Duts87ss

iTrader: (10)

Anyone else having problems with their Micro-Tech MAF and Burn-Off relay getting along? Car runs like pooh with the Burn-Off relay connected and runs great as soon as it's disconnected. This wouldn't be a problem other than the SES being on all the time because of the disconnected relay.

Is this a persistent problem with Micro-Tech MAFs or do I need to use the lifetime warranty and get this thing replaced?

Duts87ss

iTrader: (10)

Noone is using these anymore?

soultron

iTrader: (2)

I had that problem and never thought of just removing the relay....

Duts87ss

iTrader: (10)

Looks like we're two for two.

I took the Micro-Tech back today for a replacement. We'll see how well the next one works.

dustpusher

I have the same problem with mine.It dosent always run bad tho.I have exchanged it a few times and still the same problem.I have put a stock maf in and it runs great.I have tried to find out why because I have a new micro tech and would like to run it.

Duts87ss

iTrader: (10)

Thanks for the post dustpusher, but I can't say that I enjoy the news. Looks like this new MAF I picked up today isn't going to be very promising.

In the middle of an engine swap; so I want know if it works until the new engine is in.

8Mike9

Odd it would work better w/o the BO relay, snce the BO relay only comes on when the car/ignition is shut off.

Could it be the MAF is like the first ones GM used (early '85 IIRC) and don't have/need a BO relay?

dustpusher

I wonder how many people have had the same problem with this maf.It seems that if everyone has the same problem with them then they wouldnt be the maf of choice.I remember reading posts thet these were better than the bosch maf.

Duts87ss

iTrader: (10)

I think '85's used the same MAF as later years, but they used a piggy-back module to control them instead of the ECM.

1991CamaroRslow

iTrader: (3)

Is the B/O relay killing the mafs? Or is it causing them to just run odd? I've driven mine a few times with the Microtech and it runs great, the only problem I've had is getting it to stay running when I first start it, it wants to surge and stall for a few seconds then come out of it and act right.

Duts87ss

iTrader: (10)

I don't think the problem is with the B/O relay but with the B/O circuit. The MicroTech cant use the B/O circuit (thick-film MAF), but the ECM needs to see a complete circuit at shutdown to think everything is okay.

Have you tried disconnecting your B/O relay to see if your idle surges go away?

1991CamaroRslow

iTrader: (3)

The car idle surged with stock MAF's so I doubt it'll change anything. I've also never got an error code since the Microtech has been installed. What code are you all getting?

IROCThe5.7L

Did you get the adjustable one? I have a stock replacement (micro-tech) and it works fine.

Duts87ss

iTrader: (10)

Advance Auto Parts factory replacement unit.

dustpusher

Mine was the same.

pandin

There is no burn off required for the Microtech/circuit board/film type of Maf, the burnoff is only for a Bosch hot wire type.

Something to consider is that a Microtech reads more air then a Bosch does so the mixture will be richer, The one I have pegs at 255 grms/sec, when the new Bosch Maf only reads 215 grs/sec, same everything but the Maf. It makes the engine seem better but it is only running way richer, BLM's drop to 108.

Duts87ss

iTrader: (10)

Try disconnecting the Burn-Off circuit and see if it stops running rich...Mine does.

The new Micro-Tech that I got a while back acts the same as the first. I'm going to replace it with a reman. Cardone unit (reman Bosch).

I also called Micro-Tech customer service today. The guy told me to just try a third one and see if the same problem persists; if it does they'll have to do testing of the units. I told him about this thread and all he would say is, "Well, we haven't heard anything about it." So I recommend everyone with problems give them a call: 800-688-1588.

Pandin, after trying out disconnecting the B/O relay, and if the rich problem goes away, I'd appreciate you giving them a call also. If we can get them to correct the problem, we could end up with a great alternative to the hot-wire MAFs.

pandin

Installing the Micro tech, is the same as raising your Maf values, if your within a range that the ECM/bin can adjust for, then you will not notice any change. The BLM's will shift, but until you hit the adjustment limits, you will not "see" any difference at idle or cruise.

The "choke", open loop, PE will all be richer and more spark due to higher LV8.

