Basic VVT Tuning info

[viceroykarl]

Everything you wrote was also correct, except for one word, ADVANCE. That part you got backwards. If you RETARD cam timing, it does everything you mentioned, and yes, you have to retard the exhaust cam also to keep overlap in check. Those numbers in the tables are retard, not advance. In general, you want to advance at low rpm's and retard up high. (In general) In most NA tunes you'll see an overall RETARD of the cam(s) as rpm's rise. Too much compression up high will make a motor hard to rev out.

I'm not too sure those are retard numbers though, those numbers show a downward trend towards 0 as the rpms increase on the stock table, even in events that would be satisfied by WOT. In terms of retarding it are you talking about moving it back so far that it'll open the intake port after the cylinder is heading down and closing it when its headed back up?
I was thinking the other way by opening it sooner before its all the way back up and closing it before its made it to the bottom. Although the other way makes more sense meow that i think about it so that its not putting exhaust in the intake

[gmtech16450yz]

This might help.

Camshaft Position (CMP) Actuator System

The camshaft position (CMP) actuator system is an electro-hydraulic operated device used for a variety of engine performance and operational enhancements. These enhancements include lower emission output through exhaust gas dilution of the intake charge in the combustion chamber, a broader engine torque range, and improved fuel economy. The CMP actuator system accomplishes this by changing the angle or timing of the camshaft relative to the crankshaft position. The CMP actuator simply allows earlier or later intake and exhaust valve opening during the four stroke engine cycle. The CMP actuator cannot vary the duration of valve opening, or the valve lift.

During engine OFF, engine idling conditions, and engine shutdown, the camshaft actuator is held in the Park position. Internal to the CMP actuator assembly is a return spring and a locking pin. During non-phasing modes of the camshaft, the return spring rotates the camshaft back to the Park position, and the locking pin retains the CMP actuator sprocket to the camshaft.
CMP Actuator System Operation

The camshaft position (CMP) actuator system is controlled by the engine control module (ECM). The ECM sends a signal to a CMP actuator solenoid in order to control the amount of engine oil flow to a Cam Actuator passage. The pressurized engine oil is sent to unseat the locking pin, and to the vane and rotor assembly of the CMP actuator. There are 2 different passages for oil to flow through, a passage for cam advance and a passage for cam retard. The Cam Actuator is attached to a camshaft and is hydraulically operated in order to change the angle of the camshaft relative to crankshaft position (CKP). Engine oil pressure (EOP), viscosity, temperature and engine oil level can have an adverse affect on Cam Actuator performance.

[cobaltssoverbooster]

This might help.

bahahaha i thought my graph came and went....its back from the dead!! do realise these are installed and measured at a complete rest position engine off and sitting for 2 days, no oil present in the actuators!

[gmtech16450yz]

Was that yours? I had no idea where I got that from! Lots of this cam stuff I researched awhile ago and I forgot half of it since then! That graph does do a good job of showing cam events, Thanks!

Like I said earlier, there's hundreds of theories and ideas on cam timing, especially on a dohc motor with a turbo and direct injection. You can drive yourself batty and end up with cam tables that seem to make sense in theory, but are a mess in actual use. I think the bottom line on LNF cam timing is the factory tables aren't great, but they aren't that bad either. It's all a compromise, there are gains to be made, but they may take away something somewhere else. MPG's can be drastically effected, up and down. Throttle response can be improved, sometimes to the point of making it SO responsive you have to tame the throttle mapping. It just depends on what you want. Here's some of my tables that are a pretty good compromise between throttle response and mpg's. My Kappa turns right around 2500rpm at 65-75mph, and between 40-70% airload. I've retarded intake and exhaust around that area to maintain a good mileage, which it absolutely does. But as soon as you go up in airload or rpm's, they go back advanced to give that torque and response. Try 'em if you want...
edit- Remember, make all the cam tables the same- cold, warm, cat warmup, etc. Same with idle tables, make them all the same. Oh and CobaltSS (name?), try driving a Kappa. I've owned over a hundred cars and driven damn near everything, this Sky Redline is one of the most fun cars I've ever driven. Rear wheel drive, short wheelbase, conventional a-arm suspension, coilovers, solid frame, tight steering and brakes, 2900lbs, hella power, good traction and it still gets awesome mileage! No trunk space or back seats, but that's what my truck is for. Try one if you haven't already!

