Megasquirt tuning guidance needed

Application: ms2, 3.57. Bought version of tunerstudio

Mopar small block 5 speed, batch fire fuel only 

What i want to work on:

Low speed driving. Like 25mph and under, crawling in gear through the parking lot. Bucks and jerks like a bronco. 

Cruise fuel: it sucks gas at cruis, and just doesn't seem to run right.

Ive been doing autotune. Its drivable and pretty consistent. 

However, all me air fuel ratio targets are set to 14.7 across the board. Im pretty sure its not right. 

So, where do i start, and what should I change? Give it to me in simple terms. I REALLY struggle with this stuff. 

For the bucks and jerks, make sure you're not cycling in and out of overrun fuel cut. I've seen that pretty often.

With the cruising, if you have a wideband and are actually hitting that 14.7 target, the issue may be your timing instead of fuel.

Full throttle would typically target around 13.2 or so for a naturally aspirated motor.

If you can post up a copy of your tune and a data log, that would give me a bit more to go on.

Wideband or narrowband o2? I am by no means an expert here but that seems a relevant question. 

I agree your target af seems wrong. Full throttle should be 12-12.5 and cruise (part throttle) should be up higher than 14.7.

Do you know what the autotune does? It may only be setting fuel trims in order to hit your af goals. So if you have it searching for 14.7 across the board, it's probably getting good at that but that's sort of the wrong goal.

Can you post your tune and a decently long datalog?

I have been setting up denser bins at the low end of the MAP scale so I can better refine the fueling there.  I loot at how much VE spread there is between cells, and adjust the resolution to make it less of a "jump."

You may also have your AE too coarse, and if your foot is herky-jerky because the car is herky-jerky, it only gets worse.

What's your AFR at cruise?  If it's an expected 14.7-ish, What is your timing at cruise? More timing will need less fuel. My 11:1 350 (granted, carb and HEI) is running about 44° at cruise.

Ill have to refresh myself on how to do a datalog. 

My best friend and i olan to do a bunch of driving around tomorrow after work to tweak things.

As far as timing: mechanical only. 12 initial, 38 all in by 3000 rpm

I have a wideband (spartan 2)

Autotune only tweaks injector to match the a/f called for in the table. So, if the a/f target is wrong, autotune will get it precisely wrong. 

Im not anywhere near my laptop to pst a copy of my tune (which im not sure how to do here anyway)

Honestly, I never go leaner than 14.5:1 for for cruise areas(anything leaner and it likes to buck, at least when timing is above 30 degrees) and richen it up to 13.2:1 for acceleration in a NA car(12.5:1 for forced induction). As far as fuel consumption goes, if its sucking more fuel than when it was carbed, that means almost certainly that the o2 sensor isnt reading right...I am not familiar with the Spartan 2 wideband, but the Innovate sensors I usually run do require occasional calibration.

Yeah, your engine may not be thrilled with running stoich under cruise.  Try changing your targets a touch richer and see if it improves.

Carburetors have much better atomization and the fuel "timing" is consistent cylinder to cylinder.  Batch fire may not give you the best results.

My miata is okay in the 15's for cruise, LS engines will happily run even leaner. All depends on the engine.

But yes, I would make sure fuel overrun is off and your accel enrichment isn't doing anything weird. Need a data log of it bucking. AFR of around 13:0 for 100kpa is standard. I run something similar to this below:

Just to make sure i understand right. Lower kpa number equals higher vacuum reading, right? And higher vacuum is less throttle, which is leaner mixture which is a numerically higher a/f ratio. Right?

In reply to Dusterbd13-michael :

Right.  The kpa is absolute pressure, so high vacuum is low kpa and atmospheric pressure (WOT) is around 90-100kpa depending on altitude

Ok. And 14.7 is ideal a/f. But 15ish for cruise is generally ok, and low 13s good for power. Right? 

See, we way the hell back at basics here. Told yall i ain't no good with this E36 M3.

Heres my map of air fuel targets. Seems like i could lean it out a bit!

What do i do hear for parking lot crawling?