Wells/microtech
Idle grs/sec 12 IBPW 3.5
Cruise 55 mph 1570 rpm 27 grs/sec IBPW 2.9 BLM 112
Wot 4500 rpm grs/sec 239 IBPW 13.6

Bosch
Idle grs/sec 8 IBPW 3.2
Cruise 55 mph 1570 rpm 22 grs/sec IBPW 2.9 BLM 150
Wot 4500 rpm grs/sec 186 IBPW 10.5

It is almost a 30% increase in fuel.

Maybe the "one wells" I have is bad, a new bosch was in the middle.

Duts87ss

iTrader: (10)

I understand what you're saying, but this still should not be the case with a factory replacement part. Of the people that own TPI vehicles, how many of them actually tune their own chips?

Like I said, mine did run rich with the B/O relay connected (black smoke from the exhaust), but as soon as I disconnect the relay, everything clears up and runs normal.

pandin

Within the BLM range there will be no black smoke. If you notice the IBPW are very near the same (idle and cruise). It is only when the rich limit is hit (108) that the ECM/bin no longer can adjust.

Maybe you where in Limp mode?

What are your "black smoke" BLM's reading (108)?

Try lowering the BLM limit to (80) to see if the ECM/bin can correct for the issue.

If the Wells/Microtech Maf is designed to be a plug and play replacement, why would you have to remove the burn off relay? This hasn't been stated in any posts about this Maf that I have read. Just stick them in and go.

If these were the hot setup, all you would hear on this board would be get one, but many have been tried and many either go SD or back to Bosch.

They seem to work fine on a more stock setup. I went out of range with a stock chip and 24# injectors with the change to 50# fuel pressure. At 43.5# (stock fuel pressure) BLM's where just in range (112) but at the 50# BLM's were maxed out (below 108).

I can try your theory, but can you try mine?

pandin

This is a very old story.

08-26-2003, 09:12 PM

#1 Bluevette85 vbmenu_register("postmenu_1458423", true);
Junior Member

Join Date: Feb 2002
Location: Latham, NY
Posts: 69
Car: 85 Corvette
Engine: 355 Superram
Transmission: 700R4 Transgo Shift Kit

Microtech MAF Calibration I bought a Microtech MAF from Advance Auto that fits 86-89 TPI cars (165 ecm). It is the film type and I believe they make them for Wells also.

The output voltage for all airflows is 0.3 volts higher than the Bosch MAF. I made my own air flow bench and compared the two MAF's. This results in a very rich condition with the stock MAF tables.

Is there a way to alter what incoming voltage the ecm sees? Could I put a resistor on the MAF signal line to drop the voltage by 0.3? I have reprogrammed my ARAP bin by changing the MAF table scalar values then adjusting the tables but I wanted to know if there was another way to make it work.

I returned the first Microtech but the second gives the same readings so they are programmed that way from the factory.

1991CamaroRslow

iTrader: (3)

Ever since it got cold my car is HELL to keep running. It will black smoke on the first few taps of the gas, but you MUST hold it at 2000rpm or so until the 02 sensors take over to keep it alive. This tells me this maf must be WAY out of adjustment. I really wish someone knew a baseline on where to change the MAF tables to compensate for one of these mafs.

pandin

It is in the post above yours .3 volts, lower all your Maf entries by the grs/sec that equals .3 volts.

At idle, in the lower maf table, it would be about 4 grs/sec. The difference between a new bosch maf idle, at 8 grs/sec, and the wells maf, at 12 grs/sec. Lower the .91 volts from 11.41 to 7.41 and see what happens.

At the same air flow a bosch will output .61 volts and the wells .91 volts so you have to slide all the numbers to match the true air flow.

You could possibly do it with the scalars, but I'm not smart enough to tell you, how to do it.

tequilaboy

When I was running a Micro-Tech MAF, I was always in the habit of continuously re-tuning for changing ambient temps. Since I was always tuning something just about everyday, this wasn't a problem for me.

A 20 degree swing in ambient air temperature would move the BLMS by about 10 points or so.

The trend was rich when cold and lean when warm. If I tuned it to be spot on for 90F ambient summer heat in the afternoon, it would be rich in the morning with the ambient air temp back down around 70F. This was really the only safe way to tune it. I didn't want it to lean out when hot.

