Alright, I have around 200 bucks to blow. I'm debating about which kind of analysis tools to get (diacom/autoxray/etc.) What are your guys opinions? Do any offer more options than others? Easier to use?
Any help would be appreciated.

 

I like Diacom+, but it is more expensive than $200.00. They have 2 versions, the "+" version and the regular version. I forget the differences between the two; Rinda can help you though at www.rinda.com

With Diacom+, I capture about 20 minutes of data at its highest frequency (which I prefer to use). Auto Xray can download to a computer but you must "dump it" after you have done your test.

My opinion is, that if you want a "long test" Diacom is better as you can save your data and keep driving. For "tweaking" my eprom, I take as long as drive as possible with as many different speed and load conditions as possible. I then take all those save files, translate them into a DBF file, and then import them into Excel. I then sort the data in RPM/MAP/INT order and determine the average "INT" value for a specific RPM/MAP/INT range and adjust my VE table accordingly.

With Auto Xray, you are limited to the amount of memory of the unit (don't have one, so I cannot comment). I think it would be great for "short trips", but I doubt that you could take a 1 hour drive and store that much information at the highest frequency (6.3 frames/second with a 8192 baud ecm).

 

Being an owner of both, I HIGHLY recommend Diacom over the Autoxray. Diacom only allows you to save like 20 seconds, while Diacom+ doesnt have that limit.

Glenn, I have a question for you and all the expert prom burners. If I were to take a Diacom capture of my car, and send it to, say TPIS or even you, to upgrade the Level V PROM that I already own (i can still feel the KY jelly), is that info good enough to do a custom burn on my car? Or is there more trial and error to it than that? Is that merely a starting point in the entire process?

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1989 IROC-Z 5.7L

[This message has been edited by Omar (edited January 29, 2001).]

 

I cannot answer for the experts. With their experience one might be sufficient. But for myself, I like as much data as possible and to do it as many times as necessary.

I find the Diacom+ data greatly reduces the "trial and error" and guesstimating process. It gets me closer and closer to my goal of 128/128 "perfection" that I am seeking on every cell of the VE Table. Though I should add that 128/128 may not be attainable on a particular cell. Within the VE Table you may have a cell entry say at 68.4. You cannot adjust the entry by a factor of .1. I find .3 or .4 is the smallest change that I can make. Thus if my average reading say for the 2000 RPM 60 KPA value is 126.8, if I lean it to 68.4 (next leaner setting, I might get 129.2). I have therefore gotten as close to 128 as I can. I should add, that I do this by initially locking the BLM min/max to 128, thus I can rely on the INT for the indication of whether I should go leaner (values less than 128) or richer (values greater than 128).

Lastly, I prefer to concentrate on one area (VE tables first) and when I have hit the point of diminishing results, I then concentrate on the Spark Table. When I have hit the threshold of maximum advances in the various RPM/KPA ranges; I review the VE Tables to see if any of those values have changed significantly to justify a further revision.

Yes, it does sound time consuming, but NO aftermarket eprom burner is going to go to that level of trouble to attain 128 perfection. As far as they are concerned, if you were getting values from 110-145, they'd consider it "close enough". They would only re-burn another eprom IF you had a major driveability problem. To do the level of work that I do, I suspect they would want thousands of dollars, just because of the time involved. That is why you ultimately cannot beat an eprom that you have "tweaked" yourself.

 

Thanks for that excellent answer! I guess I will be reading the archives for info on how to get started learning and what equipment is best. Thanks!