[viceroykarl]

I tried adjusting the stock table to copy the mpg trend to lower rpm states to cover cruising at 45mph. I'll see how that works out when i flash it over. should at least give me an idea of whats going on in the table. I think the le5 table works a little different from the lnf since my numbers can only be input from 0 to 128*
If the table is degrees of retard rather than advance im still wondering why as rpms increase the numbers move from high to low. Everything i've read so far says retarded intake/exhaust gives high rpm power.

attached are intake and exhaust tables for cam

[silverbullet08]

try driving a Kappa. I've owned over a hundred cars and driven damn near everything, this Sky Redline is one of the most fun cars I've ever driven. Rear wheel drive, short wheelbase, conventional a-arm suspension, coilovers, solid frame, tight steering and brakes, 2900lbs, hella power, good traction and it still gets awesome mileage! No trunk space or back seats, but that's what my truck is for. Try one if you haven't already!

These are very close to the ones im working with. Im trying to see how much more we can squeeze out up top though as well. You have a little more retard in your intake cruize section. I had a little issue when i put my clutch in so im working on getting that fixed before i can experiment any more. No one happens to have a engine harness for the Lnf do they? lol

I would love to own a kappa! lol Im so jealous! I have always wanted one of those platforms.. especially the redline.

[cobaltssoverbooster]

Was that yours? I had no idea where I got that from! Lots of this cam stuff I researched awhile ago and I forgot half of it since then! That graph does do a good job of showing cam events, Thanks!

Like I said earlier, there's hundreds of theories and ideas on cam timing, especially on a dohc motor with a turbo and direct injection. You can drive yourself batty and end up with cam tables that seem to make sense in theory, but are a mess in actual use. I think the bottom line on LNF cam timing is the factory tables aren't great, but they aren't that bad either. It's all a compromise, there are gains to be made, but they may take away something somewhere else. MPG's can be drastically effected, up and down. Throttle response can be improved, sometimes to the point of making it SO responsive you have to tame the throttle mapping. It just depends on what you want. Here's some of my tables that are a pretty good compromise between throttle response and mpg's. My Kappa turns right around 2500rpm at 65-75mph, and between 40-70% airload. I've retarded intake and exhaust around that area to maintain a good mileage, which it absolutely does. But as soon as you go up in airload or rpm's, they go back advanced to give that torque and response. Try 'em if you want...
edit- Remember, make all the cam tables the same- cold, warm, cat warmup, etc. Same with idle tables, make them all the same. Oh and CobaltSS (name?), try driving a Kappa. I've owned over a hundred cars and driven damn near everything, this Sky Redline is one of the most fun cars I've ever driven. Rear wheel drive, short wheelbase, conventional a-arm suspension, coilovers, solid frame, tight steering and brakes, 2900lbs, hella power, good traction and it still gets awesome mileage! No trunk space or back seats, but that's what my truck is for. Try one if you haven't already!

names alex and ill be staying in the lnf cam learning even if i dont own one anymore just because its future happy potter shit haha just saying i may want a new car but i love how complex this is. anyways now that was my graph....the first time i blew my turbocharger i had a minor cover leak so i popped her off and inspected everything... i mean who wouldnt look at something they havent seen i opened my box and set up the ol degree wheel and took a lobe profile then measure the durations and opens at the valve to acheive max lift values. plus by getting the lobe profile i was able to establish the gm rocker ratios. this resulted in information for head porting when the second turbo decided it would be cool to drop another journal on me. and now im stuck with this ported disaster and no rttuning or a ssdyno to figure stuff out quickly.

my uncle and a tuned stg kit solstice it was indeed fun but i want trunk and a little bit more space...no doubt in my mind they are def on my faves list

[cobaltssoverbooster]

see its my chart haha


factory




mine



plus mani haha

[silverbullet08]

Im suprised you havnt had much luck with that head..? I bet it would make a bigger difference with a bigger turbo.

[Leafy]

I think the issue is with how the ports in a DI head have to work.

[cobaltssoverbooster]

I think the issue is with how the ports in a DI head have to work.