You have to stay on top of the tune with these sensors.

Duts87ss

iTrader: (10)

I would, but didn't feel like fooling with it anymore and ordered a reman Bosch unit that I pick up tomorrow. Maybe some day down the rode I will experiment with it again.

BC GTA

I have posted my results this year with this type of MAF sensor. It is suppose to flow more air; however, many people have experienced problems with them. I went back to the Bosch type MAF sensor and will stay with it.

VAN454

So the bosch is the way to go then? Where is the best place to order a reman one? I have maf issues too and I don't want hassles when I get a new one

tony_cogliandro

iTrader: (3)

this was one of the most interresting tec posts i have read in a long time. sort of like a "who done it" novel.
i run a map unit but now i see the problem that can happen when you start moving parts around and mixing and matching supposed oem parts.

rgarcia63

A mass air flow sensor shouldn't have an issue with ambient temperature could internal heat be affecting the output circuitry?

When my Bosch failed I replaced it with a Microtech I really have had any problems, but after reading this post I've gotten curious, I know it smells rich on startup. I'll do some data logging and post unfortunately I don't have any Bosch data for my 388 to compare.

1991CamaroRslow

iTrader: (3)

It's 70 today I think I'll start the Camaro and see if she'll run without help.

Vader

I've installed a couple of the MicroTech MAFs after the Wells was no longer available. I've had no such problems.

The 1985 MAF is completely different, since it outputs a digital (frequency modulated) signal instead of the analog signal like 1986-up units. They are not plug-and-play.

1991CamaroRslow

iTrader: (3)

Temp makes a huge difference here, as stated earlier it was 70 today; I started the car up and it idled with minimal fuss. I ran quite good and idled really well. I still need to drop my MAF tables down a bit, I am planning to start really working on this once I get a wide band.

tony_cogliandro

iTrader: (3)

i almost got a maf system so i made some notes from articles i read. maybe it will help. SORRY FOR THE FORMAT, BUT THE NOTES WERE TAKEN FROM A NUMBER OF ARTICLES INTO A NOTEPAD THAT DID NOT FORMAT VERY WELL.

