Improving Fuel Economy

[eagle mark]

I have a question about the lean burn thing ... while it exists in the software, were there any physical difference to the engine, or none, and can that be documented and proven?

I ask this because I was thinking about my Typhoon with the oil squirters. How do I know that the ECU change was also not accompanied by some mechanical addition like oil squirters? If I enable it without other possible required safeguards, it would be foolish and probably cause long term damage.

Nothing was changed except programming!

The lean cruise went away after a few years, now it's back! Don't know when but the LS PCM have the capability, just not the code. But Holdens in Austrailia do have it and it's on.

This thread really took off, cool!

Good note on the oil cooling pistons! It is the only cooling they have, water jackets in cylinders walls keeps them under control but oil only for pistons. You can really push spark limits in cruise if you can measure EGT and or oil temps. Oil temps will lag behind EGT but prove the point of to much timing, there is a certain point where detonation can occur without creating knock, it's a sweet spot you want to stay away from. hence find knock and back away at least 2 degrees.

There is a lot of room for more timing in our trucks without hitting knock, reason it's not there is emmissions. Now you have to be careful to add as a truck pulling a trailer will not take as much timing as same truck without. Same for comparable trucks, one on stock tires and one with huge heavy tires. Proper gearing gets them closer but all the weight of tires and wheels is still a factor, have to turn all that weight plus move truck!

great discussion guys

I'm just carbed so I guess my options are more limited. I will run through that checklist of basic stuff just to make sure I'm doing all I can. I love checklists, CK5 should make some more.

I did just switch to a 180* tstat, just because it was routinely running warmer than 210 with the 195*. a little early to tell, but it seems like the 180* might do the trick.

I thought carb trucks ran a 180?

Before you jump in might want to check and see if gauge is accurate and sender is in correct location.

Carb engines are much more forgiving then EFI when it comes to lowering T stat temps. EFI thinks the engine is not warmed up and adds fuel as choke!

 

[kis2]

the 195* was what oreillys pulled up in their system as factory, but I can't tell you if thats true or not, only what their system said .

hooked up a seperate guage before all this and it confirmed the guage is reading right. sender should also be good to go and is a new unit.

next step down was a 160, but I don't think that'd cut it in the winter. it's cooled down here a bit this week, but in the past 24hrs the new 180* tstat seems to be doing much better than the 195.

 

[dyeager535]

the 195* was what oreillys pulled up in their system as factory, but I can't tell you if thats true or not, only what their system said

next step down was a 160, but I don't think that'd cut it in the winter. it's cooled down here a bit this week, but in the past 24hrs the new 180* tstat seems to be doing much better than the 195.

They are correct. It's been 195* I believe since the 60's. Maybe some of the wild stuff like the 302's or something used cooler 'stats stock, but that's because their technology sucks by today's standards.

Thermostat rated temp is not what governs the maximum engine temperature. Cooling system effectiveness is what governs maximum engine temperature. If the cooling system is effective, then the thermostat prevents the engine from being overcooled. If your truck overheats with a 195* thermostat wide open, it has to overheat with a 160* thermostat wide open.

The ONLY difference is that if the engine is cooled to 160* (say a stint at sustained speeds of over 25MPH) when you DO come to a stop, the engine will take LONGER to overheat because the coolant temperature is lower.

I'd posit that your other thermostat wasn't working correctly. Seems most but Delco's anymore run a very high risk of being bad out of the box.

The only time my engine temps climb is when I am crawling up steep grades, or idling. If the fan can't handle that, then the cooling system isn't working correctly, regardless of thermostat rating.

 

[kis2]

dyeager535 I dont want to take this threads time discussing my heating issues, but if you'd be so kind as to check out my build thread I have a whole paragraph about the symptoms, I'd love to know what you think.

 

[Agent_Orange]

i would run my K5 if it ran on endanger baby seals. MPG's hahahaha

 

[crawlink5]

I didn't see where anyone mentioned this so...

With all the mods being done on the drivetrain rpm range gets over looked a lot. Engines are built to give power in a specific rpm range.

Very important - get a cam that produces torque in the range you are cruising in, preferably lower rpms - idle to 2500. Factory cams are not always the best for mpg as they also have to meet emissions. Match the intake rpm range to it - dual plane intake idle to whatever. If you have a carb get one that atomizes fuel well. Not a holley meant to run WOT - you are not driving a race car if you are looking at MPG. Injected is best.

If you are cruising over 2500 rpms you need to not worry about mpg or change that. You need to produce torque as low as you can and cruise there.

Get an O2 sensor and a gauge and watch your numbers so you don't run rich or lean. A good carb should balance this out and efi will control it for you.

Get a vacuum gauge and watch it while you are driving and try to keep the vacuum as high as possible while accelerating and cruising - this is just a control for your foot.

