red ws6 99

Yes it can be extended out, Harlan Y2KHAWK has his extended, maybe he will come on here and post his curve.

Gary

ChrisB

You can extend your range somewhat, but there are still problems.

You have 2 limits to deal with - the physical limits of the MAF sensor itself (at what massflow rates is it still precise?) and limits within the computer itself on max massflow variable size.

Concerning the sensor itself - it is already getting near the limits of it's range in the stock calibration (which is probably why GM flatlines it near the top) What I mean by this is that measurments at this rate are not precise (repeatable).

Now if you port the sensor or get a differently calibrated sensor you may be able to extend the physical limits of the sensor. Now we run into the second problem.

Due to the way the massflow rate is stored in the pcm you can not have values greater than 512 g/sec.

Basically if you are near/at/just bast the stock border you can probably extend the range enough to work - but past that you are out of luck with respect to maf range. depending on the airflow rate of your motor this may or may not work.

But there are possible solutions. Here is something that was discussed on the LT1 Edit mailing list but died due to lake of hardware fabrication.

A dual MAF setup - you would need to take 2 MAF sensors and mount them in parallel in the airstream. You would need a microcontroller to sample both, convert the HZ to airflow (lookup table), then sum the airflow (since hz and airflow are not linear you can't just sum up frequency). Finally convert this total airflow back to Hz and you have a new value.

Doing this we have extended the physical limit of the sensor by a factor of 2. If we assume the stocker is good to 400 g/sec with high precision then we now have a 800 g/sec unit.

Now we need to address problem 2 - the limit. Without code changes, hacks, etc. we are limited - but there is a solution. Since airflow and fuel rate are linearly related we can use one to scale the other. In our hardware above we will add one step - after we have summed the massflow rates we will divide it by two and then convert the new value to hz for output. So now our max massflow value of 512 actually corresponds to a real 1024 g/sec.

Now we need to correct fueling. We can simply take the injector flow table and multiply it by two. We are reporting 1/2 the actual air, but are putting in 2x as much fuel as it needs - since 1/2 * 2 = 1 - well, that means we are addign fuel in a 1:1 ratio again.

The only problem we have now is load based - the computer uses maf input to calculate load - and we have scaled that by a factor of two. But we can remedy this by changing the displacement of the motor to half the actual value. Load calculations will now be correct - and as a bonus the car should operate properly in SD mode now also.

What we need is someone who can build the above hardware microcontroller - the rest is just easy manipulation with LS1 Edit. Harlan? It would work for LT1's, LS1's, etc. - you would just need to alter the lookup table for the particular sensor used?

Chris Bennight

Ellis1

For my current setup the extending the range out to 512 g/s(67 lb/min) would work pretty well. I currently don’t even hit the 58 lb/min limit, but as the weather gets colder I would expect to see at least 60-63 lb per min. Does the PCM just throw the code at 58 and continue to read higher or does it read the same number continuously above this level?(this would be lean and bad if it does happen) In LS1 edit what needs to be changed to get to the 512g/sec limit?

Ellis1

I know that the stock limit for the maf meter is 58 lb/min. Can this range be extended with ls1 edit?

y2khawk

iTrader: (5)

Yes, i have extended the MAF table to the 512 limit.

I wasn't seeing the flat line until i went over 12 psi on the boost. But the MAF does seem to have a valid ouput at these levels, repeatable output and constant AF on the wideband.

Now the dual MAF box is an interesting situation. In theory and easy task. Problem is cranking. PCM is in speed density at crank. Halve your injector numbers and you get gobs of fuel at startup. Hard to get around that.

I could investigate the dual MAF average box if the interest is there. But there are other issues that need to be addressed along with it.

ChrisB

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by y2khawk:
<strong> Problem is cranking. PCM is in speed density at crank. Halve your injector numbers and you get gobs of fuel at startup. Hard to get around that.
</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">I addressed that above <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" /> If you divide the displacement by 2 then proper speed density mode will be restored.

Chris

SJH

Me and John@Pace can electronically skew a ls6 maf flow rate to show 50% of normal flow. So you can run just 1 maf with no converter box.

I have extended my ls6 maf to the 512 limit for now. 67 lbs/min peak is just about right for my combo.

Steve

ChrisB

The problem with using one math is the physical range of the sensor itself. At a minimum you decrease your precision by an order of two - and infact, at flow levels over 400-450 g/sec the MAF itself just isn't very precise. (I ran a few on a flow-bench with a frequency counter). The confidence value went from about 95% in that range to about 75 and below once you get over 450 g/sec. Not really good enough for goverment work even <img border="0" title="" alt="[Sad]" src="gr_sad.gif" /> . Even if you skew the output by a factor of two you still are relying on the sensor to physically meter air up to 1024 g/sec - at which point the precision would not be very good. With a two maf setup you could keep a confidence value of 95% all the way up to 800-900 g/sec of flow.

