LNF Engine Braking

[DrJones_CMR]

Sorry if there is already a thread on this topic! I used the search function and could not find anything.

Question: Is there anyway to get the throttle plate to close when lifting out of the throttle and provide engine braking?
Like many new cars that are drive by wire, when you let off the throttle pedal the throttle plate stays open (assume for emissions and such).
If I could get it to act like a cable operated throttle that would be great.

Background for my need: The car is an '07 Pontiac Solstice GXP setup for SCCA Solo (autocross) in the F-prepared class. Right now we can't really get the car to rotate by lifting the throttle. Yes it keeps the car pretty stable but it would be real helpful weaving through the cones.

[cobaltssoverbooster]

nope the Throttle body tables are not unlocked in the lnf. The best you can do is play with the optimum spark and dal tables to get it to respond a little faster to the changes which may net you so faster throttle closing but thats all there is at the moment and the future doesn't look good for getting more features unlocked.

thats a wicked car hope some adjusting works out for you guys.

[DrJones_CMR]

thanks for the response.

Why does the future not look good for those tables?
liability?

[cobaltssoverbooster]

copyright mostly.

[noorjSS]

shouldn't the DAL table be able to "shut" the throttle more on lift if you command less air load

[cobaltssoverbooster]

thats the idea. command less in the lower load high rpm areas and it should close the plate but it will only help to a degree. some of the hangup can be released by changing optimum spark to help with trq modeling interference.

[codename Bil Doe]

You can. The throttle blade closing is controlled by the integral gain table. I was going to post information on several unmentioned tables. Adjusting the gain tables properly will give you linear pedal response along with control over boost (and, subsequently, throttle blade). The boost, throttle blade, and timing are all directly related and adjusted together.

Things you will find with the integral gain table - adjusted too far one direction (stock settings) and it will hang open after throttle lift. Too far the other direction it will close the throttle blade faster than the pedal will go from 100% to 0%. Yes, that fast. But, it will also cause fluttering of your boost at WOT because it's fighting to meet the demand to close while you're WOT.

That's a very simplified explanation. In short, yes you can control it.

[codename Bil Doe]

Beautiful car by the way. PM me and I can give you some tips on alignment and other settings. I just got back from a track day this past weekend adjusting the tune. The car rotates nicely off-throttle. I have minor adjustments left on the tuning side.

[cobaltssoverbooster]

nice never gotten that response from that table before. thanks for sharing

[codename Bil Doe]

All the tables are interrelated. Eventually, I will post a thread with a full explanation of the tables that haven't ever been discussed as well as the ones that have, what they affect, and HOW to manipulate them. There is enough unlocked on this pcm to fully control everything. It just takes knowing how to change the available tables to make the unseen ones do what you want. The end effect is a very linear pedal response, great driveability around town with near instant throttle response when you stomp the gas pedal and no stuttering/hesitation.

I've spent the last 4-5 months testing and figuring out exactly what each table will allow you to do. They are very interrelated because so many are reference tables. Not a big issue, just requires that you have to make many adjustments until they're all happy.

I don't have the time right now to do a writeup. But, here's a very quick idea of what each of the gain tables does.

prop max - limiting table. set to max (327%). As a limiter table it shouldn't have any affect on responsiveness. But, I've noticed it does somewhat. Set to max to eliminate any effects.

prop gain - controls your boost ramp. This affects ramp up differently for larger single scroll turbos than it does for the stock turbo depending on where you set it. Too high and part throttle transition will be unruly (on/off switch when slowly rolling from 0-100% pedal).

integral gain - controls throttle closing. Effects stated in previous post

derivative gain - DERIVATIVE DOES NOT MEAN DIFFERENCE. THIS IS NOT A 'DIFFERENCE' TABLE. This controls boost overramp. Proper values will eliminate overboost on ramp-up. Too high and you will never hit boost levels because it takes too long to ramp up. Note what the right two columns are (0's) and how much overshoot you have stock.

Again, VERY brief description. I suggest whatever you set each table to, make it one value. This is one of the steps to giving your throttle a linear response. Don't ramp the tables. Also, read up on PID theory to at least get a little understanding. It's a control method. I'm a mechanical engineer and have several years experience with controls. It's not adding and subtracting.

