dual plug engines

[avbrando]

just picked a used cmb .65 and it turned out to be a dual plug engine, just wondering what the starting proceedure is for an engine with two plugs and any problems/benifits associated with them, also the low speed needle has beed removed and sealed, how will this affect operation? any help is appreciated.

Brandon

 

[DickJones]

Brandon

I did alot of testing with dual plug heads, they do have more torque on launch and low speed however when trying to get high RPM's the dual plugs disrupt the swirl in the button and if U lean to much you stand a good chance of blowing one of the plugs and the air to fuel mixture will go instanly lean in the engine. Also make sure U keep the plug oreintation centered on the side to side, (over the transfer ports), if U mistakenly rotate the glow plug oreintation from front to back, (over the boost and the exhaust), U will loose alot of the engines power.

Hope this helps

dick

 

[Andy Greene]

just picked a used cmb .65 and it turned out to be a dual plug engine, just wondering what the starting proceedure is for an engine with two plugs and any problems/benifits associated with them, also the low speed needle has beed removed and sealed, how will this affect operation? any help is appreciated.

Brandon

I was fortunate enough to get both the single and dual plug head button when I purchased mine (90 cmb) . Good thing cause the dual had a stripped plug thread.

I have yet to repair it and try it, the single plug runs well enough to get the job done

The person I got it from swears it runs better with the dual plug though :blink:

Andy

 

[Ron Olson]

If you're wondering about the starting procedure, I've seen guys fire them up on one plug and once running, hit the second plug for a second with the glow driver. One other good side effect is that if you fry one while running you may still have the other one to keep you from a DNF.

 

[avbrando]

thanks for the reply guys, we can't wait to see this thing go. hopefuly it runs as fast as the single plug flatslide engine that is in dad's rigger now (without the carb falling appart repeatedly). any problems running a .65 rigger with the low speed needle removed and capped?

 

[Andy Brown]

thanks for the reply guys, we can't wait to see this thing go. hopefuly it runs as fast as the single plug flatslide engine that is in dad's rigger now (without the carb falling appart repeatedly). any problems running a .65 rigger with the low speed needle removed and capped?

We always removed the low speed needle.

Since the low speed needle was removed hopefully some of the other needed engine mods are taken care of too.

That's a VERY fast engine with a few proper mods. In stock form it's a total dog.

Back when we were running those in the original Jaguar the modded engines would run in the high 80's with an H-32 and we even got one to 97 mph with a cupped up 65x110. John Brown won IMPBA US-1 in 1994 and again 1995 with that boat/motor combo.

The stock engine in the same boat is good for low to mid 60's and will be inconsistent on the needle.

 

[BigChuck]

Andy

Dicks inforation is spot on. The single will rev higher. If you run the dual you have to be willing for it to come to you on the heat. Or push them richen because of the heat.

Found it easy to push and them richen. Around lap 5. you can here the motor when the plugs go. Oh yeah costly, you blow two plugs in one run.

 

[Andy Brown]

Andy

Dicks inforation is spot on. The single will rev higher. If you run the dual you have to be willing for it to come to you on the heat. Or push them richen because of the heat.

Found it easy to push and them richen. Around lap 5. you can here the motor when the plugs go. Oh yeah costly, you blow two plugs in one run.

I'll have to disagree about a single revving higher than a dual plug. Years ago when we where running dual plugs on lots of different engines, they did in fact have much more torque and less revs than the single plug in most applications, but that is only because we didn't have everything working in unison.

I have had some engines that turned much more rpm with Dual plugs and that was after much testing with both types.

Dick is correct about the plug orientation being critical to performance. Anything other than side to side won't work at all.

This situation you mention Chuck, about having to wait for it to come up to temp and them richen it, is simply a result of improper fuel delivery.

And I don't mean improper needle setting. I mean carb configuration and transfer timing.

It's been 12 years since I've worked with dual plugs. With what I've learned about our little nitro engines since then makes me believe that there is a huge amount of power to be gained by running dual plugs. Especially in the BIG engines like you run Chuck!

 

[Chris Wood]

there must be something to it.. this guy know's his stuff

http://rbmods.net/rbshop/index.php?target=categories&category_id=65

 

[Andy Brown]

there must be something to it.. this guy know's his stuff

http://rbmods.net/rbshop/index.php?target=categories&category_id=65

"We are designing new heads for Nova Rossi, RB Concepts,Picco, Go Tech Engines. These heads are to be fitted with a redundant plugs system "RPS". The idea is to be able to blow a plug in a race and still be able to finish the race, Better fuel economy, Higher compression, Lower temps do to the directed flow of the spray path."

Chris,

Not much of what he says relates to reality.

If you blow one, you blow both.

Two plugs burns more fuel....that does not equate to fuel economy.

When you burn more of the fuel, you need lower CR, not higher.

But I will say it again. If everything is set up properly a high nitro engine can make more power with two plugs.

One group of people that DO know their stuff!...TOP FUEL drag engine builders!...and they run TWO PLUGS per cylinder!

