Tuning ?????

[clementeunknown]

I am still learning how to use my HP Tuners here are some rookie questions. Thanks in advance.

1. What is considered the limit of spark advance during WOT? Right now I'm at about 23*-25* through the rpm band. It's a completely stock 4.8 other than tune.

2. What does detonation sound like? I know I can see Knock Retard on the VCM scanner but what does it sound like? Is it a rattling noise?

Thanks.

[Sleaper]

What fuel are you running? Premium?

Detonation sounds like pinging. If you are seeing knock on the scanner at WOT, you need to adjust something, probably timing.

[ChubbyBuddy]

Watch your KR at WOT you may be able to get 28-29 on the 4.8.Ive seen 32 on a 5.3 before!

[George C]

timing is all part of what the vehicle wants. theres just not one set number

[Madd Maxx]

Yup - what he said. Timing is one of those parameters where more is not always better, even if you don't have detonation. Timing should be set so maximum cylinder pressure occurs 12-15º ATDC. Too little timing and the piston's on its way down before maximum cylinder pressure occurs - you lose power. Too much timing and maximum cylinder pressure occurs too soon, which incurs a pumping loss as the piston has to compress rapidly expanding gasses - you lose power.

Where timing needs to be set is a function of piston design, combustion chamber design, and the fuel used. The only way to really know what timing is needed for your truck is to put it on a dyno or take it to a drag strip and adjust based on trap speed.

[clementeunknown]

Well i adjusted the high octane spark table and copied it to the low octane so I'm running on 93 octane. I know each engine would take different amounts of spark advance since not all are going to respond the same but I just wanted a ball park figure to know if I'm pushing the engine to the limits or if I can push it more. Right now there is no KR at all on the VCM scanner. My spark advance peaks at 25* right now but averages about 23*, by your replies I'm guessing it's pretty conservative right now. But I guess I have to mess with it more see how the truck reacts.

[George C]

old school rule of timing. add timing till vehicle pings and reduce it by 2*

or keep adding timing till vehicle noses over then back it off some

since not every vehicle will ping with XX amount it will however nose over as mentioned by maxx


increase timing everywhere you have a load even at 1500 rpms it helps. just keep eye for KR meter and ear for pinging. keep adding till it doesnt pull anymore then back it off some

[straightaxle]

detonation sounds like golf balls in a coffee can

[clementeunknown]

old school rule of timing. add timing till vehicle pings and reduce it by 2*

or keep adding timing till vehicle noses over then back it off some

since not every vehicle will ping with XX amount it will however nose over as mentioned by maxx


increase timing everywhere you have a load even at 1500 rpms it helps. just keep eye for KR meter and ear for pinging. keep adding till it doesnt pull anymore then back it off some

10-4

[txarkitekt]

old school rule of timing. add timing till vehicle pings and reduce it by 2*

or keep adding timing till vehicle noses over then back it off some

since not every vehicle will ping with XX amount it will however nose over as mentioned by maxx


increase timing everywhere you have a load even at 1500 rpms it helps. just keep eye for KR meter and ear for pinging. keep adding till it doesnt pull anymore then back it off some

+1. Since no KR, then increase timing little by little. Its all about taking the time to go log your vehicle and making several runs. Since most tuning runs occur back to back, you should be able to feel a difference in each different tune. Just be sure to watch for your injector duty cycle and fuel trims as well.