Cal 72pph

[show-off]

I am in the need of a 72pph manual tranny cal to burn...anyone got one?

[Frank]

Rob has done a 72lb/hr for me, but it is an ATX and the wrong year. I would start with him.


Frank

[show-off]

He sent me one last year and I finally put it in yesterday and it won't idle worth a crap or run either. That is the problem!!

[Frank]

Whats it exactly doing for idle and such, descriptively that is? I am sure Rob or we could remidy that.


Frank

[show-off]

He did a 52 & a 72 that should have been the same set-up w/ just different injectors. The 52 works and the 72 does not. It has erratic idle and won't rev/run either. It almost sounds like it is missing really bad, but the car runs fine w/ his 52 chip and 72lbs injectors...just too rich.

[ShelGame]

Hmm, Let me look at your cal again. I'll post back later...

[ShelGame]

Whats it exactly doing for idle and such, descriptively that is? I am sure Rob or we could remidy that.


Frank

BTW - not to hijack Mark's thread - but how does the cal run for you , Frank?

[Frank]

Last I drove it, it ran great and was spot on. I do have minor idle issues, but I think they are minor and can be fixed. I took care of it by adjusting the idle screw. I am not worried about it that much.

I did have starting issues, but found that its my fuel upgrades causing the issues. The bigger lines cause it to bleed down further then normal, so I have to prime it twice. I will probably adjust the cal to do a twice as long prime.


Frank

[ShelGame]

Mark,

What fuel pressure were your 72's rated at? Is it 72pph @ 43psi or @ 55psi? What fuel pressure are you running?

[ShelGame]

Last I drove it, it ran great and was spot on. I do have minor idle issues, but I think they are minor and can be fixed. I took care of it by adjusting the idle screw. I am not worried about it that much.

I did have starting issues, but found that its my fuel upgrades causing the issues. The bigger lines cause it to bleed down further then normal, so I have to prime it twice. I will probably adjust the cal to do a twice as long prime.


Frank

I think I found something that might actually help idle a little with big injectors. There's an idle error PW lookup (used when the ECU is trying to control idle with spark and fuel only). The table loses a ton of resolution when you go with bigger and bigger injectors. The table lookup is multiplied by 4 before used. So, I deleted the 4x mult and changed the scale of the table. Voila - 4x the resolution in the table.

I don't think this would be your issue, Mark. But, it wouldn't hurt to make the change.

[Frank]

Based on how my idle was hunting and pecking, that sounds like it could be it for me at least. Where did you delete the multiplier at?

[ShelGame]

Based on how my idle was hunting and pecking, that sounds like it could be it for me at least. Where did you delete the multiplier at?

This is for the '90/91 2.5 T1 based cals only:

Make a 16-bit constant at address #BC92. The value will be 05 05 (lsld lsld). Which is 2 logic-shift-left commands (logic shift left is the same as a 2x multiplier in binary). Change that to 01 01 (nop nop).

Definitely, DO NOT change the value to anything else. Extremely unpredictable results will occur.

That multiplier is for the table at #83DE (IdleErrorFuelPWModifierFromBaro). As you can see, that table has a really small value in it. So, when it gets scaled from 33pph to 72pph, the value gets even smaller. This table is used for controlling idle with fuel and spark (normal operation - the AIS is actually kind of a last resort).

But before you do the 400% scaling, I'd copy the stock table back into your cal. The resolution was already lost when I scaled it from 33pph to 72pph. After you copy the stock points back in, then scale it by 400%, and then by 33/72 = 45.833%.

I'm not sure how comfortable you are with this stuff, Frank. If that's too complicated, I can post the updated cal/table file.

[Frank]

I should be able to make the changes no problem, but obviously my assembly sucks. Could you explain what is actually going on with the lsld and nop commands? Are we not changing the actual multiplier, but instead nulifying the multiplier by someother command?


Frank

[ShelGame]

I should be able to make the changes no problem, but obviously my assembly sucks. Could you explain what is actually going on with the lsld and nop commands? Are we not changing the actual multiplier, but instead nulifying the multiplier by someother command?


Frank

Geek mode on (please note the bright green flashing "G" on my forehead):

A logic-shift-left is an implicit multiplier. In binary (base 2), it's a multiplier by 2. It's the same in decimal (base 10), actually. Do a logic-shift-left on the decimal number 122, for example. Shift all digits to the left 1 place, and fill in the last digit with a 0. The result is 1220 - 10 times the original number. It's the same with binary, but the multiplier is 2.

lsld is a logic-shift-left of d (the 16-bit accumulator). The table lookup goes into the lower byte of d. So, 2 lsld's is the same as a mulitply by 4, but takes a whole lot fewer clock cycles than an explicit mulitply would. And, it also turns an 8-bit lookup into a 16-bit result (the PW is a 16-bit number). But, the lookup value is so small, that even after the 4x mulitplier, the upper 8-bits are all still zero's. So, the multiplier is pointless, and just causes the table to be lower resolution.

The nop is the no-operation command. Basically, the CPU doesn't do anything, and it just eats a clock cycle or two. lsld and nop are both single byte commands, so it fits well. In an ideal world, we'd just re-compile without the lsld (and therefore wouldn't need the nop). But, since we're just hacking exsisting code, we need to fill the lsld's with something that doesn't interrupt the program flow.

Geek mode off:

Whew...

[Frank]

Understood completely and well done. I had forgotten almost all of my assembly class from college.

So would it be wise of us to do calibrations for +40's that use 01 05 (nop lsld) to partially scale that table to something in the middle of the road?


Frank

[ShelGame]

Understood completely and well done. I had forgotten almost all of my assembly class from college.

So would it be wise of us to do calibrations for +40's that use 01 05 (nop lsld) to partially scale that table to something in the middle of the road?


Frank

I think you'd want to use the largest possible scaling without causing an overflow. The value is so small, even for a stock cal, it seems like a good modification.

This table isn't in the earlier (T2) code. The idle error PW was calculated completely differently. So, my guess is - it was new and maybe they thought they would need a bigger scale that they actually did. I dunno.

Keep in mind, this is just an idea I have. I haven't tested this on my (or any) car yet. I don't see any dire consequesnces, but it may have little to no effect at all. I do really think it will help, though. And, if it doesn't work, it should be pretty easy to undo...

[Frank]

Roger dogger

[show-off]

43.5psi like it should be. Won't idle well at all or rev up. Almost like a timing miss.

[ShelGame]

Roger dogger

You gonna try it? Let me know how it works if you do :eyebrows:

[Frank]

it is going to be a few weeks. :(

[Aries_Turbo]

Understood completely and well done. I had forgotten almost all of my assembly class from college

Frank

dude, we didnt learn it in the first place. you and I just both built the circuits and folks like scott morris did all the programming lol ;)

Brian

[Frank]

LOL. I learned some.... concept! hehehehe

[Aries_Turbo]

riiiight. you learned about as much as i did ;) im actually learning more messing with cals than i did at school cause i can apply it as i learn.

Brian

[Frank]

I messed with it a little bit afterwards, but I utterly hate it.