AFR tuning and intro

[patina]

Alan what CP are you running? I would agree 3.0 seems low, but I saw virtually no real change in cruise AFR’s dropping WP from 4.0 to about 3.6. Even at 3.6 my cruise AFR was mid to high 15’s. I aim for stoichiometric (14.7) cruise AFR. At 3.0 I was dead on the money yesterday. It was also a 50* ambient day so I’m sure that will fatten a bit as the days get warmer.

[patina]

Just did a flow test to confirm fuel and it exceeded 1500cc’s in 30 seconds so all good there.

[Alan L]

I am generally running between 3.6-3.8
I don't have a cruise AFR (track only). But what I am trying to say is setting your WP to satisfy an AFR cruise number is the wrong approach. You are basically on boost dump WP.
It is possible your idle mix may help at cruise AFR - depending how the car idles and where that AFR sits currently. At low throttle openings the idle mix has some input in to the AFR.
Alan

[Alan L]

Being able to check for airleaks, and CIS settings, you are 99% there in terms of what you need to sort these engines out. Those bits of gear will serve you well and save you lots of time and $s in the future.
You are on the right track.
I will post a reference to a CIS book when I get home - maybe today. Explains how all the bits work - including the fuel distributor etc. Once you have that knowledge it gets easier to diagnose problem areas. But for right now you need to know you have not induced an airleak (there are lots of hoses associated with getting to the recirc valve ), and for reference check the WUR settings. No need to alter anything there right now - but check you are close to spec. That then gives you baseline info for air and fuel. The answer has to be in there somewhere.
Alan

[patina]

So I checked Cold Pressure today and somehow it dropped big time from when I set it yesterday. I set it back to 2.1 and set WP to 3.4 with idle AFR at 13.0. It’s been raining all day today but I should be able to take the car for a drive tomorrow to see where I’m at. Should be 60*F ambient.

[Alan L]

I always have a thermometer next to the WUR when setting CP.
A 10 Deg F drop will have a noticeable effect on CP. So even the time of day you set it at can make a difference. There is a Temp/CP chart for the WUR. I will see if I can dredge it up from my manuals etc.
But basically you need to know the ambient temp when setting CP.
Alan

[Alan L]

I can't seem to post the graph.
But for 5 Deg C increase, you get 0.3 bar increase in CP. Or vice versa for temp drop.
Are you knocking the pin to reset CP? You don't want to do that too many times.
Since you are in the lower temp range at 60 DegF, at 10 Deg C CP should be around 1.6 bar, 15 Deg C= 1.85 +/- 0.1
Alan

[930martini]

Finally I got all the necessary parts and I found the time to install an RPM switch. I use my Zeitronix ZT-2 to control the activation of the valve and I can set the boost dump threshold from the Zeitronix software.
I set the threshold to 4000RPM first and increased it up to 4800RPM. I have attached a screen shot from my last run. I think it leans out a little to much (12.6 AFR) at around 6100RPM. What do you think??

[patina]

Originally Posted by 930martini

Finally I got all the necessary parts and I found the time to install an RPM switch. I use my Zeitronix ZT-2 to control the activation of the valve and I can set the boost dump threshold from the Zeitronix software.
I set the threshold to 4000RPM first and increased it up to 4800RPM. I have attached a screen shot from my last run. I think it leans out a little to much (12.6 AFR) at around 6100RPM. What do you think??

You are dipping below 11.0 at boost onset? That is not ideal. 12.6 at close to redline is not bad.

[930martini]

I agree that the dip at 4800 RPM when the switch opens is too low. I will set the RPM threshold at 5200 and see if the low dip can be avoided....