Car running lean

[Rusty]

it's 2.2 bar (absolute) at WG crack, then drops away to about 1.6 bar @ redline so is fine

Just checked my stock graph and it was about 10.5:1 all the way from boost onset.

[prj]

Just checked my stock graph and it was about 10.5:1 all the way from boost onset.

That means you had a heavy boost leak.

[Rusty]

That means you had a heavy boost leak.

...my stock car RR graph is with a boost leak created when the operator connected up their boost measuring pipe ...

Yes, as I said, it had a boost leak at the time, the overboost protection cut in on the dyno, it had been fine for an age before that - typical. I traced the problem to the pipe that had been used to T in the dyno boost measurement hose. Didn't do it again after that.

[prj]

Well, AFR's with a boost leak are not terribly useful either
I got 10.7 under boost as well after the hose going into IC developed a split...

[Rusty]

that was my point, hence posting the homefries graph in the first place but that wasn't mcuh help either. Good luck finding a standard one - I'm just askign a mate to see if he can help but it's a long shot.

[prj]

Actually, looking at the homefried log, I have to question a few things...
It runs 12.7 at peak torque, yet gets progressively richer up top.

The highest threat from detonation IS at peak torque... So peak torque should be richer and the top end just after that can be leaned out a bit...

[Billman]

In theory but actually the backpressure rises and you need the cooling effect there and that's why it gets richer.

[prj]

True, but no point going to 11.0 AFR... better to reduce boost.

[Billman]

Less boost there means less power, less AFR there higher boost means more power but more consumption.....one must choose!

[prj]

Less boost there means less power, less AFR there higher boost means more power but more consumption.....one must choose!

Sorry, but this is wrong.
You do not make more power by upping boost and going too rich. At 11 AFR you are severely limiting power already... dipping to 10's is useless, you will not make more power, even with more boost.
Also, talking about consumption at WOT is useless. Consumption is important in transients and on cruise, not at WOT, because the car spends VERY little time at WOT.

[porkkis]

Why don't you just swap to std sw and go for a spin? It's pretty rich at high loads.

As a rule of thumb, all richer than afr 11,5 wastes power and is basically useless. Any situation that requires so much fuel should be avoided.

[prj]

I have swapped to std sw.
It runs around 12.6-12.9 for me at peak torque. Well, basically the graph is similar to homefry, except it does not go mega rich in the end.

I think there is nothing wrong with my car anymore. I ran really lean, because my breather pipes were not sealed tight and were leaking in unmetered air. Since that is fixed and all leaks are fixed, AFR's are much more solid and repeatable.

[Billman]

Also, talking about consumption at WOT is useless. Consumption is important in transients and on cruise, not at WOT, because the car spends VERY little time at WOT.

You obviously never lived in Germany.... :-)

As for the under 11.5 AFR speak to some guys with high powered cars with high boost and then you will see. Also in other car makes it is very common to run richer than 11.5 in full boost (i.e. Subaru).

[prj]

You obviously never lived in Germany.... :-)

Well, if you are going WOT at autobahn, then you should run rich enough, so that EGT does not kill the engine. Consumption is not important.

As for the under 11.5 AFR speak to some guys with high powered cars with high boost and then you will see. Also in other car makes it is very common to run richer than 11.5 in full boost (i.e. Subaru).

Look, you progressively combat knock with fuel.
You up the boost and richen the AFR to combat knock and measure torque.
But richer than about 11.1 AFR torque starts decreasing very fast. So there is no point to use more boost and go richer, you will not make more power because combustion efficiency decreases rapidly as the flame front speed decreases.

This is really the basics of tuning AFR, as is written in any book...
Some random guys who do not know theory and think boost = power do not change the laws of physics.
I personally agree with porkkis, that running richer than 11.5 is just stupid on these cars. If you are still knocking at 11.5, then dial back the boost and increase timing, and you will make more torque.

P.S. Feel free to try it on your car. Just try AFR at 11.5 and then at 10.7. Even with your butt dyno you will feel that the car has lost a lot of power.
That said, I personally try to tune to about 12:0 at peak cylinder pressure in cold weather. That way I have some reserve, so in hotter weather I can go slightly richer, down to 11.6-11.8 using a IAT correction table.

[Billman]

no question you will loose power if you do this, but raise the boost for 0.5 bar and richen up and tell me if you loose or gained power.