Re: BPW and Cylinder Vol.?

[Roger Heflin <rah@horizon.hit.net>]

On Thu, 29 Jun 2000, Squash wrote:

> --- Roger Heflin <rah@horizon.hit.net> wrote:
> > That would be your problem.   With you doing a brake stand the engine
> > will be loaded more heavily, and will require more fuel.   
> 
> That is why I did it, so I can tune the VE.

VE is different for different loading conditions.  The VE for WOT with
the brakes holding the car is different than VE for the same RPM at
WOT without the car being held.

Heavier loading == more fuel == different VE.

 > 
> > At no time when you are driving normally should you ever get this sort of
> > behavior, and any tuning obtained from this method won't correspond to
> > normal driving VE.
> 
> On the contrary, "normal" driving for this vehicle includes 5500 rpm at 90kpa for 30 seconds at a
> time, 400 rpm at 90kpa, and anywhere in between.  Unless I use the brakes or hook to a 10,000 lb
> sled, I will not get a chance to tune for these conditions.
> 
90Kpa is open loop, it is easy to tune.   You run diacom, do a
dragstrip run and make an educated guess at how the O2 sensor reads.
I will also probably help to read the plugs, but just from the O2
sensors if you are careful you can get a pretty good idea.

Putting a 10000lb sled on the car to hold this conditions, is a
completly different tuning point and won't be very useful for how it
will work at 5500, 90kpa for 30 seconds, it is just not the same.


> What do you mean by normal driving VE?  Normal cruising VE is 0-3500rpm, 45-55 kpa.  What about
> normal heavy load VE?  
> 
> > The engine uses different amounts of fuel in different gears (at the
> > same RPM) just because the loading is different.   Doing a brake stand
> > is a entire new load over all of the gears.
> 
> I'm not doing a brake stand like smoking the tires, i'm driving 30 mph and holding the brakes to
> load the engine.  If this is wrong, what do you suggest?

>From what it sounds like, you are road racing, so you won't ever see
30 mph and as low of rpm as you are having trouble with (<2000rpm)
unless you are a pretty poor shifter.   And 30mph with the brakes
holding the speed down will be different loading than 5500 rpm and
acclerating slowly.  Or 30 rpm at whatever rpm and quickly
accelerating.

The holding the brakes part would only be valid if this was a pulling
vehicle, and then I would suggest getting a trailer to slow it down,
and then the tuning with a trailer won't be  valid for the car
without a trailer (their will be significant BLM adjustments to adjust
for now trailer).

			Roger

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