How do you know when you retard timing too much?
 

All,

I got a hold of a bit of software to tune the fuel and timing advance/retard on my supercharged 3.6.

When tuning, how do you know when you retarded the timing too much? My butt dyno is not that sensitive to tell the diff.

I do have an egt gauge. Would this tell me?

thanks,
anthony

Too much ignition retard = unburnt fuel = overly rich AFR's.

If too retarded = not happy. Easiest to hit the dyno and check with power output. When you hit the most power pull back couple off degrees for safety. Just IMO.

Get a timing light. A generic 12volt strobe light bulb one without the adjustable advance delay knob on the back will do fine without any added confusion or MSD multiple spark issues some of the lower quality adjustable ones have and hook it up to the number one spark plug wire according to the instructions.

You can clip the 12 volt supply wire to one of the fuses on the left rear relay panel thats hot while the ignition is on and the ground clip to a left side motor mount bolt or whatever works.

Without a timing light you're just guessing. The stock specs are on a sticker on the bottom of the engine lid or in the owners manual.

Engine runs hotter and down on power.

BTW, be very VERY careful adjusting critical engine parameters using the "butt dyno"... you don't want to screw something up and destroy your motor, otherwise your mechanic will be lubing your butt for some serious raping of $$$$$ to rectify :eek:

I am being conservative and taking some timing out. I can feel the engine down a bit on power when taking timing out.

How does ignition retard causes unburn fuel? Does this happen only for severely retarded timing only and not the 3-5 degrees or so that I'm taking out?

+1. That's really the only way to do it right.

Why dont you start where Porsche designed the stock ignition and go a little bit forward from there?
You can get a hold of ignition curves off this site or the owners manual so you know the timing parameters and then just modify your starting points, meaning idle timing settings, to advance a little from where the factory set things. The factory set idle timing retarded to improve emissions and make the car run hotter at idle at the expense of power and low speed response.
This would give you a baseline to start from. Only way to optimize is like said above post on a dyno. This takes lots of money in tuning time....which is why alot of guys in the know dont offer up details.

This might be an opportunity to try the Dynolicious app for the IPod Touch. Change the timing and make acceleration runs to determine which value yields maximum torque.

Here's a screenprint of part of my ignition map, about 12 hours of dyno time in there. I can screenprint other sections of the map and the fuel map if you want.

I get no knocking at all, we kept advancing until power peaked, then pulled a degree or two.

This is a supercharged 3.2 with intercooler. Twinplugged, about 11 psi boost.

hope this helps

http://forums.pelicanparts.com/uploa...1322792825.jpg

John - where do you get your dyno tuning done?

same here, got a guy down here with a mustang but he says my car sits to low (ground to headers) to fit on the rack... Actually trying to hook up with a TO guy with a dynapack portable. Dyno day?

My dyno time was all in castlereigh and brook vale, NSW Australia. We never had a clearance problem, and the car is very low. Are your heater boxes hitting the rollers? I don't have those...

After the dyno I did at least another 20 hours in transient throttle and other fine tuning. Still working on an oscillating idle.

How consistent can you be with launching the car using the iPod app to get accurate 0-60 times?
You would need to be very consistent to eliminate roll out variation and when it triggers to start a run wouldn't you?

I dont think this would give the accuracy he is looking for. Might be good for ball parking.

Interesting ignition map. If I read it correctly....
1) at idle you are around 16 degrees BTDC?
2) at higher rpm low load cruise you are around 40 degrees BTDC?
The numbers seem higher than is normally acceptable by most guys (from forum discussions) and definitely way more advanced than a normal 930 with factory ignition runs stock. Not knocking your info, Am I reading it wrong, just want to be sure.
Thanks for posting the info in such detail, this is the level of detail I always ask for to really help with tuning and find hard to get.

Hello Fred,

I'll have to look at my logs to verify where I am at idle...I have idle set at ~1250rpm but I dont recall the static MAP at idle.

This is a race car only, I spend no time at high rpm/low load. I spend most of the time accelerating/flat on the throttle or backing off/into braking. That said, I do log knock and have never recorded a knocking event except where I induced it on purpose to test the sensor.

I agree, these advance numbers are much higher than I had seen before, but the dyno pulls were very consistent and thorough...we did many, many pulls and kept pushing the ignition further until power fell off, then backed the figure up. Again, on the dyno no time was spent cruising, it was all on/off throttle.

The vast majority of forum information on these cars is for turbo application, I've found very little on supercharged applications like mine. Some differences might be;

1. maybe the timing mark on the pulley is a degree or two off (retarded?) This is a custom pulley to drive the charger and alt/fan.

2. My intake temps are quite low compared to many I've seen on the forum...firstly the supercharger has different heating dynamics to a turbo, where it is exposed to exhaust temps. Second, I have a custom intercooler by Bell, and a pair of "puller fans" shrouded to the underside of the intercooler that switch on whenever IAT exceeds 20 deg C.

3. I am also twin-plugged, run modern injectors, have ported heads and different cams.

Maybe any one of these or a combination of them contributes to the high advance figures. In any case, the dyno doesnt lie ;-)