This is so much fun! this car is exactly what I was hoping for and I haven't really used it.. lol What a shame the season is coming to an end soon.

This is where it stands currently.

 

It's gotten a lot cooler around here. Almost time to put the car away for the winter. but I took a cruise in it today. I found the boost cutoff, which isn't set to high but, it answers a previously made question..... So, I know why it the car suddenly backfires and such. haha

Anyway, car runs decent, except upon initial throttle input the car hesitates quite bad, almost shuts off, then it'll rev up. It can be tricky to drive. It happens primarily on takeoff. I feel I have to let up on the pedal for engine to "catch" then I can let out clutch/give gas and drive away.

If someone has any suggestions or thoughts would be greatly appreciated.

 

Your AE settings are probably out-of-whack. You appear to be putting in too much fuel on light throttle applications, especially at low speeds / off-idle.

Looking at the logs, where the problem is occurring, your idle PW is around 1.7 ms, while your AE add is 3 ms.
Contrast with my setup, where my idle PW is around 2 ms, and in similar off-idle situations, my AE add is 1.2 ms.

Don't compare your numbers to mine directly, of course, but look at the relative numbers in each. I am adding 60% more fuel over idle in these situations, while you are adding 176% more fuel over idle in the same. (EDIT - Obviously I mean only for the brief duration that AE is active, of course, but that momentary surge of fuel could definitely cause what you are seeing.)

 

I'd try adding fuel to your VE table in the cells above idle. The cars leaning out to almost 18 AFR when you're letting the clutch out. I'd try adding 5-10% fuel in the 500-1500 RPM region from 40-60 KPA and see if that helps.

I'd also check your Accel Enrichment settings, because when AE does activate you're going down into the 10's which is also going to make the car unhappy. However, I'm also not seeing AE activate the whole time you're letting taking off.

Basically, fueling.

 

That's probably very true - my AE settings. The way you put it makes sense as I too notice the AFR's go down when I add throttle.

Thank you for the advice!


Ok so Add some fuel to the Fuel Table.. Here's the thing, wouldn't VEAL pick up on this and make the4 changes?



*** 2nd thing and this is a BIG one... What the hell I'm I actually looking for?? Like for real, I don't get what I really should be looking at. What I should be striving for on these datalogs.. I've watched many many videos and find that in the videos the data to be looked at, how it applies in real world, what should be done is not really explained and I must have missed what is the meat and potatoes of tuning an engine. Like what data tells me I've got a good tune or I'm headed that way or what tells me I'm going the opposite of a good tune. I THOUGHT it was all about the AFR's throughout the combination of engine loads and RPMs essentially. I know there's A F*&K ton that goes into it but what the hell.

I know I'm in way over my head but.. What info source have you all used that you feel does a great job explaining process? is it MS tuning guide - It was brutal for me to follow.

I want to learn I do, but me looking at the datalogs is like looking at hieroglyphics - does not compute

 

I'm just looking at the log and seeing that when you come out of idle you're going super lean and then super rich. I don't know for sure that's the issue, but that's what I would try if it were my car. I'd bet it's more of an issue with the AE causing the car to go super rich than the lean out, but I don't think either are helping. I also see that the cells right above idle are leaner than the idle cells. Usually people will recommend to make all your idle cells the same value (assuming the car hits multiple cells at idle, your car seems to stick to a single cell, at least in the log I looked at).

I'd bet if you stab the throttle at idle (without trying to take off) the car will bog. You might play around with that a bit.

Regarding what to look for, you said the car was stumbling when taking off so in my mind I'm scanning the logs for a time frame where the RPM is around 900 for 10 seconds or so and then paying attention to what's happening once the TPS begins to register some throttle input. After that I'm looking for something that seems abnormal. Drivability issues to me (assuming it's the tune and not an issue with the car) would usually get me looking at AFR and ignition. I don't know for sure that fueling is the issue, but it has some pretty major swings so that's where I'd start. ETA - Getting MLV tabs setup for different parts of the tune helps a lot. Mine's not setup properly right now, but having a graph that shows Target AFR vs Actual AFR, AE Activation or %, TPS, etc... is going to make looking at fueling way easier.