Batch fire?  Like all 8 at once, or bank to bank?  

On that, have you made sure the "banks" make sense?  It's pretty easy to get them firing at the wrong time and they don't exactly make it into the chamber very well.

IIRC, Knurled had a good explanation of this issue on a V8 he was working on a few years ago.

In reply to alfadriver :

I think all 8 at once. 

For better dynamics, can I suggest two banks at a bare min?  8 twice makes for odd injection timing for transients.  

Even better would be 4 mini banks, or 8 sequential.

Im not set up for sequential to my knowledge. I know i didn't wire it for that ability. 

I will try changing the setting. Im not entirely sure why its like that.

How did you wire it?  Have a diagram?

Interesting to see someone else with similar and altogether different issues.  I have a little of the huck-a-buck going on my 190 now.  Orders better now than the first time it went on the road, but not quite dialed yet.  I am flying against the grain and not running autotune (didn't pay for it), and in fact not even closing the loop with the WBO2.  I'm datalogging constantly, then going back and analyzing the log, examining short periods of steady state (ish) RPM and MAP conditions, noting the AFR, and then adjusting the VE table that way.  AE is effectively off (just realized settings are such that it is never being triggered atm).  Overrun cutoff is off.  Once I get the VE table dialed in running open loop, then I'll enable closed loop. 

Sunday was the first day it left the garage, today I drove it like 80 miles.  Datalog from the middle 10 or so miles looked pretty good actually.  

Dusterbd, I'm curious how steady (for lack of a better word) your AFR is from the Spartan 2.  I have the same unit.  Mine is pretty good, but I'm still surprised at the relatively high time-constant that part of the equation seems to have.  But when I zoom in on a few seconds worth of data, everything looks nice and correlated, so I'm inclined to believe it. 

Also, I totally forgot about that squirts per cycle param.  I'll have to revisit that at some point. 

alfadriver said:

For better dynamics, can I suggest two banks at a bare min?  8 twice makes for odd injection timing for transients.  

Even better would be 4 mini banks, or 8 sequential.

With a distributor, the most that can be done is batch firing alternate sets of four, and you can't choose when they fire because there is no way to determine crank position.

And yes, batch firing a V6 with short straight runners, a large plenum, and Very Large Injectors that had to be set to 1 squirt/cycle (one injection every 720 degrees) made it run like a poorly running oddfire four.  I figure two cylinders' fuel was getting blown up into the plenum instead of getting to the cylinders.

I have a sneaking feeling that Chevy and Ford got away with batch fire on their early V8 efforts because they had 20-22" long runners.  The fuel wouldn't get blown up into the plenum.  The LT1s had short runners but they also had sequential (or at least semi sequential) injection.

alfadriver said:

How did you wire it?  Have a diagram?

Here you go!

So a question for the MS experts- for the same bank pins- (i'm going on the color that is used) can the pairs 32-33 and 34-35 separate their pairs to make it sequential for a 4 cyl?

And michael- do you know which cylinders are going to 32, 33, 34, and 35?  Or better, reverse that- what cylinders are each pin feeding (individually)?  Not knowing mopars, on top of that question, what's the firing order?

We will get this so at least the timing isnt' the problem.  So when you go after the base and transient fuel, it will be more effective.

In reply to alfadriver :

The old style (non-Pro) units would double up the pins for current handling with the small pins in the DB37 connector.  If you wanted to separate them, it would require circuit board surgery.  It would be much easier to run an external fuel injector driver box (IIRC there was one that could do eight).

You'd still have to run some sort of cam position sensor, though.

In reply to Knurled. :

So for this MS2 version he's using, it's bank fire only?  Ok- that's good to know.

micheal- back to the what pins are feeding what cylinders?  To make sure they are at least partially in phase with each other.  

Once that's done, lets attack the specific tune.

In reply to alfadriver :

Without major disassembly, i cannot answer with certainty. However, i think i brike the two banks side to side like a chevy tpi system. 

Ok.  Well, at least change to a bank system, and two injections per cycle.  

It's been a long time, Knurled- have you done that with 4 injections per cycle on an MS?