[s-cars] Injector "balancing" perspective

[QSHIPQ at aol.com]

A variance of 5-10cc is very normal for a production FI, a variance of .7-.8 
means that the injectors are "balanced".  If one was to argue that the RS2 
injector is a 380cc injector - tm RC (bosch claims 440 "uncorrected" to RC), then 
a 8cc variance is 2%.  Actually, if one was to ck around, many places that 
advertise injector 'balancing' are claiming 1.5%.  This tells me that the RS2 is 
darn good as delivered.  As rpm's increase, S car sequential fire fuel 
systems become batch fire by definition, so I really doubt 2% has any significant 
advantage, specifically, I doubt there's any disadvantage to running and 
injector with even higher measured flow variance.

I'll also share some btdt here at sea level.  I haven't gotten the RC 
injectors that were functioning "fine" in CO, to function fine in Chicago.  I suspect 
that's because it's quite possible that the input sensors and software used 
in CO, actually makes the RC's run within acceptable specification.  I could 
speculate on a bunch of other ideas with regard to this, but I'll suffice it to 
say that the RS2 injectors solved the problem.  Finally resorting to parking 
an RS2FI/RS2 equipped S car next to the RC/RS2 equipped S car and swapping 
parts.  The first indication that something was array, was the data logging of O2 
sensor readings on the RC car.  Lambda at idle would hover right at .98-1.02, 
but a throttle blip to 3-4k would result in a very slow recovery of baseline 
lambda.  The RS2FI car worked fine.  After swapping the injectors, no problem.  
Go figure.

I'm with Minhea/Ned on this whole idea, if you are using a non standard 
injector, it's not automatic that the car will run better without proper tuning of 
the software.  And what may work at sea level may not elsewhere.  
Unfortunately, there aren't a lot of custom software guys available in the States.  
Unfortunately 2, very few folks are interested in 7gas exhaust analyzers in helping 
them properly tune fuel.  Add a 7A exhaust cam, fuel is whacked out again.  

I'll put forth that RC injectors are *an alternative* to the RS2 injector, 
hardly "the".  Claims of 'better' based on 2% flow variance I believe to be 
totally a naiive and mythical benefit (you must be joking;). 

I also believe that the RS2FI is good for 400hp+.  In the 300HPATW S car I 
tested, prior to switching to the lower (3.8) RS2FPR, the car was drowing in 
fuel.  I believe also, that there are very few S cars out there that can claim 
that they've overshot the RS2 injector in terms of flow.

My .02 arbitraged thru the peso

Scott Justusson
QSHIPQ Performance Tuning
In a message dated 2/23/2004 6:48:44 PM Central Standard Time, 
mlped at qwest.net writes:
The RC reports are tucked away in a file folder, now filed I think under "No
Idea where" someplace.

I can't recall the specific numbers for the Bosch injectors.  It would be
interesting to find the reports, because as I recall, I think I asked RC to
test them at several different pressure settings, 3bar, 4 and maybe 5bar or
more.  A comparison of those numbers vs. the formula's "new" pressure x
square root of old/new might provide a hint as to how much, if any effect
the rising fuel pressure degrades projected performance.

As I recall, RC would flow "match" injectors, whether Bosch or their own in
house.  The variance might have been greater than RC's guaranteed "matched"
set, but I don't recall it being as great as the 7 to 8 cc's you suggest.
But then again you could be right.  As I go through the old file folders
I'll try  keep my eye out for old reports, if they still exist.

Mike
  -----Original Message-----
  From: CaptMagu at aol.com [mailto:CaptMagu at aol.com]
  Sent: Sunday, February 22, 2004 12:29 PM
  To: mlped at qwest.net; s-car-list at audifans.com; forgied at direct.ca;
mik at info.fundp.ac.be; rstoddard at shaw.ca
  Subject: Re: [s-cars] Alternatives to RS2 Injectors


  Mikey

  I don't know if you've still got those RC flow sheets but if my memory
serves me, the other issue with the Bosch injectors was the relatively large
spread of flow numbers. Given that RC was doing the measuring, it seems that
there was something like a 7-8 cc variance between the Bosch injectors. The
Rcs only had .4-.6 cc variance.

  Hap, tryin to remembah in Evahboost, Maguire