Tuning EFI for economy.

[Sam Powell]

I have a 69 Dart slant six with electronic EFI which is fully programmable. I can set fuel ratio, timing, and warm up enrichment rate to anything I wish. First goal was drivability, which is now pretty good. I am eager to learn more about tuning tips to improve economy.

The first big, positive change came a month ago. I took a 600 mile round trip with it from the DC area to Blacksburg VA. On the way down the car got 21.5 MPG. I raised the cruise timing from about 40 BTDC to 55. The mileage on the way back was 26.7. I would like to get this car over 30 MPG, and from what I have read here, this should not be impossible.

The car has a Ford Mustang 5 speed which is much more efficient than the old auto.

Any ideas about tweaking the tuning would be appreciated. Maybe a link to another thread would be a good place to start. Thanks in advance.

Sam

[rmay635703]

Since you have a steel / cast iron rig its best to play with timing when cruising along, sadly you still have aluminum pistons which you could blow holes in though.

You could also setup lean cruise, you would need to determine what gear / RPM you typically cruise at and the coresponding load then create an island where you go in open loop or if you have a wideband end up with a lean burn situation, most engines run fine at 15-16.5:1 so long as you are loaded up between 40-80% (fluffy numbers), too light of a load and it won't fire, too much and you burn holes in pistons.

There are a couple folks on here who made vehicles go lean, higher compression and knock detection are a must when running lean, high percentages of ethanol work well for leaner than normal AFRs

have fun.

[Sam Powell]

Thanks for the reply. The engine is built with Forged pistons and does have a knock sensor that works well.I also have a wide band O2 sensor that feeds both an in-dash gauge and the ECU. I have been cruising at 16.5 with no knock. However the cooler weather has caused some pre-ignition at 3000 RPM under light load right before shifting. I could go a little richer there, or dial the timing back a bit there. The system has a self tune that will change the fuel map to match the AF table, (user set). Others using Megasquit II have experienced lean conditions when it gets cold outside. I think most have simply dialed up the mixture a bit across the board.

Tell me what you mean by "loaded up". What is 40-80%. Percent of what? Thanks. Car cruises at 2000 rrm at 62 MPH. Compression is 8.5:1. It was intended to be turbo charged, but that never quite worked, so I removed it. Now economy is the game.

One of the things I have tried to figure out is if at 40 MPH it is more efficient to cruise in 5th at 1200rpm, which it will do, or in 4th at 1700 rpm. The AF ratio gets leaner in 4th, and the map reading drops. But I have not had the time or commitment to go out and drive 100 miles at 40 in 4th gear and then drive another 100 miles 5th an compare actual mileage. It would be difficult to find a place in the east coast here where one could actually do that. I suppose if I worked the math maybe I could figure it out. The computer does give me milliseconds of injector open time as one of its readouts. But it does not do the match as scan gauge does.

One feature this ECU has is an overrun fuel cutoff. When coasting in high vacuum, it cuts fuel off completely and starts it again when you open the throttle a bit. Until I enabled that feature, the excess fuel would cause a miss that was quite disruptive to the RPM read on the ECU. I was forced to find out about this fine feature and put it to use.

I am one of those guys who uses Evans coolant. It has been in there for 3 years. There are open questions about what temp to run the coolant, and what temp to have the fans turn on. There is one 16" two stage fan, with separate temp controls on the radiator itself, not in the block. I feel certain wit6h the right solid state controller I could get the sending unit in the block to control the fan. I think the ECu can be made to do this but not two stage (I think).

I am very interested right now in figuring out a way to automate a radiator block when cold. Does anybody know of an easy way to do this? Are there products intended for other uses that can be adapted? Are there OEM pieces that can be modified and put to use? I read on another thread that the Chevy Cruze has such a feature. I know the newer Mopar trucks and cars employ this also, but have not looked into it. Maybe there is a thread already working that discusses one. Thanks again for the response. I feel this is going to be a big help in my tuning and tweaking.

Sam

[rmay635703]

Originally Posted by Sam Powell

However the cooler weather has caused some pre-ignition at 3000 RPM under light load right before shifting.

You could create a true DFCO configuration and it might stop the pre-ignition, when you fully lift your foot off the throttle and RPMs are above a threshhold (maybe 1200rpms) just have them completely off, you could then learn to just fully lift your foot before shifting and pre-ignition would be minimized because there would be no fuel.

Originally Posted by Sam Powell

Tell me what you mean by "loaded up". What is 40-80%. Percent of what? Thanks. Car cruises at 2000 rrm at 62 MPH. Compression is 8.5:1. It was intended to be turbo charged, but that never quite worked, so I removed it. Now economy is the game.

by loaded up i mean a percentage of max output, lean burn works best with more fuel (and more load and air), lots of turbulence and warm temperatures,
you might consider a warm intake mod and see if it affects knock.

Originally Posted by Sam Powell

One of the things I have tried to figure out is if at 40 MPH it is more efficient to cruise in 5th at 1200rpm, which it will do, or in 4th at 1700 rpm. The AF ratio gets leaner in 4th, and the map reading drops. But I have not had the time or commitment to go out and drive 100 miles at 40 in 4th gear and then drive another 100 miles 5th an compare actual mileage. It would be difficult to find a place in the east coast here where one could actually do that. I suppose if I worked the math maybe I could figure it out. The computer does give me milliseconds of injector open time as one of its readouts. But it does not do the match as scan gauge does.