Im suprised you havnt had much luck with that head..? I bet it would make a bigger difference with a bigger turbo.

#1 is most correct so far....#2 yes it flows way over the factory turbo capabilities and i need an efr to make this work great.
but #3 which is my opinion and findings is the factory head port swirls the air into the chamber for best atomization, but besides that point i can bring alot of power back with the cams and i am still having problems getting them into their sweet spots which could be faster if i had a dyno i could run for a weekend without maybe killing my pocketbook. all these street pulls are gonna get me in trouble not to mention hard to come by with all this traffic.

[silverbullet08]

#1 is most correct so far....#2 yes it flows way over the factory turbo capabilities and i need an efr to make this work great.
but #3 which is my opinion and findings is the factory head port swirls the air into the chamber for best atomization, but besides that point i can bring alot of power back with the cams and i am still having problems getting them into their sweet spots which could be faster if i had a dyno i could run for a weekend without maybe killing my pocketbook. all these street pulls are gonna get me in trouble not to mention hard to come by with all this traffic.

yea dyno time gets expensive. Ive done all my tuning on the street which i believe is better in a way. If you think about it yes a dyno can replicate the same load your car should be seeing on the street but it can only get so close. On a dyno you dont get the bumps, up/down hills, change in wind conditions, temperature variations, depending on your intake the amount of air being blown around the filter at high speeds. Yes you can make a pretty good tune on a dyno so dont think im saying its pointless, it would be perfect for your senerio where you need a place to do abunch of pulls with no trouble and get a good close tune. But i believe to get the smoothest and most versitile tune you need to do the fine tuning on the road where the car will be driven... not a dyno.

[silverbullet08]

So here is the set im using currently. If you see room for improvement then feel free to bash. These tables make the car run soooo smooth and still makes good power, i average 28-29mpgs at 70-75mph and mpgs climb majorly at lower speeds "still above 2k" GMtech, your car has a different gear ratio than the balts so your cruize rpms are different. Not sure if everyone else has cought on to that. Thats why my MPG humps are a little wider and further south. The car makes awsome power on these "i pulled on a C6 ZO6 with exhaust with these tables tonight". I included a overlap shot of these tables on the bottom. Gmtech i think i remember you saying less overlap in cruize is what you want for mpgs correct? il double check but based off of these im netting more mpgs with a little overlap in the cuize section. i may have what you said backwards. My goal is to design a set that has smooth overlap transitions but still has good power and economy these are still a little bumpy in spots based off the overlap table.

[gmtech16450yz]

Copy the entire 3500 to 4250rpm rows and paste it one row lower. Basically you have three rows of retard on your intake cam and only two on your exhaust. Widen that exhaust retard area and it will help smooth your overlap. BTW, your overlap numbers don't seem to add up right?

Ok here's a comparision between stock and the tables I'm running as far as overlap... (stock on left, mine on right.)




Somebody try to explain to me what GM was trying to do in the stock tables as far as overlap goes? Like I said, sometimes you can theorize to death and think you have it all figured out, then you look at what the engineers came up with and it makes no sense. They do have many other factors to deal with though.

Stock Kappa's freeway cruise in the 2k row, between 40 and 50% load. (screenshot below) So why in the 2k row do they have 0 in the 30% cell, -10 in the 40% and -15 in the 50% cell? (as far as overlap) This is where it all gets tricky. You have to remember that reducing pumping losses and getting the "EGR" effect are not mutually exclusive. If you have NO overlap, it doesn't matter where the retard or advance is, you still won't get any exhaust reversion because the valves will never be open at the same time. If you have a ton of overlap, it will depend on where the timing is as to whether you'll be getting exhaust or intake reversion. A lot of overlap on a boosted motor, you could be blowing the charge out the exhaust port when the intake and the exhaust are both open. Trying to create no overlap by timing the exhaust too late and you'll be loosing compression. Too much overlap at high rpm's when the turbo is in hair drier mode and the exhaust back-pressure is super high and you'll have a fight between the intake charge and the exhaust charge. Not enough overlap and the cam timing events will be either too early or too late. AAAAAAHHHHH! My head is gonna explode just thinking about it!! Then add in what cam timing does to EGT's, wear on lower end bearings, etc, and it gets crazy.

