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Crotchety Old Bastard
 
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Modified fuel heads are a different animal and as Jim states not apples to apples compared to the US head.

Stock vs stock the Euro system flows more fuel than the USA and has no Lambda system to malfunction. Head flows more, lines are bigger, WUR is different, fuel injectors flow more.

Modified, yes the USA is superior. The head is modified to eleminate the frequency valve/Lambda system and the ports are adjusted to flow more fuel. I have spent the better part of today working on a 965 that had the USA fuel head modified. It was blowing so much fuel it would hardly run. That is what happens when a modded head is simply popped on with no attention to the needs of the engine. I replaced that controlled gas leak with a freshly rebuilt stock Euro unit. This car is 350WHP so that is a good fit. It now runs perfectly with a nice fuel curve (yes the WUR is adjustable).
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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 07-16-2011, 01:15 PM
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That is what happens when the 4 adjustments on the adjustable WUR are not set up right for the fuel head in use.

You need an accurate digital AFR gauge in the car while driving and logging AFR's on a laptop or having someone watch the gauge while you drive and call out the AFR's and then you try and remember them.
A CIS pressure gauge helps too.

It takes longer than an afternoon to figure it all out and get it right.
Old 07-16-2011, 01:32 PM
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thanks for the input, I will discuss it with my mechanic
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Old 07-17-2011, 06:55 AM
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Crotchety Old Bastard
 
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Quote:
That is what happens when the 4 adjustments on the adjustable WUR are not set up right for the fuel head in use.
Not in this case. This fuel head had been adjusted wide-open on a 350WHP engine. The fuel output was beyond the adjustment capabilities of the WUR given the needs of the engine. There is a sweet spot of adjustment for the WUR. What I do is match the fuel head and WUR to each other and that combo to the needs of the engine. That is also one way to optimize fuel economy. My goal is to have the system just at the point of leaning out at redline and then tweak in a couple tenths of an AFR point for safely. If you slap on a big head and adjust the WUR to compensate you leave a couple miles per gallon on the table. Nowdays that's a big deal.
This is off-topic for this thread but it may give more insight as to what Jim and I are talking about.
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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 07-17-2011, 09:34 AM
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so is this a car specific thing? in other words if my mechanic cant get it right do we pull it off the car and send it off to be be dialed in or is it something that a good mechanic just works through and dials it in.
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84 930 Slant
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Old 07-17-2011, 09:53 AM
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the latter...
and were talking obsolete mechanical fuel injection designed to pass emission requirements that was discontinued a long time ago.

most of todays younger working mechanics only have experience on newer OBD and OBDII efi cars and dont know much about CIS and don't want to learn because it's complicated, takes time to learn well, and is now obsolete so instead they take a negative attitude biased by their ego's and won't learn.. and instead make lame excuses.
Old 07-17-2011, 10:14 AM
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Crotchety Old Bastard
 
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What Jim and I are talking about is beyond the scope of this thread. The operational range of the stock fuel system is set on the rich side purposefully by the factory as a safety margin and to fuel cool the heads. Your car was running well on the system that is on it now so all is good. There is opportunity for improvement, should you wish to do so, as the factory settings, both Euro and USA are on the rich side. Most mechanics do not do this as it is time consuming and in most cases not necessary unless you are an enthusiast and wish to improve on OEM or your engine is modified and tuning the fuel becomes mandatory.
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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 07-17-2011, 08:37 PM
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