Tuning ITB Load curves

[robd]

Hi, I was just wondering the best way to tune the ITB Load curve for the 'ITB Load TPS Switchpoints'? I'm currently just using the defaults and I'm not sure if this is causing me issues with my VE table for areas where I'm ending up in the same cells at different TPS positions.

I've got another thread going here where at first I thought it was an issue with my TPS%, but now I'm wondering if it's actually my ITB Load TPS Switchpoints that are wrong!

Is it just a case of logging a full rev range run, like through 1st and 2nd gear and then review the logs to see at what TPS% the KPA is at 90 for certain RPM's and update the table. Also I read about ITB Load mode and it mentioned a %Baro Switchpoint, is this actually a setting somewhere or are the manuals just out of date and it's just based on the ITB Load TPS Switchpoints.

Also is there any need to change the ITB Load at TPS Switchpoints or is this best left as is?

Also another question, how is the Alpha-N area of the table calculated? So if my switchpoint for 2109rpm is 10.4% TPS, what happens when I'm at the same rpm but at 20% TPS?

Thanks in advance

[muythaibxr]

Have you read the manual page on the ITB load feature?

http://www.msextra.com/doc/ms3/ITB_Load_Mode.html

I think it should answer your questions, and if you don't think it does, we can fix that.

Ken

[robd]

Thanks very much for the reply Ken, I hadn't read that no but had read this which seems to cover most of it. The main thing I was struggling to get my head around was how it worked out the TPS change once you reached your Switchpoint, but I read the link you posted a few times last night and I finally got it I think.

So if I'm understanding this right, the ITB Load TPS Switchpoint should be the TPS% where you reach 90kpa. So this is saying, ok when I get to say 10% TPS I should also be at 90kpa, so I'm then switching to the Alpha-N area of the table.

Then the ITB Load at TPS Switchpoint is the partitioned VE table, so you're just saying I want this section for MAP based VE and this section for Alpha-N based VE. To get to each of these switchpoints it uses the previous table for when you hit the desired TPS%.

Now I kinda got that bit already, but what I was then struggling with was once it got the the Alpha-N area, how did it work out the difference. Which if I'm right, it's basically just a percent of the remaining VE area. So if at say 2109RPM my TPS% is 10.4 and the VE load area is 79.1. This means that if my TPS% was at say 50% at this point, it would be 50% of the difference in the remaining VE cells, which would put me at roughly 90 ITB Load. So basically it just divides the VE table above the switchpoint and the TPS% is the division of that area of the table.
Does that make sense?! lol I think I've got it anyway. I was previously thinking that say 50% at that same switchpoint would move you to a different switchpoint, but if the RPM was the same it wouldn't, it would just move you higher up the ITB Load table based on the TPS% which is worked out as a percent of the ITB Load after that switchpoint.

lol I know I've probably repeated myself like 10 times there, but hopefully I've got it right and maybe if I say/type it enough I'll get it right!!

Please don't tell me that's wrong now or my head might implode!! lol

Ok so the next question, not sure if you looked at my logs in that link I posted? But is there a best way to check your switchpoints? Like should I go through say 1st and 2nd gear from idle to redline but slowly increasing the throttle change, or can you just literally go WOT through a full rev range and you'd still get the same results to see where your kpa hits 90 at those RPM's to then set your switchpoints?

Also could incorrect switchpoints cause an issue where if say at 2900rpm with 13% TPS and at 75-80 ITB Load my AFR is at 14.9 which is correct, but then at the same RPM and Load my TPS% was 20 but my AFR's are then going into the high 15's and even high 16's?

Thanks very much.

[robd]

Ok so the next question, not sure if you looked at my logs in that link I posted? But is there a best way to check your switchpoints? Like should I go through say 1st and 2nd gear from idle to redline but slowly increasing the throttle change, or can you just literally go WOT through a full rev range and you'd still get the same results to see where your kpa hits 90 at those RPM's to then set your switchpoints?

Think I'm being stupid there, as if you went WOT throughout the entire rev range then it'd be showing up as 100% TPS at those switchpoints which would be no good. So I guess you do need to slowly go up the rev range to get the correct TPS% at 90kpa.

Still if you can give any feedback would be great and any thoughts on the lean issue would be great too.

