What do you do for a living Nodge?
What do you do for a living Nodge?
Nodge68
Well-Known Member
Retired from automotive engineering.
What sort of lawnmower engines did you work on?
Nodge68
Well-Known Member
Lawnmowers were a bit low tech for me, but I would be able to make them faster
. I used to build performance vehicles for various client's. Mostly wolf's in sheep's clothing type stuff. Triumph straight six's were my favourite creations. Here's one I did in 2003.
GrumpyGel
Well-Known Member
Lets cut the rubbish out here.
The driver tells the ECU how much fuel he wants to use. The MAF, combine with other sensors such as MAP, IAT and engine speed, tells the ECU how much is allowable to be injected.
The ECU will override the drivers wish with the values from the sensors - so the sensors, including MAF, are controlling the amount of fuel injected.
To see how much difference the MAF can make, this is a map from the EDC15 used in a 1.9 VAG engine. The EDC15 is used on Freelander TD4 but I haven't come across a mapping for that. The TD4 being slightly larger, probably using a different turbo charger, tuned at factory for different power requirement and of course simply being a different engine will have different values, but it gives an idea. It shows that as revs rise above idle, full boost detected by the MAF will allow roughly 50% more fuel into the cylinders (effectively turning the 2.0L into a 3.0L in "swept volume" terms discussed previously)
As said above, it will also be applying other limits. It will also be governing the EGR to allow these limits. Interestingly, and I forget where I got this info, the EDC15 does not use oxygen sensors in the exhaust, therefore it can not check that the sensors it is using are working within their original tolerances - therefore when MAFs go wrong (as the Bosch unit in TD4 does regularly!) you get black smoke (because its allowing to much fuel into the engine) rather than a MIL light lit!
The driver tells the ECU how much fuel he wants to use. The MAF, combine with other sensors such as MAP, IAT and engine speed, tells the ECU how much is allowable to be injected.
The ECU will override the drivers wish with the values from the sensors - so the sensors, including MAF, are controlling the amount of fuel injected.
To see how much difference the MAF can make, this is a map from the EDC15 used in a 1.9 VAG engine. The EDC15 is used on Freelander TD4 but I haven't come across a mapping for that. The TD4 being slightly larger, probably using a different turbo charger, tuned at factory for different power requirement and of course simply being a different engine will have different values, but it gives an idea. It shows that as revs rise above idle, full boost detected by the MAF will allow roughly 50% more fuel into the cylinders (effectively turning the 2.0L into a 3.0L in "swept volume" terms discussed previously)
As said above, it will also be applying other limits. It will also be governing the EGR to allow these limits. Interestingly, and I forget where I got this info, the EDC15 does not use oxygen sensors in the exhaust, therefore it can not check that the sensors it is using are working within their original tolerances - therefore when MAFs go wrong (as the Bosch unit in TD4 does regularly!) you get black smoke (because its allowing to much fuel into the engine) rather than a MIL light lit!
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I think the moderators should confine crusaders to a restricted thread category - can you image Wammers versus Joe on how overfueling a VCU causes high blood pressure on the nut on the end of the steering column if a 50mm lift is retrofitted to a dodgy MAF.
I'll get me coat
I'll get me coat
Lawnmowers were a bit low tech for me, but I would be able to make them faster
Here's one I did in 2003.
View attachment 109377
Indeed pretty simple motor. When the 2.5 Pi came out they used to wear away the tag for the thrust bearing. Official factory cure was to drill an hole in the web and fit a self tapper. Some of the Stags and Dolomite sprints where abortions. Rover stuff P6 and 2000 were pretty good motors. British Leyland has a lot to answer for. The Marina, Allegro and Maxi were total crap. When you did a PDI on a four door Marina. You could almost guarantee the N/S rear door would not open. .
GrumpyGel
Well-Known Member
It does nothing of the sort Wammers. That mapping is titled "Smoke map IQ limit by MAF".It shows that as revs rise above idle, full boost detected by the MAP will allow roughly 50% more fuel into the cylinders (effectively turning the 2.0L into a 3.0L in "swept volume" terms discussed previously)
Fixed that for you.
I don't pretend to know exactly how the MAF is used in the fuel calculation, just going by the information available whether the MAF is used in calculating the amount of fuel to be injected. I have 1 voice saying it is not and all other references I see say it is. If you can show us somewhere that says it isn't, then maybe you won't be the lone voice.
I can think of a few reasons why it could/should be used.
The MAP sensor. "MANIFOLD ABSOLUTE PRESSURE" sensor. Measures the turbo boost for fuelling. Little to do with MAF, although it,s flow reading maybe used by the ECU as cross reference, to ensure the MAP reading is sensible before injecting fuel to achieve a driver throttle power demand. The interlinking of the circuits and sensors on the later Emissions control systems is such that a glitch will cause some very strange behaviour. .
You are being confused by the ECU fuel MAPS and the MAP sensor. I really do know what i am talking about honest.
Tony Reeves
Well-Known Member
Older engines will use either Mass Air Flow (MAF) or MAP sensors to determine fueling (amongst other things). These days it is common to use both as MAP works better at low manifold pressures (less air flow) and MAF for higher air flows, at least in throttle controlled engines.
And speaking of throttle control, it has been quite common for diesels. The venable Fordson Tractors and Thames Trader trucks used Simms mechanical injector pumps. These used Manifold Air Pressure to determine fuel metering with the accelerator pedal connected to a throttle in the intake manifold.
freelance
Well-Known Member
Great fun if you derestricted the airflow, gave much more power and speed !!
GrumpyGel
Well-Known Member
I'm sure you basically know what you're talking about Wammers.
I'm also sure I know enough to know the difference between MAF sensor, MAP sensor and Fuel Maps.
I'm also sure that others are not as thick as you make them out to be.
One last thing I'm sure on.... is that you are wrong and that you know it - sorry that's 2 things.
Diesel Do
Well-Known Member
We don't delete the MAF via the file service, the MAF is very important. Here's a quick explanation of why MAF delete is bad:
- MAF - Fuel economy: The MAF has both an air mass meter and an intake temperature sensor. The ECU makes small injection timing corrections based on the intake air temperature and the air mass flow. These result in both better fuel economy and also a smoother sounding engine.
- MAF - AFR calculation and smoke limitation: The main job of the MAF is to monitor how much air is available to enable the ECU to precisely control the fuel quantity injected in to the engine. If a MAF is deleted, we need to set some default high values so that power is not limited. This results in lots of smoke under full load as the car no longer controls Air Fuel Ratio (AFR), once the turbo spools up then there will be sufficient air and the car will run cleanly.
Off a reputable tuners website
- MAF - Fuel economy: The MAF has both an air mass meter and an intake temperature sensor. The ECU makes small injection timing corrections based on the intake air temperature and the air mass flow. These result in both better fuel economy and also a smoother sounding engine.
- MAF - AFR calculation and smoke limitation: The main job of the MAF is to monitor how much air is available to enable the ECU to precisely control the fuel quantity injected in to the engine. If a MAF is deleted, we need to set some default high values so that power is not limited. This results in lots of smoke under full load as the car no longer controls Air Fuel Ratio (AFR), once the turbo spools up then there will be sufficient air and the car will run cleanly.
Off a reputable tuners website
