DAVE26: Your MAF sensor is located on the air inlet tract, normally immediately following the standard filter. It has wires coming out of it. It can be affected by oil used to coat aftermarket filters.

 

No

In all seriousness...

Adam last night in chat was saying he was getting 1%... on the gas analyzer at that particular rolling road...

Now He's either suicidal where his cars concerned............. ( NAAH *shakes head* NO WAY))

OR

*gasp* *horror* Eerrm the equipment wasn't exactly kosher

 

Richard,

Adam has a Link, so no AFM to worry about. His low CO/fueling, may be due to getting 100% IDC at 5000rpm :ek:

Larger injectors, and a re-map will solve the problem.

Mark.

 

Hi All,

I went to PE for a rolling road test a few weeks ago as I suspected something wasn't quite right as the acceleration seemed a little flat and my EGT's were a little higher than I'd like.

Some of you may remember a few months back when the car was reporting egt's of 955deg at 155mph and 930ish deg at 130+mph.

On the rolling road the car reported a CO2 of 5% which is on the weak side. I think it's been something which has been gradually deteriorating. After removing the maf and cleaning it the car made a CO2 of 3% so the car had to be driven off boost until a new MAF sensor could be fitted. The car made a CO2 of around 8% last time it was there when it made the 326bhp run.

Since changing the MAF the car is much smoother..feels a lot stronger through the revs and most importantly, even at 145mph the EGT's are not going beyond 870deg. That's over 60deg reduction in egt temps just by replacing the MAF.

I just thought I'd bring it to peoples attention just how detrimental to the engine a faulty maf could potentially be. It also didn't cause any obvious running problems like erratic idling and such like. My car is also an MY98 which isn't usually affected by induction kits. I can't blame it after nearly 60,000 miles of use, but it might be an idea to have modded cars checked out on the rollers on a more regular basis just as a precaution. In effect, it's very understandable with hindsight that an induction kit should affect warranty since it can be a very real threat to the engine. I will continue using mine since they offer good improvements but just thought I'd give a bit of food for thought and highlight the fact that the std jecs ecu relies on the maf sensor to control fuelling so a dodgy one will make the car underfuel.

Rgds
Nito

 

where could i find my maf sensor??

i have a MY93WRX
and am thinking of doing a rolling rd test very soon, can any point me in the right direction?? im in leeds.
a tel number would be fine

 

Wait a minute....

Poor old Adam was also complaining about his *leaness* on that particulaar RR


Mmmmmm


Now are you running..

Hot Film MAF..(MY99) or Hot Wire(My98) ??



I keep replacing the HF one's every 7 to 8 months .. Such is the price

 

Nito, how was the duty cycle on the injectors? You never said.

Dan

 

Hi Danny,

There didn't seem to be any facility on the select monitor to monitor injector duty cycle. There was one form of measurement for injectors but I didn't have a clue what it was showing or how it works..it certainly wasn't in percentages..maybe its just a Link thing, I had a look through all the functions and inj duty cycle didn't appear. However looking at my egt's with the new MAF in place and taking into account CO2 figures I may well continue running with my current injectors on the jecs. I think my next mod will be a Techtom MDM100 to monitor MAF voltage and knock correction!!

rgds
Nito

 

Can anyone tell me approx price of new MAF sensor fro UK98 ? - I thought they were v expensive - or can they be cleaned without risk of damage ? (Ignorance rules OK)
Stan

 

Select monitor directly measures injector pulse width, that coupled with the time available for injection will give you the duty.

"Link thing " .... thought injector duty was pretty fundental, my car showed 8% on the rollers but my max duty was 120% ... its not all about the gas analyser which can mislead you, especially those cars with large exhausts, the big exhaust fan at PE can cause some odd readings on cars fitted with large bore tail pipes as it "extracts" gas causing a misleading reading.

Incidentally both Motec and Link ecu's report the same injector duty for the same load points on my car. Just for comparitive info.

Maf ... both hot wire and hot film are prone to mis read if contaminated, hot wire can be cleaned, hot film not really. Not unknown for them to fail, Select monitor check at the regular service should pick it up (thats why its done). MAF is expensive but has to be considered a "consumable" especially if cars are uprated with exhausts and higher flow filters (panel or induction). Any MY maf can be affected.

Faulty maf can also cause a car to over fuel especially if the temp compensation cct plays up.

 

Hi Bob,

Thanks for the explanation. Sorry, I didn't mean to be derogatory about the link with the "link thing" comment, I just thought that the link reported duty cycle as a percentage whereas the jecs didn't.

Would the extractor fans at PE cause the gas analyzer to read weaker or richer I wonder, or is it just a case of it'll just cause some inconsistency either way? It's usually been consistent there on mine in the past. Also, how could I calculate duty cycle from injector pulse width and available injection time? Sounds complicated...especially without data logging. Is there a specific pulse width that it shouldn't go over or an easier measurement to determine how far overloaded the injectors are? I'd certainly like to find out my injector duty cycles and definately haven't ruled out fitting larger injectors but I want to continue using jecs for now so want to find out more first. How did you cope Bob with 120% duty cycles and how real a risk is it running like this? Any advice would be much appreciated.

