1987ZTPI

does anyone kno how to dissasemble the mass air flow sensor on our 85-89 tpi cars i want to cut down the aluminium fins so i can pull a little better air flow. As of now that is the biggest restriction in my intake, any help would would be appreciated i did a search and found nothing.

vipershark11

iTrader: (6)

you probably wont gain anything from this and may end up messing up the sensor.

Mike89GTA

badazta87

iTrader: (1)

I did not disassemble mine to cut the fins. just put a couple layers of duct tape on the ends and slip the hack saw blade through the maf. You really have to be very careful doing this and the maf will be fine.

Vader

You can remove the fins, since they are only there to cool the electronics package. Bosch really didn't know what they were doing when they engineered the MAF, since we all know that electronic devices don't need to dissipate any switching heat, anyway.

You can also remove the end screens, since they are only there to break up laminar airflow at part throttle (for a more accurate reading) and protect the hot wire sensor from sonic shock originatig in the intake at higher throttle angles. Since you always drive your car at WOT and probably don't need the MAF to report air flow. it should be fine.

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Perform a SEARCH. You'll find lots of members who have cut the cooling fins in their MAF sensors, as well as removing the screens. If you make a note of those members' names, and search further, you might find a good number of them who later post that they are having "inexplicable" Code 33 and 34 errors, poor idle, and poor part throttle response.

Since there is a better than 50% chance that you will end up buying a new MAF anyway, you might as well leave the OEM MAF intact and purchase a new MicroTech MAF as a replacement (the current replacement for the old Wells SUJ-145). They have no fins, no real "screens" in the duct, and have a slightly larger cross sectional area than the OEM Bosch MAF. That way, you'll have a lifetime warranty on your new MAF, and still have a working spare to keep or sell to the highest bidder.

Or, you can cut away and tell us how well it works later. Just in case you need a visual aid:

1987ZTPI

thats awsome thanks for the pic when i tried pulling apart my maf i only found the 3 screws on the outter edge and the 2 big 1's inside the bottom of the housing and it seemed like there was still something holding the unit together because it would pull apart a bit but i could never it to come apart and i didn't want to force the unit too much so i just put it back together and it still seems to work fine . what was nessecary for you to pull you maf apart. i have descreened my unit already but the stock unit only flows 550cfm i think that seems a little restrictive for a performance motor, where would i find this micro tech mass air flow sensor i've never herd of that brand befor just the granatelli units.

LAFireboyd

iTrader: (3)

Micro Tech MAF:

http://www.partsamerica.com/ProductD...pe=473&PTSet=A

It's brand new, not remanufactured like most replacement MAFs. And its price is very reasonable, costing much less than a GM/Bosch replacement.

Its price used to be much lower. So I'd guess the increase in price must've been because of the increase in demand for it, as it seems to have become the replacement of choice in '07.

navyCM

iTrader: (3)

have you used this? if so how does it work?

LAFireboyd

iTrader: (3)

I haven't use it, no. But it's the one I'll be getting to have onhand for when or if I ever change my MAF.

Vader compares it to the Wells MAF, which I think he liked a lot. So I'll take that as a confirmation that it's a good one. I'm not sure who came up with the design first, Micro Tech or Wells(maybe they're even the same company today), but it was Micro Tech who got it patented, and that seemed to coincide with the end of the Wells brand MAF, IIRC.

And another moderator(don't remember which one) got one sometime in '07. There was a thread topic about it. It was exactly at that time that the price increased from $170 to its current $230. So he might be someone to contact about its performance.

customblackbird

iTrader: (15)

dont bother modifiying the stocker. just go aftermarket. i never heard of the MICRO tech MAF, but i just got a granelli high flow for xmass and it was only 250$ and no shipping theres no hot wire and nothing in the open area of the MAF. they guarrenty 45% more airflow, and its adjustable for tuning. ive seen cars get 10-15rwhp mostly on stock LS1-LS2's tho.

i'll post sum pics if u want of the inside

Vader

I have a Wells MAF on my '86 and have installed a MicroTech MAF on a TPI conversion - They are identical. If you used the SEARCH feature of the site, you would have been able to find more information on both hot wire and thick film transistor MAFs than you ever wanted.



The original Bosch MAF (not Delco) used round wire screens. One is in the inlet end to delaminate the passing air to allow a more accurate sample, the other is at the outlet end to help the sampling and to deflect sonic shock waves generated in the intake tract from lean backfire and at wide open throttle from valve opening events. These shock waves can weaken the fragile platinum hot wire.

