Red Devil

Ok guys, here is the question. If a manfg. produced a MAF unit using the original circuitry, but increasing the diameter by 25% (this is arbitrary, I pulled it outta my.. er.. thin air I'll wait for some input on this number) could you still get by with your calibrated chip? Would an AFPR be enough to compensate or would you need a newer chip. If you incorporated a heated O2 sensor would the O2 sensor be able to sufficiently adjust the FI duty cycle to compensate? Or would you absolutely need a new calibrated chip along with larger injectors? Or any of the above singularly or mixed and matched? Let 'em rip!

Guest

Something would have to be recalibrated to let the ECM know there is more air going in. Otherwise, you are just lying to the ECM and it really isnt doing its job as designed. That means, in a perfect world you always change the chip when doing a mod. Of course we dont, and we mess with the timing and fuel pressure to work outside the computer.
In this case, I wouldnt do that, I would recalibrate. Keep in mind the table only reads to 255gm/sec, which IIRC is only about 420ish CFM, so beyond that you need a different calibration to provide proper fueling anyway. Someday, someone will mod the program like a certain Ford guy has done so the table doesnt stop at 255 and the ECM is capable of higher flowrates.

Red Devil

Max, are you refering to the calibration in the chip itself? What is the reason that the table stops at 255? Is it hard wired in the ECU or in the chip? Thanks.

Vader

RD,

Max is right. The extra air flowing around the MAF at WOT would be great for those who need it. The extra air would be a disaster during closed-loop, however, since the MAF would report (arbitrarily) 25% less than actual air flow, making the ECM control fuel for a lot lower intake air. You'd be lean forever, and likely be the Supreme Allied Commander of the Code 34 army.

RD is on to a possible mechanical solution, and Max is very close to a final solution for our ECM problems. I wish I could tell you more right now, but I can't (RD might have a clue as to why).

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Later,
Vader
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"Make Me Bad"
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Red Devil

Heh.. already had that one under the belt. I cheated and swapped out to F**D injectors to compensate... sorta.


My curiosity is working overtime now, I think I'll be making some calls in the following business days. Now then, Max, you wanna join a conference call?

Ok, back to the grilling to get a clearer pic...

If the MAF diameter is increased by 25% and airflow is increased by 22% (mind I'm not too good in fluid dynamics but we'll say about that) from the increase in diameter, could you have the chip calibrated to have the same increase in fuel delivery? Or rather, could you have the chip compensate for that extra airflow?

TRAXION

Anyone ever thought about using 2 MAF units and then researching the circuitry for the MAF to only send HALF of the signal back?

Tim

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TRAXION's 1990 IROC-Z
Best Time = 12.587 @ 107.97mph (1.710 60ftr) on the long runner setup.
All Natural. No Force. No Drugs. Stock Bottom End. Stock Body Panels. Stock Wheels. No Weight Reduction.
Gunning for NA 11's with the MiniRam II and Hooker LT Headers.
-=ICON Motorsports=-
Moderator: PROM board at thirdgen.org

Red Devil

The circuitry we've covered in a few posts, and you could probably pull this off (halving the signal) with an '85 set-up but I don't know how you would coordinate the signal from two '86 up MAF's. Also sending "1/2" the signal would then beg the same problem as increasing the diameter. You would also need to add on a new harness as well as the new ducting. That's partially why I'm chasing down the larger diameter option, no wiring or signal modification, just ducting work. This is the place for these questions. I think this is the site that has the biggest conglomeration of knowledge on this GM platform, which means it's the best place to hash out ideas!!

irocz

the Buick guys have an translator that lets them run lt1 3" and 3.5" mafs on their cars. So we know it can be done. I think that would be the direction to go.



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87 IROC-Z, 5.7, auto, 3.27, leather, !cat, Holley fpr, K&N'S, SLP 1-3/4" Jet-Hot coated headers, SLP cam, $uperPITAram, Edelbrock lower intake, Holley 52mm tb, Dynomax/Flowmaster catback
Coming Soon - Fasttrack/Accell DFI

1989 Pontiac 20th Anniversary Turbo Trans Am - STOCK (for now)
SOLD ->91 Z28, 5.7, 3.23, Ported Plenum, Accel runners & lower intake, Accel distributor module, !dual cats, POS Edelbrock catback, K&N'S, ram air, tb airfoil, !tb coolant

Red Devil

Ok, I've kinda heard about this, however, I can't find anything on the web about it. Their MAFs are the six cyl. type, so I don't think we could use 'em, but, I would love to find out the manufacturer and court them on the idea of making one for us. I don't know how this would affect the tables in the chips. Anyone have some info on this? Any links? First hand experience? Please post, I am really interested in defeating this gremlin.
BTW - Max, hows the LTR stuff coming? I may have a new idea for ya to try if you feel like putting something together. If your near MA we should hook up and compare notes. I'm basing most of the stuff on my little 383, but I'm sure this could be uased for any 8 cyl chev.

