Don Terrill’s Speed-Talk

joe 90 wrote: ↑Sun May 20, 2018 4:35 pm

ptuomov wrote: ↑Sun May 20, 2018 9:18 am

joe 90 wrote: ↑Sat May 19, 2018 7:13 am It must be called "lean spool "for a reason?
If you're adding excess fuel it's not lean so therefore lean spool doesn't use excess fuel.

So what’s your answer, does lean or rich spool the best in terms of maximizing acceleration?

As I said above in a previous post, richer than lambda 1 but not as rich as full power rich.
If you flood it with fuel so that it runs dirty , it'll run like crap.

And how about ignition timing?

ptuomov wrote: ↑Sun May 20, 2018 4:47 pm

joe 90 wrote: ↑Sun May 20, 2018 4:35 pm

ptuomov wrote: ↑Sun May 20, 2018 9:18 am

So what’s your answer, does lean or rich spool the best in terms of maximizing acceleration?

As I said above in a previous post, richer than lambda 1 but not as rich as full power rich.
If you flood it with fuel so that it runs dirty , it'll run like crap.

And how about ignition timing?

I've already mentioned that too.
You even quoted my reply.
......................................................................................................
Lean spool?

There's more than one way to do it.


If you run extra rich (11s) when you don't need to , you kill the power output.
So keep it lean, normal lean, in the 12s or 13s......pull back the ignition timing a bit.
You lose a bit of power but the boost goes up quicker.


Everything has a downside, the downside to this sort of thing is failed turbos.

This is a turbo engine 12-13 AFR burns holes in pistons.

vwchuck wrote: ↑Thu Jun 07, 2018 9:43 am This is a turbo engine 12-13 AFR burns holes in pistons.

Even at the rpm band where the turbo is just spooling and wastegate is fully closed under WOT?

By running rich and retarding the timing you are effectively turning the exhaust system into a burn chamber and spinning up the turbo earlier than you could with only the engine. You are spinning up the turbo from the delta P that you created due to burning fuel in the exhaust. This is VERY hard on the turbine......
I think the OP is looking for a safe fix to increase boost when the engine is out of the power band. In this case you really can't unless you go to a sequential turbo setup where you feed a small turbo with a larger one. It is a plumbing and control nightmare but will give you torque down low and make you come on boost much sooner.

ptuomov that isn't the operating condition. He said he is full throttle at low RPM trying to do a pull on the highway. I would definitely run it rich there.

My car has a 5.0L V8, makes peak power at about 6200 rpm, and makes about 2 psi of boost 1400 rpm. So I don’t really have a problem with the car (not this problem anyway). I’m just trying to understand what’s optimal and why.

Oh didn't even realize you are the OP...so this problem doesn't even exist?? Great....

vwchuck wrote: ↑Thu Jun 07, 2018 2:40 pm Oh didn't even realize you are the OP...so this problem doesn't even exist?? Great....

More is never enough and too much is just right!

If I learn something useful in this thread, I'll surely try it out. So it's not wasted effort.

vwchuck wrote: ↑Thu Jun 07, 2018 9:43 amThis is a turbo engine 12-13 AFR burns holes in pistons.

It's a low compression engine and its off-boost. You could probably run 14.7 there if you wanted to.

vwchuck wrote: ↑Thu Jun 07, 2018 9:43 amThis is a turbo engine 12-13 AFR burns holes in pistons.

Only when you do it wrong.

Only a fool would run it there for the irrelevant 10 horsepower gain. Just turn the boost up 1 psi more

The idea is to only run it like that while the turbo (s) spool up (to make boost) which shouldn't take any more than a second or so.

A 12 or 13 to doesn't and never has burned holes in any pistons, not when you're at lowish load and not making boost.

It's the detonation or pre ignition resulting from that lean AFR combined with low octane and the timing wrong which does it.

Old thread, but interesting. Has anyone tried secondary air injection to speed up the spool? Koenigsegg has used pressurized air, which clearly works and is quite involved. I've successfully used air injection with check valve and solenoid increasing exhaust temperature to get a 2-stroke measurably earlier on the pipe and wonder if something similar could be used in 4-stroke turbo application.

Dr. Hans Mezger (of Porsche 911 fame) published an SAE technical paper in 1978 on turbocharging and secondary air injection reducing turbo lag was covered. Porsche found that adding secondary air injection reduced turbo lag. This was one area where a "smog pump" actually improved performance.

Since the goofy belt drive air injection pump was buried on the 930's, driven off of the back of the left side cam, an astute customer could tell that "something was wrong" when the little belt broke. It had noticeably more turbo lag without secondary air injection.