different flow rate for injectors

For discussing injector selection,manifold modifications, throttle bodies, fuel supply system design and construction, and FIdle valves and IACs.
Forum rules
Read the manual to see if your question is answered there before posting. Many users will not reply if the answer is already available in the manual.

If your question is about troubleshooting, configuration, or tuning, you MUST include your processor type (MS-I or MS-II) and code version in your post. If your question is about PCB assembly or modifications, you must also include the main board version number (1.01, 2.2 or 3.0).

If you have questions about MS1/Extra or MS2/Extra code configuration or tuning, please post them at www.msextra.com Such questions posted here will be moved to: a temporary MSextra sub-forum, where they will be removed after 7 days

The full forum rules are here: Forum Rules, be sure to read them all regularly.
Post Reply
ctchme
MegaSquirt Newbie
Posts: 12
Joined: Fri Dec 23, 2011 5:15 pm

different flow rate for injectors

Post by ctchme »

hey guys, i am currently making a tune for my nissan exa, and was wondering what would happen if i entered a larger flow rate for my injectors? would it just end up starving the engine of petrol? or would it actually work? Im sure its a dumb question but it had me thinking
kjones6039
Master Squirter
Posts: 618
Joined: Sat Jul 22, 2006 7:02 pm
Location: Eureka, Nevada USA
Contact:

Re: different flow rate for injectors

Post by kjones6039 »

ctchme wrote:hey guys, i am currently making a tune for my nissan exa, and was wondering what would happen if i entered a larger flow rate for my injectors? would it just end up starving the engine of petrol? or would it actually work? Im sure its a dumb question but it had me thinking
injector flow rate=injector flow rate

Nothing is ever going to change your injector flow rate, short of changing injectors themselves!

Ken

EDIT: Although increasing fuel pressure could increase flow within certain limits.
1979 Corvette - 383 CID SBC w/ Holley Pro-Jection 900 CFM TBI, 4-85 lb lo-z injectors & Walbro 255 pump
MS2 v3 w/ms2extra 3.4.0 Release
36-1, Delphi LS2/7 coils in wasted spark, driven by v2.0 logic board from JBPerformance
Spartan Lambda Sensor from 14point7
trakkies
Super Squirter
Posts: 1162
Joined: Tue Dec 30, 2008 3:06 am
Location: SW London, UK

Re: different flow rate for injectors

Post by trakkies »

ctchme wrote:hey guys, i am currently making a tune for my nissan exa, and was wondering what would happen if i entered a larger flow rate for my injectors? would it just end up starving the engine of petrol? or would it actually work? Im sure its a dumb question but it had me thinking
Changing the req.fuel does the same thing in effect.
Dave P, London UK.
Rover V-8
MSII V3
EDIS
Tech Edge Wideband
DonTZ125
Experienced Squirter
Posts: 337
Joined: Sat May 16, 2009 1:49 pm
Location: Scarborough, ON
Contact:

Re: different flow rate for injectors

Post by DonTZ125 »

If you lie to the ECU and tell it the injectors flow more than they actually do, it will use shorter pulses resulting in less fuel flow.
.boB
MegaSquirt Newbie
Posts: 18
Joined: Fri Oct 14, 2011 7:21 pm
Location: Colorado Springs, CO

Re: different flow rate for injectors

Post by .boB »

The ECU doesn't actually measure the amount of fuel injected. It calculates the duration of the pulse width based on the flow rating that you enter. If you tell the computer you have 50 pound injectors, it will use a pulse width 25ms (numbers I made up).

If you then tell the computer you've installed 25 pound injectors, it will use a pulse width of 50ms, in an attempt to get the same amount of fuel. But since you didn't really change the injectors, the engine will be getting twice as much fuel as it needs.
------
.boB
Factory Five Racing Roadster
427W, 8 Stack EFI, 600+HP
MS2 - Extra
Bernard Fife
Master Squirter
Posts: 475
Joined: Thu Oct 29, 2009 12:54 pm

Re: different flow rate for injectors

Post by Bernard Fife »

what would happen if i entered a larger flow rate for my injectors?
ctchme,

This is not as simple a question as I think you would like it to be. Firstly, for the most part the codes don't have a injector flow setting (the newest model based code do have such a setting), instead they have a req_fuel setting (and the injector flow is part off the req_fuel calculation).

If you put different number in the req_fuel calculator AND you adjust the VE table to match, then you will get the same fuel as before, and all will be well (assuming it was properly tuned in the first place).

If you put different number in the req_fuel calculator AND you DON'T adjust the VE table to match, then you will get different amounts of fuel. Putting a larger value for injector flow in the calculator than you actually have will lean out the engine, putting smaller value will richen up the engine fuelling. HOWEVER, if you have EGO feedback enabled, then this will compensate up to its limits under the conditions ego feedback is active (so probably not always).

None of this changes the actual physical flow rate of the injectors, as other have said.

The best and simplest thing to do is to use the most accurate number you have, and leave it at that.

Lance.
"Never wrestle with pigs. You both get dirty and the pig likes it.” - George Bernard Shaw
Post Reply