JETHROIROC

Doesn't Granatelli motorsports already make a better MAF for thirdgens, or am I thinking about the one they make for 5.7L Chevy trucks?

Guest

RD, right now I'm at a standstill. I'm in my last semester at school and dont really have the time to do what I want to do. The manifold base I did install on my TA before I changed the engine, and the Gtech I have showed a solid .5 difference. Before I yanked the engine I put the old original base back on and I lost the .5
I plan on taking another TPI car I have (Grand Prix) and running it on a dyno as is (stock stuff), with my modded base, and hopefully with an aftermarket part to be named later

Granatelli doesnt make a better MAF for our cars. There is a Wells unit that flows more, but the ECM is a limiting factor anyway. A translator might be an option at this point, the Turbo Buick guys seem to be getting away with it and reprogramming.

Red Devil

Max, every time we chat you get my creative juices flowing, as well as my curiosity! Five tenths is nothing to sneeze at at all! I'd be very interested in those dyno numbers. I wouldn't knock the G-Tech times either. Both times were taken with the same instument, so you can assume a very close to true value.

On another note. Anyone know the percentage increase in fuel flow when you swap out to Ford 24# injectors? (assuming the same rail pressure? Also, anyone any good in fluid dynamics? Man, now I wish I didn't cut class in college all the damn time!

Red Devil

TTT

Vader

The MAF translator (I believe once offered through Painless Wiring) was for the digital MAFs on 231 Buick engines.

Concerning the rescaling of a pair of analog MAFs, the circuitry to A/D convert, add the two signals with an op-amp, and D/A convert a scaled signal would fit inside a cigarette pack and cost about $50.00 in parts, tops.

A similar circuit to rescale the output of a larger MAF would do the same. The trick would be to measure the intake flow accurately to scale the new MAF output properly - a good use for the original MAF, I suppose.

You still aren't quite getting the solution. I'm working on an email to the Red Devil. We may have a business proposal that doesn't involve fiberglass bodies.

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Later,
Vader
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"Make Me Bad"
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Red Devil

Interesting. So far the best offer I got was to get the sensors shipped sans tube. I'd have to epoxy or bolt then to fabricated tubes and then fab the ducting.

I'm a waitin'! BTW the guy has yet to come back with a counter offer for the molds .

Ok, anyone else want to add to this? Maybe answer some of the questions above? Anyone have a definitive explanation on MAF operation? I can only get old archive searches working, so I can't seem to find that nice long post we had going on the diferences of the two thirdgen MAFs. C'mon guys I need some help on this here subject to make some things happen!



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If you have a problem,
If no-one else can help,
And if you can find them,
Maybe you can hire....
THE A-TEAM

BadSS

Men,, I'm soaking this in big time. I'm running a stock 305 chip in a 86 with a pretty hot 355 and 24# injectors. Dang thing will fly WOT (good plug burn), but the rich idle is killing me. Thanks for posting this discussion. It's got me thinking - - and I'd be interested in the product(s) if you all hash one/some out!!!

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86 IROC - 9.8:1 - 355, TFS twisted wedge heads, 218/228-110, fully ported GM base and plenum, SLP runners, 52mm BBK, 24# SVO, 1 5/8" Headman headers, 3" Dyno-max, TH350, B&M Megashifter, 245/45ZR17s on 212 Eagles

Jim85IROC

iTrader: (2)

Interesting. I'm running a pretty hot 355 and 24# injectors with the stock 85 305 chip. My car has all sorts part throttle torque, but falls on its face when I floor it. I think my knock sensor is playing dirty games, but the junk 32k prom (and stock to boot) sure isn't helping.



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BadSS

Jim85,,, I'm an old timer and a carb guy, so this is really frustrating to me. I can tune a carb,, including the computer quads. There's no programming involved there,,, so no problem. However, I'm at the point of no return and sunk way to much time and money into the TPI set up (more than I have to spend). I keep telling myself to hang in there,, especially since I've driven it with the TPI set up and know this thing will go,, and it can't help but get quicker with a properly calibrated "chip".

Wish I could help you,, I did however change every stinking sensor on this thing.

