DIY_EFI Digest       Saturday, December 4 1999       Volume 04 : Number 675



In this issue:

	Soap box
	re: Stop guessing at facts.

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Date: Sat, 4 Dec 1999 12:12:41 EST
From: A70Duster@xxx.com
Subject: Soap box

Phil writes

<< Most engines need 15 to 20% more fuel than stoich to
 make peak power and 10% less to make peak efficiency. >>

and

<<at 12.8 and second 7000 rpm has a max pw of 7.57ms.>>

Three helpful tidbits and a bunch of complaining.  If you need to unsubscribe 
then



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Later....

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Date: Sat, 4 Dec 1999 11:22:03 -0800
From: "John Dammeyer" <johnd@xxx.com>
Subject: re: Stop guessing at facts.

Hi Phil,

I found Scotts comments quite good!

>Phil
>Injec Racing Developments
>
>And just a hint to John. The limiting factor is your first choice of
>max pw
>at 12.8 and second 7000 rpm has a max pw of 7.57ms.


I'm not sure that I understand what you mean about limiting factor but an engine
cycle is 720 degrees and therefore, at 7000RPM,  with an 80% duty cycle the max
pw is 13.7ms.  By limiting my pulse width to less than 75% I just needed
slightly larger injectors.  By using Lucas injectors, with a shorter open time,
I can use a short pulse width at idle and still keep the engine ticking over
smoothly.

BTW,  theory finally caught up with real life after I discovered a software
glitch in the ignition timing that had my advance at 65 degrees at high RPM.
(oops).  Now I (properly) limit advance on this engine to 34 degrees and maximum
advance is in at 4000.  VTEC solenoid comes on at 3700RPm and we are achieving
134HP at 6700RPM.   Suddenly my Volumetric Efficiency table matches theory and
tuning the engine has become far more fun.

Regards,

John

I also agree that the Internet can be a source of mis-information and if
everything was considered to be the truth some would end up believing that an
ambient (barometric) pressure sensor isn't necessary. ;-)

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End of DIY_EFI Digest V4 #675
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