Fuel Pumps, Fuel Pressure, and Frustration

[billr]

I'm confused, not seeing what you are talking about in that most recent log. The AFR never goes down to 13.5, and the VE is a steady 36, as it should be for the rpm and MAP per your table.

[ironwill11]

I'm confused, not seeing what you are talking about in that most recent log. The AFR never goes down to 13.5, and the VE is a steady 36, as it should be for the rpm and MAP per your table.

I have to take smaller logs, the forum does not allow you to upload them once they get too big. The tuning was done to get the afr to 13.5 in neutral, prior to putting it into gear (VE table needed 36). Then put it into gear and the tuning was done to get that to 13.5. Then I shifted back into neutral to make sure everything was good and at that point i started the most recent datalog (I would have logged the whole thing, but that would have taken several minutes which would have meant the log was too big). But you can see that when coming out of gear my afr wanted to stay in the low 14's.

I am not sure why it would be at 13.5 in neutral, then going back into neutral it was at 14. I was thinking that it has something to do with the large step between the two.

Will

[Six_Shooter]

To start with, every GM TBI I have checked pressure on will drop a few PSIG from cold to warm, the only exception has been my T-bucket, but it has a pump really designed for MPFI, and being an open engine car the TBI probably stays cooler than a vehicle that has an enclosed engine bay. I've never experienced any tuning issues from a couple or few PSIG drop off from cold to warm.

I'd also not completely trust that gauge. You're using a 100 PSIG gauge and most gauges (including the senders for electric gauges) are most accurate within the middle 3rd or so of the full sweep, so using 15 PSIG and below you're under that sweet spot range and the readings could be less accurate and show more drift than what is actually happening. I'd replace it with a 15 or 30 PSIG gauge.

Also why are you tuning such a rich idle? Any gasoline engine I've tuned I shoot for mid to high 14s at idle, as long as it's not a really rowdy engine, then maybe a little richer but still try for low 14s.

[ironwill11]

To start with, every GM TBI I have checked pressure on will drop a few PSIG from cold to warm, the only exception has been my T-bucket, but it has a pump really designed for MPFI, and being an open engine car the TBI probably stays cooler than a vehicle that has an enclosed engine bay. I've never experienced any tuning issues from a couple or few PSIG drop off from cold to warm.

I'd also not completely trust that gauge. You're using a 100 PSIG gauge and most gauges (including the senders for electric gauges) are most accurate within the middle 3rd or so of the full sweep, so using 15 PSIG and below you're under that sweet spot range and the readings could be less accurate and show more drift than what is actually happening. I'd replace it with a 15 or 30 PSIG gauge.

Also why are you tuning such a rich idle? Any gasoline engine I've tuned I shoot for mid to high 14s at idle, as long as it's not a really rowdy engine, then maybe a little richer but still try for low 14s.

Thank you.

I have been reading about using MPFI for a TBI GM engine but only saw a few people do it, and i really want to drive this vehicle and not experiment with it. Right now I do not have a hood on my engine which, but that is just because it is easier to work on while it sits in the garage. I also imagine that things might get a little screwy from heat soak on the intake air temp sensor after the hood gets mounted back on.

I was going to buy the 0-30 psi gauge but it was double the price and I wanted to hedge my bets incase I wanted to switch to another EFI down the road. I even asked the company about it and they assured me that they are all accurate throughout the whole range.

I am tuning to the 13.5 idle because I read in the megamanual (the only manual I knew about when I got my MSII finally put together), it stated that Throttle body injected motors like to run rich at idle around 13-13.5. Any information I came across on the web seemed to confirm that. So it was pretty arbitrarily decided.

Will

[Six_Shooter]

The idea that a TBI engine likes or needs to be tuned that rich sounds like lack of understanding of how an engine works, and/or other areas of the tune are severely lacking. Like I said before I've always been able to tune for mid to high 14's regardless of being TBI or MPFI, except for those that a more wild combination. The only reason I can think of to tune so rich is for keeping the intake port walls soaked in fuel to ensure a smooth idle, but even though it may be smooth doesn't mean that it's good. It's a waste of fuel to tune so rich IMO. I have used a rich idle for initial tuning and getting an engine to run on a first fire of a new EFI system, but I can typically reduce the idle AFR to what I stated above pretty quickly, like within a dozen or so minutes of initial fire and being warmed up.

There are some wall wetting parameters in the MSExtra code that you might want to explore if you find that a properly stoich AFR doesn't run quite as smooth as you'd like.

