MSD Atomic EFI: Tuning Tuning Tuning

[Flip]

Okay so the results of my highly scientific butt dyno tests are as follows;

First off still no change in hunting or miss.

So I fired it up let it idle a few minutes and hit the road. I drove down and then back up the hill to my house.

Then adjusted the power valve to 30% and repeated.

I noticed no real 'off the line' improvement.

Otherwise it felt pretty similar. But I did a little test where I was moving up hill at 50mph then kicked it in the guys and counted how long it took to get to 60, from the same location for both settings.

With the power valve at 20% it took 13 seconds to gain those 10mph.

With it set to 30 it only took 9-10ish

So there was a minor improvement but I really didn't feel it, I only counted it that one time.

I was tired (12 hour work day) so I parked it and retired for a cocktail and a cigar.

Yeah seat of the pants "rule of thumb" is, it takes 10% or more change to feel the difference. That's a pretty big jump. Your time test speaks more to the situation. As we suspected the engine can use more fuel, but needs it metered correctly based on function.

OK, lets have some fun...

Right now we are just looking for changes, good or bad. We are getting a feel for what your power train needs to have for optimum performance, and overall driveability. Positive results will come once we understand what your engine needs. So all this is just testing to get a target goal.

Bump your displacement up to 400ci. reset your Power valve to 25%, and idle stoich to 14. Let's see what that does.
This is going to be a global change. At this point we're only looking for an overall driveability/power change. We'll deal with the hunting after we achieve power, and driveability.
You may need to drive it for 20 or 30 minutes to get it to settle in from this change.

This change should add metered fueling across the board. This will indicate the effectiveness of where the WBO2 sensor is located in the exhaust, and if we have any issues we need to address with that before proceeding. We want to note the following:
1). Stumble - hesitation either from a stop, at cruise and at transition from cruise to power
2). Overall power increase/decrease
3). Idle quality, and idle stoich.
4). WOT (wide open throttle) heavy load stoich

Watch your stoich during these changes, and note how rich or lean it goes, and how fast the system responds to bring it back to requested stoich.

5). An injector code

[Dr. Marneaus]

Cool cool, sounds like a plan. I've got some driving to do this weekend out to the range, may go look at a canoe, etc, so I can certainly drive it through a variety of conditions.

For the record, do I need to be concerned with driving it during all of this? As mentioned everything feels more or less "fine" I just feel its not as good as it should be.

While doing all of this am I okay to put some miles and take some trips? I get that it may not be running as strong or efficiently as possible, but want to make sure I'm not harming anything by driving it in the meantime. I dont think we've seen anything that indicates a major issue thus far, have we? I had intended to take it a few hours up the highway next weekend. If i cant, it's whatever, but I dont want to do any harm.

[Dr. Marneaus]

Would fall flat on its face if you stabbed it from idle

gotcha. I've not had anything like that, and I've had no hesitation from stop or during transitions, etc. The only abnormality i have noticed is that it feel's somewhat weak, the hunting, and the miss.

[Flip]

Yep you are totally fine to drive it. The more you drive it, the more we learn.
If we get way out of whack, it will throw a code or you will hear a pinging, in which case you can just hit the reset, and re-enter the standard parameters.
We aren't doing anything radical enough to cause any issues. Our bump to 400ci is only about 11% global change. I'm being a bit conservative due to your altitude, heat and low humidity.
I *think* as we get close, I'm going to ask you to please bump your base timing up about 5*, but want to get some more fuel metering first.

[Flip]

I also encourage you to play around with it. It's way more simple than people think.
Just listen for pinging, watch your temps and watch for codes.
As you read through the tuning guide, and get an idea of what each function does, you'll get a great understanding of how they all work together. So in the future, as you make changes to the engine (cam, heads, intake, headers, etc. ), you can do your own tuning.

[Dr. Marneaus]

Thanks Scott and everybody else. You've all been invaluable in this process and I appreciate all the help! I'm already very happy with how much better this is than the carb so if we get it dialed in pretty well and it gets even better I'll be one happy camper!

[Flip]

Yes, a great collaborative effort! Which seems the norm on this forum. Very cool.
Thumbs up to all involved.

