"Differential" ITB mode

Testing and development of Megasquirt 3

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Arowana
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Joined: Fri May 01, 2015 2:20 am

"Differential" ITB mode

Post by Arowana »

I have some ideas for running boost with itb mode, but first some background information:

I have a 85 Toyota mr2 mka1 (aw11) with a 4age 20v blacktop + 6 speed swap. Its running MS3X fully sequential using yaris COPS. I ran like this whole last summer and everything worked great.
I'm now in the progress of supercharging the same engine, using a sc14 roots supercharger from a Toyota previa. Due to the high compression (11:1) I will be running E85 to have a fighting chance.

I really liked the way that ITB mode worked and I would like to use it for boost also.

Right now ITB mode is dual mode pure alpha-n and % baro

I intend to run 2 map sensors one pre throttles and one post throttles, the pre throttle will be "baro".
because the speed density part of itb mode is referenced to baro it will be working against the pressure differential of the throttles regardless of plenum pressure (if plenum pressure is hoked up to baro that is)

The itb table will be tuned as good as posible with the supercharger disconected.

for the second table I will be runing speed density, bu I will modify the MS3 source to use baro instead of map:
ms3_misc.c line 2703

Code: Select all

outpc.fuelload2 = tmp1;

to

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outpc.fuelload2 = outpc.baro;
then will change the folowing in ms3_inj.c

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 if (ram4.loadopts & 0x4) { // multiply map
                inj_load1 = outpc.map;
            } else {
                inj_load1 = 1000;          // normalizes to ~1 when divide by baro
            }
            inj_divider1 = outpc.baro;
to

Code: Select all

 if (ram4.loadopts & 0x4) { // multiply map
                inj_load1 = outpc.map;
            } else {
                inj_load1 = 1000;          // normalizes to ~1 when divide by baro
            }
            inj_divider1 = [b]1000[/b];
to make algorithm 1 non baro dependant.

and

Code: Select all

 } else {
                if (ram4.loadopts & 0x20) { // multiply map (2nd)
                    inj_load2 = outpc.map;
                } else {
                    inj_load2 = 1000;          // normalizes to ~1 when divide by baro
                }
                inj_divider2 = outpc.baro;
            }
to

Code: Select all

 } else {
                if (ram4.loadopts & 0x20) { // multiply map (2nd)
                    inj_load2 = outpc.map;
                } else {
                    inj_load2 = outpc.baro;          // normalizes to ~1 when divide by baro
                }
                inj_divider2 = 1000;
            }
to make algorith 2 to "multiply baro" to that when table 2 is all 100% it will be tuned somewhat right.
then I just change table2 to compensate for changes in ve with boost (it should stay very close to 100 all the way i hope)

Is my theory sound?

Do I need to change some more outpc.baro to 1000 in the source to make it work?
or is there an easier way?

I guess it would be possible to add the pre throttle map sensor as a generic sensor and modify the source to use that.
Then I wouldn't brake any calculations were the baro sensor is involved. How can I access a generic sensor in the code?

Any input appreciated!
suberimakuri
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Re: "Differential" ITB mode

Post by suberimakuri »

Interesting idea. I may not have fully grasped it and haven't tuned ITB mode before.
Would things get interesting with boost?
As 100kpa is not full load, and a typical 80kpa or whatever ITB mode switch point may not correlate like it does NA, at least when rpm high enough to create boost.

Based on weeblekiller's posts on here regarding turbo throttle setups...
I've done some preliminary 4age tuning with single throttle turbo setup running SD VE1 (multiply map off and use this table for boost VE changes) and AN VE2 for main 'load' map.
It works fine just miss out on SD bonus below <80kpa.
Could in theory do <100kpa adjustments in VE1 but I haven't bothered.

Am changing to 20v head soon with throttles, hence the experiment.
Have another car with 20v NA on AN so can use throttle map from that as base for turbo setup.

Also i realise normally for NA, throttles map better with AN then single throttle does with AN. Single better SD.
Weeblekiller mentioned map fluctuations post throttles on boost so switched to pre throttle map sensing.
As I have single throttle with standard 16v plenum I haven't noticed any issue with post throttles map pickup location.

Keen to see how you get on!
Arowana
MS/Extra Newbie
Posts: 7
Joined: Fri May 01, 2015 2:20 am

Re: "Differential" ITB mode

Post by Arowana »

I have tested the mods and it looks good so far!