[ironwill11]

The idea that a TBI engine likes or needs to be tuned that rich sounds like lack of understanding of how an engine works, and/or other areas of the tune are severely lacking. Like I said before I've always been able to tune for mid to high 14's regardless of being TBI or MPFI, except for those that a more wild combination. The only reason I can think of to tune so rich is for keeping the intake port walls soaked in fuel to ensure a smooth idle, but even though it may be smooth doesn't mean that it's good. It's a waste of fuel to tune so rich IMO. I have used a rich idle for initial tuning and getting an engine to run on a first fire of a new EFI system, but I can typically reduce the idle AFR to what I stated above pretty quickly, like within a dozen or so minutes of initial fire and being warmed up.

There are some wall wetting parameters in the MSExtra code that you might want to explore if you find that a properly stoich AFR doesn't run quite as smooth as you'd like.

Would this be why the truck shakes more when the load goes up when I put it in gear no matter what afr it is at? Lack of wall wetting that is? I just assumed it was with my ve tune.

Will

[Six_Shooter]

I wouldn't say that that IS the reason, though it may contribute to that. There are many factors, both tune related and mechanical that could cause an engine to shake.

[ironwill11]

I wouldn't say that that IS teh reason, though it may contribute to that. There are many factors, both tune related and mechanical that could cause an engine to shake.

I was just thinking something like that because when it is in neutral at idle it purrs nicely.

Will

[billr]

Perhaps it would help if you identify at what time periods in the log it is in N and when it is in P; I'm never quite sure when I look at them.

[ironwill11]

Perhaps it would help if you identify at what time periods in the log it is in N and when it is in P; I'm never quite sure when I look at them.

That is a very good point, especially now the iac is working properly. I will take a better log and make some notes about it.

Will

[billr]

Be sure to identify (or post) the applicable MSQ.

[turbo conversion]

I have a question for you, before you converted to MS did you have a consistent stable smooth idle?

David

[ironwill11]

I have a question for you, before you converted to MS did you have a consistent stable smooth idle?

David

Hello,

Sorry I was away for a while my mother is ill.

No I did not have a consistent stable smooth idle before having MS. I tracked down issues for the idle problems for over 2 years too which I found many people with GM TBI have them and no one had a fix for it (people actually replaced their engines because they could not figure it out). Many people claimed it was a vacuum leak, but no one ever got a fix for it (my MAP sensor says I am pretty steady). In my research I stumbled upon MS and DIYautotune. I contacted them and advised of my issue and they suggested it would help. That being said, my engine idles and runs infinitely better with MS then it did prior to converting to MS.

If you are interested in more back story:
I did an engine swap and ran very minimal sensors (never had and O2 sensor until MS). It ran like that for a while until I broke the truck. Then it was parked for a while and I when I started it up, it had a bad idle hunt. If you unplugged the vacuum or electric to the MAP sensor (introduce a vacuum leak) the idle would straighten out and run smooth but if you touched the gas it would drop to its knees (as my dad would describe it). Got it to a mechanic friend I we knew and after a couple days he got it running and stated that he just reset the map sensor. We don't know what he did but eventually he dissappeared. It was parked for a while again and when i started it back up it had the same idle hunt. I researched this for two years with not a lot of luck. I got the MS and started hooking it up and someone on the forum tunerpro (GM tuning forum) stated that he probably reset the IAC. Since then I have been making progress with the MS and getting close to having it running.

Will

[Six_Shooter]

So what is the application/vehicle exactly? The fact that you say you never had an O2 makes me think this was some previous half done conversion. Other than export vehicles to countries that only had lead at the time that TBI was used and MAYBE a couple heavy vehicle applications, all GM TBI vehicles had an O2 sensor.

What are we calling "idle hunt"? 25 RPM, 100 RPM? 400 RPM? What RPM are you targeting for idle RPM? I have yet to have an engine that is TBI or MPFI idle steady at one RPM, unless it was ridiculously high, like 1200 RPM on a nearly stock engine and even then it would have about 25 RPM "hunt". I typically see about 75 RPM on TBI equipped engines that I try to get an idle below about 700 RPM (fairly stock engines). Engines that have fairly large lumpy cams and long strokes tend to need an idle of about 800 to 900 RPM for most of the ones I've done. One of a friend's needs about 1000 RPM, but it has huge ported heads, huge cam that barely pulls 10 in/hg and is fairly large displacement wise.

