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The mkiv Supra Owners Club

Really poor fuel consumption


GeordieSteve

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Ello!

 

The sup used to cost about £10 a week to get to work and back... BARGAIN! It's only a 8 mile round trip per day so it wasn't too bad. Now since the winter rebuild things have had a turn for the worst... down to £10 per day (and thats for 8 miles round trip!!!!). I don't drive fast at all especially on the way to work. Maybe 1/3 of the way at 50mph, the rest at 30mph.

 

Current spec:

 

Veilside exhaust

Double de-cat

Walbro

440 injectors (replaced in 2 weeks)

Envy hybrids

Apexi power intake

Blitz boost controller (1.23 bar MAX when I boot it)

TRL FCD

Greddy FMIC

Apexi S-AFC (not set up yet... again 2 weeks)

... not much else that would effect fueling

 

Does this sound normal (I effin hope not!!!)? Any ideas?

 

Taa muchly :thumbs:

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how many litres is £10?

 

cause with £ you cant work out JACK.

 

work out the litres

take the amount of miles youre travelling between fill-ups

 

and work out the miles per gallon

 

I drive exclusively in london (stop and go) and get 19-21 mpg depending on what fuel (optimax, Tesco, etc)

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well. 8 miles round trip....so thats 4 miles each way

 

fuel required to warm up the engine every 4 miles...i am not surprised.....

 

 

EDIT: actually forget what I said....youre talking about a winter rebuild.....so I DUNNO...

 

 

maybe o2 sensor....reminds me...i need to get mine checked :D

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my mpg is all over the place too mate! local optimax here is 90.9. got 180miles out of the top half of the tank the other day which i was quite happy with :D week before i got 100 and that was with slower and steadier driving!!

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In my experience, ECUs don't always pick up a 'lazy' or half-dead oxygen sensor. They keep trusting it, and the lower voltage is treated as gospel, resulting into continous overfuelling (the sooty plugs will show if that is happening)

Only if the sensor is totally dead or shorted out does the ECU see it as faulty, it cannot tell in between, if it still returns some voltage (but not the proper one)

Say if the ECU wants to see 0.55V for "X" amount of injector duty at (closed loop) idle, the tired sensor will only send 0.3 V, so the ECU will think that it's lean, so it will increase the flow on the injectors until it sees 0.55V.

By the time the sensor sends 0.55V the car is running pig-rich, but the ECU is happy because it eventually did manage to operate closed-loop at 0.55V so it doesn't know any better ;)

 

Translation: I'd first fit a new sensor mate :cool:

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just turn the safc off or zero all the (fuel adj) settings. what vehicle did the safc come off, one with bigger injectors?

 

i'd doubt yr o2 sensor would suddenly go to this extent especially after you have just installed new injectors and an unknown setting safc. these would definately be my first culprits to rule out. o2 sensors genarally deteriorate slowly. im not saying it's not the o2 sensor, but by no means the first, cheapest or simplest thing to check.

 

whay have you put new injectors in? did you have them flow tested?

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First thing I do with SAFC is disconnect the damned thing, I get loads of trouble with them. If you think a SAFC will manage bigger injectors properly, in the future, think again!

They have NOTHING LIKE the resolution to do this. Bigger injectors should ONLY be used with a proper standalone mappable ECU, like an AEM, Motec or whatever.

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...i'd doubt yr o2 sensor would suddenly go to this extent especially after you have just installed new injectors and an unknown setting safc. these would definately be my first culprits to rule out. o2 sensors genarally deteriorate slowly....whay have you put new injectors in? did you have them flow tested?

eyefi is right, sensors usually deteriorate slowly (although I did have one dying suddenly, even though it was 2 months old!)

I didn't know about all the other fuelling changes that had happened just before, I'd definately rule those out first

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You mapped mine OK :p

 

That was 550cc injectors though, on hybrids. I also wouldn't like to go higher than that with an AFC and defo not do a single conversion with one. I think E-Manages have the resolution though, but Chris doesn't :)

 

One sunny day Terry and I will pop over to CWs and let him have a look at our non-Motec solutions :D

 

-Ian

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Still running 440's at the mo. The S-AFC came off a supra... I think with 550's. My 650's get put in on the 23rd and I'm going to have the S-AFC set up then.

 

I did have an emanage to do the work but was told it almost impossible to set up and S-AFC was the easier option

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Still running 440's at the mo. The S-AFC came off a supra... I think with 550's. My 650's get put in on the 23rd and I'm going to have the S-AFC set up then.

 

I did have an emanage to do the work but was told it almost impossible to set up and S-AFC was the easier option

 

If you've taken an AFC off another car and not zero'd it you are opening yourself up to a world of problems, that's craziness. Running an AFC on a car with stock injectors is futile as well, they are for trimming bigger injectors down, they cannot magic up more fuel out of smaller ones (well, not where it counts anyway). I'm of the belief that if you have to increase the airflow signal at any point, you haven't got big enough injectors, full stop. Having the AFC pre-installed ready for a future upgrade is OK though, of course, as long as it's zero'd!

 

Controlling 650's with the AFC should be... interesting :)

 

Who told you an E-Manage was impossible to set up? :banghead:

 

-Ian

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