Fuel Consumption/Efficiency

Andjeti · Post by **Andjeti** » Mon Jul 11, 2011 12:04 pm

I've been testing out my fuel consumption the last few times I've filled up my ET (Stock Except Exhaust), and I've been averaging around 350km per tank. This is probably about a 50/50 Highway Vs. Town driving. I can drive a bit hard at times, but under my "normal" conditions, I estimate my foot rarely goes past half throttle, and I change gears at around 3000 RPM. It does however cruise on the highway (110KM/H) at around 2500rpm in 5th. (Thinking about getting an Auto Diff Gear for it)

Does this sound about right? Or is it time for me to start hunting down more efficiency from the little beast. I've read Evan's comments on Temp sensor to ECU causing over-fuelling when warm. So I'll check that next opportunity I get. But lately, with the damned truck radiators on these things, the gauge doesn't even get above the top of the "C" (unless stuck at lights for extended periods), and I don't even know if my thermo's are working as it never get's hot enough to turn them on. Would this lower than normal operating temp cause the ECU to constantly think the Engine is cold, or will the ECU detect "warm" as anything over say 50 degrees? (I know the gauge may only have a 15-20 degree difference between Cold, and Hot)

Cheers
Jay

sashN12 · Post by **sashN12** » Mon Jul 11, 2011 3:16 pm

I get 4-450 km to a tank of 98, Runnin 13 psi and gets boosted up to speed.

Kimmo · Post by **Kimmo** » Mon Jul 11, 2011 4:22 pm

sashN12 wrote:I get 4-450 km to a tank of 98, Runnin 13 psi and gets boosted up to speed.

Is that with standard ECU though?

ST3LTH · Post by **ST3LTH** » Mon Jul 11, 2011 4:37 pm

Andjeti wrote:I've been averaging around 350km per tank. This is probably about a 50/50 Highway Vs. Town driving.

really? that sounds bad. i was getting well over 500km to a tank in mine (stock).

Kimmo · Post by **Kimmo** » Mon Jul 11, 2011 4:39 pm

I get about 350 but then I give it a fair bit of stick...

Still, I'm sure it's pretty far out of tune : /

TurboZ.Dude · Post by **TurboZ.Dude** » Mon Jul 11, 2011 7:06 pm

Andjeti wrote:But lately, with the damned truck radiators on these things, the gauge doesn't even get above the top of the "C" (unless stuck at lights for extended periods), and I don't even know if my thermo's are working as it never get's hot enough to turn them on.

Well, you've definitely got an issue here; the engine is definitely running cold with that kind of coolant temperatures. A cold engine has bad fuel efficiency obviously.

For me this sounds like your thermostat is stuck open. Besides, even if you have a large radiator, the thermostat should be able to restrict the flow of coolant so that the engine temperature stays at (or close to) correct running temperatures, definitely well beyond what reads as 'c' on the gauge.

I assume the ECU will detect via the temperature sensor that the engine is running cold, but all the ECU can do is to make the mixture richer. I'd be looking at replacing the thermostat first, it's cheap and may solve the problem.

photoglossy · Post by **photoglossy** » Mon Jul 11, 2011 7:09 pm

Being conservative (no boost) i managed 550km on my 40L (or is it 38?) tank in my exa. Stock ECU.

TurboZ.Dude · Post by **TurboZ.Dude** » Mon Jul 11, 2011 7:18 pm

photoglossy wrote:Being conservative (no boost) i managed 550km on my 40L (or is it 38?) tank in my exa. Stock ECU.

Does the EXA have a different fuel tank than the ET? The ET one should be close to 50 liters, 48 or something.

paul w · Post by **paul w** » Tue Jul 12, 2011 11:35 am

Bog stock N12 (E15 motor), auto, hatchback.
I always fill up to the same spot in the fuel pipe. Always. I also always work out the fuel consumption while at the pump, so I can see if it's starting to use more fuel, etc.
On the open road, I average 90-100km/h, using on average 6.5lt/100km (best was 5.8 ).
With a 50 litre tank, that should work out to about 769km.
The average fuel consumption is 7.2, which is about 700km.
I usually fill up about 470km, and it's often about 33 litres, leaving another 17 litres, so I have about 230km left.

sashN12 · Post by **sashN12** » Tue Jul 12, 2011 12:26 pm

Kimmo wrote:
sashN12 wrote:I get 4-450 km to a tank of 98, Runnin 13 psi and gets boosted up to speed.
Is that with standard ECU though?

yeh mate stock ecu, cooler exhaust 13 pound.

Andjeti · Post by **Andjeti** » Tue Jul 12, 2011 1:34 pm

Hrmm, OK, time to hunt it down. I'll check the Thermostat, Temp Sender (to ECU), see if the AFM has been fiddled with (I hope not), etc. Thanks guys.

Cheers
Jay

Damo · Post by **Damo** » Tue Jul 12, 2011 9:31 pm

Check over the water plumbing to the turbo, if it was anything like mine was, it will have the return from the turbo going to the hot side of the radiator rather than the cold side.
Also, replace your thermostat, it may not be seating properly or to cold a setting.

Damo

Andjeti · Post by **Andjeti** » Thu Jul 14, 2011 8:49 am

Thermostat tested OK (Pot of boiling water on the stove, thermometer measuring temps, it opened somewhere between 75-85, so all good). Pretty sure it was seated properly. Temp sender to ECU is working correctly (similar test procedure, but with multi-meter attached). Wires going to ECU are ok (Alas I tested these after I tested the Sender, and the plug no longer has its little metal circlip, so it may not have been connected correctly, but will be now).

TurboZ.Dude - Both my ET's run cold, although Red (Camry radiator) used to run about 1/4 temp, unless in traffic. Blue (Stock ET radiator) has been running just above "C" since it became winter, before that it was below 1/4 temp.

Damo - Return from the turbo does go to the hot side (The same side as thermostat housing, only on the bottom). Is this an issue? Is there a bung hole on the opposite side (I'll look when I am putting my turbo back on this afternoon, wasn't going to pull manifold off, but did, so I need a new gasket)

So I guess that leaves AFM spring tension, this should be fun, shite loads of black silicone around the cap, so it's probably been tampered with at some point. Off to search the forums (If I remember tighter tension=less fuel=possible detonation from too lean a mix)

Damo · Post by **Damo** » Sun Jul 24, 2011 1:15 am

There is most of your problem. If the return from the turbo goes to the hot side of the radiator, it is effectively causing unrestricted flow through the radiator. That is the thermostats job.
Plumb the return into the cold side of the radiator and you will find the engine will warm up in no time, and it will use less fuel. Plus, you will be able to give it a proper tune-up as anything done previously will have been with a cool engine.

There is a steel tube with a barb on it which should run from the return heater hose across the front of the block under the exy manifold. The must be a pic somewhere.

Damo

madn12 · Post by **madn12** » Sun Jul 31, 2011 10:42 am

Andjeti wrote:I've been averaging around 350km per tank. This is probably about a 50/50 Highway Vs. Town driving.

when mine was running (stock, slighly larget exhaust) i would get around the 480 mark on 10psi upwards from that on stock boost

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