[robd]

Thanks very much for the reply Ken, I hadn't read that no but had read this which seems
Ok so the next question, not sure if you looked at my logs in that link I posted? But is there a best way to check your switchpoints? Like should I go through say 1st and 2nd gear from idle to redline but slowly increasing the throttle change, or can you just literally go WOT through a full rev range and you'd still get the same results to see where your kpa hits 90 at those RPM's to then set your switchpoints?

Also could incorrect switchpoints cause an issue where if say at 2900rpm with 13% TPS and at 75-80 ITB Load my AFR is at 14.9 which is correct, but then at the same RPM and Load my TPS% was 20 but my AFR's are then going into the high 15's and even high 16's?

Thanks very much.

Anyone got any pearls of wisdom they could share with me for checking hte Switchpoints are correct please?

[muythaibxr]

Basically they should give you consistent tuning results. If they do not, then tune them until they do.

The other curve should just be set to give you the best tunability, and should be set based on personal preference.

[robd]

Ok, thanks again for the reply. I think from looking at my logs the 90kpa switchpoints may be lightly out, so I'm going to compare the last 4 days logs to check they're consistent and I'll try adjusting them and see if that helps.

Thanks very much.

[muythaibxr]

basically look for load to climb/fall smoothly in your datalogs. If it doesn't the switchpoint curve needs tuning most likely.

[robd]

Thanks very much, sounds like I'll have to get my log reading cap on then.

I've just put together a quick spreadsheet of data of every point in a few logs where I hit 90kpa and what the RPM, TPS% and Load was at that point. It looks like my curve does need adjustment as you said, however it also looks like some of the switchpoints are way off as well!

E.g. at 2109RPM my current TPS% switchpoint is at 10.4, however looking at my logs I've hit 90kpa at 9%TPS a little bit before this RPM, normally around 2050 and all the way up to 2500RPM the switchpoint appears to be 9%TPS at 90kpa!
Then at 3418RPM my current switchpoint is set to 15.8, however looking at a few logs, I'm hitting 90kpa at 11%TPS from about 3350RPM up to about 3600RPM.

Judging by this and the Loads I'm getting at those points, I think I'll need to drop my Switchpoint curve down a few % as well so I've got more cells in the Alpha-N area to give it some more wiggle room.

What do you reckon, do you think those numbers sound wacky or feasable?

I'm still wondering if maybe my TPS is a few % out as in my other post I don't see any TPS% change on very light throttle up to about 2000RPM ish when the engine's running. If this is the case when I'm moving, this will also be throwing my switchpoints out! Oi vay!!

[muythaibxr]

Nothing you have said there sounds wrong. The only way to tell for sure is to try it though.

As far as the TPS not changing, on my ITB setup, I can get the engine to rev slightly with no change registered by the TPS... In my case I think that's the nature of ITBs... they let a lot more air in with a much smaller throttle opening than normal TBs. In my case I can't drive without showing any TPS opening though, so I'm not sure if you're seeing what I'm describing.

Ken

[robd]

Thanks very much, that's good to hear, at least I know I'm not doing this all arse backwards!
I'll try changing the switchpoints and see what difference it makes and get some more logs for the higher up rpm.

That's a bit of a relief to be honest hearing you say that about the TPS, that sounds like mine, with engine off I can see TPS movement on the gauge, but with the engine on very slight movement of the throttle doesn't register anything. I'm 99.9% sure that I've always got a TPS reading when I'm driving the car though as you've described so that sounds good.

Brilliant, you've been a great help Ken, thanks very much, really appreciate it.

....off to play with my switchpoints and curve now and see what happens....

[robd]

Just one other thing Ken, I don't suppose you could check yours and tell me how much throttle movement you have before the TPS gauge shows movement could you? My idle is about 900rpm and I can very lightly rev up to 2000rpm before it shows any TPS movement on the gauge.

Thanks very much

[muythaibxr]

IIRC, I could only very slightly increase the revs before showing throttle movement... maybe 200-300 rpm. I can give it a shot somethime this weekend.

Ken

[robd]

If you could please that would be great.

[robd]

Any joy on testing your TPS% movement Ken?

[E4ODnut]

Robd,
If you aren't getting any change in TPS values at small throttle openings you might have to get creative and build yourself some progressive throttle linkage and move the TPS to the primary lever side. The stock throttle bodies on my Fords are progressive to effectively "gear down" the initial movement.

[muythaibxr]

I didn't have time last weekend, will try again Sunday.

Ken