[ironwill11]

So what is the application/vehicle exactly? The fact that you say you never had an O2 makes me think this was some previous half done conversion. Other than export vehicles to countries that only had lead at the time that TBI was used and MAYBE a couple heavy vehicle applications, all GM TBI vehicles had an O2 sensor.

What are we calling "idle hunt"? 25 RPM, 100 RPM? 400 RPM? What RPM are you targeting for idle RPM? I have yet to have an engine that is TBI or MPFI idle steady at one RPM, unless it was ridiculously high, like 1200 RPM on a nearly stock engine and even then it would have about 25 RPM "hunt". I typically see about 75 RPM on TBI equipped engines that I try to get an idle below about 700 RPM (fairly stock engines). Engines that have fairly large lumpy cams and long strokes tend to need an idle of about 800 to 900 RPM for most of the ones I've done. One of a friend's needs about 1000 RPM, but it has huge ported heads, huge cam that barely pulls 10 in/hg and is fairly large displacement wise.

Half done? Yeah, I guess you can say that, my dad and I were the ones that did the conversion. I got a 4.3 TBI from a S-10 Blazer from a bone yard. We put it in a Suzuki Samurai. It was my first one. I bought a wiring harness from painless wiring harness. I had did not have a clear idea on what O2 sensors did so I excluded it (as I was told to do by a friend who did the same engine conversion). We actually went out of our way to create a circuit to give the ecu the voltage it wanted to see to trick it into thinking the O2 sensor was there. Yeah now I learned about them I realize how ridiculous that was (there wasn't a lot of info about this on the web back then). When the engine ran well it idled around 675 rpm which is why I was shooting for that as my target idle. When it hunted it would bounce between 350 (almost stalling) and 1500 rpm.

Will

[Six_Shooter]

So it's still the 4.3 in the Samurai?

Bouncing like that is usually the sign of the throttle blades being too closed and the ECU going into "stall saver" mode (at least that's what GM ECMs do), which will usually caused that overshoot. It could also be that the IAC is getting lazy and when it is commanded to move it doesn't respond as quickly as it should and the ECU over compensates by commanding more to be added or taken away.

Have you tried to set the idle with the IAC disconnected and closed? You can use the IAC test mode to close it, then unplug it and set the idle via the throttle stop screw.

[ironwill11]

Be sure to identify (or post) the applicable MSQ.

I was able to get back and collect some data tonight and this is the first log that i took:

2017-05-12_21.20.31_Shifting.msl

The datalog starts with the trans in neutral (it did not seem to want to get down to the target idle but I think that is because the IAC would not go below 20 steps)
9 seconds it gets shifted into "drive", it dips down and then slowly comes back up to around the target at 29.092 seconds.
I shift back into neutral at 33.197 seconds
It gets back to the target idle around 47.761 seconds
I shift back into "drive" at 58.443
It starts to recover at 59.037 seconds and gets back to the target at 77.999 seconds.

The AFR seemed to be responding and staying in range, just idles rougher in gear then in neutral

This is the MSQ that I have been using:

2017-05-12_23.54.14._Shifting.msq

This is a second datalog that I did to duplicate the results:

2017-05-12_21.24.22_shifting2.msl

Will

[slow_hemi6]

When you shift into gear the MAP goes from 28kpa to 42kpa. Your spark table is pulling about 0.5 degrees of timing out when this happens. You actually want the opposite, try adding 2 degrees of advance in your 35,40 & 45kpa (701rpm) cells.

[turbo conversion]

Have you done a compression test to make sure the cylinders are balanced?

If you have a cylinder imbalance you will never achieve a smooth idle.

David

[ironwill11]

So it's still the 4.3 in the Samurai?

Bouncing like that is usually the sign of the throttle blades being too closed and the ECU going into "stall saver" mode (at least that's what GM ECMs do), which will usually caused that overshoot. It could also be that the IAC is getting lazy and when it is commanded to move it doesn't respond as quickly as it should and the ECU over compensates by commanding more to be added or taken away.

Have you tried to set the idle with the IAC disconnected and closed? You can use the IAC test mode to close it, then unplug it and set the idle via the throttle stop screw.

Yes, it is still the 4.3 in the Samurai. If it was the throttle blades I don't understand why it would change from just sitting for a while. I did not test the IAC, I only learned about that test after I cut out the GM ECU and wired up the MS. However, I have no big idle hunt with MS. I do watch the steps in the closed loop mode and the IAC does move around a little but it is relatively stable.

What kind of idle would I be looking for with the setting the stop screw. I would imagine that it should be lower then the idle with the IAC open so it has room to move around?

Will