More TPI questions from me

[John Hess]

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

Too numerous to describe.  It was the first generation TPI system and 
was significantly changed for '86.  The '86 through 89 is pretty 
consistent (some mapping and other variances to basically the same 
system)

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? Why does everone want to eleminate the 
cold
start injector?
I don't know that EVERYONE DOES.  I do. The cold start injector is 
simply something else to go awry.  If it can be gotten rid of with 
programming, then do so.

What is the difference between the speed density system
and the mass Air Flow?
Speed densiity measures the manifold pressure as the controlling item 
whereas Mass Air Flow measures the actual volume of air the system is 
using.

Would one be more desirable for my application?

Depends.  If you are building a machine that you will be developing 
over a period of time, or for the street, the MAF might be a better 
solution in that it works with a very wide variance of modifications, 
including cam, exhaust, intake, etc.  On the other hand, if you are 
looking for maximum performance on and engine (system) that is 
finished, the MAP (with proper mapping) will generally yield greater 
horsepower (at least as great as a well tuned carburetor).

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

According to what you are doing, each has its benefits (described 
above).  As for the '89 EPROM, it was the last of the '86 - '89 
programs, so for that genre, the '89 has all the goodies developed for 
the model.  In '90, the system changed to MAP.  Got a little 
horsepower;  but, became a little more difficult to modify without 
remapping.


Mike Jones
rwj5125 at electriciti.com