scootz
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| posted on 19/12/08 at 01:34 PM |
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Things to Consider When Buying Fuel Pump / Injectors?
What are the main things to consider?
I'm running a 4.2 V8, 12.5:1 CR, 8250rpm and 400-450hp.
I've yet to decide on injectors.
Any help establishing a flow-rate or brand recommendations would be appreciated!
Ta
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02GF74
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| posted on 19/12/08 at 01:57 PM |
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I have seen a chart somewhere listing injector size selection, just wracking my brains where ...
could be in one of the Ford performance magazines; I think Burton power list a couple.
from memory, the chart shows fuel rate vs bhp but not 100%.
whippy''ll be along to tell ya.
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scootz
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| posted on 19/12/08 at 02:05 PM |
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Come on Whipster... where are you man!
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mark chandler
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| posted on 19/12/08 at 02:23 PM |
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There are tables and calculators on the megasquirt sites
Link
 
Rescued attachment injector_flow.JPG
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scootz
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| posted on 19/12/08 at 02:28 PM |
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Hoorah for Mark!
Mr Whippy... YOU'RE FIRED!
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scootz
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| posted on 19/12/08 at 02:37 PM |
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So, I'm looking for 36 (ish) pound injectors!
Mr Whippy... you may be hired if you can help with recommending a Fuel Pump to feed those suckers!
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BenB
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| posted on 19/12/08 at 03:11 PM |
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http://users.erols.com/srweiss/tableifc.htm
Work out your estimated BHP.
Decide what your BSFC is (depends on engine date, NA / forced induction etc).
Divide estimated BHP by number of cylinders to give estimated BHP per cylinder.
Go for an injector witha 80% BSFC reading of about that reading.
Job done
Bosch injectors are widely available. People are always flogging injectors on Ebay, ask them to read the 0280 number on the side and cross-reference
the BSFC reading...
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BenB
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| posted on 19/12/08 at 03:14 PM |
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For a fuel pump look up the cc/min rate for the injectors. Multiply by the number of injectors. Add 10-20% on top. That's your flow rate
requirement.
Find a pump that beats that specification. Lots of cheap ones on Ebay....
These are cheap and they give the flow rates....
linky
Don't bother for going for anything massively over-spec'd. Otherwise you're just using more electricty to move the petrol into the
engine bay, heat it up a bit and then dump it back in the petrol tank..... Keep it cool, keep it powerful....
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BenB
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| posted on 19/12/08 at 03:20 PM |
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Don't forget to make sure you get the right type of injector. Some ECUs can drive high impedance injectors, some need low impedance.... You may
burn out your injector drivers if you use the wrong ones....
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scootz
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| posted on 19/12/08 at 03:50 PM |
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Thanks... just flicking through that site and DAMN his dad has big ears! 
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v8kid
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| posted on 19/12/08 at 03:52 PM |
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Guys I'm dissapointed in you where's the locost spirit!
The Cossie boys upgrade thier injectors from blue to green or whatecer so there are loads of blue injectors on the 2nd hand market. I bought three
sets of 4 from ebay, sent them away to get cleaned and rebuilt.
On return each injector had its individual flow chart so I could select 8 exactly matching injectors.
Easily makes over 400bhp on the rolling road and v smooth all at a locost price.
Injectors are low impedance so reqire a ballast resistor ( at least they do on a DTA box)
Bosch 041 pump easily handles the requirements if you search on this site i posted a story about the trials and tribulations of hp and feed pumps.
I now feed the Bosch pump direct from the tank with no feed pumps or seperate swirl pot and it works fine - with my tall narrow tank anyhow.
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scootz
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| posted on 19/12/08 at 03:55 PM |
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Nevermind the Locost spirit... DID YOU SEE THOSE EARS!
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v8kid
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| posted on 19/12/08 at 04:07 PM |
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Airbrakes?
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clairetoo
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| posted on 19/12/08 at 04:18 PM |
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quote:
Originally posted by scootz
Nevermind the Locost spirit... DID YOU SEE THOSE EARS!
Shhhhh...............He'll hear you 
Its cuz I is blond , innit
Claire xx
Will weld for food......
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scootz
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| posted on 19/12/08 at 04:32 PM |
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Sorry... did you see those ears?
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BenB
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| posted on 19/12/08 at 05:05 PM |
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Bed-time reading anyone?
"Honey I shrunk the BFG"
Spooooooooky
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BenB
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| posted on 19/12/08 at 05:08 PM |
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re: low impedance injectors with ballast resistors
Can be done BUT
- puts a higher load on the injector drivers and can burn them out
- slows down the opening of the injector
- reduces the cc / min flow rate
High impedance resistors are designed to have a large amount of current to wham them open then a smaller amount of current to keep them that way. Low
impedance resistors just use a medium amount of current throughout.
you can do it but it's a bodge....
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stevebubs
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| posted on 19/12/08 at 05:18 PM |
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quote:
Originally posted by scootz
So, I'm looking for 36 (ish) pound injectors!
Mr Whippy... you may be hired if you can help with recommending a Fuel Pump to feed those suckers!
Sierra Cosworth RS500 pump should be up to the job...
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Dusty
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| posted on 19/12/08 at 07:02 PM |
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quote:
low impedance injectors with ballast resistors
Didn't work with my Omex ECU and cossie blue low impedance injectors. Injectors just locked up at 4000rpm and flow rates dropped and got
progressively worse. First rolling road thought it was a poor fuel pump. Omex said ballast resistors should work. Mech Motorsport said don't
even bother. High impedance injectors was instant fix.
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MikeRJ
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| posted on 20/12/08 at 07:09 AM |
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The megasquirt tables/calculations always seem to give far too large an injector size. e.g. using the calculations, a 20XE should be barely capable
of making stock power on standard injectors (214.4 cc/min), yet you can get 200 bhp out of them with just a small pressure increase.
quote:
Originally posted by BenB
High impedance resistors are designed to have a large amount of current to wham them open then a smaller amount of current to keep them that way. Low
impedance resistors just use a medium amount of current throughout.
T'other way around. Low impedance injectors allow a high initial current for fast opening, but require the ECU to limit current to prevent
overheating (so called "Peak and hold" ). The lower holding current gives faster closing times, since the lower magnetic field collapses
more quickly.
High impedance injectors can take a sustained 12v feed without overheating (providing their is fuel going through them), but have slower opening
times.
[Edited on 20/12/08 by MikeRJ]
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jeffw
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| posted on 20/12/08 at 07:43 AM |
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Why don't you use the standard injectors and fuel pump from the B7 RS4 (I assume this is the engine your talking about). The injectors will be
good for 450BHP and the pump will be fine. Otherwise you'll need something like a Bosch 044R pump.
Don't forget that the injector flow pattern has a big effect on performance of the modern Audi engines, not sure if Cosworth Escort injector
will make the same power. MRC Tuning use Siemens injectors (mine are 660cc at 3bar for the B5 RS4) so might be worth talking to Doug again.
[Edited on 20/12/08 by jeffw]
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