Rod ratio question

[min301]

Hello, I'm a 22 year automotive tech, and a 16 year engine builder. I was referred by a freind, on Hot Rod magazines forum.
He was speaking about a test done by Reher-Morrison, concering wether or not changing the ratio makes any difference in output. The findings were that peak showed no difference. My question was, what about below the curve, and did it make any change in torque.

Thank you in advance,
Bill

[jacksoni]

Check this thread:

viewtopic.php?t=2066&postdays=0&postorder=asc&start=0

And this one:

viewtopic.php?t=1914

Its a topic gets a lot of thought. Lot of calculation but hard to prove info as tough to A-B-A without other factors changing too. And we race cars not dynos. Look especially at Darin's and Maxracesoftware's amd Panic's posts.

[GibTG]

bump

[Wolfplace]

Instead of bumping this to the top please just take the time to go to the search function at the top of the page & type in "rod ratio"
You will find a days worth of reading in this subject

It has been discussed on this forum at length for years & I believe it was Darin that said something to the effect that if there were definitive gains or losses proven there would no longer be these discussions

In my opinion as well as a number of others I consider a lot smarter than me there are no magical gains with rod ratios within reason.

Two different people can write two different books "proving" how "short" is better than "long" or "long" is better than "short",,, but no one I know of has shown either to be true with subjective data.

It hooks the piston to the crank & makes the wheels go round

[GibTG]

I have read quite a bit about what has been said here, but the orginal poster and myself just wanted a little more info from Darin from his R/S tests funded by GM, he stated before that it made no difference in horspower, but how did it effect other factors? Torque peak? torque peak RPM? timing? ect, ect ???

[Wolfplace]

I have read quite a bit about what has been said here, but the orginal poster and myself just wanted a little more info from Darin from his R/S tests funded by GM, he stated before that it made no difference in horspower, but how did it effect other factors? Torque peak? torque peak RPM? timing? ect, ect ???

=
Here is a quote of a quote from a simple search
Note the part of Darin's post I put in bold.

If this is not an answer to what Bill asked I apoligize & will leave it to Darin to answer your questions again,,,

Hi
this rod thing gets beat around more than probably any subject out there.I kept a post that Darin made a while back and I hope he doesn't mind but here it is-

"In a 4 stroke motor you want a long rod on the compression stroke so that you can take advantage of mechanical leverage. But in the suction stroke the longer rod let's the piston sit dead still at tdc for several crankdegrees and the incoming charge is blocked off under this period. The shorter rod will move the piston away from tdc quicker and will also accelerate the piston faster from tdc to about half way down the bore and that is creating a harder pull on the incoming charge and you will have better cylinder filling".
Just about everyone I know is brought up to believe this. The GM engineers believed it to until we proved it to be false. In 1995 reher Morrison conducted an R&D project funded by General Motors to once and for all prove the Rod ratio theories that everyone subscribes to. In a tall deck small block Chevy the rod ratio was changed from 5.550 to 6.650. The difference in ratio was 1.59 to 1.91. The difference in power? NOTHING, not one single horse power difference. The dyno sheets looked identical in every way all the way up to 9000rpm. That is why I now say its a fallacy.

Hope this info. helps.
shawn

[GibTG]

Oh, my mistake, I had forgotten that he mentioned that the dyno sheetslook the same, I only recalled him mentioning the horsepower values being near identical, but I would still like to get Darin's opinion if the engine's changed in any other way noticeable.