17lb injectors worth the swap for mpgs

[Click]

I have a 89 325i and have a set of 17lb injectors as I plan on getting a markd chip in the future. From what I've found im pretty sure I can run 17lb injectors with everything else stock. I know the 17lb/hr are 4 pintle design and are said to be better at atomization where the stock are 1 pintle design. Would there be a mpg increase if I swapped them in before I got the chip?

[shiboujin]

What's stock lb rate? like 14?

So 3lb/hr more but better atomization? You expect better fuel economy? lulz. If it was the same lb/hr rating but better atomization, I would expect a barely noticeable gain in mpg. But shoving MORE fuel in without telling the ECU will always net you worse MPG.

Short answer, no.

[nando]

I doubt it will increase your MPG. better make sure your O2 sensor is new and working, too.

[Click]

What's stock lb rate? like 14?

So 3lb/hr more but better atomization? You expect better fuel economy? lulz. If it was the same lb/hr rating but better atomization, I would expect a barely noticeable gain in mpg. But shoving MORE fuel in without telling the ECU will always net you worse MPG.

Short answer, no.

Stock injectors are 14.5 lb/hr. I'd figure the ecu will adapt to the larger injectors w/ a shorter duty cycle. Of course there is a limit to the amount an ecu can adjust, throwing 25 lb injectors would drown the engine, but I figure a 2.5 lb/hr difference is only like a 17% increase and should be able to cope. I would bet some people are driving around with heavily clogged injectors that would net 12 lb/hr or less and the ecu has adapted to those conditions.

Then in theory, after the ecu has adjusted itself, you would be squirting the stoichiometric amount of fuel through a better atomisation nozzle which in theory would be a smaller amount due to the better atomisation. And thus higher MPG has been achieved.

[nando]

the ECU can and does adjust fuel trim based on O2 feedback. there's a short term trim and a long term trim. But you need to be certain your O2 sensor is working properly and there are limits to how much it will trim.

I ran 19# injectors for years with the stock ECU - worked fine, no problems with CELs or running too rich.

the biggest side effect is your MPG gauge will read high by the % difference in your injector size.

[shiboujin]

I should do a proper response instead of something smart.

The 80s tech of the ECU is not smart enough to accommodate for very much. Clogged injectors doesn't really change flow that much (not down to 12 anywho). The atomization will suffer but the engine is efficient enough to burn it.

Long story short, the stock ECU isn't very smart.

[nando]

Listen, i did the injector swap thing before you were even old enough to know what an e30 was.

The ecu can and does support long term O2 feedback.

[shiboujin]

proof?

[nando]

I have tons of docs on early motronic systems. Even toyota was doing long term trims in the 80s.

[Click]

[bmwguy325is]

:stupid:

Listen, i did the injector swap thing before you were even old enough to know what an e30 was.

The ecu can and does support long term O2 feedback.

I have tons of docs on early motronic systems. Even toyota was doing long term trims in the 80s.

[blefevre]

I went from stock injectors with Dinan chip, to M50 injectors with Dinan chip, to M50 injectors with MarkD chip.

I saw a 0.5-1mpg increase with the M50 injectors. BUT, I had them cleaned professionally so I am positive that is what was the cause of the increase.

Don't expect anything.

[IminDiegoTriick]

Would you need to run 91 octane? just curious :P

[bmwguy325is]

Would you need to run 91 octane? just curious :P

That has more to do with timing advance than injectors. However running premium nets you better millage LOL Not by muxh but better than a tornado intake kit

[shiboujin]

I have tons of docs on early motronic systems. Even toyota was doing long term trims in the 80s.

I have a few books on motronics systems too. They will do long term changes but only a VERY minimal amount. They weren't designed to have different sized injectors put in. Find me real proof and I'll concede.

And? I know it does O2 corrections. You're dealing with a terrible narrow band though. It can only trim so much.