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Old 10-03-2009, 10:58 AM   #1
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Default How can I increase MPG?

I can't seem to break 22mpg. I've tuned for MBT-2* in the cruise cells (yes, that took some time) and the log shows that its pretty close. Even when i run EGO correction I still get the same crummy mpg. Am I a victim of 8.6:1 compression?




Edit:
I'm using EGO correction at 82kpa and below



Any thoughts?

Last edited by hustler; 10-03-2009 at 12:11 PM.
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Old 10-03-2009, 11:04 AM   #2
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Dump your fatass boyfriend.

EDIT:

Seriously...post your target AFRs...even though I'm sure you're not datalogging anymore.

With mileage it's less about torque...and more about sought over bought. You're still seeking enough torque to keep going down the road...but you want to buy it with less gasoline. At MBT you ARE getting the most return on torque for fuel injected....but it's more than you need.

I have NO problem running low 16s in cruise cells. I drive 150miles/day through a mix of sweepers, elevation changes, and a little bit of straight and level...and still get 29mpg. Even at these lean AFRs it rolls right into boost when I punch it.

Joes has a really good AFR target table somewhere. I've got the .vex on my laptop at home. It's way leaner in boost (especially low boost) than you'd like...but does really well everywhere else and is smooth.

With the way your motor is built..and how efficient it is I wouldn't be afraid to run it a little lean where you actually spend 90% of your driving time. I pour gas into it everywhere else.
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Old 10-03-2009, 11:12 AM   #3
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Originally Posted by gospeed81 View Post
Dump your fatass boyfriend.
I'll start that today and let you know how it works out.
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Old 10-03-2009, 11:54 AM   #4
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god you must want to shoot yourself when you see your MPG on the track.

seriously: are you kidding about gas mileage on a track car?
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Old 10-03-2009, 11:58 AM   #5
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This is going to sound funny because it's the opposite of what you do on a track car. To make the car consume less fuel under cruise, the engine needs to be hotter. Hotter motor, hotter charge = less fuel enrichment. You're a vicitim of your own success.

I had my 1.6 tuned pretty well. I went cell to cell on the highway, seeing how lean I could run the car before it starting cutting out. Many areas I could run nearly 19:1.

I used that info and repopulated my AFR target table in MLV. Made the car idle and low load around 14:1 but gradually lean out to 17.5:1 or so in medium load, then get richer again towards high speed cruise. I advanced the **** out of the timing. I had an EGT gauge which was handy.

Got consistent over 30mpg in mixed driving.

Still got around 12mpg in the mountains.
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Old 10-03-2009, 12:04 PM   #6
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god you must want to shoot yourself when you see your MPG on the track.

seriously: are you kidding about gas mileage on a track car?
Do you really think I'm this stupid? Seriously, I understand the difference in fuel consumption and output at 40kpa and 200kpa.

also, I drive this car when its nice out.
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Old 10-03-2009, 12:18 PM   #7
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Quote:
Originally Posted by gospeed81 View Post
Dump your fatass boyfriend.

EDIT:

Seriously...post your target AFRs...even though I'm sure you're not datalogging anymore.

With mileage it's less about torque...and more about sought over bought. You're still seeking enough torque to keep going down the road...but you want to buy it with less gasoline. At MBT you ARE getting the most return on torque for fuel injected....but it's more than you need.

I have NO problem running low 16s in cruise cells. I drive 150miles/day through a mix of sweepers, elevation changes, and a little bit of straight and level...and still get 29mpg. Even at these lean AFRs it rolls right into boost when I punch it.

Joes has a really good AFR target table somewhere. I've got the .vex on my laptop at home. It's way leaner in boost (especially low boost) than you'd like...but does really well everywhere else and is smooth.

With the way your motor is built..and how efficient it is I wouldn't be afraid to run it a little lean where you actually spend 90% of your driving time. I pour gas into it everywhere else.
I spent about a hour tuning it from the passenger seat while Johnfag drove this week. It's much better now, and hits AFR targets the way it did on my old turbo set-up...only now it drives like more of a big-block than it did before. VE values are there, and enrichments are perfect enough that they instantaneously hit target AFR with no more than a .2AFR variance. Even the supercharger shop guy has nothing bad to say about my big turbine and low compression, lol.


I tuned for MBT in cruise, because I could then sustain 70mph on the dyno, in lower load cells (I love steady-state tuning).