[This message has been edited by BadSS (edited October 12, 2000).]

irocz

Red Devil - check out www.modernmusclecar.com for the maf translators. Maybe they can help out w/ a program or something to convert the data stream to one our cars can read.



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87 IROC-Z, 5.7, auto, 3.27, leather, !cat, Holley fpr, K&N'S, SLP 1-3/4" Jet-Hot coated headers, SLP cam, $uperPITAram, Edelbrock lower intake, Holley 52mm tb, Dynomax/Flowmaster catback
Coming Soon - Fasttrack/Accell DFI

1989 Pontiac 20th Anniversary Turbo Trans Am - STOCK (for now)
SOLD -&gt;91 Z28, 5.7, 3.23, Ported Plenum, Accel runners & lower intake, Accel distributor module, !dual cats, POS Edelbrock catback, K&N'S, ram air, tb airfoil, !tb coolant

Red Devil

Hey Bad and Jim, you guys know your rail pressure?Start up a thread with both cars' info and let's see if we can rid ya of your gremlins! Have you guys shown any codes?

Red Devil

Allright, to revisit this lets cover some outstanding questions as well as some new ones.

-The 255 gm/sec limit of the MAF. ECU reason or chip reason?

-By the time the MAF reaches that 255 gm/sec. limit (on a stock 350) what % is the
throttle open? How about on a 383 or 400?

-Max, can you elaborate on this Ford guy??

-Can a chip recalibration compensate for the increased airflow even if it does not 'register' through the MAF?

-Anyone know the percentage increase in fuel flow when you swap out to Ford 24# injectors? (assuming the same rail pressure)?

-Anyone have a definitive explanation on MAF operation? I can only get old archive searches working, so I can't seem to find that nice long post we had going on the differences of the two thirdgen MAFs.

-Vader, wanna clarify this:
"...Concerning the rescaling of a pair of analog MAFs, the circuitry to A/D convert, add the two signals with an op-amp, and D/A convert a scaled signal would fit inside a cigarette pack and cost about $50.00 in parts, tops.
A similar circuit to rescale the output of a larger MAF would do the same..."

I can get access to a flow bench so I could get a few sets of numbers.

Red Devil

ttt

Jim85IROC

iTrader: (2)

My rail pressure seems to be a bit of a mystery. See. Nothing is ever easy. It is 45lbs no matter how far I turn the afpr screw in either direction.



------------------
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<A HREF="http://www.rit.edu/~jli4307/camaro" TARGET=_blank>
View the restoration of an 85 IROC</A>
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Red Devil

Have you checked it with the vacuum line pulled? If so I'd look at your AFPR and it's gasket.

Vader

The 255g/S is the limit of the ECM's ability to scale fuel to air, so it was the arbitray limit set in the ECM firmware, not the PROM.


That all depends on some other variables, like engine RPM, atmospheric pressure, and humidity.


Given adequate RPM, CTS, and MAT signals, at WOT, the ECM will deliver a maximum of 80% duty-cycle on-time of the injectors. At stock fuel rail pressure, this is the rated maximum output flow of the injector(s), either 19 lb/H or 22lb/H. The ECM firmware will not cycle the injector driver transistors any more than that 80%. The PROM has no control over this maximum, only the points between 0% and 80%.

Umm, 24lb / 22lb = 9% increase. An increase in fuel rail pressure can accomplish the same thing, to a point.

Are you certain you really want the WHOLE thing? I've got a pretty good novel going on MAF specifications and details...

A quad-input CMOS A-D converter has a standard range of 15V. A single CMOS cascade adder operates in the same range. A little experimentation with scaling can provide the correct biasing for the span and zero points of the adder, and the output can be routed to a quad D-A converter to feed the ECM through an appropriate pull-down transistor to yield the correct analog signal that the ECM expects. All of this is readily available at your local electronics supplier (mostly stock ECG components) and would probably suck a whole 10W from the vehicle electrical system. Ship me a spare dual-trace storage scope, function generator, and flow meter, and I'll get one together for you.

It's just not that difficult if you have the spare time. The problem is that the ECM will still only supply fuel up to the 80% duty-cycle limit, regardless of the air intake volume.

------------------
Later,
Vader
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"Make Me Bad"
Adobe Acrobat Reader 4.0

[This message has been edited by Vader (edited October 16, 2000).]

Red Devil

Yee gads!! Ok, I knew I liked you for more than your looks!! I need to absorb and then fix up some answers... er... questions... The only one that pops out at me was the SVO injectors. I was hoping someone would have a difinitive answer because the ford injectors are rated differently and I keep finding different numbers.
Also I have a call in to Wells... we'll see what that leads.