cammed 6.4 self driving

I have a 2015 GC with a 6.4 that has the below mods

* FRP tomahawk cam w/lockouts
* FRP drop ins at stock compression
* stainless works longtubes
* 180 t stat

I'm noticing that right at 1500 rpms especially at 20-30mph (3rd or 4th gear) I'm getting some self-driving behavior especially during warmup. It's still there during "regular" driving, but is most noticeably during warmup. I've attached my current tune and a log. Can someone tell me what I need to change to make the this behavior stop?

Attachment 153808

Attachment 153809

Quote:

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Originally Posted by Chubby Racer

I have a 2015 GC with a 6.4 that has the below mods

* FRP tomahawk cam w/lockouts
* FRP drop ins at stock compression
* stainless works longtubes
* 180 t stat

I'm noticing that right at 1500 rpms especially at 20-30mph (3rd or 4th gear) I'm getting some self-driving behavior especially during warmup. It's still there during "regular" driving, but is most noticeably during warmup. I've attached my current tune and a log. Can someone tell me what I need to change to make the this behavior stop?

Attachment 153808

Attachment 153809

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This should fix it.

So, basically you're just commanding more throttle closure when making a small throttle closure request?

I've experienced this, as well as a run-away throttle at idle, when I had too large of numbers in the 1st few entries of the throttle body airflow model table. I've also experienced some of the "cruise control" effect when the small & large range tables were not the inverse of the throttle body airflow model table.

Your small and large range tables do not appear to be the inverse of the throttle body airflow model table.

Here are your tables:

Attachment 153848


I've done a lot of tweaking on mine over the past few months, and here is where I landed for my supercharged 5.7L:

Attachment 153849


The last change I made, to smooth out the throttle tip in, was to match the 1st three entries to that of a Hellcat. Here is a look at the stock Hellcat tables:

Attachment 153850


The way I understand these tables is that they are not demand tables, but are characterization tables which define theoretical air flow through the throttle body opening, at sonic speed, when the blade is opened the amount in which the voltage being applied would result.

All of the those tables, to my knowledge, are stock. So now I’m really confused.


EDIT: nevermind, the tuner had modified them. Thanks.

Keep in mind the cam also changes your airflow, so the model probably needs tweaking to account for it.

Yea, I clearly need to figure out what parameters to look at to do that. This is the first ETC car I’ve attempted tuning.

Quote:

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Originally Posted by Stoopalini

The way I understand these tables is that they are not demand tables, but are characterization tables which define theoretical air flow through the throttle body opening, at sonic speed, when the blade is opened the amount in which the voltage being applied would result.

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Quote:

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Originally Posted by Stoopalini

Keep in mind the cam also changes your airflow, so the model probably needs tweaking to account for it.

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But if they're just throttle body characterizations and my throttle body hasn't changed, shouldn't I just leave these alone?

engine is a air pump

you changed the cam

the cam is its brain so you changed the actual airflow

there are no scalars for lift duration and overlap... wouldnt that be nice

the pcm does not use any sensors that measure airflow

it only knows temps, pressures, rpm, throttle and cam position

the airflow is calculated by combining those factors and what stoop is calling characterizations

Ok, playing with the throttle body airflow table below 1v, and matching the small and large range to it has solved my self driving. I did have 2 questions:

1. should the first cell in both the small and large range always be 0?

2. Since making these changes, I'm getting a little idle surging. I'm guessing these changes are going to effect the throttle PID logic, and I'm going to need to soften that as well. Is that accurate?

Quote:

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Originally Posted by LilSick

engine is a air pump

you changed the cam

the cam is its brain so you changed the actual airflow

there are no scalars for lift duration and overlap... wouldnt that be nice

the pcm does not use any sensors that measure airflow

it only knows temps, pressures, rpm, throttle and cam position

the airflow is calculated by combining those factors and what stoop is calling characterizations

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My understanding was that these were test bench flow numbers similar to how you you’d get a voltage vs airflow table for an aftermarket MAF.

Check out this thread:

https://forum.hptuners.com/showthrea...+throttle+body

Hemituna does a great job explaining how these tables can be used to modify the way the throttle feels.

In terms of your slight idle surge, I'm not sure on that ... I get a slight variation when idling, but mine is due to the AC compressor cycling. If I turn the HVAC system off, it goes away on mine. It hasn't annoyed me enough to chase it down and fix it yet though.

Quote:

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Originally Posted by Stoopalini

Check out this thread:

https://forum.hptuners.com/showthrea...+throttle+body

Hemituna does a great job explaining how these tables can be used to modify the way the throttle feels.

In terms of your slight idle surge, I'm not sure on that ... I get a slight variation when idling, but mine is due to the AC compressor cycling. If I turn the HVAC system off, it goes away on mine. It hasn't annoyed me enough to chase it down and fix it yet though.

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The GC supposedly has a 2800 rpm converter stock, but when it gets to "chopping" it rocks the car on the converter. I had killed that effect before messing with the TB airflow tables, but it has crept back in slightly.

where a converter stalls with the engine at max tq ouput doesn't have anything to do with the car rocking at idle

you cannot really use rpm to label a converter in the first place...

apply more tq to it (with the car dead hooked) and it will allow a higher stall rpm

I was just meaning that it was looser than the 1600 rpm converter in most other hemi equipped vehicles. So my rocking at idle isn't the result of big-cam-stock-converter "that's just what big cams do" stuff.

Is there anything I should be logging here to make sure my changes are correct, or is this entirely just a feel thing?

Guys, I really appreciate the help with this. Bumping the airflow below 1v and matching the small/large range tables has completely killed the self-driving/cruise-control behavior. However, I’m now having a problem where I’m getting surging at very low throttle commands. Like, creeping forward in stop-and-go traffic. Do I just need to keep bumping up the airflow below 1v til it quits?

you will have to play around a little bit with the area of IDLE / Airflow / proportional spark and derivative spark tables. for the creeping surge but there are other tables you can touch example torque tables.

Quote:

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Originally Posted by MadhousePerformance

you will have to play around a little bit with the area of IDLE / Airflow / proportional spark and derivative spark tables. for the creeping surge but there are other tables you can touch example torque tables.

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When you say torque tables, are you talking about friction loss?