Slant Six Forum
https://slantsix.org/forum/

Does anybody ever experiment with lean burn mods?
https://slantsix.org/forum/viewtopic.php?t=32077		 Page 1 of 1
Author:  Ed Mullen [ Tue Nov 04, 2008 10:17 am ]
Post subject:  Does anybody ever experiment with lean burn mods?
I mean instead of just switching to EI?

Is there any info on tweaking or troubleshooting the system?

I just remedied a bunch of weirdness by adjusting the link between the pedal and the throttle on my van (throttle to trans already adjusted).

It seems to make a world of difference in the size of the shot of gas it gets at startup. Also makes it a little more responsive.

It seems to me that if I could get a little extra advance timing when I hit the pedal, that it'd take off alot more smoothly.

Has anyone ever devised a way to boost vacuum to the ESA modulator thing at an appropriate moment (i.e. at the point the power valve is opened?)

I'd also like to entertain keeping the lean burn until it fails in some catastrophic way. How do I make sure all it's components are operating within spec?

Also...

Does anyone know the optimal jet sizes for a Holley 1945 on stock slant van with lean burn? (the people who rebuilt it seem to have done a good job, they did flow tests and other stuff before giving it back, but they did everything per factory spec, not optimal useage).
Author:  Reed [ Tue Nov 04, 2008 10:45 am ]
Post subject: 
Good luck. I am not aware of any hot-rod techniques to be used with the lean-burn system. My recommendation would be to get a digital multimeter and a factory service manual for your van. If you really want to keep the lean burn, be prepared to spend lots of time teaching yourself about the system and how to troubleshoot it. You might be able to advance the base timing a few degrees, but that would be the only timing adjustment you could do.
Author:  Matt Cramer [ Tue Nov 04, 2008 11:07 am ]
Post subject: 
I am using a Lean Burn distributor wired to a Megasquirt instead of a Lean Burn computer to give me direct control over the timing. There is also an MSD programmable timing computer that could be wired to the distributor.

The only way I could see adjusting the timing curve on a Lean Burn without reverse engineering the program on the chip would be to take an Apex'i Super AFC or similar piggyback controller from the import world, and splicing its wires in between the MAP sensor and the Lean Burn computer. This one would adjust the MAP sensor reading that the computer "sees" to change the timing curve.
Author:  SlantSixDan [ Tue Nov 04, 2008 11:25 am ]
Post subject: 
The Lean Burn system is a complete dead end as far as improvements to performance, driveability, or mileage. Your money, time, and effort are much, much, much better spent converting to conventional electronic ignition (Mopar or HEI) and proceeding from there.
Author:  Ed Mullen [ Tue Nov 04, 2008 2:03 pm ]
Post subject: 
Quote:
The Lean Burn system is a complete dead end as far as improvements to performance, driveability, or mileage. Your money, time, and effort are much, much, much better spent converting to conventional electronic ignition (Mopar or HEI) and proceeding from there.
yeah, that's the idea that I'm getting

(in four years I'm getting historic plates, and never going through inspection again. Until then I need to keep up appearances under the hood. I guess I could always hollow out the ESA and put the module and ballast inside it with a small fan to cool them.)
Author:  SlantSixDan [ Tue Nov 04, 2008 2:08 pm ]
Post subject: 
You needn't go to any such lengths. Extra boxes and wires won't be noticed; at most they're checking to see if all the original widgets are in place. And I'm betting they're not checking to see if the Lean Burn's there, but to make sure you haven't disabled the PCV, removed the EGR, and that kind of thing.
Author:  Reed [ Tue Nov 04, 2008 2:57 pm ]
Post subject: 
Plus, HEI is so small you could hide it easily in the mess of hoses and wires in your engine compartment.
Author:  Ed Mullen [ Tue Nov 04, 2008 3:44 pm ]
Post subject: 
I was kidding, really, but the last time I took it through NJ inspection I met the Spanish inquisition because my target gasses (apart from CO) were so low.

The station manager was insinuating that I had somehow tampered with the van in such a way that the inspectors missed (and since they missed it, he wasn't going to push the issue and get his men in trouble, but he wanted me to know that he was on to me).

Of course the extent of my 'tampering' was a tuneup, cleaning some parts, having the carb rebuilt and replacing all the vacuum line and the cat.

I eventually got through for CO by connecting my EGR valve to direct manifold vacuum in the parking lot, and going through reinspection for the fourth time. It passed by 5 parts per billion. I think at that point the manager was convinced I was not only 'tampering,' but delving into black arts to do so.

