Skip every text I have ever read defines Ve as the breathing ability of the
engine. No where in any of the equations is there any reference to flame front
speed. You can get mean numbers for flame front but that is the best you can
hope
for. Those numbers are different on a cycle by cycle basis. Even worse it is
about impossible to calulate the numbers in both directions in that the
requirement for one cycle is dependant on the previous one to a certain degree,
so without knowing what has happened in the last cycle it is hard to determine
what needs to be done in the next one. Micro proccessors are helping some there
measuring the ionization characteristsics of the spark and getting some useful
info there. The real problem you are having is the fuel characteristics at
Bonneville. I have had the same problem with several cars in that all the
expected things do not seem to work and the EGT is universally too high no
matter
what you do. I have struggled to get below 1450 there and am personally getting
a
little lost to be honest. I feel it is the fuel and there is nothing that can be
done about it as far as I can see. The only other issue seems that it may be a
cooling one at Bonneville in that you are on the throttle for minutes. The other
issue is whatever the ambient temperature goes up so does EGT but this would
only
be about a 20 degree difference as most dyno cells are about 85 or so to begine
with.
This in general is not information that you are going to get that will be useful
in the long run no matter how useful it may seem. All I would think they can
provide you with is the speed under a certain set of lab conditions, which
probably do not have anything to do with your particular engine but hey use it
if
you will be I am willing to bet it will be something that will only send you off
in a different direction that might not have anything to do with what needs to
get done.
Dave
Skip Higginbotham wrote:
> I didn't and may not ask any more questions......
>
> In the mean time:
> Others seem to think that power loss at higher RPMs is caused by VE
> reduction. They might be right depending on how VE is defined.
> The same people (and lots of others) also think that power loss at higher
> RPMs has nothing to do with the fact that the piston tries to outrun the
> flamefront. It can't, of course, but the delta velocity causes less force
> to be applied to the top of the piston as RPMs increase. Basic stuff........
>
> Now back to the question at hand........considering all the factors that
> you have accurately noted as constants or at least knowns for the purpose
> of my question, I would like to (with my engine and it's factors, whatever
> they are) be able to accurately predict the right amount spark advance to
> apply at any operating RPM, by fuel type, to maximize power (force applied
> to pistons). And then implement that advance curve. What's the problem with
> wanting to do that?
>
> Fuel companies that have said that they have the data and won't give it to
> me......so where is it so I can get it???? I'm not making fuel for a
> living....I don't even mess with it....much (-:
>
> Skip (I don't care if the data is current at this point......just want data)
>
> At 02:18 PM 3/1/02 -0500, Dave Dahlgren wrote:
> >ok I am lost now, must be a units conversion thing...
> >I give up how do you get from flame front speed to Ve???
> >Is it squared or cubed by the plug heat range or divided by the 5'th root of
> >the
> >rod ratio???
> >
> >Dave
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