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[quote]I think you'll find that an engine that will accelerate it's best can very well use less fuel than one that dosent accelerate as well, and it's certainly going to need fewer pit stops.
Sounds like a plan for the next Parker enduro, have you got plans to run???MP
I may be driving, but nothing of my own. Just too many projects this year.
This is true with most "average" ex ports. This is why I'm an advocate of having the best exhaust port possible. It would be great if the ex port could flow the same as the intake port. You wouldn't have to open the ex valve so early or lift it as high. You could take advantage of the remaining pressur in the cyl, and still evacuate effeciently. The remaining pressure in the cyl past 90* is still pushing down on the piston, and anything is better than nothing.
For example:
The ex lobe in my 467, with the Canfields that I ported is opening (@.050) 69 BBDC, and closing 17 ATDC. That's a long way from the numbers you're talking about, but the ex port on those heasds flowed 298 @ .700, and 312 @ .800. That's over 85% of the intake at the same lift. The results speak for themselves. That engine also made BMRP #'s in the high 190's and broke 200 @ peak torque. That's with only 12.4:1. Good combustion.
RMbuilder...what you quoted is true to a certain extent, on certain motors, but is also a very wide and sweeping generalization.
Steelcomp,
In my conversation with Infomaniac we were both referencing the valve events at rated seat duration. As correctly stated by Info, referencing the valve timing @ .050 is of no value here as the valve is already well off the seat at .050 lifter rise. This is particularly significant with the EVO as the pressurized cylinder begins to blow down immediately as the valve begins to open. Given there is still some residual cylinder pressure remaining in the power stroke @ 90* ATDC the balancing act then becomes determining at what point the decaying pressure curve is best utilized to blow down the cylinder vs. where it delivers useable leverage to the arm. In your rebuttal you referenced many significant data points particular to your engine. Looking at your exhaust lobe let me quote you
opening (@.050) 69 BBDC, and closing 17 ATDC. That's a long way from the numbers you're talking about,
You referenced the .050 (266*) exhaust timing numbers here with an EVO of 69* BBDC. To examine your exhaust lobe correctly @ rated seat duration (as per my previous post) we need to utilize your correct exhaust lobe dimensions, which are (302* rated). Given your centerlines this will render a rated seat EVO (lash factor included) of 87* BBDC/ 93* ATDC which are 1*-3* of the valve events Ron and I were discussing, hence my confusion with your last sentence. What I quoted is true, in reference your motor, and is in no way a very wide and sweeping generalization. The laws of physics do not discriminate.
Bob
Anyone interested in re-opening this discussion?
After taking a quick look at this thread, this should get pretty interesting!! :idea:
Warp Speed ;)
Pressure.
God allows it to accelerate.
Paul
Money! like the guy said back in '05! Especially with the price of gas!
CC
.............When the build was off or it was a little tired...........CH3NO2
oh steel, did you really need to open this can of worms again! I stayed out of it the first time but.............. well here goes. According to Newton if something moves it means a force acted apon it. and torque is a force.
But Fulton (the father of horsepower) says the speed at which it moves is the result of horsepower. Torq can move something with zero regards to time, horsepower is totally time based. You asked about accell so the answer is HP
What's going on???
I was downloading Desktop Dyno and it linked me to here....