Is This MAF bad?

[GeoTalon91]

After working on and off on the 91 1G Talon. I finally got it too idle a bit smoother, however I have a few questions, that perhaps a few of you can help me with.

First, I am curious if this MAF is bad, seeing as how the cardboard insulation is lifting off. (See Pic)

Should I leave it alone? Look for another MAF? Or take the Cardboard insulation off? For now all I did was just flatten the cardboard back up with my finger and left it in there.

The idle used to be very rough, but I changed some vacuum lines, and injector o-rings that were leaking. In the process I broke off one of the bolts that holds the fuel rail to the head, the one that is closest to the throttle body. Any ideas on a fix for this or should I leave it alone for now? I checked all injectors and o-rings with the car on and none of them are leaking so the seal is good (this may change once I boost though).

I also added a new boost gauge and an NSX Manual boost controller. While I was at it I adjusted the BISS and set the idle for about 900-800 RPM. (I still need to set the timing on the car).

At this point my main concern is the MAF, any thoughts on this?

Thanks

 

[We're on Boost]

I've never used a 2g MAF, but the advice to use a 2g MAF with 550cc injectors sounds reasonable. Jeff Oberholzer told me that the 2g MAF sends out a signal about 30% lower (lower Hz) than a 1g MAF at the same airflow. So just putting the 2g MAF in with no other changes would lean you out about 30%. Going from 450cc to 550cc injectors would richen you back up by about 22%. So you'd only be a few percent leaner than stock then, at the same fuel pressure. Really it's a little more complicated than that because MAF Hz versus airflow is not linear. But 2g MAF with 550cc should be decent.

 

[NHerron]

And plus the maps at WOT are pretty rich anyway. A little leaner at WOT wouldn't hurt. Closed loop wouldn't matter either, it would compensate via trims.

 

[We're on Boost]

Ok I found the stock 1990 MAF that was on my car when I bought it, and took some pictures.
There definitely is cardboard in there. It is not loose or peeled off or anything weird. This is looking into the outlet end of the MAF.

So, as far as what happens when you take it out, I don't know.
But I know that this MAF is a Karman Vortex Sensor and you are looking at the guts of it right here. The round thing that I'm pointing at with a red arrow - that is basically a microphone. There is another mic just like it on the opposite side of the tunnel (to the right).

The black rectangular bar (vertical in the picture) in-between the mics is the "disrupter" which creates the oscillating wake which is sensed by the microphones. The frequency of that oscillating wake is the "Hz" that the ecu gets to figure out how much air flow there is.

The designers are going for laminar (smooth) airflow up to the disrupter. That's what the honeycomb is for. The cardboard I suppose has something to do with airflow or some acoustic purpose, maybe it is like a baffle board around the mics, I don't know.

One of the first "free mods" people used in these cars was to take the honeycomb out. I don't know if they also took the cardboard out. For that matter I saw an article in Hot Rod showing how to take the honeycomb off the inlet end of a GM MAF. These are half-baked mods in my book, and if you can go with either a 2g MAF, or a new, unmodified, genuine GM MAF, those should be better mods. Or, if you are going to stick with the stock downpipe in your exhaust system, you might never need more airflow than the 1g MAF can give you, in which case you could go with a good used 1g MAF - if you can find a "good" one. Mine looks good, but when I got my GM MAF going I noticed some improved running characteristics right away, even at idle and in ordinary low speed driving. I think these 1g MAFs were good hardware when they were new, but they are awfully old now!

Check out the Karman Vortex Sensor section in this article - very good!
[ame="http://en.wikipedia.org/wiki/Mass_air_flow_sensor"]http://en.wikipedia.org/wiki/Mass_air_flow_sensor[/ame]

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[/URL][/IMG]

 

[NHerron]

Cool info, this thread had turned out pretty good. Can you possibly modify the thread title to mention something about cardboard?

 

[GeoTalon91]

Try a boost leak test and spray real good around the intake manifold. Sounds like you have a good sized vacuum leak. Or if you can't do a BLT, run it and spray brake cleaner around the IM. If the idle raises then you've found the leak. But that's really not the best test, plus it's hard to tell on some leaks.

I bet once it warms up to op temp it gets back to normal right?

I'm either going to buy or try to make a Boost leak tester to further diagnose the problem. Question though, what is the IM?

Yea once it warms up it stays settled at about 9000 rpm.

Ok I found the stock 1990 MAF that was on my car when I bought it, and took some pictures.
There definitely is cardboard in there. It is not loose or peeled off or anything weird. This is looking into the outlet end of the MAF.

So, as far as what happens when you take it out, I don't know.
But I know that this MAF is a Karman Vortex Sensor and you are looking at the guts of it right here. The round thing that I'm pointing at with a red arrow - that is basically a microphone. There is another mic just like it on the opposite side of the tunnel (to the right).

The black rectangular bar (vertical in the picture) in-between the mics is the "disrupter" which creates the oscillating wake which is sensed by the microphones. The frequency of that oscillating wake is the "Hz" that the ecu gets to figure out how much air flow there is.