At hot unloaded idle, the MAF sensor reading in g/sec should be very close to the liter size of the engine. a 5.0 should read 5 g/sec.
If the MAF sensor reading in g/sec is higher or lower than the liter size of the engine at idle, check the fuel trim. If the fuel trim is good (±10%), then the MAF sensor is reading the airflow correctly.
If the fuel trim is greater than this, it's an indication of a problem. As the engine load changes, the dirty MAF element cannot give up its heat to the air flowing over it, thus it underreads the airflow. The fuel trim has to correct this airflow reading from the MAF sensor. It does this by multiplying the base air equation by the trim value needed.
Another example of a MAF sensor reading incorrectly is if the MAF sensor's Wheatstone bridge is out of range, the actual g/sec reading would also be out of range. Since the MAF sensor reading sets the fuel delivery weight, the fuel trim would correct the airflow. This would create out-of-range fuel trims as well. However, there's a difference in the way the fuel trims load on the chart; rather than going from a negative to a positive value, the fuel trims stay linear. In other words, they stay very close to the same percentages from the bottom of the chart to the top. In this case, the MAF sensor would need to be replaced.
Mass flow fuel injection utilizes a sensor placed in front of the throttle to measure the mass of air inducted into the engine. This type of system is used on GM tuned port V8s through 1988.
Mass flow fuel injection systems use a Mass Air flow sensor (MAF) to measure the mass of the air being inducted into the engine. Intake air is ducted past the MAS which measures total air flow in one of several different ways depending on the type of MAF. The most prevalent type is the hot wire sensor pioneered by Bosch. The hot wire sensor routes air flow past a heated wire (hot wire). This wire is part of an electronic circuit that measures electrical current in milliamps. Current flowing through the wire heats it to a temperature that is always above the inlet air temperature by a fixed amount.
(see picture attached) MAF sensors use an exposed hot wire to measure air flow through the unit. Air flow changes cause voltage change as the ECM attempts to maintain the calibrated wire temperature. The ECM interprets voltage changes as specific air flow changes.
Air flowing across the wire draws away some of the heat, so an increase in current flow is required for it to maintain its fixed temperature. When air flow is low (idle) little current is required to heat the wire to temperature. At high air flow (wide-open throttle) it takes a lot of current to heat the wire because heat is being removed from it more quickly. The current necessary to heat the wire is proportional to the mass of air flowing across the wire. A temperature sensor in the MAS provides a correction for intake air temperature so that the output signal is not affected by it. A circuit in the MAS converts the current reading into a voltage signal for the Electronic Control Module (ECM) that converts it to grams per second. The output of this sensor is not linear with respect to air flow; it is sensitive to low air flow and less sensitive at high air flows. Idle speed air flow is typically about 4 to 7 grams per second, increasing with rpm. The hot wire is made of platinum and is sensitive to contaminants or deposits, therefore, it is super-heated after engine shutdown to burn off any contaminants or deposits.
Mass flow fuel systems measure the mass of the air directly, so there is no need for the ECM to correct for air density. Other inputs to the ECM include a throttle position sensor and an O2 sensor for closed loop air/fuel ratio control. Once the ECM knows the amount of air entering the engine, it looks at the other sensors to determine the engine's current state of operation (idle, acceleration, cruise, deceleration); then it refers to an electronic table or map to find the appropriate air/fuel ratio and select the fuel injector pulse width required to match the input signals. Finally, the ECM energizes the fuel injector for the appropriate number of milliseconds to inject the fuel. On a GM tuned port car, the sensor readings and subsequent calculations are made at a rate of 160 calculations per second to ensure high accuracy.
A mass flow fuel system adapts easily to changes in the engine as well as hardware because air flow is measured directly. In other words, a mass flow system is self-compensating for most reasonable changes to the engine and is extremely accurate under low-speed part-throttle operation. The downside is that the sensors are expensive and sometimes unreliable. Many MAFs also provide a considerable restriction to air flow in high horsepower engines, limiting their power (between 300 HP and 350 HP). The mass flow system found on many high-performance GM cars (Corvette, Camaro, Firebird, Grand National) simply cannot read high air flow values, thus the combination of air flow restriction and the loss of the self-tuning feature causes many people who want to build very high horsepower (in excess of of 325 HP) engines to change to speed density fuel systems. The Accel Power Process is designed specifically to support this change, allowing a complete conversion on GM cars.
As used in 1985-89 TPI engines, the mass air flow system supplies the ECM with information about the amount of air passing through it. If the ECM sees large amounts of air flow, it indicates acceleration, wide open throttle or high power demand, while small amounts of air indicate low power demand, deceleration, or idle.
The MAF used in 1985-89 TPI systems is a Bosch hot wire type where current supplied to the sensing wire attempts to maintain a calibrated wire temperature. The current will vary with temperature and the ECM interprets this as either an increase or decrease in air flow. The ECM supplies a current-limiting five volt reference source on the MAF signal line. The MAF will pull the voltage low, to about .4 volt with low air flow and as high as five volts with high air flow. Accuracy is maintained by a MAF burnoff circuit that briefly heats the sensing wire to about 1000 degrees after engine shutdown to burn off contaminants.

Duts87ss

iTrader: (10)

Guys, I feel pretty stupid. I have a bad relay that was causing my problems. It failed in the closed position so that it's sending battery current all the time, even with engine off.

I've already replaced the Mirco-Tech unit with a reman Bosch, so I'll use it for a while until I'm ready to replace it. The Bosch is probably better for me as I'd like to make a 3.5" Maf later on (once I getting tuning this 383 under control).

Pandin, I especially apologize to you.

tony_cogliandro

iTrader: (3)

i was wrong too.
i just read that MAF will be used on some of the 2009 camaro's. don't know if it was true. i think it was a road and track i was reading in some office someplace.
we will see.

VAN454

So does this mean you are selling the micro-tech? If so I may be interested

Duts87ss

iTrader: (10)

I returned the Micro-tech under warranty to get the reman. Bosch.

rgarcia63

So, which relay was it?

Duts87ss

iTrader: (10)

It was the relay that I was using for Burn-off (I have one of S10Wildside's custom harnesses; MAF, B/O, FuelPump all use the same type of relay).