 

[Ron Olson]

OK, just little old pretty much know a little me.

RB Mods, I take this guy with a grain of salt. He's selling almost the same engine that Glenn Quarles is selling for $165.00 and he wants over $400.00 for?

Why would anyone bother to mod a Traxxas engine?

What I've learned about nitro. It is by nature a slow-burning fuel so higher percentage nitro burns better in a smaller engine and in a higher cube engine you want lower nitro otherwise it's wasted, right? A dual-plug engine will help to burn more fuel so that in theory 2 plugs should be able to burn a higher percentage of fuel because of propogation.

Top Fuel and Funny Car motors fry their plugs and are completely destroyed by the time that they leave the starting line so then they're dieseling the rest of the way so the only way to really shut them down is to shut off the fuel supply.

Some of this I learned from Andy himself in a really old thread plus I'm an avid fan of drag racing.

 

[Chris Wood]

RB Mods, I take this guy with a grain of salt. He's selling almost the same engine that Glenn Quarles is selling for $165.00 and he wants over $400.00 for?

ron you need to talk to this guy the knows his stuff.

just my opinon

 

[BigChuck]

Andy............"TOP FUEL" yeah if I had MSD to power the plugs and the fuel pump flow that they have.................. :lol:

But the things mention are things that I have experienced running the motors with those heads. Also have had a few of them REVV like F1. But I put that effect down to the carb that was on the motor...........550 bore

 

[shoboat]

You can power your plugs, remember

Use Better Carbs that flow more fuel

Use Better Fuel

Make Better Head Buttons

Just A Few Things That Can Still Be Done,

Mark Sholund

 

[Andy Brown]

Andy............"TOP FUEL" yeah if I had MSD to power the plugs and the fuel pump flow that they have.................. :lol:

But the things mention are things that I have experienced running the motors with those heads. Also have had a few of them REVV like F1. But I put that effect down to the carb that was on the motor...........550 bore

Yes Chuck, I understand what you have experienced. I have experienced the same issues many many times. I am the guy that is responsible for CMB building their 67, 80 and 90 engines with duel and triple plugged heads in the early 90's. Previous to that, (1988-1990) I built many duel plug heads for OPS and CMB 67's, 80's and 90's. I still have a 4 plug head for a CMB 100 that I tested. It had enough firepower to burn pure 90% nitro/10% oil in that engine. That was before CMB even had a 100 engine. The first CMB 100's came by way of Ranjit Phelan big bore P/L's.

We had set up's that were much faster than the single plug heads, otherwise we (Me and Art McMeans) would not have asked CMB to build them. The problem was that if the engine was not set up correctly or the wrong modification was made, the duel plugs did not work. There's a lot more to it than just the carb bore size. It's many things about the complete system including the fuel tank, needle valve, pipe and of course the engine and carb itself.

As I mentioned previously, we had two Jag 67's with CMB 67 (black & gold) duel plug engines in them and they both ran high 90's in racing trim.

And when I say same racing trim, the boats were just as we raced them (full turnfins included) with the only difference being an additional 10% nitro and a bigger prop. One boat used an ABC 65x110 (cut down 1667) and the other boat ran an ABC H-32. It takes a lot of RPM to run high 90's with an H-32. Those duel plug engines would do it.

 

[Tom Foley]

Andy............"TOP FUEL" yeah if I had MSD to power the plugs and the fuel pump flow that they have.................. :lol:

But the things mention are things that I have experienced running the motors with those heads. Also have had a few of them REVV like F1. But I put that effect down to the carb that was on the motor...........550 bore

Yes Chuck, I understand what you have experienced. I have experienced the same issues many many times. I am the guy that is responsible for CMB building their 67, 80 and 90 engines with duel and triple plugged heads in the early 90's. Previous to that, (1988-1990) I built many duel plug heads for OPS and CMB 67's, 80's and 90's. I still have a 4 plug head for a CMB 100 that I tested. It had enough firepower to burn pure 90% nitro/10% oil in that engine. That was before CMB even had a 100 engine. The first CMB 100's came by way of Ranjit Phelan big bore P/L's.

We had set up's that were much faster than the single plug heads, otherwise we (Me and Art McMeans) would not have asked CMB to build them. The problem was that if the engine was not set up correctly or the wrong modification was made, the duel plugs did not work. There's a lot more to it than just the carb bore size. It's many things about the complete system including the fuel tank, needle valve, pipe and of course the engine and carb itself.

As I mentioned previously, we had two Jag 67's with CMB 67 (black & gold) duel plug engines in them and they both ran high 90's in racing trim.

And when I say same racing trim, the boats were just as we raced them (full turnfins included) with the only difference being an additional 10% nitro and a bigger prop. One boat used an ABC 65x110 (cut down 1667) and the other boat ran an ABC H-32. It takes a lot of RPM to run high 90's with an H-32. Those duel plug engines would do it.

Sounds like it needs to happen again !! I for one would rather run a twin with 67's than 91's any day !!