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Chip tuning

88-383

88-383

1/2 ton status
Joined
Sep 11, 2005
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Location
Tracy. CA
What aribles do you have to change to speed up the idle some? My 355/cam combo makes like 50kpa/15" at cold idle. Then when it warms it drops to 30kpa/10" as the idle slows to 525RPM.

I have everything to burn chips and can handle that part. I'm just trying to figure what params need tweaking. I tried a chip with the target idle speed vs coolant temp cranked up to 650rpm but the truck still seemed to idle down to the stock numbers. What am I missinng? I'm using Tuner CATS software.

Kelvin
 
Must be doing something wrong somewhere. I changed my idle vs coolant targets with tunercat and it worked fine. Can't remember having to change anything else to make it work.
 
Did the changes take right away? I had the batt disconected, so that should be all I need to do right?

Thanks

KM
 
88-383 said:
Did the changes take right away? I had the batt disconected, so that should be all I need to do right?

Thanks

KM
Click to expand...
You're burning an eeprom right? So you must disco the juice anyway to change proms. Yes they work right away. I'm no expert on this by any means. Just dabbling with it. There's a ton of info over on 3rdgen worth looking at. Mr Yeager seems well clued up on this stuff as do a few other members, they may well chime in in a bit.
 
Actually I converted the eprom to a flash chip. But either way, the batt was disconected. I really wish this forum had a TBI tuning section!

KM
 
I haven't messed with the idle RPM stuff, since my motor idles fine. Nor the flash stuff, just EEPROM. Actually haven't gotten any further than changing the fan temps, but it was then easy to see that my PROM's were working as the on/off temps changed. :)

As suggested, you will probably find your answer over on thirdgen.org in the DIY-PROM section, or perhaps the plain old TPI/TBI forums over there. Either focus on searching for "radical" cam info or idle speed increase.

This does beg the question though, is your combo so radical that vacuum *should* be that low, or do you have a vacuum leak??
 
Motor idles fine ,but 525rpm is too low for my cam. The vacum falls from 15" below about 650rpm. Lingenfelter recomends 750rpm idle and the cam will give 15"s at idle.

KM
 
88-383 said:
Motor idles fine ,but 525rpm is too low for my cam. The vacum falls from 15" below about 650rpm. Lingenfelter recomends 750rpm idle and the cam will give 15"s at idle.

KM
Click to expand...
That's a lot of idle! Does he say this is a comp friendly cam?
 
Yup, 7747! and this cam is very very computer and smog friendly in the TPI world. It ran so well in my TPI engines I had to give it a try. Normally you would think 650 and higher RPM is high for an engine, but it's not out of line for a performance piece.

KM
 
I just looked through my truck's 7747 bin, and tunerpro's ECU file, and less the desired RPM vs coolant temp table, I can't find anything that'd cause it not to increase the RPM as you set it to...
 
Thanks Russ! I'll try again but with a bigger change, maybe it's doing it and I cant tell.

KM
 
What's the original target idle? Is it truly 525RPM?

Even that sounds low for stock to me, but I haven't (yet) logged RPM without the ECM upping the idle to 1000RPM while logging.
 
Dorian, thats probally becuase you are applying reistance between the diagnostic wire and ground. The `7747 does not require any resistance to start transmitting ALDL data, it does so all the time. If you just read the data, it shouldn't increase your RPMs at all.

Ok, I just loaded up my 89's AMUR bin, and here is what I've found:

At 100 degrees C, the engine should be idling at 525 RPM, according to the stock desired idle speed vs temp table. With the RPM increasing from there to 650 at 115 degrees, and decreasing from there to 600 RPM at the colder temps.

There is a %throttle follower in the constants chart so the RPM is changed based on if you are in gear or not according to the park neutral switch. When in gear, that % is nearly 20%, and when out of gear, its approx 12%.

Stall saver comes into effect at 400 rpm, and disengages at 525 RPM.

Other than that, I can't find any references to idle that seems like it might affect what your idle is suppost to be. Maybe check to see what your coolant temp sensor is reading and make sure it is accurate?
 
You need to raise your IAC vs Temp counts to increase your idle speed. The IAC acts like a vacuum leak, it does NOT control the AFR like a lot of people think, but rather is used to control the idle speed. Raise the counts a bit and see what happens. Here's a short cut & past from a thread over at thirdgen.org that will help with something that you will also need to be aware of:


In order to go closed loop, besides the 'in drive' parameter, the kick down steps needs to be greater then the IAC vs. Coolant steps.

If the kickdown is 25 steps, and the coolant steps at 56C is 24, then at 56 C the ECM will go closed loop idle control. Same if the coolant steps at 56 deg are 10, the ECM will go closed loop shortly before reaching 56 C (interpolation between table entries puts the coolant steps at less then 25 before 56 C is reached).

OTOH: if the kick down steps are 15, and the lowest steps vs. coolant is 24, then closed loop idle will never happen.

The bottom line is that the kick down steps (@ $5D8) must be at least one step greater then the IAC position vs coolant table (@ $5F5) steps for the ECM to fully control the idle speed.
Click to expand...


Hope this helps. All of this stuff is interconnected and it helps to be able to burn a chip quickly and cheaply when troubleshooting problems....for that I HIGHLY recommend getting a Prominator. It makes downloading a new burn into a 30 second job.:D
 
Wingnutt said:
You need to raise your IAC vs Temp counts to increase your idle speed. The IAC acts like a vacuum leak, it does NOT control the AFR like a lot of people think, but rather is used to control the idle speed. Raise the counts a bit and see what happens. Here's a short cut & past from a thread over at thirdgen.org that will help with something that you will also need to be aware of:





Hope this helps. All of this stuff is interconnected and it helps to be able to burn a chip quickly and cheaply when troubleshooting problems....for that I HIGHLY recommend getting a Prominator. It makes downloading a new burn into a 30 second job.:D
Click to expand...

Cool, good to know! I totally missed that entry the first two times I went through the ECM file!

I'd love a prominator, but don't have nearly the cash for it :(
 
Thanks guys, I was thinking that had to be it. I'll burn another chip:wink1: I still think our forum needs a TBI tuning section though! It gets old going on Thirdgen asking questions regarding how to get a K5 running better:D. But they allways seem willing to help.

Maybe we should start a poll to check intrest? Maybe I'm all alone on this?

Kelvin
 
I'd love an EFI forum here! I know there are many guys running TBI, and several guys running TPI (myself included) and it'd great to be able to work together on the issues we all run into! Someone else always thinks of something that you'd never have even thought of...
 
Ditto the TBI/EFI tuning forum! Maybe Steve will open one up in the near future.:D



Edited to add......your idle should be 650-700 rpms in C/L.
 
8747 or 7747

I have a 90 Burban 2500 with a 8747, tried to program a chip, Guess I don't know enough about what is going on here. I got the 8747 file from tunercat and without any changes it runs like crap when I install it. The other chip is running the system at open loop, I guess a set of default parameters. I need to get the thing working properly, is there a place to find out the stock program and what I should change for non stock mods?
What is the diff between the 8747 and the 7747?
Fred
 
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