The designers are going for laminar (smooth) airflow up to the disrupter. That's what the honeycomb is for. The cardboard I suppose has something to do with airflow or some acoustic purpose, maybe it is like a baffle board around the mics, I don't know.

One of the first "free mods" people used in these cars was to take the honeycomb out. I don't know if they also took the cardboard out. For that matter I saw an article in Hot Rod showing how to take the honeycomb off the inlet end of a GM MAF. These are half-baked mods in my book, and if you can go with either a 2g MAF, or a new, unmodified, genuine GM MAF, those should be better mods. Or, if you are going to stick with the stock downpipe in your exhaust system, you might never need more airflow than the 1g MAF can give you, in which case you could go with a good used 1g MAF - if you can find a "good" one. Mine looks good, but when I got my GM MAF going I noticed some improved running characteristics right away, even at idle and in ordinary low speed driving. I think these 1g MAFs were good hardware when they were new, but they are awfully old now!

Check out the Karman Vortex Sensor section in this article - very good!
Mass flow sensor - Wikipedia, the free encyclopedia

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[/URL][/IMG]

Sweet! Real good info right here! I actually took most of the cardboard out as mine was loose all over the place. There is only a small amount of cardboard left, about an inch on all sides, that is glued to the honeycomb.

Thus far it has had no noticeable driveability issue's as a matter of fact it pulls real hard above 4000 rpm. Will check the plugs today to make sure Im not leaning out.

I have a GM MAF, just need to try and find a good priced translator for it, also thinking about getting a 3" downpipe as my flexpipe is leaking.

 

[NHerron]

Intake manifold

 

[We're on Boost]

I have a GM MAF, just need to try and find a good priced translator for it, also thinking about getting a 3" downpipe as my flexpipe is leaking.

When I first put in my GM MAF (3") I initially used one of the old wires in the OEM MAF harness as my ground (this went through the firewall and into the cabin). Later I did a "rewire" for the power (12v) and ground to the MAF. The new ground was a 16 gage wire only about a foot long going to a big bolt on the chassis. Before I did that it was leaning out at WOT. After, it was all good. I think it was the beefy ground that did it. I notice that ECMLink tells you to do the ground like that when you are using a GM MAF. Maybe they found the same thing.

When you put in a 3" downpipe, together with replacing the Cat with a "test" pipe, and a 3" exhaust, you will all of a sudden be hitting fuel cut. Because you will be over-running the stock injectors, the stock fuel pump, and the airflow will be over 2000 Hz which is where the stock ecu throws a fuel cut. The stock 1g MAF also goes to pot right around 2000 Hz. The GM MAF can go much higher. Anyway, you will have all those things I mentioned hitting the wall at right around 2000 Hz. So at that point, you need bigger injectors, bigger fuel pump, some MAF other than the 1g, and a modded ecu - like maybe an eprom ecu with a reprogrammed chip in it from somebody like member MY1GDSM.
And to check A/F you really should have a wideband O2 sensor!

When you say a "good priced translater" do you mean a used one? or a low-priced new one?

 

[NHerron]

A little info on the different Mass Air-Flow Sensors...

maffrequencylimits [ECMTuning - wiki]

When I first put in my GM MAF (3") I initially used one of the old wires in the OEM MAF harness as my ground (this went through the firewall and into the cabin). Later I did a "rewire" for the power (12v) and ground to the MAF. The new ground was a 16 gage wire only about a foot long going to a big bolt on the chassis. Before I did that it was leaning out at WOT. After, it was all good. I think it was the beefy ground that did it. I notice that ECMLink tells you to do the ground like that when you are using a GM MAF. Maybe they found the same thing.

I wonder how much current those hot wire MAF's pull to keep... the wire hot. I wonder if our stock wiring is too small and creating a small voltage drop. But I'd think it'd be adequate judging by the tiny 20 gauge wires I see on the stock GM pigtails...

 

[GeoTalon91]

When I first put in my GM MAF (3") I initially used one of the old wires in the OEM MAF harness as my ground (this went through the firewall and into the cabin). Later I did a "rewire" for the power (12v) and ground to the MAF. The new ground was a 16 gage wire only about a foot long going to a big bolt on the chassis. Before I did that it was leaning out at WOT. After, it was all good. I think it was the beefy ground that did it. I notice that ECMLink tells you to do the ground like that when you are using a GM MAF. Maybe they found the same thing.

When you put in a 3" downpipe, together with replacing the Cat with a "test" pipe, and a 3" exhaust, you will all of a sudden be hitting fuel cut. Because you will be over-running the stock injectors, the stock fuel pump, and the airflow will be over 2000 Hz which is where the stock ecu throws a fuel cut. The stock 1g MAF also goes to pot right around 2000 Hz. The GM MAF can go much higher. Anyway, you will have all those things I mentioned hitting the wall at right around 2000 Hz. So at that point, you need bigger injectors, bigger fuel pump, some MAF other than the 1g, and a modded ecu - like maybe an eprom ecu with a reprogrammed chip in it from somebody like member MY1GDSM.
And to check A/F you really should have a wideband O2 sensor!

