Not quite sure I follow on what the LC1 will do without tuning and how it works with a computer programmed to function with a narrow band O2, is it taking a reading and sending the computer a fake signal to get the desired AFR?

I understand about the cat over temp, I am not too worried about the cats honestly, selling them will just about pay for a set of long tube headers...

I really wish I could afford tuning the truck, idle timing is not very steady and way too late and I suspect it could stand more advance everywhere, I would like to be able to use the shift button to lock it into a gear like the old "auto stick" would do, there are still plenty of un-nessacary down shifts. I could also just tell it to run 14.7 or even leaner until I hit WOT. I am also thinking about adding a bigger throttle body and modifying a vararam to feed more air at lower throttle angles so it don't downshift as much.

Yes, the LC1 wide-bands have an programmable output emulate a narrow-band. You can keep output strictly to emulate the narrow band signal or skew it in any way you want. including for e85 (would need a tune unless flexfuel). **The skew would only ever affect part throttle closed loop.** Somewhere more than part throttle the PCM uses tables and your going to get a programed/modeled AFR regardless. Data-logging from from the wideband will help you determine those points and actually tell you if its getting too lean/rich and where. At WOT in your combination, your PCM never did have any idea where AFR is and it wouldn't even if the engine was completely stock. Seriously. There are actually a couple outputs on the LC1, e.g. you can send an output to a gauge or datalogger like a diablo trinity while still using the narrow band emulator for the PCM.

You mentioned e85; you will need to do your own math to figure at what price-point that makes any sense and a wideband (unless your PCM is flexfuel compatible). Its not likely, but it might be if cheap enough.


My point is that the PCM literally has no idea they exist and will dump raw fuel anyways in certain situations...ALOT of fuel actually. Speaking of the catalytic, this is oversimplified but the downstream o2 sensor exists to know if the catalytic is 'working'. It tests for a difference in O2 from the upstream sensor before the catalytic vs after. The only way to get a less free o2 in that measurement is for there to be unburnt fuel going into the catalytic . Burning more of that fuel in the engine will get more MPG... and possibly higher egts



Seems like you spent plenty on whatever this experiment is. I'm just trying to enable you to finish it out.

I certainly apreciate the help, that LC1 sounds like a very fun and useful tool I had never heard of, I'll have to look into it. SO just to be clear, I could set it to something like 15. AFR and it will send a signal to the computer that would trick it into thinking 15.5 was actually 14.7 during closed loop?

WOT open loop I am sure it is trying to dump more fuel but like you said it is not able to tell anything and I am now pumping a lot more air through it also, it could actually be lean, I am sure it is a total crapshoot at this point but a tuner is what $1000 more plus paying someone that knows how to do it right and not a hack like me and the cost of the LC1... I am terrible with computer stuff, heck I can't even post a picture on moparts! I have been working on dodge stuff for well over 20 years, ASE master certified (for whatever thats worth) so I do have a basic Idea how the stuff works to diagnose cars but programming is beyond me.


As for cost, I don't really have much into this project, I bought an entire burned 2014 6.4 truck for $300 and sold the cats for more than that and also the trans. The truck I put it all in was dirt cheap because it had a blown up 5.7 in it and actually came with another super low miles complete 5.7 engine and new lifters, head bolts, gaskets and a ton of other stuff I have used to get customers vehicles fixed. I do all the work myself with my 9 kids. This is the only way a guy with 9 kids can accomplish stuff like this. I don't know a low buck way around the tuning issue besides what I've already done though I am going to look into the LC1 more now and see what I can do with it...

I just did a bit of a hypermiledge test with this truck, cruise set on 62 MPH on a 100 mile all flat ground round trip with nothing in the bed but 3 fishing poles AC cranking and got 22.7 MPG. Even my 318 2wd dakota won't do that, heck the closest I came was doing 65 MPH AC off and got about 17 MPG, even though I have to use premium in the giant 3/4 ton it is cheaper to operate... (I still prefer driving the dakota though).

What trans is behind your 6.4?

545rfe

I have been watching all your posts, also. Most of my trucks end up getting fixed and sold to support my hobby, my kids are all grown up. When I find a nice 2500 or 3500, then Id like to try the modified 6.4 in it. I am surprised the the 5.\7 PCM works, I always figured they would have pulled timing out of the bigger motor, as well as compression. Kind of like what they used to do on the 3 series truck motors from the 60's and 70's. As someone else mentioned, your an out of the box thinker and doer. Always need more of them. Jim.

The 6.4 is lower compression than the 5.7, that's why I put eagle heads on it, they take 10 CC out of the combustion chamber. Also both BGE and SRT8 6.4 cams has slightly more duration so I used a 5.7 cam to give it a tiny bit more time to push on the crank before the exhaust valve opens and the intake valve closes a tiny bit earlier to build even more cylinder pressure. Also the 6.4 uses EGR and the 5.7 don't so when you put a 6.4 in a 5.7 truck you get a free EGR delete.

I am going to sell this truck and build an engine for my newly aquired 2015, going to put in SRT8 pistons and zero deck em, BGE heads, 5.7 cam for real high cylinder pressure and hopefully keep it out of detonation. If I had access to e-85 I would run the SRT8 pistons, zero deck em and run the 5.7 cam and eagle heads for super high cylinder pressure. I think this would be hands down the cheapest way to run a 3/4 ton truck.

I just put a bid in on 4 RAM trucks today, One of the 2500's looks like a keeper, Ill be in touch. Jim.