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1989 IROC-Z 5.7L

 

Glenn is right. FYI, I just finished the process he mentioned in tuning the fuel and spark curves by dyno AND driving the vehicle. You cannot imagine the difference that all the har work has given me. Stock EPROM with stock base timing yielded about 195hp, stock EPROM with 6deg base timing about 215hp, my custom EPROM = 245 hp and mileage inreased from 17 to 20 mpg on the highway. I cannot impress upon you guys how much the throttle response and overall driveability has increased. I have TONS of EFI experience but this has been my first GM experieince and my first experieince with a system that takes so long to manipulate. It is rewarding to make changes on the fly with a laptop or handheld module (edelbrock) in other systems but I have to admit I am VERY impressed with the GM ecu's ability to control the engines fuel/spark functions. UNBELIVEABLE!!!

The above motor is not stock internally, obviously, and most followers will know what I am running... Mellow 3702 Edelbrock cam( 194/214, .395"/.442"), too, in a 350cid with clean heads/exhaust and Performer intake 1-11/16" TBI.

Just wanted to share my experience. And time spend with a good diag tool (I use SnapOn) is GOLD to your outcome. I burned about 25 chips, by the way but could do it in less, now, from experience...

 

Soo, you think that's good?.
Try reading about the IAC, and how it works.
Might look at what DFCO is.
Trust me your just warming up on what fun and drivibility can be.
Some of the bins offer lean cruise modes.
I run 17.2 AFR cruise, 15.2 at idle, and a few other tricks.
Mess around and you'll really see what you can do........

 

Already did all that IAC/PID/etc research... thx. It's on diy_efi.org/gmecm/papers/xxxxxx for all to see...

Grumpy, I have a 7747 ecu... Any helpful hints for me??? I think that my ECU does not keep the BLM's stored after engine shutdown... Are all TBI ECU's this way??? Doesn't hurt cause I'm mainly at 128 BLM's about everywhere but driveability on warm starts hurts when just starting the tuning process, open loop stuff, that is...


The Tunercat I am using doesn't have all that much stuff (taht you mentioned) that I can change. are you using some other software??? Or custom definition file(s)?


[This message has been edited by FastBroker (edited January 30, 2001).]

 

Grumpy, I too would like to learn more about the controlling of the IAC. I will scope out the link posted above and do more research on the IAC. Any further insights that you can offer on the IAC will be most welcomed.

I noticed that the "highway mode" on for my eprom and have "played" with it. However, I can also see that your VE tables need to be very close to "128/128" get the full advantage of it. When I first "invoked it" it seems the ecm relies solely on the tables when using "highway mode", thus if you are too lean or too rich, you either won't get the advantage intended or worst, go too lean. But, I can definitely see the advantage of leaning out the mixture when you are cruising on a long flat highway. No, need to be at 14.7 when 16.2 (or as you are doing 17.2) works just fine, and cuts down on the amount of fuel going out the exhaust.

[This message has been edited by Glenn91L98GTA (edited January 30, 2001).]

 

Just realized my IAC is open to about 90 - 110 while at highway cruise... That's GOTTA be wrong, man...

Grumpy/anyone PLEASE help??? Do I need a different DEF file for my Tunercat that has the ability to change the IAC at operating speeds/rpms??? Right now, I am EGR-less and VSS-less, if that makes a difference, which I am sure it must...

Thanks in advance.

 

That sounds about normal. The IAC also acts as a throttle follower (or some similar phrase in that IAC paper), so it'll ramp up when you press down on the gas. Likewise, when you come to a stop, it'll ramp back down to the idle position after a couple seconds. This idle position (in IAC counts) depends on the throttle body's minimum idle setting, as well as how much spark advance and fuel you have at idle.

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Greg Westphal
'87 IROC 305TPI/A4

 

Yeah but should it be open to above 100 or so when driving down the highway? That doesn't sound very efficient to me... Can the IAC Counts vs driving modes/speeds be changed??? IAC open is basically a controlled vacuum leak and I'd like to get it as small as I can to get the air into/by the butterflies... Any help/ideas?

 

I've noticed the same thing while driving in part throttle cruise...IAC varies between 90-110. I would have to review my Diacom readings, but I recall noticing that there appears to be a relationship between the IAC being above and below 100, and what my INT is (above or below 128 when my BLM is locked at 128).

