jtm209
New Member
- First Name
- JT
- Joined
- Jul 26, 2023
- Threads
- 0
- Messages
- 1
- Reaction score
- 0
- Location
- Columbus, Mississippi
- Car(s)
- 2023 Integra MT
I’ve had my 6-speed Integra since November and I’ve been loving the car. It has the perfect mix of sportiness, fuel economy, practicality and looks. Plus it has a manual transmission and a decent price. If you need to operate with only one car and you value all six of those things, you can’t really do better. Maybe the Civic SI, but those don’t have the hatchback space and I couldn’t bring myself to pay a dealer markup.
I bought a KTuner with the Phearable tune about a month ago and I’ve been running it since. It fixes one of the few problems I had with the car, which was rev hang, specifically on the 1st to 2nd gear transition. Easier to shift quickly, more power, and does not seem to affect highway fuel economy much. But it is difficult to compare numbers because I switched to 93 octane fuel and moved from MA to MS where the speed limits are higher. 7% higher highway speed is 15% more fuel consumption for the same distance.
I’m posting here because I have an idea for a tune that could improve highway fuel economy and I wanted some feedback on it. I studied electrical engineering and I have a bit of an irrational desire for efficiency that I think I share with all engineers. Plus I take long trips with lots of highway miles where I don’t care about engine power, but I do care about fuel cost. I want to switch to a tune based on the KTuner basemap. Map 1 would be basically stock so I can hopefully run 87 for long trips (I'll monitor knock to make sure it's safe). Maps 2 and 3 would be at 19 and 21 PSI in sport mode and I would only ever run those with 93 octane. But the main point of this tune is that I want to have the boost target limit table for 6th gear full of zeros so the engine basically becomes naturally aspirated in 6th. The engine is probably only running at 10% of peak power or less at 2800 RPM on the highway, so boost should not be necessary and I can always downshift to 5th for passing.
I have a few KTuner-specific questions about how to best implement this. Some of them are also more general about what the KTuner actually does. This stuff is pretty in-the-weeds, but I think it would be helpful to learn how the ECU actually uses the turbo.
Sorry for typing out a novel here. I suppose I could figure a lot of this out by trial and error with some fuel economy testing, but that would take forever. At any rate, I hope this will stimulate discussion.
I bought a KTuner with the Phearable tune about a month ago and I’ve been running it since. It fixes one of the few problems I had with the car, which was rev hang, specifically on the 1st to 2nd gear transition. Easier to shift quickly, more power, and does not seem to affect highway fuel economy much. But it is difficult to compare numbers because I switched to 93 octane fuel and moved from MA to MS where the speed limits are higher. 7% higher highway speed is 15% more fuel consumption for the same distance.
I’m posting here because I have an idea for a tune that could improve highway fuel economy and I wanted some feedback on it. I studied electrical engineering and I have a bit of an irrational desire for efficiency that I think I share with all engineers. Plus I take long trips with lots of highway miles where I don’t care about engine power, but I do care about fuel cost. I want to switch to a tune based on the KTuner basemap. Map 1 would be basically stock so I can hopefully run 87 for long trips (I'll monitor knock to make sure it's safe). Maps 2 and 3 would be at 19 and 21 PSI in sport mode and I would only ever run those with 93 octane. But the main point of this tune is that I want to have the boost target limit table for 6th gear full of zeros so the engine basically becomes naturally aspirated in 6th. The engine is probably only running at 10% of peak power or less at 2800 RPM on the highway, so boost should not be necessary and I can always downshift to 5th for passing.
I have a few KTuner-specific questions about how to best implement this. Some of them are also more general about what the KTuner actually does. This stuff is pretty in-the-weeds, but I think it would be helpful to learn how the ECU actually uses the turbo.
- How does the engine/turbocharger normally respond to low load conditions? I would think it either (1) closes the wastegate and lets the turbo build boost that is immediately pissed away by a mostly closed throttle to limit engine power, or (2) it fully opens the wastegate and does not close the throttle as much. I’d assume option 2 is more efficient. The gas pedal in a modern car is just a potentiometer, so the ECU could do either of these things and the driver wouldn’t know the difference.
- What does the “Early Spool” do exactly, and how would it affect the turbo when on the highway at low load and constant RPM of 2800? If the engine runs like option 2, there must be a low-to-middle point in the accelerator pedal range where the ECU decides to close the wastegate and spool up the turbo. Maybe this makes that cutoff point earlier? That would reduce partial throttle fuel economy but improve low and mid-range throttle response.
- What does the “Boost Target Ramp Rate” do exactly and how would it affect the engine under highway conditions? I assume that after the turbo is spooled up, the wastegate starts closing and is modulated by some sort of feedback controller to make the actual boost pressure track some computed target boost pressure. It seems like this setting changes how that target ramps up with time. Is that true?
- There are also the “Turbo Responsiveness” modes. These seem really similar to the “Early Spool” option and I suppose they affect the same thing. If I’m right and the engine works like option 2, they change the point in the accelerator pedal where the wastegate closes to spool the turbo. Before that point, the engine acts like it is naturally aspirated. Is this correct? If so, how do these two settings interact? Does one supersede the other?
- If you were trying to minimize fuel consumption at low load and 2800 RPM, would you enable or disable “Early Spool”, “Turbo Responsiveness”, and more aggressive “Boost Target Ramp Rates”? Would these settings even matter if the boost target was forced to zero by the boost target limit table?
- Will my method of zeroing the boost target limit table for 6th gear actually do what I want and force the ECU to disable the turbo? Or will the ECU do that automatically by default at low load/RPM (making this unnecessary)? Would there be any possible damaging effects if I did this?
- What is up with the “VTEC Activation” options on the L15CA? It does not look like the one here: http://ktuner.com/KTunerHelp/vtec.htm. Looks like the factory default is to engage “Cruising” VTEC at 1200 RPM, which seems really low. I thought most Honda engines engage VTEC at ~5000 RPM in order to optimize valve timings for torque and power instead of efficiency. It seems like the L15CA uses its VTEC as an efficiency thing and it is always engaged at partial throttle above 1200 rpm. Which means VTEC is only really disengaged when idling or WOT. I guess this means the L15CA is opposite of normal and the more performant valve timings are the ones with VTEC disengaged. Does this sound right? How is VTEC used for these engines? Should I fiddle with those parameters at all?
Sorry for typing out a novel here. I suppose I could figure a lot of this out by trial and error with some fuel economy testing, but that would take forever. At any rate, I hope this will stimulate discussion.
