Flow matched injectors?

[phord]

Does flow matched injectors increase mpg and longevity of the engine?

[dcb]

it probably helps efficiency a tiny bit, though I don't know how long they would stay matched in the field.

I can't see it having any appreciable affect on longevity.

[Jyden]

Not a bad idea - mached injectors will provide more even power, also if one injector are giving way too much fuel it will tend to rince the oilfilm off the wall of that cylinder causing more wear.

[Old Mechanic]

Most modern engines with OBD2 would pick up a significant difference in flow from one injector to another. It would show up as a difference in cylinder balance, which is measured passively by a sensor that measures the difference in acceleration and deceleration of the flywheel as the enigne is running.

The sensor counts the number of teeth in the flywheel ring gear, and provides a percentage of power developed between each cylinder as the engine is running.

regards
Mech

[DonR]

If each cylinder get the same amount of air it would probably be a good thing. But that rarely happens. Having each injector calibrated to its specific cylinder would probably be better use of resources.

[stonebreaker]

They won't increase longevity any, but buying a flow matched set of injectors in addition having a knife edge tune put on the engine's computer, will improve your mpg enough to measure.

The factory tune has slop built in to account for flow differences between injectors. Weirdly enough, it seems to be more cost-effective for the factory to spend millions developing things like cam phasing than to flow test every injector going into every car.

What the computer does, at least on GM cars, is during closed loop operation the computer adds or subtracts pulse width based on the feedback from the O2 sensors; when you floor it, however, the O2 sensors don't react fast enough to keep up with changing load conditions. So, the computer dumps what it thinks should be the right amount of fuel plus a little bit extra into the cylinders. If one of your injectors is somewhat lean compared to the others, this means the computer will add a bunch of fuel to ALL the cylinders to compensate, because it won't know WHICH injector is causing the problem.

So by getting a set of flow matched injectors, you eliminate the variance and thus the computer can run closer to its base calibration, always a good thing; and if you know a good tuner, he can change the car's programming to account for the more precise injectors.

I think DonR's concern about the uneven airflow is valid, but probably more important when racing. GM's V8 engines, in particular, because of their intake manifold shape, flow more air to the back cylinders than the front ones. Big power combinations like superchargers may even have to use bigger injectors on some of the cylinders to handle the increased air flow.

[Old Mechanic]

Any difference in air or fuel delivery would create cylinder imbalance, that could be measured with the built in cylinder balance capability of OBD 2.

Maybe it would be more cost effective to check the cylinder balance before you spend time and money on injector balancing, only to find they were already close enough that it would make no measurable difference in economy or emissions.

Ram air manifolds with plenums feeding individual runners feed cylinders very evenly especially on 4 cylinder engines.

I did have a performance build 2.0 liter Datsun truck engine in a 510 2 dr sedan. I first tried a Weber 36 DCOE with a manifold that fed 1 and 2 cylinders from the front barrel and 3 and 4 from the rear barrel.

The engine ran like crap, always rich on 2 and 3 and lean on 1 and 4. I bought a Cannon manifold built in Australia, which fed 1 and 3 with the front barrel and 2 and 4 with the rear barrel.

Problem solved. The firing order was 1-3-4-2 so the induction was occuring on two cylinders in a single 360 degree revolution ofthe crankshaft.

Pulling on 2, then immediately pulling on 1, then pulling on 3 and immediately pulling on 4 created the problem.

The Cannon manifold pulled on 2 with a 180 degree static pause then on 1, and the same for 3 and 4.

Plugs all burned equally clean and the idle was perfect. That car could run an SS Monte Carlo heads up to 65 MPH, and blow it away in the turns. Tom Wyatt build a 510 4 dr than outran a 427 Cobra on the Road Atlanta track. Mine was not turboed.

Fuel and air distribution issues have evolved greatly with modern emissions and port fuel injection. Under high load low speed operation (where best economy is achieved) the fuel and air distribution is most likely within 2% of exactly the same. That would not necessarily apply to high speed operation where air flow to individual cylinders would be compromised.

The mid 60s Chrysler Cross Flow ram manifolds in the 300 series were one solution to unequal air distribution.

regards
Mech