just about to start burnin proms.....need guidence on settin a spark tabe...not sure how to go about it!! can anyone help or show me were i can find help?? thanks

 

Basically, pull 2-3 degrees from entire table after the idle area.

Then drive and monitor for knock and remove timing accordingly or experiment with adding more and noting results.

Then use the table that gives you best WOT performance and cruising mileage and throttle feel

If you are not running EGR, you should automatically take 2-3 degrees from all cruise areas, maybe more depending on the combo.

This should be done only after your fueling is dialed in and the WOT stuff only after you have checked it with a wideband or the like so u know your AFR is in a safe range.

Some good notes on spark tables above and if you do a search, it should net you some examples, however I caution u from using a table, because it looks "good".

later
Jeremy

 

I realize my 94' Suburban is much heavier than a pickup, but spark was the biggest change I had to make. By monitoring the knock degrees taken out, I ended up removing from 5* to 15* of SA from the AUJP bin at heavy part-throttle and WOT.

I could not believe how little advance it wanted. Going against what I was sure the engine "needed", I gave the engine what it "wanted". I think we have heard that many times before .

With the TPI in my 94' Suburban, I get about 18 mpg on the highway, and that's a steady 75-80 mph.

TPI Conversion - Tuning

Ed

 

I have that same thing occuring to me on my vortec headed 383 in my Formula.

Thing doesnt like over 28deg WOT and like mid upper 30's at cruise but anything past 60kpa it likes less timing. Down into the lower mid(25) to low 20's

Its getting to the point I'm thinking Im crazy lol

But the car is getting smother and smoother it feels.

Just goes to show you what 2 tons vs. 5-6tons can do to a spark table as well as converters and gears.

I avg 21.7mpg highway, loaded car and windows down. 600 miles each way. That was fresh engine no highway mode etc.

U have a nice site there Edge, u got added to the stickies up top in one fo the rounds :-)

later
Jeremy

 

ok should i start with the fuel tables first or the spark.....right now im runnin vary lean at wot so there not goin to be anymore wot intell i get it runnin in the safe range! EDGESz28-----with your burben does your spedo read right? is so how did you get it to read right, ive messed with my DRAC and im still like 12-15 mphs off and 200-600rpms. also are you runnin your cruse control, if so how did you get your cable to fit and work?


right now as my tune is im gettin just over 16mpgs. but i just have no performance, my mother had a 91 z28 i drove it a few weeks in hs and i could smook them off the line for ever .....alll stock..... and my truck will brake them loose but i cant get it to roll smoke like the car did at all, and i have lot more performce in my motor. granted i didnt have a posi or gears and so i couldnt use my 2200 stall at the time i only ran a 16 flat at 84 in the 1/4, from what ive seen and been told i should be runnin mid-high 14s low low low 15s with what i have in it. just bummed!!!

 

On my TPI 350, I had to radically alter the timing table from so stock so don't be afraid of pulling more then just 2-3 degrees out.

3.8TransAm: I thought I was the only one with nutty timing on my engine. Mine likes 32* cruise and 18* wot. No VE or PE tuning done yet... (enough work just trying to get the stock cal to stop rattling the engine)

 

My speedometer reads correctly because I never touched those wires/system. My VSS is like 128,000 ppm and goes to a buffer, that in turn feeds the speedo and PCM. I could never get the buffered signal to the PCM to work with the 727 ECM I installed to run the TPI. So I finally broke down and bought the Dakota Digital buffer. This works great. I could read the vehicle speed the ECM sees using my Auto-X-Ray scanner and adjusted the DD box to read within 2 mph of what the speedo reads (which is correct).

Click on the picture below for more details:



Cruise Control: In order to install the factory Suburban cruise control cable, I had to cut off the original press-in fitting and install a smaller fitting. I used parts left over from when I installed a universal Audiovox cruise control system on my 1981 Camaro. Be very careful if cutting so that you do not damage the cable itself. I don't have any pictures on my site, but I can take and post some later if you would like.

For me, I am not an experience tuner, actually far from it. I found it easier to tune the spark table first. For the most part, since my engine is basically stock, the VE table needed little adjustment. I used Datamaster and their Histogram feature with Excel spreadsheets to tune the VE tables. You can see how I did it at http://www.edgesz28.com/edgesZ28/sub...-tuning.htm#ve

You can also see my spark table as well: http://www.edgesz28.com/edgesZ28/sub...-tuning.htm#sa
But remember the usual disclaimer, use at your own risk. I have it posted to emphasize the drastic difference between what my Suburban wanted and a stock AUJP file. And, my custom Street & Performance chip was a slightly modified AUJP file, which actually had more timing put in! Those clowns knew my custom application was a Suburban retrofit, yet I got an off-the-shelf "custom" chip. The spark table alone is what "forced" me into DIY-PROM. I had no other choice.

