One or Two Fuel Pumps

[iamchappy]

I was planning on using one 44 Bosch pump with my CIS injection.
I have a 86 930 intake with a Euro fuel distributor. I am not planning to run more than 14lbs of boost and dont wish anymore than 450hp if it comes to that.
(engines going in my 914 street car)

I have a 7th injector plumbed into the intake that would fire at 12lbs via pressure switch if I need it for the A/R's and cooling.

I was doing a search today and saw that my extra 79 SC fuel pump is the same one used for the front pump on the 930's.

Should I consider installing this along with the 44 or do you think the 44 will be able to handle the job all by itself.

[spuggy]

My mild 930 ran fine with good AFR's with only the stock '77 S fuel pump.

I intend to fit an 044 up front in the original location instead.

All these pumps are designed to run in series, I believe. Can't hurt to fit another if you have it.

Post pics - I wanna see what you do for the rear mount pump!

[iamchappy]

Henry at Supertec said all I would need is one 44 to do the job but having the extra pump laying around I thought maybe I could put it to good use if 2 works better than one.
What is the purpose of using two?

[Craig 930 RS]

OT - You like the idea of a seventh injector?

[iamchappy]

I used it with my BAE kit with the stock 70SC CIS.
I plumbed it into the new intake just before the throttle body.
I may never need to use it if the A/R's look good at 1 bar. This is
my street car and I doubt my engine will ever see sustained boost.
This is far from the optimum setup for ultimate performance as the a RPM enrichment 7th injector would be, but it worked for me in the past and if I need it I am sure it will work fine for my setup.
I am not going to worry about the optimum tweaking, I will do my best to get it to work with good and safe A/R's which I should have using the Euro fuel distributor. I really enjoyed the performance i had in the 914 using the BAE kit on the 3.0 SC engine at 8lbs. i felt it was plenty, this engine i may have to even tone down a bit to keep me from getting into trouble as it could be laying down up to 100 more horse power.

[spuggy]

Originally posted by iamchappy
Henry at Supertec said all I would need is one 44 to do the job

Cool, that's pretty much what I had believed from the spec sheet, but good to get it confirmed!

but having the extra pump laying around I thought maybe I could put it to good use if 2 works better than one.
What is the purpose of using two?

Most inline pumps will make a considerably higher flow rate if supplied by another pump, rather than simply gravity fed. It can also maintain that flow rate at a higher pressure.

The effect of operating at a higher pressure (like in a CIS system) is to effectively decrease the maximum flow rate of the pump. Also, the harder you work the pump, the more current it draws.

Using two pumps allows bigger flow rates at higher pressure.

Despite some conservative specifications for the 044, (Bosch quote it as 200LP/H on the Motorsport reference sheet, about 35LP/H more than they quote the stock pump), Jay Racing had some flow charts that compared it to the Walpro "255" pump and showed it flowing much, much more fuel. Like 60+% more fuel, especially at the high end.

They seem to have just re-organized their web site, and that chart isn't there anymore, but there's still some useful info here.
http://www.jayracing.com/index.php?main_page=product_info&cPath=2_5&products_id=1

There's some good Bosch cross-reference information and specs in these links:

http://apps.bosch.com.au/motorsport/downloads/fuelpumps.pdf
http://apps.bosch.com.au/products/saa/efi_crossref.pdf
http://apps.bosch.com.au/products/saa/efi_techserviceparts.pdf

There's even vehicle-by-vehicle application sheets here, just the thing for digging around breaker's yards:

http://apps.bosch.com.au/products/saa/efi_vehicleapplications.pdf

If you were going to use two pumps, I'd be inclined to put the 044 last, or use two 044's. But you should remember that I have no expertise here, and this is just my gut feeling...

Excess capacity only means the pumps aren't worked as hard, and the fuel is pumped around faster - thus kept cooler. It's all good.

Cheers,

Andy

[RarlyL8]

I used the stock front SC pump and purchsed/added a stock 930 rear pump. Here is a picture of the rear pump and home made brakcet.

[iamchappy]

Well looks like my questions have been answered. I think I will install both, why not!