The Wells/MicroTech MAF uses a thick film transistor mounted to a single flat circuit board in the airstream to dissipate sensing heat to the intake air rather than a hot wire. It can nearly survive a hammer blow. The aftermarket MAF inlet "screen" is actually a flat metal matrix (honeycomb) which presents a lot less air flow restriction, yet still breaks up the inlet air to allow for correct sampling. The matrix design was borrowed from the factory LT1 MAFs. It also has a slightly larger main body to allow more air flow. The Bosch 14094712 MAF has a cross sectional area of 5.965 in², with an inside diameter under 71mm. The Wells/MicroTech MAF has a cross sectional area of 7.036 in², wirth an inside diameter of 74mm in the short dimension and 76mm in the wider dimension (it's slightly oval).

Along with the lager diameter, and considering the lack of the restrictive wire screens, sample tube, and heat sink fins required by the Bosch unit, they just flow more air. Add to that the fact that the replacement is far more durable, plus they are usually about the same price as a remanufactured hot wire MAF (and sometimes less) it doesn't make a lot of sense to play around with the stock Bosch unit.

Regarding disassembly of the Bosch MAF, there is a silicone sealed-on cover over the electronics package, a layer or thermal/anti-oxidation gel on the circuit board, four screws holding the electronics to the main body tube, and the electrical connections to the sampling tube have to be desoldered and uncrimped from the circuit board.

I've been there a couple of times. I actually replaced a burned hot wire in one unit, but the platinum alloy I selected was evidently not quite correct since the eventual output signal was significantly lower than it should have been. Working with 41 Ga. platinum/nickel wire is not a lot of fun, especially when it is resistance welded to the end connectors and wound through the supports. At about $22/foot for the wire, I spent more than a few dollars just trying to get the resistance weld process right.

You may have more patience, and a better source for the wire, but I found it more effective to just replace the MAF and end the problem.

Beyond that, unless you have something pretty special going on, you may not actually need a lot more MAF flow.

Vader

Your engine is a four-stroke cycle, naturally aspirated overhead valve piston engine. The theoretical displacement of the eight cylinders of the engine totals almost 350 cubic inches, or about one-fifth of a cubic foot (0.2025463 cu. ft., to be exact). Since your engine is a four-stroke cycle design, it can theoretically flow that amount of air on every two revolutions - one complete cycle for every cylinder. If your crankshaft spins at 5,000 RPMs, that would mean 2,500 complete cycles for every cylinder, or 506.365 cu. ft. every minute. If that same engine achieves 6,000 RPM, the theoretical flow would be 607.639 cu. ft. every minute.

Again, these are theoretical numbers. This assumes that the intake valves actually are removed from the ports, and the valve sizes are 4.000" intake and 4.000" exhaust - the same as the bore. The intake and exhaust ports would have to be the same size to assure no restriction and maximum air flow. The throttle body would have to have two 3" bores to accommodate 1.414 (square root of 2) cylinders on an intake cycle at any given time. If all these things were true, the air flow into the engine would be 607.639 cu. ft. per minute at 6,000 RPM. The stock MAF would then be a restriction, since it can only flow 544 SCFM without creating more than 0.01" W.C. static pressure drop.

This would be in a theoretical world. In the real world, the valves are only as large as the combustion chamber design will allow, and the intake and exhaust ports are significantly smaller than the 4" bore of the engine. This means that there is a significant decrease in theoretical flow right at the heads (more on that later).

Next, the only way the cylinder can fill with a fuel/air mixture is if there is a vacuum in the cylinder to draw the mixture in, and a slight push from shock waves created in the tract. The air in the manifold can't "wish" its way into the cylinder. To create a vacuum, even a slight one, the piston must travel down in the cylinder while the intake valve is open. This means that some of the theoretical displacement of the cylinder has been "wasted" to create this vacuum. So even though the cylinder volume may be 43+ cubic inches, you'll be really lucky to get 40 cubic inches of air/fuel mixture in to it, even with the theoretical 4.000" intake valve. And since the intake valves are nowhere near that theoretically ideal size, and the ports offer restriction of their own, the volume entering the chamber on even a very well-designed engine is more like 75-85% of the theoretical displacement (that's called "Volumetric Efficiency" in most circles - VE).

Additionally, these theoretically ideal valves would have to completely open the instant that the piston started on its downward stroke, and instantly close when the piston reached the bottom of its stroke (actually, a few degrees after that, but close enough for argument's sake). Since our small valves open and close very slowly in relation to the piston travel, there is additional loss and restriction. To compensate, the valves are opened a little sooner than the theoretical optimum, and close a little later to ram that last little bit of air/fuel mixture into the cylinder.

