What controls my ignition advance curve?

[MoeJr]

There is someone on this site that burns chips for the 85 and up C4. For the life of me I cannot remember who. Mad Mic may know or Rob. I can see his post about it in my mind but not his screen name. Damn lumbago!!

 

[bossvette]

Yeah, I will do whatever. It might actually help. I cannot do any harm by retarding the timing can I???

not 6 degrees.

 

[vetteboy86]

The timing figures you are seeing are perfectly normal for a C4 chip. Heck, I have 50.6* of total timing in certain low load areas of my chip.

What concerns me is that my knock retard is actually retarding the timing 12 degrees or more at some points. This is not good, the car falls on its face, and it cannot be good for the motor. My brother with the same chip, only pulls 41 degrees of advance ever.

So there is not harm with putting the initial timing of my car at 0 degrees?

 

[wishuwerehere82]

A lot of things can make your knock sensor retard the timing.
Increased compression ratio due to new pistons or shaved heads.
Insufficient Octane rating in the fuel.
Bad MAP sensor. I had one once, and it never reached full advance.
Malfunctioning Advance module.
Improper TPS setting affecting Fuel / Air ratio. It will make a difference in an initial Lean or Rich condition.
Insufficient fuel pressure. It will knock if the fuel mixture is too lean.
Improper initial timing.
OR--- A bad Knock sensor. I had one once and it made the timing jump all over the place, all the time.

Try resetting the Initial timing to 0 degrees, then resetting your TPS to idle. Then see what it does, you can always set it back.

 

[G Winter]

You could even go as far as 4 deg retard and not hurt anything. If you were to go extreme such as retard 12 deg you could tend to run a hot exhaust, which could maybe hurt the exhaust valves but not likely.
Glenn

 

[Hardlight]

I asked Gordon Killebrew about this at FunFest and he said the ECM does it all and gives it all it can take until the antiknock sensor input rolls it back. Setting it above the 6 deg like I did on mine at 10 seems to give it a little intial jump but the ECM takes over after that.

 

[MoeJr]

Your brother is running 1 point of CR less than you and that is why he is not having an issue. Try the timing set at 0 and see how it reacts. My guess is with your CR u gonna need a prom that is not gonna advance beyond 40. 12 degrees of knock retard is way too much. Also playing into this equation is high CR along with a relatively small cam that is boosting your cylinder pressures and making the engine more prone to spark knock. I know someone on here custom burns proms for 85 and up C4's. I almost wanna say his ID is Jeff but not positive.

 

[Hrtbeat1]

There is someone on this site that burns chips for the 85 and up C4. For the life of me I cannot remember who.

-=Jeff=- He used to be a moderator here but haven't seen a post in quite some time, don't know if he is still around. I do know that he has been busy with a young'un.

I learned a lot of what I know through talking and comparing bin files with Jeff. He helped me ensure I was on the right page when it comes to burning chips. We compared files and had a few disscussions via email and phone while I was tuning a '91 in HI. Our bin files looked pretty much the same even though we derive our values for the tables a little differently. BTW the '91 turned out really good ... it would run like a scalded dog and would idle very well.

Craig sorry I haven't replied ... been real busy with cleanup around here. I need to get some info from you. What is a good time to call? You said you are running the Hypertech chip ... do you still have your stock one? If so try it and see what happens. They may have advanced the timing map in the hypertech chip beyond what your car actually needs. The falling on its face as you describe is a good indication of this. FYI most places that will sell you a chip are just going by the mods you have done and they are not going to be right for the car. They may be close but without scan data to analyze they are just going on prior experience basically a shot in the dark. I saw this with my TPIS chip ... yes there were improvements, but the car ran super rich. I had to modify some areas of the fuel tables and the spark advance tables to lean it out a bit. One thing that really gets me is some of these places that sell "performance chips" are not doing anything except changing the temp the fans come on, disableing VATS, or turning off the EGR (which is illegal BTW) then they somehow change the format so the chip can't be read much less modified (except by them) then they charge a substantial fee for this service. I've seen this with both Hypertech and Ed Wright, not pointing fingers just stating facts. My advise if they don't ask for scan data be cautious how you spend your money. One other note ... no chip tuner will get it right the first time. They may be close but not right on. The best I've done is three, we could have done more to really fine tune it but three got us pretty close. Its hard to tell the difference between pretty close and dead on and actually I don't know if there is such a thing as dead on there are always little things that can be adjusted to improve certain areas.

 

[vetteboy86]

Gerald, I totally understand. You have alot of things to take car of, which is no problem. I can send you data whenever you would like. I will be pretty busy tomorrow, but sunday afternoon probably wouldn't be bad. I will send you an email, or pm tomorrow, and we can work something out when it is okay with you.

Craig

 

[Hrtbeat1]

Try what the others have suggested and set your timing to ZERO with the EST unplugged. I have a feeling that may help you out in the mean time. There are differences between your computer and your brothers, the way the computer looks at the data. By using his chip it would be hard to tell what your car really needs. Thats why you see more parameters when you select his year in the software.

