IBT-AFR table.

[Trump]

I am attempting to tune a multi TB 4 cylinder car in IBT mode. Car seems to be going OK but I am having trouble coming to grips with the AFR chart in IBT mode. Road test utilizing TS for auto tune. Log taken at the same time shows the target AFR not showing any resemblance to the AFR table set up in the tune.
What is the relationship between the AFR chart and the VE table in IBT mode?

[shauer]

I cannot open up your files right now so this is just a shot in the dark.

Do you have your load axis for AFR set to the itb load? Or is it still set to a default of MAP?

When I was running ITB mode this messed me up once or twice. AFR table was still referencing MAP as load axis so nothing looked like what I was expecting.

hope this helps

[elutionsdesign]

It's not very far off, since you're running auto tune and have the EGO control turned off its difficult to tell how hard the auto tune is seeking your afr target. If you plot AFR target vs. actual AFR you can see it is quite close. Don't expect it to be dead on all the time. VEAL uses your AFR table as the target and makes changes in the VE table just like in SD mode.

VEAL can be run and works just fine with EGO control active, try that.

[Trump]

VEAL...sorry, can not find any ref to this. Do remember reading something on this but cant remember where.
After this run I checked the plugs and they were white to very light tan.
I am running with both the primary fuel and ignition load set IBT. Should I go bake to setting these back to SD.
The engine was running a single TB and running in SD mode. I started with the same msq modified to IBT when I fitted multi TBs so was using the same tune tables.
Remember, this engine is a 1950's design, not as old as me but still an old unit so the combustion is not as efficient as latter units.

[Trump]

Ooooppsss. VEAL...VE Analyse Live. All these acronimes.

[wrenchdad]

OK veal is VE (fuel table) Analyze LIVE V-E-A-L, it's one of the tab screens of TS when you have the registered version, otherwise that screen is not active.

What the other poster is talking about is on the load column of your tables when looking at your tune in MegaLogViewer, if you right click on the load column, you can choose what MLV will use as a lead reference, default is MAP, which is not what you want to use with ITB mode.

Hope this helps, later wd

[Trump]

All my tables,AFR, Ign, and VE are set for IBT. Do not understand what load column you are referring to in MegaLog Viewer. I do not seem to be able to change any of the load columns in that screen. I have not been utilizing the VE Analyze in MV but using VEAL.

As the MAP goes to max with min TPS, should I assume that the engine is actually at full power for that RPM and as such set the AFR accordingly? How do you relate the Load column settings (in MAP) with TPS settings?

Looks like I have missed something fairly basic when I read the manual on this.

[elutionsdesign]

Your tables are set correctly for ITB mode and I'd leave it in ITB mode as it works really well. At least for the few ITB setups I've tuned.

The MAP/TPS load relationship is set using the ITB mode TPS switchpoint curve. Below that curve you're basically running in SD mode, above that curve you're basically running in Alpha-N or TPS mode. You want run SD up to about 90% MAP as the relationship between the fuel required and MAP is good up to that point, beyond that the "load" based on MAP has really poor resolution but the "load" based on TPS becomes very effective for determining fuel required. You can go into megalogviewer and plot these relationships, look for the "scatter plots" tab, and from that you can determine where MAP becomes a poor indicator of fueling and TPS or TP becomes better, then go back and set the %baro and TPS switchpoint stuff.

So the answer to your question, when MAP goes to max with min TPS, no. The engine is not at full power for that rpm, the load can increase say by going uphill and you'd need to open the throttle more to maintain rpm which won't change MAP very much at all (poor resolution) but TPS will increase (good resolution) and therefore your fueling needs increase. Did that help?

[Trump]

Thanks
I understand how the tables work in SD and Alfa/n. It is the IBT mode that I am having trouble with. In particular, what cell do I change once the TPS goes above the switch point?
Say, for example, RPM 2500, Map 90(switch point set at 88), TPS 18%. AFR is showing lean in the logs. What cell do I change in AFR or to correct this when using VEAL?
How do I read the chart once above the switch point? For info, my switch point is set at 88 as the on board MAP sensor reads low. I run some logs to set the IBT Load Switch Points chart and set the IBT Load at Switch Points to 50% as advised in this thread.
I think my tune is close in cruse and around town, it is the top end I am mainly concerned with. I am on the track in a couple of weeks and need to be reasonably sure I can get the AFR close at the top end. I cant get to that range on the road. I will use practice (two sessions) to get the tune checked with logs but need to know what to change if I need to. If it is showing lean or rich, what cells do I change?

I do appreciate your input, there is just something in the interpretation of the tables once past the switch point that I cant come to grips with.

[Trump]

Bingo.....I have been reading(again) the IBT Load Mode document from the MS3 list. It suddenly came to me and if I got it correct, it is really very simple. Why didn't I get it the first time?

The IBT Load switch Point chart sets the point of transition from SD to AN. The IBT Load at Switch point sets the cells on the tuning charts that represent the 0% to 100% for SD and AN of that particular column.

In my case, I have set the IBT Load at Switch Point to 50% across the table. Therefor the top 50% and bottom 50% of the VE/AFR/Timing tables represent the 0% and 100% of the two modes,AN and SD.

In the example I gave RPM 2500, TPS 18%, Map 90, and %baro Switch Point 88. The MAP of 90 is 16.6% of the column above the switch point for AN load (2 as a % of 12). With the IBT Load at Switch Point set to 50%, the cell that would be looked up on the tuning table would be 8% above the 50% line.

Did I get it correct?

[muythaibxr]

Once above the %baro switchpoint and the TPS switchpoint, the TPS alone sets the load. Oh, and it is ITB load mode not "IBT." Other than that you have things right.

[Trump]

Thanks for hanging in there. I think I am now on track.