LNF Tuning Question - Cam / Throttle Response Time

Hey Guys,

Have a question here are bout the response time of the camshaft phasing units. Does anyone know how quick these things can adjust the cams? There is a pretty big lag when I drop down a gear or two (say, coming out of a corner pretty hard) and get onto the throttle at all when I'm driving. I'm trying to find the source of this lag to understand it and hopefully tune it out as much as possible. The obvious first answer here is turbo lag, but I don't think that's it. I don't think it is the turbo because the delay / lack of smoothness can be usually solved by releasing the throttle for a second and then getting back on it. Further, my boost gauge shows that there is boost but just no power. From what I can see in the data logs there is nothing funky going on with the spark or KR either, so I starting to get more and more suspicions of the electronic throttle delay or the cam phasing delay.

Maybe as a side note I had a email tune from a tuner a while ago, and the car exhibited the same problem. I started doing my own tuning to get more power, less KR, and in general a lot smoother ride. To do the tuning I followed all of the guides people have made (which are very well done!!) and really haven't done anything over the top. I've also tried and failed numerous times to track the cam advance in the datalogs but have failed. Seems like no matter what I do, as soon as I start recording the log, none of the custom inputs I've defined work anymore.

Any help / thoughts would be appreciated, thanks!

Quote:

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Originally Posted by hockeymandan2828

Hey Guys,

Have a question here are bout the response time of the camshaft phasing units. Does anyone know how quick these things can adjust the cams? There is a pretty big lag when I drop down a gear or two (say, coming out of a corner pretty hard) and get onto the throttle at all when I'm driving. I'm trying to find the source of this lag to understand it and hopefully tune it out as much as possible. The obvious first answer here is turbo lag, but I don't think that's it. I don't think it is the turbo because the delay / lack of smoothness can be usually solved by releasing the throttle for a second and then getting back on it. Further, my boost gauge shows that there is boost but just no power. From what I can see in the data logs there is nothing funky going on with the spark or KR either, so I starting to get more and more suspicions of the electronic throttle delay or the cam phasing delay.

Maybe as a side note I had a email tune from a tuner a while ago, and the car exhibited the same problem. I started doing my own tuning to get more power, less KR, and in general a lot smoother ride. To do the tuning I followed all of the guides people have made (which are very well done!!) and really haven't done anything over the top. I've also tried and failed numerous times to track the cam advance in the datalogs but have failed. Seems like no matter what I do, as soon as I start recording the log, none of the custom inputs I've defined work anymore.

Any help / thoughts would be appreciated, thanks!

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It's not the cams, it's the delay on the ETC.

One way to get around it is by calibrating the DALs, Optimum Torque table and Optimum Ignition tables. I would suggest reading as much as you can on the threads dealing with these tables and use extreme caution.

Watch your ETC % and ETC Desired % in your logs (if you're not logging them, you need to be).

Thanks T-Man. I have stayed away from the whole optimum spark tables due to the fact that they are labeled with "use with extreme caution". However, I'll start looking there. I've definitely messed with the DALs and optimum torque tables though. I do log ETC% and Desired ETC, and the ETC certainly lags during shifts. Again, thanks for the help!

Quick Question, does anyone know how to get the PIDs for the Cam angles to start recording? I've tried all the different PIDs for the cams that I've seen around here.

Digging up the dead. But, since no one replied, are you recording intake and exhaust cam positions in the main table? Without that info, no PID will work.

Hey, thanks for the response..

I'd actually have to go back and look at my tune, but I'm pretty sure I was. I tried everything that I could think of with pretty much no luck on recording the cam angles. On the upside, I was able to tune some of the "lag" I was feeling out, but there is certainly still some there. Once I get around to doing an intake and an exhaust I'll be 100% back in the tuning game again. I'll have to confirm that I was recording the cam angles in the Main table. Thanks!

I've been testing for a couple weeks with Optimum Spark tables. Wanted to finish a few more tests before posting a new thread. GMTech was correct in his first locked thread. I'll explain more in the new one, but Optimum Spark manipulation controls what people call the ecm 'nanny' - throttle lag, boost lag, etc.

I may post a thread this weekend on it.

best to record cams by duty cycle. its easier to see you changes.

we have known the optimum spark tables control the nanny. the problem is not everyone has the money to pay for solid state dyno time to get them correct. same for the dals. you may get both of them in a general spot of great running but to make the ecu so you dont have to touch it anymore takes solid state time that would kill the normal working mans budget. dals control most of the throttle response but the throttle recovery response is optimum spark.

you are on the right path keep going.

eager to read more...

