BenDoe

I'm getting close enought on the VE tables to think i can start doing the timing on on my 91 Z28. I'm using a laptop and craig moates free software and was wondering how i go about tuning the timing. Thanks.

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1991 Z28 305 5spd 1LE, TES headers, dual cats, 3 Chamber flowmaster, Comp cams .488/.495 212/218 the usual street racer with a stock chip.
Gained 20HP by porting and polishing my EGR passage.

leirch

Good question, I would like to know of a procedure myself.

Brendan

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1987 IROC-Z L98,SuperRam,EB 6085's,LPE 219/219 Roller, Crane 1.6RR, EB TPI Base, 58mm TB, ADS 24#, AFPR, K&N, EB TES, Catco Cat, 3" Borla Cat-Back, Accel cap,rotor,distro/other crap, MSD 6AL, MSD Blaster 3, Aluminum DS, 94 Disk Rear, Adjustable Valve, Precision 3.73 Gears, Sub-Frame Connectors, Hotchkis Lower Control Arms, KYB Shocks/Struts, Suspension Techniques Lowering Springs, Polyurethan Bushings all over the place, Moog Upper/Lower Ball joints and Tie Rods ends/Idler Arm,

To see the ROC, Check out the webpage Here

Bobalos

I third that. From what I gather from Grumpy, less is more. if that is the case (not that I am questioning you) then this is going to be a VERY tough game to play. as I start to take out fuel I think that I am going to find that there is too much timing. if that is the case then it is going to be steps for me. < Fuel. < timing. < fuel. <Timing. etc.

as the timing table is RPM to MAP, how much is right? In CL the ECM is going to put in X amount & then if it knocks it will take Y out @ Z rate until it stops knocking. how do you base the gain/loss? I can only imagine that THIS gain/loss is actually based on efficiency. But w/o being on a Dyno & calculating BSFC, how do you know efficiency.

I would imagine @ WOT this would be rather "easy", as you can just start taking out timing until the motor starts losing power. or start adding timing until the motor stops making more power (this magic point ought to be before I start hitting knock counts) BUT, that addition/subraction is going to be based on the table that you dont have a reference to as to what is good or what is bad.

the question is, do i start to removing the timing until I stop getting some value of knock counts? OR do I continue to remove timing until some thing else happens (the power drops, O2 drops, what?). on the flip side if I am not hitting the knock sensor @ all do I start putting in timing & see if I start to get knock counts? & then back it back down?

This appears to be a very deep subject, & I am sure that there is not a simple answer. There has to be a yard stick to measure by. @ the racetrack (WOT), it is MPH (aka HP), when you are doing the base table though, what it is?

TIA

BW

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Bobalos
aka Bob W.
www.r71camaro.homestead.com
r71chevy@earthlink.net
&lt;&gt;&lt;

Steves ZZ5

I fourth that notion.

Learning to curve our spark tables hasn't really been discussed in detail.

:: patiently awaits the lesson ::

[This message has been edited by Steves ZZ5 (edited June 15, 2001).]

Bobalos

WOW, no takers? Calling on the big dogs on this one, Glenn, Traxion, Grumpy? who else are the SD dudes?

BW

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Bobalos
aka Bob W.
www.r71camaro.homestead.com
r71chevy@earthlink.net
&lt;&gt;&lt;

leirch

I don't think the Tuning of the spark table is Sd specified. It has to be universal to MAF also.
So anybody, help!

Brendan

Brent

iTrader: (1)

http://www.diy-efi.org/gmecm/papers/tunetip.html

If I understand things correctly, the TPS voltage is your performance gauge during cruise. For example, the less TPS it requires to run 2000rpm @ 50KPA the better.

Or the other way is to test it at 2000RPMs and .89V TPS and look for the lowest MAP.

Bobalos

Ahhhhhhhhhhhh, Brent now that makes sense. If i can put less foot into it to get the same speed & map, then the motor must be making more hp for less foot, for a given load.

In my app I could not go the other way cause with as stupid a cam as i have, i have a better vacuum when cruising down the road than when @ idle so, using the first idea would make more sense for me.

