Pontiac G8 Forum banner

1 - 20 of 26 Posts

·
Registered
Joined
·
1,127 Posts
Discussion Starter #1
A buddy just had a TSP AFM-2 cam installed recently (and a 2800rpm stall), and the tuner left the DoD inactive. We have HPTuners, and I re-enabled the COT and AFM, but it only stays on for a few seconds. I'm wondering if the vaccuum parameters need to be modified due to the mid 220 duration cam in order to keep the AFM active for longer periods.
 

·
Premium Member
Joined
·
1,097 Posts
Yeti is, the tune is by Pat G tho, not sure if he will know off hand.
 

·
Registered
Joined
·
1,127 Posts
Discussion Starter #3
The Yeti is the first person that came to mind, but I knew that Pat tuned his car.
 

·
HPT Pro Tuner
Joined
·
3,815 Posts
Yes, you'll have to adjust the DOD vacuum enable/disable parameters because of the cam.
 

·
Registered
Joined
·
1,127 Posts
Discussion Starter #5
Less vacuum with the higher duration cam, so I assume that I could drop the kpa all the way across in the enable and disable tables? Would 5kpa be enough for a mid 220's cam or am I all wrong here?

Thanks for the help BTW.
 

·
Registered
Joined
·
148 Posts
Less vacuum with the higher duration cam, so I assume that I could drop the kpa all the way across in the enable and disable tables? Would 5kpa be enough for a mid 220's cam or am I all wrong here?

Thanks for the help BTW.
Datalog it and see, run it where you want it to turn on and see what the MAP is. The stock DOD isn't very aggressive. Or add 5 and run it and see how it responds. I'm not a guess and check guy though I like empirical ways of doing it.
 

·
HPT Pro Tuner
Joined
·
3,815 Posts
Engine/manifold vacuum is the difference in pressure between Intake manifold pressure and static map (atmosphere pressure). if map kpa at 60mph is say 55kpa, and assuming static map is 100kpa (you can observe map kpa with engine off, and that would be atmosphere pressure or static map), then you can say vacuum would be 100-55= 45kpa.

Then to play with DOD you can check this thread, i talk about the needed details :)
http://www.g8board.com/forums/showthread.php?t=28312&highlight=dod+tuning

mainly, to keep it longer with stock cam, you'll decrease the numbers in the DOD enable/disable vacuum tables, why ?
Look at the description on the enable/disable vacuum tables,
enable: Engine vacuum level must be above this to allow switch from v8 to v4 mode
disable: If in v4 mode, vacuum level below this would force a return to v8

get the scanner and see what the map is doing in say 6th gear at 50-70mph, then decrease the enable rpm values accordingly. most do it 5 decrements, and about 2-3 decrements for the disable table. i know i used to say tps% had in impact in dod, but futher testing showed me enable/disable vacuum and timing were more important to change than tps%, but as always, test, test and keep testing until satisfied :thumbsup:

Have fun.
 

·
Registered
Joined
·
500 Posts
You may also need to change the throttle % enable disable as well. I believe I changed mine a while ago for a different reason though.
 

·
Registered
Joined
·
1,127 Posts
Discussion Starter #9
Engine/manifold vacuum is the difference in pressure between Intake manifold pressure and static map (atmosphere pressure). if map kpa at 60mph is say 55kpa, and assuming static map is 100kpa (you can observe map kpa with engine off, and that would be atmosphere pressure or static map), then you can say vacuum would be 100-55= 45kpa.

Then to play with DOD you can check this thread, i talk about the needed details :)
http://www.g8board.com/forums/showthread.php?t=28312&highlight=dod+tuning

mainly, to keep it longer with stock cam, you'll decrease the numbers in the DOD enable/disable vacuum tables, why ?
Look at the description on the enable/disable vacuum tables,
enable: Engine vacuum level must be above this to allow switch from v8 to v4 mode
disable: If in v4 mode, vacuum level below this would force a return to v8

get the scanner and see what the map is doing in say 6th gear at 50-70mph, then decrease the enable rpm values accordingly. most do it 5 decrements, and about 2-3 decrements for the disable table. i know i used to say tps% had in impact in dod, but futher testing showed me enable/disable vacuum and timing were more important to change than tps%, but as always, test, test and keep testing until satisfied :thumbsup:

Have fun.
Thanks for all that, and the other replies as well.
 

·
Cars are my hobby...
Joined
·
1,610 Posts
Bluegoat's the man.
 

·
HPT Pro Tuner
Joined
·
3,815 Posts
Thanks a lot guys, glad to be able to help as always.
 

·
Registered
Joined
·
1,127 Posts
Discussion Starter #12
I haven't gotten to play with my buddies cammed car yet, but dropping the enable and disable by 5kpa on my car with the stock cam makes a noticable difference in how long the DoD stays active.
 

·
HPT Pro Tuner
Joined
·
3,815 Posts
Cool, should work the same in the cammed application, although it may need more than -5kpa, depending on high the map kpa is with relation to the old kpa values. You can also increase the DOD timing in the cruising areas, say 1600-2000rpm, (log the g/cyl the engine stays on for this rpm) by 2-3* to increase mpg in DOD.
 

·
Registered
Joined
·
1,127 Posts
Discussion Starter #14
I really appreciate the input on this. I am just learning HPTuners, and want to make sure I do things the right way. To log g/cyl, do I need to add a PID to the scanner, or is this something that is there in the injector data by default. Thanks again.
 

·
HPT Pro Tuner
Joined
·
3,815 Posts
The timing histogram already have rpm vs g/cyl, which is all you need to know engine load at any given speed and gear. Just drive the car at the intended speed/gear, and note engine load (g/cyl) and rpm. With stock cam, the sweet spot would be between 1400-1800rpm, .24-.28 g/cyl, in 6th gear.
 

·
Advanced Member
Joined
·
1,202 Posts
Drop the enable range from 3000 to 2000rpm so the lifters don't enable at higher rpm using a cam. Also increase the hysteria kPa and TPS so it stays enabled better during light throttle changes.
 

·
Registered
Joined
·
1,127 Posts
Discussion Starter #17
Got mine dialed in perfect last night and went for a long drive. I was able to keep DoD active for the full length of the max time - for the first time since I've owned the car. Noticable jump in fuel mileage, and was even able to pull slight grades in the highway and accelerate on flat ground without it kicking out like it would before.

I won't get to work on the cammed car until sometime next week, but again, thanks for the help with this.
 

·
Cars are my hobby...
Joined
·
1,610 Posts
That's awesome! You'll have to report back to us your new MPG over a hwy cruise.
 

·
Registered
Joined
·
1,127 Posts
Discussion Starter #20 (Edited)
Well, I got gas tonight, got right on the highway, and drove approx 15 miles into a strong headwind. Got off the highway turned around and came back. Two way average was 67.3mph and 23.3mpg. I'm guessing that might have been a little scewed towards the low side by starting out into the wind. At the end of the first half of the trip I was only at 19.9, and I'm not sure that it totally averaged out by the time the test was over. I'm guessing that a longer test sample would have shown better numbers because it was still climbing. Regardless, my best before was 22.1mpg.

I had 100 miles on the last tank when I got the DoD set up the way I wanted it, but I still managed 50 more miles on that tank that I usually average.
 
1 - 20 of 26 Posts
Top