Injector upgrade - thoughts, please.

[ed_crouch]

Hi everyone.

The Chim 4.6 is getting a Megasquirt 3X ecu at the moment. We're not in a mood to map the ecu with old and probably cacked up injectors in it, and there are vicious rumours abound that next year the PAS pump might sprout a Rotrex badge.

I'm planning on putting Bosch green giant injectors on it - 453cc/min (more than enough!!), Bosch #0280155968. For a 9.35CR 4.6 they're obviously a little big at the moment, and the reduced pulsewidth will incur a proportionally greater deadtime, but equally they're not the crappy disc-type injectors it currently has that don't really atomise fuel. When its supercharged, they'll be just right.

Has anyone used any other commonly available injectors to give headroom to 350ish horsepower?

Thanks,

Ed.

[Jhonno]

Those injectors are far far too big for your needs... You will struggle to get idle and low down fueling right.

Cerb 4.2 injectors are good for 400bhp. So nicely spec'd for 350bhp.

I actually have a refurbished set for sale too..

[Classic Chim]

I don’t know about size but I have speed 6 injectors fitted to my 4.6 and my car runs superb from very low revs onwards if that helps.
My fuel economy is better and the car feels more urgent and crisp but that might have something to do with mapped fuel/ ignition via MBE Ecu.

[ed_crouch]

Thank you for your input. So the jolly green giant is about a 450cc injector.

Is the concern about low down running about excessive dead time vs injector PW or about ecu PW resolution?

The MS3 ecu has very fine resolution, but obvs can’t do anything about the dead time...

[Dougal9887]

Far too big. Not even in the ballpark.

[ed_crouch]

So the online calculators tell me that 350 - 375cc/min is about right.

I’ll have another look through the Bosch numbers!

[Jhonno]

ed_crouch said:

So the online calculators tell me that 350 - 375cc/min is about right.

I’ll have another look through the Bosch numbers!

350-375cc is also too big I think.. That's good for about 500bhp.

Edited by Jhonno on Saturday 8th June 00:20

[Jhonno]

The Cerb injectors I mentioned earlier for reference, are (278 iirc Creams), with a flow rate of 240cc/min @3bar (TVR's run 3.5), so about 260cc and they are good for 400bhp in an NA V8..

[cinquecento]

I am running those bosch green 968s in my Megasquirted Griff 500 whose power steering pump has already suffered from a rebadge. Whilst those injectors are a bit big for a n/a 4.6, I assume you'll be running std fuel pressure so that will help with duty cycle. To help running rich at idle, you can up the spark advance as this helped me pre SC days to get a smoother idle.

Interestingly too, I've had trouble finding accurate deadtime values.

If you choose smaller injectors you may well have to upgrade post Rotrex badge ... at 12psi running 3.0bar fuel pressure my duty cycle is over 90%..

[Jhonno]

What is your final bhp target?

[ed_crouch]

Probably 350-400. No higher than 400 as things go all wobbly in there without stronger underpants around the engine, and that’s bad.

For grins, I’ve been designing and making stuff for the MS install:

[ed_crouch]

[ed_crouch]

[ed_crouch]

[ed_crouch]

[ed_crouch]

Hmm, some upside down ones there...!

Crank and cam sensor assemblies. It looks possible to do a la Motronic/THOR and machine the front cover to pop a hall sensor in, but I don’t know whether 1) the engine has a THOR cam sprocket, and 2 whether the tooth pattern is something Megasquirt can work with... so I built a “notdistributor” with a hall sensor and a rotor with a flag on.

[Boosted LS1]

Jhonno said:

What is your final bhp target?

This.

[ed_crouch]

375bhp

[Belle427]

Just wondered if your interested in making some dizzy blank plugs, im interested in buying one and cant seem to find any!
Found one on the bay but the guy is having trouble with his machinist.

[Boosted LS1]

ed_crouch said:

375bhp

35 lb injectors will be plenty. That's 367 cc but you could probably use 315cc and play with fuel pressure.

Edited by Boosted LS1 on Saturday 8th June 19:33