(I found out later the elevated CO was due to a leaking fuel pump diapram. Had I just pulled the PCV valve and breather out of the valve cover the CO would've dropped tons, but the manager would have had me burned as a witch.)
Author:  coconuteater64 [ Wed Nov 05, 2008 8:10 pm ]
Post subject: 
I experimented with my lean burn system; I saw how far I could throw it! :D
Seriously, my old man had one van with the lean bum system when I was in high school. It ran great. Mine..not so much. I think that's because the PO started monkeying around with it.

My advice: toss it.
Author:  cw6er [ Thu Nov 06, 2008 9:19 am ]
Post subject:  Re: Does anybody ever experiment with lean burn mods?
Quote:
I mean instead of just switching to EI?

Is there any info on tweaking or troubleshooting the system?
Well, it's nice to know I'm not the only idiot out there that still has the Lean Burn computer. :shock:

I've got an '81 D150 truck also with the Holley 1945 and it is a "Home Center/Airport Beater". You know, hauling trash or willing to leave it in the airport lot for a month in the blazing sun as people beat on it with their doors while you're away on vacation. :roll:

I, too, see keeping the Lean Burn for a while for 2 reasons: A kind of perverse determination to make what I've got run right and the fact that by the time I spent the money to buy a distributor, ignition module, harness and carburetor, I would have more in it then I originally paid for it!! :D 8)

Who knows, maybe others will see your brave confession and will come out of the closet and admit that they still have a lean Burn system and we can use this thread to get our systems running right while others mock us from the sidelines. :mrgreen:

Seriously, the PO did an engine swap in mine, and I need to fix all of his screw-ups and get the engine running right, to factory specs, as a baseline before making any changes or the changes can just mask or hide problems caused by something else.

I look forward to comparing notes on the two systems, for instance:

I would have thought the later systems would have a "feed back" carb with an O2 sensor, but the 1945 is not a feed back carb, so what sensors are on your system?
Author:  Ed Mullen [ Thu Nov 06, 2008 6:38 pm ]
Post subject: 
Quote:
so what sensors are on your system?
Not many:

temp sensor at front of head

unknown sensor (i.e. 7/8" diameter x1/4" sheetmetal cylinder on 1"x2" sheetmetal tab bolted to head between valve cover and manifold)

intake air sensor in intake manifold (for EGR, as I understand it. Autozone actually sells that one and they use 'EGR' in the name)

That's it for sensors.

Controls-wise:

solenoid valve to operate vacuum servo valve that switches between downstream and upstream AIR injection.

solenoid valve between vacuum amplifier and EGR valve

lean burn distributor

It does not have any controls on the carb apart from a solenoid that was apparently for the A/C which I've gotten rid of (the solenoid remains with the wires cut off as a curb idle adjustment stop--can't seem to locate the non-A/C equivalent)

as far as 1945s not being feedback: I think I've seen them with a solenoid purge valve (might have been a 6145?--don't know if that counts as 'feedback' anyway.)

van was made in Canada, btw.

I am of the mindset that with this silly antique control unit that measures so little, and controls even less, could easily be replaced, while the rest of the system be restored to the way it was meant to operate ('easily' being a relative term)

I would love to plug my lean burn harness and vacuum line into a tweakable/adjustable unit. It seems I would need an ESA with a working vacuum modulator, and a clear idea of what range of signals come from which sensors under which conditions. A fresh PC board could be cut to fit in the spot of the original.

In the most extreme (but in other ways, the simplest) approach, a laptop and a lab controller wired to the harness and vacuum modulator could replace the ESA. The whole thing could be solved with software, and other sensors/controls could be added.

I'd much rather go the more primitive (but harder to actually pull off) idea of a series of logic circuits with maybe some PC-mountable mini pots to make adjustments.

Realistically, the only important thing that the ESA does is control timing.

As such, nobody is going to win any arguments against EI conversion from a practical standpoint.

I'm not trying to be practical. I need to control my distributor. I look for ways to do it , and the only answer I get is 'get another (older) distributor and control it by another (older) method.'

My next question is 'why do I need to change distributors to control one?' and the only answers are 'because you don't know how to control the one you have, and it's the cheapest easiest thing we know.' (I'm not even commenting on this forum. Across the entire internet, the only information on Lean Burn is how and why to get rid of it. It's been my experience that I get the best information, and most thought out answers, from this forum of all the sites I'm aware of applicable to my van. This is the only topic I can think of where the popular answer is the same as that of all other venues.)

