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Airflow meter plate moves with FP

i am currently having issues tuning my fuel system with the adjustable WUR.
My issue is the AFR goes rich when the engine is revved. The fuel pressure can be seen fluctuating and the metering plate fluctuates.When the metering plate is steadied the AFR's return to normal (13.6) with fuel pressure normal. I am trying to identify what is causing this problem.

I have been through the obvious checks, Fuel pumps and WUR settings with no findings apart from the height of the Airflow metering plate.
When no fuel pressure is applied the plate sits just above the top of the cone. When fuel pumps are energised the plate raises by about 5mm.
I have tapped the spring stop roll pin down to slightly to lower the metering plate but it still sits to high.
The manual mentions that the height of the plate should be set with the pumps on, Should the plate normally move up with fuel pressure? My concern is that if i do adjust it with fuel pressure on then it may sit too low when fuel pressure drops off.

Can anyone advise if the plate should move up with fuel pressure on?
Has anyone noticed with fuel pressure off if the metering plate sits below the cone and then raises with fuel pressure on.

Thank you

TIM

Old 05-10-2013, 11:56 AM
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Crotchety Old Bastard
 
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Yes the metering plate will move up when the pumps are on (fuel pressure present). The plate should be adjusted flush with the begining of the cone with the pumps on. DO NOT OVER ADJUST. The stop spring guidepin is pressed in per factory spec and not meant to be actively adjustable. Something has cause the plate height to go out of spec which should be identified as it will likely continue to degrade.
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RarlyL8 Motorsports / M&K Exhaust - 911/930 Exhaust Systems, Turbos, TiAL, CIS Mods/Rebuilds
'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
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Old 05-11-2013, 08:35 AM
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With the engine switched off the metering plate is slightly high, with fuel pumps on it is too high. After engine shut down the plate is too high.
I have re fitted the original WUR and the AFR' are not richening as much just down to 13.4. If I keep a steady throttle the AFR's return to cruise settings about 14.6.
When the fuel pressure fluctuates the Metering plate can be felt vibrating.
As the plate is 5mm above the cone should I adjust it down to flush?

Thanks
Tim
Old 05-11-2013, 11:59 AM
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Had a problem with my metering plate vibrating ... Read my post in this thread.

Air flow sensor vibrates
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1986 930 - K27-7200, Andial Intercooler, Tial Wastegate, Electronic Boost Controller, B&B headers, Bodart Zork, Leask Adjustable WUR, Full Elephant Racing Suspension w/Adustable Spring Plates and Von Shocks, Wevo Transmission Mounts, Fuel Safe Fuel Cell, Forgelines (9"/11"), Hargett Shifter, Innovate AFR, Cobra CF Seats, DAS Rollbar, Coleman Floating Rotors, Lightweight Interior, Forgeline 17" x 9"/11", 2800 lbs.
Old 05-11-2013, 04:09 PM
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Thanks for the link. It does appear I could have damping issue in the fuel head.
Brian has also inferred this as well.
If this is also vibrating when I am on boost then this could explain why I can't lean it off.
Cheers

Tim


Quote:
Originally Posted by Dave 86 930 Fl View Post
Had a problem with my metering plate vibrating ... Read my post in this thread.

Air flow sensor vibrates
Old 05-11-2013, 11:33 PM
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Quote:
Originally Posted by timspu View Post
Thanks for the link. It does appear I could have damping issue in the fuel head.
Brian has also inferred this as well.
If this is also vibrating when I am on boost then this could explain why I can't lean it off.
Cheers

Tim
Not sure about vibrating while on boost, hard to verify ... I don't worry too much about perfecting AFR under boost, as long as its rich.
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1986 930 - K27-7200, Andial Intercooler, Tial Wastegate, Electronic Boost Controller, B&B headers, Bodart Zork, Leask Adjustable WUR, Full Elephant Racing Suspension w/Adustable Spring Plates and Von Shocks, Wevo Transmission Mounts, Fuel Safe Fuel Cell, Forgelines (9"/11"), Hargett Shifter, Innovate AFR, Cobra CF Seats, DAS Rollbar, Coleman Floating Rotors, Lightweight Interior, Forgeline 17" x 9"/11", 2800 lbs.
Old 05-12-2013, 02:09 AM
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Quote:
Originally Posted by Dave 86 930 Fl View Post
Not sure about vibrating while on boost, hard to verify ... I don't worry too much about perfecting AFR under boost, as long as its rich.
With the standard WUR fitted I am seeing high 9 AFR's which is way too rich.
Hopefully a rebuilt head will fix just not sure why the Metering plte is so high,

Thanks
Tim
Old 05-12-2013, 08:34 AM
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Tim,
I've got a rebuilt head sitting on the shelf if you need one.
If the fuel dampener in the head is malfunctioning/damaged you will not be able to control the pressures accurately. The Euro heads rust with advanced age and the metal diaphragms also distort with age and fuel pressure spikes. A multitude of things can go wrong once the passages begin to gum up or clog with rust.
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'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
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Old 05-12-2013, 09:00 AM
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The ethanol in the crappy E10 gas we use these days absorbs moisture out of the air in humid climates. Then it's carried through the fuel system and a cast iron euro fuel head will rust, mostly in the bottom areas of the fuel head like the bottom of the lower differential chambers where the water and ethanol mix falls out of the gas and collects. Water is heavier than gas and thats called phase seperation.

The ethanol is part of how they give E10 gasoline it's octane rating these days so as the ethanol mixes with moisture from humid air and seperates from the gasoline during phase seperation and corrodes internals of meachanical fuel injection systems like CIS the octane of the gas is dropping at the same time so engine damaging detonation can start happening at the same time.
Old 05-12-2013, 05:59 PM
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Fuel head being sent off for refurbishment. managed to find a porsche specialist that refurbs them. Hopefully this will rectify my issues. Thanks guys for the feedback.
Old 06-10-2013, 05:15 AM
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Maybe to late now but in the states this is the best place to send them... Home - CIS Flowtech
Old 06-10-2013, 07:06 AM
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Quote:
Originally Posted by JFairman View Post
Maybe to late now but in the states this is the best place to send them... Home - CIS Flowtech
Luckily enough i have found a place in the UK that can do it at a price that won't break the bank. I did think about the US as Brian had already offered but i have the issue of import duty and courier charges which then makes it very expensive going down that route. When i pulled the head off there were signs of rust at the mating face and the plunger was coated in a sticky substance. So probably the internals will need a good clean.

Cheers

TIM
Old 06-10-2013, 07:27 AM
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Fuel head has been tested and confirmed that there is an issue with the damper function. The calibrated orifice is twice the size of what it should be and this appears to be the reason why i cannot lean off my AFR's whilst on boost. and why the metering plate vibrates and the fuel pressure indications fluctuate. The Fuel head will be fully overhauled.
Hopefully i can get this car set up correctly.

Cheers

TIM
Old 06-14-2013, 07:19 AM
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what orifice are you talking about?

this is why i was looking for an original car. this one has a lot of the goodies i wanted, but i dont know everything thats been done or changed. ihave a euro head but who knows whats been done to it.

my car is fine on boost and idle, my cruise is too lean for some reason. timing, air leaks, fuel pressure who knows?
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Old 06-14-2013, 08:40 AM
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The oriice is internal to the fuel head. I believe it is located above the plunger which rests on the mass airflow plate. The fuel head has to be fully stripped to get access to it. The orifice assists with hte dampening of the plunger.
This won't affect an issue of too lean as mune is quite the opposite, very rich and won't lean out. Mine is a Euro car.

Old 06-14-2013, 12:50 PM
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