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Crap Fuel Economey...

justin911

By justin911,
in General Maintenance

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Cubes Grand Master

Cubes

Posted
Posted (edited)

If an injector is blocked or clagged sure less fuel will pass through, that fuel will also squirt instead of spraying a fine atomized mist.

Bad atomization = incomplete combustion = bad fuel economy.

If it starts fine then it sounds as if the injectors are ok. :blink:

Cold start water temp correction table also has some head room for fuel economy improvements.

The R34 values are a very good place to start from.

Depending on how much you are paying for the tune they will have the car for a day or two tweaking the water temp correction and a few other little bits.

Edited by Cubes
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benl1981 Grand Master

benl1981

Posted
Posted

But doesn't it get into closed loop within about 2 -3 minutes anyway so closed loop running when reasonably cold will be the same?

I think I am only going to get a tune for 2-3 hours. Cold start correction the tuner may go off other R33s he's done I'm guessing. I'm going to the guy that tunes Sydneykids cars - the tuner seems pretty knowledgeable.

Are you talking about R34 Powerfc setings?

Cheers.

Cubes Grand Master

Cubes

Posted
Posted (edited)

Water temp injection correction has nothing to do with closed loop.

It richens up the afr when the car is first started, much like a choke.

As water temp increases the afr leans off to the usual afr.

The R34 water temp correction runs a little leaner and actually allows the car to run better when cold. Well, my car anyway.

You can throw it in your self to have a look see once its all tuned, don't forget to write down the origional values.

The R32/R33's origional water temp injection correction values are:

+80C 1.000 1.000

+50C 1.094 1.156

+30C 1.141 1.297

+10C 1.250 1.500

-10C 1.391 1.734

-30C 1.594 2.000

The R34's water temp injection correction values are:

+80C 1.000 1.000

+50C 1.031 1.078

+30C 1.063 1.219

+10C 1.250 1.469

-10C 1.391 1.734

-30C 1.594 2.000

Table reads as

temp, light load injection correction and moderate/heavy load injection correction.

As you can see the R34 runs slightly leaner. Mine used to really stink of fuel on the mornings, it doesn't tend to stink as much any more, also there is no slight flat spot that I previously had and the car simply drives easier when stone cold, that is starting and instantly driving away.

Have a good look around your pfc h/c, make yourself familiar with all the menu's and options. Do this now, before its tuned. So if you break something you can simply initialise the pfc and its all good again. :blink:

Edited by Cubes
benl1981 Grand Master

benl1981

Posted
Posted

So what the engine doesn't run in closed loop till it gets to around 80deg C? I guess it must be about 5 mins or so till it goes to closed loop then. Have to have a check in the morning. I'll look at the 02 sensor readout

I have noticed a smell of fuel in the morning. I have looked at the table in the PFC hcontroller and thought the values were high. Thanks for the numbers :blink:

I guess the stock R33 ecu water temp correction values would be similar to the PFC R33 ones?

Thanks Cubes :)

Cubes Grand Master

Cubes

Posted
Posted

No idea what the stock values are.

Those values are from the PFC.

R32 and R33 values are the same.

R34 runs a little leaner.

My R32 gets up to operating temp within 2km's, earlier if I let it idle for a minute or so after the initial start.

I'm running the R34 values, they are perfect, it drives nicer than the origional rb20/25 values. So.. I'm not going to fiddle.

I did try fiddling with the rb20 values, I got flat spots and general bogging. i.e driveability suffered.

benl1981 Grand Master

benl1981

Posted
Posted

Hey Cubes put the numbers in today. I found that my car goes into closed loop within about 2 minutes anyway - so these corrections are only for when you are in open loop and before car gets to closed loop.

I get up to about 70 deg C within 3-4 mins of driving. ABout 5 mins before it reaches 80deg C

Cubes Grand Master

Cubes

Posted
Posted

Yes thats correct, mine gets to operating temp just as quick, you will find without as much injector correction the car will jump in to closed loop ever so slightly earlier than with a lot of inj. correction. :(

Every little bit counts.

