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i just realized that that the crankcase vent connects to both inlet plenums as well through the small diameter balance pipe (or whatever it’s called...) How does this work ? Is there a check valve in the connector to the air box ?
The pigs snout at the front end of B bank connects to the end of the B bank airbox via a quite large diameter pipe and flexibles. The air then goes at 90 degrees through the airbox to the pipe you mention, via a sprung one way valve in the short flexible between the airbox and the thin pipes. There is a bit inside the airbox that also lets crankcase air into the airbox itself and thus through the B bank inlet butterfly at wider throttle openings.
I only suggested blocking off the inlet pipe from the pigs snout as it is a theoretical source of air.
Rear air balance tube removed and replaced by a 3/8” hose with a T for ECU.
Engine started. RH bank understandably run pretty rich and fills garage with fumes. I disconnect the hose and allows it to breathe durin warm up.
Vacuum is appr 0.5 bar on both banks after the AAV has closed. Idling at 400-450 RPM. Remember idle shunt at AAV is fully closed as well. There is actually no flow through the AAV when warm.
I then disconnects PCV tube and blocks the connectors to air plenums. Idle drops to 400 RPM, and RH vacuum increases to 0,7 bar (21” hg).LH vacuum is 0.4 bar (12.5” hg).
I measure the vacuum at the middle of the rear balance hose, which is split during this measurement, ie no connection between the 2 banks air plenums
It seems the air supply for idle mainly is from PCV and maybe AAV. I had expected to hear leaks from inlet manifold gaskets or o-rings when abusing the engine like this, but it just turns over nice and slowly...
Ok, a finger pushing on both butterflies did eventually kill it.
I suppose that means I may have a PCV valve with too little resistance against opening, maybe slightly too much throttle gap and otherwise a quite sound inlet/vacuum system.
Now I will reassemble and go for a blast. I bet the exhaust is half filled with water and fuel...
Leo
Block off the PCV pipes at the point the single pipe exits the flexible with the valve in it (ie after the back of the airbox). Then you van remove the flexible and the valve inside it, clean them up and see what the spring in the valve is like. You may, repeat may, have a leak in the flexibles/joints between the pig's snout and this point.
The PCV should not be a source of air, except to the extent there is either an airway into the block (eg the chain tensioner plug is missing) or as a result of blowby past the piston rings. With the PCV pipe blocked off, adjust the AAV. Then renew all the PCV flexibles and that should sort out the tickover. On my car, if the PCV is blocked, there is no change to the tickover.
Cheers
Greg
My PCV opens at a pressure well below the start of scale on my vacuum tester. My guess is 0.03-0.05 bar, so it seems to be dead.
The spring is in place and ensures one way flow, it's just extremely soft.
I did by the way have a nice joyride. I could still make it miss at ultra light throttle. I tried to change into in neutral without lifting off the gas to get an idea of just how light throttle we are talking about.
17-1800 RPM was the result. It would be interesting to know somebodys TPS voltage output when keeping RPM at this level. Just for reference and something I could try to adjust after in case my pushrods are having too much (or too little) slack.
I opened the PCV valve by removing the flanged lip in a lathe. The spring was intact, so I increased the spring pre tension by placing a spacer under it. M8 nut fitted very well...
This caused idle to drop to around 550 in N/P and 450 in drive.
RPM has since the A/C was repaired been rising 100-150 RPM when A/C kicks in. I have therefore made a small bushing to reduce flow in the supplementary air solenoid valve opening for extra air when A/C kicks in to avoid RPM to drop. The inlet hole in the valve is 6.35mm, and I started out with a 3 mm hole, which should reduce the flow to around 25%. This turned out to be fine, I now have an increase of 10-20 RPM when A/C turns on. The devil is in the detail
I then opened idle screw at AAV maybe one turn, and I do now have idle in N 700-750 RPM both with and w/o A/C. In drive it's around 600.
And how how about the missing ? No issues, but it’s as cold as in my fridge, so I will not conclude it’s gone yet...
SAV with nozzle for reduced flow SAV in place
Last edited by leo_denmark; 10-27-2018 at 10:22 AM.
Reason: typos
10-14-2018, 01:54 PM
