Twin Guys Question

[Don Ferrette]

Question from a newbie playing with a twin? If both needles are set the same do you tweak the right prop to handle the extra load????

Nope.

 

[Don Ferrette]

Tried all kinds of set ups over the years for mixture control on the twins, now it's two simple isolated manual needles for me.

 

[John Beardslee]

Good thread Doc,

I tried fixed jets (no needles) when we built the first flow meters but still had variation depending on the days temp and elevation, then we got Kinsler's air density gauge and still we had inconsistant runs and went back to inflight needles mounted both on the carb and remote. Stayed with the remote mounted inflights mounted to a bracket on the boom. The big ahaa moment with the flow meters came went we found that no 2 needles flow the same with the same movement or rotation ie: 1/2 turn on one would flow a different number than 1/2 turn on the other needle. So we polished and flowed needle after needle to get consistant pairs to use. I've got some BVM needles and OS that I'll be doing checks on for my twin in addition to the paired old Rossi needles. The nice thing about todays computer radios is the ability to adjust the trim step and get the amount of flow change you want and the new Boris flow meter to compare one needle to the other.

Thanks, John

 

[Greg Hahn]

Tried all kinds of set ups over the years for mixture control on the twins, now it's two simple isolated manual needles for me.

I"m with Don, I use two isolated OS 9B needles with "fine" taper. test and flow and once they're right leave em alone!! 1 1/2" fuel line between needle and carb

gh

 

[Grimracer]

If some of us feel a twin might be best simplified WITHOUT the use of a 3rd channel setup why would we feel we need it on our "normal" boats?



I for one do not and or never have used a radio operated needle on ANY nitro boat. Is it just me?



I still get my wins and losses but the losses never seem to fall under “needle setting”.



Grim

 

[Rick Pirrone]

i run close to carb so far no dramas

have run two remote and one remote and one fixed now trying mark grims remotes

 

[Tom Foley]

Tried all kinds of set ups over the years for mixture control on the twins, now it's two simple isolated manual needles for me.

I"m with Don, I use two isolated OS 9B needles with "fine" taper. test and flow and once they're right leave em alone!! 1 1/2" fuel line between needle and carb

gh

Greg I have the same setup in my Ferrette Roadrunner Twin 90 boat ( VAC - 91's ) with about 4- 1/2 " between needles and carbs and it also works great , same needles . It seems like if you are using large - 5 /32 " line and tanks with 5 /32" nipples and internal tubing the engines are not sensitive to the customary length of lines one would get from mounting toward the rear of the engine bay .

 

[Tom Foley]

If some of us feel a twin might be best simplified WITHOUT the use of a 3rd channel setup why would we feel we need it on our "normal" boats?

I for one do not and or never have used a radio operated needle on ANY nitro boat. Is it just me?

I still get my wins and losses but the losses never seem to fall under “needle setting”.

Grim

I have found out that it really helps if you don't have time to test prior to the race so if you do go out a bit lean or rich you can make a correction but you have to practice a bit with the flow meter to see how drastic the adjustment can be .

 

[dwilfong]

I have had some very good results with my new fuel set up.

Had a tank made with 3/16 tubing in the out put side and sump.

Then modded a BV needle with 3/16 tubing.

The lines are Dubro ex large 5/32ID.

This all goes to the carb with 3/16 tube in it.

Then I soldered a length of 5/32OD 1/8ID tube to that to make the spray bar in the boar.

It stopped the problem of the setting changing as the fuel got lower in the tank.

The Eng dose not lean over at the end of a run.

I can set the eng at a leaner setting and not have to play with the needle after it is set.

1/8ID tubing works fine for the pressure side. Air moves much easer thew the tubing.

 

[Andy Greene]

If some of us feel a twin might be best simplified WITHOUT the use of a 3rd channel setup why would we feel we need it on our "normal" boats?

I for one do not and or never have used a radio operated needle on ANY nitro boat. Is it just me?

I still get my wins and losses but the losses never seem to fall under “needle setting”.

Grim

I have to agree 100% - I have both my 40 Mono and my Modvp setup this way and they come back hot nearly every heat- Do I give up a little every now and then- yes. Is the end result worth it- Without Doubt

My Scale will come back to me with third channel and as John stated about todays radio's-

I will give myself a VERY narrow window of adjustment based off a flow meter reading .

Just my .02 - but its waaay to easy to get greedy on the needle.

