how much advancing is possible ?

[spatz]

hi folks,

still playing around with the LS7 and my map and figured out that power is really !!! increasing with advancing.
I reduced to 28 to 30 around what I am at in the third gear flooring the throttle and I had a lame stuttering engine
when I got back to 38 degrees WOW that kicks the stuttering almost gone away. So now
the question is if I push the advancing at the middle of the map at average throttle (MAP) and RPMS
even further ?
What is the next experience when going over peak power ?

I can imagine that is how AS is tuning the old blocks to the high HP ?
If anyone is interested I can make a screenshot of the advancing ignition map.

regards

[harry b]

You can advance as much to the point where the edges of your pistons start to meltdown.

Oldschool stuff.
Lower compression in order to be able to advance timing more, gives net result of more power at the cost of loosing lowend torque.

So it's a choice what kind of engine do you want?

Edited by harry b on Tuesday 29th March 21:35

[738 driver]

hmm...... GM's fast burn heads/high c/r engines are designed to run less timing and hence improve power (spark nearer TDC).....one of the main reasons they perform so well and return mpg..

If you run a lopy cam on fast burn heads you can run more initial timing so long as all else is in harmony ...

[spatz]

ok I somehow expected this kind of answer, always two sides of a medal there is. I will see a professional roller in the next weeks and see if I can get rid of the stuttering completely, changing advancing forward from 35 to 38 in some area of the map already improved both power and engine running.
So if you risk the health of your engine how do you know when you reached the best setting ?
I learned that the industry has to map engine for different fuel qualities and therefore there is a band of values not really an exact straight line ?

thanks

[GTRCLIVE]

Before playing with your Map I strongly recomend you reading a book on the subject first, very easy to kill a good motor with a Bad mapp.

http://www.amazon.ca/Engine-Management-Advanced-Gr...

This book is very good and easy to pick up, it says advanced but it gives a very good account of how you should mapp an engine from start to finish with lots of tips along the way.... worth every penny

[macgtech]

We found we had to remove a LOT of fuelling at part throttles and low revs to make the car run well, and increase it at full throttle and high RPM. The map we started with was a 'standard' Mosler map which ran like a dream on the dyno.

Obviously depends on your intake and exhaust arrangement too. We found running closed loop lambda makes it much easier for the final 10% trim.

[spatz]

yes my map was created on a dyno as well not in the car, and it pretty seems that it really makes a difference, will look for this book, thanks clive

[spatz]

received my tuning book, thanks clive for the hint, i noticed when increasing advancing that my lambda reports a little richer values which is conistent with what the book is telling. However I understand you get the most power if you go close to knock, do not have a knock sensor fitted nor does the DTAFAST S80 support one. So the question is how can you detect early knock ?
Is anyone here that has been tuning a stock LS7 ?
How good is a map that has been created on a roller, still needs touching up in the car driving ?

thanks

[deadscoob]

You could get something like this:

http://www.linkecu.com/products/TuningTools/g4-kno...

[Gulf LS3]

Hi Spatz

As 738 says, 38 degrees will destroy your nice 7 very quickly. What cam does it have fitted? If standard or close to then she should idle like a swiss watch and pull through to 7000rpm. The Knox definately give a lot of protection on a Gm setup but the Gm map goes nowhere near 38 degrees.

The standard map runs upto lambda 1 till 3500rpm then fuelling increases all the way to the redline with just under .80 lambda at the top end, the standard Gm map is rich up the top end to protect the motor, cats etc.

[spatz]

according to my supplier it has a stock cam, and I have been working on the map again yesterday and am using values
between 36 and 38 in the middle of rpm range and Manifold pressure. I tried 28 just for testing and the results are awful misfiring and no power.
It has improved a lot and the misfiring has disappeared with the mentioned values.
I will now work on the fueling which is quite perfect according to my recorded lambda values and mainly increasing at end of the range as I am aware about the enrichment for higher rpm and then try to reduce the advancing to be on the safe side.
According to the book the velocity density based maps as mine could have up to 20% being impacted by flow through intake and exhaust.
Kyle be aware that my engine has a Wilson manifold with 4 barrel throttle body with cold intake and this alone makes a stock LS7 very different to mine.
What lambdas are you running on the charged LS3 and what advance timings ?

[spatz]

one more thing I am tuning with 95 octane fuel and advancing has to increase for higher octane fuel as burn rate is slower. Also have ordered a TPS for my throttle body, so I can use the transient fueling function ot the DTA ECU. Should further improve the response to fast changes in throttle.

Edited by spatz on Monday 4th April 08:05

[738 driver]

Worth putting a temporary timing mark/light on there Spatz, just to be sure what you are reading is correct....seen photo examples of reluctors out by more than a degree or two .. To be fair its not uncommon to see aftermarket ECu's getting away with a couple of degrees more advance than a factory controller, quite why I dont know? But for sure stock LS setups usually run around 27-28 degrees peak advance, the intake should not really have that much influence on flame speed at similar RPM, a cam, non stock heads or C/R maybe..
Setting a blown motor up which was far away from stock in internals, cam or intake saw the best at 28-29 degrees of advance on an aftermarket ECU and premium pump gas ! This was 2-3 degrees more than we would have expected on a GM controller. So even with serious mods the LS's Ive seen are pretty consistent on timing ! Even on a highly modded LS's you can run considerably more timing before detonation occurs but the torque always drops off...
Id double check your hardware first.

Good luck.

[spatz]

ok many thanks,

for the hint, I understand that figures in the ECU map are mereley representing a hopefully consistent relationship between cam position and advancing.
I can imagine that most tuners are using the original GM controller and I totally believe that your values are common ones.
I am not an expert but had misfiring under certain conditions (part throttle hard accelerating). The original map is somethimes having values of 40 for low MPA values and low revs. Increasing the timing by 2-3 degrees has improved a lot, and I also tried 28 which was giving extremely poor results.
So this DTAFAST ECU obviously seems to be different than the GM controller.
BTW I had no torque decrease with the new advancing but quite the opposite, more power.
Once I think I have everyhting optimized I will post MAP/fueling and MAP/advancing tables here.
BTW the book is telling me that advancing actually should increase with more REVs, is that true for GM controller setups ?
Does anybody have an advancing or fueling map of a stock LS7 with GM controller ?