Bench testing a 1990's hot wire MAF and ECU

[Duck]

I'm having some very strange MAF behaviour on my custom buggy build. I won't share the details just yet as I have some more basic checks to do first, so please bear with me.

The MAF is "hot wire" type, has three wires, V+, Gnd and signal. The factory manual says to expect 1.0-1.6v at the signal wire (measured at the ECU) when the ignition is on, and 1.7-2.0v when the engine is at idle. Does this mean the ECU takes a 0-5v signal from the MAF? And if so, is it safe to feed a 0-5v signal to the ECU to check it registers the MAF signal correctly? I have full diagnostics module for this ECU and can see all ECU data.

Engine is Suzuki G16B (Vitara hairdresser model) 1.6l EFI 1998.

 

[Keithmac]

MAF is not the best load input for a buggy that's going to be driven though all sorts of mess imho.

Speed Density would be a far better staring point.

 

[Ubique]

The signal range will be 0.5-4.5V, anything outside of that will be tolerated, but set a DTC.

 

[Keithmac]

If you've altered any of the intake system away from factory on a draw though MAF system your calibrations in the stock PCM will be inaccurate.

 

[Ubique]

Also bear in mind that the IAT is only accurate with the engine running, that will also have a bearing on air mass calculation / calibration values.

 

[Duck]

If you've altered any of the intake system away from factory on a draw though MAF system your calibrations in the stock PCM will be inaccurate.

The original airbox and hose has been binned as it didn't fit the engine bay, and replaced with same diameter hose but in silicone. Is there anything that can be do to get the readings re-calibrated? It's a factory ECU, not configurable.

 

[Hotstuff]

I have never heard of a hot wire type MAF sensor being recalibrated.

If the MAF includes an IAT (sorry I can’t recall and need to check the workshop manual to confirm), that can be disconnected and a remote IAT with the same scaling installed.

Is it possible that the hot wire has been contaminated with oil from an aftermarket filter?

Could you buy a new MAF and look at it as a service component?

What happens if you disconnected the MAF with the engine running?
Some ECUs revert to a “get you home” alpha/N mode. If the problem that you are experiencing disappears then that might indicate a problem with your MAF.

 

[Duck]

I have never heard of a hot wire type MAF sensor being recalibrated.

I assumed so much. So if the air intake pipe has been modified how would I check if the MAF is still running right?

Is it possible that the hot wire has been contaminated with oil from an aftermarket filter?

Possibly, but more likely the issue is due to using a cheap £30 MAF.

Could you buy a new MAF and look at it as a service component?

This is where things get complicated. I just fitted a decent new MAF I'd bought a year ago in anticipation of the new airbox with dry paper filter, but it didn't work and immediately caused the ECU to shut down each time the engine starts. Now there are very few decent new MAFs available, all have to be imported from EU or US. On top of that when I first got the engine running two MAFs failed (before the oiled filter was fitted) in succession. So that's why I opened this thread. I've checked the wiring, checked for power spikes using silly-scope and checked the ECU isn't sending any voltage to the MAF signal pin (silly scope). All looks good. I've found a potentially decent new MAF, it's in the post, I'll fit it and hope all these issues with failed MAFs have just been a string of bad luck.

What happens if you disconnected the MAF with the engine running?

The ECU light comes on, the engine runs very poorly.

 

[ajlelectronics]

So if the air intake pipe has been modified how would I check if the MAF is still running right?

It should be irrelevant, the MAF will still be reporting what is flowing past its vane. You can test by monitoring the voltage appearing at the ECU, which should vary accordingly. You could move the vane through its range and you should see it change.

 

[Hotstuff]

I assumed so much. So if the air intake pipe has been modified how would I check if the MAF is still running right?



Possibly, but more likely the issue is due to using a cheap £30 MAF.


This is where things get complicated. I just fitted a decent new MAF I'd bought a year ago in anticipation of the new airbox with dry paper filter, but it didn't work and immediately caused the ECU to shut down each time the engine starts. Now there are very few decent new MAFs available, all have to be imported from EU or US. On top of that when I first got the engine running two MAFs failed (before the oiled filter was fitted) in succession. So that's why I opened this thread. I've checked the wiring, checked for power spikes using silly-scope and checked the ECU isn't sending any voltage to the MAF signal pin (silly scope). All looks good. I've found a potentially decent new MAF, it's in the post, I'll fit it and hope all these issues with failed MAFs have just been a string of bad luck.


