New larger injectors

For discussing injector selection,manifold modifications, throttle bodies, fuel supply system design and construction, and FIdle valves and IACs.
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neal1980
MegaSquirt Newbie
Posts: 2
Joined: Fri Feb 18, 2011 12:26 pm

New larger injectors

Post by neal1980 »

Hi,

I cant get a definate answer on this and dont want to bugger things up so here goes.

I have fitted larger injectors to my rebuilt engine im running MS1 Extra.

Do I just have to change the req fuel for the new injector settings only??

Or do I have to go in and under one of the options saw something about old req fuel and new req fuel and this changes the VE tables.

I understand it will need final tuning but just want to get roughly somewhere so I can run a few miles in.

Many Thanks

Neal
Matt Cramer
Super Squirter
Posts: 2951
Joined: Sat Jul 03, 2004 11:35 am

Re: New larger injectors

Post by Matt Cramer »

You need to change Required Fuel, Cranking Pulse Width, and Acceleration Enrichment. Maybe Injector Opening Time too. The rest is unchanged.
neal1980
MegaSquirt Newbie
Posts: 2
Joined: Fri Feb 18, 2011 12:26 pm

Re: New larger injectors

Post by neal1980 »

I have also changed from 2.5 bar to 3.0 fuel pressure, is there a calculation to allow for this or will it still be in a good range to get it running in??

Engine is a rover v8 old injectors at 3 bar were 210cc / min but were running only 2.5 bar for my req fuel calculation.

My new injectors are 350cc / min at 3bar which I now have with a new fuel pressure regulator.
DonTZ125
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Posts: 337
Joined: Sat May 16, 2009 1:49 pm
Location: Scarborough, ON
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Re: New larger injectors

Post by DonTZ125 »

Flow increase through a fixed orifice is a function of the square root of increased differential pressure; Q2^2 ~ Q1^2 x (P2/P1)

You've increased your dP by (3/2.5) = 1.2; your flow will increase by a factor of 1.095.

This is theoretical math, real world factors in your piping will also contribute with minor flow losses.
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