I can't think of anything else I run into in life where I accept me not knowing a thing as a reason to abandon something, and do something else.

Matt Cramer is on to something (see his post on this thread) but I would rather make something than buy something. There just seems to be no good information available on this topic to go on.

I guess I have to break down and get a FSM, but I doubt it will have enough info to even reverse engineer from. (If it was a Honda or Bosch ECU I'm sure there would be tons of info provided by undergrad electrical engineer nerds on the web.)

An electronic distributer should be able to outperform something that works on suction and springs. Pulling out what should be the superior technology to replace it with stuff 15-20 years older than the vehicle it goes in seems silly (then again, so does using an ESA in 1987 that was designed 10 years earlier, when that particular 10 years saw huge strides in what can be done electronically in other fields--or the same exact field in other countries...Sweden, Germany, etc.--I understand that slanted vans weren't Mopar's top priority at that time--or ever--but still...I don't see them getting any better torque to fuel economy ratios out of anything else they are doing. They could've just worked out a fuel system and spark control that would have gotten by stricter emissions. There'd be 30mpg slant trucks in production now--maybe not. Engines that run forever don't fit the business model of modern car manufacturers, and Mopar don't even offer vans anymore, apart from repackaged Mercedes.)

What were we talking about?
Author:  66aCUDA [ Fri Nov 07, 2008 5:22 am ]
Post subject: 
Do you have a spare LB module? I would think it would be neat to at least open it up and see what all is in there. I know electrolitic caps. tend to dry out and go open. this is just and example. I routinely repair old electronics this way.
If you need an old LB Module to play with PM me. I cant vouch for it working but thats half the chalenge.
Frank
Author:  Matt Cramer [ Fri Nov 07, 2008 7:47 am ]
Post subject: 
I think part of the reason you don't see many people trying to alter the Lean Burn system is the complexity involved in tuning a programmable electronic ignition. My turbo buildup is one I already intended to dial in on a chassis dyno, so it doesn't really bother me, but you will want to plan on doing something like that to get your spark in tune. By contrast, the older distributors are something you can often get tweaked at a dragstrip test & tune night.

The other reason you seldom see anyone trying to hack a Lean Burn ECU is that there's a fairly small amount you could gain from this, and it's not likely you would see the reliability get any better.

I haven't cut a Lean Burn box open, but my guess is it's a digital system with the advance curve stored in an EPROM chip. Usually with something this complicated you would have to reverse engineer the contents of the box, or design a programmable ignition controller from scratch. It is possible to build a Megasquirt to function as purely an ignition controller and make it work with the stock sensors if you don't feel like designing your own PCB for a stand alone ignition controller.

The idea about using an Apex'i was kind of an intellectual exercise in how manipulating a Lean Burn might be theoretically possible, although not necessarily practical. It's hard enough to find information about using a Super AFC on domestic fuel injected cars.
Author:  Ed Mullen [ Fri Nov 07, 2008 11:50 am ]
Post subject: 
I looked into the MSD programable ignition. Seems like a semi-viable option (barring the $400+ pricetag).

It wouldn't address the other roles of the ESA (upstream downstream air and EGR).

I suppose the ported switch for the purge canister could be used to operate EGR as well (I've found vacuum operated switches--i.e. electrical switches, not valves-- that are prohibitively expensive. I could very easily build one using the servo of a vacuum operated heater valve from the JY), or repalce the ported switch with a 3-inlet one, bypass the EGR solenoid and pull a hose from the carb and attach to the third inlet.

The upstream/downstream soleinod could operate via toggle switch. Only does stuff at inspection anyway.

Given the fact that I can buy a pile of used ESAs for $400, I'm not going to seriously consider that option.

I guess if I get a FSM, make sure all the sensors are working (all 3 of them) within spec, or replace them, I can keep the LB going.

I should probably start stockpiling used ESAs and, expanding upon 66aCUDA's suggestion, check for open caps, burnt resistors, bad soldering etc.

I know with Bosch stuff, it's almost never the chips gone bad. It's the stuff that costs $0.10 form Mouser.com (or $1.09 form Radio Shack), or degradation of solder over time.

Even in the case of blown chips, there are more than enough cores to go around with EI conversion so popular. (just need to start rescuing them before they all get tossed).
Page 1 of 1 All times are UTC-08:00
Powered by phpBB® Forum Software © phpBB Limited
https://www.phpbb.com/