KrisW

iTrader: (5)

Okay, guys, here I go again.

I'm searching the TPI forum a lot. I see people wanting to switch to speed density, and that's fine, but I want to run my MAF system. LT1 guys do it, LSx guys do it. Why can't we upgrade to a better MAF?

Is there something in the ECM that limits this? Doesn't the maf send a certain signal (like 5v dc reference or something) based on air flow/temperature and don't the newer mafs do the same thing?

What is keeping guys from upgrading to the bigger LT1/Vortec/LSx MAF units?

Is there anything that can be tuned in to the ECM to allow this? Will I have to run a 1993 LT1 ECM to do this to a TPI car?

I'll go back to searching now, but I'm not finding much... am I looking in the wrong place?

Thanks guys.

KrisW

iTrader: (5)

Okay, I just read something about a translator? Can someone explain that to me?

Street Lethal

iTrader: (16)

^... Click Here, Click Here and Click Here....

KrisW

iTrader: (5)

Excellent...

doc

The main reason why people want to go away from MAF and go to MAP is the restriction of the MAF sensor. TPI MAFs w/o screens flow 658 CFM,,, and its well up the intake tract. So, in order to make bigger power with strokers and such poeple make the switch from MAF to MAP.

The reason why us TPI guys can not use an LT1 MAF is the language of each type. That is where the MAF translators come in. Apparently, you can use an LT1 MAF with the translator and the computer will be friendly with the input.

I got around the flow restriction and language mismatch by building my own large TPI MAF sensor. I cut away the plastic outer tube of a factory MAF sensor and mounted the electronic gutts into a 3.5" OD aluminum tube. I then had to reprogram the EPROM chip to indicated the proper airflow thru this larger tube. Then, the next restriction was the outlet of the twin airfilter airbox. I cut away the outlet tube and body-fillered in a 3.5" OD tube to match the new larger MAF sensor. This whole thing works great for me.

KrisW

iTrader: (5)

How did you re-program your EPROM? What exactly did you do? I am interested in doing what you did to my car...

Thanks!

ploegi

I would love to see some pictures of your modified MAF..... Sounds like a really good idea.

doc

I can send you pics by email if you give me your email address.

KrisW: You have to become very good at programming your own Eprom chips. The 165 computer in my '87 car has six flow tables. What I did was to increase the scalar value for each table. For the same count value out of my home made MAF I was getting alot more air into the engine by about 38%. So I had to adjust the MAF tables by 38%, in this manner I kept the BLM about the same. I used TunerPro for this,,, in the past I had always used C.A.T.tuner, but I heard now that he was bought out.

doc

pics maybe

doc

pic try again

ploegi

Looks interesting, and easy to do. Would probably also be a way to get around the 255gm/sec limit, as it will be flowing MUCH more air, for a given reading, as compared to the stock unit..... Hhhhmmmmmm.

From the angle of the picture, (thank you very much) it appears that the sensor portion is not centered in the tube, does this affect accuracy very much? I also see that you elected to leave the heat sink fins in place. I have read, but, not actually seen... that the heat sink is not really necessary, and can be shaved off for even better flow in a stock MAF.

How difficult was it to modify? Any reliability issues?

doc

1) The most difficult part was mating a 3.5" dia tube to the flowlid. With a 3.5" OD MAF, the next restriction is the flowlid (airbox) outlit. This job required some fabrication.

2) This does nothing to "get around" the 255 gm/sec limit. Everyone makes such a big deal about this, it is rather un-important,,, because at WOT, we have a table that feeds more fuel by RPM & temperature, they are:
"Power enrichment VS RPM" and "Power enrichment VS coolant temperature".
Be use of these tables, we can appropriately feed fuel to the engine above the 255 limit. This large MAF still has the 255 limit, but I do not see that as a limitation.

With the correct MAF table scalars, I am getting the right amount of fuel while cruising around, that is where I need the MAF to do its job. The drivibility is very good. With tuning at WOT being help by a wide band O2 sensor, I am not running either rich nor lean at WOT. When the MAF hits 255, it stays there, and I tune WOT by these other two tables.

3) Concerning the accuracy, the metering tube is not centered. I let the BLMs dictate the scalar values when I switch out my MAF sensors. I recorded the BLMs that I had in several fuel cells with the factory MAF, then after switching MAFs, I tuned the MAF table scalars so that I acheived the same BLMs. I thought that this process (even though a bit tedious) is the right way to go about it. I did not have to fudge the fuel injector constant to get things right. Therefore, I have the correct flow characteristics up to 255 gms/sec.

