AFR's go Down as RPM's go Up?

[mooney265]

I have been fighting an overly rich [boost] condition with my CIS. I have a BL WUR with 4800 RPM Pill installed. And, all 6 injectors replaced about 1-yr ago...

I've got the CIS test gauge and use it regularly. And, always log my changes. In looking at the history, I see the following: [WP=Warm Pressure and EP=Enrichment Pressure]

WP: 3.75
EP: 2.1 - [1.65 BAR difference] the way it was shipped from Brian Leaske on 4/09 - so rich it "bucked the car under boost..."

WP: 3.8
EP: 2.5 - [1.3 BAR difference] 9/18/09

WP: 3.85
EP: 2.9 - [0.95 BAR differnce] 11/4/09

WP: 3.85
EP: 3.1 - [0.75 BAR difference] 2/6/10

WP: 3.85
EP: 3.2 - [0.65 BAR difference] 4/10/10

WP: 3.9
EP: 3.3 - [0.60 BAR difference] 5/20/10

WP: 4.1
EP: 3.55 - [0.55 BAR difference] 9/21/10 - Today

After doing today's adjustment, I took it for a spin. I noticed that my AFR's have increased from 13.8 to 14.1 at 1500rpm cruise - as expected...

BUT, as i increase the RPM, the afr's slowly and steadily drop to about 13.0 at 4500rpm [and NO BOOST]. This means, I only need about a 1.5 AFR drop at the onset of boost when the 4800 pill hits...

My question is: Is this constant AFR drop normal as RPM' increase and no boost with CIS?

And, Could my mechanic have put a larger flow injector in?

What could be causing this situation where fuel is increasing greater than the air as RPM's increase under a NO-BOOST situation?

A fuel head mod that I'm unaware of?

Thanks CIS brain-trust!!

[tj930]

I've been wondering about Boost Pressure and RPM myself.

I've been logging the voltage across the Boost Sender with my LM2. I can be cruising at 2000RPM in 4th gear with 0.0Bar registering on the Boost gauge, but this voltage is (if memory serves me correctly) around 0.05V higher than when the car was warmed up at idle (at the start of the journey).

The thought is that maybe there is some small boost level and some correspondingly small voltage as a result, even though this is not enough to lift the needle in the OEM gauge?

[mark houghton]

I've been seeing something similar this summer, though even more pronounced, but only after I've shut down for a few minutes after the engine has reached full operating temperature (like after a half hour highway cruise). Stop at the store on the way home, fire her back up, all runs fine, AFR's normal at idle, then put some rpms on her under load (no boost) and watch the AFR's drop down as low as 12.0 by 4000 rpms (and even if there was boost, I've got a 4800 pill and solenoid to delay the boost pressure charge to the WUR).
Something to do with heat soak....maybe....but I doubt it. Loosing power to the heating element in the WUR and mimicing cold start enrichment....maybe? I haven't spent much more than brain time on this one. Could be my BL WUR is going south.

[tj930]

P.s. I've got the throttle sticking open slightly - and I'm blaming the stock WUR for this!

[mooney265]

Originally Posted by mark houghton

I've been seeing something similar this summer, though even more pronounced, but only after I've shut down for a few minutes after the engine has reached full operating temperature (like after a half hour highway cruise). Stop at the store on the way home, fire her back up, all runs fine, AFR's normal at idle, then put some rpms on her under load (no boost) and watch the AFR's drop down as low as 12.0 by 4000 rpms.
Something to do with heat soak....maybe....but I doubt it. Loosing power to the heating element in the WUR and mimicing cold start enrichment....maybe? I haven't spent much more than brain time on this one. Could be my BL WUR is going south.

Mark,

Thanks, but I don't think I'm losing power to the WUR... I keep the gauges on the car and run it... don't see any change in the CP...

The heat soak thing could be real, however, it's happening when barely warm, too...

[mooney265]

Originally Posted by tj930

I've been wondering about Boost Pressure and RPM myself.

