Sizing of injectors.

[Graham]

On my 4.5L 350SL, I have the M117 engine. This engine uses Bosch 0280150036 injectors (blue) that apparently are rated at 485 cc/min at 3bar.

On a 3.5L 350SL, they have the M116 engine. This engine uses Bosch 0280150034 injectors (yellow) that are rated at 317 cc/min.

Info is from here http://www.injectorcleaning.co.uk/flow.htm

Do they mean 3bar gauge or absolute in that table??

The 3.5L Euro and 4.5L US spec engines apparently produced the same HP - 230HP SAE as it was defined at that time.

So why would they use injectors with different ratings?

Was there something else different about the engines?

Rail pressure is same, according to the manual.

I found the calculator at the bottom of this page

http://www.rceng.com/technical.aspx

It says that 227 cc/min would be enough.

This leads me to think that the yellow injectors may be more fuel efficient if they were used on the 4.5L engine ?

Confused by all of this

[Gurunutkins]

as with all of these graham it depends on who you believe. I have an old bosch book that I work with and tend to trust that, but its been wrong occasionally. a;lso the pressure standard for these is pretty much always 3 bars regulated at the rail

The 450sl runs 280 150 036 injectors generally rated at 495ml per hour and they work at 2 to 3% duty cycle for most of the time but at WOT they just dump gas into the engine.

my 350sl euro came with 280 1250 017 injectors rated at 377ml per hour and work at pretty much the same rate as the 036's in my 450sl.

I have put mustang 5l injectors rated at 19lbs (205ml / hour) into a 450sl and they work very well and very economically with very little noticeable change in power until you get right up to the top end.

I have both my 450 and 350 running on megasquirt now so can actually watch the duty cycle change if I were to drive with the laptop open on the passenger seat which I would never do right!

what I do see is that when you open these engine up and dump that much gas into the engine unless you are perfectly set up and everything is working exceptionally well the gas just tends to dampen the spark and you get a pretty turbid response. This winter i am going to convert my 450 to EDIS (electronic distributor less ignition system). hopefully with the 2 coil packs with each plug getting its own feed (running wasted spark) I will be able to capture the great potential these engines have for some sterling horsepower with very little machanical modification.

hope that helps some and just for interest my 74 450sl is now running very well with tons of power at 18mpg (us gallon) and my 73 euro 350sl at 20 -21 mpg and feels more powerful than my 450.

cheers
barri

[Graham]

Originally Posted by Gurunutkins

as with all of these graham it depends on who you believe. I have an old bosch book that I work with and tend to trust that, but its been wrong occasionally. a;lso the pressure standard for these is pretty much always 3 bars regulated at the rail

The 450sl runs 280 150 036 injectors generally rated at 495ml per hour and they work at 2 to 3% duty cycle for most of the time but at WOT they just dump gas into the engine.

my 350sl euro came with 280 1250 017 injectors rated at 377ml per hour and work at pretty much the same rate as the 036's in my 450sl.

I have put mustang 5l injectors rated at 19lbs (205ml / hour) into a 450sl and they work very well and very economically with very little noticeable change in power until you get right up to the top end.

I have both my 450 and 350 running on megasquirt now so can actually watch the duty cycle change if I were to drive with the laptop open on the passenger seat which I would never do right!

what I do see is that when you open these engine up and dump that much gas into the engine unless you are perfectly set up and everything is working exceptionally well the gas just tends to dampen the spark and you get a pretty turbid response. This winter i am going to convert my 450 to EDIS (electronic distributor less ignition system). hopefully with the 2 coil packs with each plug getting its own feed (running wasted spark) I will be able to capture the great potential these engines have for some sterling horsepower with very little machanical modification.

hope that helps some and just for interest my 74 450sl is now running very well with tons of power at 18mpg (us gallon) and my 73 euro 350sl at 20 -21 mpg and feels more powerful than my 450.

cheers
barri

When you say the pressure standard is 3bar. My question was - Is that a gauge pressure - ie 43.2 PSIG or an abolute pressure 43.2 PSIA (28.4 psig)? The D-Jet SL rail is supposed to be at 2bar 28.4 psig.

I have been reading your Megasquirt posts - Sounds like a good mod, but I suspect, like me and my projects, you are just doing it because you need a challenge!

I was looking for a low cost CO meter or A/F meter so I can adjust the MPS (I bumped up my fuel pressure to stop vaporizatio in Spring & Fall when we get winter gas containing butane, ethanol and whathaveyou. It solved the problem, but I need to adjust the MPS & idle mixture. In my search, I came across this site:

http://www.sdsefi.com/

Thought you may be interested.

[Gurunutkins]

[QUOTE=Graham;2029475]When you say the pressure standard is 3bar. My question was - Is that a gauge pressure - ie 43.2 PSIG or an abolute pressure 43.2 PSIA (28.4 psig)? The D-Jet SL rail is supposed to be at 2bar 28.4 psig.

I have been reading your Megasquirt posts - Sounds like a good mod, but I suspect, like me and my projects, you are just doing it because you need a challenge!

Thanks for the site Graham, always does to keep current but I already have all of the stuff ready to do the conversion. see the end of this thread finally my 450sl runs on megasquirt

The pressure at the rail for the quoted bosch flow rates is gauge not absolute. so just to be certain its 3 bars on the gauge with no correction for atmospheric pressure so a full 43.2psi.

with our cars running at 28 - 30 psi I often think its because the injectors are oversize for normal running and the only way they could get the duty cycle of the injector up was to run the rail at lower pressure. When you have your test rig running have a look at the spray pattern at 28 psi versus 38 to 40psi, you can actually see the difference in atomisation. running mine on the megasquirt I run them at 32 psi on an even shorter duty cycle but I can only do 2 alternating squirts per cycle rather than the 4 I would prefer as the duty cycle is so short and there is almost a millisecond for solenoid movement (latency) that if I shorten it any more I wont have time to physically move the solenoid. definitely time to start trying smaller injectors
cheers
barri