Thanks
Nito

 

The PE analyser is only misled when a big tail piped exhaust is on a car and the sense pipe is not been pushed far enough into the tail pipe, Merv had to get out and sort it out when my car was on the rollers (HKS Hiper) but it is not normally a problem as they are aware of it and watch for it, as I sit watching the laptop and the afr meters at the time of the runs I do then I see the fueling as it happens whilst the analyser picks up what has happened (if you see what I mean) The extract fan at the rear of the workshop hepls pull gas away from the sensor and so it indicates lean in error.

At 120% my injectors are wide open all the time which means that they are not pulsing fuel and sit there getting hot, not to be recommended which is why I have some uprated ones to go in when I get time. Its not an issue day to day as I normally don't max the car on the road, there is no need to. I get away with it cos I mapped the injector timing to maximise fueling, otherwise it would be way too lean. I also tail the boost down to help it out abit, at 7000 rom my boost is down to 1.25 (ish) bar from 1.4/1.5. With bigger injectors I could hold a higher value for boost longer.

 

some thing does not make sense here, if the jecs ecu goes on open loop when on load, why would the MAF affect full power run ? i would have thought it would have only affected cruise (closed loop ).

sorry if the answer is too obvious for everyone

 

Guys,

Since the "hot wire" MAF sensor is the only one that can be cleaned, what is the best way to clean it ?

Carlos H.

 

Sam, try reversing that picture... off boost, it's the lambda sensor that comes into play, on boost, the standard ECU uses the MAF to calculate the mixture. The MAP is not used to alter fuelling with the standard ECU, but does play a role in the ignition timing.

You can see with that scenario that the MAF is crucial in this setup. If it reports less air than actually got through (lower voltage) than the car will run terribly lean.

It doesn't even have to be faulty ... a bit of water/oil that gets on it can temporarily make it read incorrectly, but you would never know unless the engine goes bang or you have a Lambdalink or Select Monitor at hand. But you would never see a CEL ...

With the Link I think (I'm not sure here) that one can "delete" the MAF sensor (or have the option to set it up that way), and use the MAP sensor to define the load zones. No more worries about a dodgy MAF, but in theory you can have a "finer" fuelling with a MAF than just with using the MAP.

1.2 bar is 1.2 bar for a MAP sensor, although the volume of air that is used with say a TD04L and a VF23 is rather different.

The MAF on <MY99 models was not as advanced as the MY99/00 ones, and maxed out pretty soon especially with a bigger turbo.

The MY01 works different still, but I have no understanding yet of what exactly it does.

 

thanks evil
the link ecu does not use the MAF sensor mine has been broken for over a year now , i found that out when i tried to put the standard ecu in once long time ago.

it uses the map sensor for mapping the fuel. but i don't see what is the porblem with using only the map sensor ? surely regardless of the volume of air, you will map the fuel through the lambda to get the right mixtures for what ever volume?


[This message has been edited by Sam Elassar (edited 27 August 2001).]

 

I'd also like to know how to clean my maf. Had a quick look today and presume it's the black box about 2" square right after my induction kit. Unclipped the wires, undid the screws holding the unit in but it didnt want to pull out. Am i doing this right? If not, what do i do? And once its out whats the best way to clean it? cheers pumpers. my93 wrx.

 

Any hints on how to clean a 97-98 MAF sensor (the wire type) ?????

Carlos H.

 

Carlos, sorry, was not ignoring you, but I'm not sure ... I thought that the MY98 MAF advantage was that it would "burn" the crud off whilst driving anyway. Do you have a particular problem with it ?

Sam, no problem using the MAP sensor. That was not what I was saying.

Air density and temps change all the time, and the MAP sensor would still see the same pressure most of the time (and thus fuelling). With a MAF, it's a lot easier for example to comply to environmental laws.

Pressure is not equal to volume, that's what I'm trying to say.

None of the two types of input for a fuelling map is better or worse ... and a lot of people feel safer to get rid of the MAF, given the fact that removing your resonator of fitting an induction kit may have strange effects on it.

If you throw in the Unichip, things get even more complicated ... the "base mixture" is defined by the standard ECU (read: MAF), but the fuelling load sites in the Unichip are MAP based. So it might well happen that you dump 20 % more fuel in through the Unichip at 6000 rpm / 1.2 bar, but that the MAF sensor has a problem so you add 20 % to a way too lean mixture (defined by the standard ECU) anyway, ending up with "lean as **** + 20% lol

This is why I would personally always advice against resonator removal or induction kits, unless you run an replacement ECU that does not use the MAF.

Hope this makes things clearer.

Theo

 

Nito,
Now that you have reduced your EGT's by changing the MAF sensor, can you tell us about your water temps ..... have they gone a lot higher on track days or under hard driving conditions ?

Carlos H.

 

Carlos, to my knowledge Nito does not take part on track days.

Dan

 

Thanx Danny .....

Carlos H.

 

Hi Carlos/Danny

I'm not a trackday regular..I've only done a handful of trackdays and since fitting the FMIC I haven't had the time to do any trackdays, I would also be reluctant to do any until I've had my oil cooler fitted since hard driving can bring on oil temps of 120-130 degrees at very high speeds which I'd like to reduce by at least 20 deg if poss! On the rollers water temp was 88degrees although I suspect this would be higher in hard driving. I haven't fitted the water temp sender yet and the factory gauge isn't much use...it never goes above the centre mark even if there's a 30 degree difference! I'll post more when I get the water temp rigged up.

Rgds
Nito