Good luck, Ed

 

Heres what I would do:

Pull 3 degree from a stock table, use aujp or anjf values.

Take for a drive and note any areas that have more than 2-3 degree if knock in them thru logging.

Datalog while testing for this so you can begin working on your fueling.

If you have some slight/minimal knock I would then begin working on all of my fueling.

After you get the fueling into the 120-135 range, then I would shift back to some work on the timing table and under higher throttle loads.

If u have a wideband, it wouldnt hurt to make sure you are indeed seeing safe AFR's.

Basically repeat as you go. Would worry about getting fuel safe and around the 128 region before I would go after the spark tables whole hog.

Just dont play with timing then fuel then timing then fuel.

U will go in circles.

Fuel first(with the exception of yanking timing from entire table and noting any other areas with excessive knock)

Then work timing

Then work fuel again

etc.

Timing changes fuel required etc. Work the table over completely then shift from one to the other, if u bounce back and forth in the same session/bin you wil run in circles

later
Jeremy

 

As far as my timing tables go:

I run a mild 383 built for boost, currently NA

8.67-1 comp, vortec heads and TPI, 3:23 rear gears and a Vigi

I run like 35-36ish at cruise(no egr) and by like 60 kpa my timing is into the 25-26deg range

Ramps out very quickly.

WOT I do end up running about 28 deg total

I was always getting knock if I accelerated form a lite and kept it at 2500rpm, would knock a little in 2nd and then more once into 3rd.

Kept pulling timing and car got smoother as I drove it.

I know the fueling is safe at cruise and WOT, so I spent a few hrs in the middle of the nite(no traffic) and just kept playing.

Going to do it again soon for more backup testing.

The stock bin's I have used tested have knocked on every car I have ever seen stock lol I'm always amazed at people jacking up the timing. It works, for a little while :-) But eventually that will catch back up to u. My GTA ran its best times ever pulling a decent amount of timing from the stock bin and only having like 26-28 total at WOT.

later
Jeremy

 

reading this post changed my entire outlook on spark table tuning. I was under the impression that you wanted to bump 2-3 degrees of spark INTO the spark table and then monitor for knock. Don't you want the most spark advance possible without knock to achieve the most power? I'm confused.

 

Doing timing isnt a mystery.

Its simply about giving the engine what it wants(that was for you Bruce:-)) lol

General consensus for a stater timing table is to remove 2-3 degrees from entire table and start your tuning efforst from there.

Work on fuel first and get to that 128 blm(close as humnaly possible at least)

Then do more datalogging and take notes. If while doing fuel u notice some bad or cinsistent knock, I would address those areas.

As far as "tuning" your timing tables after u have a safe fueling table, it comes down to eliminating knock first.

This may be too little fuel or too much timing or vice versa, just depends on the app and overall combo.

Then u want to use the timing curve you put together that makes u go the fastest with the least amount of timing possible.

Here is an example, say you run 28deg WOT and say 12.8AFR as a test.
Above example runs equal to 34deg WOT and 12.4AFR(might like a litte more fuel cause of more timing)

U would want to use the 28 deg at 12.8 Its just as fast as running more timing with a slighltly richer mixture, but puts less of a "beating" and heat into the engine.

Lots of good info in the "tuning guide" sticky up top for timing and fuel related questions.

Side note, I have yet to see a stock near stock TPI car(assuming TBI the same) that didnt knock on a stock calibration.

later
Jeremy

 

That makes good, good sense.

The thing is that I'm not running a stock motor. It's a SBC 406 with 350 fuel injection heads, intake, & TB on it. Based on the heads, I think I'll start with a 350 spark table, pull 2-3 degrees out and go at the fuel.

At the moment, I have a 454 spark table in there and it runs pretty darn good (no knock counts). The AE tables are an average of the 350 & 454 tables (454 was too rich).

I built a stopwatch portable dragstrip device over the winter. I think it's time to hook it up....The seat of the pants dyno is sometimes out of calibration.

This is when emulation is handy.

-mike

 

You might want to take a look at David Vizard's cylinder head book or SB chevy book. It talks about head design and how it affects timing.

The vortec head requires less timing because the burn is better. I run old 76cc smog heads that have a poor chamber design and therefore I have to run more timing to make horsepower. More timing is a band-aid for ineffciencies like the heads I use. Well, at least that is the way I see it. In general, you want to run the minimal timing possible to make the most horsepower.
In a 3800 pound car with steep gears and street cam, I added timing to the stock AUJP $8D bin. Every situation is different.

