Turbo Tuning Help

[jckleewein]

My 4094R turbo has a lot of lag in it at 5800’. Correct me if I am wrong, but my understanding is that decreasing the timing table down low will help spool the turbo quicker. My question is how far out in the table should this adjustment be made (to 1400, 1500, 1600 RPM)? And at what mm3 value should I start adjusting at? How safe is it to use negative degree angle numbers?

[Dozerboy]

Not that I'm any expert and I have a stock VVT, but I would start under 70mm3 and 2400RPMs. From there your going to have to do a lot of logging. EGTs should tell you how low you can go retarded timing = heat.

[jckleewein]

I am planning on doing some testing here pretty soon.

[LBZoom]

I'm not certain that lowering timing would help spool or not, I suppose it would in the sense that more fuel injected after the cylinder has reached TDC would potentially generate more heat and create more pressure to spool the turbo, but it may create some smoke here and there if you went too far, and you also run the chance of losing power and efficiency perhaps even more.

Maybe try squirting a little extra fuel in around 1,000 RPM and start at around 20 or 30mm3, either via throttle base injection quantity or torque based fuel (depends on which Duramax you have) or through the pulse width tables. This will also generate a little more heat while adding a little more power at the same time. When I say a little I mean like 5-10% increases to start with. And if you lose fuel efficiency then experiment with advancing the timing a little bit to compliment the added fuel.

I'm basing my philosophy on sled pulling trucks...they add fuel and RPM's to get there turbos spooling rather than retarding timing I'd say. But I dunno it's late and I may not be thinking straight as well lol.