JackoliciousLegs

Hey everyone, I posted a while back about getting a/f readings from a NB02 that seemed lean. Everyone told me that I was probly running rich so not to worry. The mods that I have done performance wise are RB Turbo Back exhaust and I bypassed the stock boost controller (now it's 5.5psi) til I can get my creeping under control (creeps to 7-8psi now).

Either way, today I decided to dyno my car with a wideband to get a baseline and see what kind of A/F I was really running. At idle it's at 20:1 and full load between 4k and 7k it was running a WHOPPING 13.8-14.3.

Basically, what is the easiest, cheapest way to get my A/F back to where it should be?

I baselined my S5 at 140rwhp peaking at a little under 7psi. Problem was my ebrake was still partly on. I really don't care about the power right now. I'll dyno it again and when I get the A/F sorted I'll make sure my ebrake is off....

JackoliciousLegs

oh, and what could be wrong....?
PS. It ran the same A/F before the turbo back...

minnesotamike

way to lean fuel filter maybe a new pumps in order or maybe an after market pressure regulator the injectors should be fine but don't cross it off your list yet

JackoliciousLegs

fuel filter has 5k on it.

ilike2eatricers

clean and flow test the injectors? That's pretty cheap and effective. Should be done as maintenance anyway.

minnesotamike

pump injectors and get yourself a nice new sxpressure regulator

JackoliciousLegs

remember... cheapest....

ilike2eatricers

I think upgrading to a adjustable FPR would just cover up the real problem.

hondahater

iTrader: (2)

fuel pump rewire

NZConvertible

That's the wrong attitude to have if your turbo'd rotary is running lean. Don't look for the cheapest and easiest way, look for the right way.

You need to do a little troubleshooting. Measure both the fuel pump voltage and fuel rail pressure under load. At 8psi boost fuel pressure should be ~45psi.

White_FC

Are you taking this reading after all the stock Cats?

even if you are it's still way too lean and needs attention, but just curious.

I'm suprised your engine hasn't blown/been bucking real bad yet?!

Is it flat like that across the whole rev range? or does it change?

White_FC

Opps just re-read your first post.

Sounds definatly like a seconday injector problem of some sort if it's only between 4k and 7k...

What are the AFR's like below that ? (<4k)

Check the plugs on the seconday injectors, i had huge probs with them.

NZConvertible

Oops, I missed that bit too. Check the secondary injector plugs to see if they're secure.

JackoliciousLegs

at idle, it's 20:1, drops slowly, then it steadies at around 14:1 above 4k. Lean all the way across i guess.

so.. check voltages and pressures
check injectors

JackoliciousLegs

Ok, got some voltage readings:
Battery... car off: 12.6v

from my fuel pump:
At idle: 9.3v
with brake lights on 9.0v
lights, radio, brakes 8.0v
WOT no lights: 12.25v
WOT with lights + radio: 12.0v

What's next?

JackoliciousLegs

This is the dyno graph with A/F. Don't mind the power rating. My rear right brake was locked.
Dyno Graph

HAILERS

This probably won't help much..........but, by gosh, my car won't even idle at afr of 15afr or higher figures. My idle being about 750. And if I lean my car out on the low settings and cruise at a afr of 16-17 the car will jerk about trying to hold a steady speed. Those are my impressions anyway. I never even tried to lean out to 20afr before and can't imagine a engine even running with those figures.

Like I said, probably won't help you.....just my impressions. So what is your idle speed?

JackoliciousLegs

750... idles smooth as a babie's bottom

HAILERS

I retract part of what I said. I drove to work and sat in the parking lot. I turned the SAFC down to a minus 50 and the engine did idle at a afr of 20. Sort of flopped around in the engine bay though while idling. No where near a smooth idle.

JackoliciousLegs

Anyone else? What do I do?

HAILERS

Do you have a airpump and acv on the car?

JackoliciousLegs

I do indeed. Only mods are full exhuast, FCD, bypassed electronic boost controller.

I haven't touched the ACV or the airpump... The ACV isn't the thing that connects to the cat, right ? That got blocked by the Racing Beat exhaust....

NZConvertible

Most of the air from the secondary air injection system goes directly to the exhaust ports, not the split air pipe.

HAILERS

Mystery sollved. The acv delivers air to the EXAUST PORTS which are prior to the 02 sensor.

The trubii acv is a bit different than the acv on non tubos that I've described on other posts/thread.

What you want to do is fully warm the engine up. Then, while watching your wideband, reach down to the acv and pull the hose off that sticks STRAIGHT UP. When you pull it off you'll see that hose has a vacuum on it. Plug that with your finger. Now look at the wideband. It should have dropped the afr down to the 13afr give or take.

Give it a try. I just did this on my turboii. I swapped out the best acv I have and put it on the car. The afr read in the 16 to 17 afr with the hose described above connected. When I pull it off, the afr goes to the 13afr range.

Another tack you might take just for grins, is to get a long piece of vac hose and connect it to the very bottom nipple on the acv. Then while the engine is running, BLOW into that vacuum hose. That will open the dump on the acv and make the air go overboard to the silencer in the fender instead of the exaust ports and the afr will drop like a rock to the 13afr.

Just to cover my *** over posts I've made on acv's in the past........the turboii and the non turbo acv work differently. On a non turbo if you pull the BLUE connector off the Relief solenoid the air dumps overboard. On a turboii this does not happen ....unless you rev the engine over approx 1400 rpm or so, then it will cause the relief diaphram to open and dump the air into the fender and the afr will drop.

HAILERS

I see NZ snuck in there while was writing.

AS a side note. I noticed the afr's will vary depending on how good the airpump is and the condition of the switching valve diaphram in the acv. I tried a couple of acv and it took different vacuums to operate one verses the other. Age makes the diaphram harden and harder to move.

Also the airpumps condition makes a difference. In the past I've only seen afr in the 14's range on this car. With the best acv I have I can see the 16's and 17's afr with everything connected up.

When you pull the hose off that sticks straight up, you disable the switching diaphram in the acv and close the passage to the exaust ports. The air does not dump overboard, but then goes straight to the split air pipe. That is why your afr's should drop to the 13's afr when you pull that hose off.

If you blow hard into the very bottom nipple on the acv, you push the Relief diaphram off its base and allow the air to dump overboard and not go to the exaust ports. And then your afrs should go to the 13's afr.

In fact, I'm betting your afr's go to the low to mid 12afr.

There's a functional diagram of the turboii acv in the factory service manual and you can look at it to figure where the air from the airpump goes at different times.

Again, a Turboii acv works different than a non turbo acv. Tactics that work on a non turbo don't work on a turbo and vice versa.