iv seen a thread about sum aftermarket ECU and it went on 2 say that sum ECU cure the MAF sensor problm? does it bypass the maf? hows it work? its booked in for a service next friday and need 2 know what 2 get a aftermarket ECU that bypasses the maf or a new maf sensor? any1 please
Billy, IIRC its a LINK Ecu. Tripple X has one in his STI5 - have a chat with him at the next meet and Im sure hell explain all.[]
Indeed i do, the Link ECU completely does away with the MAF sensor, you remove it and blank the hole, and instead the ecu looks at other factors to calculate the amount of air entering the engine. [8D] Andrew C will tell us more on this im sure! One thing to think about here though is that a new MAF costs what? £70-£80 A new Link ECU (with knock and lambda link) from BRDevelopments mapped by Bob Rawle costs somewhere in the region of £1400. You could always try and get the lot second hand like i did and then get Bob or Andrew C to do the map.
Several aftermarket ECUs can run without a MAF, Link/GEMS/Motec/Pectel to put them in price order. As TripleX says, both he and I run a Link, the inlet airflow actually passes through the maf housing, you can either leave it in place and the ECU just ignores it or remove it and replace with a piece of better flowing pipework. Without a MAF, ECUs use the speed-density principle, for a given VE/RPM/MAP there will be a specific airflow mass passing through the engine and the ECU can calculate fuelling based on this. Andrew...
scoobbillydoo I thought you had a MY97? Phase 1 cars use a hot wire MAF which is far less susceptible to damage than the hot film type that so much has been posted about on SNet. They can also been cleaned, although usually do a pretty good job of self cleaning. If yours is a UK car I can lend you a good MAF to try. Andrew...
Andrew, what do you mean when you say VE? Also how do the MAP sensors work, ive heard of people changing to bigger MAP sensors, what would be the reason for this?
Volumetric Efficiency, its a measure of how well a engine processes the Air Fuel mixture which passes through it. It changes with RPM due mainly to cam and valve design but there are a myriad of other factors. On a Subaru Max VE is around 4500RPM for UK/WRXs and a bit higher for STis which is where maximum torque will be produced. MAP sensor is just a pressure transducer, on pre-97 cars the maximum reading is 2.5Bar absolute (1.5bar boost) although this is in reality only about 1.2bar as the output is non linear above this. On later cars a 3bar absolute sensor is used which is linear to about 1.8bar boost, which is calibrated to a 1.55 bar limit on the Link. For the Link there is an option to use an alternative 3bar map sensor made by GM which is linear to 3bar (ie 2bar boost). Andrew...
Second guessing your next question, all post 97 Links have Inlet Air Temp (IAT) compensation, although only STis have the sensor in place as std. Andrew...
ohhhh god im lost now[:I] ok its a uk MY97 tell me what im best doing new ECU or use a hot wire MAF which is far less susceptible to damage than the hot film type i trust u will know more than me[] thanks for the reply billy[]
Your car already has a hot wire MAF, they can fail, but not with the regularity of the later hot film types. What makes you think you need it replacing? I wouldn change the ECU unless you are considering seriously modifying the car - look how far Rich has got with his 97 on the OEM ECU. Andrew...
Andrew, excuse my ignorance, but I am keen to learn, Absolute pressure = Atmo + manifold pressure? if that is correct, surely pressure & density of air are not comparable?
no i didnt want 2 go down the root ov changing the ecu just yet but i just read a thread on a ecu that can bypass the MAF so i thought instead ov getting a new MAF sensor every 2 years or so i thought id get rid ov it iv got a strong feeling that the maf is on its way out it started about 4 months ago, when i start the car up it revs hight at 1500 revs till warm or a short drive then the car run fine. as the weeks and months went by it got worse it and then it started pulling back when over 3000 revs or so but after a 1 mile drive it was ok it just gets worse now its about a 2 mile drive b4 it runs fine but as i was cumming back from mi mums at the weekend it holds back all the time. it doesnt pull back big time but u can feel it just slightly holding back it still flys like a rocket but its just holding back a bit
Andy: Manifold Absolute Pressure is absolute pressure, atmospheric pressure doesn really come into it. I can remember my A level physics that well but I seem to remember that for any given gas, density is a function of pressure and temperature - the term vapour pressure keeps jumping into my head but I can remember its relevance. Billy: What you describe could be a number of things, MAF, Lamdba, bad earth, plugs, plug leads, ecu pulling timing due to noise caused by lean running if using an induction kit, etc, etc, etc. As I said I have a MAF which was working perfectly before I removed it, you can borrow it if you like. Andrew...
What you see on a boost gauge is what is (if reading BAR) BarG (G being gauge), absolute pressure is that reading plus atmospheric pressure, which is usually around 1Bar constant (give or take a bit for dodgy weather). This is called BarA. In the normal world because atmospheric pressure is constant we use BarG, but for an ECU it needs to run on Absolute to correct for the change in atmospheric pressure for instances like driving at high altitude, say Mexico City, this enables a manufacture to produce one ECU for the whole world, with only variance being need for fuel quality available (eg 100ron in Japan) Jim (and yes I did physics, but pressurised system is what pays the bills)
