Limiting factor for RPMs?

[TC]

Thanks, where did you find it? I've been looking for weeks.

Oh crap, I got the break year wrong, its '93. Mayfield has the '93. Thanks.

The Two numbers I found came from these sites......

This one just had a list in one of the posts that stated the CDxA.....

http://www.rx7club.com/3rd-generatio...t-drag-737674/

And this one had specs on the probe which gave the Frontal Area........

http://carspector.com/car/ford/016527/

The actual CD number I calculated myself using the Frontal Area number and CDxA number.....

And Mayfield??, I was going to ask, but found it my first try searching for it, pretty neat site, looks like the numbers I found are a little different than theirs, but still in the ballpark........ And if you ever have a problem finding something let me know, I have a good knack for finding stuff......

[Bob Holmes]

The Two numbers I found came from these sites......

This one just had a list in one of the posts that stated the CDxA.....

http://www.rx7club.com/3rd-generatio...t-drag-737674/

And this one had specs on the probe which gave the Frontal Area........

http://carspector.com/car/ford/016527/

The actual CD number I calculated myself using the Frontal Area number and CDxA number.....

And Mayfield??, I was going to ask, but found it my first try searching for it, pretty neat site, looks like the numbers I found are a little different than theirs, but still in the ballpark........ And if you ever have a problem finding something let me know, I have a good knack for finding stuff......

Thanks, the RX7 thread is interesting.

[moparmaniac07]

Holy shit. I thought this thread was dead after page 3. DG, don't worry, it's not ruined. I got out of it what I wanted, and good information sometimes comes from arguments. TC, I get what you're saying, but Squirrel's right. It doesn't really matter, and it's not worth arguing over it. I think some people read too much into what was originally said, and you wind up arguing about different things, but thinking it's the same topic.

The basic premise of the last 15 pages (my interpretation):
TC: An engine with a shorter stroke will reach a set RPM level quicker than one with a longer stroke, all else being equal.
DG/Others: A car will not accelerate quicker just because of a shorter stroke engine, there are many other factors, and you're using the wrong terminology

[squirrel]

that sums it up pretty well.

Now, back to the original subject of the thread...

[jcharliem]

...The basic premise of the last 15 pages (my interpretation): TC: An engine with a shorter stroke will reach a set RPM level quicker than one with a longer stroke, all else being equal...

I disagree. "All else" is not equal. Two different mills with different bore/stroke combos are not equal... even if they displace the same cubes. You're attempting to simplify the topic - as TC is - and it just doesn't work that way.

[TheSilverBuick]

I disagree. "All else" is not equal. Two different mills with different bore/stroke combos are not equal... even if they displace the same cubes. You're attempting to simplify the topic - as TC is - and it just doesn't work that way.

I have to agree. At minimum fuel delivery cannot be equal, because if it was then the longer stroke piston would be moving faster, not at the same speed as the short stroke one, given the same displacement.

[moparmaniac07]

I disagree. "All else" is not equal. Two different mills with different bore/stroke combos are not equal... even if they displace the same cubes. You're attempting to simplify the topic - as TC is - and it just doesn't work that way.

Exactly. The statement was "all else being equal", regardless of plausibility. I've been watching "The Universe", and you want to talk about "concrete laws" of physics being broken, look up some of the theories/discoveries over the years. Regardless of how they pertain to this planet, its cause me to think theoretical recently. Anything can be broken down into simple concepts, then figure out how they relate to each other to determine how best to go about something.

[jcharliem]

^^^ "All else being equal" doesn't apply. May I suggest you contact TC... discuss some theories... then proceed with your new mill from there.

[TheSilverBuick]

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.

[CDMBill]

One of the Mustang magazines is doing a short deck and tall deck pair of 363" motors to compare some of these factors which most of us couldn't or wouldn't replicate. It won't answer most of the problems uncovered in this thread but it'll be interesting none-the-less.

[TC]

I have to agree. At minimum fuel delivery cannot be equal, because if it was then the longer stroke piston would be moving faster, not at the same speed as the short stroke one, given the same displacement.

Just because the piston speed is higher doesn't mean the crankshaft is spinning faster...... Your confusing to different variables.......

[squirrel]

Randal didn't say the crank was spinning faster. He said the piston speed will be different with a different stroke engine, and he is assuming the rpm is the same in both cases.

[TC]

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.

It's very simple to test the theory, build a stock 350 and then build a 350 like I'm building, put the same cam in each with the same heads, intake, compression, just everything the same, hell you could even use 6 inch rods in both of them so the only difference is the stroke of the crank..... Next you dyno test the motors put a load on them and see how fast it take each combo to reach 7000rpm......Record results and let the bench racing begin.......

And piston speed is not always a good thing, you can actually have the pistons go to fast and move ahead of the flame front and you'll lose power.........

[TC]

Randal didn't say the crank was spinning faster. He said the piston speed will be different with a different stroke engine, and he is assuming the rpm is the same in both cases.

RPM being the same?? as in all things being equal??...... That's the problem with his logic, he's trying to argue a different point than I am, I'm talking about an acceleration from idle to 8000rpm and how fast the motor will get there, not how fast a piston is moving at a certain RPM........

[TheSilverBuick]

As Squirrel says, I know that rpm is the same. Pray tell, how to build a stock 350 and a 350 like you're building and keep the bore the same? Wouldn't want the "potential of fantasy valve shrouding" to possibly skew the results.