boost lag and fuel economy question

[newsh]

Good news on the compression test

Only time I feel something is off is when I'm requesting full boost..

Describe what happens when you request full boost.

[hunker7]

Going over Dave's G39 links I've realised why lambda seemed not to be working. Because I thought lambda plug is the one with 2 pins, and heater is the round one, so I was unplugging that, thus is wasn't running differently.

So nothing has really changed (glad I got lambda quite cheap) so I'm still where I was before whole lambda thing.

I will call Automark and see what he says, as Spink hasn't got back to me.

[hunker7]

When I request full boost (i.e. fully press throttle) nothing happens for good second or two at about 2000 rpm in 3rd gear, of course it's less noticeable in lower gears and higher revs.

Was doing about 75mph on my way to brother's and I floored it in 6th (3000rpm) it still has a lag (unlike when I was coming back from you) and then it boosts and goes but occasionally I can feel car shake slightly or being slightly sluggish.

It's hard to explain.

[hunker7]

Just unplugged lambda (for real this time) and feels like boost builds up quicker?

Still doesn't pull properly at higher speed/revs but hats expected I guess?

[Error404]

It will run rich with lambda disconnected the ECU will use default safe values. I would image it will also pull timing to be safe.

[hunker7]

I mean fuel consumption dropped right down. But first/second gear it felt nippier.

[newsh]

Lambda is ignored at WOT anyway.

Do a boost leak test. Properly with an air line.

When are you back down South? How about ADI?

[Error404]

Well, if fuel consumption dropped I think you can assume lambda is probably working ok. Lambda isn't used on full throttle

[hunker7]

Don't have access to air line. Not planning to go south any time soon.

[hunker7]

What I will try to do is undo downpipe bolts (where it attaches to cats) to have a gap and then go for loud test drive and see if that helps.

[newsh]

If you have a "boost" leak then the ECU will try to adapt as you go from off-boost (cruise = vacuum so drawing in unmetered air) To on-boost (boost = pressure so metered air escaping) This means you get a stumble as you go from cruise to boost before it adapts.

If you disconnect the Lambda it cant adapt so no stumble, just rich all the time

That's the theory, of course you have to do the boost leak test to find out if you have a leak. It will be a small one, if it was a big one you'd get a code or an "overboost" fuel cut!

[hunker7]

I'll hook up my spare tyre and boost test, I've ordered MAF hose too should arrive next week at some point.

[newsh]

If you have a leak in the MAF hose of PCV then you will be just drawing in unmetered air and the ECU will only be trying to add fuel to combat a lean situation, the amount of adaption will still change depending on how big the leak and how much throttle.

[newsh]

I had a hole in my MAF hose when I first got my 3B, it had rubbed through on the back of the headlight shroud. It wasn't running right.. I also had a leak in the N75.

[hunker7]

How would you check N75 for leaks?

While I wait for MAF hose I will go over PCV system and check the valves and piping again.