Carb v EFI

[outlaw]

Gidday schofield, I have a j73 350 lt4 chev 753 unit running a a big carb, I was skiing and towing a biscuit at the lakes doing average 3500 rpm for about two and a half hours I used 26 litres of fuel, my engine also runs smooth, I think this was pretty good hope this helps. Ps. there still making fuel!

[bbs 540]

In my experience regardless of carb or injection for a 350 to last under load your air fuel mixtures have to be fairly rich due to constant heavy load at lowish RPM. You have to compare a jetboat engine to a vehicle towing a heavy trailer up a steep hill, it is under high stress load all the time. With this in mind to stop things from melting you need to run around 6% fuel wastage (rich) or if you have an oxygen sensor to check your mixtures .82 Lambda. This is for long term longevity 1000hrs+. So regardless of what induction system you run you need to run the same mixture under load. Where fuel injection can save you is it can meter your idle and off load areas more effciently than a carb. If you are running a 350 it's pretty hard to go past a victor jnr  intake and a 600 vac/secondary holley for all round usage.

[sambo]

All done to meet emissions standards over time, and most done with the O2 sensor in a closed loop circuit. First thing that gets done in a boat is to a$$hole the O2 sensor and run an open loop circuit. Besides, the ECU mostly ignores the O2 sensor after about 50% throttle anyway.

A well tuned and maintained carb will make as much power and be as efficent as an injected system, particuarly at the throttle percentages we run in a boat...

Makes you wonder why GM LS2's and LS3's make more power out of the crate with a carb than with the EFI setup.
EFI LS2 = 400hp, (Carb) LS364 = 440hp
EFI LS3 = 480hp, (Carb) LS376 = 515hp

 The only reason  the carbed engines here have  more power is just ecu tuning,   every efi engine  from a factory is never  brought out with full power.  they tune them with  reliability in mind .

[PM]

 

The carb'ed engines still come with a GM 3 year warranty. Not tuned for reliability?

The original statement was that an EFI setup would make more power, now tuning is important?

[Brendan]

as far as i am concerned and alot of people would agree, a carb an dissy does a bloody good job and is easy to fix, keep it simple is how i see it. if you do the research you will find that EFI runs an engine as lean as it can to give economy but when you go to WOT the system opens all the injectors to full flow and pours the fuel in my 

[Anarchy]

GM have hoter cams in the carbed LS motors and it all comes to tune .but what kiwi bloke can fix a over thought sistem with a screwdriver and a cresent
go carb go hard get home 

[Brendan]

GM have hoter cams in the carbed LS motors and it all comes to tune .but what kiwi bloke can fix a over thought sistem with a screwdriver and a cresent
go carb go hard get home 

yeah right on. 

[JR]

GM have hoter cams in the carbed LS motors and it all comes to tune .but what kiwi bloke can fix a over thought sistem with a screwdriver and a cresent
go carb go hard get home 

Is everyone overlooking some thing.. If it a jet boat and it gets you up and down the river/lake or where ever that is a good thing..
I have always had a carb/dizzy motor in my boats up till now. Have a Link ecu and if it all go's tits up it will put it in to limp mode... Have had it do that once... When't from 8cyl down to 4cyl and we limped home... Cheers JR

[wrongway2]

(773 - 15 foot ali boat ) I replaced a (carbed) Holden Red 308 V8 with a LS1.  Fuel saving is approx 30% in favour of the LS1 for the same useage.

[bbs 540]

Interesting the 308 vs LS1 I found the same thing when you change from a small motor to a larger cu motor (350 to 383) that you use less fuel. Big motor does the job easier than a small one working it's heart out hence less fuel used. Here's another one,350 chev/212 3.4 impeller 600 holley WOT 3800rpm. 390 Holley 3700 rpm Throttle response immediate, starting and midrange performance far better. Fuel economy about the same but much better to drive. Most people tend to go too large with their carbs which can make them soggy in the midrange (where we all use them 95% of the time) just to achieve that last 50 or 100 rpm more than their mates boat pulls. Most of the time we want a boat that starts well and responds immediately when we get ourselves in the crap and doesn't leave the transom covered in black unburnt fuel after a run. Listen to what people say take an average, then take 150CFM off the size of they recommend and it will go well.

[mohawk]

(773 - 15 foot ali boat ) I replaced a (carbed) Holden Red 308 V8 with a LS1.  Fuel saving is approx 30% in favour of the LS1 for the same useage.

Some of that could be the weight saving or the tune you were running . Not so much EFI over carb.
As much as I like carbs , Im the first to admit the EFI engines are generaly lighter and more efficiant in design .