4) About flow rates: a factory MAF w/o screens is known to flow 658 CFM with 6.424 sq in of flow area. I estimate that my 3.5" MAF is flowing about 908 CFM, about 38% more that the factory MAF w/o screens.

KrisW

iTrader: (5)

That is an awesome mod, doc, you are to be commended.

Thank you and I will affectionately refer to my future MAFs as "doc MAFs" after they are installed, when people ask me what it is!

Now I just have to dive fully into tunerpro and all of it's requirements...

ploegi

How much air does the stock MAF think is flowing thru when it hits the 255gm/sec limit? (CFM) I am lousy with conversions.

At what RPM would a stock 350 hit this flow number?

Given that your MAF flows 38% more air, I would assume (and please correct me if I am wrong...) that the max rpm,(before hitting the 255 limit) for a stock motor, would rise in the same manner, with your maf installed. Or, you could install a larger displacement engine, which would compromise the stock maf even more (a lower max rpm before hitting 255), with fewer issues.

I understand that at WOT the computer basically ignores the MAF, that is why I am curious about the RPM. Given that I had a tendency to cruise at 100+ mph on the freeway, at 3:00am, being able to do so, and still get "reasonable" fuel economy would be fun. That, and I am just curious about it..... (sorry to be such a pain.... my GF tells me I am very good at it, and my theory is: Stick with what you are good at..... )

doc

KrisW: thank you for the compliment. I think that what I accomplished here is very important to making big Hp with a thirdgen type MAF. This large MAF gives you the drivibility and is not as a big restriction as the factory MAF. And it works within the 256 framework of the stock ECM.

Ploegi: Hey, you're in Adrian, we will have to meet this Summer!

255 gms/sec equates to 451.567 CFM. The conversion factor is 0.5647: to convert CFM to gms/sec, multiply the CFM value by 0.5647 to get gms/sec. So, at 452 CFM, the ECM can support about 348 engine Hp or about 304 RWHp. (I am using a rule of thumb that it takes 1.3 CFM to make 1.0 engine Hp, got this from an engine buildup book.)

The factory MAF is reported to flow 518 CFM and w/o screens 658 CFM. If you look at these numbers, even the factory MAF can run out of its 255 limit. But to do this in the real world, many intake parts has to be changed. When new, my IROCZ made 230 engine Hp,, that means that the engine was processing about 300 CFM. Therefore, in stock trim, my 5.7 IROCZ was not hitting the 255 resolution limit of the ECM.

I think that the peak Hp was at about 4800 RPM, so this is not very high. I am trying to get my tranny to shift by itself at 6200 RPM, but I am struggling with the govenor on this matter. I remember back several years where with a ported plenum and SLP cast runners and an Accel intake, the car fell flat on its face at 130 mph at Michigan Internation Speedway. I do not know my new max speed, but I do know that my best trap speed at Milan has been 113 mph.

I can not remember right now what triggers the ECM to go into PE. BTW: I am pulling about 6,000 RPM at the end of the 1/4 mile in 3rd gear with 3.70s in the rear end (9 bolt car ratio). So for your cruising at 100+ mph, I can only assume that you would stay in PE mode, but at steady cruise at that speed maybe you wont.

DSmith

HEY DOC

I would love to see a picture of the air box outlet and also one of how the sensor is mounted in the pipe.

Thanks, Dewayne

ploegi

Sounds like a plan! Would love to see you/your car. I may, or may not... still have mine. I need the money more than I need the car, so, unfortunately, it is for sale.

Ok, so, near is I can figger.... which is questionable accuracy..... A 350 cubic inch engine consume about 100 CFM, per 1000 RPM.

350ci / 2 (four stroke engine) /1728 (Cubic inches to cubic feet) =.101273

Round it to .1, just for ease of use.

.1 (factor determined above) * 1000 (engine rpm) = 100

This assumes 100% volumetric efficiency, which we all know is certainly not the case with a normally aspirated motor.... Given the above, it would seem that the MAF sensor stops being usefull at around 4500 RPM. Again, assuming 100% VE. So, lets say the engine is 80% efficient.... that would yeild a max accurate air flow at around 5600 RPM. IF that is correct, I can see GM's reasoning for the 255 gm/sec cap..... as the engine gets more efficient, that number would be lower, but, for a stock 350, it appears that the MAF could remain accurate, all the way to redline.... Interesting.

