J N's MiniRam backfire

[timsiford at hushmail.com]

JN,

Yes, there are many MiniRammed MAF cars running absolutely fine.  The system 
will work.  The 730 is just slightly easier to Tune IMHO and other's opinions. 
 But, you can make the MAF system work ... it will just require a little 
more time and experimentation.

I would begin with those 30lb injectors.  Are they new injectors?  The reason 
that I am suggesting this is because if the 30s are new then this would 
rule out a MECHANICAL injector problem.  Plus - with the MiniRam it only 
takes about 1/2 hour to swap injectors.  Then, put the fuel pressure at 
around 44 and burn a new PROM with the injector constants set to 33lb/hr. 
 Now, I know I am comparing apples to ... hmm ... pears, but my 730 MiniRam 
system runs great with the 30's.  The 30's should not be too big.  There 
are plenty of MAF cars running 30's.

If you still have the backfire once the 30s are installed (which should 
happen if this is not an injector issue) then I would play with the Fuel 
Pressure just to see if you can make the situation go away by INCREASING 
the fuel pressure.  NOTE: I AM ONLY SUGGESTING THIS AS A QUICK AND DIRTY 
METHOD FOR DETERMINING IF THIS PROBLEM IS FUEL RELATED.  If the problem 
did go away then you would NOT want to keep the pressure up that high.  
This will fook up your BLMs everywhere and you run the possibility of going 
lean in the upper RPMs if your fuel pump can't supply enough fuel at that 
pressure.  This will just tell you if it is a fuel issue.  If the problem 
goes away then you want to put the FP back to normal and begin playing with 
the fuel curves to make the situation go away.  

Tim

At Thu, 9 Nov 2000 11:09:54 -0500, "JN" <jwn at sgi.net> wrote:

>
>The recording is a neutral blip.  It also does it in gear.  Smoothly
>increasing the throttle is fine.  It's when you shift and then hit the 
>next
>gear kinda hard you feel a dead shot and sometimes a backfire.  Another
>interesting note is that the zero O2 reading after hitting the gas was 
>also
>recorded (not noticed) when I had the Super Ram on.  There are alot 
>of
>Minirammed MAF cars out there running fine.  Maybe someday I'll go to 
>a MAP
>(which by the way, TPIS claims are a real bear with a miniram) but not 
>until
>I learn this MAF system better.
>
>Jason
>----- Original Message -----
>From: "Bruce Plecan" <nacelp at bright.net>
>To: <gmecm at diy-efi.org>
>Sent: Thursday, November 09, 2000 10:28 AM
>Subject: Re: J N's MiniRam backfire
>
>
>>
>>
>> (reference a modified engine)
>> Well, might be time for a 730, and MAP.
>> I'm kinda assuming that is a *neutral* blip of the pedal.
>> On a MAF system if you want any real response in neutral you just 
>won't
>find
>> it.  They aren't made to operate that way, and the calibration is 
>going to
>> take a really serious amount of work to cure it **correctly**.   The 
>MAF
>> demands a min certain lenght to get the air *straightened* out enough 
>so
>> that the MAF sees it correctly, with the change in runners and plenum,
> he
>> now has a very different system.  The AE, and IAC stuff will all have 
>to
>be
>> retuned.   EFI like anything else must be balanced, each and every
>> component.
>> Being able to blip the gas isn't part of the EPA cycle and I doubt 
>any
>> meaning ful time is devoted to it.  There just isn't a MAP AE correction,
>> and the TPS AE of the MAF just would have a hard time (as in really
>> couldn't) cover that same hole.
>> Even a MAP system for a neutral blip aint the greatest in the wold 
>when
>> comparing to say a carb..  It's the ingear stuff that matters,
>> Bruce
>>
>>
>>
>>
>>
>> > Jason sent me an XLS spreadsheet with data from a scantool that 
>shows a
>> > backfire happening when he blips the throttle.  Car = 1987 Vette 
>w/
>> MiniRam.
>> >  Its pretty interesting.  (Jason, I am posting here because I can't 
>find
>> > your e-mail, thirdgen appears to be down, and I also want to share 
>this
>> > info with others here).
>> >
>> > The data clearly shows Jason 'blipping' the throttle from off idle.
>There
>> > are 4 data points on the throttle blip and you can clearly see the 
>O2
>> volts
>> > going from the switching behavior at idle (TPS=0.53V) to 0mV on 
>a
>Throttle
>> > blip.  The data is below.  This appears to be a fueling issue
>(expecially
>> > when viewing the SA in relation to the throttle blip and LV8).  
>Its
>> undetermined
>> > as to whether or not it is a PROM fueling issue or a mechanical 
>fueling
>> > issue.  What do you guys think?
>> >
>> > RPMs,TPS, O2, AFR, Knock, SA, LV8
>> > 875, 0.530, 836, 14.7, 0, 25.4, 57
>> > 875, 1.630, 712, 11.7, 0,13.8, 189
>> > 875, 3.310, 292, 11.7, 0,15.9, 177
>> > 1300, 2.94, 0, 11.8, 0, 28.2, 175
>> > 1725, 0.90, 13 ,14.7, 0, 45.5, 124
>> >
>> > Jason - quick question for you.  The MiniRam has ZERO provisions 
>for
>EGR.
>> >  What PROM are you running?  Are you running $6E code, $32B code? 
> Is
>your
>> > PROM image based off an original TPIS image or did you start with 
>the
>> stock
>> > image as a base?
>> >
>> > A separate issue is that IMHO, knock -should- be detected and isn't.
>> >
>> > Tim
>>
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