DIY injector cleaning?

[tim eh?]

I have a set of injectors from an m60 I'm thinking of swapping into my motor in the spring. They look great (waaay nicer than mine) but if I can do anything to them before I put them in I'd appreciate the advice.

[whiskychaser]

Dont you have to consider stuff like flow rates, operating pressure etc? Even the 'standard' injectors have different sized holes in the pintels dont they?
(Yeah I should do more research but I'm dangerously close to becoming a nerd anyway)

[ss2115]

I have a set of injectors from an m60 I'm thinking of swapping into my motor in the spring. They look great (waaay nicer than mine) but if I can do anything to them before I put them in I'd appreciate the advice.

If they are a similar specification to the correct OEM ones and mechanically fit of course, then its not a problem to put them in because any small difference in specification the ECU along with the O2 sensor will adjust for them.
However, if they are quite a bit out of spec then you'll regret the changeover - if they are too small a flow you'll lean out at high revs and have poor performance and possible engine damage, and if they are too large you'll have poor idle and low pickup.

Best idea for getting them ready is to give them to a specialist for ultrasonic cleaning and flow testing. He'll make sure they all flow the same as well.

[whiskychaser]

Best idea for getting them ready is to give them to a specialist for ultrasonic cleaning and flow testing. He'll make sure they all flow the same as well.

Now that is technical language I do understand

[tim eh?]

ok thanks guys i was told these are ~19lb injectors vs ~17.5lb stock m20 and would be a good upgrade for my car... can someone suggest where I could read up on this?

bentley says for fuel pressure
m20= 3.0 bar
m60= 3.5 bar

[ss2115]

ok thanks guys i was told these are ~19lb injectors vs ~17.5lb stock m20 and would be a good upgrade for my car... can someone suggest where I could read up on this?

bentley says for fuel pressure
m20= 3.0 bar
m60= 3.5 bar

Hi again Tim eh?

17 to 19lbs will not be any difficulty to swap in. The difference is small and as noted previously, the O2 sensor will see a slightly richer mixture from the slightly larger injectors and tell the ECU to shorten the time intervals it opens the injector and so bring the fuel mixture back to the correct ratio.

This brings up the big BS about bigger injectors being upgrades - they are only effective if you have done other work to the car so that the engine demands more fuel - then and only then is a larger fuel injector of any benefit as it can flow more. This is usually at high revs where smaller injectors cannot pass enough fuel to maintain a safe and performance orientated mixture ratio, and its of benefit to engines that have been turbo'd or supercharged after they left the factory (ie: if the manufactuer has designed the car with charging, then he's already designed the fuel system to cope with all eventualities).

Under all other circumstances (such as yourself), larger injectors will be adjusted by the ECU to maintain the original fuel ratio the manufacturer intended and make no difference to performance.
In fact, as previously stated, a well oversized injector can actually give a poor idle and off line performance and possibly poor starting due to its poor ability to atomise the fuel at very short "on" intervals controlled by the ECU.
*You won't have that problem - 17 to 19 lbs is a small change.

In regards to the Bar ratings you have quoted, these are not actually to do with the injectors, but the fuel pump pressure - the amount of pressure that is in the fuel line/fuel rail that feeds the injectors.
Again - if you were making other performance changes to the engine, it might be of benefit to increase the fuel pressure to the injectors. It means the fuel moves along just that little bit quicker, and the main benefit is that the higher pressure through the injectors will atomise just that little better as well.

But once again, just increasing the fuel pressure alone (or with bigger injectors as well) will not be of any benefit at all to a mostly standard engine because if more fuel is pushed through the injector by a higher rated pump or higher adjusted fule pressure regulator, then the o2 sensor will detect a richer mixture and tell the ECU to shorten the injectors timing intervals anyway to bring it back to normal.

The fuel regulator makes sure that the fuel pressure from the pump is extremely constant so that the timing intervals for the injectors will be reliable to squirt the exact amount of fuel for every interval the ECU selects. If the engine is steady at 2,500rpm and the ECU is setting the timing of the injectors at x milliseconds, its because the pressure is constant and it knows from feedback from the O2 sensor that its the correct fuel ratio to maintain the forward speed under the load of the car, to be within the pollution laws, and to also be the least amount of fuel to maintain that speed for fuel economy.
But if the fuel pressure was up and down all over the place, the ECU cannot possibly react quickly enough to be constantly adjusting the injector timing to maintain a smooth engine speed.

So the pump usually pumps at a higher pressure than actually required (eg: 5 bar) and then the fuel regulator adjusts that pressure down to give a constant reliable 3 or 3.5 bar to the injectors.

Again, there is a lot of BS about installing an adjustable regulator (off eBay and some speed shops) will increase your engines performance even through the standard injectors. For all the same reasons explained above, its not true on a standard engine that isn't demanding more fuel because the O2 sensor will see a the richer fuel mixture by the higher pressure pushing more fuel through the injector, and it will tell the ECU to reduce its injector timing to bring the fuel mixture back to what the manufacture intended for that engine.

If you thought an engine could benefit by a richer mixture, there are other ways to do it such as fitting piggyback fuel computer or entirely replacing the engines ECU and there are little tricks like changing certain sensors to the ECU to "trick" it into thinking the engine needs more fuel than it really does. Most of these tricks fall around either making the ECU think the engine is still warming up and so it operates constantly under choke conditions, or fooling the ECU into thinking its really cold weather and the ECU will increase the fuel mixture to cope with cold air that is heavier and doesn't atomise the fuel mixture as well as hot air.

Hope this helps.
If your interested, I do have a book available written for people that want a basic understanding but don't need or want to be experts. It isn't illustrated yet. I wouldn't mind a review if you were interested.

[tim eh?]

Wow thanks for taking the time to write that. The main reason I want to do this is not so much for an upgrade but because I have this set already and I think the ones in the car are pretty much toast. However, once the 19s are in there maybe I could do something with the airflow to get some hp. I'd like to know they work first tho satus quo. I think I have grasped the basics, just not the specifics (ie what size what be too big... will it physically fit... how to clean... how to test)

Send me the book! I am reading lots of 'diy for dummies' these days maybe I am a good barometer . Maybe you should post it up - lots of people here...

[e34.535i.sport]

I have a set of injectors from an m60 I'm thinking of swapping into my motor in the spring. They look great (waaay nicer than mine) but if I can do anything to them before I put them in I'd appreciate the advice.

Good timing this! I've just posted a thread about having mine cleaned 'ultrasonically' - Only cost £60 for all six so might be worth you looking into to make sure they're tip top before you put them in?!

[e34.535i.sport]

Wow thanks for taking the time to write that. The main reason I want to do this is not so much for an upgrade but because I have this set already and I think the ones in the car are pretty much toast. However, once the 19s are in there maybe I could do something with the airflow to get some hp. I'd like to know they work first tho satus quo. I think I have grasped the basics, just not the specifics (ie what size what be too big... will it physically fit... how to clean... how to test)

Send me the book! I am reading lots of 'diy for dummies' these days maybe I am a good barometer . Maybe you should post it up - lots of people here...

I remember looking into this a bit myself - To see any reall impovement I think you would need to upgrade your fuel pressure reg also...

** Just spotted this has already been discussed