It's a combination of the optimum spark (initial reactive manipulation of boost, tb, wg to pedal input) and the optimum torque tables (in-between shifts). Though there have been a lot of writeups, all over the place and some AMAZING input by you (cobaltss), gmtech, and a list of others, the threads are still cryptic in how these most important tables relate. That's why I was going to do another thread covering:

optimum spark - throttle pedal input vs touchiness and its effects on boost, etc. I've seen gmtech's original explanation (which was great), but have yet to see the correct manipulation of this table explained. That's important for other people who don't want to just start experimenting on an open track.

optimum torque - affects the speed at which throttle blade reacts to pedal input + recovery in between shifts (that' brap brap brap pausing). Correct tuning here lets you mash pedal for instant response instead of having to roll into it. I've read a ton of threads but have yet to see this discussed or explained.

WGDC - combined with boost control it controls boost, but it also will eliminate off-throttle boost spikes. You can adjust it so far that it causes off-throttle boost DIPS (yes, boost dip)


All the LNF work here has been phenomenal, but there are still some unexplored/unexplained areas of tuning which have not been discussed. The general whereabouts have been, but not the HOW.

Over the last couple weeks of constant testing, I've found that proper opt spark has given me the near-instant response to a LIMIT (50-98% throttle blade opening speed @ WOT hits a threshold of ~1.0x sec). The speed beyond this is controlled by the optimum torque table.

I've also figured out what parts to manipulate for race tune while leaving cruise very streetable. The how of this hasn't been discussed. I think it's pretty important to lay this out for these tables rather than just say 'we know what it does'.

You don't need a solid-state or any other dyno to get these tables dialed. You can do it with the scanner, the 'how' of which I was going to describe in another thread. For anyone who has scanned a WOT pull, You'll notice a) the throttle blade response does not mirror throttle pedal as boost builds; and, b) it has 'stall' points where it tends to flatten out for a little bit. Those can be fixed/eliminated.

I have the lnf file in a file editor and there are tables hidden that will amaze everyone. Problem is I haven't verified any coding changes to grunted their operation. So far out of the mess I have been trying to sift through I found 5 tables we don't have control over.

All of my open work (5 axis cnc and solid flow simulated head, solidworks designed injector spacer for cars requiring secondary fuel sources, and a revised solid lifter for the cnc head changes) will be coming to an end as I will be making my last lnf tune next week on Thursday. There are a few of you guys out there re solving the issues we discussed a long time ago and its going great places. Hopefully all of those people continue to help the rest of the lnf group out down the road.

Keep pressing forward and good luck.
Cssob

Still more testing I need to finalize before I do a writeup. Then, I'll explain the relationships better between opt spark, opt tq, DAL, & WGDC from what I've found.

Haven't seen anyone mention the effects of opt spark on gas mileage at cruise. With it set right I can get it to hold low-to-mid 40mpg during cruise (60-70 mph) with light throttle. I've also gone the wrong direction and seen it cause instant drop to low 20's mpg range with slight throttle variation. All testing has been done with no cam table changes.

Steady state calibration net me 42 at cruise for around town total of 35-36 combined

4th gear 35-40mph cruising I'm in the 47-52 range. Interesting so far how manipulating the opt spark will shift that around. Have to 'relearn' what the optimal rpm is for efficiency with changes.

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Originally Posted by cobaltssoverbooster

I have the lnf file in a file editor and there are tables hidden that will amaze everyone. Problem is I haven't verified any coding changes to grunted their operation. So far out of the mess I have been trying to sift through I found 5 tables we don't have control over.

All of my open work (5 axis cnc and solid flow simulated head, solidworks designed injector spacer for cars requiring secondary fuel sources, and a revised solid lifter for the cnc head changes) will be coming to an end as I will be making my last lnf tune next week on Thursday. There are a few of you guys out there re solving the issues we discussed a long time ago and its going great places. Hopefully all of those people continue to help the rest of the lnf group out down the road.

Keep pressing forward and good luck.
Cssob

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won't amaze everyone, just most. :)

you won't see those tables come to light due to the contract between hpt and their acquisition of the a2l coding and gm saying yes and no to certain things to be made public. politics are fun!

Care to elaborate on these 5 tables? Function?

Passed entire project to someone else. Sorry but I'm out.