M50B20 injectors in M20b25?

[Andy325i]

I heard/ read that you can use M50B20 injectors in an M20B25 as they have similar flow rate and have a better spay pattern.

Has anyone done this or shed any light on it?


Many thanx

Andy

[Steven320]

there is a little diverence idd. i use them right now on my m10b18, and before on my m20b20 runs perfect. but if i was you use the m50/m52b25 little bigger

[Andy325i]

Hi Steven, thanks for the reply I think M50b25 injectors would over fuel? Do you know any of the flow rates for the above injectors? Wondering what fuel pressures the M20/M50 run?

Many thanx

Andy

[Steven320]

hee, no the m50b25 will be fine, i mean you are running a m20b25 right so the engines have the same size. and your car is running on 3 bar of fuel pressure and i think that the M50b25 does it aswell. dont worry you will be fine but make sure that those injectors are clean or let them clean for you.

Steven

[Quaser]

I wouldn't use them tbh - this was done by zoners many moons ago and the conclusion was that the m50 injectors have a 4 point spray pattern where as the m20 ones are straight down and the m50 ones would cause bore wash as it didn't send the fuel in the same direction as the m20 ones (or something like that!)

[HairyScreech]

The flow rate of the m50b25 injectors is higher. IIRC the m50b20 ones actually have the same flow rate as the m20b25 items.

Beware though, changing the flow rate WILL change the air:fuel ratio at all points in the map.

Basically I wouldn't advise change for the sake of change.


Edit- Got to pick up on the bore wash thing.

The whole thing about the m50 injectors causing bore wash because of the spray pattern is bollocks. I made a long post on here a while back that I am sure would come up with a search for bore wash.
The reason for the bore wash is the use of fuel injectors with higher flow rates with out the system being calibrated for these higher flow rates.

Bore wash is caused by having WAY too much fuel in the cylinder that is liquid and diluting the oil film on the bore reducing it's ability to be a lubricant.

Any fuel that is on the port walls will be atomised to safe levels by the effect of being pulled past the valve, the heat of the chamber and the turbulence of the squish effect.

Provided the fuel was metered to the correct ratio you could have it drip in the inlet under gravity and let the physics do the rest and still not get bore wash (this method is also know as a carb).

[HairyScreech]

Found it.

http://www.e30zone.net/modules.php?name ... =bore+wash

Tl;Dr, pretty much a longer version of the above, might do an edit as I am sure there is more I could add now.

[Steven320]

never got a problem with my m20b20 and he wasnt drinking fuel either so why you dont just try and find out by your self. you can read your spark plugs if you whant to know.

[HairyScreech]

You were probably still within a reasonable AF ratio, if they were second hand injectors then they may well have been under performing as well so probably were not that far out.

It's one of those things that come under "if it isn't broke, don't fix it" if your current injectors are big enough to fuel the engine then your not going to gain anything. The low CR of the m20 negates any real chance of an economy gain from the spray pattern, its kind of like the Michelin man wearing light shoes to help him run faster, there is bigger issues to fix first.

btw - not saying m50b20 injectors are not fine in an m20b20, they may well be, it's just not really the correct thing to do.

[Andy325i]

Thanx guys, would it be worth getting the originals cleaned/ refurbished? It goes well enough, but is hard to start, esp from hot/ warm and I noticed yesterday it was near impossible to start when I had the front end up on the jack (Sorry little off topic!)

Edited to add: Its done 199,993 miles lol

[Gunni]

I wouldn't use them tbh - this was done by zoners many moons ago and the conclusion was that the m50 injectors have a 4 point spray pattern where as the m20 ones are straight down and the m50 ones would cause bore wash as it didn't send the fuel in the same direction as the m20 ones (or something like that!)

Bore wash no,

To much port wetting , pretty certain.

[Steven320]

i got your point simon;)

check your sensor mate.
if you have a multimeter, you can check by manual if its within limits and shut be ok. but you can better start with the tryangel of combustion

ignition
fuel
oxygen

and if that is al correct you can go further with electronics and try to work out how the ecu work makes a lot easyer.

[DmcL]

i havent played with M50B20 injectors but i can say that M50B25 injectors will drop straight into an M20B25. the M50B25 runs at 3.5 bar fuel pressure while the M20b25 runs at 3 bar. i worked it out some time ago and with the fuel pressure difference the M50 injectors end up only flowing something like 1lb/hr more than the M20 injectors. i chucked a set straight into my own M20B25 some time ago and it ran fine on them, mind you i havent run a standard fuel map since like 2009 but if memory serves i was pushing a little more fuel at full throttle than the standard maps prior to throwing in the M50 injectors.

as said it will run a hair more rich but should not be so much as to cause problems. in an ideal situation you would want to stick a wideband on the car and tune the fuel maps to get AFR's back where they should be but not everyone has that capability. for a straight drop it they are very good. if the M50B20 injectors do indeed flow the same as M20B25 injectors including the difference in fuel pressure between the two engines then the M50B20 ones would be the ones to go for of the two.

[reggid]

I wouldn't use them tbh - this was done by zoners many moons ago and the conclusion was that the m50 injectors have a 4 point spray pattern where as the m20 ones are straight down and the m50 ones would cause bore wash as it didn't send the fuel in the same direction as the m20 ones (or something like that!)

Bore wash no,

To much port wetting , pretty certain.

so what is the best spray pattern for the M20 with stock fuel injector location spraying at the back of the valve?
should a narrower pattern be chosen to avoid wetting the walls?

[steve_k]

Has anyone thought about using the 19lb injectors from the ford mustang?? Had a look online & there's a few threads on the likes of bimmerforums etc where folk have used them to good effect with either a chip or dyno session to set it up correctly,

Just a thought really as I'm thinking of going for these on my 2.7 build (pretty hi spec but keeping quiet at the no)
So any thoughts on these?

[jmc330i]

I've seen mention of using Mustang injectors on the US forums, but I thought it was for the M42.

[steve_k]

I've seen mention of using Mustang injectors on the US forums, but I thought it was for the M42.

I know what you mean Jim, but a lot of them have been used on m20's as well as m30 arm's.

[jmc330i]

The M42 uses the same injectors as the 3.0 and 3.5 M30, not sure how they'd work in an M20.

I've also read some guys on the US forums saying the Mustang injectors aren't a brilliant fit in the M42, which could cause leaks - not ideal near the fuel rail

[steve_k]

The M42 uses the same injectors as the 3.0 and 3.5 M30, not sure how they'd work in an M20.

I've also read some guys on the US forums saying the Mustang injectors aren't a brilliant fit in the M42, which could cause leaks - not ideal near the fuel rail

Very true, could be worth looking into though as I'm sure there will be a work round any leaks,