Throttle Body Injection

[Friz]

1986 Bayliner 20' Cuddy, 350 GM engine.<br />Having been a car guy and mechanic for a long time, I have developed quite a distaste for carbuerators. FI is the way to go. I think a TBI setup would be the easiest, such as Holly's ProJection. I've put this system on a few street motors, but nothing in the water.<br />Anyone done this? Pros, cons, ideas?

 

[Boomyal]

Re: Throttle Body Injection

They have a marine version Friz. It's as good as the street version but....$$$$$$!

 

[Dreamer1Q]

Re: Throttle Body Injection

I'm with Friz on this one....FI is more my cup of tea. Happen to have a link to said setup?

 

[craze1cars]

Re: Throttle Body Injection

http://store.summitracing.com/default.asp?target=partdetail.asp?part=HLY-700-21 <br /><br />Above is their simplest and cheapest kit that I feel would be more than adequate for most small block marine engines. It's a 2bbl, but 670 CFM is a LOT of flow...more than many 4 bbl OEM marine carbs. <br /><br />They also sell a much more expensive 4 bbl version that runs off their highly tunable Commander 950 computer unit that's been popular in auto racing, IMO it's probably capable of more CFM's than many motors need (capable of nearly 1,000 CFM if I'm not mistaken) unless you have a heavily modified big block. Do some internet searches if you're interested in that one. Lots of places sell 'em.

 

[TilliamWe]

Re: Throttle Body Injection

I know next to nothing about Holley's system, and I am no ASE certified mechanic... but I know from 25 years of practical boating, that small block chevies do not need a ton of carburation. We put a Holley 750 double pumper on a great running 1983 260 (350 chevy) and it did NOTHING for performance.<br />So I totally agree with craze that 2bl system at at 670CFM is plenty for your engine. Best of luck!

 

[Boomyal]

Re: Throttle Body Injection

A while ago I did some research on these TBI units. There seemed to be a lot of confusion on what was available for marine use from Holley. The last I was able to come up with was that Holley had raised the price into the high teens. <br /><br />I'm glad to see this link for $879.95. It puts it back in the ballpark to consider. It's definitely superior to carburation. I'd like to see some programming instructions for it.

 

[rbezdon]

Re: Throttle Body Injection

350 cubic inches is about .20 cubic feet. Therefor at 4800 rpm, and with an intake stroke every other cycle, a 350 cubic Inch engine can consume .2 x 2400 cubic feet of air or 486 cubic feet per minute. That is assuming 0 vacuum at WOT rpm (perfect air processing) which is impossible as the carb wont function efficiently so there is 3 or 4 inches of vacuum at WOT so the engine will actually only be able to process most of the 486, not all. Placing a carb or TBI airhorn cabable of passing more for a SBC in marine applications where RPM is typically limited to below 5000 is not worth the investment. The engine simply can not process more air that its cubic inches and rpm dictate (unless you add something like a super charger or turbo). On top of this you have to insure the exhaust system can release all that air and the typical back pressures of a through prop sytem will add a bit of back pressure to boot. 600 CFM is more than enough.

 

[Boomyal]

Re: Throttle Body Injection

yeah but vatter, there are so many other attributes of FI that make it worthy of consideration, such as:<br />ease of starting<br />better warm up<br />quicker throttle response<br />more precision fuel metering resulting in better fuel economy

 

[rbezdon]

Re: Throttle Body Injection

I agree with that Boom, my point is why try to over kill the thing with some monster system when the engine cant even process every thing the 2BBL can give it. I would love to convert to Fuel Injection of I had the budget. Of course, I would get the full MPI version instead of the TBI so I could get the performance increases as well as the operating and maintenance conveniences.

 

[Dunaruna]

Re: Throttle Body Injection

Originally posted by Boomyal:<br /> yeah but vatter, there are so many other attributes of FI that make it worthy of consideration, such as:<br />ease of starting<br />better warm up<br />quicker throttle response<br />more precision fuel metering resulting in better fuel economy

and much better atomisation

 

[Friz]

Re: Throttle Body Injection

Vatter, you are right about how much air one of these motors can use. The typical Quadrajunk carb is a 640. Holly's most popular models for stock or midly modified small blocks are 600 square bore and the 650 spread bore carbs. These run fine on a stock 350 so the 670 2 bbl TBI will work fine. having been a grease monkey most of my life, I have installed a few ProJection systems on street cars. They work real well. I was just curious whether anyone here had used one in a marine application.<br />It's not the performance of FI that I'm looking for, it's primarily ease of maintenance and a small part better economy. I HATE working on carbs!