BW

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Bobalos
aka Bob W.
www.r71camaro.homestead.com
r71chevy@earthlink.net
&lt;&gt;&lt;

TRAXION

I've been watching the progression of this post. I don't have the time to write a post on how I tune the spark curve (heck, look at how long the P730 fuel tuning post was ). However, that is kind of a moot point anyhow because in contrast to fuel tuning, spark tuning can be done several ways. Each programmer has their own 'special way' of tuning spark. There are some 'popular' methods. However, one would have to discuss all popular methods or else the author will be opening himself up to some interesting comments What I propose is a discussion on theory first. By theory I mean ....

1) Some people tune by the most advance possible. Pros/Cons?
2) Some people tune by the most advance - 2 or 3 degrees. Pros/Cons?
3) Some people tune by the least advance possible. Pros/Cons?
4) Some use the knock sensor during the tuning process. Pros/Cons?
5) Some use spark plugs during the tuning process. Pros/Cons?
6) Some use the KS and plugs. Pros/Cons?
7) Other chit

Personally, I admit to being aggressive on the spark curves (part throttle and WOT). I have learned to not be TOO aggressive (thanx Bruce!) but I still consider myself pretty aggressive.

These are my initial thoughts. I'll share more as time permits but I am pretty busy with extracurricular activities (ice hockey, softball, wife, gym, car, e-mail, other boards, e-mail lists, etc). At the same time, I would like this to be more than a one-sided conversation with me explaining and others listening. I need to grow too

Tim

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TRAXION's 1990 IROC-Z
Best Time = 12.244 @ 112.51mph (1.778 60' / 7.819@88.32mph in the 1/8)
All Natural. No Force. No Drugs. Stock Bottom End. Stock Body Panels.
Gunning for NA 11's with bigger cam, bigger stall, and bigger exhaust.
-=ICON Motorsports=-
Moderator: PROM board at thirdgen.org

[This message has been edited by TRAXION (edited June 17, 2001).]

Grumpy

Take a bin.
Make sure the timing matches the base timing in the chip.
Subtract 3d from all the table entries.
Move the timing around in the idle areas, and see if that improves the idle.
then try driving,
you shouldn't see any retard at any time. If so do some data logging to find out where it's occuring.
In the cruise areas, work the timing and fuel up and down to get the min TPS for a given road speed. 1.0v at 70ish is acceptable.
The start feeding some timing into WOT, ALL THE TIME MEASURING Performance, GUESSING WILL MELT A MOTOR. Buttometers are a waste of time, general rules
AL head (58cc chambers) 28d
Small Chamber Iron 32ish
Large MAYBE as much as 34.
Often with EFI you don't need as much timing as a carb'd motor.
Then you want to take as much timing out as fast as possible without having a sag from cruise to WOT.

Then during overrun you want very little timing

Just off of the top of my head a general shape would be (ie about 2,400 rpm)
20K/Pa 100K/Pa
18 36 38 34 32 27 28 26

If this was with AL heads probably be close
assuming no WOT spark adder.

this is just a pointer to get ya going

Bobalos

[QUOTE]Originally posted by Grumpy:
Make sure the timing matches the base timing in the chip.
~ what do you mean, check to see that the the timing is set right? (ie 6* BTDC, on my motor)

The start feeding some timing into WOT, ALL THE TIME MEASURING Performance, GUESSING WILL MELT A MOTOR.
~ Until when, the HP gain stops? or the motor starts to knock? or ????

~ All the while observing drivability, to prevent a sloppy tranistion into PE or through the RPM range w/o PE, right?

Then during overrun you want very little timing
~ Sorry again, what does this mean? what is overrun?

Thanks Grumpy, I know testing, testing, testing. Sounds like your gold standard is the least Trottle position for the same Vac & MPH. this does make a lot of sense.

BW

Bobalos

comments/answers Grumpy?

