What Exactly Happens When.injector Duty =100%
01-29-2003, 01:13 AM
#17
Senior Member
Join Date: May 2002
Posts: 334
Two things:
Is there such a thing as to run too low a duty cycle? Perhaps you have some gigantic injectors on a stock motor. Would there be any drawbacks besides a little rougher idle?
Is there anything else that should be taken into account when upgrading the fuel system? Injectors, Fuel pump, etc. How about fuel rail, wiring, etc.?
Thanks.
Kyle
Is there such a thing as to run too low a duty cycle? Perhaps you have some gigantic injectors on a stock motor. Would there be any drawbacks besides a little rougher idle?
Is there anything else that should be taken into account when upgrading the fuel system? Injectors, Fuel pump, etc. How about fuel rail, wiring, etc.?
Thanks.
Kyle
01-30-2003, 06:17 PM
#18
Senior Member
Join Date: Nov 2002
Location: PHX
Posts: 265
In most applications it would be best to keep the stock primaries. This way you can have a good idle. When you really need more fuel than the 550's can supply will be in the higher rev ranges so you get the 1300 or 1600 secondaries and can reduce the duty cycle for them. This gives you small enough primary injectors that you can pass emissions at idle and large enough secondaries to get all the power you want at higher rpm.
02-03-2003, 01:45 AM
#19
Member
Join Date: Aug 2002
Posts: 65
Duty cycle = (on time/(on time + off time) x 100
Therefore 100% duty cycle means the injector is turned on all the time. Obviously the injectors cannot supply any more fuel past this point unless the fuel pressure is bumped up which is a lousy way of trying to fix the problem. As already stated big injectors are useless if the pump cannot keep up.
No offense to Dragon cause he has taught me a bit about turbo stuff and his FD makes mine look like a piece of ****, but I disagree with his statement abount injector flow decreasing at high duty cycles. I have heard this argument before, but from my experience it just doesn't happen.
Yes there are problems with having very large injectors and running very low duty cycles at idle. The resolution is dereased dramatically. i.e. a 1% change in duty cycle gives a large change in the amount of fuel being delivered, so it is harder to get a good tune at idle/cruise. Thankfully us EFI rotary owners have staged injection so we can have smallish primarys and big secondaries and get the best of both worlds.
Therefore 100% duty cycle means the injector is turned on all the time. Obviously the injectors cannot supply any more fuel past this point unless the fuel pressure is bumped up which is a lousy way of trying to fix the problem. As already stated big injectors are useless if the pump cannot keep up.
No offense to Dragon cause he has taught me a bit about turbo stuff and his FD makes mine look like a piece of ****, but I disagree with his statement abount injector flow decreasing at high duty cycles. I have heard this argument before, but from my experience it just doesn't happen.
Yes there are problems with having very large injectors and running very low duty cycles at idle. The resolution is dereased dramatically. i.e. a 1% change in duty cycle gives a large change in the amount of fuel being delivered, so it is harder to get a good tune at idle/cruise. Thankfully us EFI rotary owners have staged injection so we can have smallish primarys and big secondaries and get the best of both worlds.
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