Convert Boost Gauge to MPG gauge???
08-12-2005, 03:26 PM
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Convert Boost Gauge to MPG gauge???
Alright here's the deal....
I have a 86' 944 turbo with a boost guage below the tachometer....
i want to know if i convert teh boost gauge into a MPG gauge... so i can get the glow face gauge and add a seperate boost gauge???
Possible???? or not???
I have a 86' 944 turbo with a boost guage below the tachometer....
i want to know if i convert teh boost gauge into a MPG gauge... so i can get the glow face gauge and add a seperate boost gauge???
Possible???? or not???
08-12-2005, 06:20 PM
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I'm guessing you're talking about a MPG gauge similar to the ones in the e36 m3? It could probably be done.. but if having the old boost gauge there bothers you that bad while having an aftermarket gauge, an NA gauge cluster may be easier. I have no idea if they are swappable though.
08-12-2005, 07:10 PM
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I think only the 86 NA had the mpg gauge. My 86 did and my 87 did not.
But I am pretty sure you can swap them out. Or just get 86 NA gauge covers and move on.
But I am pretty sure you can swap them out. Or just get 86 NA gauge covers and move on.
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08-13-2005, 01:44 AM
#11
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it pretty much the same thing the e30's also have the MPG gauge on them. the only thing that you have to prob change is the label. but am not sure i think its the same comcept.
08-13-2005, 06:29 AM
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I did this on my 944S
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You can dismantle the cluster and just swap the rev counter unit complete. The 'econometer' part connects direct in to the printer wiring board.
On the Lux/S/S2 the DME has the correct signal already routed to the terminals. The Turbo probably does not have a suitable signal available from the DME.
The existing KLR signal would probably drive it, but the calibrations would be about as truthful as our prime minister, Tony Blair
Rick
Original
After
You can dismantle the cluster and just swap the rev counter unit complete. The 'econometer' part connects direct in to the printer wiring board.
On the Lux/S/S2 the DME has the correct signal already routed to the terminals. The Turbo probably does not have a suitable signal available from the DME.
The existing KLR signal would probably drive it, but the calibrations would be about as truthful as our prime minister, Tony Blair
Rick
08-13-2005, 03:43 PM
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Originally Posted by Speed Demon
Jason!!!
is this true about relabling????
Could i get someone to verify that....
what if i increase boost???
is this true about relabling????
Could i get someone to verify that....
what if i increase boost???
There are some who will claim that the mpg guage is vacuum-based like the guage in older BMW's is, but they're incorrect. The 944/924S guage is electronic, using a speed input from a hall-effect sensor in the speedometer (for the 924S and early 944) or intercepting the speed pulses from the speedometer input sensor (late 944) and combining the speed value with the injector duty cycle value from the DME. From the duty cycle on the injectors it can calculate the fuel delivery rate and with the fuel delivery rate and the speed it can calculate mpg, which it then displays via the electrically-driven analogue guage.
Aaron
08-13-2005, 04:05 PM
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Exactly - it's not so simple. Obviously the engine turning 4,000 RPM in second gear and fourth gear are going to consume the same amount of fuel (same rate), but yield very different mileage results - you're going to cover more ground in fourth.
Incidentally the MPG gauge on the n/a cars (at least on my early n/a) is INTENDED to be both a fuel rate gauge and an MPG gauge (it has both scales), although this is obviously ridiculous - for example, you can't be doing "60mpg" when your speed is zero - your miles per gallon is also zero, since you're not moving. I think therefore that the rightmost "peg" is actually zero, but has a limit approaching that of infinity from the left (anybody that's taken calculus will understand what I'm talking about)
IIRC the "0.5 g/h" indication corresponds to roughly the "30mpg" position, which only going to be true in one gear (probably fifth, although I've not calculated it out). I think you could fairly easily (and accurately) convert the stock boost gauge on the turbo to a fuel FLOW gauge, but not an MPG gauge - there's no way for it to compensate for vehicle speed, which obviously impacts this value quite dramatically.
Incidentally the MPG gauge on the n/a cars (at least on my early n/a) is INTENDED to be both a fuel rate gauge and an MPG gauge (it has both scales), although this is obviously ridiculous - for example, you can't be doing "60mpg" when your speed is zero - your miles per gallon is also zero, since you're not moving. I think therefore that the rightmost "peg" is actually zero, but has a limit approaching that of infinity from the left (anybody that's taken calculus will understand what I'm talking about)
IIRC the "0.5 g/h" indication corresponds to roughly the "30mpg" position, which only going to be true in one gear (probably fifth, although I've not calculated it out). I think you could fairly easily (and accurately) convert the stock boost gauge on the turbo to a fuel FLOW gauge, but not an MPG gauge - there's no way for it to compensate for vehicle speed, which obviously impacts this value quite dramatically.