Chris

SJH

Yes 1 maf may have some drawbacks with a 50% reduced flow report.
And at the 1000hp level, I suppose it will be a physical air restriction possibly. A ported ls6 maf is a full 85mm though, so it will have a large flow potential.
I have already run a ls6 maf reduced around 50% though for quite a while N.A..
It suffered no drivability problems at all from cutting the resolution in half.
The problem then(before we had ls1edit) was that of the calc load being way off and messing with ignition timing and A4 trans line pressures. But ls1 edit could take care of that now as you mentioned.
I would run a peak of around 24lbs/min when the motor was really seeing 45 or so.
I also played around with large dry n20 shots with this method a couple years ago with mixed success.
Steve

ChrisB

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by SJH:
<strong>I have already run a ls6 maf reduced around 50% though for quite a while N.A..
It suffered no drivability problems at all from cutting the resolution in half.
</font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif"></strong>

Your granularity is reduced by a factor of 2, but it probably will not be that noticable when you keep the airflow down.

You are still NA, so at a 1/2 rate you probably don't see much over 150-175 g/sec - or 300-350 g/sec actual. This is within the MAF's dynamic range. If you were a blown vehicle and extending that range then you would see the problems - again, I ran it on a flowbench and under ideal conditions the maf wasn't accurate at much over 450 g/sec.

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">
The problem then(before we had ls1edit) was that of the calc load being way off and messing with ignition timing and A4 trans line pressures. But ls1 edit could take care of that now as you mentioned.
</font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">

Yep - just reduce the cylinder size by a factor of 2.

Chris

SJH

I was N.A. when I ran that combo for testing.We were running it that way as we ran 42lb(50 or so at 60psi) injectors with stock 28lb injector programming.
I have been blown for a year now on my 98ls1.

Right now we reduced the ls6 maf flow rate to match a 512gm/sec pcm flow limit, which I can hit.
Since a 98 ls1 pcm can only go to 11250HZ and a stock ls6 meter reads only 365gm/sec at that frequency, we had to reconfigure that table to peak at 512gms at 11250hz and match the maf to that

Right now it looks as if all works very well up to the limit(67lbs/min).
When you graph out the maf flow, it's a nice smooth climb with rpm to the upper limit. It's totally repeatable.

Beyond that, I have no idea. I won't be messing around with any maf flow rates beyond this level on my own motor as I have 4 mechanical alky injectors for further fuel flow.
Hell 1/2 the guys here run maxed injectors as it is because they are to small, essentially running mechanical efi systems.
We could sell a modified ls6 maf to match a 512gms/sec table if there was any interest.

Steve

MIGHTYMOUSE

iTrader: (59)

what do all the other mass air cars in the world do that flow more than this? can we adapt one of their sensors etc? (mustangs)

what are the limits of running in just speed density? higher/lower than the maf limit?

ChrisB

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by MIGHTYMOUSE:
<strong>what do all the other mass air cars in the world do that flow more than this? can we adapt one of their sensors etc? (mustangs)</font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif"></strong>

The system the mustang uses for MAF determination (sampling tube) makes it easier to calibrate for different ranges - but it isn't as accurate/precise. At big power levels they simply go to an aftermarket fuel injection.

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif"><strong>
what are the limits of running in just speed density? higher/lower than the maf limit?</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">The MAP is only 1 bar (0kPa - 100kPa (atmospheric)). You will not be able to differentiate any airflow levels of positive pressure - and you won't have the maf to crutch you up to 400-500g/sec. If you are flowing serious air I would suggest running a FAST setup in a piggyback configuration.

Chris

Godspeed

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">The MAP is only 1 bar (0kPa - 100kPa (atmospheric)). You will not be able to differentiate any airflow levels of positive pressure - and you won't have the maf to crutch you up to 400-500g/sec. If you are flowing serious air I would suggest running a FAST setup in a piggyback configuration.</font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">What about keeping it in SD and installing a 2 or 3 bar MAP sensor and connector it to a microcontroller that scales it to the PCM's 1 bar scale, then tune the values accordingly in VE tables.

<small>[ August 20, 2002, 12:16 AM: Message edited by: Godspeed ]</small>

ChrisB

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Godspeed:
<strong>What about keeping it in SD and installing a 2 or 3 bar MAP sensor and connector it to a microcontroller that scales it to the PCM's 1 bar scale, then tune the values accordingly in VE tables.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">You don't need a microcontroller for what you are wanting to do - most map sensors output across the same voltage range - they just cut the resolution in half - e.g. on a 1 bar 2.5v is 50kpa, on a 2 bar 2.5v is 100kpa, on a 3 bar 2.5v is 150kpa, etc. (range being 0-5v).

Couple of problems - the computer does a baro check on key on - with a different map sensor your car would think you were running at 120,000 feet or something absurd. Now if you use the microcontroller to skew the key on baro reading you are getting somewhere.

The problem is no one really has any idea what else this will effect - the only way you could know for sure is to try it out yourself. The other factor is that VE tables are limited to 100%, and there is no PE vs. MAP table for power enrichment - so you really aren't much better off than with a 1 bar and hacking the PE vs RPM.

What would really work well is if someone (harlan <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" /> ) impliments the dual MAF concept - a microcontroller which summed up 2 maf readings and then divided the value in half - using the above-mentioned trickery to allow the pcm to process it correctly. The would allow proper dynamic fuel and timing control.

Chris

Godspeed

Couple that with one of those high impedance to low impedance injector driver converters boxes and we are set. <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />