Evening all.. I'll be buying an Evoscan cable in the next few days and need to know a few things about them..

I'm running without an AFM, but the ecu has gone into limp mode and its now inhaling fuel. Can this be switched off?

Can the rev limiter be adjusted?

Can cold start timing (open loop) be altered desperately to closed loop?

How easily is the above achieved, if at all?

Muchos gracias!

Evening all.. I'll be buying an Evoscan cable in the next few days and need to know a few things about them..

You'll want the Openport 2.0 cable. Ecuflash allows you to reflash your ECU. This cable will work with evoscan too.


I'm running without an AFM, but the ecu has gone into limp mode and its now inhaling fuel. Can this be switched off?

What are you trying to achieve? Speed density hasn't been ported to magna yet. This isn't something that you can just turn off either, the ECU's code is based on the reading from the AFM - this is how it calculates load. At the moment, your ECU is effectively guessing what the load would be - and also ensuring that it's running rich to protect the motor. This is by design.


Can the rev limiter be adjusted?

Yes, quite easily.


Can cold start timing (open loop) be altered desperately to closed loop?

Without AFM, ecu will never go into close loop.

Correct me if I'm wrong but without AFM ecu is using throttle sensor for load calculation, not a good idea as that map is very basic and will flood the engine to protect it

Aftermarket interceptor ECU is running a map sensor. AFM is null and void, apart from the fail limp mode screwing with my fuel levels :/

Aftermarket interceptor ECU is running a map sensor. AFM is null and void, apart from the fail limp mode screwing with my fuel levels :/

Unless the interceptor is generating a suitable replacement for the MAF signal, you aren't going to make this work satisfactorily. The whole point of the interceptor (other than ignition advance changes) should be to adjust the MAF signal to get the stock ECU to increase the fuel flow (unless you're using something like a Prosequential which can drive the injectors directly, in which case you shouldn't have this problem).

Which interceptor are you using? From what I've gathered, any interceptor that can be used in an Evo should be able to generate the correct signal (which is a variable frequency AC signal, rather than a simple voltage proportional to airflow as with a hotwire MAF(AFM)).

See the thread in my sig for more info about the reflashing aspects of using the OpenPort cable.

Running pro sequential ^_^ my understanding is that it should control fuel mixtures completely independent of the AFM, given that it runs on the output side of the stock ECU and has the ability to tune off its own MAP sensor alone... but I have been known to be wrong.

If so this is going to do my head in trying to figure out wtf is wrong with the AFM.. as they seem to kind of half work.. and progressively fail hard. I've tested with 2 so far.

I should also note that the current tune was done with both AFM and MAP sensors connected, so it seems to have been relying on data output From both at the time. A retune should fix everything, I just want to get rid of the AFM error code and check engine light!

Hate the be the bearer of bad news, but from a disassembly perspective - it's impossible to eliminate the MAF with stock ECU.

The stock ECU needs some form of Load input. The stock rom calculates load using the MAF signal. There are also other tables that rely on the operation of the other sensors in the MAF (ie baro, IAT)

Evo guys have deleted MAF using a hacked rom that reads in a MAP sensor and generates a load value (google speed density). This fools the ECU into thinking it's still getting a correct load value, thus allows the ecu to use normal maps for lookup instead of using the limp home table for AFR values.

So you've got a few options (not aimed directly at yourself either, just in general)

*wait till speed density is ported to Magna ROM. This is easy in theory - but i never understood the obsession of eliminating the MAF - it's not a restriction like most seem to think. Unless there was incentive to port it, i dont think it would happen (ie give donations to relevant people for magna ROM dev - like the VR4, Eclipse, EVO, etc guys - WytWun and co have done some bloody hard work making defs and disassembling ROMs - it's not as easy as you think!) and also deleting the MAF is pointless IMO even with force induction. It's a bloody accurate sensor compared with others, and i actually commend how the karmen vortex sensor works. In some respects we're lucky to have a karmen vortex. Other sensors are just rubbish compared to it. i think it's only let down is it's size.

*remove the piggy back and just reflash your stock ECU - what you're trying to achieve can be done easily with the stock ECU.

*leave MAF alone - Piggy back doesnt produce the signal that the ECU is expecting, thus its going to go into 'limp' fueling mode

*complete aftermarket ECU

*get a piggy back that can produce the MAF signal - dunno what'll do this, but again why delete something that works so well?

