the fuel pressure REGULATOR regulates the injection pressure to remain CONSTANT
when the manifold is under vac the fuel is being sucked out of the injector thus MORE fuel is sprayed
when the manifold is under pressure (boost) the fuel is being pushed back in the injector thus MORE pressure is needed to keep the injector spraying the same amount of fuel
here's an example
Manifold Pressure MAP
Fuel Pressure
INJ PW
Amount of Fuel Injected
-18 in hg
29
2.0
0.0063
0 (atmos)
39
2.0
0.0063
18 PSI
58
2.0
0.0063
as you can see in the example above , the fuel pressure is adjusted to REGULATE the injector pressure that way the injection pressure remains constant
exactly why they call it a REGULATOR
Why 80's?
I highly recommend the 80s because they are excellent injectors and have very accurate low pulsewidth control,
the siemens deka high impedance injectors are a completely new design, up until about 8 years ago,
all injectors shared the same basic design, if you cut open an injector from a 1988 mustang or a 1998 mustang
the internals are basically identical which is 30 year old technology, it wasn't until a few years ago the modern
high flow OEM grade injectors that are available today were released, these new injectors no longer have the
terrible low pulsewidth control that large injectors are notorious for
I highly recommend the 80s because they have excellent low pulsewidth control, excellent atomization,
and very linear flow characteristics, and when buying new injectors the price doesn't really fluctuate that much
based on the injectors size.
these injectors usually sell for $45/each or $360 for a complete set of 8, i recommend to shop around, and be on the look out for fakes,
as of lately there's been a bunch of knock off china made fakes hitting the market that are absolute garbage, only buy from a trusted vendor
most of the the vehicles I tune end up getting either a larger turbo, more nitrous or additional engine mods and thus have to get larger
injectors to support it which then requires a re tune, however, most of these engines would not have to be re tuned if the larger injectors
were in there from the get go, so it saves both of us the hassle lol
Thats why I always recommend 80s since there's no downfall and they aren't much more price wise than a different sized set. If you spend a
little more and do it right the first time, that's one less thing you have to worry about later on down the road when you decide you want more,
sooner or later you will want more, i can guarantee it
just so you know, you don't have to get the 80s if you don't want to, but that is what i recommend if you ask me, which ever size you decide to go with is fine,
so long as you get injectors that will support your engines needs you won't have anything to worry about (until you decide you want more)
If you feel that these injectors are too large for a stable idle, rest assured as the Siemens Deka are the OEM injectors on the factory CobraJet vehicles.
For reference, the Injector Positive Ignition 12v+ Relay feed should always go to the right side of the connector where looking at the connector with the center indention down.
