2350 cold weather MCF table adjustment

[SemiSweet]

My 2350 has been demandated by a reputable member on this forum. Alberta has been in a deep freeze lately -30 to -40 and I am constantly on the boost gauge trying to keep boost down under 30-33 psi due to the dense air. I have been doing some research on here trying to get a little more information on adjusting the MCF tables between 1500-1700rpm to limit the boost pressure possibly making a separate tune all together to load during the cold months.

I’m having to run a gear or two lower to keep boost in safe range and i cant run this thing at 60mph loaded (super bs) like this . It’s probably ok if I am in the driver seat but I will at some point have to let another guy drive my truck and they do not understand the damage they can do.

Any advice to adjusting these values? I have all the technology to perform these changes but I have personally not made adjustments to an individual tune.

[Rawze]

First of all, are you sure that the engine is still using the mass flow references for its turbo positioning control?.

It is more likely that the turbo is being directly controlled via positioning tables instead .. after the de-mandate. If that is the case then simply lower the positions in the 'tahr_vgt_llim' table a bit where you think it needs adjusting, and that is all that has to be done.

Forum member 'running rough' lives and owns equipment up in those climates as well. Maybe he can chime in with his opinions on all the extreme cold weather.

[SemiSweet]

Thanks , From what I understand MM tunes do not employ the mass flow method, if they did it would compensate for the dense air correct?
I will do some tinkering with this Vgt table and follow up.

[Rawze]

(01-06-2022 )SemiSweet Wrote:  Thanks , From what I understand MM tunes do not employ the mass flow method, if they did it would compensate for the dense air correct?
I will do some tinkering with this Vgt table and follow up.

I have seen a few people try to control boost via the the 'MCF' methods. there is nothing wrong with doing it that way as long as it was done correctly. That is in fact the only method available in the CM870 programming. - It is far more touchy, sensitive, and unpredictable, but it is certainly doable. There will be a bit more turbo lag and unpredictable turbo positions by doing it that way, but it does somewhat work. - Either method that is used, requires a lot of tweaking to get it right.

[SemiSweet]

Update,

Adjusted the VGT table between 1500-1800rpm at around 3/4 fuel. Values in yellow were all lowered 2%. Tested all week and it’s working well keeping boost in that 32-33psi max while pulling hard.. I do need to make a few more adjustments at 15-1600 at 1/2fuel, I’m seeing the boost really jump fast when I get into the overdrive gears pushing up to 34 psi then dropping down. Overall It’s in the right direction. I also replaced the imap sensor to take any possible pressure error out of the equation.

While I was in the program I also lowered the torque tables under 1500 rpm down to 1850ft/lbs from 2050ft/lbs. I never pull below 1500rpm so I don’t notice any difference but it will keep the abuse down of someone else is running the truck.

[Rawze]

Thanks for sharing that. Looks pretty good there.

and yeah.. ,the lowered torque in the bottom end will make the engine live a longer lifespan.