Well I sold it and moving onto another one, a friend with a 2010 cummins borrowed it when his truck was down and just had to have it. For a replacement I bought a 2015 5.7 4 door 4x4 long bed, same basic truck but all stock with 5.7, drove it 400 miles this weekend and got 2 MPG less than the 6.4 truck did on a same trip and I was trying real hard to get good MPG. It did cost less to operate because it can run 87 octane but not a lot of difference. I was babying it to try and squeeze more MPG out of it and keep it from downshifting all the time... It had to down shift a ton more to get up hills and never had anywhere near the TQ the 6.4 had.

I have another 6.4 to build for this one and this looks like the recipe I will be following.

BGE heads shaved .025, I will do the same thing with the valves, mirror polish the entire exhaust valve head in the drill press, machine the margin on the intake valve to a very sharp edge to break up the fuel drops and minor porting on the heads along with porting the intake to more closely match the heads.

SRT8 short block

Can't decide on 5.7 or BGE cam, I feel the BGE cam will give me more power as the RPM go up but the 5.7 will give more MPG, also the switch from eagle to BGE heads will give it just a little more power as the RPM goes up and it will have a hair more compression... I thought about retarding the 5.7 cam a few degrees to give it just a tiny bit more time to push on the piston before the ex valve opens. Anyone know how much I can retard the cam timing before I get a computer code?


The other option I been considering is an eagle 5.7 with a piston swap to the early pistons, not gonna have the TQ of the 6.4 but could possibly do better MPG again with premium fuel only of course and I can easily sell the 6.4 to buy long tube headers and a vararam...

Thats funny, had a 4.7 Dakota that I liked for a daily beater, a fellow showed up today and had to have it. Gotta sell when the money is good. Picked up an Eco-Diesel to drive in the meantime. Keep up the posting. Jim.

Well I sold it, bought another 2015 with 5.7 long bed 4x4 4 door, same configuration same gear ratios (3.73) same trans and well it gets significantly worse MPG. On the same run with the cruise set at the same speed yesterday I was only able to manage 18MPG with this one so I got some work to do. I know it may be a tiny bit cheaper to operate this one as it runs perfect on low grade gas but the TQ has taken a huge hit with this 5.7. Even towing, or normal driving it is sucking more fuel than the 6.4 truck did with a lot less TQ.

I have another 6.4 just sitting around and like I mentioned before I am trying to decide exactly how to configure it, I am leaning toward SRT8 pistons, BGE heads and 5.7 cam, exhaust and intake... should give me a tiny bit more compression and a little more airflow thru the heads and extend the RPM up a tiny bit without hurting the bottom end TQ.

For better engine efficiency the “low hanging fruit” is to go from a factory air/fuel ratio of 14.7 to 20 to 1 or more.

That probably means an aftermarket fuel injection system or open source Megasquirt.

To convince yourself of this buy
an old carb single cylinder generator,
a wide range O2 sensor,
and run the generator engine at 14.7 and 20 using an electric air heater to load down the generator.

I know y’all talking truck but my 15 SRT 392 just got 28 mpg on a trip to Hilton head (75 mph) down and back. Lie guage was same as fuel-miles added up. The 4 cylinder drop out really makes a difference.

The best my 2020 T/A 392 has gotten was 22mpg, with the wife driving, that was in eco mode.

Just read a review of the 2024 model Honda Accord where it is mentioned that the I-4 gasoline engine static compression ratio is 13.9 to 1 and
-surprise- the air to fuel ratio is lean.

Not sure how Honda does that lean trick and still meets NOx standard.

I know people don't want to hear it but generally anything leaner than about 14.7 burns cooler not hotter.

When talking performance engines they tend to make best power around 12.5 or so because of the cooling effect of the extra fuel and yes running leaner than that gets hotter but only up to around stoich and equally important to hot rodders the 14.7 makes less power so running leaner than 12.5 gets hotter and makes less power so not a good idea under WOT. WOT at about 14.7 AFR is as hot as you can get the burn to be and that is when pistons melt not 17 to 1 AFR.


However part throttle is a different story at say 17 to 1 would run cooler than 14.7, it is just science that it would make less NOX. A lean mix vs stoich plus EGR will provide better odds of the fuel molecules combining with an oxygen molecule. EGR molecules just get in the way of a complete reaction. I think the reason companies have not typically done very lean mix instead of EGR is that it is not as easy to keep the cat lit and functioning properly with very lean mixtures VS richer with EGR. Maybe honda fingered out a way to clean up the lean mix in the exhaust with a new fangled cat or something.


If I was designing an engine from scratch I would shoot for something around 14 to compression with maybe a slightly retarded cam timing to bleed off just a tiny bit of the compression and allow for a longer push on the piston before releasing cylinder pressure into the exhaust and it would also have a much better expansion ratio. And yes I would run a very lean mix at part throttle.


I am curious do you know how lean they are claiming it is running? Also is it direct injected?

Yep, “way out there” on the lean graph a very high compression ratio does not knock
like this 2016 post shows in the Porsche graph by a guy named Gruden

https://board.moparts.org/ubbthreads/ubbthreads.php/topics/2182726/1994-5-9-magnum-upgrades.html

same graph shows that a “pig rich” mixture does not knock

another
look at how the NOx curve “brown line” drops with lean-ness to near zero percent just past 16.3
but the graph uses “percent”
which is way bigger than “parts per million”
and ppm would getting to EPA levels,
which legally are grams per mile.

On a side note,
notice the news articles
about Death Row executions
carried out “painlessly”
with pure nitrogen.