Megasquirt reality check!

[falzsf at mts.net (shawn f)]

Great post dan.......It is not a small job. PERIOD....
----- Original Message ----- 
From: "Dan Bubb" <jdbubb@ix.netcom.com>
To: <scirocco-l@scirocco.org>
Sent: Wednesday, October 29, 2003 12:07 PM
Subject: Megasquirt reality check!


Since there seems to be a surge of interest in Megasquirt and since I feel
I'm partly responsible because I've been hyping it from day one, I want to
take the time to throw some light on the total picture.
I think the MS is a great little system. It's cheap, it's very capable, it
has excellent tuning software and there is great support on the Yahoo MS
group.

But, having said all that, it's becoming apparent from watching the posts of
some people on the Yahoo group and on Vortex that you really need to have
more than a basic understanding of how engines work before you can install
and tune an aftermarket engine management system.

First there is assembly, wiring and installation. It's easy to bypass these
steps by having someone else do them, but even then this is not factory
wiring, so to get factory reliability some care needs to taken in crimping
or soldering and wire routing to make sure the connections don't fail due to
heat, vibration or contact with other components. You need to be able to
read a basic schematic and convert that into actual contacts, connectors and
sensors. What's the worst that can happen if a solder joint on the PC board
fails or a wire splits due to an overdone crimp?

So, you've gotten the unit installed and it's time to start you car. What if
it doesn't start? Now you have to trouble shoot the installation, make sure
MS is operating correctly and all the sensors are giving reasonable values.
Of maybe you just need to tweek some tuning parameters. Are you familiar
enough with the system to trouble shoot it or know what parameters to
change?

A very common problem with MS installations is not being able to get a clean
tach signal. There are lots of things to change to fix this problem, but do
you have the understanding to know what to change?

Then there is the actual tuning once the car is started. VE table, injector
setup including the possible need for PWM if the injectors are low
impedance, Required fuel and injector control setup. Plus all the
enrichments; cranking pulse width, afterstart enrichment, EGO setup, warmup
enrichment and acceleration enrichment.
There are strategies for approaching all these tuning parameters, but you
need to understand how the enrichment works to be able to tune it.

I've seen alot of people request maps or tuning setups from other people
with similar engines. It is my experience that exchanging maps will get you
a base map that will allow your engine to run. There are too many variables
from engine to engine that will change a VE table or acceleration
enrichment. As an example, just changing to a different cam can change a VE
table entry by 30%! Changing cam timing will change the A/F ratio enought to
require tweeking VE table entries. The same can be said about the various VE
table generators available for MS. They'll get you a starting point! The MS
really needs to be tuned to your engine!

In the end I'll help as much as I can, as I'm sure will other listers, but
there are things that cannot be done through e-mail or over the phone. If
you don't have a good understanding of the fuel requirements of an engine
and don't understand most of the documentation available on the Yahoo group,
it may be best to pass on installing MS or at least take the time to
understand the documentation before attempting installation and
(effectively) disabling your car and painting yourself into a corner.

I'm not trying to inhibit anybody's enthusiasm in our sometimes headlong
rush to more power, but I've heard of more than one guy with a good basic
understanding of engines that doesn't know where to start with tuning his
engine or thinks he's done tuning his car and wonders why he's only getting
10 MPG!

Maybe I'm being a pessimist and everybody's on top of this. I hope so!

Dan
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