Injector sizing

[Kquaine]

Has anybody changed the injector to a smaller size to save lower the fuel burn rate?

[Bob Bradley]

You'll achieve the same result by pulling back the throttles. And, you'll still have the hp there if you need it. Right now I'm helping my daughter and son in law put the correct injectors back into their 671ti engines to fix the problem caused by the prior owner doing the same thing you are suggesting. The smaller injectors are preventing them from hitting their top rpm under a load, and the boat has trouble getting up on plane. I'd strongly recommend against the move

[Captain Ralph]

Has anybody changed the injector to a smaller size to save lower the fuel burn rate?

You'll achieve the same result by pulling back the throttles. And, you'll still have the hp there if you need it. I'd strongly recommend against the move

The same horse power is required to move the hull at a same speed.
Horse power requires fuel.
The only thing you would change is top end operation.

Change in operation offers better results.
Changing the throttles to a slower pace does the job better.

I also strongly recommend against the move.

BTW; I'm looking at the next size up in injector size.

[Avenger]

Isn't there an FAQ about this subject? If there isn't , we need one. Seems like everyone who can't use the search function has to ask this question.

[Timeless72]

Would be cool if a chart did exist for Detroits. Next step up in size for performance gains, if even worth doing. Seems to come up a lot.

[Captain Ralph]

Would be cool if a chart did exist for Detroits. Next step up in size for performance gains, if even worth doing. Seems to come up a lot.

I have notes listing the HP & Injectors on the DDC engines. Mostly 12V71**s.

But it is not just injectors on any ole Detroit; #1 concern when messing with injectors on a turbo charged engine, you sometimes have to change the turbos also. That air / fuel ratio thing.

There can be also, cam shaft timing, blower ratios and by-pass blowers.

But wait, there's more; Inter-cooling, After-cooling and on some models both (TIAB)

Always stay stock when you can. Just pull the throttles back.

My problem, tired of slowing down when crawling up the back of a swell when I need to be moving.
It is rare when this happens since we mostly operate in LSD mode but some times we get chased out of the ocean or encounter an inlet at the wrong time, could use some extra ponies.

[jim rosenthal]

There probably WAS a chart of injector sizes and performance figures at some point when companies like J&T and Stewart & Stephenson were marinizing Detroit themselves and selling them as OEM engines. The one company I know of which have always been DD dealers and have been around forever is Western Branch Diesel in Tidewater, VA. If anyone would have that sort of information, they would, if they are still around. They are either in Chesapeake or Portsmouth, I think, can't recall which.

[bostonhatteras]

my 871N engines went from N70 to N80. no smoke or haze on horizon and no soot on transom. should've done N90.

[Captain Ralph]

my 871N engines went from N70 to N80. no smoke or haze on horizon and no soot on transom. should've done N90.

On Naturals (non-turbo), The compression ratio starts taller and you can adjust injectors a little easier.
On a pair of fresh 6-71s, we went from N-60 to N-90s.
No more slowing down crawling over swells.
Full of people and dive gear, you could drive that boat straight up a wall.
We were going to ad pitch into the wheels but never got to it before it sold.

[bostonhatteras]

On Naturals (non-turbo), The compression ratio starts taller and you can adjust injectors a little easier.
On a pair of fresh 6-71s, we went from N-60 to N-90s.
No more slowing down crawling over swells.
Full of people and dive gear, you could drive that boat straight up a wall.
We were going to ad pitch into the wheels but never got to it before it sold.

I would definitely need to add pitch if I had gone with 90s