Dear all, I try to understand how to choose fuel injectors. There are a lot of info here on the forum, but it isn’t so clear to me. My car is a 348 with ECU 2.5 and fuel regulator pressure are 3.0 bars. It seems that the original injectors are Bosch 0 280 150 731 (15.7 ohm, 18lb/hr, 192cc/min). Is it correct? The original engine power is 300CV. The injectors are too small for the power, no? We need something like 21/221cc, or I’m wrong? May I change my original injectors with 21/221cc? Is it ok with a 3.0 bars fuel pressure? Originals are 15.7 ohm, what is the tolerance? Thank you very much for your comment.
The basic rule is that a 250cc injector can flow about 50hp. So in an 8cyl engine with 250cc injectors, you can flow about 400hp, and this seems to work out with a Lexus 1UZ V8 my friend has in his race car, it literally makes 400hp. You can "cheat" a bit more flow by increasing fuel pressure which I think Ferrari did looking at the fuel pressure the 348 runs. The 192cc injectors in our 2.5 motronic cars are absolutely maxed out. You cannot simply put bigger injectors on the car without completely re-doing the fuel and ignition map. It is not a simple process. I intend to replace my fuel injectors in my 348 next time the engine is out, but I will also be wiring in a Link G4 ECU which we will use to tune the engine. It will be interesting to see how much more we can get out of it. I suspect the 192cc injectors were the best available back when they designed the 348, so they worked with what they had. I suspect this is why the F40 has two injectors per cylinder, there may not have been big enough injectors back in those days.
thank you for your comment... I want to change my injectors because the car has 40k miles on the clock and there are 'vintage'. The goal is to install 4 holes injectors. It seems that it is possible without any change. I've got 8 pieces (220cc/min à 3.0 bar with a 14.5 ohm resistance) in my stock. The resistance is just a little bit different, from 15.7 (original) to 14.5 ohm Do you think i can install them ? there are very close to the original but with 4 holes. If it is possible, i shall send old items for a Check-up.
You may want to read through this recent thread https://www.ferrarichat.com/forum/posts/148468139/ Considerations: 4 hole injectors will have more flow, especially during open loop operation when the O2 sensors are not yet functional to control stochiometric ratio. Fuel flow is based on airflow (MAF), coolant temperature and OEM ECU fuel maps during this period, so, more than likely, you'll be pumping in more fuel than you need during engine warmup. If the injectors are providing too much fuel (because of the 4 holes), during closed loop operation, the ECU may not be able to adjust the injector duty cycle sufficiently to get the right stochiometric ratio. ECU adjustment has a limited range. Again the car will be running rich. The spray patterns will be different. Will most of the fuel end up in the wrong part of the intake tract? There are known problems when running too rich and, as Euro cars have no CELs, you may not know you are damaging your engine. As Kev says, you may need to fit non-OEM ECUs and retune your engine for the new injectors.
one more detail, i don't want more power. I just want to be sure the injectors are ok and i want to use the pieces of my stock ... if possible.
You can have the injectors serviced and flow tested. I did this with mine when I had the engine out. I sent them away, they have these needles inside them called pintles, they have a tapered end on them that wears, this is pretty much the only thing that wears out in them. Have them serviced and they'll be good as new for another 30 years. You do not need to replace them unless there is some other problem with them. Make sure wherever you get them done, that they flow test them and give you a data sheet showing the results.
I sent my injectors to Mr injector who cleaned replaced the seals and flow tested them. They're basically as new spec. While I was in there I powder coated the fuel rails. Sent using FerrariChat.com mobile app
