Spark timing question

[JMD0346]

Ive been playing with my predator a little today. I noticed that cruising at around 2000 rpm @ 40 in 4th the spark is reading as high as 50 degrees advance. This is with a small amount of throttle input. If I add more throttle it starts to drop. If I let off the throttle it drops to 10 degrees.

Is this normal? Is 50 degrees normal?


Michael

 

[tv's 03]

Based on my datalogging, yes its normal. The a/f is also lean. But the engine load when cruising is low and there is not a lot of fuel going in. Its more than likely a way to acheive good fuel economy and emmissions

 

[JMD0346]

Yeah that makes sense. i know about the lean fuel part. Ive just never had much dealings with part throttle spark. I just want to be sure mine isnt all out of whack.

Im supposed to have 23 degrees at WOT. Im gonna go out later and check that. I had my son in there earlier so couldnt do it.

When you go WOT does your timing climb gradually or does it shoot right to 23 when you hit it?

 

[NotoriousGT350]

When you go WOT does your timing climb gradually or does it shoot right to 23 when you hit it?

Good question. I want to datalog my cobra and see what the spark advance is reading when I'm in WOT. I'm hoping for 23*. Guess I'll make some runs tomorrow sometime.

 

[golstho]

it is normal. i think 52 is max in closed loop. under part throttle in 4th you would be in closed loop so this is normal. once you get into the gas harder and the load increases then you will go to open loop and you should be around 23 or less. if your car is at 50 in open loop or at wot then you would have big time problems.

 

[JMD0346]

Thanks guys. I feel much better now. It only does this with slight throttle input so it must still be in closed loop. Once you give it even a hint of throttle it starts to drop.

 

[V8Mustang]

If you datalog a full throttle, say 3rd gear, run, you should be able to download the info to your PC and view the curve. I've not tried it yet but plan on it.

 

[Chonger]

I've datalogged timing a shitload of times w/my predator. It literally jumps all over the place. Do a 3rd gear pull on the highway and you will see the results you are looking for. Mine jumped from 10* to 30* and all over the place at partial throttle and stop and go.

A WOT blast read 21*@3,400 to 22*@3,700 to redline.

 

[Sonic03inSC]

Michael,
When are you getting that thing on the Dyno?
John

 

[JMD0346]

Soon I hope. I had hoped to go to Rick by now but he's having dyno problems. He street tuned it but that didnt tell me much. It is seeing 23 degrees timing. JUst went and checked it a couple hours ago.

 

[ricksterman]

I have screwed with this on my Mach1 for 6 months (of course I had knock sensors that I had to contend with too, totally worthless POS if you ask me).

In closed loop timing isn't relevant sine there is an active feedback. WOT is open loop and the spark timing is based on load and temperature. When you mod the vehicle you change the perceived load, and as a result the timing can change. The Predator has two ranges for timing, 2-4, 4-7K but these only adjust the existing timing curve in percent (10% is about 2 degrees max). Which is why, especially on forced induction motors, getting a good custom tune can make such a difference.

On my Mach with a custom tune I can pull 29 degrees advance (5200ft) without audible ping, but I doubt it makes much difference. The Cobra is at a safe 20 degrees WOT after 3K RPM. Since I am not allowed to post attachments I can't show you the dyno runs (w/ datalog overlay of load/spark) and the datalogs (Cobra), but doing this type of data collection and analysis will show you a lot, and also help you pinpoint deficiencies and potential problems (BOOM!). I know this information has probably already been presented numerous times, but it's always good to reiterate.