Watts Shop Performance
Injector Sizes = HP
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Diesel Performance
Companies that make and/or sale diesel injectors, all rate there injectors
differently. Most companies rate there injectors as HP over the stock horsepower of
the stock injector. Example: 2001 Dodge Cummins is rated at 235 HP and the HO
is rated at 245 HP. So if a company sells a 100 HP injector or nozzle, that is 100
HP over the stock 235 Hp injector. That is a 335 total HP injector or nozzle. These
companies rate their injectors or nozzles as total HP. A few other companies rate
their injectors or nozzles by LPH (Liters Per Hour). This is fine but LHP can change
do to pressure. High pressures will flow more through an orifice verse the same
orifice with a lower pressure. So, unless you have a industrial wide standard
pressure for these injectors or nozzles. You can give a HP rating to the injector or
nozzles. Now here is where it gets tricky. The other half of the companies out there
(bigger named companies) do not rate their injectors or nozzles by Hp over stock.
They rate them by size, by the number of holes and the size of the holes. Example:
6x18, 7x14, 8x13, 5x22, ect.... Each one of the injectors or nozzles performs
differently, do to number of holes and how many holes. But, given the X number of
holes and the X size of the holes. You can get a general idea of the HP of the
injector or nozzle. This is not exact. There are companies out there that sell
injectors or nozzles of different number of holes with different size of holes but
have the same HP rating. Example: 6x18 and 7x17, these companies sell both. Say
that these injectors or nozzles are 300 HP over stock. Well, that's not really true.
Cause now you get into the CROSS SECTION AREA of INJECTORS. This is where
it gets REALLY TRICKY! Using the earlier example, 6x18 and 7x17. The CSA
(Cross Section Area) of a 6x18 is 0.0015268 and the CSA of the 7x17 is 0.0015889.
So the 7x17 is slightly bigger in CSA, so it should make more HP. Not exactly.
There is alot more involved that just number of hole and size of holes. The number
of holes and size of holes has an affect on atomization of the fuel. The rule of
thumb is the less number of holes with larger hole size, tend to be dirty. 5 hole
injectors or nozzles are dirty than 6 hole injectors or nozzles. 6 hole injectors or
nozzles are dirty than 7 hole injectors or nozzles and so on. The more number of
holes and smaller holes atomizes the fuel better. This will cut down on smoke while
driving and under WOT. But as you increase the number of holes and inlarge the
holes. You run the risk of mechanical failure of the injector or nozzle tip. This
mechanical failure is basically the tip cracking between the hole and then breaking
off. Then you end up having a mechanical issue with the engine. You end up
breaking a piston, trashing valves and valve seats or worse case destroying the
engine. So it is better to run a 7x14 verse a 8x13 injector or nozzle. The reason is
there is more material between the holes and less chance of breaking the tip off.
Then there is POP Pressure of the injector or nozzle to deal with. What POP
pressure do you run. Well that all depends on if it is a 12v or a 24v. This does not
apply the Common Rail Cummins as they are EFI not mechanical injectors. Using
the 24v as the example, there is a range on the POP Pressure. This range, ranges
from 3800 psi (262 Bar) to as high as 4500 psi (310 Bar). Alot of companies say not
go below 260 Bar (3770 psi). POP Pressure has an effect on timing, smoke and
atomization. Plus high POP Pressures have an effect on the fuel being sprayed
into the cylinder under high boost pressures. Also, every 10 Bars = 1 degree of
timing. 1 Bar = 14.5 psi and 10 Bars = 145 psi. So added 10 Bars of pressure
REDUCES the timing by 1 degree and lowering the pressure by 10 Bars ADDS 1
degree of timing. But lower the BAR pop pressure also has an effect on smoke,
more smoke. Rule of thumb is higher POP Pressures help with street driven trucks.
Lower smoke, better throttle responce, better drivability  and a little lower egt's.
That is why it is hard to give an exact HP rating to injectors or nozzles, cause there
is so many factors that go into it. On top of all this info, you need to have enough
air (big enough turbo) to take advantage of the extra fuel to reach that HP rating of
the injector.
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