Blow through MAF does anyone have any experience.

[Davezj]

Hi all,
Just happened across this topic on other forums and wondered if anyone had tried it.

It does not seem to be recommended that a Karmon votex MAF (VR4 type) as it does not like raised boost pressure blowing through the MAF.

Maybe we could switch to a different type of maf.
I know the vr4 has the IAT (Inlet Air Temp) sensors and the BARO (Barometric pressure) sensor.

So it is not quite as easy as you might think.

Just considering this option as it would mean we could get rid of all the inlet pipework in front of the turbos. If you wanted you could just put a filter on the turbo inlet.


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[Nick Mann]

Huh?

You mean put the MAF between the Y pipe and throttle body?

Why would this be better than going to Vipec/Link and MAP?

[Davezj]

Depends if you £1000 burning a hole in your pocket.
If you can just move a MAFor replace it with a different on for £50 to £100 then I know what I would be doing.
Budget is key.

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[Nick Mann]

I've got a second hand MAP ECU 2 kicking around that you could have for not a lot more than your suggested budget!

[Davezj]

It is just a thought I am not saying anything is a better way to go than anything else.
Just wondered if anyone else had heard of, or new of any info on the subject.
I know I said a Jarman vortex MAF is not recommended as a blow through MAF but I have read of people doing it and saying it does work. But for how long I am not sure as the sensor in the MAF is quite fragile flexible foil. But still I might give it a go.

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[Davezj]

I was looking into designs get a voltage to frequency converter.
But not as easy as you might think.
But again it is something to try.


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[Louis]

Just a quick thought/question.
Our MAF is before the turbos, so they do not blow through the MAF!. The MAF only get atmospheric getting sucked through. (if some vehicles that have the MAF after the Turbos, then higher boost may damage their MAF)
Unless the rate of air being "sucked" through the MAF was the issue?, (just looking for clarification on your initial question)

Hi, sorry, re read your post and know what you mean now.

[paulg23]

I was looking into designs get a voltage to frequency converter.
But not as easy as you might think.

How about the CD4046 PLL. Has a VCO built in.

[Amonlym]

We have a few devices at work that convert voltage to frequency, I might have access to an appropriate design - what is the voltage and frequency range needed?
Alternatively, way back when in PC overclocking people used to make external FSB oscillators (using PLL's like the CD4046 as Paul suggests) that were pot controlled - one of those designs might be usable.

[paulg23]

As far as I can make out the MAF frequency output range is about 20Hz to 3000Hz. Could do it with an Aruino Nano.

[Davezj]

i had throught about using an arduino to manipulate a voltage to a frequency. but i dont think the output of the MAF is linear. so the 0-5V output of a MAP sensor can be

i would have to measure the freq output while blowing air through it with a hair drier or leaf blower or compressed air source . to see how the output changed with input air volume.

the voltage to frequency converter was to use a Manifold Absoulute Pressure (MAP) Sensor instead of a MAF. to do the same job as using a blow through MAF.
this would let me get rid of the inlet pipework and make more room under the bonnet for other stuff.

[paulg23]

Look up table would handle the non linearity. Fit a MAP and get an arduino to log MAP, MAF and RPM. Should then be able to see the relationship.

[Davezj]

paul, that is not a bad idea that would solve quite a few of the issues i have throught about.

that is really a cracking idea. paul. i feel a plan coming together.

[Confused]

You're describing exactly what and how a MAP-ECU works

They've done all the hard work - 2nd hand they're peanuts nowadays, so why bother with all the hassle when it's already all done, and done fairly well.

[paulg23]

i feel a plan coming together.

Let me know if I can help.

[Davezj]

I have another option that involves no effort at all.

use Evoscan.

you can already log RPM and MAF frequency i think.

so all i have to do is fit a MAP sensor and log that too. the data is saved into excel into a massive spread sheet of all the data so it should be easy to get a good feel for what map voltage should produce what frequency.



OK so what result would you expert. i imagine we would get a few different scenarios.

under max load as rpm increases mass air flow increases and so will frequency along with Map voltage increases as boost is generated.

under low load rpm increases mass air flow increases but not by much, so frequency increases by not much ,and map voltage is low as no boost pressure is generated as the manifold is under a small vacuum.

under lift off deceleration the RPM decreases relatively slowly, Throttle butterfly is closed so Minimal Mass air flow resulting in minimal frequency, Map voltage will be minimum as manifold will be under max vacuum.


i will have a look at Map ecu to see if it a viable option for me.
but it would be nice to offer a solution for the masses. rather than the few.

[Nick Mann]

......it would be nice to offer a solution for the masses. rather than the few.

Dave, there are not masses wanting to do this, only the few!

[orionn2o]

Dave, there are not masses wanting to do this, only the few!

Disappointing.... but true

[Davezj]

It doesn't really matter if nobody else wants to do it, I want to do it and if I can do it in a way that is cheap and easily repeatable by someone else then all the better for them.
It will be an interesting little project.


I know quite a few people are going down the link g4+ ecu (vipec ECU) route, but I am not one of them sadly.

I have enough to spend on my engine complete rebuild. Yes complete rebuild, it started with head gaskets then mushroomed from there due to the state of my crank bearing.
Which I only looked at because I could due to the engine being out of the car.
Apart from the exhaust gasses in the cooling system the car ran very well no abnormal noise or knocking, nothing.

But I know know the crank bearing are completely FUBAR 'ed

The only parts left in the block are the cylinder oil squatters on the 4 main bearing locations.

And i have been told that some of the con rod bearings I need will be delayed by 2 months and that is from amayama.

But I still have lots to do. Lots and lots to do.





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[swinks]

Dave, karman vortex sensor won't work in boost operated environment. Gas flow phisics. For that reason EVERY vehicle manufacturer is placing MAF sensor prior to turbocharger or compressor.
What you are after is simply MAP device which has been already tried gazillion times in Mitsubishi stock MAF and ecu operated vehicles. People who want to convert MAF to MAP simply need following (very very short description):
- MAP sensor (most popular generic GM 3bar from ebay approx. 7 GBP)
- IAT sensor (you need measure air temp as close to mainfold as possible), generic GM with M12 thread costs approx. 12 GBP
- cable patch from MAF socket to IAT sensor (for use of stock ecu iat input)
- use 1 free pin in ecu for map signal
- disable ecu input of maf baro and karman
Last time I spoke with Lee from Dynotech, he said that ecu from VR4 can't be much different to ecu's from Evo 4-6 (phisicaly they are the same - box, sockets/plugs, 7202F chip), and already does maf>map conversions for Evo 4-6. He just needs to have VR4 for day or 2 to play with ecu.

And now... blow to this project. Although it seems cheap to acheive (minimum costs of parts required), it is not. Proper tune on rollers and then secondary one road tune will cost you near 500 quid at any reputable tuner (Dynotech, Eurospec, MADevelopments, Indigo GT). So offer of 950 quid for Link4 ecu if does include tune seems like a bargain in real terms.