[s-cars] RS2 MAF deliberations

[QSHIPQ at aol.com]

--
[ Picked text/plain from multipart/alternative ]
In a message dated 4/19/2003 4:07:00 PM Central Daylight Time,
mik at info.fundp.ac.be writes:

>>Totall agreed the RS2 is preferable from an "open mesh" point of view but
>>from a programming point of view, I prefer the stock unit. And I think
>>several people over there have found out the RS2's screen only gives a few
>>more horses (with the right programming of course, there's no point in
>>comparing 2 MAFs with the same SW when the SW doesn't take the MAF >>values
>>into account the same way), nothing really relevant actually... I can't
>>explain why the RS2 used that MAF as at that time I was still playing and
>>repairing/upgrading guitars and amps, not cars, though...

I'm an old fart...  No one (even Bosch) has given me the answer to that
question either.  Porsche ego, or definitive advantage?  My bet is on the
latter, but have seen plenty of the former....

>Those asterisks are what keep me smiling Minhea.  I'll go back to a point
>I made long ago.  That MAF - ANY MAF - in the I5 20vt is not necessary at
>all.  ***  With proper tuning ***  it can be eliminated alltogether, in
>which case:  up goes HP, torque, throttle response, preturbo inlet
>pressures and temps lower.  Why not "properly tune" that pipe right out of
>the fuel equation?

>>Well, at least me and the German engineer whom I've learnt Motronic systems
>>with don't think it's good to remove the MAF from the circuit *** in a
>>Motronic I5 20vt ***, not even for 500 HP...

Why?  Speed density systems are what Motronic systems default to anyway (with
absent or bad/maxed MAF).  I see the MAF as redundant and unnecessary to any
motronic system.  A velocity stack to the inlet of a turbo is the cats meow.
The "redundancy" of MAF is really to protect from air leaks in the system
causing boom (we can also define "air leak" as too much HP bolted on).  SD,
especially WR02 SD won't care if you have an "air leak".  Whatever's
happening upstream of the combustion chamber results in a O2 reading which
gets fuel.

>>I don't want to enumerate the pro's and con's of alpha-n vs. MAF vs. speed
>>density systems but my point is that Bosch know their stuff better than
>>anyone else and if they did and still do the Motronic with a MAF (as in the
>>S4tt's, 1.8T's, VR6's and so on), there is a reason to it.

I think that may be an audi demand more than a Bosch requirement.  For
redundancy purposes, the MAF can provide some failsafes that SD systems
can't.  However, they can also be THE restriction to more HP.  Wide Range 02
is going to make Bosch and audi look at that redundancy in terms of cost vs
benefit.

>>The new systems
>>are very complicated right now, i.e. they monitor EGT, use wide-band O2
>>sensors, check for the feasibility of an actual particular injector opening
>>time and so on, but so far, they do still use MAFs, even on the RS6.... and
>>this is because the MAF Mo(t)ronic system has proved that for everyday
>>driving it is the best system around. Alpha-n and speed-density require
>>reprogramming every time one changes a part that alters VE and can't
>>compensate by themselves for an engine wearing out and loosing >>
compression...

I disagree with this conclusion of SD, in fact just the opposite is true.  SD
doesn't care what you add to the engine, it will measure PT and TPS,
corrected by O2.  Wide band O2 actually makes speed density an even better
idea, since there is no need for any WOT "tabling".  O2 based systems are
more accurate than MAF, there's no "estimation" only lean/stoich/rich.

>>Then, if one removes the MAF and reprograms the chips accordingly, the
>>system would only be an alpha-n system, and I think an SDS or similar
>>system is cheaper than an alpha-n reprogrammed Motronic, right? The
>>Motronic can't run as a speed-density system as the MAP or PT is only used
>>by the "boost control" part of the ECU, i.e. the bottom board. Then, the
>>pressure drop across the MAF is only 0.05 Bar (measured by a friend of
>>mine), which is minimal and I can't see why the intake temps will be lower
>>without a MAF rather than with a MAF... of course the argument can go on
>>for days and months but I simply can't see why the MAF is such a big
>>problem in here...

Drive a SD system, there isn't a problem, only gains to be had.  All I can
tell you Minhea is, that the MAF has been deleted, on a neu S4 with all the
extra goodies.  I haven't seen a higher HP table from a MAF equipped one.
For SD, you already have ALL the components for it in the Motronic system.
With proper tuning (-tm MC:) it can and should be taken out.  I look at the
monster MAF projects MLP/Hap/Jonsie have taken on, and think that's a lot of
money for something that's really not necessary.  Me, I'd be spending those
dollars deleting MAF and adding WBO2 into the software.

>>Well, Scott, this is where and what my respect goes to you for! I've tuned
>>quite a few different 20vt engines, some of them with weird parts bolted on
>>(Garrett hybrids, unusual injectors and so on) but I haven't built an
>>engine myself yet!!!! So, you're a tweeker but better than I am (though I
>>did my 20vt swap on my own from scratch and only with my wife's help). So
>>this is why I respect you and I don't want to argue with you on this
>>subject for months.. :-)

Good wife, keep her.

>>WRT Hoppen and MTM programs, I can't really commit as I dunno what they
>>really sell... I've received a supposedly Lehmann SW for RS2ed AANs which
>>is almost identical to a SW I got from MTM so I really dunno who or what to
>>believe except what I program myself and check for "proper" EGTs myself...

I think the bed has been shared so to speak on the urs programming.  Beyond
400hp is where the play is now.  What to do?  Those resultant SW changes get
bigger, and scrutiny of the HW changes should be made concurrently.  Since
the variance of HW of these 400+ machines is going to get wider, why not use
SD and let "Hapersize Go Wild" (video soon to be released).

>With regard to accepting/needing any MAF at all, I'll freely argue our
>definition of ***properly tuned*** will always differ.  I know it can be
>deleted, I saw it done on a S4tt.

>>Of course it can be deleted, I just simply still think it's not so
>>necessary to delete it, but maybe when I blow 2 or 3 per month (with 450+
>>crank HP) I'll see the need to delete them :-)

Others are already there and have BTDT Minhea.  At which point, this
tweekster looks at the problem and says, hey, you don't NEED a maf.  The best
argument for that thinking is affordable WR02.

>>Anyway, thanks for your thoughts again Scott!
>>Mihnea

Yours as well Minhea...  I gotta go talk to my wife now....

SJ