How much horsepower will 250cc injectors support with 10:1 FMU. Online calculators say approx 400 crank if my math is correct but some members have talked about leaning out much earlier...any ideas?
Which FMU ratio should be adequate with 300cc injectors?
Are you comfortable running those sorts of fuel pressures? Ive never bothered with FMU. If fitting a turbo I much prefer the ability to tune it properly. Some of the mapping of stock ecu is pretty unrefined to begin with.
I understand it is less than ideal but I know of more than a few members who run an FMU. I am in a country with no dynos and no tuners and I do not want to deal with fighting the ecu when it keeps relearning the tune from a piggyback so I have decided to stick with manual tuning via FMU (and possibly meth injection to control detonation if needed). Not only that but I know that 8psi (72trim) should be okay with an FMU although it may (or may not be) be rich. I do plan on purchasing a Vortech recalibation kit to raise or lower FMU ratio depending on AFR wideband numbers. I will also run 300cc injectors to reduce the pressure. 6:1 on 300cc provides better flow than 10:1 on 250cc with 30% less pressure..However I am trying to get an idea where the stock 250cc max out to give me a starting point....
I've seen plenty of guys running stock ecu and boost, Ive also seen more failures than I can remember. The main reason most get away with it is the stock ecu goes extremely rich up top anyway and have relative conservative timing for a naturally aspirated engine. In NA engines the top end power is improved greatly with a few degrees more timing and lots less fuel. Years ago I swapped out a set of stock 215cc to 250cc on a supercharged jetboat running 8psi. It had an intercooler with low intake temps. I was just able to supply enough fuel however I was over what I consider an acceptable duty cycle. Anything with slightly higher air temps they wouldn't have done the job. Running stock na engines on the road I'm getting reasonably high duty cycles at higher rpm however not too bothered due to the infrequent times they go there, on track engine I prefer larger injectors to keep duty cycles down as they spend lots of time at higher rpm. Theres more to consider than just the air flow ratio.
I know that AFRs are just 1 key to the puzzle. I blew up a 600hp 2jz with perfect A/R due to lack of timing retard.
May I ask what horspower numbers you were running at 8psi?
Also, in your experience, what caused the grenaded motors in the examples you mentioned? Lean condition? timing? Detonation? Or rod/piston failure?
At what horsepower level?
As I mentioned, I am going to use slightly larger injectors at 80% duty cycle to decrease fuel pressure and keep that margin of safety and meth injection to control detonation....and a larger turbo to decrease air temperatures at that flow. Obviously 8psi on a t72 generates less heat than 15psi on a td04. Hence my question, at what point did 250cc injectors hit 100% duty cycle. With that info, I can reverse calculate fuel requirements with FMU and larger injectors (theoretically...). thanks for you help
Sorry that job was years ago and I can't remember that much. Every now and again I come across photos of it when I'm looking for other stuff. Ive done so many different setups I can't remember lots of details these days. Maybe 25-30 boosted 1uz's. Every other one I have done I've used larger injectors.
All the failures have been other guys setups. Just had a guy that blew two motors before he decided aftermarket ECU was the answer then went cheap and the trans is now having issues as it wasn't setup correctly. Head gaskets is common with 100000km old gaskets,, pistons is common too either burnt away or smashed to bits. Too high intake temps is common with DET and mixture issues.
I don't do piggybacks very often. Instead opting to take fuel and timing control away from stock ecu and leave stock ecu doing trans. Easy and works well. Early ECU are pretty dumb. Fuel trim is primitive
I had run FMU 12:1 with turbo on my SC400 with boost at 6 psi for a long time without issue. My friend is running supercharger at 6 psi on his LS400 without issue. I'm an old time member here, got busy, so I didn't log on here for a long time.
The AEM from the Supra works perfectly. The only thing that I am not 100% satisfied is that after I insert the key in the ignition, I have to wait for about 10 seconds for the AEM to initialize, then I can start it.