Hope this helps.

My only reasons for wanting to remove it are that it stopped working and a replacement didn't help, and that the path from my air filter to blower JUST fits the maf in and doesn't allow room for a pipe to plumb in my oil and BOV lines. Its just a matter of convenience rather than trying to achieve some amazing gain or something.

Im thinking that if I get my tune redone with limp mode in place, then the only issue I'll have is an error code and an engine light, which Ill just remove the globe and live happily ever after.

Problem with limp mode, is the fuel map isn't as big, and it'll disable quite a number of functions like close loop mode, some idle routines, etc

How did you determine that your original MAF was broken? what symptoms were you having?

Why the heck do you guys replace MAF with MAP? Manifold Absolute Pressure is never going to be as accurate as Mass Air Flow. Motorbikes are nearly all MAP-based and their part-throttle fuelling is usually diabolically bad; it's only when you get to wide throttle that bike ECUs go into Alpha-N (Throttle position/RPM) mode and adds fuel based on a precalculated volumetric efficiency of the engine.

So I guess I'm wondering what is "so bad" about Mass Air Flow?? A MAF-based system is usually self-tuning: flow more air, add more fuel. Is there something about MAF and tuned engines or cold air intakes?

It is easier to tune a car with a MAP sensor, as you can use realtime engine load to ensure optimum mixture at any given load.

MAP sensor is more preferable on a high performance engine, whereas a MAF sensor is more suited to everyday applications.

It is easier to tune a car with a MAP sensor, as you can use realtime engine load to ensure optimum mixture at any given load.

MAP sensor is more preferable on a high performance engine, whereas a MAF sensor is more suited to everyday applications.

So you use a mix of Speed Density and Alpha-N at WOT? Sounds just like most motorbikes.

So you use a mix of Speed Density and Alpha-N at WOT? Sounds just like most motorbikes.

And performance cars?

Why do people keep thinking I have something against my MAF? :S As I said, I only want it resolved as it stopped working.

As for why it died.. the MAF was struck by something when I had a low mounted intake.. it was only when I relocated it when it died... my car wasn't holding idle, was badly hunting, and drove like shit.. as soon as I unplugged it all problems went away, bar fuel consumption and a little bit of hunting on cold starts.

The replacement MAF showed exactly the same symptoms so I have no idea what the hell has happened, it may be a coincidence that 2 were duds but I doubt it.

As an afterthought.. is it possible that the MAF being like 10cm from my blower could be causing it to go spastic from the turbulent air?

As an afterthought.. is it possible that the MAF being like 10cm from my blower could be causing it to go spastic from the turbulent air?
If the MAF is downstream of the blower, turbulence could possibly affect its behaviour; if the MAF is upstream of the blower, I doubt it. My understanding is that the honeycomb-like structure at the front of the MAF is intended to minimise turbulence issues, but I have no idea how effective it would be immediately downstream of a blower.

The maf is on the inlet side of things, but given that there is a dirty big vortex being created right after the honeycomb filter I could imagine issues

As an afterthought.. is it possible that the MAF being like 10cm from my blower could be causing it to go spastic from the turbulent air?

I have a book on tuning EFI systems which I just checked, and it specifically says that blowers, cold air intakes and all sorts of other stuff can make the MAF go mental. It appears to be the reason performance engines use MAP and IAT, as Dave said.

The maf is on the inlet side of things, but given that there is a dirty big vortex being created right after the honeycomb filter I could imagine issues

There is also an issue that can cause the stock ECU to shut the engine down - if the MAF output exceeds an RPM based threshold (the table that controls this is included in the ECUFlash definitions).

You really need to get an oscilloscope on the MAF output to determine if its working, as I don't think a multimeter will respond quickly enough (unless its completely dead). Have you considered the possibility that the connector or harness may be damaged? (which might explain multiple "dead" units)

Indeed I have made that consideration. If I had something I could use to identify expected output from each pin I'm go through and test them.. scoping is a little hard however... need to source one first :/

When I get a chance I'll mock up an extended intake pipe that places the afm further from the blower and see how it reacts. I'm really beginning to thing that this may be the issue in its entirity, but I'll never know until I test!

I have a book on tuning EFI systems which I just checked, and it specifically says that blowers, cold air intakes and all sorts of other stuff can make the MAF go mental. It appears to be the reason performance engines use MAP and IAT, as Dave said.

