jcorenman

Carry on, not much I can add... definitely need more details.
As noted, closed-loop data will have more scatter due to the LH continuously diddling with the fueling, hunting around the stoichiometric AFR of 14.7 in order to keep the cats happy. SP tries to correct that, if O2-adjust is also logged.

But a lot depends on the time span-- there are lots of data points in the cell that Ralph referenced-- because of the fuel heating that Tuomo mentions. I am also not convinced that intake air-temp is completely compensated by the LH. And it also depends on the type of driving-- ripping through the mountains introduces a lot of variation because of the fast changes and limited sampling rate. Tuning on the road is ideally a wide range of load and RPM, varied smoothly over a relatively short time-span (i.e. an hour, not days).

Ralph Newman

Thanks all for the great information. I feel like I should be sending you a tuition check.

The good news is that the car is running fine right now and with your input probably can be improved.

Jim, nailed one issue. When tuning, I have been driving the car as I normally would around town. Start, accelerate, shift, accelerate, shift. etc. etc, etc. for 30 minutes or so then add additional run on subsequent days. I assumed this would give me a good average A/F ratio. As he suggested, I will try tuning using single hour run, slow the acceleration and deceleration down as much as possible.

Are the fuel dampers there? If the fuel rail driven by the LH doesn't have sufficient fuel damping, that creates resonant slightly angled but mostly vertical "stripes" in the Sharkplotter AFR visualization. It will be impossible to get rid of those errant AFRs within a cell, because the resonance is so sharply determined by (rpm, pulse width). It's a fools errand to try to tune the LH without very well dampened fuel rails.

Ptuomov. I do have the dampers in place. However, recently I noticed my fuel gauge will start out being very steady and later in the run be bouncing quite a bit. About 4-5 psi, plus or minus. Thought it might just be my gauge getting old. So I will check the dampers.

Thanks again, Ralph

FredR

You cannot get high load readings without being on it - that is best achieved in top gear and we all know what happens when you do that!!!! Remember when you stamp on the gas pedal there is a transient correction profile for the lead lag due to acceleration of the airstream that messes things up a tad.

Friend of mine who had a 996 twin turbo some years ago was going abroad on holiday and when clearing immigration at the airport the police officer on duty said to him "I take it you like driving fast sir" to whit my friend responded wryly "Yes sir" - the officer smiled and told him he had a ticket for doing 270 kph [about 170 mph]. The nice officer told him he could pay the fine when he returned! Things are a bit different these days and I doubt that "Sharktuning" would cut the mustard as mitigation. Indeed above a certain speed point I think one gets 3 days in the slammer.

Speedtoys

I had this on 60lb injectors that were too much for the stock dampers...ill try to find that thread.

..This?

https://rennlist.com/forums/928-foru...l#post10012537

ptuomov

This setup with two 951 fuel dampers works for me with 80+ lbs/hr injectors:

Instagram

View this post on Instagram

www.instagram.com/ptuomov