 

Spark isn't all that mysterious once you are able to visualize what everything is doing inside the combustion chamber. Imagine that the whole engine breathing, the RPM, fuel burn speed (depends on mixture quality), dynamic compression (intake valve closing is after piston is moving up), and the quench design. That in a nut shell are the most critical parts that restrict how much timing you can run. Cooling does have an effect but that's usually after you've been in PE/WOT mode for a while like in 3rd gear or a very heavy vehicle. Then you need to run less timing to keep the combustion chambers from getting to hot and pre-igniting (which leads to detonation).
Generally speaking a true SA table will increase steadily with RPM and decrease with intake manifold pressure increase. Then there's deceleration to consider, don't want too much timing or you'll go through brake pads at every other oil change. There's also PE mode and which gear you're using. Like I said before, you can add timing with high gear multiplication because you won't be building as much heat into the combustion chamber as you would with other gears. I only know of one code that has this feature .
Other than that, try and consolidate your SA tables to a main table (no PE mode SA) and the coolant SA compensation. I've found working with just those 2 tables you can get tunes near perfect.

 

The thing that makes the PE spark advance nice is if you have emissions. You can keep your power and keep your NOx low on the dyno emissions test. As another plus you can keep your engine from pinging under stoichiometric air/fuel mixtures while the engine is under higher load. When you mash the pedal the air/fuel mixture will richen up, the TCC unlock, and you can use the extra timing.

 

i have never done anythin like this befor at all.......all this talk is scarin me a lil, im thinkin i need to find somone that knows a lil bit of what there doin at least so i dont do somthin bad to the motor!! but then again once i get my prom burnin softwear and parts and sit down to look at it, ill find that its not all to to bad. right now its just all the talk im gettin overwelmed!! i just cant wait for the final outcome!!!!!!

 

When I did my fullsize van, I used the factory spark curves from a 1981 G20 305. 6* initial timing, 0* centrifical advacne at 1,500 and 24* centrifical advance all in at 3,800 rpm and 0* of vacuum advance at 5 in/hg and 16* @ 10 in/hg of vacuum advance. It ran very smooth, had decent power, and got good mileage. From there I added 6* of PE spark at rpms over about 3,500 to compensate for the VE curves of a stock engine (helped extend the RPM band and didn't run into detonation). At lower speeds I was able to get away with 2-4* extra on cheap gas before the knock sensor registered any knock counts. To finish up when I turned the EGR on I added 4* more to compensate for the EGR.

I eventually came back and changed the tables somewhat. I started advancing the timing a little earlier in the main table and eliminated all PE spark below about 3,500. I took the PE spark table to 4* at higher RPMs. So in other words I started the centrifical advance at about 1,200 rpm and ended around 2,800 and added about 2* everywhere in the table.

For being a 5,000 lbs truck with a 305 this thing scoots.

 

Ahh, grasshopper, you knowledge far exceeds your years......

 

They work in concert. You have to work back and forth between the two, or you'll probably wind up missing the tune. The SOPometer, generally thinks too much timing, and too much fuel feels better. All it does thou, is knock the corners off the pistons.

 

I was wondering about some details that I didn’t see on your site (I have a 92 K1500 Blazer and most of the parts to do the swap sitting around but figured it would never be worth it):
- you stuck a rebuilt/crated engine in it, how close is it to the stock 350? What heads does it have?
- I think from your site that you ran that engine with the TBI, edelbrock and TPI setup, you’re saying that it’s getting about 18mpg on the highway, how did it to do with the other setups, especially the TBI setup (I don’t get nearly that on the highway)
- is it a 4x4? What size tires/rear gear?

 

is this on good gas or 87 octane? Where do you live?

My Formula 350 with a stock spark curve on just about anything in cool weather, but dies knock a little on 87 in warm weather and even some on 89 this time of year, but it’s not enough to notice without a scan tool. I have dragstrip runs that show a knock count here and there (especially on the shifts) on 87 in august, but nothing major/unexpected. My crossfire car seemed to be more sensitive to brand then octane.

SOP meter likes too much timing and fuel… possibly because extra fuel tends to fatten up the torque curve and timing adds responsiveness? It’s not otherwise quantifiable? The car doesn’t run faster at the dragstrip? (I know that you’ve said this before and I’m just trying to understand exactly what you mean by it)

 

My G20 Van with the 270 RWHP TBI 350 was getting 17-19 mpg on the highway. My 245 RWHP 305 is getting 21-23 on the highway and averaging 18+.