How do you know when ignition timing is too much retarded?
11-26-2011, 09:24 PM
#1
Drifting
Thread Starter
How do you know when ignition timing is too much retarded?
I got hold of the software to my unichip which can change the timing and fuel on my tpc supercharged 993.
Want to tune it for max safety. But how do you know when timing is retarded too much? What are the symptoms or indicator?
Too advanced is easy...pings and your engine may go boom. But what about too much retarded?
I do have an exhaust temp gauge in one bank. Would this provide any clue?
Want to tune it for max safety. But how do you know when timing is retarded too much? What are the symptoms or indicator?
Too advanced is easy...pings and your engine may go boom. But what about too much retarded?
I do have an exhaust temp gauge in one bank. Would this provide any clue?
11-27-2011, 01:10 PM
#3
Nordschleife Master
Loose of power & just being lethargic is a good benchmark. On boosted engines you do retard the timing from a NA engine.
Best thing to do, is rent some dyne time, do some ODBII logging, with wideband reading, then see what's going on.
Best thing to do, is rent some dyne time, do some ODBII logging, with wideband reading, then see what's going on.
Last edited by Stealth 993; 11-27-2011 at 08:40 PM.
11-27-2011, 01:45 PM
#4
Race Director
i'm gonna be perhaps a touch harsh here, but you have to be very careful tuning your own car if you don't have any experience. One wrong keystroke and that expensive engine will be a smouldering heap.
Renting some dyno time would be a good idea, but you can also go by feel to some degree. As noted above, a car with severely retarded timing would have awful throttle response and would just feel sluggish.
Who did your baseline tune and why do you want to modify it?
Renting some dyno time would be a good idea, but you can also go by feel to some degree. As noted above, a car with severely retarded timing would have awful throttle response and would just feel sluggish.
Who did your baseline tune and why do you want to modify it?
11-27-2011, 02:18 PM
#5
Addict
Lifetime Rennlist
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Was not tracking this....did you change out the distributor? If not, there are limits to the adjustability of the timing anyways, since you at least have to have the rotors near the cap studs in order to get the spark to the plug, and our systems are essentially mechanical. I think the timing adjustment is when the coils fire?
No sure if you would end up with a "smoldering heap" but you can cause damage, especially in your case where you are stressing the engine. It would be relatively easy to have some pre-detonation and put a hole in a piston for instance, so be careful.
Does TPC have recommendations?
Cheers,
Mike
No sure if you would end up with a "smoldering heap" but you can cause damage, especially in your case where you are stressing the engine. It would be relatively easy to have some pre-detonation and put a hole in a piston for instance, so be careful.
Does TPC have recommendations?
Cheers,
Mike
11-27-2011, 03:06 PM
#6
Rennlist Member
If you can adjust your timing on the fly, then you DEFINITELY need to visit a Dynapac dyno with a professional tuner. That's really the only way to do this properly. In just a few hours they'll know exactly what timing you need across the rev band. It would be absolutely crazy to try this yourself. I'm sure there are shops near you that can do this; just make sure it's NOT an inertia dyno like a Dyno Dynamics or Dynojet. But your tuner can explain all this.
11-28-2011, 05:53 PM
#7
Drifting
Thread Starter
I'm too far from TPC to have them tune the car fully. The tune right now is reasonably good. However, when the engine is cold, Motronic rapid acceleration function is pretty aggressive in the timing area, and I'd like tune that out.
Okay, another question. Seemed like the procedure for dyno is to first set the AFR, then tune timing by increasing timing advance until you power drops indicating you've max your timing limit. Then drop timing a degee or two. Is this still a good method since you'll be allowing the the DME to push timing to its max (until car gets pings) on a high-compression supercharged engine? I would have though ANY pings is a no-no. So why let the DME push the timing until it ping?
Okay, another question. Seemed like the procedure for dyno is to first set the AFR, then tune timing by increasing timing advance until you power drops indicating you've max your timing limit. Then drop timing a degee or two. Is this still a good method since you'll be allowing the the DME to push timing to its max (until car gets pings) on a high-compression supercharged engine? I would have though ANY pings is a no-no. So why let the DME push the timing until it ping?
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11-28-2011, 11:08 PM
#8
Race Car
If you can adjust your timing on the fly, then you DEFINITELY need to visit a Dynapac dyno with a professional tuner. That's really the only way to do this properly. In just a few hours they'll know exactly what timing you need across the rev band. It would be absolutely crazy to try this yourself. I'm sure there are shops near you that can do this; just make sure it's NOT an inertia dyno like a Dyno Dynamics or Dynojet. But your tuner can explain all this.
On a dyno is the only safe way to turn any engine properly and safely (assuming the operator is a good one).
The dyno you need is basically any that will allow you to tune load points. Ie. the dyno must be able to "brake" to hold the engine RPM at a certain level. Dynopac being one of the most popular at the moment as it is a hub dyno ie. car cannot fall off.
