Limiting factor for RPMs?

[dieselgeek]

Which is why the goal should always be maximum torque at the highest RPM? I hear that a lot. The EMC guys approach it this way because it mazimizes point score there.

[TC]

Now we get to whats the quickest ET this gets talked about on every board all the time. Mike Jones put it very
well from Jones Cams

I really can't believe some people can't understand such a simple fact.

The only torque that matters is Wheel Torque.
Wheel torque is engine torque multiplied by the gear ratio.
To be able to run a gear that is a higher multiplier of torque, you need to be able to make that torque at a higher RPM.
So the two things that can increase wheel torque is Engine torque, and RPM.
We measure the combination of engine torque and RPM as Horsepower. That's why we look at Horsepower.
If you can move the power curve of the engine up 20%, you can run change to a gear that'll increase the wheel torque by 20%, so even if the engine torque is down 15%, you'll be faster.
We look at HP because it is Torque and RPM.


I would add the TQ on a Automatic is a fine multiplyer of TQ if its a poper converter for the job

Apparently Mike and I think alike........

[squirrel]

Which is why the goal should always be maximum torque at the highest RPM?

Of course, and you need to set up the drivetrain so the engine is running at highest RPM (or as close as you can get to it) all the time. Within the limits of traction, of course.

[dieselgeek]

Apparently Mike and I think alike........

Mike is one of the top minds in his field. About the only time I see you two thinking alike is if Mike decides he has to take a poop. At that time only, would you and he have the same things on your mind.

[dieselgeek]

Hilariously, there's a thread going on Speedtalk.com forums right now about destroking, and in general short stroke engines. Just to confirm that TC and Mike Jones do NOT think the same way, here's a quote from Mike. Hopefully Mike's lawyers don't send me to jail since per TC I am breaking the law here:

The only time you would want to de-stroke, is for a racing class where the CID is limited, and you can increase the bore along with the de-stroking, or a class that gives a weight break for less CID., or a really bad engine design with too short of a rod length.

[jcharliem]

Hilariously, there's a thread going on Speedtalk.com forums right now about destroking, and in general short stroke engines. Just to confirm that TC and Mike Jones do NOT think the same way, here's a quote from Mike. Hopefully Mike's lawyers don't send me to jail since per TC I am breaking the law here:

Uh-oh. Is TC posting on that site/thread? Or does he only stink up this place?

[dieselgeek]

Uh-oh. Is TC posting on that site/thread? Or does he only stink up this place?

He doesn't post. Even he knows better.

[JeffMcKC]

Mike is not saying the same thing as you TC.

[BKBridges]

Yep, that's one reason we've got one between the frame rails of my race car.

By the way, El Mirage next weekend! Bring the Jensen

Dynoroom,
I will be there, but the Jensen is laid up with a blown torque converter... went Cherynobyl in Mariposa CA last week. If you had smell a vision the pics would really be stinking things up around here... Some vacation fun. Damn long stroke motors...
Bruce

[CDMBill]

Except forced induction.

Actually, forced induction doesn't alter the advantages of greater displacement, you just need a bigger pump to match.

[CDMBill]

There are a lot of "Maybe's" in that article AND it says it took 4HP more to run the short stroke engine, which would be 4hp less being used to accelerate the engine and car. And it mentions that the short stroke for slower piston speed is to make the engine last 500 miles, not about making more HP or being more efficient. Also says that torque is about engine size and volumetric efficiency, like OldMachinist was saying, more cube's. In class limited fields, short strokes win out over long strokes to get big bores for more airflow on the same capped displacement. Of course all this is just a repetition of what's been said over the last 150 posts. The last line, "If you can afford it, a combination of big bore and long stroke is the ultimate answer. There will never be a replacement for displacement." And you are shorting your build on displacement.

I'd forgotten about that story, the conclusion is in essence that there is no difference for the engines we are talking about and that Old Machinist is right on about maximizing displacement. On this point I'm already there at 4.560 bore (as that's all it'll sonic check to) and 588", and I suspect that's why, last I knew, Larry Larson's motor is a 572". He and Moran seem to know their way around how to go fast with twin turbos and drive on the street and do donuts in the parking lot. Much to be learned there.

As usual Jeff has summarized the rest of the original question well as have a number of others here and yet the thread goes on and on.

TC are you going run a 4-7 swap cam?

[TC]

TC are you going run a 4-7 swap cam?

That is one thing I was going to discuss with the cam manufacturer when I call them to recommend a cam........ With 50mm cam bearings I'm not going to find an off the shelf solid roller, it's going to have to be a custom order piece...... I did find a used Crower solid roller on Ebay with 253 duration at .050 and about .600 lift with 1.6 rockers(that's the ball park I'm looking to be in) but it was on a 108 LSA, and I'm not sure if I should go that tight on a turbo motor.......

[CDMBill]

You are solidly in custom cam territory regardless of what your final configuration is for the engine. Mike Jones sells custom cams BTW.

I was being a bit tongue-in-cheek as the 4-7 swap cam test precedes the short stroke long stroke comparison story in the link you posted.

[Bob Holmes]

Actually, forced induction doesn't alter the advantages of greater displacement, you just need a bigger pump to match.

[moparmaniac07]

Here is the problem with "All else being equal" and "theory". How do you test your theory? As soon as you change the stroke a dozen other variable suddenly are not equal. Unless you have lots of parts to work with to run dozens of statistics from hundreds of test, keeping as many of the variables unchanged as possible, your theory doesn't mean jack because it has zip for data to back it up. That's the scientist in me.

All else being equal as in the force pushing down on the piston, the frictional force resisting motion, the moment of inertia of the crank and whatever else is attached to it. The only difference being the length of the stroke. One will accelerate faster than the other, or they'll accelerate at the same speed. Oversimplified, yes, but it can be proved or disproved with math. I don't feel like doing it, but it can. Obviously there are other factors in the real world, but that's what I mean by all else being equal.