Here's been my theory, don't go too far away from stock except for where you want some dynamic compression and to eliminate the EGR effect for better torque. Try to keep overlap somewhat low, that way you don't risk exhaust or intake reversion issues as much. Don't try to get too much dynamic compression up high, it will make the motor not want to rev out as easily. You can have plenty down low, as long as KR is in check. There's little downside to lots of dynamic compression down low, as long as you have good fuel to support it. Remember, I never said I was the All-Knowing cam expert, so some of these things I've said could be completely wrong. If there is an expert on cam timing, ESPECIALLY on an LNF with dohc, DI and a turbo, I'd like to meet him! He's either a liar and doesn't really know everything or he's the one making 6 figures at GM or Bosch engineering all this.

Cell hit count, freeway cruise drive in a Kappa. Yes, the Cobalts will be different because of gear ratios, and mine will probably be even a little lower than most Kappa's because I have huge back tires. These numbers are from a bone stock LNF Kappa with stock sized tires. Set up a histogram with the same rpm and load axis as the cam tables and see where yours runs.

[cobaltssoverbooster]

^i coppied your first posed cam tables and saw the 1 row difference and modified it for this weekend and then proceeded to not upload it but record it like i did upload it. yes i know DUNCE! hahaha anyways ill post a log of it to show how it works on the port job.

[silverbullet08]

[QUOTE=gmtech16450yz;264443]Copy the entire 3500 to 4250rpm rows and paste it one row lower. Basically you have three rows of retard on your intake cam and only two on your exhaust. Widen that exhaust retard area and it will help smooth your overlap. BTW, your overlap numbers don't seem to add up right?

Somebody try to explain to me what GM was trying to do in the stock tables as far as overlap goes? Like I said, sometimes you can theorize to death and think you have it all figured out, then you look at what the engineers came up with and it makes no sense. They do have many other factors to deal with though. [QUOTE=gmtech16450yz;264443]

I changed it like you said. Makes since i guess i just didnt see that lol. My overlap doesnt seem to make sense in areas...? your adding 6 to the exhaust and subtracting 10 from intake correct?

Gm must have some reason for the wierd overlap table.... or maybe its just a flaw? Im guessing the kappa tables are different or your using a different year. My factory over lap at cruize is like -4 to -19 meaning a little over lap then 0 overlap under more load.... Which actually does make sense. Your lowering compression under light load then raising it when you hit higher load. So less power until you hit higher loads or "more pedal" for more power. But there are other areas that are still off the wall.... heres a copy of mine. THe more I look at the factory cam tables the more i like them and understand. With a few minor adjustments you could really have a good set of tables lol. I bet im just catching up with everyone else on this.

[cobaltssoverbooster]

so i was like y is my car making no torque.......studied that shit hard as fuck for an hour .........and found i was running 6* timing in boost comanded. apparently i forgot to turn it back up. so i ran the cam changes as gmtech posted with the cobalt adjustment rows and got this run. she spins second decent....not good and fun like she used to but decent. and the recording here is a pull through third gear where i found out truely how high the boost level was hahahaha and im still running 12* under this boost level hahah wtf!

40.9 psi with the boost lo res as a sensor in the histo thats up. ouch kick in the balls.

[96sunfire]

Unless you're running 15lb. of boost at idle, it looks like your forgetting to subtract 14.7 (one atmosphere) in your PID...

[Gremlin85]

I'm having such a hard time wraping my head around the cam tables. I am running a older posted set of GMTech's cam tables from a while ago.

I'm thinking I might just revert back to completely stock cam tables.

I've just been aiming at getting the maximum power I possibly can.

[oldskool]

This is quite possibly the best thread I've read on LNF tuning - thanks guys for the contributions!

One question i have is with respect to overall advance/retard. I somewhat understand we have a difficult task of tuning n/a out of boost and also in boost as Gmtech described. It also seems like everyone agrees to some extent that overlap is the enemy of making more power in boost, but what about moving both cams in the same direction? This may come more from the n/a camp, but "in general" doesn't overall retard make more power up top, and overall advance makes more power down low? I would imagine making changes in this vein would only happen in the high load columns...