Contrary to popular opinion Dynojets (an inertial Dyno) do have a brake system that will allow you to hold the car at a certain RPM and then tune that load point. In days of old inertial dyno's would only allow you to do "power run's" ie 4th gear WOT to redline (no stopping), the tuner would then best guess the right tuning and then run again.
Find a tuner, a good dyno and ask to sit in the passenger seat while the whole thing goes down, if they won't let you, find another tuner.....
11-28-2011, 11:13 PM
#9
Race Car
Axl. Here is a quick article for you to ponder...
Extract: "When you make a change to add or subtract ignition timing, you will normally see a corresponding change in power output.
Using an onboard or aftermarket Knock sensor to check for detonation is the easiest way to find the maximum allowable ignition advance. However, if you do not have access to one, here is another way to get pretty close.
Advance the timing until maximum power is reached and begins to fall off when more timing is added. From there, back off the ignition advance one or two degrees and set it there.
Once you have made a few hard pulls on the engine at this setting, shut it off and remove the spark plugs. Inspect them for obvious signs of detonation or erosion. Pay careful attention to the J-shaped ground strap. You will notice that somewhere on the strap it begins to change color.
Ideally, when the proper timing is set, there will be enough heat in the combustion chamber to make the color change at about the center of the strap. If it changes more out towards the end of the strap, then there is not enough heat, and more advance is needed. Conversely, if the color change is near the bottom where the strap joins the plug, then take some ignition advance out in order to start the burn later and transfer more heat out the exhaust!" Ben Strader..
Full Article:
http://racingarticles.com/article_racing-62.html
Extract: "When you make a change to add or subtract ignition timing, you will normally see a corresponding change in power output.
Using an onboard or aftermarket Knock sensor to check for detonation is the easiest way to find the maximum allowable ignition advance. However, if you do not have access to one, here is another way to get pretty close.
Advance the timing until maximum power is reached and begins to fall off when more timing is added. From there, back off the ignition advance one or two degrees and set it there.
Once you have made a few hard pulls on the engine at this setting, shut it off and remove the spark plugs. Inspect them for obvious signs of detonation or erosion. Pay careful attention to the J-shaped ground strap. You will notice that somewhere on the strap it begins to change color.
Ideally, when the proper timing is set, there will be enough heat in the combustion chamber to make the color change at about the center of the strap. If it changes more out towards the end of the strap, then there is not enough heat, and more advance is needed. Conversely, if the color change is near the bottom where the strap joins the plug, then take some ignition advance out in order to start the burn later and transfer more heat out the exhaust!" Ben Strader..
Full Article:
http://racingarticles.com/article_racing-62.html
11-29-2011, 11:02 AM
#10
Rennlist Member
+1. That was my experience when recently tuning my race car. My tuner actually had me work the software so that I'd learn it better.
12-01-2011, 01:32 AM
#15
Rennlist Member
Trophy you won't need all 6. Only 1 cylinder, of course assuming that both turbos are providing even boost to each bank, which should be sorted out before tuning anyway. The other Eric, usually the cylinder pressure transducers go through a charge amplifier and then you can read them using an oscilloscope or other data acquisition system. I would want to instrument a stock turbo engine prior to any dyno work to establish a value of what your baseline maximum cylinder pressure is from a factory boosted engine. Porsche certainly won't disclose what their cylinder pressure limits are but you definitely wouldn't want to exceed 1.5 times a baseline value for very long.
Axl I would just stick with the knock sensors as you have mentioned, pinging is something to avoid, tune so that there is no correction. The correction should only be used in a situation preventing detonation like bad fuel, overboost, etc. If you're doing timing work, the cylinder pressure transducer is a tool used to see how far you are pushing, but the power may not be highest at peak pressure. The transducers and data acquisition is costly, not worth the investment in my opinion unless you're developing a setup that you plan on selling and you're using the data as validation. The more advance, the higher the cylinder pressures, also the higher the boost the higher the cylinder pressures.
I used knock sensors when I tuned up my camaro after I modded it. One more point to add, you should start with a rich calibration as a default and lean out from there, not sure how much AFR work you've done so far but before you start just command fuel high before you start tuning and lean out.
I hope i'm providing some insight or tips.
Axl I would just stick with the knock sensors as you have mentioned, pinging is something to avoid, tune so that there is no correction. The correction should only be used in a situation preventing detonation like bad fuel, overboost, etc. If you're doing timing work, the cylinder pressure transducer is a tool used to see how far you are pushing, but the power may not be highest at peak pressure. The transducers and data acquisition is costly, not worth the investment in my opinion unless you're developing a setup that you plan on selling and you're using the data as validation. The more advance, the higher the cylinder pressures, also the higher the boost the higher the cylinder pressures.
I used knock sensors when I tuned up my camaro after I modded it. One more point to add, you should start with a rich calibration as a default and lean out from there, not sure how much AFR work you've done so far but before you start just command fuel high before you start tuning and lean out.
I hope i'm providing some insight or tips.
Last edited by uicnick; 12-01-2011 at 02:06 AM.