Momar

This is not exactly a diy/prom question, but I thought you guys might be a good source of information for this since you deal w/ the timing curves electronicaly in number form.

I have been considering getting this. http://www.holley.com/HiOctn/ProdLin...C/800-300.html I would be using it with a carbed motor, but I believe it would give me the ability to program my timing curve digitaly. I figure that It would be used in place of mechanical advance, but vacuum would still be used. Does this sound feasible so far.

So here is the deal. I am only looking for information regarding wot right now. I have read that to much timing can hurt the high end, but the more timing helps the low end. I was curious if you guy had any examples of what you were running for wot timing curves. I am not really looking to get exact numbers as to what to set my timing curve to, but more of how it should kind of look. Should the timing actually drop up high, and if so how much. I know that w/ mechanical advance you try to get the timing in as quick as possible, but want it to stop going up around 3000 or so. Is this true, for you guys also. Do you guys have your timing in sooner since you dont have to worry about the timing advance while the car is trying to start? I just wondered if something like this would give me enough benifit to be worth it. Any input on this would be appreciated.

Thanks

Ben

Grumpy

A 32 point timing curve is hardly more then laughable, IMO.

Take an ecm, and wire it up as a timing computer, and you'll have a 200 point table, and cold engine timing table.

Poke around the archives here, and I'm sure you'll get the details you want. Might look at the DIY-EFI list for 747 and timing, in the FTP area. There should be an article with all the details of what to do.

Mc Firebird

if you download an ecu file and a bin file or two and a program to view the tables, then you can compare stock against performance chip timing tables as a guide.
TunerCat gives you 30 days evaluation free and tunerpro is just as good.
If you need ecu/bin files to try out let me know i can send some to you.

11sORbust

I usually stick w/o a wot "curve". I shoot for a straight line. Like 32* from 3000rpms up, that is generally how I do it. I might add/remove like 1-2* here or there but the idea is to get a flatline. So if you are going carb then I would suggest a mech dist. Much easier and less "potential part failure".

There is two guys that might give you more insight/opinions. Bo is really good with ignitions(and everything else) and aaron has a carb with an ecm to control the spark(ran like that for long time). They are both at team3rdgen.com.....

TRAXION

It is very useful to pull timing OUT of the WOT curve in the higher RPMs. Somewhere AFTER peak torque is when you should consider pulling away the timing.

I flatline my curve at 38d and then eventually drop to 34d. If I have a chance to dyno then I will globally reduce my timing at WOT to see if I lose power. You want to run the least amount of timing possible ... but still produce good horsepower numbers. So, if your horsepower is basically the same with lower timing then you definitely want to run lower timing.

Tim

kevm14

I thought it was the opposite. I thought you wanted the least amount of timing at peak torque rpm and 100kpa, due to that being the area of the highest cylinder pressures. Then I thought you wanted more timing (or at least the same) as revs increase past the torque peak, due to the effects of rpm and decreased VE. Is this not correct?

I agree that the least timing with the most HP is what to shoot for, however.

Momar

When I looked at it I thought it was saying that you could adjust the timing 32*. I wasn’t thinking 32 points. I guess that might be kind of limiting. I will look more into it a little later to see exactly what the deal is.

Traxion, you say it should drop off a little after peak torque? I was just curious, but why would this increase power? Also, how should the timing curve below 3000 look? I wont probably even really see below 3000 at the track, but for responsiveness when acutally driving the car how steep should the curve be. The cam I am looking at is a large solid cam. I will be revving pretty high. I was told that I should lock the advance out, and just run full advance all the time w/ this cam. The book that cam w/ my demon also said that they tend to like a base of 18*+. If I did it this way, I suppose I could use the single stage retard in the msd digital 6 to drop the timing up high. Any other opinions on whether the programable curve would be worthwhile to me or not would be appreciated. It sounds cool, but thinking about it, I don’t know that it would do a lot of good on my setup. Let me know if you agree or disagree.

By the way, even thought I am currently building a carbed setup, I do plan on eventually getting a FI car. I used to read this board all the time, and still check in on it to see what kind of new advances have been made from time to time. I do appreciate all of your knowledge. I have watched the board enough to know that there is a huge wealth of knoledge about the fuel injection here. I hope to eventually be able to get into prom tuning and such. I have played w/ a LT1 a little on tunercat, but no major tuning. Mostly just fixing minor stuff to get it ready to work in a non fourthgen. With my car currently, it started out carbed(ccc) and I could have converted to tpi, but I am looking to make quite a bit of power, and I just cant afford to do it w/ fuel injection right now.

Thanks for the help and any other ideas welcome.

Ben

Grumpy

I've never seen it to be universally true about adding or subtracting timing at rpm higher then peak torque.

Momar

Well, Grumpy, I looked into it some more and your right. The you set the curve in 500 rpm intervals. Out of curiosity though how can the box adjust the timing? Do you need a special dist? How long are the contacts for a normal dist in contact w/ each cyl? Would it be long enough to actually adjust the timing curve like that?

Thanks

Ben

dimented24x7

iTrader: (2)

RBob wrote up a paper on how to run an ecm as timing only.>Click< I wouldnt use any of the C3's though as in stock form they can only do timing up to around 3600 rpm (plan on rectifying that soon with mine). After that the extended spark slope takes over. Theoretically the same thing can be done with one of the 90+ speed density TPI ecms. Those are better in that there is more resolution and tables that extend further. Basically, go out to a junkyard and grab the ecm, wire harness, distributer, and the sensors. With the addition of a good aftermarket module and coil youd be in buisness. The only drawback is that youd have to purchase a prom programmer (usually a pocket programmer) and some other stuff to be able to set the timing properly. Otherwise youd be stuck with the stock tpi timing tables, which really wont work for you. Youd probably be looking at around 400 some odd dollars for all the stuff, and some time to get up to speed on how to set it up but it would be worth it in the end. The increase in tunability and precision would help power and consistancy and youd also be able to improve part throttle driving as well.

dimented24x7

iTrader: (2)

As for the dropoff after peak torque, I had to do that as well. The engine would nose over after around 3500 rpm or so if I just left it somewhat flat. Probably not true for all motors but its worth experimenting a bit.

Momar

I will read that. I have thought about that and have a SD TPI computer, but no harness. I do have a cc dist, but it is from a 85 LG4. Would it work? It would be nice in the fact that you could also probably use the knock sensor. The problem I see is that even though this would be a better controller I still am running on a stock ignition and it is still going to cost more money to upgrade it. If I could get the harness for a decent price, it could be worth it but then I still need the programmer. I might be able to get a couple buddys to split the cost of that w/ me but I dont know. Like I said, I will read that and see what I think.

Thanks

Ben