Farther upstream, the intake passages in the manifold and/or runners are nowhere near the size they would need to be to feed the engine at its theoretical maximum flow. The same holds true for the throttle body and ductwork. All of these passages would have to accommodate the 4.000" size for a zero-restriction system. This would mean that the MAF would have to be somewhere in the range of 4.756" (120.8mm) in diameter. Since it is only 70mm in diameter, it should be restrictive!

Factor in all the losses on a real-world perfectly designed engine. This engine would have at least 2.20" valves and the cam timing would have to be at least 50ºBTDC intake opening to achieve maximum intake flow at that RPM. The exhaust valves would have to be 1.80" minimum, and the individual matched head pipes would have to be tuned and megaphone-belled at about 10-15" to make the most scavenging action at that RPM. (Is this beginning to sound like a top-fuel engine? - It should.) Intake passages would have to be as short as possible to provide the least possible restriction and tuned length.

With all these things in place, the 350 cubic inch engine would flow around 534.722 cubic feet per minute at 6,000 RPM. Your stock engine is nowhere near that efficient in flow. By that determination, the 544 SCFM of the stock Bosch MAF should provide enough flow for your engine to achieve 7,000 RPM easily. The thick-film sensor replacement should support even more.

z 28 jari

iTrader: (1)

Is that Microtec maf compatible with -85 ecm or is it 86-89 only?

LAFireboyd

iTrader: (3)

It's compatible with all GM '85-'89 5.0 and 5.7 liter TPI engines.

customblackbird

iTrader: (15)

lol that wells MAF looks exactly like my grannelli maf....

LAFireboyd

iTrader: (3)

That's the adjustable one, right? Micro-Tech makes it too, so that's why.

Reviews I've read on here by people who've used it haven't been very good. But it's supposed to work well, so I'm thinking the people who've tried it just haven't set it correctly. But that's just a guess that, I'm sure, someone will take issue with, lol.

customblackbird

iTrader: (15)

yea the grannelli is adjustable, its just alil white tab thing that ur turn thats in the base. i wonder how much the adjustable wells MAF is? i hope its not more than what i paid for the grannelli since the basically look the same.

grannelli also offers MAF that are cold air tuned but i havent seen any for our applications

LAFireboyd

iTrader: (3)

The "Wells" brand doesn't exist anymore. It's only Micro-Tech now.

But I wasn't saying Micro-Tech also makes an adjustable MAF. I was saying that Micro-Tech is the manufacturer of the Granatelli MAF.

1) The Micro-Tech site says they designed and manufacture the only adjustable MAF available.

But while they don't specifically say it's the Granatelli MAF, or even that they make the Granatelli MAF...

2) They do have an affiliation with the Granatelli "name" in other areas of their parts manufacturing.

So putting 1 and 2 together...

shocker89bird

I agree with everything Vadar said except one thing and that is the screens on factory massairflows(on any vehicle) serve another purpose which is where there name comes from and it is WOT silencer, they are designed for factory vehicles to quiet the amount of noise under WOT. Just thought I would add that. this is from memory but I don't recall where I learned it so just take it as more of an opinion. Some cars seem to benifit from it but not all of them since the maf is calibrated assuming the screens are there.

tequilaboy

I have had some issues with my Micro-Tech MAF, mainly related to the calibration and inlet air temperature sensitivity. I've gotten it to perform well, but not without some effort and some eprom tuning.

Fortunately, I had alot of data on hand available for comparison from my Bosch MAF, before it failed.

• In general it over estimates airflow in the mid-high flow region resulting in an extra rich mixture under heavy throttle compared with an OEM Bosch MAF.
• Noisy signal output also in the mid-high flow region that can lead to erratic fueling unless filtered and limited.
• Poor inlet air temperature compensation results in relatively rich running (Low BLMs) at lower air temperatures and lean running (higher BLMs) at higher air temperature. More of a problem with cold air intakes. This is the most frustrating issue.

To avoid the high temp lean-out and remain safe when in open loop, I've tended to calibrate my MAF flow tables for the highest ambient temperatures that I'm likely to encounter. Say mid-90s summer heat.

I try and tune for 128 blms at this temperature. Under cooler temps I can live with the richer open loop and lower blms in closed loop.

A 20 degree change in ambient temp is fairly significant and may drop the blms by 10-15 counts or more. My car would run consistently richer in the morning when it was still cool, compared with the afternoon when it was hot. Rich in the mornings, lean in the afternoon. Forcing one to tune for conditions or find a compromise.

Unless your scanning and tuning and can stay on top of the calibration on a regular basis, proceed with caution with a Micro-Tech MAF especially if your running near the top of the MAF's range or using a cold air intake. My present "MAFless" tune may be more consistent than the Micro-Tech. Its certainly not much worse.