I've been logging the voltage across the Boost Sender with my LM2. I can be cruising at 2000RPM in 4th gear with 0.0Bar registering on the Boost gauge, but this voltage is (if memory serves me correctly) around 0.05V higher than when the car was warmed up at idle (at the start of the journey).

The thought is that maybe there is some small boost level and some correspondingly small voltage as a result, even though this is not enough to lift the needle in the OEM gauge?

but, I have the RPM switch to "delay" boost enrichment... don't think I'm beginning to "enrich" until 4800 rpm...

[mooney265]

Any other ideas? Thanks, Shannon

[mark houghton]

Originally Posted by mooney265

Mark,

Thanks, but I don't think I'm losing power to the WUR... I keep the gauges on the car and run it... don't see any change in the CP...

The heat soak thing could be real, however, it's happening when barely warm, too...

Your gauges are installed inside the car, so you can watch it under load? That's interesting. Or are you referring to just sitting in the driveway?

If your CP isn't changing then the low AFR's are most likely not fuel delivery related. Possibility of a small air leak after the turbo and before the throttle body...loosing some of the air that should be going into the engine. It can be kindof misleading, these turbo cars, in that air leaks react almost directly opposite of a NA car. Even though you're not showing any boost, the intercooler and associated plumbing is under some pressure, and a bad seal will leak out...not draw in as one might expect. With your air to fuel ratio already set by the deflection of the control arm at the fuel head, if all that "metered" air doesn't make it to the engine, you'll be too rich.

Just a thought.

[mooney265]

Well, I didn't think of that... I figured if I had a leak down there that I would be more "lean" due to the vacuum...

And, yes I'm operating engine with gauges hooked up in the driveway...

[Helmsy]

OK I am having a similar situation where I am too rich under boost even if I adjust my BLWUR to not enrich under boost. I don't have the solenoid but have tested with my mityvac to see enrichment not occurring at 12psi but yet a drive with boost sends my afrs into the 9s.

If I plug and/or remove the boost line to the WUR (for testing) should I see no enrichment on boost or is there some other way the car goes rich under boost?

[Helmsy]

I managed to get afrs into the high 10s by banging the disc in but am hesitant to hammer it in anymore (looks like it's a fair way in).

Does increasing system pressure affect the boost pressure too? I did try raising system pressure to spec but found it caused run-on on shutdown so returned it to where it was.

What else makes an overly rich boost enrichment? Timing looks like its working fine. I am happy to live with mid to high 10s on max boost but I am only running 0.8bar boost and max increase to 1 bar in the future. Any ideas?

[xbmwguy]

shannon have you checked to make sure the solenoid you are using is actually staying closed completely until 4800?

[pkracer21j]

These cars are supposed to run-on after shutdown for a couple seconds.

[pkracer21j]

BTW, seek xbmwguy's knowledge...hes a CIS BL WUR guru. he coaxed 10hp out of my car on the dyno!

[mark houghton]

Originally Posted by pkracer21j

These cars are supposed to run-on after shutdown for a couple seconds.

Be carefull on our use of words. Yes, the CIS 930's have a "delayed ignition cutoff" when you turn off the key (fuel pumps shut down but the ignition continues to fire for a couple seconds to burn residual fuel). Not to be confused with engine running-on (as in dieseling) which Helmsy might have been referring to.

[Helmsy]

Thanks Mark.

Yes I was referring to the actual run-on ('dieseling') which the engines keeps put putting after the ignition has shut off.

I need to have my system pressure below what is in the books in order to stop this from happening.

In the case of my boost enrichment I believe I probably need the solenoid but am happy to leave it where it is for now.

I was just wondering why if I adjust my WUR to have no effect under pressure with my mityvac that I still see enrichment?

[mark houghton]

Originally Posted by Helmsy

Thanks Mark.

Yes I was referring to the actual run-on ('dieseling') which the engines keeps put putting after the ignition has shut off.

I need to have my system pressure below what is in the books in order to stop this from happening.

In the case of my boost enrichment I believe I probably need the solenoid but am happy to leave it where it is for now.