When you say a "good priced translater" do you mean a used one? or a low-priced new one?

If I switch to a 3" DP and install the 3" GM MAF along with the translator and set the boost to about 8psi, can I still drive the car on the stock injectors and fuel pump?

Yea I'm thinking about a good priced used translator.

 

[We're on Boost]

If I switch to a 3" DP and install the 3" GM MAF along with the translator and set the boost to about 8psi, can I still drive the car on the stock injectors and fuel pump?

Yea I'm thinking about a good priced used translator.

Oh yeah, you should be able to let it go up to 11 psi or so.

The "basic" MAF Translator brand new is about $210:

STM: MAF TRANSLATOR | 90-99 DSM | 3000GT

It's worth keeping in mind that if you go with a GM MAF plus MAF Translator now, and then decide later you want to upgrade to ECMLink "Lite", you haven't exactly wasted your money on the translator. "Lite" needs the translator to work with the GM MAF. If you eventually get the full blast ECMLink though, that one can take the GM MAF directly (with their special cable), without the translator, and it doesn't cost much more than "Lite".

Here's a good place to read the basic stuff about ECMLink and ECMLink Lite:

STM: 90-99 DSM TUNING & ELECTRONICS

I wonder how much current those hot wire MAF's pull to keep... the wire hot. I wonder if our stock wiring is too small and creating a small voltage drop. But I'd think it'd be adequate judging by the tiny 20 gauge wires I see on the stock GM pigtails...

Yeah I've wondered why it should make any difference, because I don't think the GM MAF draws much current. Probably an amp or 2 is it, but I suppose you'd have to log current during a WOT pull because that's probably where it draws the most, and I've never done that.

I'm not sure it's the ground that did it either. Maybe the power wire made the difference. My "rewire" power wire comes right off the battery, so it is getting more than 12v, whatever the alternator is putting out at the moment, usually about 13.5 volts. I found a 40 amp relay that I think is very high quality (Radio Shack believe it or not) using the standard Bosch socket, and wired that in to feed the current to the MAF. The 12v wire in the stock MAF harness now goes to the coil of the relay to turn it on and off.
Anyway, that 12v wire in the stock MAF harness, I'm not so sure it runs at full system voltage (13.5) - it might be regulated to 12 volts. The GM MAF might be designed to run on full system voltage. This is just wild-assed guessing because I've never measured all this stuff with my meter with the engine running. But it could explain it. These little integrated circuit regulator chips are dirt cheap, maybe a buck and a half each. If you put 12 volts into a 12 volt regulator, you can only get about 11.5 volts out max - they drop 1/2 a volt. So if the GM MAF has its own built in 12 volt regualtor and you feed it with only 12 volts, I think something's going to be a little off. You know what I mean?

 

[We're on Boost]

Going to make 1 more wild-assed guess about the power wire in the stock MAF harness - why it might make a difference to get the "12v" supply right from the battery.

If the 12v wire in the stock MAF harness is regulated, the current would be limited, by the current capability of the regulator. So if the GM MAF draws more current than the stock 1g MAF, then the voltage in the stock wire would drop under high current conditions. There would be no such limitation taking unregulated power right from the battery.

 

[NHerron]

Well on the 2g, the MAS gets its power unregulated from the battery, via the MFI relay which controls power to all engine sensors.

If I had the time I'd love to look more into this kinda stuff more often but sadly I don't...

 

[We're on Boost]

Yep, same here on the lack of time.

If I get down to the garage with my meter sometime I might measure the voltage on the stock MAF wire under different conditions. Should be able to tell if it stays pegged right at some constant voltage, or if it varies like battery voltage does. That wire now only runs a relay coil that only takes 130 milliamps at 12 volts.

 

[NHerron]

Do you have a factory service manual yet? I would look up the diagram for you but my laptop passed away recently .

Here's where I downloaded mine from before I bought the original hard copies off ebay.
Mitsubishilinks.com

Also includes the parts program so you can enter you vin and get the right part number everytime.

 

[We're on Boost]

Do you have a factory service manual yet? I would look up the diagram for you but my laptop passed away recently .

I have it - yeah I see that on the 1g, there is a Red wire going straight from the MPI relay to the air flow sensor, #3 terminal in the connector. Cool - that would be unregulated then. So maybe it is the ground wire that made the difference.

Did your laptop ride around in your car a lot - logging? I keep expecting the hard drive in my laptop to crash from the hard ride it gets. The shocks and springs on my car are lethal. I'm thinking a nice solid state drive would be a great idea on any computer that you log with, instead of a disk drive.

 

[NHerron]

I do but that wasn't the cause. Funny though, the laptop has a built in warning it detects it had been jolted and asked to turnoff the HD. Got really annoying, I couldn't carry the damn thing without it flippin out, so I shut off the warning.

I really want to get an apple since they have that bootcamp program to run Win AND apple OS, plus they come with SS drives now which is just dreamy. Small size though - my music collection will fill up most of it.

I think apple is just engineered better hardware wise, I've repaire a lot of hand held electronics and ipod stuff is always flawless inside