Am I somewhere in the ballpark here?

If the above assumptions are correct... with a 38% increase in airflow thru the maf, before hitting the 255gm/sec reading, the increased size maf would support accurate flow numbers over 7000 RPM.... Wow.

doc

Give me your email address, I will send a pic of the completed air box, sitting next to the factory unit. My pic is too big to post here, and I could not down size it.

Ploegi: Your flow equation is same as mine, which I recently posted under the this TPI board for the guy wanting to biuld a 383. It goes like this:

350 cu.in / 1728 x peak cam RPM/2 = ideal air flow

350/1728 = 0.20255 now times 6000/2 = 607 CFM is the ideal flow of a 350.

As you stated this is ideal, multiple by 80% effecientcy and we get 486 CFM.
It takes about 1.3 CFM to make 1.0Hp, therefore we get 374 engine Hp from a 350 with a cam producing peak power at 6000 RPM. So, as you stated, the 255 gms/sec limit does not come into play unless the engine is modified somewhat extensively.

DSmith

dewaynesmith05@yahoo.com I thought about doing this a couple years ago but never did because I wasn't sure how to mate the sensor to a bigger pipe.

Thanks for the help,
Dewayne

ploegi

We are in agreement then? Amazing! I did it right..... Will wonders never cease.....

But, that brings up the question of: Why did GM decide to ignore the MAF at WOT?? (can I throw a few more acronyms in here?) It seems to me, that reading actual air flow, and determining pulse width given that information, would be more efficient than simply using theoretical values, "guessing" as it were.. a fairly accurate guess, yes.

But, I suppose, on the other hand, "efficiency" in this case, would be better fuel economy, and not necessarily more power. Which, at WOT (alright! another acronym..) is certainly not a primary concern..... (fuel economy)

Anyone else have thoughts on this?

Could you post the pictures of the airbox please, Doc?

doc

I did not say that GM ignores the MAF at WOT, did I?

I think that the ECM calculates a base pulse width even at WOT based of the flow thru the MAF sensor (even if its pigged at 255 gms/sec), then applies the PE fuel amount. The ECM should go into PE mode long before 255 gms/sec of air flow is reached.

I sent the pic of the flow lid to DSmith by email, maybe he can downsize it and post it here.

I think that we are way off course now on this thread. We should start a new thread to continue these thoughts & questions.

ploegi

I think the original question was answered with the first three posts..... then we got kinda... um... sidetracked..... Might just as well continue in that vein, as opposed to starting another thread, lot of good information in here.

So does the ecm pay attention to the maf at wot? If so, then it would seem to me that this is still a good idea. Especially for those with modified engines, that hit the 255gm/sec cap fairly quickly. If nothing else, just for the increased flow capacity.

doc

Pic of factory and large MAFs and flow lids.

neagan

iTrader: (7)

Doc's Mega MAF is absolutely amazing! Interestingly enough, there's another member of this board who is putting together a larger air box; one that fills up every millimeter of the space between the twin filters and the hood.

I personally have been rebuilding most every inch of my 88 IROC and have spent months just studying up how best to improve and modify our suspension's before I dug into replacing every single part (which I just finished). I also spent several months learning about TPI systems so that I could maximize porting techniques for moving as much air is possible into my SVO injectors. I'm having a proffesional performing the final touches to my Edlebrock base and already maximized the mega porting of the SLP runners & Plenum. Before I take on learning how to make my own PROM chips, I'm studying up on ignitions.

Doc, could you possibly share with me/us more in layman's terms everything you've noticed about your drivetrain's performance and general effects of this Monster MAF you designed? Mileage, how much quicker your engine wound up to redline, thoughts about Torque effects, etc????

I'm going to make this thread a personal 'sticky' for when I can get to this area. My family thinks I'm absolutely nuts for pouring the amount of time, details and $$$$ into this car; especially when I could have bought one already modified for far less than doing one up by scratch. However, it has forced me to go from the abilities of a part's swapper to someone who can diagnose and visualize why some stuff improves our F bodies. Damn there's still so much to learn!!

Again, it would be a big help to get your view on the overall effects of your design. All I currently know about my MAF system is that there's been an ongoing argument on this board over just the wisdom of removing one or both of the screens!!!!!