Hope this helps a little. Later when I get a chance I'll explain how to manipulate the other tables.

[cobaltssoverbooster]

im glad you were willing to share because my results even with extensive dyno time were different on one of them. prop and derivative were same for me as you saw but ive been using maximum value prop max for so long i dont have any thing to compare it to to check response times.

i hope more people will explore and report.

[MikeM173]

I have been working with Codename Bill to some extent on these tables and I will say a lot of testing is required to fully understand and lock down your setup and your goals in properly. Between my conversations with him and my reading I will say I have exactly what I want out of these tables and others. I am currently tweaking all the time to help learn more. I don't feel most of the tables are needed for most peoples goals and or setup. I mean this beyond the realm of the PID tables. There are other tables people don't touch that have netted me some amazing goals to include driveability and performance. I think any serious tuner or car enthusiasts would seriously test all of these tables to help ensure the car runs amazing. Just my opinion.

[codename Bil Doe]

^this.

[cobaltssoverbooster]

most are fearful of the results on error like sticking throttle's and massive boost overshoots. they seem to forget that small amounts at a time will prevent you from hitting these extremes in an uncontrollable manner.
Im looking forward to what you guys have found, and hope it brings the rest in for a refresher and update to learn what they are missing.
I only touched every table on 2 cars due to the cost of running the dyno for so long, that is aside from my own. Others got adjusted tables after that but i limited them to a fixed spot instead of fine tuning every single one. A lot of them showed amazing results but when GMTech and IamBroke were the only two around who were up for sharing left for other projects i had no one else to compare notes to so i never shared anything.
the more you guys can share with each other the better.

[DrJones_CMR]

Thanks, Bill!
I'll have to dig out my controls book from school to freshen up on PID's. Haven't needed them since graduation (i'm a mechanical engineer too).
Everything you said makes sense and giving me the "Oh yeah" light bulb turn on.

-Alex

[codename Bil Doe]

Tell me about it. I had to do the same. The above is a quick how-to relative to adjusting. It's not quite controls as we know it because there are so many other interdependent tables that we don't have control over. In my brief explanation that lack of control is indirectly assumed, and the methods of manipulation above should get you what you're looking for. I had another track day test couple weeks ago to fine tune my numbers.

For prop and derivative gains, take a look at the highest values in the table as a place to start.

[MikeM173]

If I remember correctly GM actually leaves the entire wastegate table 95 on high load for both stock and GM flash tune and you'll notice they also don't raise DALs a lot. You'll also notice that the PID tables changed and if I remember correctly again it was mostly the prop table. My highest value is 1.2. I am also a larger turbo though. I have almost my entire high load wastegate table set to 100. I did lower high rpm to control boost. I could have used the PID tables to net me exactly what I wanted but I'm street tuning not dyno tuning and I don't care much for driving reckless. Their is a lot of control to be had with all of these tables you just need to find the sweet spot. When I went to 1.3 as my highest it actually slowed me down and so did 1.1. I did a good amount of testing on those tables and I will tell you they are far from stock to match my turbo/bolt ons and my goals. You definitely shouldn't just copy and paste these tables. The only tables I haven't extensively tested are my cam tabmes and thats again because I'd rather not drive reckless. I'll wait til I'm tuning someone on the dyno and do mine as well. I have however seen substantial gains from my setup.

[cobaltssoverbooster]

and people wonder why it was possible to get 315 whp on the factory setup. once the pids got touched hp and trq records got readjusted lol

[MikeM173]

I really think between these tables and the cam tables people would see the best tunes. This is strictly a guess because I haven't fooled with the stock turbo but I feel people don't touch PID at all and I also feel that people don't set up the cam tables correctly. I could be completely wrong.

[DrJones_CMR]

Good stuff guys. I definitely have to read up some more. I'm much more a suspension chassis person than a engine tuner. I leave the tuning stuff up to Lyndon and it's great. Just need to figure out how to get the throttle by wire to act like a cable for some engine braking.
I see Mike has started a PID specific thread and have subscribed to that!

Thanks!
Alex