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Discussion Starter · #1 ·
This is a corollary to my post on the "How to" sub-forum. I installed the Insight on the 4th of July, so I’ve had some time to look at displayed data.

I configured the first gauge screen to show Exhaust Gas Temperature (from the probe), Soot Level (in grams), and Boost (from the factory PID). EGT’s, in degrees F, are typically in the high 200’s to low 400’s at idle, depending on the overall engine temperature (cold start-up vs. idle @ normal operating temperature). Medium acceleration gets it up to 700’s ~ 800’s. Loading it up pretty well gets it into the 1100’s. I checked the “Records” function, and found that the highest it achieved was 1275 deg F. All of this is about what I expected, from my limited experience of riding in trucks with a pyrometer.

There is an available, and configurable, digital readout under the virtual analog gauge, which I set for “EGT #1 (Post Turbo)”. It’s interesting to observe the relationship between the pre-turbo and post-turbo temperatures. During acceleration, the pre-turbo temp is greater than the post-turbo temp as you would expect (thermal energy is converted to mechanical energy to drive the turbo compressor). During deceleration, the post-turbo temp exceeds the pre-turbo temp, which I assume is the effect as the wave of thermal energy passes through the turbo without “doing” much. It might be interesting to set up a digital gauge screen to display each the pre-turbo EGT, post-turbo EGT, and Turbine Vane Position.

As for boost, the highest recorded was 27 PSI… I haven’t REALLY romped on it yet…so maybe it’ll go higher. I assume that the boost value is calculated from the MAP sensor signal (versus the ambient barometric pressure). I’ve configured the digital gauge below the analog gauge to show the MAP Sensor value, which by definition of the acronym, is the absolute pressure in the intake manifold. This would be a function of the barometric pressure, boost, any resistance in the intake piping, and the “throttle position” (since these crazy modern diesels actually do have a throttle). I think it was the boost factor that threw me for a loop when I observed the second regen I’ve experienced since installing the monitor. I watched the relationship between boost and MAP pressure. During regen the boost seemed to say at zero while the MAP dropped to sub-atmospheric…..10 ~ 11 PSIA. I drive in rolling to steep hills, so sometimes the boost would come up (with load), but there were many times during regen when I expected some minimal boost (1 ~ 2 PSI), but it seemed to stay at zero. I think the computer may blow off the boost pressure in an effort to keep EGT’s higher for regen.

That brings me to Soot Levels and Regen. The soot level was at 19 grams when I first plugged in the monitor permanently. As per the GM Service Manual, the computer will initiate a regen when the soot level reaches 22 ~ 25 grams. Sure enough, the car has performed a regen each time the soot level has transitioned from 21 to 22 grams. I’ve experienced three regens since July 4th (darn mixed city/suburban driving!).

Otherwise, I’ve glanced at “DEF Injections” readout that presumably shows when DEF is being injected. Bizarre…it rapidly goes from zero to fast changing values. I’ve looked at injection timing as well. I’ll have to investigate the expected behavior of those items further.

That’s all for now.
 

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Very cool! Thanks for sharing!

Otherwise, I’ve glanced at “DEF Injections” readout that presumably shows when DEF is being injected. Bizarre…it rapidly goes from zero to fast changing values.
Have you been able to track any patterns for DEF usage? For example, does it spike when you romp on it? From my limited knowledge of "how it all works," I would assume during periods of high load, the EGR closes down and the turbo spins up pushing more oxygen into the combustion chamber and resulting in the need for more DEF to offset the resulting NOx generation. Does that sound correct?
 

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Very interesting post. I would have thought the DEF would always be injected at some rate while the car was running.
 

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Discussion Starter · #5 ·
Have you been able to track any patterns for DEF usage? For example, does it spike when you romp on it? From my limited knowledge of "how it all works," I would assume during periods of high load, the EGR closes down and the turbo spins up pushing more oxygen into the combustion chamber and resulting in the need for more DEF to offset the resulting NOx generation. Does that sound correct?
To be honest, I haven't looked at DEF much. I've been more interested in the rate of soot accumulation, and timing of the regens. I'll have to take a look at DEF behavior soon.

You may be right about the increased use of DEF under high load conditions.
 
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Are you running stock or have you chipped?
 

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Discussion Starter · #8 ·
Are you running stock or have you chipped?
Still stock. Might consider a tuner in the future, but I'm interested to see what the aftermarket discovers about the transmission.......and how they choose to handle it.
 
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are you running 27 psi on the stock turbo? correct me if i am wrong but isn't there a point where it would not make any more hp (with it being such a small turbo), its like a T25 off of an eclipse can show 25psi but after 18psi i believe it starts to heat up the air and causes less hp at 25psi than you would have at 18psi due to the pressure causing heat, or something to that effect if i remember correctly.

Is there a turbo chart out there that anyone knows of?
 

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Discussion Starter · #10 ·
are you running 27 psi on the stock turbo?
So says the "Records" (aka recall) function.

I believe Duramaxtuner hit ~30 PSI on the stock turbo........but I believe that was with programming.

Values of 20 ~ 22 PSI under "strong acceleration" are more common.
 

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To be honest, I haven't looked at DEF much. I've been more interested in the rate of soot accumulation, and timing of the regens. I'll have to take a look at DEF behavior soon.

You may be right about the increased use of DEF under high load conditions.
Actually I can almost garuntee there is more Def use under higher loads. It makes logical sense. Generally under high load the output of exhaust gas is in relationship to the burning of fuel. Burn more fuel, more exhaust, more exhaust used the more conversion fluid that must be used to keep specs in line.

Sent from AutoGuide.com Free App
 

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are you running 27 psi on the stock turbo?
This is a boost spike. Rapid acceleration of increasing boost before the full effect of the wastegate can dump excess exhaust gasses. You will not see 27psi as a constant on any stock CTD.

These boost spikes are so fast, that you can't even see them with an analog gauge. Only a computer, taking measurements every millisecond, will know it was there. :)
 

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Discussion Starter · #13 ·
More observations...

Observed another regen last night on the Insight... Interesting...

The soot level approached 22 grams, but the little red "R" light did NOT come on immediately. I was cruising on the parkway through town, so I couldn't tell if a regen was initiated... BUT, the soot level started falling. IIRC, the regen indicator light didn't come on until the soot level dropped to about 17 grams.

I noticed the same thing one other time. Not sure why that happens that way.

Anyway, if I haven't mentioned it before, the regen continues until the level drops to 3 grams, then quits. This has proven to be consistent for me.

One thing that is somewhat disturbing: the soot levels rise again quickly immediately after regen. In my return trip home last night (10~15 miles, mostly highway), the soot level rose from 3 to 11!

However, in my trip to and from work today (22 miles each way, mostly highway), it only gained 1 gram...!
 
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