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Thierry25 Thierry25 is offline
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Join Date: Feb 2009
Location: FRANCE (Besanšon)
Posts: 310
Originally Posted by 911st View Post

You are the man!!!

Might test with half the injectors 3.3 and half 3.6 at the same time then poor the gross from each side into its own measuring beaker.

Or what ever you think is best.
Hello Keith

Glad to let you know that I did this test .

As beeing said, everything was the same during the test procedure....everything except the fact that the 3.3T injectors are new parts and 3.6T injectors are used.

I installed a fuel pressure gauge on the head in order to make sure I've got the same system fuel pressure during all the tests. ( It was the case !!)

By this opportinity, I noticed that my fuel pressure was at 8.5 bar under cold condition. In both case, the fuel system pressure drop to nearly 7.2 bar while I actionned the metering arm in it maximal position. ( It makes a kind of Star Wars noise while the injectors deliver fuel ). Even with my upgraded 044 front fuel pump, the system pressure is dropping. So there is absolutely no doubt about the utilty to up grade the stock fuel pump !! in order to get more fuel with CIS !!!

With new 3.3T injectors ( ref bosch 0437 502 017 ) I 've got an average of 245 ml/ min . The variation between each injectors flowed fuel volume was about 6-7%. . It seems these 6-7% are exactly what we get without accurate head adjusting . ( STU related very similar tolerance in his several experiences).

With old 3.6T injectors ( ref bosch 0437 502 057 ), I've got an average of 265 ml/min. However I was incredibly impressed by the poor quality of the fuel pattern as well as the increased min/max volume tolerance. I 've got about 12% of difference between min and max . ( I have on injector which flowed about 275 ml /min) . I was scared to see this and to think that many engines are runing with such injectors variations !!!

Lastly, after comparison, I 've made a fine tuning of the head in order to reduce the difference between each new 3.3T injectors flowed volume. It is not such easy task since we are talking about 5-10░ of rotation on the head adjustment screws. However, after 4 tests, I succeed to reduce the tolerance at 2% only ! By the way, as I got already much enough fuel for my car setup I didn't try to increase the flowed volume by playing on the head. However, considering the fast action of the adjsutment screws, I do believe that I could have get about 260 ml /min ( using 3.3T injectors) if I put the head screws to near their maximum position. Thus it could have been nearly 280-290 ml/min with the 3.6T injectors.
965 C2T / 1991 3.3 TURBO
Old 02-06-2010, 08:47 AM
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