BW

Grumpy

Assuming your starting with a low amount of timing make a base line pass with whatever timer your going to use. The start bumping the up, watching for detonation on the plugs, and noting the performance changes. going in 2d steps should be enough of a change to see a difference in performance, if it flattens off add some fuel. If you see a trace of detonation see if adding a little fuel cures that. If not then take the timing out, and the fuel, you just added.
just have to wor back and forth on timing and fuel, not easy way to get there. Then when you think your done take 2d out at WOT, and see what changes there are. If none then leave the calibration alone. The old flat head ford tuning idea of max timing, and max fuel are just outdated. If your running for money or have money to waste then the ***** to the wall tuning is fine, but not on the street. There are just tooooo many variable on the street

Overrun, closed throttle at any engine speed higher then idle

TRAXION

"***** to the walls tuning" ... I kinda like that (even if my motor doesn't) j/k, j/k ... I've learned.

Tim

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TRAXION's 1990 IROC-Z
Best Time = 12.244 @ 112.51mph (1.778 60' / 7.819@88.32mph in the 1/8)
All Natural. No Force. No Drugs. Stock Bottom End. Stock Body Panels.
Gunning for NA 11's with bigger cam, bigger stall, and bigger exhaust.
-=ICON Motorsports=-
Moderator: PROM board at thirdgen.org

Bobalos

Tanx, that helps to clear things up. When I think about it this is both logical & intuitive, but when you cant discern what variables to eliminate, & which ones to concnetrate on the matrix is just too complex & overwhelming (Kinda like searching through the DIY archives, If you know what you are looking for, you can find it).

Tanx again.
BW

MonteCarSlow

I have been doing this, but I don't notice a change in TPS voltage over a 4 degree range. I do however see a change in MAP voltage. If the TPS is not changing, should I aim for lowest MAP voltage?

I have a heavy car with lots of gearing (2000rpm@55mph), 5.0L/TPI with AL heads (seems to like 41 degrees at cruise, or about 3 less then stock AL head 350 timing)

Grumpy

You missed the boat somewhere,
the Vette AL D port heads like lots of cruise timing and a very limited amount of WOT timing.

It's working time and fuel together. But the post was timing specific.

If your running a distributor application then you have to look at what the cutoff timing advance is in the ecm. Some distributor applications have a limit of 41d total timing, in the math.

I've seen some cars respond well to as much as 51d timing but that is reserved for DIS stuff.

Damon

Grumpy- compared to recurving an old mechanical distributor, would I shoot to basically replicate the curve I used to build into the distributor's weights/springs, etc.

Forget part throttle for a minute, that's tricky stuff. I'm talking about just getting the WOT curve pretty close. I used to shoot for something like this at WOT:

14* advance at 900 (the "base" timing)
34* by 2800 (that's 20* worth of centrifugal advance on top of the base timing)
no more advance beyond that point vs. RPM.

I found that the RATE at which the advance comes in has a big effect on torque production. I suspect the stock programming brings the advance in kinda slow, just like a stock mechanical distributor would with tight advance springs, leaving room for performance improvement with the proper reprogram (a faster advance curve).

If I'm anwyhere near sane on this (you decide) I think I may have lost my fear of burning my own. Yes? No?

19doug90

ive just started getting into this, same as the rest of you get the VE table close then start playing aroudn with spark.

I was starting from a stock 8d 350 ecm.

Firstly traxion mentions a bunch of various methods that people use for tuning the spark, i think as a newb im probably using a little bit of all of them.

its a pretty simple formula, where ever in your rpm band theres more fuel, youre going to want more spark advance.

the method i used was to smooth out the spark advance curve, and move where the timing was around so it suited the power curve of my new cam better.

basically just started adding timing until i noticed that i was getting knock retard, then backed off until the knock retard went away. It's helpful to have someone in the car watching the datalogging so if you get knock retard its noticed right away (if its slight itll only happen for a second) and you can back off on the throttle until you burn a new chip with less timing.

for performance youre going to want to advance as far as you can without any retard.