As far as sources, a lot of my learning has been reading posts on here, HPA videos/podcasts and just tinkering with my car and trying to fix issues like this one. I've had way too much fuel in boost, hit 10 AFR and seen the car bog. Hell, my car right now doesn't have the fuel dialed in quite right for E85 cold starts and will lean out and die if I don't let it warm up for 10-15 seconds (I've just been lazy about fixing it). For me it has been a lot of tinkering and tail chasing but I also enjoy it for the most part. Also keep the Dunning-Kruger effect in mind. I chime in a lot but I also know that I'm not nearly as qualified as some of the guys on here who tune different cars every week.

IMO A good tune is one where you can hand the keys to someone without having to give them a list of oddities about driving the car.

 

In that instance, which is a case where he wasn't coming on the throttle enough initially to trigger AE, and only part way into throttle application did AE kick in, after which is when it goes rich.

There are other instances where AE kicks in right away and AFR just dives. Again, that's a lot of extra fuel being added very suddenly at a small throttle input - look at the spikes in injector pulsewidth.







FWIW, I've just focused specifically on these coming-off-idle events - I'm not commenting on other aspects of the tune right now, just pointing out what immediately jumped out to me as suspect in these scenarios.

 

Right, if AE doesn't hit then it looks pretty lean and if/when AE does hit then it goes really rich. I drew an arrow in the screenshot to show that AE was kicking in which swung the AFR. Probably could've explained that a bit better.

I'm not used to looking at AE in terms of PW adder, but it definitely seems excessive, especially isolating it

 

Well, that's literally how it's configured on a MS2.
As I said earlier, converting the AE PW to a percentage of idle PW, he is adding 176%, while in my own tune I am adding 60% under similar conditions.

Yep, I was just pointing out that there were a number of other cases I saw where AE was jumping out at me straight away.

The lean spikes are obviously an issue as well. In looking at the same part of the log that you originally clipped, there's a couple of things I see:

• As you noted, VE is dropping despite an increase in both RPM and MAP
  • In the noted area, it drops from 38 at idle to 35 at the first minor peak at 1500 RPM
  • Both my own and known-good base tunes all have an increase between the equivalent cells
• CL idle close delay also seems high; it takes a long time to close after getting on the throttle
  • Probably not a huge deal, but CL idle settings might want to be looked at

Not related and not strictly a problem, but I was also surprised to see that overrun cut isn't enabled in the stretch preceding the region being discussed.

GBWhIteMIATA, can you post up the tune that goes with these logs (or at least your latest tune)?

 

Okay that gets the wheels turning a bit. I see what you're saying about just looking at these particular events (From idle to driving). I follow the AFRs spike LEAN, then drop dramatically RICH when AE kicks in. That box that denotes "TP AE". Admittingly, I didn't understand its importance/relevance. Very recently I turned on the "TPSdot uses %WOT" however I did not adjust the graph associated with it. Visually watching AFR gauge while driving I didn't see a change in behavior.

I haven't really done anything to the BASE TUNE other than drive around with VEAL. I got the tune from DITAUTOTUNE

 

Wait a minute... why is your req_fuel 6.6ms? It should be 4.4ms for 700cc injectors.

Given that, your AE settings look even more wrong now than they already were. You are adding a minimum of 3ms and a maximum of 9ms. That's really high given a proper req_fuel of 4.4ms.
I think the "gotcha" here is that you probably didn't adjust AE PW from the base tune you started with. The MS2 specifies AE in raw pulsewidth - it is not scaled according to req_fuel. So if you change injector sizes, you have to go and recalculate the AE PW manually.

