Part Throttle SOI Tuning

[lucas287]

There's a lot of talk on here about SOI tuning/considerations for WOT. But not much about part throttle tuning where I spend most of my time. I've seen @GHuggins address this a time or two but he's MIA.

Is there any benefit to messing with SOI for part throttle driveability/MPG gains?

I've zero'd out my VVT tables below 2800 RPM. Since there doesn't seem to be a VVT SOI table specifically it appears that this bump (pic attached) in the base SOI table is for VVT cam retard purposes.

Do I just need to watch Greg's video? Assuming he address part throttle of course.

Thanks!

SOI.JPG

[lucas287]

bueller.jpg

[TriPinTaZ]

If you're looking for part throttle fuel mileage you should put the VVT tables back to stock. You aren't going to find any MPG gains with SOI. The ECU will add/subtract to the SOI as it sees fit so adjusting the table isn't the final say anyhow.

[lucas287]

IThe ECU will add/subtract to the SOI as it sees fit so adjusting the table isn't the final say anyhow.

Very interesting! I wasn't aware of that. Guess we only have access to so much. I hear you on the VVT settings. It has had an appreciable negative impact on fuel economy. The throttle response/torque is just so good though!

[cmitchell17]

I thought the latest consensus with the SOI was that you should just leave it entirely stock. I am not sure if that means if you have a huge cam not even check anymore if your exhaust or intake valve is still open when SOI occurs or what?

I know some "tooners" add like 20 degrees to the whole table and have "confirmed gains".

[lucas287]

I thought the latest consensus with the SOI was that you should just leave it entirely stock. I am not sure if that means if you have a huge cam not even check anymore if your exhaust or intake valve is still open when SOI occurs or what?

I know some "tooners" add like 20 degrees to the whole table and have "confirmed gains".

Exactly - IDK either man. For now, I just put my VVT table back to stock. Really does seem to run smoother like this.

Not looking for anyone to give away free advice since a lot of this knowledge seems to proprietary. Just curious if I'm on to something and, if so, what rabbit hole should I go down.

[tunerpro]

I thought the latest consensus with the SOI was that you should just leave it entirely stock. I am not sure if that means if you have a huge cam not even check anymore if your exhaust or intake valve is still open when SOI occurs or what?

I know some "tooners" add like 20 degrees to the whole table and have "confirmed gains".

There's a lot of variation between the OE SOI calibration strategy - I have seen some applications where advancing the SOI at WOT made a measurable improvement on the Dyno, other applications had no effect at all. You have to try it and measure it on the Dyno to find out.

[Ben Charles]

I thought the latest consensus with the SOI was that you should just leave it entirely stock. I am not sure if that means if you have a huge cam not even check anymore if your exhaust or intake valve is still open when SOI occurs or what?

I know some "tooners" add like 20 degrees to the whole table and have "confirmed gains".

If they do that they are most certainly shooting fuel out the exhaust valve and skewing there lambda reading...
The bigger the cam typically (exhaust valve closing) this gets worst

[cmitchell17]

Just to clarify, you are saying if they are adding 20 degrees to the SOI table they could be shooting fuel out the exhaust, with the bigger cam (earlier exhaust opening) makes the problem worse? If I remember correctly increasing the SOI in that table makes the event head more towards TDC?

[grandam75]

As I understand it, problem with bigger cam is later exhaust closing. If you increase numbers in the SOI table the spray will start earlier and may spray when exhaust valve is not yet closed.

[Ben Charles]

As I understand it, problem with bigger cam is later exhaust closing. If you increase numbers in the SOI table the spray will start earlier and may spray when exhaust valve is not yet closed.

Correct