Cleo has become an MPG project - Gas Savers

philip1 · 03-13-2011, 07:28 PM

I picked up a programable ecu for my BMW. The plan is lean her down at part throttle as much as I can get away with and see what happens.

pgfpro · 03-13-2011, 11:03 PM

Quote:

Originally Posted by philip1

I picked up a programable ecu for my BMW. The plan is lean her down at part throttle as much as I can get away with and see what happens.

What kind of BMW?

DRW · 03-13-2011, 11:22 PM

Excellent! Is there a commented disassembly for that ecu?
I've enjoyed the mods I put into mine. I had some good results from lowering cold idle and leaning out cold enrichments.

philip1 · 03-14-2011, 05:08 PM

The car is an old 1988 535i with 256k miles on the clock. I've lowered her with Bilstein shocks on Spax springs. This weekend I will be adding an airdam and sway bars as well as the ecu. All told I should be able to reduce the drag from .4cd to probably .36cd and fuel milage should climb above (not much but above) 35 on the highway.

philip1 · 03-14-2011, 05:40 PM

Photo of Cleo the 535i

This is how she looks right now.

pgfpro · 03-14-2011, 05:46 PM

Quote:

Originally Posted by philip1

Photo of Cleo the 535i

This is how she looks right now.

Nice!!! I always like the looks of those cars.

philip1 · 03-14-2011, 05:52 PM

I won't be doing any mods that detract from those looks. I am sure the air dam will improve looks as well as reducing drag.

philip1 · 03-15-2011, 08:41 PM

Finally got a base tune for the computer so she'll at least run. Next begins project lean out.

This is a paint can pistoned brute so I don't know how lean I can make her. I'll do it slow till she starts bucking then add a tiny bit to keep her smooth. Any thoughts pgfro?

I will have some rudimentary feedback systems, AFM readout, narrow o2 and my decades of feeling out carb tunes.

**theholycow** · 03-16-2011, 07:05 AM

I'm not familiar with the phrase "paint can piston"; does that mean that the pistons are not very strong, or that the bore is wide?

pgfpro · 03-16-2011, 08:22 AM

Quote:

Originally Posted by philip1

Finally got a base tune for the computer so she'll at least run. Next begins project lean out.

This is a paint can pistoned brute so I don't know how lean I can make her. I'll do it slow till she starts bucking then add a tiny bit to keep her smooth. Any thoughts pgfro?

I will have some rudimentary feedback systems, AFM readout, narrow o2 and my decades of feeling out carb tunes.

Sounds like a good plan. Can you change the emulsion tubes and air bleeds?

If you can I would go for the highest amount of atomization you can with these to parts of the circuit then start reducing the main jets. Then start adding some more ignition timing advance.

Do your carbs have a dual power valve circuit? I would keep a careful eye on the vacuum gauge and to dial in the power valve if so. You can also usually run a restrictor wire in the power enrichment channel (the one that feeds the main jet wells) to lean down the lower vacuum areas.

Also you can always come up with ways to add more heat to the heat cross-over in the intake manifold to help with atomization and lean down.

philip1 · 03-16-2011, 04:48 PM

She is actually efi but what I was getting at is I know how extremely lean conditions feel. The paint can remark was a comment about the pistons they are huge.

philip1 · 03-16-2011, 06:55 PM

Just today short sample 34.5 mpg for the last 20 miles

pgfpro · 03-16-2011, 10:51 PM

Quote:

Originally Posted by philip1

She is actually efi but what I was getting at is I know how extremely lean conditions feel. The paint can remark was a comment about the pistons they are huge.

Oops

Sorry I thought you were running a carb.

Then I would go with your original plan and start taking away fuel until you notice a slight misfire then add some fuel back to get it to run smooth as you said.

philip1 · 03-17-2011, 06:17 PM

I think I have a lot of ignition I can add too, if needed.

philip1 · 03-19-2011, 07:12 PM

I've written a tune with fuel pulse widths reduced by 5ms in the 1400-3200rpm and 18-48% load range and ignition advanced 3 deg there too. I'll test it out tomorrow.

DRW · 03-20-2011, 04:20 PM

Quote:

Originally Posted by philip1

I've written a tune with fuel pulse widths reduced by 5ms in the 1400-3200rpm and 18-48% load range and ignition advanced 3 deg there too. I'll test it out tomorrow.

"5 ms"? Is that right? Maybe I'm used to the injector time scale on my car, but that sounds like a lot. Are you sure the units aren't Us?
ms= millisecond=0.001 second
Us= microsecond = 0.000,001 second
What's the stock injector pulsewidth in the load/rpm range where you plan to make those changes?

philip1 · 03-20-2011, 04:39 PM

Tbh I have no idea what units they are using but I reduced the number by 5

philip1 · 03-20-2011, 05:37 PM

Here are screen shots of the maps the first is the stock map with the affected area highlighted I haves also highlighted the altered map.

stock map

Altered map

Hmmm looks like I went 7 instead of 5 oh well.