I was just wondering why if I adjust my WUR to have no effect under pressure with my mityvac that I still see enrichment?

Do you still have your stock WUR? Might want to swap out the BLeask with the old one, just to take that out of the equation.

[mooney265]

Originally Posted by mark houghton

Do you still have your stock WUR? Might want to swap out the BLeask with the old one, just to take that out of the equation.

Mark, usually Brian takes the original one... He did mine...

And, like Ben is asking, I'd like to know why my AFR's are dropping without the boost enrichment even taking place?

I haven't gotten as far as "tuning out the enrichment" but, have lowered it to just a couple 1/10's of a BAR and it still goes too rich [9's] in the upper RPM's????

[mark houghton]

Originally Posted by mooney265

Mark, usually Brian takes the original one... He did mine...

And, like Ben is asking, I'd like to know why my AFR's are dropping without the boost enrichment even taking place?

I haven't gotten as far as "tuning out the enrichment" but, have lowered it to just a couple 1/10's of a BAR and it still goes too rich [9's] in the upper RPM's????

That's right, I forgot (I bought my BLWUR from someone else but direct from Brian set up to my mods, so I still have my stock unit).

Wish I could give the answer to your and Ben's issue. Let's think what can cause swings in normally stable mixtures: Faulty WUR (well DUH!), air leaks in the intake of CIS engines would cause a rich condition under any level of boost - getting progressively worse with more boost (even at your stated "no boost 4500", there is still low boost there), changes in system pressure dropping unexpectedly (pressure regulator spring assembly in the fuel head or one of the fuel pumps operating erradically), fuel injector sticking open or poorly atomizing the fuel, faulty portions of the lambda control system (O2 sensor, frequency valve, or computer under the seat), maybe even changes in the ignition timing advance curve for some faulty distributor reason, etc etc.

Sorry for the random mind dump on this; nothing concrete I know. Whatever this is, it seems to happen to a small percentage of us. Unfortunately I'm not a CIS systems expert but there are such people lurking in the background watching as we stumble along.

[911st]

CIS is a lot of fun but has not ability to compensate other than via the Lambda computer / function. On the ignition side, only the C2 turbo's have any real compensation for differance in intake temps.

---Thus, on a hot day when there is less oxygen in the air CIS is going to keep delivering the same fuel and the AFR's are going to go rich. Cold day and it will go lean. (Same fuel, more or less oxegen.)


---As to monitoring boost pressure voltage, the sender needs to be after the throttle plate to get any usable information for part throttle operation.

--- As to rasing system pressure. It should not effect AFR's at normal operating ranges. It should only extend the upper end fueling delivery. CIS operates at 100% duty cycle and is alwas delivering fuel. The orfice at the injector is a fixed size. Thus the only way to vary fuel delivery is to change the pressure in the injector line. At low speed pressure to the injectors is low. As we start reaching peak HP the pressure to the injectors will approach system pressure. Extend the system pressure and if the fuel pump can maitain it at peak HP, it should help up top. Might look at the accumulator and or a leaking injector for the change in run on with higher system pressure. However, on shut down the fuel dist probably leaks down to the pop pressure of the injectors. More pressuer, more leak down.

--As to trying to tune the AFR's with the WUR:

AFR at idle can be adjusted at the factory adjustment screw. However, to a degree it will affect the metering pint position at all air flow levels and about the same amount. That is, if we add 1 point to the AFR to a 1000rpm idle. It will probably add about .5 point to a 2000rpm idle.

Base CP effects the rate the metering pin advances as a percentage. Thus, if we lower it so that AFR's at idle might go up 1 point or 7%, AFR at high speed cruse will go up about 7% more or less.

Same thing with on boost enrichment. However, what complicates things is the metering cone and plate on the 3.3 turbo's were not designed to work much past the air flow rant of 300 HP. Thus, a bit past 300hp the metering plate starts to stall and the metering pin no longer advances.

Thus, the more we lower on boost CP the fatter our on boost AFR's will get. Then as the metering plate starts to lose its fidelity at higher air flow, the AFR's will start to taper off.

Got to run.