VVT phaser control

[98 SS]

Would anyone know or be able to find out what the hz range is for the PWM VVT solenoid?

I know that with no power applied, the pin is relaxed which results with the cam being locked at 8.5* advanced. I would like to know the hz range that is used to retard the cam from the 8.5* advance to 22.5* retard.

Also, if anyone has any info on a general VVT setting that would be good to start at for idle and where to finish off at around 6k rpm that would be helpful.

Im working on a module for a carbed L76 that will start with the cam advanced and then retard it throughout the rpm range.

[98 SS]

Could someone look at a tune with VVT tables and see if there are values listed in the description?

[mbray01]

there are plenty of stock files in the repository that will give you all the info you need. Different years and model had different actuators, and different maps for those. Some were at 8.5 rest, some 7, and I believe some were at rest in a retarded position. Find a stock file that is exact for what you have, then try to get the info from there

[98 SS]

there are plenty of stock files in the repository that will give you all the info you need. Different years and model had different actuators, and different maps for those. Some were at 8.5 rest, some 7, and I believe some were at rest in a retarded position. Find a stock file that is exact for what you have, then try to get the info from there

I don't have HP tuners anymore. This is an L76 out of an avalanche. It has the 8.5 degree park to 22.5 advance

Im going to keep it around 7.5 degrees advance at idle, retard to 5 degrees at 3500, the retard to -4 at 5000, and -9 at 7000. That's an ish based on what ive dug up for optimums. Might even include a multiplier based on TPS and RPM to retard significantly for light load cruising. What im really looking for is the hz range that the magnet works through.

Maybe bill could help?

[mbray01]

I don't see anything in any files I have about how it actuates, options i see are for modifying when and how much adjustment. I don't believe hptuners lets you have those tables

[98 SS]

Alright, thanks! Is there anything listed on the description of the VVT tables? When you hover over the table button or have it selected without opening it and I remember there being a description that popped up in the lower right somewhere? I didn't know if that would only give you the table range of whatever the axis' are or if it would give you the PWM range.

[98 SS]

Oh, and I was just looking at your VVT thread! Im guessing there is some sort of multiplier for spark that goes with your VVT tuning? I doubt I will be able to pull that off with the carb/msd setup.

[mbray01]

Well, my file I started pulling 2* at 4k, through 12* at 6k rpms. With spark I removed all spark adders with vvt before 4k. then I extrapolated the spark into the higher and lower map regions. Seems to work well. not getting any kr. on my file for cam retard only says 0*-52* of full retard, sorry no pwm, I limited mine to 12*, as mine is a fairly large cam for the setup. Maybe contact hp support and they could give some insight into the script.

[mbray01]

I did a little research here about this. Usually gm will publish pwm plotting when it comes to their systems, ie fuel pumps, pressure control solenoids, however for this I do not see anything at all, just says it advances or retards with pwm, which leads me to believe, there is no set Percentage, or frequency for a specific position. If you watch the actuation with a scanner, it does not head straight to the commanded position, instead it creaps up to it, and a little after, basically looks like it is searching for it. The cam position is constantly changing, throughout the rpm range, even if only .5* but it constantly moves, I beleive this is due to the change in oil pressure, with change in rpm. More oil pressure=less hertz required to maintain the same position.

So to answer your question, from what I see, there are no concrete frequencies that you can plug in to command a specific cam degree. You might be able to map something that will get close, but it would have to be 3 dimensional, accounting for; rpm, oil pressure, oil temperature. And that is assuming that the viscoscity of the oil remains the same, with fuel contamination. I think the computer does it by monitoring camshaft position, and actuating the solenoid to keep it as close to steady as possible.

I think you could try this, get everything going apply say a 25% signal to the pwm solenoid on the cam, which in theory should give you 25% retard. monitor cam position, with a scanner, see where it sets, then make a couple throttle snaps and see if it moves, I believe it is going to be all over the place based on oil pressure

[98 SS]

I think im confused on what Im looking for. Its not HZ, but % of modulation that I need to know. Im guessing that the max extension for the solenoid is less than 100% cycle since 12v for more than 2 seconds can damage the solenoid.

So to answer your question, from what I see, there are no concrete frequencies that you can plug in to command a specific cam degree. You might be able to map something that will get close, but it would have to be 3 dimensional, accounting for; rpm, oil pressure, oil temperature. And that is assuming that the viscoscity of the oil remains the same, with fuel contamination. I think the computer does it by monitoring camshaft position, and actuating the solenoid to keep it as close to steady as possible.

Hmm, well that throws a kink into things. Gotta mull that over for a little bit.

[mbray01]

sorry, not hertz, brain sneeze. Yes percentage, apply a 25% duty cycle to the solenoid, and monitor with scan tool.

