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Dr J Dr J is offline
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Join Date: Apr 2008
Location: Miami
Posts: 680
Flow test- not getting enough fuel

I am completing a rebuild and putting a supercharger. Since the components are apart, I did a flow test on my CIS system. Here were the test conditions:

Vehicle 79SC
Bosch fuel distributor had the numbers O 438 100 031
WUR had the numbers O 438 140 042 which should match
New CIS injectors with good spray pattern (these are 79SC injectors no electricity)
Fuel is old ~ 1year but was stabilized from the beginning
Fuel distributor had not been used for 1 year but was previously exercised, by connecting it to the CIS and cleaned through a FI cleaner until the system responded correctly (properly regulating system pressure)

Test parameters:

CIS by itself plumbed into the fuel system (engine is somewhere else in the garage)
Current draw of the fuel pump during test: 10.4 A
Voltage at the battery during test 12.22V
System Pressure during test: 5.1 bar
Temperature: 73F/23C (apologies to those up north)
Test time: 1 min

Connect the CIS plumbing to the vehicle
Put glasses underneath each injector
Bleed the CIS gage
Bleed the injectors until there is a good flow
Push up on the air flow sensor plate control lever to maximum limit
Simultaneously time the test
WUR not in line (used CIS pressure measurement valve to cut off WUR)

All injectors flowed nearly identical amounts of fuel
Measured fuel per injector was 150 ml
Fuel had varying levels of turbidity:
Cyl 1 clear, Cyl 2 some, Cyl 3 slight, Cyl 4-6 moderate
(when the test was repeated, had Cyl 1, 2, and 4 clear and 3, 5, 6 some, with 6 being the worst in all cases)


When placed into the formula:
HP = (flow in ml/min * # injector)/(10.5 * BSFC) I get:

(150 ml/min * 6)/(10.5 * .55) = 156 HP

Way too low for SC and much too low for Supercharged system.

Does anyone see any error in my procedure?
Is there any other thing I should check?

Below is an image of the fuel across all glasses (ignore the lines they were from a previous less formal test which motivated this test). The last glass contains water at the same level for measurement without ruining an extra glass:

Picture of the test setup:
1979 SC, Slant nose wide-body cab conversion. AEM Infinity EFI. (Whipple Supercharger currently off for rebuild)

Last edited by Dr J; 01-18-2010 at 03:44 PM..
Old 01-16-2010, 04:12 PM
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