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My car has had an on-going problem with power reduction at high speeds on a hot day. No codes are ever set but the top speed drops drastically after a few minutes.
I am trying to identify a change in ignition engine timing advance that might be associated with the power reduction. I have posted two pictures captured from recorded data from TouchScan that show the timing advance for two different test drives.
The first is a 3-mile drive around my neighborhood at 30-45 mph taken at a high update rate. The second is a highway drive on cruise control at 70 mph taken at 1 sample per second.
I really don't understand what I am seeing. On the highway drive the road was flat and the speed constant. I did not expect the large timing variations.
I am trying to get a baseline of what normal timing advance looks like on this car so I can identify a change during my high-speed events. But I don't see much in the way of a baseline here.
Anyone with any real experience or insight into the timing advance information I'm seeing?
Cruise logs aren't going to tell you anything. You need to log the timing along with intake air temps (IATs) during full throttle runs and compare before/after as temps heat up (and the car heatsoaks).
As someone who is -very- experienced at datalogging - you need to datalog several things simultaneously. I would log vehicle speed, load, throttle position, air intake temp, fuel rail pressure and short and long term fuel trims at a minimum in addition to spark. Keep in mind there are several modifiers to spark such as intake air temp, knock reduction, torque modulation and a few others. You will not be able to make sense of what you are looking at datalogging just spark by itself. And try to replicate the conditions when you experience power loss as this is the area in question.
As someone who is -very- experienced at datalogging - you need to datalog several things simultaneously. I would log vehicle speed, load, throttle position, air intake temp, fuel rail pressure and short and long term fuel trims at a minimum in addition to spark. Keep in mind there are several modifiers to spark such as intake air temp, knock reduction, torque modulation and a few others. You will not be able to make sense of what you are looking at datalogging just spark by itself. And try to replicate the conditions when you experience power loss as this is the area in question.
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Thank you. I am actually logging most of the items you listed. I only posted the timing graphs to keep to post as simple and to the point as possible.
What am I looking for in the logged data for a high speed event. I am running at 165 mph then the max speed drops quickly to 135-142 mph.
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Thank you. I am actually logging most of the items you listed. I only posted the timing graphs to keep to post as simple and to the point as possible.
What am I looking for in the logged data for a high speed event. I am running at 165 mph then the max speed drops quickly to 135-142 mph.
If you maintain a sustained 165 mph, you might be in catalyst overtemp protection. If this happens, you would probably see more fuel added in the trims and you might see throttle reduction. Add throttle actuator position or actual throttle position as well to your datalog.
Ignition Timing Advance Analysis