[98 SS]

Bad part is there is no scan tool here. This is a carbed setup. So now I need to figure out how to read a 58x and 4x wheel set and make some sort of function that reads the actual cam position, then compares it to a table that has the desired cam position, then have it command whatever is needed to line them up...... getting more difficult.

[mbray01]

I thought my troubles with the vvt were giving me fits, I can only imagine yours. While poking around about this, on ls1tech, I saw alot of posts from guys having basically the same setups as you, and either they left the cam alone, or deleted it with non vvt stuff. Their claims were that the cam retarding only gave negligible hp gains with a carb, a few claimed quite a few dyno hours trying to make it work, and found very few hp, definitely not worth the effort. then there were others who claimed huge numbers of hp, when the revs started getting up to 8k. But most didn't go into detail about making it work. Right now vvt seems to be a black art. It's hard to get good information. with my other thread, I got a few emails, with apparently some very bad information, so I guess, until someone publishes a guide explaining all the ins and outs, we are kinda left guessing

[98 SS]

I think a lot of people just delete it for the very reason that it is a dark art for the time being. But in all honesty, guys have been doing cam degree changes since racing began. Its a way to change your powerband based on track settings. Its a lost art right along with proper carb tuning. And there is definitely some power to be gained, but the big advantage is not having to give up peak hp to make peak tq or vice versa....you can have both. So while the gain on one might not be all that high....remember that your not sacrificing the other. This can be seen by strapping down to a dyno and commanding a constant cam position and finding what value gives max tq and what gives peak hp. And imagine a more aggressive grind cam designed for vvt....but that didn't have to worry about the issues associated with aggressive cams and efi. It may not be ideal for a max effort motor....but its a pretty wicked little idea for a carb street motor I think. Maybe its a dumb idea....I dunno..... but for $50 bucks and some garage time....I think it can work.

[mbray01]

Yes I agree, I have been building circle track motors for about 15 years, and yes setting the cam just right is essential I always kept 3 pc timing covers and handfulls of offset cam degree kits. in 1/2 degree increments, ready for dyno time. Of course with that you are looking at a specific power band within a specific range. Yes a lost art, but was essential to what was needed. 15hp made all the difference with class rules and limited carbs. I think with these new vvt setups we are getting into something that scares alot of people. I know there are guys doing it wrong, and those doing it right. I have a large fairly large cam in a truck I am doing now, maybe not large for racing standards but for a na street motor pcm sees it as a 104 lsa cam. which is very substantial. I want it to pull stumps down low, but be able to retard it top end so it doesn't fall off. It seems dialing it in like "I" want is the hardest part. Where I have it tuned now I believe would satisfy 99% of all customers, but because I am only happy with perfection, I demand it for my customers.

I thought about your situation and I wonder iif there isn''t a simple solution. It will be hard to make repeatable every single time, but I think it will keep you close. I believe if you set a specific pulse width say 25% lets use even numbers so say you have a theoretical 50* swing of the actuator. 25% should give you a 12* somewhere in the oil pressure spectrum. Now my thoughts if you actuate the solenoid say starting at 2500rpms you wont have full 12* it will be less, but as rpms increase so will pressure, and thus timing retard. which will probably be more than 12*i would guess at 14-16* which would put you at about 6-8* retard with a stock cam would probably be right in the power band. Now of course in theory how I would guess this to work. I just think this would be easier to do on a dyno, playing with pwm vs. trying to map cam vs crank signals to monitor the signals. just a thought

[Maxirat427]

I'm curious about the static position of the cam on VVT engine. I see you discussing them at about 8* advanced. I have a L76 truck engine swapping into a non VVT truck and I was wondering the effect of just leaving the VVT disconnected. Does applying power to VVT solenoid retard or advance the cam ('08 L76 GMC Sierra). If you are applying power at higher rpms looks like it would retard the cam. Therefore, in a stock application the truck would run fine with VVT solenoid disconnected, you would just give up a little top end hp? Low end torque would not be affected? Don't want to have a dog on the bottom end.
This has had me pulling my hair out last few days, as this was not supposed to be a project. It's my wife's daily driver.

Thanks for any input.

[mbray01]

not exactly sure why you would want to disconnect it entirely, unless you have a specific cam, and then you would want a differnt chain and cover assembly. My advise is to play with cam timing and see what works best.

[reddevil96]

I have been playing with this VVT stuff in my 2010 escalade L94 6.2L, I am pulling in 2* increments from 2800rpm and at 6k and up rpm I am at 15* retarded on the table, which would put me about 6.5* retarded on the cam. I still trying to play with the highway cruising rpms for a little bump in gas mileage, but in doing so, it acts like turbo lag when it leave the cruising range and then into the higher rpms.