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-   911 / 930 Turbo & Super Charging Forum (http://forums.pelicanparts.com/911-930-turbo-super-charging-forum/)
-   -   Thought on this AFR graph? (http://forums.pelicanparts.com/911-930-turbo-super-charging-forum/401064-thought-afr-graph.html)

RarlyL8 04-19-2008 09:49 PM

I believe that is the same unit I have. It looks like this installed:

http://forums.pelicanparts.com/uploa...1208666935.jpg

Quicksilver77 04-19-2008 10:13 PM

OK I'll pony up! Nothing like the right tool for the job! Plus buying tools makes a guy feel infinitely more manly!

Though in regards to the cold pressure vs. the warm pressure the settings: from BL these were 2.2 cold and 3.75 warm. Is this saying that the fuel pressure should be 2.2bar upon start up and 3.75bar after warm up?
Shouldn't these be reversed? more pressure/fuel at startup? and then leaning out at warm operation? I would tend to think that the higher pressure would push more fuel into the cylinder in a shorter amount of time leading to a rich air fuel mixture.

Or does a higher pressure result in a leaner air fuel mixture by creating a more aerosol-ed fuel spray from the injector, which would explain why BL set the WUR as he did? Not questioning BL in any way shape or form, just trying to understand! :cool:

lite75 04-19-2008 11:42 PM

Fuel pressure and control pressure both need to be checked, the WUR only effects the control pressure. More control pressure less fuel, less control pressure more fuel.

Dan

RarlyL8 04-20-2008 06:33 AM

The spray pattern remains the same nomatter what the pressure. The volume of fuel changes.
The fuel head piston moves farther up the chamber as control pressure rises and allows more fuel to flow. An x-ray style diagram would help you see how that works.
BL likely set your WUR in the middle of spec for your application and region, I am simply suggesting you verify those numbers before moving on.
In order to take full advantage of the Leask modifications you need the pressure gage and an LM-1 or similar device reading A/F ratios that will allow you to fine tune the WUR to your specific application. You can rough tune using only the pressure gage but fine tuning must be done with an LM-1 or similar device.
If you need more info past what BL included with your WUR there are many threads on the subject.

Quicksilver77 06-03-2008 10:45 PM

Update
 
Alright it has been a while, but here is where I am at!

Installed wur and checked the cold pressure with wur unplugged:
Gauge Valve open: 8psi

I pulled the wur and sent 'er back down south for a quick look see from B. Leask
Seems some contamination made its way into the wur and was making it bench test at 4bar.

WUR re-calibrated and sent back.
Installed WUR and checked cold pressure:
Gauge Valve open: 8psi

WTF I say!! I'm not getting enought fuel!

Checked fuel pump relays: Good
Checked fuel pump operation: Both running

A month or so in... I decided to throw in the towel and take her to someone who knows what the eff they are doing. Been at the shop for two days, and the best they can say is that there is something down stream of the WUR that is bleeding the pressure (no sheite). But with the gauge valve closed they are seeing 90ish psi. So at least the pumps are working and the filter is not clogged. I guess?

The car ran before I:
-Pulled the WUR and installed the rebuilt adj. WUR
-Unplugged the Andial fuel enrichment system (shown above, I unplugged the two prong connector shown in the picture and removed the item it plugs into from the fuel line)
-Installed the RPM solenoid valve

What the heck did I do????? That would cause this shop with eons of experience to be in the dark? Any ideas???

The weather is perfect and I want to be driving!!!!

