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Accuracy of MFA mpg reading

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Might be a stupid question this:-

 

Anybody know if the mpg MFA reading is an accurate one or just a ball park figure? How does it calculate it?

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It seems fairly accurate to me, best thing to do is calculate it yourself manually then compare the figures.

 

also I tested the speedo in my mums golf last nite with sat nav, when she was doing 75 according to the car, the satnav read 70mph, I will do the Corrado as well when I get chance.

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the mpg is a calculation and id expect that more or less any mode would put it out as the calcuation is based on the standard parameters of the car

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It seems fairly accurate to me, best thing to do is calculate it yourself manually then compare the figures.

 

also I tested the speedo in my mums golf last nite with sat nav, when she was doing 75 according to the car, the satnav read 70mph, I will do the Corrado as well when I get chance.

 

I've done that in my corrado. I was curious since I have 17" wheels on it. Alot of other guys had tried it with their corrados with statndard wheels. They were getting up to 8 mph under from the sat nav (real speed) than from the car's speedo. My speedo reads ~1.5 mph over the speed I am really doing. No matter what speed I do. I tested at 30, 50,60,70 & some others :roll:

 

I think its a really handy thing to know especially when going through towns. I never speed through towns and I know sitting at 30 on my speedo, I ain't speeding. However, if I was to be a bit cheeky I could sit just a shade under 35 on the speedo due to the 10% error given by the police and the 1.5mph error in my speedo :lol: But I dont do that!

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the mpg was spot on when i tested it...

 

my speedo is 10% out though!!! indicating 100mph and actually doing 89mph

 

 

you're a very naughty boy!! You'll be running standard wheels though??

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How does it calculate it?

 

I think there's a manifold pressure sensor in the instrument cluster - that gives the MFA a clue as to how much fuel is going in to the engine, and of course it knows how far you've travelled... one divided by the other gives you your mpg...

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The reading of MFA Fuel is done by vaccum!

There is a hose that comes out of the back of the speedometer and goes to the engine bay.

If you have a vaccum leak (pherhaps a broken pipe) you would get faulty readings!

Lately i have been setting up the ignition timing of my 1990 G60 to the maximum time before i feel knocking / pinging. I saw that the value of vaccum (showed in the MFA 2 in the hidden mode) decreased to about 74! Which should be normal to get values between 84 - 104 readings. Could this be a problem? Before this a was having 88 readings!

I still noticed that now the fuel reading is not the same! It shows less fuel expense! And i don´t believe in that!

So i wonder... How efficient could the MFA readings be?

Curiosity, i advanced a lot my ignition timing because with standart timing 6deg +/- 1 the car was slow as hell! And now it´s quicker of the line! You can notice the difference! Now the muffler is not poping any more! And now the motor looks like a swiss clock! I am using 95 RON from Shell.

Is something rong with i have done? If so... Advice me!

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