Ok, i have read and read and read, and i have tuned and tuned and tuned. my VE tables are nailed, my WOT has been tuned as best i can without a WB (dynoing in january, i testing WOT based on 1/4 mile MPH).

being that i have an LO3, i know my timing table sucks. advancing the whole table 6* really woke things up. but i am sure there is a lot more to be gained by fine tuning and optomizing the timing tables.

i have read many posts on timing, most of them say something along the lines of 'give the engine what it wants' or leave it at 'ramp the timing up'. my question is, how do you know what timing the engine wants, i have seen many posts saying that more timing isn't always better, and tuning by advancing til you get knock counts, then backing it off, is the wrong way to go about it. my question is how do i go about finding the spark curve my engine wants? obviosly 1* in 1 cell is not going to make a measurable diffrence at the track, so how do i find that 1* in that 1 cell, and know it should be changed? most of the answers on timing i have seen are so vague it is hard for me to figure out where to start adjusting, and what changes in the data i should look for. if someone could possible spell out how i am to go about optimizing the timing, with real world, doable answers, i would be greatly appriacitive.

Thanks
John

 

i have been watching this topic closely in other postings. i have KC that i am uncertain if real or set off by the exhaust or a loose sensor. i will check clearance on exhaust. i am considering changing the amount of retard the KC allows. I think it retards 6 deg and may change it to 3 deg and see how that works . my timing curve i believe is stock GM for 84 vette. i have taken out some advance around 30 -40 map 2400-2800 rpms as that is where the KC occurs in quantity. i think my timing can be more aggressive and am giving away HP due to conservative timing. will compare my tables with others that have posted on the forum. i will do some plug readings to confirm no issues with detonation. fuel tables are very good but rich at PE (12/1). i would like to think my engine is capable of more than 222HP/ 268 TQ at rear wheels per dyno. i think i read a post that spark is optimized on dyno as a function of max TQ but not sure on that. not sure if i can hear detonation as pipes are very loud?

 

I wholeheartedly agree that jsut tuning by KC will not get the right results unless detonation occures before the maximum power has been reached. Im not done with my timing curve yet but so far Ive found on mine that the timing was very subjective. I concentrated on one small part at a time and paid close attention to one portion of teh cars operation while i repeatedly ran the car through the same portion of its operation over and over again. I put a previous bin and the new one on the eeprom adn jsut took the car out and compaired the two and made repeated changes untill the next bin in the series jsut 'felt' the best and seemed to give the best performance without having too much timing and slowing the car down or too little and causing the engine to bog. To me it doesnt seem like theres much alternitave to using a certain ammount of subjectivity in addition to track times and such in tuning it since most people dont have brake engine dynos to run teh motor at one spot and see what the best timing is there. Ive also found that theres a pretty narrow margin where it runs the best and going over or a tad under can mar performance. If you can get a good data logging system like a high end g-tech that can data capture it would probably help since you could run the car repeatedly at a similar load each time and compare the results and make decisions on that.

 

I assume you are running a 8746 and near sea level.

I'd start with bone stock timing tables.

For WOT I'd head over to the 3200 - 3600RPM x 95 - 100KPA cells and add 2 degrees to these fours cells and check my trap speeds. Keep adding and checking as it gets faster. When it slows down go back to your fastest bin.

Since 3600 is the last entry in the table, the ECM will use that number all the way to your shift point. Well..... there is a spark slope adder..... It adds a little advance over a set RPM window, say 3600 - 4600 it may add 1.5 degrees.

Now you'll want to work on 2800RPM and under. It will probably be less advance than at 3200RPM and will probably decrease as you approach idle RPM.

 

But isn't telling someone to add X degrees here, not really seeing what the engine wants.

Since the tracks up here are closed there isn't any trap speed comparing, and some of the aftermarket things IE Gtech/Moates... aren't too reliable. I ran 13.7s at the track but moates only said I ran 14.2, while track ET for another IROC was 15.3ish while Gtech said 14.2.

 

It would be if they aren't measuring the engines performance with some repeatable tool such as the drag strip.


The question is not if the Gtech/Vericom/Moates etc produce the same results as the dragstrip. The question is, are they repeatable, do they give consistent results. If so then they are reliable for tuning. If not then find some tools that are consistant and repeatable.