KNOCK COUNT - with tunerpro the knock count will be a random number of w/e it detects on startup. This number will not change unless you get a large amount of knock retard. If you notice your knock count going up its time to baby it until you can get a new chip with either less timing or more fuel, whichever it is the motor needs.
i didnt realize this was the case and pulled about 2 degrees of advance from the entire upper half of the table to try to get rid of my knock coutn of 42 and the car just ran like poop.


on top of this once youve got as much timing as you can put in without any retard, its a good idea to check your plugs every now and then for "speckeling" little dots on the plug are specs of your piston coming apart from detonation, thats bad, back off the timing a little if you see this.

another note is since i went to a larger cam my powerband was a lot higher up then it would have been stock, when i was tuning the ve table i had a really bad stumble/hesitation between 1600-2000 rpms but wasnt getting a knock retard reading. At low rpms if you have too much timing it can make the motor just stumble all over the place. I pulled a little bit of timing up to 60 kpa out of the 1600-2000 range and the car is as smooth as can be now

Cflick

It's an old thread, but apparently still valid for too many. ( OK, me )
Thanks for bringing it back to life.

Not necessarily dead on, but within reason. It's gonna change.
Fight the urge to go back and forth between spark and VE. It's gonna change, but do one thing at a time. In closed loop, yeah, the BLM will wander a bit, but as long as it's in closed loop, and not hitting the BLM limits it's running at 14.7 AFR. Let the computer help you. Worry about fuel after you settle ( for a time ) on a spark strategy.
( with reservation in WOT or PE at any time )

We all have our preferences, beliefs, and methods.

I'd tend to disagree with that. True, an overly rich mix will tend to burn slower, but here's where excess spark can be masking an over rich condition, or the over rich can mask too much spark, so be very careful with that line of simplistic thinking.

Yeah, well, I developed a whole timing map from scratch that way. I was happy.
Then, I did a "reality check" by comparing to something ( several, actually. There are no maps for this block, but there are 12 factory distributor curves, and 14 initial settings. None of which match MY collection of parts, but.... ) basicly "stock" specs for the *block,* threw my "scientificly developed map" out and started over.
Things are much better now. 20% better mileage, more torque ( obvious ) and cooler.
Apparently the engine was *not* happy, even if I thought I was.

I've no problem disagreeing with that !!
Grumpy said many times, you want the LEAST amount of spark consistant with performance. I'm pretty much in that camp. Back off a degree or three at a time, until performance begins to drop. Then, leave it alone, and go back to fuel.

/snippage/

Yeah, been there, done that. Pulled WAY too much chasing a knock from, I don't know what, but with a reality check, and a realistic curve, it's gone, and the engine is cooler.
Probably, I was getting knock from just plain heat, but I don't really know.

TRUE, and with no evidence of knock. It's not detonating, just trying to run backwards.
This happens if you try to go with as much advance as possible without knock.
DON'T TRY THIS AT HOME !! ADULT SUPERVISION REQUIRED !!
I've experimentally run my 455 with as much as 75 degrees advance, as high as 6K RPM, but with NO LOAD !
All it really did, was prove that as much advance as possible doesn't work. Yeah, it runs faster with less throttle, and didn't detonate, but sure gets hot ! REAL hot.
Kinda proves the "as much as possible -2 or 3" doesn't work either.
I'm in that "only those who go too far truly know how far you can go" camp.
AND I do these things with the full knowledge that I could well make a 2 second $10K mistake. I'm kinda counting on the knock sensor to prevent that, but it may not.
A several second mistake ( twice. I ride the little bus to school ) cost me upwards of $600 in cats alone, so far.
Personally, I try to avoid plug cuts, for two reasons.
1. I'm old, and lazy.
2. I'd prefer something that warns me of a problem before damage is already done.
( note: avoid, not ignore )

These days, I'm into in cylinder pressure measurements, but don't yet have a fool-proof method. Ion traces are showing good promise, but it's still very early. WAY pre-prototype at this stage. ( my stuff. Saab has it OK )
What anyone can do, is their own data gathering, and note taking.
Do 5 or 10 runs with a particular burn. Take out two degrees, and do 5 or 10 more runs. How's the average performance of the first ten compare to the average of the second ten ?
That works. I'm just looking for a "better" way.