Hey, Well i got my 383 tunnel ram'd dual tbi setup working pretty good, its winter now so no more tuning for me but i am curious about something.

I need to do some tuning at WOT but iam not too sure where to start especially since all my other tuning is done automatically for me.
right now it doesn't pop or backfire or anything like that but it definetly doesn't jump like it should.

Here is a pic, still need to clean/dressup the engine a bit more

 

If you dont have a wideband O2, that would be the first place to start.

The next thing you can do is set up an old school vac advance dist. curve. Nothing real agressive. Youll never really be able to tune every spot, so if youve had experience with vac. advance distributers, then that would be a good place to start off. Once the VE is tuned, then you can come back and start tuning the timing again. Keep in mind that the timing and VE are coupled together, so if you change the timing, the VE needs to be retuned.

The next thing to do would be to set the computer in open loop and start tuning the VE table. Start off at lower loads and tune those cells in first. After that, you can work up to progressivly higher and higher cells. Its a good idea to make sure that you dont start off right away at high loads. This way you can get a feel for what the VE table should look like, and forcast ahead so at least the fueling is somewhat ok once you get out there.

As a side note, dont let the wideband be your sole source of info. If the tune is way off or the engine isnt up to operating temps, then its only useful as a rough guide. The only time its usefull is when the engine is up to temp, the AFRs are within reason, and the ignition system is working properly.

 

There's not much old school about me. I started learning on EFI cars, so I have no clue how a carb setup should look like.

What does an "old-school vac advance" curve look like?

When tuning, as I understand it, you want the highest MPH for the lowest TPS% in a given SA cell. After altering the VE tables, I'm sure the SA table will be just as difficult when to populate as the VE table. How can a guy tune the SA table when you can't populate all of the cells? Do you look at "marker" cells and form a graph from that?

 

For WO spark advance, I just ramp it up to about 2500rpm, then run the full advance from there on. Really, dyno time is the only way to really nail the SA, a degree here and there can make a few HP diffrence. What heads are you running on that motor? If you are running your standard SBC performance head, you will probably end up at about 32*-34* advance at WOT. If you are running something like a vortec or swirl-port, probably a little less, like 28*.

 

OK, what do you mean by "I just ramp it up to about 2500rpm, then run the full advance from there on"?

I'm running vortec heads, so you think the max SA will end up being 28 or so? Will it be 28 degrees by 2500 and no advance after that?

I don't want to thread jack, but I'm sure this is useful info for other people. Thanks for the help, as you can tell, I'm very new at this still. I haven't read this much since high school.

 

Ok, Pre-Tuner here we go with an old school example. I hate to admit I am old enough to have any idea about this old school stuff, but yes I got a lot of mile on me. Only good part about that is yes I was a teenager during the muscle car era, any way enough, I am showing my age. Dimented is referring to setting up your spark advance tables initially to simulate a typical distributor setup (non computer controlled) with mechanical and vacuum advance. Mechanical advance was controlled by levers, weights, springs, and stops in the distributor to allow the timing to advance relative to RPM. The stops would control the maximum amount of advance and the springs would typically control the advance rate relative to RPM increases. So you could control how rapidly the timing would advance relative to rpm from the base timing until it reached the stop or maximum mechanical advance. Vacuum advance would typically use manifold vacuum to increase timing relative manifold vacuum. This would allow for maximum advance during low load conditions (idle and light throttle cruise) and would decrease with load such that as you approached WOT there would be no vacuum advance (minumum manifold vacuum). In general, base timing and mechanical advance were used to set performance and driveability and vacuum advance is used for mpg when cruising.
Ok, so lets take this information and try to build our old school timing table for a typical SBC mild street engine. This is an example only. I am not suggesting this for your engine, I do not know enough about your setup to recommend a starting point.
Let's say the old school guys recommend for our sample engine a base timing of 10 degrees, 18 degrees of mechanical advance all in by 2800 rpm and 12 degrees of vacuum advance. To build a SA timing table for this I would start by setting the entire SA table and the distr base timing parameter to 10 degrees as in the first attachment (old school base.jpg). Then we need to add in the 18 degrees of mechanical advance, so we will add 18 degrees to all cells in the table above 2800 rpm. This gives us 28 degrees in all the high rpm cells (10 base + 18 mech advance). This is what is call "Max Advance" (yes, I know later when we add in vacuum advance there will be high values, but this point is known as "max advance"). Then we what to ramp up all the values between idle (800 rpm) and our "all in" rpm (2800 rpm) to get a smooth transition as we increase in rpm. This is shown in the second attachment (old school mech.jpg). So, now lets add in our 12 degrees of mechanical advance. If our sample motor idles and light cruises at say 35-40 kpa then this would be the point of maximum vacuum so we will add 12 degrees to all cells below 40 kpa. and we want to ramp out our vacuum advance as load increases (vacuum decreases) so we need less and less vacuum advance added in for each of our load columns so that by the time we are near WOT (95-100kpa) we are adding in NO vacuum advance. In this case if we simply add in 1 less degree of advance in each increasing load (kpa) column it will work out well. So we added 12 degrees at idle (35kpa) and we will add 11 degrees at 40kpa, 10 degrees at 45kpa, 9 degrees at 50kpa, etc. This is shown in the third attachment (old school vac.jpg)

