Motronic vs. alternatives[was Re: MC-1 MC-2 - Block any difference?]

JShadzi at JShadzi at
Wed Feb 25 00:25:21 EST 2004

Ben, I think I already touched on the main reason in my original email, but 
more or less, the Volumetric efficiency of a tuned 10v motor is greatly 
different than that of a 3B 20vt.  You mention that the 3B Motronic is adaptive, or 
"adaptive", I wouldn't interpret this too deeply, narrow band O2 feedback is 
hardly going to allow a Motronic system to self-tune itself to a totally 
different motor.  And, the 3B motronic was infact designed for a 4-valve, 5 cylinder 
engine with a very specific configuration, it was never offered on any other 
motor with any other configuration.  Maybe you're overgeneralizing the name 

There are plenty of poorly tuned 3B and AAN Motronic systems out there, 
recently I consulted with an owner of a highly tuned AAN S4, he had thrown several 
high performance "chips" at it, the car was running poorly, on the dyno it was 
going pig rich (9:1 a/f), its base programming was way off, no amount of 
adaptation was going to get this motor back in tune, his power #'s were totally 
suffering becuase of it - I believe this was the result of the highly changed 
configuration of his engine, bigger turbo, ported head, etc, etc and chip tuning 
that was just a "guess" at what the motor was really needing.

Installing a 3B Motronic system on a 10v is infact unconventional, from my 
knowledge, it was never provided from the factory on a 10v motor, so you are 
"re-inventing" so to speak.

Also, if you think your 10v motor is going to flow even 85% of a bone stock 
20v you're probably fooling yourself:

10v intake at .5" lift - 130cfm (on a good day)
10v exh....... - 90cfm
20v intake at .5" lift - 190cfm (easy)
20v exh....... - 140cfm

I don't know if you've ever actually flowed a head you've ported, but I've 
done up some real nice 10v ports in the past and actually hurt the flow through 
the head once I flowed it, so don't assume your motor will breathe anywhere 
near what a 20v will.  Recently I helped build a 10v head for a customer, the 
intake was carefully flowed on a bench to 160cfm, the exh. port were actually 
raised 1/4" and totally reworked to a square shape, I built a custom header for 
it, this motor flowed an amazing 140cfm on the exh side, equivalent to a stock 
20v.  With a little work, the 20v easily goes to 215/160 cfm @ .5" lift.  The 
head alone was work about $4000.

I never said it "wouldn't work", my assertion is that it will work OK at 
lower power levels, but is already out of tune, and the more you push and change 
things, the more the 3B Motronic will be out of tune.  The 20v motors can 
withstand much more ignition advance than the 10v, its power band is completely 
different, its just a totally different mapping strategy.  I suppose if you can 
somehow retune it to give you a good a/f under WOT then you'd be in the ball 
park, but then there is the issue of ignition timing, etc.

I'm sure you're right about the value of the 3B Motronic system you picked up 
is great, and I'm not trying to be a jerk, it just seems you have some 
misconceptions or "over assumptions" about how it will work in your application, and 
that's based on my experience, not guessing, etc.

I'm releasing a new 034 product soon that you might be interested in, contact 
me privately if you like, it will be a "stripped down" version of the full 
Stage IIb ECU (sequential fuel, dist ignition) at a significantly lower price.

It can't hurt to give it a try, the 3B Motronic, let me know if I can help.


In a message dated 2/24/2004 8:01:33 AM Pacific Standard Time, 
benswann at writes:
I don't beleive Motronic was designed exlusively for 4 or 5 valve per
cylinder engines.  Surely this is one of the better designed EFI systems out
there, at least for its day.   I don't know what your friend is doing to try
to get hes system right.  There are those who can't seem to get CIS right
either, and those like myself who have been able to get it working well,
even when the power requirements were higher than the stock engine.

I also don't understand exactly what the major difference is going to be in
the 10V vs. 20V with respect to air fuel mixture.  Perhaps someone can give
me a better explanation than that of cost and citing examples of those who
tried and couldn't get it right.  I know if I had to build it from scratch,
Motronic would not be an option, but I have sourced the system for a very
reasonable cost.

I don't believe using Motronic would be considered re-inventing the wheel,
in my opinion it is just the opposite.

If I continue to follow your logic to its end, I'd be ditching the Motronic
system in my 200Q20V avant.  I currently have several chip setups to choose
from and can make changes as necessary should the need dictate.  Right now
my 200Q20V is Running quite happily with Motronic at  higher boost than
stock and the car is so fast I've had no desire to go to 3Bar.

Again,  what is the real reason that Motronic isn't good for a 2 valve per
cylinder engine.  I expect to be getting similar flow out of my engine as
that of a stock 20V.  Is there a problem with sequential fuel injection for
the 10V?  Is there a problem with the stock injector flow rate?  Is there
simply a problem with the parameters that are programmed into the Motronic
chips for one specific engine that will make it not optimal for an engine
with different compression and flow?  Is it simply a matter of the system
was being pushed outside of its design parameters.

I'm not hung up on using Motronic, but it does seem to be the best thing  I
could source for the money.  As a side note, I am considering going straight
to Megasquirt, as by the time I get the engine completed, sequential
injection will be fully available, or I can just implement batch if
sequential is the problem.  If I could have sourced the 034EFI for twice
what I'm paying for the Motronic setup, I might have considered it.  I must
say Javad has a great product from what I understand.  I just want control
of the code and schematics for any non-stock system that I implement.  I
don't think Javad is ready to offer his product available on the open
consorcium basis that MS is available for.


More information about the 200q20v mailing list