That said. I do see Foleys side of it- You need more time and less boats bro

 

[Piston1]

Joe has the answer on why to mount away from the carbs. I think a small actual reservoir between the needle and carb may work better. I tried this at the fall Nats on my single 101 and throttle response was the best I have had.

Now Joe, team Captain, do you think that the needles stay in sync with adjustment once they are set? IE with one number change on the transmitter changes the flow change is the same in each individual needle?

Any thought on one mixture controlled motor and the other with just an isolated needle?

Many years ago a guy by the name of Jerry Devay and his son each ran twins of his own design. His motors were ALWAYS TOGETHER AND BAD FAST without todays flow meter. He had the most consistently running twins I have seen run. HE USED ONE MIXTURE CONTROL NEEDLE THE OTHER NEEDLE WAS JUST AN ISOLATED NEEDLE.

Doc,

The name is Gerard (Jerry) Davet and his son Jean Paul Davet. Jerry was a commercial pilot. He was a regular racer at Huntsville and came to Knoxville once. He ran own design boats with OPS 80 engines. He told me once that his preffered fuel was Sig 35% (oil half Castor half synthetic). He used to come to the start line, start Jean Paul's twin and his, all engines at low speed idle before launching. Jean Paul had to stand in a short step ladder to reach the top of the drivers stand. He was 8 yrs. old at that time, racing a twin OPS 80 rigger. Impressive.

JOSE

 

[Joe Warren]

Many things have changed over the years in how we tune a twin, #1 is the Carb Barrel Valves Must be Perfectly the same. (wide open, Mid throttle & Off) # 2 Put all of the fuel you plan to race for the weekend in 1 jug. Reguardless of the Nitro & oil content. Your Viscosity will remain the same the entire race weekend. NOones fuel is consistent from Jug to Jug. # 3 Make Sure Needles and Tanks and Fuel filters are CLEAN.........#4 flow the needles with a Good Quality flow meter. I normally flow the outside engine about 2 clicks leaner cause it is loafing most of the time and trying to Go Cold. #5 control your water flow & Know your engines best operating temp range for Power & Rpm.... #6 Make sure Your head volumes and head squish are the same #7 Run a Match set of props if your matched set of props 1 has less pitch Run it on the inside engine. it will help the Boat lauch out of the corner. #8 if you have built the boat correctly and Flowed the needles the same & You have been on the water running with success? Read the plugs after every run. If the Boat Runs correctly the Next step is to maintain that set up for 2-3 days of racing. Make sure you have a Direction drawn on your fuel filters ( Arrow scribed onto the fuel filter hsg showing the direction of flow) Back flow the filters after every heat of racing to remove any trash that may have been trapped. If you have been running Correctly and you Fire the Boat Up and One engine is Way out of tune. Look at barrel valve locations, Clean & back flow the fuel filter... Clean & Back flow the Needle. DO NOT TRY to Correct the Running by just twisting the needle. If you have Not Found the REAL Problem the engine Now sounds different??? the Boat is now Dialed out Untill someone comes along & fixes the REAL problem & Re-flows the Needles. The Perfect Twin will Run Hard and Fast & Give Plug readings that are the same. At this time you are getting max performance from Both engines.

 

[dr gary turner]

Joe discussed basic good principles of twin running. John, you NAILED the issue. NO TWO NEEDLES WILL FLOW THE SAME WHEN ADJUSTED AS IN A REMOTE NEEDLE. SOOOOOO HOW CAN THE NEEDLES ONCE FLOWED AND MATCHED BE ADJUSTED TOGETHER AT THE SAME TIME RICNEN OR LEAN EQUALLY THE SAME AMOUNT?????????.

I do think having an adequate volume of fuel readily available to the carbs at all times is critical in having the motors stay in sink. Again I tried a reservoir between the needle and the carb and was close to the carb in the single 101 hydro and there seemed to be better consistency in how the motor ran.

So could the best set up be the outboard motor has an isolated needle and the inboard have a remote adjustable needle., therefore having one less variable that is not consistent? Thus adjust the loaded motor to keep them in sink with fuel reservoirs to keep an adequate amount of fuel readily available for good throttling?

 

[Duke Mordja]

Doc,

In setting up my first twin, I set my two remote needles up with one servo. I must have lucked out with my needle valves as they do flow the same throughout the richer/leaner adjustment of the third channel.

I agree with your idea of the inboard/outboard being separate. I would possibly suggest having both adjustable on their own servo and running a 4 channel radio. This way those who could have time to adjust, they could adjust both if needed. With enough testing, one button on radio could adjust both servos at different rates-keeping flow equal if the radio is capable.(programmable mixing) Not sure if 4 channel radios can do this function on the 3rd and 4th channel. I know my 3rd channel can change like this from steering or throttle control.