So, we have now developed a timing table to simulate our old school vacuum advanced distributor requirements and hopefully have some idea of what guys like Dimented and Dewey are talking about.

old school base.jpg

old school mech.jpg

old school vac.jpg

Hope this helps.

 

Nice post, thank you. It really put things into perspective for me.

One hurdle I'm trying to wrap my mind around, is the base. In the "computer controlled" world, everyone says to use the base timing set by the manufacturer; in my case, 0-degrees. Would I subtract 10 degrees from the figures in your example because it has a 10 degree base? I think the only time I'd have to add base timing is if it needed to go above 43 degrees at some point.

This isn't the first time I've heard of doing it the "old school" way. My dad and uncle drive dragsters, and they just said "set it up like this and forget about it". Of course, I'm being ignorant and thinking "ya, but yours isn't computer controlled, so mine is different". Their SBC's put out 700HP and 1098HP (No turbo, blower, or N2O), so I guess I should pay attention next time. I have so much to learn.

 

If you are running a near stock engine, then 0 degrees base is fine. When you are dealing with cammed engines it is often better for cranking (startup) reasons to have a base timing anywhere from 6-15 degrees. Just be sure that your engine distributor timing and your ecm base time are set the same, then the values in the tables represent the SA the engine will be running at.

In the example, if you set the base to 0 degrees and still wanted to only run 18 degrees of mech advance and 12 degrees of vacuum advance, then yes you would decrease all the table cells by 10. Keep in mind this would reduce your max timing (total timing) to 18 degrees. So in that example one might want to run more mechanical advance than the 18 degrees to get more max timing.

 

It fires up fine, so I guess it's not far enough from stock to have the need to change the base.

I have a new 350 crate engine with vortec heads, hyd roller cam (.488/.495), Holley TBI, GMPP vortec intake, K&N filter system, shorty headers with 3" exhaust, new sensors and new OEM ignition. I'm waiting on the EBL system and soon after that I'll probably add a WBO2.

I'm noticing on the stock bin that the SA numbers are very specific (like 23.71). Is this just to smooth the table out or should the numbers I enter be as exact?

 

Pre-Tuner

Some of what you see in the exact numbers is from smoothing the curves and some of it is simply because the values are stored in hex format and when you convert them to degrees in decimal format thats just how it works out. Tunerpro does the conversions for you. Also, when you type in a value such a 10 and then read it back I think you get like 9.84 since that is the nearest hex equivalent to what you typed in.

Your engine combo is not that much different than mine (see signature below).

 

OK, i got the SA number thing. That makes perfect sense, and now that you mention it, I remember seeing the "change" happen when I was tuning the VE tables.

Our setups are nearly identical. My cam is the XR264HR-12, so yours is just a touch more aggressive. Is the last jpeg you posted what you're running for spark or was it made up for illustration purposes?

 

[Hey I was just wondering what ecm setup you are using and how you set up your throttle linkage???? Im thinking of doing something similiar on my 350 but with the new edlebrock manifold. Any help would be great. Thanks


quote=wolfmanken;3181796]Hey, Well i got my 383 tunnel ram'd dual tbi setup working pretty good, its winter now so no more tuning for me but i am curious about something.

I need to do some tuning at WOT but iam not too sure where to start especially since all my other tuning is done automatically for me.
right now it doesn't pop or backfire or anything like that but it definetly doesn't jump like it should.

Here is a pic, still need to clean/dressup the engine a bit more[/quote]

 

What I posted was for illustration purposes only. I will post what I am currently running, but consider it for illustration purposes also. You may find it a bit much especially at WOT low rpm for your applications, but it really helped with low end torque on my engine (maybe too much tire smoke if you know what I mean). In addition, I am currently running an additional 3 degrees of PE SA as shown. I suggest you start out a little more conservative.

 

If this works, here is what my spark table looks like. This one is originally from a tbichips prom, but I think it's closer to what I'm going to need in the end. It's not too far off from yours but there is notable differences.

