Fortunately for 2.0L Probe owners our cars are equipped with topfeed injectors. Aftermarket, topfeed injectors are much more readily available than the sidefeed injectors of our older brother the Probe GT. The 2.0L injectors is referred as a topfeed "Nippendenso" style (according to RC Engineering), which is pretty standard on most Japanese cars, like Toyota and Mitsubishi. This style injector has an o-ring seal on the top side of the injector, and a "gasket style, donut, bushing" on the bottom side. The pictures below will help clearify. While the top o-ring seals on the outer diameter of the injector and the inner diameter of the fuel rail port, the gasket seal on the bottom seals differently. The gasket itself is comprised of two parts. The "gear-like" ring is actually a plastic ring while the actual seal is molded to fit around the inside, top and bottom of the plastic ring. The top side of the gasket seals against the lower shoulder on the injector (refer to picture). The bottom of the gasket seals on a shoulder that is located on the intake manifold. The 2.0L injector part number is INP480, which is a Mitsubishi injector. Who actually manufacturers the injector is still unknown. Injectors fall into two basic catagories: saturated and peak-and-hold. The 2.0L has saturated injectors which are a little more expensive than the peak-and-hold. The resistance between the two electrical terminals should be around 15 ohms, compared to peak-and-hold's 3 ohm resistance. RC Engineering has ran flow tests on several INP480 injectors and they all had flow rates that ranged from about 215-220 cc/min at 43 psi fuel pressure. This translates into about 21 lb/hr injectors. At this fuel pressure and flow rate our injectors are good for about 135 horses at 80% duty cycle, with a Brake Specific Fuel Consumption (BSFC) of .5. You can alway up the fuel pressure to achieve more flow, but he said that these injectors can only handle about a 80% duty cycle because the actual "valve" inside the injector is approximately 4 grams, supposedly this is heavy for an injector, so it makes it hard for it to open and close rapidly.
As for aftermarket injectors, RC Engineering claims that the largest saturated fuel injector manufactured is a 440 cc/min at 43 psi, which they claim would be suitable for my 300 hp goal, but I would have to increase my fuel pressure (approximately 60 psi by my calcs). The injectors that RC Engineering sells are supposedly the lastest in technology. The bodies are stainless steel. The "valve" only weighs a fraction of a gram. With this lightweight "valve" the injector can safely operate at duty cylces of 90% or more. They offer these injectors for almost $90 a piece. This seems so cheap, since I priced our factory injectors at the dealership for a $320 each ($195 each at Mazda). The also offer lower flowing injectors as well, which are a little bit cheaper, but If the 440 cc/min injectors are too small you are not out of luck. RC custom makes larger flowing saturated fuel injectors, but the price jumps to about $135 each or more.
No. . . the result is more fuel, but your motor will not injest enough air to completely burn that extra fuel, so the result is simply a rich mixture that will hurt overall performance.Cruzan said:This is some very interesting info....
My question is....and I am trying to understand what you wrote.......does increasing injector size along with fuel pressure result in more horsepower?
No. . . the result is more fuel, but your motor will not injest enough air to completely burn that extra fuel, so the result is simply a rich mixture that will hurt overall performance.
BryanPendleton said:With serious, aggressive cylinder head work and aggressive cams you would want larger fuel injectors. Why? With aggressive head work and cams you sacrifice low rpm volumetric effeciency (VE) but gain high rpm VE, resulting in more torque and power in the high rpm range (7000+rpm). At those rpms my guess is you would exceed the duty cycle of the OE injectors. . . but with all that work you would need some way to control it all. . . . reprogramed ECU is one way, but could be trial and error, and considering you have to ship your ECU off, would be a pain.