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Old 09-11-2008, 06:49 PM   #1 (permalink)
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newb Q'n. Lean burn + advanced timing ... how far to go?

I have a 93 Toyota Pickup 4x4. Currently I average 18.4 mpgs. It's a 5spd, manual locking hubs, 3.0 Liter V6. Unladen weight w/ me in the driver seat is 4060 lbs.

I have taken care of a bad EGR valve and installed a new magnaflow catalytic converter. 100% synthetic amsoil, front to rear. K&N air filter. All non-essential vacuum operated devices are gone. No AC (totally removed to the back of the dash).

I have a JAW (just another wideband) kit from New Page 1. I'll be monitoring my AFR, EGT's and I may install a MAP sensor so I can monitor that. It can also log RPM & TPS. However, AFR is logged all the time and then there are only 3 optional inputs to choose from. Must choose wisely.

I have looked at the MPGuino and I can probably put it together & use that for data logging as well.

My plan is to lean out the engine. The factory O2 sensor is still installed, that way the ECU does not go into open loop mode. The WBO2 sensor is installed 10" downstream in the cat.

In addition to leaning out the engine, I'd like to advance the timing. Most guys for this toyota that advance timing run it to 15 +-2. Base timing is 10 deg BTDC.

This engine family is prone to a burn #6 exhaust valve, so I'll be installing my EGT thermocouple as close as I can. It happens to be where the exhaust manifolds merge, right next to the #6 cylinder.

Any ideas what an ideal EGT would be? How hot can it get before I have to worry about the valve burning?

I know as you get more lean, it gets hotter, and more advance gets hotter. But after a certain point, it gets cooler.

I will run 2 tanks or so (600 miles) with everything at factory spec. Timing, AFR, idle speed, idle bypass, cold idle speed, etc.

After that, I'll make my changes and log the results.

Would I have to go to a premium fuel to cool it down running more lean & advanced? Would it benefit?

Any savings in fuel is a bonus at 40K miles per year. When I got the truck it was getting 14 mpgs.

Tires are inflated to 50 psi as well.

Thanks,

~ryan

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Old 09-11-2008, 09:07 PM   #2 (permalink)
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Welcome to the forums. I am completely useless to answer any of your questions, but I look forward to the answers and reports on your progress. Thanks for the link to the JAW, I may have to grab one of those to play with.
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Old 09-16-2008, 08:09 PM   #3 (permalink)
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Quote:
Originally Posted by b1gmoose View Post
Any ideas what an ideal EGT would be? How hot can it get before I have to worry about the valve burning?
Have a look here, wise advice: Tech Page

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Would I have to go to a premium fuel to cool it down running more lean & advanced? Would it benefit?
Unless you've modified the hardware with octane-raising mods (raised CR, raised boost, advanced intake camshaft timing, higher intake air temps, warmer thermostat, etc.) you should be able to run the engine on the octane specified by the manufacturer and no higher octane should be needed. If you experience pinging after advancing ignition timing or leaning AFR, retarding ign timing and/or enriching AFR a bit is easier & cheaper.
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Old 09-16-2008, 11:42 PM   #4 (permalink)
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Quote:
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Would I have to go to a premium fuel to cool it down running more lean & advanced? Would it benefit?
Using fuel with a higher octane rating than recommended by the manufacturer will do nothing but cost you more money. Octane is just the resistance of a fuel to detonation.
The way I understand it, burning rich leaves less heat in the engine. The unburned fuel absorbs the heat and then takes that heat with it down the exhaust pipe. That means less fuel economy and probably more pollution. Running lean makes more heat, because there is nothing to absorb the heat except the engine.
One thing that I've been looking into is water injection. The water added to the combustion mix simulates running rich, but with water absorbing the extra heat instead of fuel (I've also read that the water changing to steam helps to add a bit of mechanical power, too). Then you can run leaner and not burn up the engine.
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Old 09-17-2008, 01:43 AM   #5 (permalink)
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vskid3 -

Quote:
Originally Posted by vskid3 View Post
Using fuel with a higher octane rating than recommended by the manufacturer will do nothing but cost you more money. Octane is just the resistance of a fuel to detonation.
The way I understand it, burning rich leaves less heat in the engine. The unburned fuel absorbs the heat and then takes that heat with it down the exhaust pipe. That means less fuel economy and probably more pollution. Running lean makes more heat, because there is nothing to absorb the heat except the engine.
One thing that I've been looking into is water injection. The water added to the combustion mix simulates running rich, but with water absorbing the extra heat instead of fuel (I've also read that the water changing to steam helps to add a bit of mechanical power, too). Then you can run leaner and not burn up the engine.
I've never heard that explanation. Interesting. I thought the unburnt fuel was burned by the catalytic converter to maintain emissions efficiency (aka the reason for the stoichiometric ratio of 14.7:1 air:fuel). Conversely, too much unburnt fuel will "poison" the cat.

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Old 09-17-2008, 04:20 AM   #6 (permalink)
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But if you do wish to run an advanced timing, higher octane fuel will make maximum use of it, My sons Daihatsu Charade pings under load with standard 92 ron fuel and looses power, run it on premium 95 ron and it has more low down torque, never pings and is smoother to take of on steep starts (manual with carbie).
The car is set to standard timing but is obviously a lot happier on higher octane, and it is alot better option than reducing timing and loosing power.
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Old 09-17-2008, 08:03 AM   #7 (permalink)
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Here is an article on the leaning techniques some piston-powered aircraft's pilots use:

Megginson Technologies: Land and Hold Short » Blog Archive » Leaning the Mixture

The wide open throttle/lean of peak (WOT/LOP) mode of operation described, with an alleged 20% less fuel comsumption, is very interesting.
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Old 09-17-2008, 08:30 PM   #8 (permalink)
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Quote:
Originally Posted by vskid3 View Post
The way I understand it, burning rich leaves less heat in the engine. The unburned fuel absorbs the heat and then takes that heat with it down the exhaust pipe.

True; but mostly so at WOT. Not very critical on normal powerplants, but high boost applications, it becomes super critical to combat detonation, and also to lower EGT's

I'm looking for the chart which I found here on EcoModder showing the advantages, disadvantages of each AFR. Does anybody have it off hand?
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Old 09-17-2008, 08:38 PM   #9 (permalink)
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Also; premium could potentially help out, but you will have to crunch the #'s of economy with higher ignition settings and PUG VS RUG with stockish ignition settings.


Typically the toyota ecu pulls much more timing than is necessary to "save" the engine from damage when the timing is advanced.

An old MKIII supra trick is to wrap the threads of the knock sensor with teflon tape (don't forget to ground the sensor!) to partially insulate the knock sensor from knock and there by allowing you to run just a little bit more knock than the factory would allow.

Another trick is to re-wire the knock sensors with rg6 to insulate the signal from EMF, give a cleaner, more accurate knock signal, and allow just a little bit more knock as well.

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