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Ken911's Avatar
 
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Location: Loxahatchee, florida
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Fuel system pressure

So how do I adjust the fuel system pressure up to 7.5 bar?
I looked in the manual and it says how to check it but not adjust it. I have an adjustable WUR but brian told me I may have to adjust system pressure up since i went to a higher displacement and compression ratio.
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88 turbo Guards red Targa slant nose, and yes I am a horsepower junkie, 3.4liter,7.5 to 1 JE pistons, Adjustable WUR, Imagine fuel head, 1 bar waste gate headers,allthe cis toys. Now apart to become the next EFI monster. fabbing my own intake, headers Individual throttle bodies, MS-3, pauter rods, Xtreme twin plugged heads, gt-2 evo cams cop's.
05 Cayenne S lapis blue
Old 03-21-2010, 06:21 PM
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you add shim(s) under the little spring in the system pressure regulator on the fuel head. it's like little precision washer(s) stacked under the spring to set it's tension when all is screwed back into the fuel head.

you can unscrew it from the fuel head carefully, it's not in tight and you'll see all the little parts.
Old 03-21-2010, 06:46 PM
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any idea how many shims or the thickness?
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88 turbo Guards red Targa slant nose, and yes I am a horsepower junkie, 3.4liter,7.5 to 1 JE pistons, Adjustable WUR, Imagine fuel head, 1 bar waste gate headers,allthe cis toys. Now apart to become the next EFI monster. fabbing my own intake, headers Individual throttle bodies, MS-3, pauter rods, Xtreme twin plugged heads, gt-2 evo cams cop's.
05 Cayenne S lapis blue
Old 03-21-2010, 07:01 PM
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Shims are number 3 here

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Old 03-21-2010, 07:09 PM
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no.. my fuel head is modified by flowtech. it's the old imagine auto modified usa fuel head so it is already shimmed to higher pressure.
i think you'll have to experiment with them.

the shims in mine are probably around .010" - .020" thick each and there are 3 stacked together but i never measured the thickness of them.

you can email Larry at CISFLOWTECH
Old 03-21-2010, 07:16 PM
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7.5bar is a little high, I would shoot for 7.0bar and see where your AFR's are at redline on boost. 100lb is 1 extra shim if you start off with stock pressure. Adding more pressure than you need will waste fuel and make it hard to tune in other areas.
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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 03-21-2010, 09:39 PM
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Where can soemone order the shims from?
These are hard to find.....
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Old 03-22-2010, 05:06 AM
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I use small washers.
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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
Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8
Old 03-22-2010, 11:51 AM
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Quote:
Originally Posted by RarlyL8 View Post
7.5bar is a little high, I would shoot for 7.0bar and see where your AFR's are at redline on boost. 100lb is 1 extra shim if you start off with stock pressure. Adding more pressure than you need will waste fuel and make it hard to tune in other areas.
Brian leask told me I need to do that with the larger displacement and higher compression that i have now. mine is still running lean when it gets up in power. and of course the clutch is on it's last legs some things never end.
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88 turbo Guards red Targa slant nose, and yes I am a horsepower junkie, 3.4liter,7.5 to 1 JE pistons, Adjustable WUR, Imagine fuel head, 1 bar waste gate headers,allthe cis toys. Now apart to become the next EFI monster. fabbing my own intake, headers Individual throttle bodies, MS-3, pauter rods, Xtreme twin plugged heads, gt-2 evo cams cop's.
05 Cayenne S lapis blue

Last edited by Ken911; 03-26-2010 at 06:17 PM..
Old 03-26-2010, 06:15 PM
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Give it a go and see how it goes, I like to run as lean as is prudent for better mileage.
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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
Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8
Old 03-26-2010, 06:26 PM
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Ken,

I would not think that with the HF head's already increased fueling capacity and being able to access more fuel with lower control pressure on boost using the adjustable WUR that you would need to bump system pressure further.

In most cases the cast iron HF head should deliver another point of richness by its self (8-10%). There should also be another point of fuel richness by lowering on boost control pressure agressively. For example, the HF FD should take you from say 14/1 to 13/1. The lower CP should then take you form 13/1 to 12/1. That is, the two should get you about 15-20% more total fuel or so at full tilt.

However, one should note that at some point when trying to increase the system pressure, the fuel pumps many or may not be able to support the increased delivery pressure. As Brian said, 7.5 is getting pretty high.

Unfortunately and as noted: the HF fuel head, bumping SP, and or lowering control pressure can increase fuel delivery places you do not want it.

When taking our CIS out of spec to deliver more fuel up top we need to also balance against this by taking our WUR out of spec to compensate.

I suspect one might start by setting on boost CP so it can deliver the fuel you need at high rpm and not more.

11.5 to 12/1 at HP peak and up to 12.5 at red line seems ok. 11.5 at HP peak would be safer but you do not want to be any leaner than about 11.8 at TQ peak is my thinking or opinion for what it is worth. This is usually not an issue if you can stay under 12.5 at red line. Yes, 12/1 at red line would be nicer.

Then, you should try to increase pre-boost control pressure and play it off against your on boost CP to bring your idle and cruse AFR's back in line. You may have to use the factory CO adjustment screw to get idle AFR where you need it. It is the cruse AFR that needs a higher pre boost CP.

Basically you are after increased pre boost control pressure and decreased on boost control pressure. All these settings are interrelated so adjusting one may effect another so it is kind of trial and error.

If you needed a lot of extra fuel up top and you are making big HP numbers, this will leave you with a fat AFR on first boost. If you are dropping solidly into the 9's, this is where many use the BL boost clamp to delay enrichment.

A better set up would be the use a Digital-WUR. In my opinion, the D-WUR is the key to unlocking the potential of high flow fuel distributors.
Old 03-28-2010, 08:26 AM
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