How about a mph/retard?

[Highlander]

I would love to see this implemented... Or do you guys have an effective way of doing this?

g/Cyl are pretty much the same between gears at WOT and I can run more timing on 3rd gear than I can on 4th gear. I have data to back up higher timing = more power on the dyno.

[swingtan]

If you have a manual....

COS-5 A0016. set up a switch for when you engage 4th gear.

I thought of this a while ago but never bothered to try it out. The theory is that with the higher ramp rate due to the lower gears, you can run more timing.

Simon

[Highlander]

Nah... I want things simpler... You can run more timing and it feels quicker... but at high gears it will ping and curiously, being on a high gear/higher load doesn't correlate to higher load on the g/cyl table, which it should.

[swingtan]

I think you'll find it's not so much the gm/Cyl but the maximum cylinder pressure. In the lower gears, the pressure is less because it's easier to turn the wheels. I think you may find that you can run higher timing in 3rd at the same vehicle speed, compared to 4th.

[eficalibrator]

Nah... I want things simpler... You can run more timing and it feels quicker... but at high gears it will ping and curiously, being on a high gear/higher load doesn't correlate to higher load on the g/cyl table, which it should.

...but I bet you'll find that it correlates to higher cylinder temperatures when you've been under load for longer. What does your timing vs inlet temp table look like? How accurate is your inlet temp measurement?

I've seen a lot of cases where people flatten out the timing vs IAT function only to have this exact problem. The stock table is structured such that the PCM reacts to any real physical heat soak correctly.

[bobbycollier]

Hi Swingtan. You mentioned using a switch to detect 4th gear... I asked in a seperate post a similar question (should have read before posting ... oh well). Anyway, what switch do you have in mind? The concept makes perfect sense, but I'm just not sure how to get a switch setup to support this. Appreciate your insight!

Thanks, Bobby

[Highlander]

...but I bet you'll find that it correlates to higher cylinder temperatures when you've been under load for longer. What does your timing vs inlet temp table look like? How accurate is your inlet temp measurement?

I've seen a lot of cases where people flatten out the timing vs IAT function only to have this exact problem. The stock table is structured such that the PCM reacts to any real physical heat soak correctly.

That is the problem. Specially when you have CATS, as the hotter the CATS get the less they tend to flow/ for some reason and the car starts to ping also...

Still... My IAT Table is NOT Flat out, but the problem is that in corvettes the faster you are running the lower the IAT gets. At least in what we have of this software we do not have a PE vs Time like the V6 3.8s have which might come handy to avoid detonation and/or heated piston. Still... Even with ceramic coating in the piston crowns you do get this issue of knock on 4th gear only.

The combustion chamber has to get hotter and it gets a lot hotter on 4th/5th and 6th gear than it does at lower gears... Since you spend a LOT more time in Peak HP (peak HEAT output) on the higher gears than in the lower there is a lot more time for things to go wrong.

[swingtan]

Hi Swingtan. You mentioned using a switch to detect 4th gear... I asked in a separate post a similar question (should have read before posting ... oh well). Anyway, what switch do you have in mind? The concept makes perfect sense, but I'm just not sure how to get a switch setup to support this. Appreciate your insight!

Thanks, Bobby

For a manual, I'd set up a "NC" ( Normally Closed ) switch on the sifter that is operated in 1st and 2nd ( once operated the switch is "open" ). Then when you leave the 1/2 gates, the switch will close.

The contacts for the switch would need to be hooked up to the PCM as for a normal NOS activation switch. this will set the PCM into NOS made and allow changes to the timing and fuel mapping. You can retard the timing by a couple of degrees for 3rd and 4th in the NOS tables.

If you then want to "increase" timing for 5th and 6th again, for cruising. You could set up and other switch fro the 5th / 6th gate and wire the 2 switches in series, so NOS mode is only active in the 3/4 gate.

The "theory" seems to hold up on this, but I've never tried it. Setting up switches is going to be interesting, though you could use reed switches mounted on the box and a couple of magnets on the bottom of the shifter.

Simon.