As for my engine's "stoutness," I believe its stout in respect to an ability to take lots of spark advance, but my valves and turbine will melt at the same place a stock motor will. I respect the reasonable EGT #'s and leanness with the masses on this forum. Also, shouldn't I be able to achieve MPG similar to a stock engine which runs 14.7:1 at cruise (slightly lower due to my static compression)?
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Old 10-03-2009, 12:26 PM   #8
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Stock motor doesn't have to blow a fan in the exhaust.

Parasitic losses are less with a turbo than SC, but they still exist. No free rides.
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Old 10-03-2009, 12:29 PM   #9
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I know you're not stupid, but you've earned the harassment.

You can definitely go super lean in cruise all the way up to 70 or 80 kPa. I know Ben like to push it a bit higher.

your timing map looks pretty good but you could probably add a few degrees in the midrange to get all your cruise cells into the 40s.

Do you still have EGR? it will help raise cruise mpg slightly.

run narrower overinflated tires on the street (stretch 195s on the 6uls?)

other than that, you're somewhat stuck with what you have i'm afraid.
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Old 10-03-2009, 12:38 PM   #10
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I don't push 'super lean' any higher than that, but I also don't immediatly drop to 12:1 just because I'm 1kPa over atmo pressure either.

I also use EGO and make sure my EGO targets match the targets I tuned for.

I will be disappointed if I'm not in highest upper 20's mpg when my new engine management is completed & tuned. That's with a heavy street car with 8" wheels.

You probably can't lighten you car enough to touch what the internally stock 1.6 crowd does for economy.
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Old 10-03-2009, 12:39 PM   #11
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Quote:
Originally Posted by Ben View Post
I don't push 'super lean' any higher than that, but I also don't immediatly drop to 12:1 just because I'm 1kPa over atmo pressure either.

I also use EGO and make sure my EGO targets match the targets I tuned for.
+1

I run mid 13's up to about 130kPa.
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Old 10-03-2009, 02:27 PM   #12
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Quote:
Originally Posted by Ben View Post
I don't push 'super lean' any higher than that, but I also don't immediatly drop to 12:1 just because I'm 1kPa over atmo pressure either.
I let the dyno do the talking out which AFR to use. The 101+ka VE and spark numbers were chosen from steady-state pulls and ramp pulls, not preconceived notions.
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Old 10-03-2009, 02:30 PM   #13
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Quote:
Originally Posted by y8s View Post
I know you're not stupid, but you've earned the harassment.

You can definitely go super lean in cruise all the way up to 70 or 80 kPa. I know Ben like to push it a bit higher.

your timing map looks pretty good but you could probably add a few degrees in the midrange to get all your cruise cells into the 40s.

Do you still have EGR? it will help raise cruise mpg slightly.

run narrower overinflated tires on the street (stretch 195s on the 6uls?)

other than that, you're somewhat stuck with what you have i'm afraid.
i need to install the EGT if I'm going any higher than 15...but mazda can make it happen lower.

adding spark in those cells did not increase output.

I never had egr in my 1991.99 motor. lol
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Old 10-03-2009, 02:34 PM   #14
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Blah blah blah.

Why do you need to steady state tune for max power at such low mani pressure? Max power = max fuel. You're not there for longer than a split second when you are actually calling upon power--and when you are, you have acceleration enrichment. News flash: AE adds fuel.

How often are you at WOT and 2 psi?

As you continue to take 'roids, your ***** will keep shrinking.
Which do you want, big arms or big *****?

I'm glad that you can read, since you're writing checks with my money. Try to use your ******* head sometimes.

Otherwise, using a steady state dyno to tune for max power instead of an "ideal" air/fuel ratio is ******* brilliant, and something that most people can't seem to grasp.
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Old 10-03-2009, 02:49 PM   #15
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I thought tuning spark numbers in cruise at low kpa for max output would produce the best mpg. I don't understand why it won't. Maintaining wheel speed, at a lower kpa, with a constant AFR is less total fuel squirted.

there is no such thing as WOT at 2psi in this car. lol

I've spent about 4-hours on the dyno now getting this crap right...I don't understand how I'm doing it wrong if output is favorable. I can lean out the 101-150kpa cells, but that's not what the dyno told me to do.

I always though enrichment tuning was there to hit target AFR when stomping on the throttle...should I adjust my logic and use enrichment differently?

I don't know which direction to go ATM...any thoughts?
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Old 10-03-2009, 02:57 PM   #16
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i'm thinking you may be right with your 8.6:1 hurting you, it's just not as efficient out of boost as higher compression. like others said i can cruise 16:1 no problem, actually much of the low end of my map is fairly lean.

are you getting 22mpg city, highway or mixed?
also you could run 2 maps
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Old 10-03-2009, 03:10 PM   #17
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Ben tried to tell you earlier what I was thinking about over lunch...