JBL930 06-04-2008 12:51 AM

I'm simply asking this question so i can better understand how you plan to achieve what you are saying, i know you know your stuff so i'm all ears.
A stock WUR starts to enrich the fuel at about 3psi, which is 0.2bar, anyone can see that with a modern turbo fitted this amount of boost comes in really early, even below 2000rpm in some cases! Brian Leask states that the WUR boost threshold can be raised to as much as 8psi, this is 0.55bar. This boost pressure will be reached by around 2500rpm which is still way too early. In all of the applications that i am aware of I am told that boost enrichment needs to be delayed until above 4000rpm, sometimes as late as 4500rpm. By this point full boost has been reached for way over 1000rpm of the rev range, how can adjusting the mechanical boost enrichment threshold inside the WUR delay enrichment in this way? It can't, you can only delay it until a certain boost level and not a certain RPM point, full boost is reached long before it needs enrichment so the only way i can see of getting a flat AFR is with the RPM solenoid, Brian Leask clearly agrees with this.
If i am missing something here please enlighten me, cheers


Quote:

Originally Posted by RarlyL8 (Post 3865230)
No, what I am saying is the RPM switch is a good bandaid but does not actually fix the problem, it masks the symptoms.

The problem is that as the WUR ages it goes off spec. In order to recalibrate you need to go inside the WUR and do some adjusting. Once back in spec you re-gain the full spectrum of the threshold adjustment.
The RPM switch simply delays the onset of boost by hiding the signal until a preset RPM, effectively overriding the threshold system by shifting the threshold to a point requiring less adjustment. The resulting A/F graph looks better but the WUR is still off spec.


JFairman 06-04-2008 05:34 AM

Hey JBL, you're 100% correct :) lol

and, from a post above your's...

"The fuel head piston moves farther up the chamber as control pressure rises and allows more fuel to flow."

Isn't it the other way around....?

Control pressure from the WUR is pushing down on the top of the fuel head piston which when moving downwards covers up more and more of the metering slits in the cylinder wall letting less fuel through to go to the injectors.
The air flow metering plate through it's lever and linkage is pushing up on the fuel head piston from the bottom. So, more airflow then pushes the piston upwards exposing more of the metering slits and letting more fuel go to the injectors.
The position of the fuel head piston is a balance between the force on the bottom of the piston from the air flow meter and the force or fuel pressure on the top of the piston which is being governed by the control pressure regulator or WUR.

The WUR or control pressure regulator is regulating that pressure on the top of the piston by simply bleeding it off and letting return to the fuel tank. The amount it does that is defined by ambient temperature when cold, and then heater element and engine block temperature when warming up, and in a turbo's WUR the boost pressure routed to a diaphram in the bottom of the WUR when the turbo spools up. This one lowers control pressure when you are on boost letting the piston rise because the airflow meter is really pushing up on it now which finally sends more fuel to the injectors.

sand_man 06-06-2008 10:05 AM

Quote:

Originally Posted by JBL930 (Post 3982670)
I'm simply asking this question so i can better understand how you plan to achieve what you are saying, i know you know your stuff so i'm all ears.
A stock WUR starts to enrich the fuel at about 3psi, which is 0.2bar, anyone can see that with a modern turbo fitted this amount of boost comes in really early, even below 2000rpm in some cases! Brian Leask states that the WUR boost threshold can be raised to as much as 8psi, this is 0.55bar. This boost pressure will be reached by around 2500rpm which is still way too early. In all of the applications that i am aware of I am told that boost enrichment needs to be delayed until above 4000rpm, sometimes as late as 4500rpm. By this point full boost has been reached for way over 1000rpm of the rev range, how can adjusting the mechanical boost enrichment threshold inside the WUR delay enrichment in this way? It can't, you can only delay it until a certain boost level and not a certain RPM point, full boost is reached long before it needs enrichment so the only way i can see of getting a flat AFR is with the RPM solenoid, Brian Leask clearly agrees with this.
If i am missing something here please enlighten me, cheers

In my low-brow primitive mind, your description and the one in Brian Leask's manual for the solenoid, is how I understand it. Rather than a "band-aide" (I know this wasn't said with malice), the solenoid, from my perspective, is a timing mechanism; a way to achieve a some what flat fuel curve by delaying the enrichment fuel until it's really needed...obviously that's dependent on the engine in question and what mods are in place. I don't think it has anything to do with the WUR being out of spec.


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