What I have also noticed is that the closer I am to 128, the closer the IAC is around 100.

My suggestion is to concentrate on getting the INT as close to 128 (when the BLM is locked at 128), and let the IAC do what it wants to. It seems to like to get as close to 100 as it can.

 

I am pretty much at 128's all around. All I know is that 100 IAC counts is OPEN man!!! You can idle to the moon with it open that much. Gotta be a way to fix this.

Are you saying the IAC moves to makes changes in mixture/BLM/INT??? If so, I did not know this was happening. I though it was entirely injector pulse variance. ?????

 

I am "weak" on my understanding of the IAC. I am just now reading up on it. This is just an observation of what I have seen while driving at part throttle at highway speed.

As for what it is doing at idle, I will have to check my Diacom readings. That is a totally different situation between idling and "cruising" on my car. This is just how the SD system on my car behaves and what I have observed.

 

If you read all of my short post from yesterday, you'd notice that I said "Likewise, when you come to a stop, it'll ramp back down to the idle position after a couple seconds." The IAC motor will extend (counts go down) to bring the idle speed down to what is requested in the table for the coolant temp you're at. Keep in mind that as soon as you start moving or the %TPS goes above zero (or some very small number), this table is ignored since you're no longer at idle speed. My IAC counts at idle and at operating temperature are around 30-35 last time I checked. It's neat watching the idle speed drop in 2-3 seconds after coming to a stop.

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Greg Westphal
'87 IROC 305TPI/A4

 

I understand that, Greg, but what controls the IAC while driving? You only need the dashpot function when you foot is let off the pedal rather quickly, not at a constant TPS value while cruising down the highway. I have an open element air cleaner with 2x3" tall filters (6"tall) on it and I can here the IAC hissing like crazy the IAC is open so much on the highway. Also, I have blocked the IAC port area with molding clay and it improved drivability a lot but it inproved throtttle response at low speeds/TPS values A REAL LOT! Had no idle control with the clay in there but it was just a test. Unkooking the IAC at a low IAC will keep it there, too, and that worked ok, too.

SOunds like I answered my own question. Need a hack to find the DASHPOT table(s)/function(s). Then, the (7747) TDF editor to alter it, if possible. Sound right?? Out of my realm of experience...

 

Nope thats about right as an univeral answer. Varies with cal. Mine is 75 max. but I changed it down from 110.
IAC, and DFCO have alot to do with burn out recovery, ie some folks get to the stage of stalls when heating the hids.

 

Slight difference from readin to using.
If you go to ecmguy's area there is a complete hac of the 747, and you can figure out from there where to go.
I generally use a combination of GMEPro, tunercat, and some stuff I've written for really off the wall stuff.

the 747 is a min function C3 ecm. It's one short coming is no IAT or MAT.

Back some years ago, I and others attacked it because it was the most primitive. We went thru the whole bin making changes one at a time on an ecm bench and watched Diacom, and drove trucks to figure it out without using any code hacing. ANyway that was the the why on the 747. In time they have been the most reliable work horse of the whole line, and just an easy to use hac'd TBI ecm. One other idio, is that parked in a heated garage, and pulled out in the snow confuses wm till you hit 1/2 3/4 the first time to reset the baro., then its fine. Generally if your really into the 747 you'll find that you might have to change the WOT as the seasons change.
HTH

 

So Grumpy, do you have your (old?) TDF editor available so that I can use TunerCat to change my IAC function/counts at speed??? I have not tried to use the TDF editor but I guess I could try. Just a newbie to this ECU, that's all.

Thanks for the input/help/guidance to all, 2. FYI, my spark curve (350cid, 9.1, nice heads, no-egr, off-road only) is pretty much ready to post if anyone would like to try it. Only if someone asks, that is, and also tells me how/where to post the BIN.

Gotta go watch NASDAQ fall some more. c-ya