View Full Version : injectors Ken

08-19-2005, 01:36 AM
Tunning a GN on the dyno last night. The MSD 50's are going to 115% duty cycle and the car is going lean on the top end
22# of boost using a PT61, 23 degress of timming, no knock, extender chip, LS1 MAF,hotwire kit, walbro 255
fuel pressure was set at 45, then tried - 50 psi.
I got the a/f down to 13.8 " turning the Tplus full max" but need it lower. do you think the motron 65# will get it there or do i need 72# ?
The reason im asking, if you think the 65#'s will get it there, then i dont need to send the ecm off for the low Z mod to run the 72's

PS it made 389 HP 422 TQ on pump gas with a SMC kit...but still on the lean side

08-19-2005, 02:46 AM
Mototron 60/65 # injectors should be plenty for your combo. A car I set up went 11.0 (that's nearly 600 HP) with MSD 50's, a single XP pump, and TE54 turbo. I ended up leaning out and popping the head gaskets, but after many runs. (It has larger injectors and dual pumps now.)

08-19-2005, 10:44 AM
Problem with the 50s is that they don't like a lot of rail pressure and get erratic at higher duty cycles. I also believe that they are rated at 100% static flow to get 50#s?

The 60/65#s are rated at 80% DC at 43.5 psi and can operate with up to 5 BAR differential (and there are some guys out there running 7 BAR in some turbo motorcycles). THey are very linear in output as the fuel pressure goes up, so they will deliver up to 84#/hr at 5 BAR and stay linear.

I made 680 HP on my motor (on the dyno) PIG rich (10:1 AFR up top) with rail fuel pressure set at 50 psi. Obviously enough fuel for more once I lean it out (figure probably somewhere around 700 HP).

The 60#/65# are very easy to control at idle, 30 degree spray cone, have a linear response, are easy on the ECU drivers (currentwise), and don't get really erratic when the duty cycle creeps up.

BTW, sorry if it sounds like a commercial ... I don't have any vested interest in selling injectors, even though MotoTron makes them. The money goes in their pocket, not mine ... it's just they are kick ass pieces! :D

I've seen them run on all sorts of stuff (blown LS1s, Ford mod motors, Buicks, big Chebbies, lots of marine stuff) and they are consistently great performers for such a large flow rate.

08-19-2005, 12:40 PM
thanks for the info, i even tried the fuel pressure at 60-63 psi "set when the car was running" trying to get the a/f down , and then after i shut it down it wouldnt even start.. I had to turn the fuel pressure back down to 45, so it would start.
Anyhow, i told him to get me some 60-65 motrons and we will be heading back for more tunning.

PS the alky system we gained 65 HP