nAst1: Progress and Concepts Thread

[robertisaar]

if you're spinning that badly with the 3.23s..... can't imagine what the extra 27% of the 4.11s will do. posi or locker or ???

[caffeine]

Well I only have 225/60-16s on the rear right now but have some 275/40-17 street slicks for autoX that should grip much better. Also dialling back the dampening on the rear end will help with launching. I'll find out more at the track on Sunday as long as I get off work in time.

[Mars]

YESSSSS!!!!

Can we get this to work on a 7730 somehow ?

[caffeine]

Interestingly enough the spark limiter isn't nearly as harsh feeling as the fuel cut was either. Much louder though

[ericjon262]

Jealous.

[caffeine]

Just looked at my log and it was obviously slow because after I shifted into 2nd I was only at 1600 rpm lol. Still making 3 lbs of boost at that RPM though. Boost starting increasing again at 2500 and by 3200 or so it was getting back to full boost. And I stopped accelerating at 5200 rpm or so (sucks not having a working tach yet ).

Interestingly with the spark cut limiter enabled the RPMs were going between 2400 and 2700 with the rev limiter set at 2400. Although its somewhat hard to say exactly because the engine speed and engine speed x 50 are inconsistent with each other. Like I'm going through the log at 25% speed and there's spots where one reads 2600 and the other reads 2450, for example. Don't know what's up with that. I'm only seeing that inconsistency when the limiter is enabled though.

[caffeine]

Maybe if I set the 'enable speed' lower than I have it then spark will be cut for a longer duration and stay at the desired rpm?

[robertisaar]

the spark/fuel cut code works on a 80Hz loop, that's not a lot of time to accelerate past the desired speed, but it may be enough with no load on the engine. so, lower away, if you feel it's necessary. widening the kill / restore gap or lowering both overall is the way to go.

RPM and RPM X 50 can disagree with each other at times when RPM changes rapidly. the way i have their calculations setup, RPM X 25 is done in the factory location of A71C, but RPM X 50 is done where i intercepted the routine at A558. the RPM X 50 loop is done on an 80Hz loop, the RPM X 25 value is calculated by a subroutine in 2 different places in the code(A763 and A614), but IIRC, both of those are 80Hz loops as well, they just may not be the same loop. point is, if they don't agree, your actual RPM is probably between the two values.



Mars: i don't see any reason why it couldn't as it doesn't use the extended RAM.

[caffeine]

I think Mars needs the 2/3bar support though.

[robertisaar]

that's true.... using a 7730, would either need to add in the missing RAM and addressing chip directly to the board or use the NVRAM hack and i would have to add in support for that by moving addresses around.

[Mars]

Hmmm. sounds like a PITA.

[robertisaar]

pain is art.

think of the "art" that could be had if i go through with my triple 7727/7730 project.

[robertisaar]

well, now i know why my MAF simulator wasn't working...

some of the oldest DIY-EFI archives jusy popped up, came across this string of messages:

http://lists.diy-efi.org/pipermail/gmecm/2000-January/006748.html

culminated here:

http://lists.diy-efi.org/pipermail/gmecm/2000-January/006762.html

the 8706 mentioned is a batch-fire ECM used on the buick 3300s.... internally and externally, it looks identical to a 1227730, i may still have the comparison pics somewhere, but the only real difference between them was the resistor/cap filter for the VATS/MAF circuit changed and i think one IC had a different part number.

anyways, using the values spec'd, the 7730/27/49 MAF/VATS circuit has a 159Hz low-pass filter.... so any signal above that is filtered out. using the 8706 numbers, it has a 27,234Hz low-pass... in reality, i have the table setup for 976-12,240Hz and there is no high-pass filtering on the circuit, so that won't be a problem.

so, to use a high-frequency MAF on a 7727/derivative, you would have to open up the case and change 1 resistor and 1 capacitor... i may take pics to give a good idea of how difficult it would be, but i've resoldered a few pieces on mine already(to add a few useful A/D channels) and i didn't think it was difficult. luckily, the SMT components aren't too tiny on this vintage of PCM.

[robertisaar]

moar crazy-old info:

http://lists.diy-efi.org/pipermail/gmecm/2000-April/008689.html

turns out, SOME P4 units got a different processor than the typical P4s... this version has 1024 bytes of RAM instead of 512... i wonder how commonly that it got used with remanned units?

[caffeine]

How long till we see a 1.08 release?