About 10 to 15 minutes of data should be good. Just normal driving around. If you have a long hill that you could drive up and kinda get on it (not WOT) that would be good. Looking for something to put a load on the car, an extra passenger helps, just to get a range of conditions. If it were not a Vette I would say pull a trailer, maybe this helps to explain what I'm looking for. I'm pretty sure the record mode has all the parameters, I can sort out the ones I need when you send it. There should be a "Export" button on the playback menu, hit that, save it to a file, then email it to me. The file extention will be .QP1 by default IIRC.

When ever you get the chance. Later man.

 

[bossvette]

Gerald
What software are you using, I may have to modify my chip in my Yellow Truck build as I am running a 214 deg cam in a 305

 

[vetteboy86]

Gerald does it matter where I put my timing for the data. I was thinking I could drive around today for a bit, but was also going to reset the timing. I will fire it up, and try some exports first before I try the 20 min drive.

 

[vetteboy86]

Well, I reset the timing to 0 with the EST wire unplugged. I am confuesed about a few things.

First: I see two values of timing on my scanning software. The first is spark timing relatiive to reference, and the other is relative to Top Dead Center. What do they mean???

Second: I would think to see a 0 degree difference between the two values if the ECM is using the base timing as a reference and I set it to 0, so why are they about 6 degrees apart always?

Third: The car runs no different, and the max advance is the same, with the knock retard still pulling about 12 degrees each time I get on it. So basically retarding the timing 6 degrees did nothing for the car from what I see with the scan software. WHy is that???

 

[gmjunkie]

Well, I reset the timing to 0 with the EST wire unplugged. I am confuesed about a few things.

First: I see two values of timing on my scanning software. The first is spark timing relatiive to reference, and the other is relative to Top Dead Center. What do they mean???

Second: I would think to see a 0 degree difference between the two values if the ECM is using the base timing as a reference and I set it to 0, so why are they about 6 degrees apart always?

Third: The car runs no different, and the max advance is the same, with the knock retard still pulling about 12 degrees each time I get on it. So basically retarding the timing 6 degrees did nothing for the car from what I see with the scan software. WHy is that???

Good ???? I would of thought, it would have made it 6 deg slower!! Maybe Chip is Defecteve? You said it's suposed to be same chip as your Bro!! Sweet Talkem man Try his, and him try your's!! But Make Shure thay are the same Chip!! Your Bro mite Beat OOOOWEEE knot's on your head if you screw up his car!! Maybe you just need to put on a Dyno? I mostly mess with OEM,not mini mod's!! The last one I bought with mod's,was a 95 purple car and was done in San Antonio by a Pro on a Dyno!! And it Ran SuperO!! But my stock C-5 would blow it's Head lamp's Open!! junk!!

 

[wishuwerehere82]

Did you use a timing light or the scan tool to set the timing? The scan tool might have the 6 degree timing advance set in one of the advance modes.

 

[vetteboy86]

I used a timing light.

 

[wishuwerehere82]

Then I'm thinking you may have a defective knock sensor that's too sensitive and firing off early. Or some internal condition such as a lean setting that's setting it off.

 

[Hrtbeat1]

Gerald
What software are you using, I may have to modify my chip in my Yellow Truck build as I am running a 214 deg cam in a 305

I use EASE for scanning and Tunercat for the EPROM modification. I'll have to check your post about the Yellow Truck ... what ECM are you using?



Just read the YT post .... speed density .... me likes. Even though it is a 305 I have the most experience in doing chips for SD systems. You do still have an ALDC right? We may have to wait till Craig Jr (Vetteboy86) is finished using my EASE system ... unless you have one of your own.

 

[Hrtbeat1]

Well, I reset the timing to 0 with the EST wire unplugged. I am confuesed about a few things.

First: I see two values of timing on my scanning software. The first is spark timing relatiive to reference, and the other is relative to Top Dead Center. What do they mean???

Second: I would think to see a 0 degree difference between the two values if the ECM is using the base timing as a reference and I set it to 0, so why are they about 6 degrees apart always?

Third: The car runs no different, and the max advance is the same, with the knock retard still pulling about 12 degrees each time I get on it. So basically retarding the timing 6 degrees did nothing for the car from what I see with the scan software. WHy is that???

It's kinda tricky the ECM thinks you have your timing set at 6 degrees, no matter what it really is set at. To actually see the difference the input would have to be changed in the chip. The timing relative to reference is internal to the ECM. Timing relative to TDC is just that. The changes to the timing should show up relative to TDC. This is strange. Did you change the software back to your year? There is a difference between the '86 and the '87-'88 ... the way the data is interpreted. That may be part of the problem. Also you said the car runs differently with the scan tool connected ... the only time I've seen that was the ECM was faulty. They are funny that way ... they won't tell on themselves ... you have to watch for changes you know should be there and when they don't appear that is one of the first things I suspect. I saw something like that with vaccuum ..... the ECM said we had low vaccuum but when we checked using a vaccuum tester we had good vaccuum. A quick trip to NAPA and we were back in business of course the wallet was $80 lighter.

 

[vetteboy86]

Well, I thought it ran differently, but turns out I have a little rough idle on start up when cold. It runs the same pretty much every cold start.

I will switch the software back to my car, but I am not sure if it actually shows this on my setup. It is very wierd in the information that changes from year to year. Well I will probably scan it out to school tonight, and try to send that off to you. I can do several readings as well.