baronbob

I have a 7.4MPI with a 5PSI M1 Procharger, Merlin heads, Gill exhaust, Mag internals, roller rockers, STOCK INJECTORS and detonation problems. Mark @ Performance is a master and he warned me that my injectors might not provide enough flow to feed the 2.25 inch intakes. He re-programed my ECU for 90% duty cycle @ WOT and it worked good for most of the summer, however I recently detonated @ sea level and now I am re-building plus changing to bigger injectors. The motor seemed to run ok @ WOT on Lake Tahoe (6229msl). Sea level WOT called for more fuel and I just could not get enough through the stock injectors and leaned out causing the detonation. The question is what flow do I have in the stock injectors and what should I go to for correct delivery @ sea level? I also have the Procharger fuel system for a 7.4 MPI (stock pump fed by the red in-line vein pump). I do see 60PSI with the stock injectors while adjusting regulation down to 54#s @ WOT. Should I modify delivery pumps as well? I will have to re-map. Should I get an on board tuner person? Are their any on the west coast?

RBeyer

Talk to Arizna Speed and Marine (a tech not a counter guy) and they can set you up with injectors and the remap make sure you get their o-rings for the injectors. I have a similar setup, fuel pressure at idle is 36#'s and rises about 80#'s at WOT.

dagah2x

Im running the 50lb injectors with an M1 on a 502. They came from Arizona marine. Also an aeromotive fuel pump and regulator with larger supply lines. Call them and ask about a 2 bar map sensor also. My computer was done by them and its a little rich, I plan to have it remapped on the water, its the only way to get it right....

Mine as well do it the right way now and not have to worry....

RBeyer

A little rich is a good thing. It beats the alternative. I'd rather clean a little black than Kaboom!!!!

bobl

If memory serves me correctly the stock 7.4MPI injectors are something like 24 lbs. It's no wonder you leaned it out!

baronbob

I would guess the HP to be 500+. The fuel delivery is stock Merc, I would guess 5/16". The knock sensors went off twice and the first caused #6 compression to go from 130#s to 90 and then declined over the summer. After the second knock sensor happening I believe I can see piston damage to #6. I have fuel cool does that have to change also?

Strip Poker 388

iTrader: (6)

I would ck with Mark at Precision Marine .You normaly do not want to go over 80% duty cycle,bandaids usally will get ya introuble ,just think when your over the 80% and a fuel pump gets a little week, voltage drop or fuel filter gets cloged a little ,or a bad batch of fuel not much fail safe there.