[Dr. Marneaus]

Okay. More butt dyno information! Adjusted to 400CID and 25% then drove about 60 miles over the course of roughly an hour and a half, with a cool down in the middle.

My initial thoughts were that it was a little bit better, kinda the same feeling as making the 30% adjustment before.

Everything seemed fine. No abnormal readings. On the plus side I was getting on and off the gas a lot during many different speeds and I never once had a backfire. It would occasionally backfire before when I let off the throttle quickly at highway speeds. Not very common tho.

I noticed at one light while I was idling that the AFR was in the mid 12's and would not come up to 14. It only happened that once though. Otherwise AFR Was dancing around where it
Needed to be, 14 at idle and cruise, and If I stomped it it would drop to about 10 for a split second, go back up close to 14, then within a second or two it would be in the mid/low 12's where it should be for WOT.

I performed my same hit the gas and count test, and this time it produced results similar to the 30% enrichment test. It took about 8-9 seconds to climb from 50 to 60 on the hill by my House.

But as mentioned before, I couldn't really feel any major difference in the seat of pants, but it was running well. I guess it felt a little stronger same as back when I had the fuel pressure high. When cruising it didn't take as much pedal to get the tuck to pull. But that was minimal and could be my imagination.

[Dr. Marneaus]

Drove it a bit more noticed on hot starts there were a few occasions where it would want to stall if I stabbed the gas from an idle or stop. AFR would shoot up then drop wallow to compensate.

[Flip]

From what you describe based on the changes, we needed more fuel all around, except at tip-in. Now we have a bit much, but you still have the distributor to install, and bumping up the base timing will compensate a bit as well.

When you redo the exhaust system, it would be good to move the WBO2 up closer to the manifold (as per the instructions).
Basically we can get it "pretty good" as is, but it's still going to have a hick-up every now and then.

What happened with IAC numbers when you jumped up to 400ci?
You may be able to tweak that a bit more, but wait until the end when everything else is set.

So based on this info, it sounds like time to get things dialed in as best we can.

If you have time, install your new distributor and bump the base timing about 5*.
Listen for three things once you've done this:
1). Kick back against the starter when cold
2). Pinging under light load cruise (most noticeable if you aren't running EGR)
2). Pinging under heavy load.

If you don't get any of those, then we are happy campers.

At that point drive it for a bit, if you still get that stumble at tip-in, pull out about 5% pump squirt. If that doesn't resolve the stumble, drop down to about 380ci - 390ci with all other tuning at stock.

Let's see what this does. At the end of this, we are looking for better driveability, and power, and I think there will still be room to tweak for better. We haven't addressed hunting yet, although I am expecting a slight improvement mostly from the HEI, and advanced timing.

[babywag]

I would agree, but would just reset CID to 360, and bump fuel pressure up 5psi.
Increasing the CID depending on their programming might cause other issues.
Depends on how they calculate fuel needed, and generate the fuel map.
Telling it you have a 400 vs. a 360 will generate a fuel map that probably wouldn't be ideal.
Too much fuel could make it fall on it's face @ high load.

That is why the GM TBI systems are nice, you can datalog and see what is going on, then you can modify the fuel table, and other parameters.
These so called "self learning", or "self tuning" systems are cool, but have limitations.
Without good data that you can look @ and see what is going on it's a best guess, trial and error, kind of thing unless you add a datalog device.

[Dr. Marneaus]

The IAC is still correct once warmed up and running the 400CID programming. Put the truck in gear, and it hovers around 5-10 counts.

wont have time to install the HEI for a bit, because I need to wire in relays and everything, and I'm intending to take a camping trip this weekend. Will put a few hundred miles on it probably with the current settings to see how it runs and if the stumble still exists.

It was about 45* this morning when i fired it up to take to work (I'm the only one at the office today) and it hunted less...and seemed to run smoother right off the bat. It ran NICE all the way to work. when sitting at the off-ramp it took maybe 30 seconds for the miss to appear, but before that it was purring like a kitten and aside from the miss everything felt a lot more "calm" if that makes any sense?

