acceleration measure (was Re: G-Tech meter )

[Arnaldo Echevarria]

I'll answer all of the questions posed in one swoop:

> Sounds interesting but you are still going to need an accelerometer or
> torque measurement from the drivetrain.  Otherwise, your product will
> only be accurate on level ground.  Around where I live, it is pretty
> hard to find level roads where you can test the car.

True, but my goal is to obtain REPEATABLE results over the same stretch
of road. Of course all of the measurements will be off in hilly
environment,
but I wouldn't want to be tuning my car in hills anyway (I'd be fun,
but....)

>I am. Have you run into problems with the rotor's exceeding the Curie temp 
>after extended hard braking? How much gap clearance do you require?

I'm still playing with the gap, but it looks like 3-4 mm. I'll have to
look
at the temp issue; I really didn't think I'd get over 150C 3mm from the
rotor.

>and disadvantages.  We have tried your method already and found that the
>'hill' issue becomes critical again.  You will have accurate speed but
>not 
>accurate HP because the slope of the road will not be accounted for.
>For 
>good results, we had to test not only on the same road each time, but 
>initiate the accel at the same SPOT in the road at the same VELOCITY
>too.  

1. Who wants to obtain repeteable numbers from different conditions?
That's like saying "well all of you that post 1/4 times don't compensate
for altitute/temp/wind so they are totally invalid".  While it is true
that
the system I proposed would be affected by every known variable known
to man (road conditions, grade, temp, density, wind, etc etc) - the
goal is to get a "reference" - a relative, repetable number, even
though it may be slightly off. Of course, you could get exact numbers
by duplicating track conditions (straight road, no wind, etc) - but
then again, anyone know of a system that will PRECISELY give times / hp
over any given terrain under any conditions (wind, temp, etc)?

2. Besides, most dynos aren't overly accurate anyway.  I work with
a Dynojet and it is sometimes difficult to get very consistent results
with the same car under similar conditions! 

3. A torque / hp graph is not a bragging tool - it is a tuning
device used to find out the performance of your engine.  
A relative hp graph would do just fine for ME, as long as it was 
consistent (which it will be if I take my car to same stretch of road
for testing).  I'm not concerned about finding out my true exact torque
/ hp numbers of my engine because:
	- you can't do it anyway unless your engine is on an engine dyno
	(nearly impossible to ACCURATELY model hp losses in drivetrain)
	- engines behave differently on dynos anyway
	- even if I did come up with THE CORRECT torque band for my
	engine, who would I compare it to? most of the stuff on the 
	magazines is inaccurate anyways...who is to say who is 
	correct?  
4. My goal isn't to say "look my engine makes 392hp" its more like
"look it was making 383hp and I changed a/f mixture and now it says
389hp". Whether 389 is really 388 or 385 is not an issue to me.
Repeteability is the main issue, and I think it can be done over
the *same* stretch of road, given similar weather conditions.

Arnaldo "I don't take wind into account at the track"
aec at netten.net