DRW · 03-21-2011, 12:43 AM

Ah, I see. In that case I'd simplify and convert into %. For example, 117-7=110.
117/110=6% change.
Assuming the stock map is aiming for stoich 14.7 AF ratio, removing 6% should put it around 15.6 AF ratio.
math;
14.7 parts air mixed with 1 part fuel =14.7:1
14.7 parts air mixed with .94 parts fuel =15.6:1 from removing 6% fuel.
14.7/.90 = 16.3 AF ratio from removing 10% fuel.

pgfpro · 03-21-2011, 08:30 AM

Looks like a raw number scale.

So what DRW did should give you how much fuel you've taken away.

philip1 · 03-21-2011, 11:56 AM

I tried the lean tune out today... Good thing I have several tunes to switch between. I had to go back to my base tune. I pulled too much fuel or didn't add enough timing. I had missing and shuttering till I switched back to the base tune.

philip1 · 03-23-2011, 07:00 PM

Ok I got a tune that works lots of ignition timing and pretty lean but it pulls better too.

DRW · 03-23-2011, 10:15 PM

Good progress! I also get misfires sometimes, I tune it so it's on the edge of misfires. Sometimes if the car is started when it's hot it'll misfire if I jump into lean burn mode too quickly, but that's rare. 99% of the time it runs nice with no signs of anything unusual except for a flatlined wideband gauge.

Gapping the spark plugs a little wider reduced misfires slightly on my car. It might be worth a try.

philip1 · 03-24-2011, 06:33 AM

I have my plugs gapped on the wider side of spec (.028-.032) at .034. I think my problem was I was not agressive enough with the timing.

philip1 · 03-28-2011, 07:16 PM

I just had an epiphany. If the oxygen sensor is on changes to the fuel map are negated. New plan tune a lean cruise open loop tune.

SarkOzy · 03-29-2011, 05:46 AM

A few thoughts.........

I'm not familiar with BMW systems, but you should look around and see if there is some sort of factory lean cruise subroutine already included in the ECM, just not turned on. Coming from the GM world we're very lucky in the fact that these modes are already programmed in, albeit not turned on due to EPA regulations concerning tailpipe emissions.

That being said, I think you're going about this incorrectly. De-fueling the engine to the point of sacrificing drivability isn't going to garner a substantial increase in economy. In OEM lean-cruise modes, it's only activated when a certain cruise parameter is set. By that I mean the engine is only lean at highway cruise speeds with very little load. If you spend a good deal of time at steady speeds then it's great.

You have the right idea by going open loop......the factory GM code is sort of a quasi-open loop mode that adds up to 50 degrees of SA while commanding anywhere from 16.2 to 16.7 AFR (get a wideband and tune in Lamda and you'll be better off) at cruise. It goes in and out of this mode to protect the catalytic converters. For me, the gain in economy is 20-30% in similar weather conditions. So it works.

I would GREATLY benefit you to get a wideband O2 sensor if you're going to be playing with the fueling. Stock narrowbands are great as long as you're right around stoich, anything else and they're junk. I'd really hate to see you blow a hole in a piston accelerating onto the highway because the engine is too lean.

philip1 · 03-29-2011, 07:29 AM

First the ecu is aftermarket the stock one has one program. Second I will not be blowing a hole in anything this computer has a separate map for acceleration. Next I am pulling fuel in just the light throttle cruise section about 1000rpm will be affected. I am adding timing across the board to improve economy slightly in regular modes I am not advancing it to detonation that would be stupid. As far as a wide band yes I will be getting one but for now I have been borrowing one when I tune.

trollbait · 03-29-2011, 09:57 AM

Quote:

I'm not familiar with BMW systems, but you should look around and see if there is some sort of factory lean cruise subroutine already included in the ECM, just not turned on. Coming from the GM world we're very lucky in the fact that these modes are already programmed in, albeit not turned on due to EPA regulations concerning tailpipe emissions.

Going off topic, how do you find out if this routine exists, and how to turn it on?

philip1 · 03-29-2011, 10:47 AM

On your HHR you will need either a really agreeable dealer or hptuners.

philip1 · 03-29-2011, 10:53 AM

I have expanded the rpm range to lean out. I now have leaned out from 1800 to 2600 and up to 40% load. This will cover pretty much all cruise conditions. Switching between the stock tune and the modified tune while on level ground steady throttle and speed (60mph) I saw instant milage change by 7 mpg with no change in the feel of the car.

I have an ecu that allows instant switching between tunes.