When I finish my IROC and show up at my local dragstrip, I want to have maximized every possible ounce of L98 horsepower while the engine looks so very stock and ordinary....
Thanks for sharing your photo's and PROM info with us; that was pretty damn generous of you.....
Sincerely, Nitro-Nicky

doc

neagan: I like the name "Mega MAF", it has a nice ring to it!!!

Concerning the removal of the screens: I dont see the issue here, 1) there are plenty of LT1 and LSx aftermarket MAFs with no screens, they do not suffer from design flaw. 2) the screens are a restriction, the diameter of the screen wires subtract from the total flow area, 3) removing the screens create laminar flow, which will always lead to increased flow as opposed to turbulent flow. Every time I see a wire or any kind of object put into a laminar flow tunnel, the air flow turns turbulent around the object. (I am so sick of hearing people claim that the screens create laminar flow, these people have never work in a wind tunnel.)

My 395 cu.in. stroker has an ideal airflow rate of 743 CFM (for a cam that peaks at 6500 RPM). A screenless TPI MAF flows around 658 CFM (I posted this somewhere, right now I cant remember the exact value). With all the talk of MAFs being a restriction, I wanted to remove all doubt in my mind that my search for more Hp was not being restricted by the MAF sensor, so I built this Mega MAF, a factory measure part stuffed into a 3.5" OD aluminum tube.
This MAF should flow about 900 CFM. My 52mm TB has been reported to flow about 898 CFM also. The next restriction appeared to be the flow lid, as measurements showed to me. Therefore, the flow lid was modified also.

Benefits of Mega MAF: The engine seems to run a little harder (better) to redline. I have never measured mileage, no concerned to me. However, I believe that this Mega MAF makes no difference to mileage, that would be involved in the tune and O2 sensor. My 1/4 mile time dropped only about 0.08 sec. Has each MAF/airlid combo been tuned to its best, No. I still have work to do in this department. I must install 30#/hr injectors as I know that I have reached 100% DC on the 24s.

I love the novelty of it all. I think that I have created something very special, maybe the first of its kind. You can not use the Mega MAF w/o being able to "burn" your own Eprom chip. So the creation of the Mega MAF has to go along with a large airlid and a special Eprom chip.

I need to paint that airlid, it can look alot better.

1bad91Z

iTrader: (1)

Doc, kudo's about your MAF, looks good! However, your lid still needs some work to get rid of restrictions. Enlarging the mouth isn't going to benefit you as much as enlarging the plenum volume of the entire base of the lid and raising the roof or bottom of the first bend after the filters. The first bend after the filters is the biggest restriction in the stock lid.

Good job, none the less!

doc

The largest restriction was the rear end round outlet (to the MAF). Now, I have replaced that with a 3.5" aluminum tube. Next to that restriction, is the inside portions as you mention, however, there are two of these. I do not remember what the inside dimension are, but I was satisfied that I had taken care of the worse of the air flow situation. It would be nice to lift the top of the air lid, that is a great suggestion. I will have to think about how to get this done, most effectively. Looks like more fabrication, I love that body filler!!!

VAN454

WOW!!! This is the sort of fabrication I love. Great work.

Daniel U

Doc, I love the "Mega MAF" as well as the modification to the "inlet". I have a fiberglass hood that would alow a larger "ceiling" on the inlet. I was thinking with som modeling clay and carbon fiber, I might have some luck on raising the cieling. I also have tried an air ram duct that sits behind the opening where my fog lamps used to be. They connect to where the air filter opening is. I'm trying to get my buddy to have them done in carbon fiber as front end wieght is always an issue with me. I'll try to get some pics as some may be confused as to what I'm talking about. Again, Kudos to the MAF!

doc

I have been using a ram air inlet to the twin air filters for about 10 years now. It's made up of one mold injected piece that I purchased 10 years ago,,, having an IROCZ, I had to remove the fog lamps to make it more effective. I think that that piece is resposible for a 2 to 3 mph pickup in trap speed in the 1/4 mile.

So, in all, I am running a ram air inlet, a MEGA MAF, 3.5" outlet from the airlid, 52mm TB, and the SuperRam which I ported alittle. What I need is a bigger intake manifold, or simply go with the Holley Stealth Ram in place of the SuperRam.

I avoided interference with the hood with the 3.5" outlet to the airlid by simply deforming the round aluminum tube into an oval. I also deformed the aluminum tube making the MEGA MAF into a matching oval at the leading end of the MAF.

rhead007

were can i find the wire diagram for the maf fbirds 4 wire i got one from an old blazer 95 it has 3 wires can this be used