[FSJ Guy]

X2 (or 3?) on resetting the CID to 360 and using other parameters (fuel pressure, etc) to adjust fueling.

Looks like your'e getting closer, though!

[Dr. Marneaus]

Also, my o2 sensor is only like 3.5"-4" away from the manifold....which is within what the instructions said. The book says "2-4"

[babywag]

Also, my o2 sensor is only like 3.5"-4" away from the manifold....which is within what the instructions said. The book says "2-4"

Your wbo2 location is fine, it's heated and you're not running headers. Should be no issue running it there.
If your engine wants more fuel, let it have it, bump pressure up in small increments until you are happy with how it runs.

[Flip]

The IAC is still correct once warmed up and running the 400CID programming. Put the truck in gear, and it hovers around 5-10 counts.

wont have time to install the HEI for a bit, because I need to wire in relays and everything, and I'm intending to take a camping trip this weekend. Will put a few hundred miles on it probably with the current settings to see how it runs and if the stumble still exists.

It was about 45* this morning when i fired it up to take to work (I'm the only one at the office today) and it hunted less...and seemed to run smoother right off the bat. It ran NICE all the way to work. when sitting at the off-ramp it took maybe 30 seconds for the miss to appear, but before that it was purring like a kitten and aside from the miss everything felt a lot more "calm" if that makes any sense?

Good news.
If the stumble comes back,reduce pump squirt 5%. If it still stumbles, come back to about 380ci. Keep pressure where it is. There is a very important reason I recommended to drop pressure, and increase engine displacement. I'll explain later, when I have more time.
HEI should help quite a bit with the miss at idle. Will also help with hunting, along with the timing advance.

[Dr. Marneaus]

Okay. So this weekend turned into a lot more driving than I anticipated!

Spark notes: 350 miles. No real issues. 12.9mpg

Longer version: drove from Reno through Susanville up to crater lake CA, then to Lassen then to Burney. 350 miles including a few climbs of 2000-3000+ feet, 25 miles of steep washboard roads, a bunch of highway at 55-65mph, slow in town driving, etc. Pretty much covered it all.

The only actual hiccup I would say was a hot start stall. Had the truck parked for about 20 min, got back in fired it up drove about 50 Yards came to a slow down and it shut off on Me fired up instantly and didn't have any other issues.

Interesting note: the jeep feels more 'calm' ever since adjusting to 400 Cid. Like, not necessarily more smooth....but cruising along at any speed it feels more calm. I don't know how else to explain it.

Also I probably had the coldest cold start yet since installing it. It was about 45 out and the display said ECT was 55*. It fired right up and had hardly any hunting. It kept high idle for maybe 5 seconds came down idled a little rough then went back up. At no point since adjusting to the higher displacement has it almost stalled or actually stalled on start up like it has done before. I used to have to use my foot to keep it running on a cold start but that seems gone now. It does still drop down once or twice and then idle fine.

Anyway, it so pulled well on grades and whatnot. At no point did it feel as weak as it did on my last trip.

So....positive results I'd say?

[Dr. Marneaus]

Oh yeah and average trip mileage was 12.88mpg.

The last leg from susanville to Reno I got like 13.8 so that's all awesome as well

[Flip]

Sounds like a great weekend, and some good news.
Your "calm" explanation is a good driveability explanation. The engine was running harsh due to active radical combustion. It's not uncommon in older engine designs when the overall stoichiometry is affected.
Basically you've increased fueling across the spectrum to better match the engine needs, while maintaining a refined concise amount of fuel per injection event with the lower pressure. This helps the system maintain a more consistent wetness in the intake runners. So overall it makes a more consistent burn in the cylinders under all conditions.

If it were me, I'd let it run as is, until after you install the HEI. See how the HEI affects things, then if needed make some final tweaks.
I think the timing control, when you get to that point, will smooth out any remaining hunting when cold, and intermittent stalling issues.

[Dr. Marneaus]

Wife is gone this weekend so that means I have as much time to dedicate to the jeep as I want and dont have to worry about taking time for things like sleeping and eating. Hoping to wire up and stick in the HEI this weekend