The ECU light comes on, the engine runs very poorly.

I’ve heard negative reviews regarding pattern MAF sensors.

Have you ever considered using a stand alone ECU? It would give you freedom to adopt a fuelling system that you can get parts for.

Have you tried posting on Suzuki-forums.com?

As a fellow G16B owner, I’d be interested to see what MAF sensor you end up with.

 

[Keithmac]

It should be irrelevant, the MAF will still be reporting what is flowing past its vane. You can test by monitoring the voltage appearing at the ECU, which should vary accordingly. You could move the vane through its range and you should see it change.

Buy the sound of he has a Hot Wire Maf, not a Vane type.

The PCM will throw a code if the inlet system is significantly different to a standard setup.

 

[Keithmac]

I've run a GM (Saab) Hot Wire MAF a in Blow Through Turbo setup on my other car and it has been very resilient.

If you've already broken two or three then your either really unlucky or the wiring is not correct.

 

[Duck]

Have you ever considered using a stand alone ECU?

I figured that would takes months to learn and set up, would the ECU need to be "mapped"? Hopefully I can get the MAF sorted without an aftermarket ECU.

Have you tried posting on Suzuki-forums.com?

I don't think there's much action on them any more

As a fellow G16B owner, I’d be interested to see what MAF sensor you end up with.

Interesting. Did you know these engines are still available as aviation certified for light aircraft? And are used in Marine. A very under rated engine.

 

[Keithmac]

Pick up a MegaSquirt 2 and go Speed Density imho.

There is a learning curve to it but you will have a far more reliable vehicle by the end of it.

 

[ajlelectronics]

Buy the sound of he has a Hot Wire Maf, not a Vane type.

The PCM will throw a code if the inlet system is significantly different to a standard setup.

Yes, silly of me (again). However the same applies that the MAF can only report the cooling it experiences relative to the airflow, so a bigger input 'ole is irrelevant as the induction determines air flow rather than positive pressure.

 

[Hotstuff]

I figured that would takes months to learn and set up, would the ECU need to be "mapped"? Hopefully I can get the MAF sorted without an aftermarket ECU.


I don't think there's much action on them any more


Interesting. Did you know these engines are still available as aviation certified for light aircraft? And are used in Marine. A very under rated engine.

The Suzuki forum Vitara MK1 section is still alive but a little quiet. The regular posters are very knowledgable so don’t write it off as a resource.

Some stand alone ECUs do come with generic maps but mostly for popular models such as the MX5.
If you are considering FI then this would be a good way to include knock sensors, boost control, traction control etc.

I must admit though, if a reliable source of parts can be found, I’m a big fan of keeping it simple.

That is interesting; I was not aware of the popularity of this engine. That being the case then hopefully a reliable solution should be available.

I don’t suppose you’re located in the South East UK?

 

[Duck]

That is interesting; I was not aware of the popularity of this engine. That being the case then hopefully a reliable solution should be available.

I don’t suppose you’re located in the South East UK?

The aviation version of the engine will have a totally different control system, only the core engine is the same.

I'm in Surrey

 

[Hotstuff]

The aviation version of the engine will have a totally different control system, only the core engine is the same.

I'm in Surrey

I’m in Hastings; shame you’re not local, I would have offered to nip over with my MAF sensor for some spare part surgery.

It would be interesting to learn more about the aviation adaptations. I’ll look into it sometime.

Good luck with your investigation.

 

[Duck]

I’m in Hastings; shame you’re not local, I would have offered to nip over with my MAF sensor for some spare part surgery.

It would be interesting to learn more about the aviation adaptations. I’ll look into it sometime.

Good luck with your investigation.

You'd be welcome. I'm planning to post photos of the buggy soon. I just want to get the body panels done because it currently looks half finished without them.

 

[Keithmac]

Yes, silly of me (again). However the same applies that the MAF can only report the cooling it experiences relative to the airflow, so a bigger input 'ole is irrelevant as the induction determines air flow rather than positive pressure.

Intake tract design before the MAF can make a massive difference in it's reading, even clocking the MAF 90⁰ can alter the reading.