MAF remapping (not sure on this.)

[jareeb]

My truck isn't turbod its naturally aspirated. The fuel system isnt maxed out. The turner I have now apexi safc 1 works but not how the new version works. Okay? The apexi I have uses rpms to change from pot to pot and I want to make one to use the tps that's it

 

[tcmtech]

No its called a Turbo. I would still like to get 25mpg

Well you are the one who mentioned the turbo.

 

[jareeb]

Cuz someone said put a gas thirsty v8 in it lol

 

[3v0]

My wife's 4.6L V8 95 Lincoln town car get 24mpg on the road with no mods.

 

[tcmtech]

My wife's 4.6L V8 95 Lincoln town car get 24mpg on the road with no mods.

My wife has my old 94 Mercury Grand Marquis with the 4.6 V8 that I stripped as much of the emissions systems out of as possible and that runs low 20's in town and upper 20's to low 30's on the interstate at 75 MPH or better.

I have often thought that with non emissions cams and a off road non emissions program on the ECU it could probably get another 5+ MPG over its present numbers.

As far as fuel efficency is concerned large displacement slow turning engines without emissions systems are the way to go not small high speed ones.

 

[jareeb]

Yeah. Umm but I think me being a male driver I would have a very hard time keeping my foot out if it haha

 

[tcmtech]

Thats the average mileage I got when I drove it daily and I never babied it and the wife drives even worse than me now and its still running the same average numbers.

In fact I regularly pulled a trailer with it when it was my daily driver often with loads up to around 5000 pounds and it still ran upper teens and low 20's on the highway with power to spare.

Small engines may pack more power in a given displacement volume but that does not mean they are more fuel efficient.

 

[jareeb]

okay v8 is not the answer im looking for. i spent too much money on the cam and all the shenanigans that goes along with it to just throw it away for a v8. so im not sure how i can explain what im trying to do any better then i have already, sorry im not good at explaining things over text, prolly cuz i cant spell the words i think of lol.

hmmm
okay lets start at the maf, the maf sends a current to the lm3914, the maf current needs to be change to a different pot when the tps voltage changes as it increases when you open up the throttle up, then the maf current needs to come though the pot and go back to the maf wire that goes to the engine's ecu.

im not sure if this is showing it or not because im not sure that the triangles that go down to nothing mean like after they go through the gate
**broken link removed**

 

[alec_t]

The triangles are symbols representing ground (battery negative).
As the tps voltage rises (pin5 of LM3914), pins 1,18,17,16 of the LM3914 draw current in turn. Because of resistors R3-R6 this results in the voltages at the inputs of inverters U6-U9 being pulled low in turn. The inverter outputs go high in turn, thus enabling transmission gates (switches) U6a-U6d in turn to pass the MAF signal at the Y inputs of the gates to the Z outputs of the gates. Pots U2-U5 thus receive the MAF signal in turn. Their wiper voltages would need to be summed (summing arrangement not shown) to give your re-mapped MAF signal.
If the LM3914 operates in bar mode (as here), 'in turn' means its output pins draw current in the sequence 1, 1+18, 1+18+17, 1+18+17+16. I think that's the sort of thing you wanted? If it were reconfigured to operate in dot mode the sequence would be 1,18,17,16.

the maf sends a current to the lm3914

Not in my circuit!

the maf current needs to be change to a different pot when the tps voltage changes

Do you really mean current? If the MAF sensor (I'm unfamiliar with those) is a current source rather than a voltage source as I've assumed then my circuit would need modifying.

 

[jareeb]

Maf sends voltage also I would need it in dots not bar mode

 

[alec_t]

I would need it in dots not bar mode

In that case leave pin 9 of the LM3914 open circuit.

 

[tcmtech]

okay v8 is not the answer im looking for. i spent too much money on the cam and all the shenanigans that goes along with it to just throw it away for a v8.

You sound just like a good friend of mine. He didn't do his research before hand and spent around $5000 rebuilding the Chrysler slant six for his pickup just to end up with a very expensive and still horribly underpowered engine.

My dad shelled out the engine is his pickup about the same time so I gave him my old 5.8 V8 that was terrible on fuel and low on power and built myself a full heavy duty highly efficient 460 cu V8 that pushes 500+ Ft/lb torque and 400 Hp on propane while getting in the mid teens, when driven conservatively, and added a custom built E4OD transmission with its own independent control unit for the same $5000 price.

In return I got a much envy opposed to much laughter for my investment as well.

(Then a little old lady took the front end off the pickup one day while I was in town.)

 

[Jaguarjoe]

The TPS will not be 0-5v, it will be more like ~0.25 to ~0.8v because most ECU's like a live zero and the TB won't rotate 90 degrees, it's more like 85 to 86.
Running this circuit directly from the vehicle's 12v system is suicidal. There is so much noise and transients it would be bad for any IC. Use an LM2937/40 as a hardened regulator to feed the circuit. Pick a voltage less than 12 and more than 5, 9 works well. These are cheap, rugged, and plentiful.
If you're only using 4 or 5 inputs on the 3914, you could make your own comparitor with adjustable trip points.
A small microprocessor would do this with minimal external parts and expense.

What does pot U1 do?

 

[alec_t]

Taking on board Jaguarjoe's comments I agree the circuit I posted would be better supplied from a regulated 9V. Also, some conditioning of the TPS signal would be advisable. Indeed, the circuit proposed is merely an attempt to set out the scheme I think the OP was initially proposing. It's not the way I would do re-mapping in practice and yes, a small micro would be preferable (as I think was mentioned earlier).

What does pot U1 do?

It provides a proportion of the MAF signal when the TPS signal is below the first threshold voltage of the LM3914.