You also have AE configured to use the TPS WOT curve, which makes it more sensitive at low throttle openings. I've never seen anybody use that feature, but maybe that was on your basemap as well. The only 94 basemap I have downloaded at the moment is Braineack's. My 99 basemap from DIY did not have the WOT curve enabled.

Other AE parameters look okay.

On CL idle, you do have a longer close delay than in Braineack's base map - yours is 3s versus his 2s. (My own is even less at just 1s.) Your close delay is also higher than I typically see looking at other tunes (3s vs 1s). And you have CL idle lockout enabled, which I believe will prevent CL idle from activating when you have the clutch in.

On your VE table, you are wasting the bottom row - there is absolutely no need to have a 5kPa row. It's not uncommon for 20kPa to be the lowest. The idle cells being in the 30s also makes sense now that I see that req_fuel is set too high - more typically, idle cells are in the 40s.

This VE table also doesn't match up with the logs - see here, where I loaded your last log and your tune. The log has a VE of 35 at this point, but you can see that your (current?) tune would have it around 44.



Also, your logs have negative times for some reason. This can be corrected within MLV, but it is odd and interferes with some MLV functionality if you don't fix it first.

As annoying as this sounds, I would suggest fixing your req_fuel and starting over with a fresh VE table - perhaps try Braineack's, as he does have a MS2 one for the NA8. (I had to convert his maps from the MS3 for mine when I started, because he doesn't have MS2 basemaps for NBs.)

 

Another tip related to VE Auto Tune is to lock out cells towards the bottom of your map. Once your idle cells are dialed in you might want to lock them out as well. When you're letting off the throttle and going into decel VEAL is pulling a lot of fuel to try and compensate. Probably not a huge deal since your table has cells for vacuum that won't be touched during cruise, but probably worth being aware of if nothing else. VEAL is good to get a map roughly dialed in, but it doesn't handle all situations. Its best used in steady state (IE cruise) where fueling is relatively stable.




And regarding req fuel, you should probably correct that, but I don't think it will cause any major issues if you don't update it. I'm also pretty sure if you do update it to 4.3 you can just highlight you're entire fuel table and scale/multiply by 0.66 (4.4/6.6) and essentially nothing should change.

Again, regarding the AE, if it were me and I was just playing around with it I'd probably take the car out with a table like the one below and see how it drives (especially stabbing the throttle). Capture some logs and report back. If the car begins to stumble when you stab the throttle then this is probably too conservative. Another option would be to raise the "Accel TPSDot Threshold" to prevent AE from activating when you're not being as aggressive with it. I think that would mask the problem more than fix it, but if AE is working well elsewhere then that might be an easier option. Based on the car being pegged rich when you're rev matching your downshifts (which I assume you feel), I'd probably focus on fixing the whole table.



Also, madmatter, I've actually never tune any megasquirts personally. I spent a good year or two working with a Speeduino which got me pretty familiar with Tuner Studio and MLV. The Speeduino (which maybe obviously has completely different menus/settings from megasquirt) can use either percentage or ms adder for accel enrichment. I can't actually remember what Link does right now since I don't think I've ever had to mess with it aside from maybe a tiny tweak when I first set it up.

Just my $0.02, again, I'm not a professional tuna by any means

 

I think it's true that req_fuel is only used by the MS2 in the main fueling equation, but there might be some other stuff that could get missed. I know that the MS3 does reference req_fuel elsewhere, so having it wrong there affects more than just your VE table. It certainly would be good to have the correct req_fuel so that your VE numbers are closer to actual VE and be used as points of comparison versus others - as it stands, it's rather far off and makes comparison more difficult.

The reason I was suggesting starting over with a fresh VE table versus scaling it is that there is definitely some quirkyness in the existing table, and it might actually lead to better results to start over. IIRC, GBWhIteMIATA was the one who had MAP sensor issues earlier in the year, so that (along with other tuning problems going along) could have skewed the table such that it would take longer to correct it rather than starting fresh. That is, the current map might be far enough out in some places that it would require more rounds of VEA(L) than just starting with a known good baseline.

