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914World.com _ 914World Garage _ Aftermarket EFI question

Posted by: jhadler Dec 14 2005, 03:47 PM

For those who have installed aftermarket EFI systems, what size injectors would you recommend for what is basically a stock 2.0L four-banger?

-slightly- higher compression than stock, with headers and I/R throttles.

The basic calculations I did say that 17# is enough, so I figure some nice Ford 19# injectors would be just fine. Am I off base here?

Thanks

-Josh2

Posted by: McMark Dec 14 2005, 03:50 PM

Most people use a stock setup in terms of plenum, runners and injectors. The 1.7 injectors are actually big enough for a 2.0, and 2.0 are even a bit larger. No reason to go aftermarket.

Posted by: fiid Dec 14 2005, 03:54 PM

From what I understand - the 1.7 injectors are significantly oversized - so they ought to be sufficient for perhaps even a turbo setup.

Anyone remember what the flow-rates are (in metric pls?).

Also- the D-jet runs fairly low fuel pressure. If you got even close to trouble you can crank that up a fair bit to get some more headway - or better yet use a fuel pressure regulator that increases pressure with manifold pressure.

Posted by: Mueller Dec 14 2005, 03:58 PM

RB Racing has a neat fuel injector calculator near the bottom of the page http://www.rbracing-rsr.com/fuelinjectors.htm

plug in the numbers and it'll tell you if you picked too high or too low of a injector based on the info you plug in...

Posted by: airsix Dec 14 2005, 05:05 PM

Use stock D-jet injectors or something even smaller. Subaru 1.8T injectors are a good substitute. They have a hose-barb and fit the stock plenum and fuel-rail if you use the rubber mounting dounuts from the D-jet injectors. They are the same impedence as the D-jet, and flow about 75-80% of what the 1.7 (yellow) injectors flow. They would be more than enough for a hot 1.7 and probably plenty for a warmed over 2.0. YMMV.
-Ben M.

Posted by: jhadler Dec 14 2005, 05:09 PM

I have the stock D-Jet, and am planning on going to a fully programble EFI (megasquirt) over the summer maybe. I already have the throttles, so conventional Bosch style fuel injectors will be needed. Can't use the stock injectors, they don't fit...

-Josh2

Posted by: Ray Warren Dec 14 2005, 07:37 PM

I am using the 1.7L injectors on a stock 2.0L with SDS fuel injection and
even they are a bit over kill.
If I recall they are 265cc injectors which should be good for about 175 HP
at 100% duty cycle. Ideally I think you want to run around 80% duty cycle.
You could probably run something around 200cc to 225cc without any problems.
keep in mind these numbers are based on 100 HP 4 cyl engine.

Posted by: Ray Warren Dec 14 2005, 07:47 PM

Here's a chart

Attached image(s)

Posted by: Tom Perso Dec 14 2005, 08:01 PM

Yup, what these guys said. Use 1.7L injectors with resistor packs (or a flyback board, if you're getting froggy).

The 1.8T injectors sound cool, I might have to take a peek at how much those are.

I'll be MS'ing a mild 1.7 over the winter.

Tom

Posted by: TimT Dec 14 2005, 08:07 PM

That chart is misleading, it shows BSFC at 0.55 which is outside what a normally aspirated engine lives at.. also a rule of thumb is to generally never exceed 80-85% duty cycle.

19# is fine.. Marren has blueprinted 19# injectors for $140/4

Posted by: Brett W Dec 14 2005, 08:16 PM

I don't know about the Bosch injectors but the Honda injectors are peak hold types that flow 240cc. They will handle well over two hundred HP on an engine that is much more efficient than the stock T4. You can ususally pick them up for about 25-50$. Peak Holds react much faster than saturated types. They will idle better and open and close faster. Although not really important for stock NA motor using small injectors, when going to 500-1000cc injectors you have to have some that respond very quickly to get it to idle.