Highway mileage gear it a little on the high side - around town a little on the low side. Decide how much you drive highway and city and make a decision. I believe weight of vehicle may alter this but I have no data. since these Blazers are not on diets you may not gain any by being on the high side - I do not know.

It was mentioned that tires with low rolling resistance is good - definitely. Fresh oil helps in the engine most but also good oil in the tans, xfer, and rear diff. Not gonna argue with anyone on this but I have seen significant difference with Duralube in the drivetrain oils - lowers friction. Get the frontend aligned so you are not creating friction there.

Tune it well, get a good exhaust, keep your foot out of it...

Cummins 4bt here with one tons 4.56, very low rolling resistance tires michelin 11.00x16.00, nv4500, 25mpg highway

 

[crawlink5]

I found the Cummins whitepaper on MPG. While this is geared to big trucks almost all of it pertains to our vehicles directly. Read all of this paper and you will be way ahead of the curve on understanding factors that effect mpg and how much each effects.

What it doesn't go into is changing engine config to get better mpg. But you do need to match power output to rpm range.

It even discusses the effects on driving style due to under powered engines causing drivers to run higher rpms.

http://cumminsengines.com/assets/pdf/Secrets of Better Fuel Economy_whitepaper.pdf

 

[crawlink5]

“For every extra 250 pounds your engine hauls, the car loses about one mile per gallon in fuel economy.” (all other things being equal I'm sure)

Don’t go out of your way to save a few pennies on gas
If it’s convenient to shop at a cheaper place, do so. If not, don’t. On a ten-gallon fill-up, saving five cents a gallon only nets you fifty cents. My car costs about 36 cents per mile to operate. It doesn’t make sense for me to go a mile out of my way to find cheaper gas. (I preach this to people with absolutely no effect what so ever)


links

http://www.offroadadventures.com/articles/view/id/280

http://www.4wheelparts.com/off-road/gas-savings-tips.aspx

 

[dyeager535]

I used to drive a bit out of my way to get gas at Costco, maybe save a few pennies. But I'd sit in line for at least 5 minutes. Not worth the time or effort to go out of your way to save a few cents per gallon.

Now across the street, thats a different story.

 

[ccarley]

What a great thread... I'm especially interested in the lean cruise bit!

So, basically, flip a bit in the chip, and gain highway mileage? Sounds pretty good to me... Now, having the capability to do the magic to the chip? I certainly don't have the software or hardware to do that at the moment. I do wonder though if anyone who sells the chips will have this option turned on?

 

[Blue85]

I have portions of my fuel map set to about 16.5:1 for light highway driving. I never noticed the engine temp trying to creep up or knock. When trying to go leaner the only symptom I've ever seen is the lean surge. It's not like the engine is leaned out everywhere - as soon as vacuum drops the mixture is richened back up.

You can't make much torque that lean, so there may only be certain speeds where it works for you, depending on the gearing, etc. If you have like 35's on 3.08:1, there's no point in setting up lean cruise, as you will never reach "cruise" conditions, except for downhill.

 

[kis2]

well, by taking it slower out of stops and by maintaining 60mph and below, my last 12 gallons got 15.1mpg! that's a real good improvement over 13.7 just for being more concious on the throttle.

and I wasn't peeling out of stops before either, so even if you think you are doing good, see if you can baby that throttle a little more and it might make a noticeable difference!

 

[eagle mark]

I have portions of my fuel map set to about 16.5:1 for light highway driving. I never noticed the engine temp trying to creep up or knock. When trying to go leaner the only symptom I've ever seen is the lean surge. It's not like the engine is leaned out everywhere - as soon as vacuum drops the mixture is richened back up.

You can't make much torque that lean, so there may only be certain speeds where it works for you, depending on the gearing, etc. If you have like 35's on 3.08:1, there's no point in setting up lean cruise, as you will never reach "cruise" conditions, except for downhill.

Engine Coolant temps are not good indicators of to lean, if they are rising it's probably worse then expected. The higher temps would be seen in oil temps as oil is what cools the pistons where the lean heat would be found. Even this takes time to see, it's not instant... dangerous area to be in pushing that far.

 

[eagle mark]

What a great thread... I'm especially interested in the lean cruise bit!

So, basically, flip a bit in the chip, and gain highway mileage? Sounds pretty good to me... Now, having the capability to do the magic to the chip? I certainly don't have the software or hardware to do that at the moment. I do wonder though if anyone who sells the chips will have this option turned on?

Not something you want to do without recording data on the vehicle, especally if vehicle has been modified.

The ECM goes Open Loop during highway lean cruise and uses values from Main VE table. It assumes main VE fueling is correct and takes away fuel resulting in a leaner AFR. If Main VE fuel is off so will lean cruise but now have no correction.