Yep, for all of the commonality between MS2, MS3, and even Speeduino, there are still a lot of differences that can get overlooked when you are used to one specific platform.

The raw PW AE is actually specifically a MS2 thing, it's not even just a MS thing. The MS3 does it differently, and also offers alternative types of AE altogether.

 

Hey Madmatter thanks for having a look at this.. Ya know I've had many tune sources. when I went to trubokitty for Braineacks tune - I found I have already downloaded it and used it somewhere at some time. Just to be sure.. Question, are Braineacks tunes found at TRUBOKITTY.COM? when I did a google search that's what comes up. its spelled tRUbokitty not tURbokitty right? Also, will I have to rescale the AFR/VE tables for boost?

Unfortunately, I can't recall how or why the req fuel was set to 6.6.

Your right, I had MAP sensor issue, and as that was going(bad) the tuning got weirder and weirder as I went. That may have made for a hard start into understanding of tuning. IDK.


I've included the tune i found at trubokitty. Just want to be sure this is the source for Brianeacks tune as mentioned.

 

You too SimBa thanks for having a look at this as well. Also, thank you for the advice on VEAL usage. I won't rely on it so heavily. I've just been running it as a drive along hoping it's doing right by me. I desperately need more knowledge and understanding.

I agree, I'm just going to start fresh, new tune and what not.

 

Lastly I'm considering putting it away for the winter months next week.

Highs are in the 40's F(this week high of 44F) lows are getting close to the 20's F... Snow is around the corner, which where I'm at means...road salt.


***Would tuning now in cool temps have an affect on its tune in the summer?

 

Like I said, VEAL is great to get a rough shape of your fuel map dialed in. After that I usually switch over to looking through logs and noting areas where I'm off target. Another thing I picked up recently is considering the delay between where you're at in your VE table and when that gets to your O2 sensor. If your o2 sensor is pretty far away it will take some time (thinking like 0-1 second range) to get picked up by the sensor. That delay will change with RPM as the engine flows more/less exhaust. Something to keep in mind when making VE table changes. Basically the ECU might show you're in a certain cell of your VE table but if the RPM is changing quickly the AFR reading could be from a couple cells back. Probably not something you need to worry about much, but something to be aware of. You can actually play around with this by sitting at idle, adding 10% to your idle VE and watching how long it takes to get picked up by the O2 sensor.

When you tune in different temperatures you're going to start getting into your corrections (IAT corrections are the main one I'd think of). If those aren't dialed in properly then yes, you're probably going to chase your tail. Not to say you can't tune in the winter, but if you are going to then you'll probably want to zero out your correction tables, get everything dialed in, and then base your 0% corrections on the current temps. The main corrections I'd be thinking of there are IAT fuel correction, IAT ignition correction and IAT wastegate correction.

Also note that, at least in my experience, all of that is easier said than done. I often end up chasing my tail a bit with all of that. Once you have things dialed in pretty well then properly set up EGO/Closed Loop Lambda corrections can take care of a lot of the slop.

 

I started over with a tune from MSEXTRA for 94-95 w/ turbo. I scaled the VE table and AFR tables to my kpa's. I filled in the req'd info to get the car running.

Did not idle all that well. I drove to gas station put Seafoam then premium in the tank. Then, I drove to storage unit, the long way to try n get some of the treated fuel to the engine and parked the car.

Here is the current tune and a couple logs I took while driving along. because it was such a new tune I drove with VEAL and as smoothly as I could to get some idea of the fuel direction I should go etc.

IDK...

 

FWIW, I was saying to start over with a fresh VE table, not an entirely new tune. Just fix req_fuel, then import the VE table from a good basemap (rescaling it as necessary).

 

All good Mad.

I actually believe this would be a better base tune overall. This is specifically for a turbo. And previously I believe I may have blended a NA tune into my turbo.

True I had more time with the previous tune dialing in the idle but idk overall I wasn’t confident in the previous tune/setup.

so.. it’s done.