8100hd

You can kinda look at bmep as torque produced, it is actually 150.2 x (torque/ci) I think? The numbers in the graph is fuel consumption.

kehyler

Thanks for the explanation.

Mind also giving me your thoughts about the second portion of my last post?

8100hd

I would lockout gears depending on load and terrain. If you can run at lower rpm without hitting maximum boost that’s good. If you need to accelerate to pass down shift but most likely the tranny will do so. For those interested here’s a link to how octane detection works how it’s used to try and control LSPI.
https://cobbtuning.zendesk.com/hc/en...ust-Ratio-OAR-

Tom_with_a_Truck

Thanks for the info, 8100. In terms solely based on fuel consumption, then, you would want to be in the blue circle where consumption is lowest, around 2500 rpm for the engine used in the graph. But there are other important aspects such as exhaust heat and preignition risk that would make running at a higher RPM better for the engine, even at a slight cost in fuel consumption.

8100hd

Ideally yes. Hopefully the ECU should be working towards that in real time. That chart came from the engine labs website and I’m not sure what engine it’s for, but most downsized GTDI engines have similar curves.
http://www.enginelabs.com/news/video...y-your-engine/

mass-hole

I really dont think lugging is an issue on these motors. Being able to control exactly when the fuel is injected is part of that and I rarely find that my truck will automatically drive below 1500 RPM. Even when it does, I have never felt lugging like I did in my 2006 GTO 6 speed by forcing it to run in 6th gear at 40 mph(it was like a .56:1 6th or something dumb). And that was at like 1000 RPM. Never once has my truck willing operated that low in the RPM's and when in tow/haul its typically never below 1700.

There are load limitations in the tuning to prevent LSPI based on IAT's and RPM. There is also knock retard which automatically adjust timing on the fly based on knock and there is Octane Adjust Ratio which is more of a long term/average timing adjustment based on how the ECU determines the fuel reacts. Unless you are using absolutely horrid fuel which the tuning doesnt have the capacity to adjust for, these things shouldnt be an issue. Even my 5Star 87 octane towing tune is usually running at -5 Knock Retard while under full load which is the best it can possibly be and its making far more power than the stock tuning. This is on 87 or 88 octane fuel.

This is also why a good aftermarket intercooler is very important for towing, way more important than fuel Octane I believe. If you are seeing 180+ IAT's on the stock intercooler then your truck is likely operating at reduced power and timing anyways and your fuel octane wont fix that. I towed in 50 degree weather the other day and my IAT's were approaching 170 on climbs. My factory tune starts cutting the allowable load limit based on LSPI at 120F IAT's. If you can keep those IAT's within 10-20F of ambient temp then you are operating at your trucks full potential. Its also a good argument for a catch can since oil can contribute to LSPI.

Exactly. HP is a measure of how much torque you can apply to the tires. You could have two motors, one that produces 200hp/105 ft-lbs at 10000 RPM and the other that produces 200 hp/525 ft-lbs at 2000 RPMs. But to operate at the same speed, the 10000 rpm motor needs 5x the gear reduction. So even though it produces 1/5th the torque, its sending the same torque to the tire via the 5x more gear reduction so its the same. Obviously no one wants to tow with a 10000 rpm motor but this is an extreme example to show that torque is not the answer, HP is.

This is exactly why a Ram Ecodiesel, which produces the same torque as the 1st gen Ecoboost, gets the snot kicked out of it when climbing the Ike Gaunlet on TFLtruck. They make the same torque but the F150 makes far more HP. This is also why a 5.0 isnt really at any kind of disadvantage when it comes to absolute towing power vs the ecoboost. It can pull just as much trailer up a hill as the EB because it makes the same or more peak HP. It just does it at a higher RPM in general.

With regards to the OP's question, there is enough safety measures in the tuning to prevent knock or LSPI from being an issue unless you fill your tank with absolute cow manure for fuel. And for me, I let the Tow/Haul mode do what it wants and dont worry about what gear its in. I generally will get down to 4th gear on the steppest climbs here at 6500 ft which is the 3000-3500 rpm range. Only once have I seen 3rd at highway speed and that was on a super hot day when Im sure I was running at reduced power because of IAT's and what not.

Tom_with_a_Truck

Interesting link - thanks. I followed it out to another description of knock control. Brought me back to the days when I had a tuner for my Honda Civic Si. Fun times, but for me, there was more trial and error. The tuner I had wasn't quite as nice as the Haltech that is described in a video linked to the page.

8100hd

Losing an engine to LSPI has always been wide spread and random but unfortunately it’s still happening today. Manufactures are pushing hard on the API for SN-Plus since the best way anyone has found to prevent it is to change oil formulations.

RubyRed Canadian

The last trip I towed on, I looked at the instantaneous fuel usage bar chart on the info screen.

With cruise control set and fairly flat terrain, the fuel usage was lower in 5th gear when compared to 6th gear.

Plus locking out 6th prevented nuisance shifts on overpasses as well.

To prevent nuisance shifting, I guess I could have manually locked the transmission in 6th, but I found the mileage was better in 5th...according to the bar chart anyway.

kehyler

Thx. Mind sharing the speed/weight you were towing?