Sam

Can't help much on this, generally higher load trumps lean burn but only to a certain rpm which varies from engine to engine.

My guess is the lower rpm wins as the difference between 4th and 5th is too great on a relatively sizable motor.

[ron22]

Shame you have such low compression ratio. I think with 91 Oct gas you could have went higher.
I think you are on the right track with the 16.5:1 air mixture. Have you tried higher to see when you start getting knock? I believe Honda had 22:1 but this was on an engine that was designed around that idea.
Can you have the higher air/fuel mixture only kick in under certain conditions? Cruising only. Turn off when you step on the gas pedal.
Who much control does the Megasquit II give you?

[Sam Powell]

I get it now. You mean to make the ratio richer when the engine is under load. And to answer ron22's question, the Megasquirt is pretty flexible. I can make the ratio richer under the higher load conditions. That is very easy. And yes, I think one key here is to make a warm air pickup that can be engaged during cool weather. The air filter picks up air from out side, in the wheel well. I would have to think about it, but I think I can redesign the pickup so there is a flap inside the box that would switch over to a second pick up tube that routes to inside the header heat shield. There were lots of stock set ups back in the 80's and 90's that did this. I think I would have to cruise a junk yard and see what I could find in the way of temp sensors that control a airflow diverter of some kind. I love going to junk yards.

Ron, You are right about the compression ratio. The low ratio is because it was intended to be turbo charged initially. There is no squish chamber on these old heads. They are an ancient, 1959 design. This makes preignition a challenge. Thinking about it now, one would wonder if it would be possible to fill part of the chamber with weld material to create a squish area. Maybe next time.

This air box came from a late 80's Cadillac. The pick up goes right straight down into the wheel well. The battery is in the trunk.



Sam

[ron22]

I am no expert on Honda and the "lean burn" mode. But I think for best cruise MPG you would want to try something like that.
Under the right conditions you lean out as far as possible (will need testing) if any of the conditions change go back to "normal" mixture ratio. I think you might have to play with mixture and timing here.
Example you step on the Gas to accelerate. The engine load goes up (going up hill). I think you get the idea.
Now how many times can you change the mixture and timing?
Have one for gas pedal to the floor (max power & max load)
Have one for normal acceleration (medium load)
I think you get the idea.
I think you will find 1 AF ratio and 1 Timing is not going to cut it.
That said sounds like you have a lot of fun experimenting ahead of you.

[Sam Powell]

Fueling andtiming are extremely flexible with MEgasquirt. There are 3 primary, basic tables, and many trim tables. The basic ones are a 12x12 AF ratio matrix, a 12x12 fuel amount (called a VE table) and a 16x16 timing table. In each the rpm which is user defined is across the bottom of the table, and the MAP (load) goes up the vertical axis of the table. Every cell can have its own number. This means for every RPM and load you can have a specific timing and fueling amount. The wideband O2 sensor adjusts the fueling within the parameters the user sets to match what is in the AF table. The actual amount of timing or fueling is an interpolation of the number in the cell, and the numbers in cells around it if the RPM or MAP load is on the edge of two cells, or even 4 if it is in a corner.

I can make this engine run any way I want to. I just need to know what to try. I am not an IT person. Getting the soft ware downloaded and talking to the ECU was not easy, as I needed my daughter's help. So discussions of trying to get mileage feedback recorded and readable go over my head. This does not mean I am not interested in doing it some day. I can tune the actual ECU now, which was an accomplishment for a 68 year old man.

Right now the engine idles at 13.5:1 which is a little rich, but this is batch fire, multipoint injection, not sequential. There is fuel behind the valve awaiting its opening, which can get sucked into another cylinder and disrupt the AF ratio for that cylindar. However it runs at speed nicely at 16.5:1 as long as the load is low. It will cruise down a level highway at 45 MPH and 18 inches of vacuum all day. If I ever get the ECU reconfigured to read the pick up wheel and sensor instead of the distributor, I can set it up as sequential. But it runs now, and am not eager to shake things up much at this point.

The trim tables are such things as warm up enrichment, start up enrichment, start up timing, cold timing, etc. etc. There is an idle timing trim table that will bump extra timing into it when you first crack the throttle for drivability.

Thanks in advance for any tuning suggestions you can offer.
Sam

[Sam Powell]

Originally Posted by ron22

Shame you have such low compression ratio. I think with 91 Oct gas you could have went higher.
I think you are on the right track with the 16.5:1 air mixture. Have you tried higher to see when you start getting knock? I believe Honda had 22:1 but this was on an engine that was designed around that idea.
Can you have the higher air/fuel mixture only kick in under certain conditions? Cruising only. Turn off when you step on the gas pedal.
Who much control does the Megasquit II give you?

I plan an extended cruise soon with a friend to play with the timing. The strategy, when a dyno is not available, is to advance timing until the detonation gauge begins to light up, and then back off a degree or so. With a dyno you look for max HP, but sadly I do not have one. All the ones around here are not steady state dynos, which is what is required to set timing for cruise. Read above post for description of tuning capabilities of Mega Squirt.

Thanks as always for advice and ideas.

Sam

[RustyLugNut]

Good work. Subscribed!