Granted, but i think it's how much piping is between the maf and the blower/turbo. My VR4 has plenty of piping between the MAF and the entry of the two turbos.

If it's short, i can see it upsetting it...


There is also an issue that can cause the stock ECU to shut the engine down - if the MAF output exceeds an RPM based threshold (the table that controls this is included in the ECUFlash definitions).

Very true... infact running the stock ROM will only cater for a load up to 100%, running boost is any value over 100%. you'll need the tables to be extended provided the stock MAF can handle it.

Not sure on the 3.5l ROM, but a 3l ROM has the MAF size hardcoded of 288g/s. So i'd imagine that this value would need to be changed in your ROM to calculate load correctly if you're going into positive load or if thats close the actual limit of the MAF, find a donor MAF from another car (VR4 is 429.2 for example). Wont know till you get your car running well without boost using stock MAF, then log airflow in evoscan as you hit boost.

Formula ecu uses to calculate load:
Load = z * y /65536
z= MAF Hz per Rev
y = MAF Size

scoping is a little hard however... need to source one first :/

Something like the DSO Nano (http://www.seeedstudio.com/depot/dso-nano-v2-p-681.html?cPath=174) would be sufficient.

That scope looks freakin awesome!

That scope looks freakin awesome!

I have a DSO Nano. It's great! Total cost was like $64 including delivery. Only problem with it is you'll need to knock up some probes of your own and hook these up to the DSO probe, as the maximum distance between the main probe and ground clip is 10 centimetres. Here's how to make them: http://www.dtec.net.au/Tech%20Articles/Automotive%20Test%20Probe%20Construction.pdf

Sorry, I should clarify I'm talking about the DSO Nano clones (DSO201) that you buy on eBay. The original DSO Nano V2 uses alligator clips and is a better design. There is also aftermarket firmware for all of these including the clones - google "BenF Firmware" for more info. I would buy the DSO Nano V2 directly from Seeed Studio - $89 with free shipping by the looks of it.

However, if you're an Apple guy I would recommend the iPad Oscilloscope hardware and software: http://www.oscium.com/products/mixed-signal-oscilloscope-imso-104
This is great because you get a nice big screen and it's much easier to view your scope traces than on the Nano's tiny screen. This product comes with one analogue probe and 4 digital probes; you will never use the digital probes on a car unless you break open the ECU and start tracing the motherboard. Seriously at that point you're into electrical engineering territory.


Once you go down the dark path of oscilloscopes though, then you need to learn about what the signals mean and what is "good" versus "bad". For this, I thoroughly recommend going to YouTube and subscribing to the channel "realfixesrealfast". These guys use a Snap-On brand diagnostic computer which is like $7,000 USD but what they do with it mostly is use the oscilloscope function.

+1 for DSO nano

So my supercharger trans belt snapped am I'm running NA for a while.. plugged the AFM in and it runs 100% fine :) Turbulence is a bitch! Now to rethink my piping setup, as well as order the twin BOV setup that I was apparently supposed to be running :/

So my supercharger trans belt snapped am I'm running NA for a while.. plugged the AFM in and it runs 100% fine :) Turbulence is a bitch! Now to rethink my piping setup, as well as order the twin BOV setup that I was apparently supposed to be running :/
Bummer about the belt, but good news that the MAF is okay and very interesting that the proximity of the blower (even though downstream of the MAF) seems definitely implicated!

Having similar problems with my setup, very experienced tuner spent 6 hours trying reflash my ecu. I'm only using maf, the issue is that he couldn't figure out why maf reading did not correspond with the actual air that engine was getting, car was runing rich so it was like air was disappearing once it went past maf (no I have no leaks) and into supercharger. He ended up basically using some ridiculous correction coefficients for airflow readings which made the car run like it should. He said that what he did simply makes no sense (this guy is as good as they get). Anyhow he also thinks its the supercharger, he doesnt thinks its the turbulence but instead vibrations and "whine" from the blower which are interfering. Im installing Cai tomorrow which will relocate maf to infront of passenger wheel. I'll let yous know if this was the issue.

Okay finally got the car to the tuner, and yes it was definitely interference from the supercharger which caused MAF to give out wrong readings. Get a CAI and relocate your maf as far as possible from the blower, i placed my one in front of the passenger wheel.