Tuning for power and tuning for efficiency are two different things.

I say that...but you are really tuned for max efficiency...just on a different level...a level much higher than what you need to just tool down the road. EDIT: You are now trying to tune for relative fuel efficiency...not just the efficiency of your motor based on output. These are two very different things. You are thinking in terms of absolute thermodynamic effiency. Fuel efficiency in terms of gas mileage is relative since it deals with consumption and distance traveled, regardless of displacement, output, or volumetric efficiency. You end up telling the ECU the motor is less efficient than it really is there...and feed it less fuel...creating a lean condition that achieves the same amount of work (traveling at 65mph) while consuming less fuel. [/EDIT]

I repeat...there is NO reason not to seriously lean out the cruise cells. As soon as you roll on the throttle you will get accel enrichments and the manifold pressure will increase. Your AFRs will be fine...and MS is smooth enough. If my shitty tune allows me to pick manifold pressure within 1psi at whatever rpm I want then your badass tune and calibrated right foot can get even more out of this ECU that we run.

1. Lean cruise cells.
2. Tune AE
3. ???
4. Profit
5. Stop complaining
6. Consider leaning a little more (read higher up) after you get a pyrometer.

If you really want to start leaning things out think about WI. I'm super lean right now everywhere since this became a DD and not a project car anymore. I see 12.4:1 at 10psi...and just barely picked up some det on the cans at around 5K rpm with Scott's timing map. I pulled out timing that I can add back in because I'm finally as happy with my fueling map as I can be without hitting a steady state...which will never happen with my setup.

I want to leave fuel where it's at...put on this stinkin' Devil'sOwn kit I have sitting on the shelf...and then add timing back in. I'm also hoping COPS will help keep things a little more consistent and smooth...and LONG to run +0.035" spark plug gaps.

My map was the result of many datalogs with some carefully researched AFR targets (not the ultra rich hand me downs everyone spouts), and then days worth of hand smoothing until I could look down at the LC-1 gauge anytime/anywhere and be content.

I know it doesn't compare to your level of tuning, but the same basic principles apply...and always will.

You can get away with going leaner.

Going leaner is the only way to increase gas mileage with regards to fuel.

You can't get any more out of your spark table, and we all know that. So besides aero, weight and rolling resistance, you're left playing with the VE cells you spend most of your time in.

EDIT:

On number six above I'm talking about the 100-130kPa cells. I purposely tune those for ~13.5:1 as that is near the leaner limit of max torque for gasoline..and if I'm lingering in those cells it's where I'm accelerating (on ramp, passing etc) where I'm at part throttle...but building some boost, but am far away from detonation.

Last edited by gospeed81; 10-03-2009 at 03:42 PM.
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Old 10-03-2009, 03:16 PM   #18
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tune cruise at cruise. maximizing power at part throttle is a meaningless endeavor. in fact, for cruise, the goal is to REDUCE power at a given throttle position. Why? Because the further you open the throttle, the lower the pumping losses you have to overcome to move the car. That's why EGR helps. it reduces power produced at a given cruise throttle opening so you're forced to open the throttle more. you're still only producing enough power to move under nearly no load, so the fuel consumption drops slightly.

short answer: if your goal is better MPG at cruise, set your AFR targets to 15.5:1 to start and autotune from 35-80 kPa and from 2500-5000 rpm.

your EGT will not be near dangerously high at lean cruise because of the 40+ degree spark advance and reduced exhaust volume.
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Old 10-03-2009, 03:27 PM   #19
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EGR reduces the amount of O2 contained in the combustion chamber, by adding air that has spent all of its O2, this allows a reduction in the amount of fuel required to completely burn the volume of AF in the chamber. This lowers combustion temperature which reduces NOX. The end results are reduced emissions and better fuel economy.

If the given ECM was to note the amount of flow of EGR, it could reduce fuel delivered, creating some fuel economy.

Ron
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Old 10-03-2009, 03:38 PM   #20
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Well put [email protected] I think you and I are largely on the same page, and our end result is common, but remember we're dealing with hardware not provisioned for EGR.

You're using EGR to reduce temp, by decreasing o2, and then decreasing metered fuel. I'm just squirting less fuel.

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Get that bitch running lean, and your economy will improve. This might sound like a stretch, but I assure you that the amount of fuel squirted is inversely related to economy.
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