What's the difference between initial spark advance and main spark bias? I have both, initial advance is set at 0 and the bias is set to 9.84, like your inititial. What does that mean?

 

Pre-Tuner

Your main spark table looks like a reasonable starting point. You may want to lower your PE SA a bit until you know everything is safe. The main spark bias is simply added to the SA table values stored in the ecm so that negative SA values can be stored. The ecm substacts it out before using values when developng the SA. Your TunerPro XDF file should be setup to handle the bias so that your display values are the actual spark advance.

 

So in the 30map @ 3600 rpm (36.21) box, the SA is really 46.05?

 

NO, the SA is actually 36.21 as displayed by Tunerpro. The actual stored hex value is equivalent to 46.05 but the ecm will substact out the 9.84 bias so the SA will be 36.21 degrees.

Likewise the Tunerpro XDF file has a conversion routine defined to handle the bias offset so the values it displays are the actual SA.

Al

 

OK, I get it. I'll just leave the bias figure alone so that the table is correct.

So when you were creating your SA table, I'm guessing you adapted an mechanical-style table like you explained to me. What did YOU do to fine tune yours after that? Everyone seems to have a method, I'm curious as to what yours was.

 

Actually no, I started with a stock ANTT.bin for the L03 camaro. It turned out to be a poor starting point. This thing needed a lot more SA. I had to dump a ton of fuel in it to even get it to run. As soon as I started to lean the fuel out I soon learned it needed a lot more SA even to idle. I just kept working from there to give it the advance it seemed to want to run well and make power.
I have yet to try to fine tune cruise for fuel economy because this not a daily driver and yes it does seem to have a drinking problem. Maybe some day when I have time I will try to improve mpg a bit but for now I like the performance it provides.

Al

 

That's the same boat I'm in. This is all in a restored '91 truck that I only drive when it's nice. I could care less about MPG as long as it'll lay down some rubber.

Thanks for all of the replies today. I can't wait to start tuning when I get the EBL next week.

 

Great posts, BTW.

If you want to make it easier, you can just zero out the main SA bias as you probably wont need it, or you can incorporate it into how the SA is calculated.

Heres mine. Needs LOTS of timing as my 350 has dished pistons. Without it, the car is a dog. The timing tables should be a good start, but youll definatly need to get out and tune it.

 

Keep in mind that vehicle weight, gearing, etc, all play a part in the timing you will be able to run.

My Heavy G20 van with 3.08 gears, despite the sick 8.4:1 compression ratio with the swirl ports and stock cam would not take any more than 26* of timing @ 3,600 rpm and WOT. With the current 305 TPI heads and ZZ4 cam, I run 30* @ 3,400 rpm. Starts out with just 4* of timing. Explosive throttle response.

 

with Dimented
I am running flat tops but definitely found the same thing. It wanted much more SA at low RPM WOT than I thought it needed. Yes it was a dog without it.

 

By saying it wouldn't take any more than 26* timing, do you mean you started losing power?

I'm not sure if my pistons are considered "dished" or not. The engine is a crate engine for a '96 truck (so I got the vortecs and roller setup) and the pistons do step down some, so I guess they are dished.

I've been messing with the fuel tables, and I haven't even touched the SA table yet. I guess I just need to get out there and do it to see how the engine responds. As soon as I get my EBL, I'll be a tunin' fool.

At what point do you get into engine damage territory? Before I even touch the spark table, my VE table needs to be closer, which is obviously a big part of burning through pistons. Spending as much money as I did on this engine, I don't want to hurt it.

 

By more than 26*, I mean under sustained heavy throttle operation, it would start picking up knock counts and retard the timing. It also did very little for power to run extra timing. 26* of timing advance is all the combo wanted. Cruise timing was around 40* @ 2,800 rpm with functioning EGR.

28-36* is the normal SBC timing range in the higher MAP, higher RPM areas (heavy load).

 

Ok well iam glad too see that someone took my post and toatlly screwed it up, this post is suppose to be about tuning at WOT not spark advance or anything like that, spark advance is very simple to do.

Now as for what ECM iam using, i bought one from dynamic efi, it came with the ebl board and an extra injector drive so it'll work correctly... also iam not using an EGR or a Knock sensor(cause you don't need it).

But back to the question... whats the best way to tune fuel tables at WOT when you don't have a WB O2.

 

Sorry for the thread jack

 

You asked about how to Tune WOT. You never stated FUEL ONLY. Timing is an intergral part of tuning WOT. IMHO, you got what you asked for.

 

"whats the best way to tune fuel tables at WOT when you don't have a WB O2"

on a dyno that has a WB O2.