How did you find drivability? Do you simply start and drive or let it idle for a min or two?

Cubes Grand Master

Cubes

Posted
Posted (edited)

Yes thats correct, mine gets to operating temp just as quick, you will find without as much injector correction the car will jump in to closed loop ever so slightly earlier than with a lot of inj. correction. :(

Every little bit counts.

Do you simply start and drive or let it idle for a min or two?

How did you find drivability?

After I fitted the Z32 I found the car felt a little dead, it appears the z32 ever so slightly richens everything up. Using this table in mine has made it much better, no more dead feeling.

Edited by Cubes
Cubes Grand Master

Cubes

Posted
Posted

You can tune it so that when it drops out of closed loop you run 11-12:1 afr's in order to pick up some off boost torque.

Tune it to 14.7:1 off boost if you are after economy.

You can go furthur and tune up to ~2psi with an afr of 14:1, helps a little with economy. It really depends on the turbo setup and how quickly it boosts, if it boosts quickly you may see an improvement in economy by tuning as such, if it doesn't make that 2psi until 3500rpm with 1/2 throttle then its pointless. :(

benl1981 Grand Master

benl1981

Posted
Posted (edited)

Hey cubes if it is off boost then shouldn't it be at 14.7:1 anyway

"Tune it to 14.7:1 off boost if you are after economy."

Another thing. My stone cold idle is fine - but I find that after a day at work I come back and water temp is 25 deg C and the idle hunts for about the first 20 seconds... Wierd. It did it with the R33 PFC values and the R34 ones. On stock ECU it didnt

Edited by benl1981
Cubes Grand Master

Cubes

Posted
Posted (edited)

Why would it be 14.7:1 off boost anyway?

When you drop out of closed loop mode due to pushing your foot on the accelerator too hard the afr will drop to anywhere from 13:1 to 12:1, then you push on the accelerator a little harder again and it comes on to boost, the afr's then drop to 11.5 or 12:1.

I'm not interestered in the pfc's common idle hunt issues, I'm more so interested in the transition from off to on throttle at low rpm, i.e decelerating in to a corner off the throttle then rolling back on the throttle at low rpm.

With the R32/R33 values I found mine bogged at low rpm a little.

I've always had the odd idle hunt, with the stock ecu and the pfc, the pfc for myself provides a much more stable idle.

However, It didn't until I adjusted the idle screw to the rpm idle set in the pfc. Then did an init and idle learn for the next 30mins.

I've just clocked 246km's to half a tank of juice, this bigger turbo is helping the 3ltr keep off boost and suck less juice at light throttle. :D

I had a good look at the exhaust today, usually I would see a small stream of black fuel smoke trailing from the exhaust on a cold start, I now see nothing. Apart from a bit of water due to condensation. :D

Edited by Cubes
benl1981 Grand Master

benl1981

Posted
Posted

I just find that mine stays in closed loop till a bit of boost is developed. Maybe if you hit half throttle or so at 2000rpm it will go to open loop without any boost present.

It idles quite erratically - might see what the tuner thinks..maybe it needs a little cold start enrichment (Is this seperate to inj correction)

Just a question - It says 15deg timing on PFC. ..The PFC doent know what you have it adjusted to on the CAS does it..or has it made corrections for the CAS position. I have about 17-18BTDC on the CAS (according to timing light)..Even though it says 15deg on powerfc do I actually have 17 ??

Thanks

Cubes Grand Master

Cubes

Posted
Posted (edited)

Is yours a 2ltr or 2.5ltr?

I find with the the 3ltr it drops out of closed loop really easy, with the lightest of throttle, stabbing the throttle has it instantly dropping to load points 15-16 with no boost from as low as 1200rpm. :D

---

The PFC assumes you have matched the timing to the value in the pfc.

Edited by Cubes

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