I auto tuned VE1 with the bypass valve open and then activated boost control and auto tuned VE2.
Its not nearly finished yet, but its proof of concept at least!

Image


Rant/Philosophy/Theory
It seams that the efficiency table (table 2) needs larger values for more boost.
But boost is already accounted for in the algorithm, so it must mean that the engine breaths more efficiently with boost.

Could this be because the plenum is at 8 psi and the exhaust is still at atmospheric? So air flows easier trough the engine?
If so, would it be the opposite for a turbo charged car? Air would flow less efficient trough the engine as exhaust back pressure rises more than boost?

Food for thought!
suberimakuri
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Re: "Differential" ITB mode

Post by suberimakuri »

Interesting results. Did you take a log?
I take it your TPS switch point was unchanged?
Normally adding boost to a motor means that effective WOT changes, and small vs big turbos or superchargers affect it again. The supercharger especially might bring in boost down low so the need to have a SD/AN switch point is lessened.. does this make sense?
How low (rpm) do you get boost?

For fun, have you tried running SD only on this motor now that it's super charged?

For turbo setups, it's common for VE values higher than 100 to be used as the turbos themselves and the whole engine setup will have varying VE's. VE value is just a number huh. :)
I think with your code on a normal or larger turbo motor we would see classic ITB mode advantages off boost and then potentially have a more SD behaviour at higher rpm when turbo is spooling well.

I like your thoughts using EXTMAP input (i.e a 3rd map sensor) instead of baro. Then can keep baro for baro. Sorry I haven't looked at the code since original B&G MS1, early MSextra days.
suberimakuri
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Re: "Differential" ITB mode

Post by suberimakuri »

How are you going with this now?
Any new discoveries?
whittlebeast
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Re: "Differential" ITB mode

Post by whittlebeast »

I tune my motor with SD below 3500 RPM and AN above 3500. My point is, sometimes there may be a different way to skin the same cat. You may be able to do something similar. Note that this is a racecar so most of the pit driving is in SD mode and almost all on track stuff is in AN mode.

Here is the tune if you want to take a look how I did it. Low power tuning is done on VE Table 1 and the high power tuning on VE Table 4

http://www.nbs-stl.com/CrxTypeR/B18C%20 ... %20001.msq

VEAL should work just fine with this setup.

Here is my tuning screen that I built in TS Ultra to make dealing with this stuff a little more do-able.

http://www.nbs-stl.com/CrxTypeR/AAW%20T ... Screen.PNG

Andy
suberimakuri
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Re: "Differential" ITB mode

Post by suberimakuri »

Andy, with all due respect, we're talking about boosted motors here. I'd like to keep on topic about original posters modified firmware.
whittlebeast
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Re: "Differential" ITB mode

Post by whittlebeast »

But you could do the same concept with any two tuning modes. Whatever you need for your application. One car I did had two SD tables. One below boost and the other in boost.

Andy
suberimakuri
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Re: "Differential" ITB mode

Post by suberimakuri »

I understand that and have combined an SD tables already.

OP, when you have time, be interested to hear thoughts after couple months running about.. :)
derbybrit1
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Re: "Differential" ITB mode

Post by derbybrit1 »

Arowana - can you post pictures of your ITB Load TPS Switchpoints and ITB Load at TPS Switchpoint tables? Is the ITB Load TPS Switchpoints table with or without supercharger enabled?

Question: I thought I read that you tuned your Primary table without the supercharger enabled. When you reconnected the supercharger, for partial throttle/off-boost conditions there is still going to be more air pushed into the engine. Won't that have a significant effect on your tune VE's? If that is the case, I don't see how you can tune it with the supercharger disabled.
Please explain.

BTW, brilliant work on your Differential ITB Mode concept and execution.
Aprilia Rotax V60, MS2 Extra 3.4.2, Interface PnP ecu for Suzuki 1000 http://interfacepnp.webs.com/gsxr1000pnp.htm
suberimakuri
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Re: "Differential" ITB mode

Post by suberimakuri »

It has been a few years, how have you been Arowana? How is the setup?
After a hiatus I'm back tuning and driving something around tuned SD ve1 and AN ve2 per my earlier comments.
Keen to hear any learnings or thoughts. Hope you're well~
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