difference without distinction. Make your argument.

The job is yours to do not ours.

Stan

Nebulous.