More TPI questions from me

[Scot Sealander]

Jones wrote:

> What is the difference between the 85 vs. 89 system.

Mostly it is in the CPU.  The 85 uses the older C3 ECM.  The code in it is 
almost identicle to an 86 2.8L MPFI ECM that I have here.  I wonder if it 
was simply a quick adaptation of the V-6 technology before the P4 ECM's 
were ready?

If "nobody" wants an 85, and you can get a good deal on it, buy it!  Just 
use the ECM for reverse engineering and buy a 1227730 ECM from one of 
those V-6 FWD's littering the junkyards, buy the appropriate PROM from 
Chevy, a few wiring changes, such as Peter has suggested here and you are 
there!

> I know the 85 uses
> a cold-start injector system while the 89 and up units do not. Why is
> one better then the other? 

Software is so much "smarter" than hardware.

> Why does everone want to eleminate the cold
> start injector?

Better starts.

> What is the difference between the speed density system
> and the mass Air Flow? 

How the amount of air in the cylinder is determined.

> Would one be more desirable for my application?

Yes, the MAF is (IMHO) ugly!  And you have to mount it somewhere.  The MAP 
allows you to just put a K&N on the Throttle body.


> Is one system better? Also, it seems as if everone on the list perferes
> the 89 EPROM, why?

I like the 91 code for the MAP.  It is just the little improvements along 
the way....

Scot Sealander   Sealand at clarityconnect.com