Exhaust throttle

[Atious]

Can someone explain how an exhaust throttle is used, how it works? I have never used one and have an OPS .67 with an exhaust throttle.

 

[Twin_k90]

basically they shut off the exhaust flow and choke the engine, they work great, better throttle response and easier to to get a mixture,

problem is they are very very very very very messy, they will leak oil and stuff all over your boat!

Dale

 

[Atious]

So do you use a servo for thottle on both carb and exhaust or just set the carb wide open and control flow via exhaust throttle? How do you set it up?

 

[TimD]

The exhaust throttle is activated by your throttle servo. You leave the carb wide open or better yet, replace the carb with a venturi.

I have heard of someone using a working carb and the exhaust throttle together. Sounds to me like something that overcomplicates the boat too much tho....

Tim.

 

[EatMyShortsRacing]

I had a CMB 67 with exhaust throttle and carb linked...

Didnt see the point....

EMS Racing

 

[Atious]

OK so heres my more important question, I'm long into gassers but have only recently gotten into nitro boating. I'm not too concerned about the mess of an exhaust throttle as I am meticulate about cleaning my stuff after use anyway. Which setup would be the better to begin with? Run a carb w/o exhaust throttle or exhaust throttle and venturi? I'm not going to be in any competition but I've gotten bored with the comparably slow speeds of gasoline. Even my new zenoah from B+H hanson aint enough, I want to scream.

 

[Propjockey]

You wanna scream? You want exhaust throttle! ;D

 

[Hammerhead]

I have used exhaust throttle with an OPS .45. It was really difficult to get a good needle on the Venturi, and when I thought I had it, it was only good at full throttle.

If you have a good pipe, and a good carb, I would just go with it.

If you want a good exhaust throttle, talk to Dale. At Kingcraft. They are very well machined.

Hammer

 

[Don Templeton]

I'm not really up to date but I did race a 67 OPS with exhaust throttle and venturi all over the country for about 8 years. I never had a problem getting a needle with that combination. It milled really well and was super quick on response to the throttle. If I was racing now that's exactly what I would use. It is nice to have a pressure bottle and gauge or on board needle adjustment when you travel to a race with different altitude reading.

 

[Hammerhead]

That is what Dale says, Don! Really easy to mill, and it punches really quickly.

I guess my lack of experience with them was my problem. Nobody that I knew at the time used them, so I didn't have any help. I'm sure if you and Dale swear by them, they are the ticket. I think Dale just locks his carb open. I don't think he is using a venturi.

Hammer

 

[Ian Inverarity]

Atious,

I would tend to use the carb first and either remove the exhaust throttle or lock it open. A carb would be a safer option for a nitro beginner to start with. The exhaust throttles can be easier to tune in my experience, but if the exhaust throttle is not a good one, or is in bad condition it may leak causing the engine to run lean and very fast even with the throttle closed. This may result in the destruction of the engine. More experienced boaters can deal with this.

Once you are used to using the engine you could then lock it open and use the exhaust throttle to get the benfits of on the water response and easy of tuning.

Ian.

 

[EatMyShortsRacing]

Hey Dale,

Who does your exhaust throttles? I have a few ideas on construction to stop them leaking if you wanna have a lil chat..

EMS Racing

 

[Atious]

I havent gotten a pipe or header combination for it yet but the exhaust throttle came with the OPS.67 when I got it and the carb is the same one listed in the paperwork diagrams from OPS. The E. thr. seems a tad loose but can be snugged a bit with set screws. Still feels like it might leak on opposing sides tho. If the barrel were on a carb I'd throw the carb out for fear of vac leaks.

I think I'll replace the header and go with the carb first.