Right now, testing is the only place I adjust the needle on my twin. I agree with many of the posts above that once you have a boat setup, you really don't need to change needle during a race--- unless you are that close on pipe/prop setup.

I do run the remote needle behind the engine and have about 3 inches of fuel line between needle and carb to act as a reservoir and never have an issue with fuel supply. I think that behind the engine-fuel is mainly delivered to the engine based on fuel pressure from pipes and vacuum from piston action. In front of motor, I think centrifugal force and constant change in direction can alter fuel delivery. (purely theory with no backup and probably so minimal we could never tell). Clean tanks and no filters to crap up. Multiple fuel filters while fueling. Keep pump and fueling lines in sealed ziploc containers while not fueling. Haven't had fuel issue in my short 3 years in rc boating. I think if I ran where there is quite a bit of sand - beach like - onboard fuel filters would be best. Sand particles attach to everything and go everywhere you don't want them and see that being a problem in the needle valves.

As Joe mentioned above so well, good principles and accurate engine setup-followed in a systematic routine is the best. Had I remembered to properly tighten my glow plug in the 4th round at Hobart this year, I may have been able to maintain first place with my two week old twin. Four seconds and a goose egg in round four was good for 7th place by 119 points if I remember right.

So much fun!

 

[charles siler]

My experience with third needle were sooper bad with my twin OPS 90s. I had twelve of the Andy brown needle and couldnt get them to flow togethet while adjusting up and down . Andy sent me a set of longer tapered needles and worked better . The next season I got a Boris meter and changed to the OS 9B needles with sooper Success! and I watch the weather and change the flow as needed . Its to easy to kill the inside motor with the adjustable needle. Test test test get your setting and have a killer time with it. later Charlie

 

[John Beardslee]

Hi Doc,

I spent alot of time working with the needles and was able to help to get them to flow closer to the same but the biggest gain came in looking at the seat area for the needle. I used spotting blue and found some off center, some with burrs/rough edges. I used dentist tools to scrap and smooth and then pieces of ink erasers to finish. Later I used Cratex mounted bobs to smooth the seats. Also no two drilled holes will automatically flow the same. I used to take music wire and put a long tapered point on it with the belt sander and used it to resize the holes to get them to flow the same with no needles in them. That's how we did the fixed sized jets to get the flow reading the same. When John Ackerman was running Midgets and using Hilborn injection he found that none of the same numbered/drilled jets (Stromberg 97) flowed the same and did the same kind of work on them using the flow meters we built.

Thanks, John

 

[dr gary turner]

Doc,

In setting up my first twin, I set my two remote needles up with one servo. I must have lucked out with my needle valves as they do flow the same throughout the richer/leaner adjustment of the third channel.

I agree with your idea of the inboard/outboard being separate. I would possibly suggest having both adjustable on their own servo and running a 4 channel radio. This way those who could have time to adjust, they could adjust both if needed. With enough testing, one button on radio could adjust both servos at different rates-keeping flow equal if the radio is capable.(programmable mixing) Not sure if 4 channel radios can do this function on the 3rd and 4th channel. I know my 3rd channel can change like this from steering or throttle control.

Right now, testing is the only place I adjust the needle on my twin. I agree with many of the posts above that once you have a boat setup, you really don't need to change needle during a race--- unless you are that close on pipe/prop setup.

I do run the remote needle behind the engine and have about 3 inches of fuel line between needle and carb to act as a reservoir and never have an issue with fuel supply. I think that behind the engine-fuel is mainly delivered to the engine based on fuel pressure from pipes and vacuum from piston action. In front of motor, I think centrifugal force and constant change in direction can alter fuel delivery. (purely theory with no backup and probably so minimal we could never tell). Clean tanks and no filters to crap up. Multiple fuel filters while fueling. Keep pump and fueling lines in sealed ziploc containers while not fueling. Haven't had fuel issue in my short 3 years in rc boating. I think if I ran where there is quite a bit of sand - beach like - onboard fuel filters would be best. Sand particles attach to everything and go everywhere you don't want them and see that being a problem in the needle valves.

As Joe mentioned above so well, good principles and accurate engine setup-followed in a systematic routine is the best. Had I remembered to properly tighten my glow plug in the 4th round at Hobart this year, I may have been able to maintain first place with my two week old twin. Four seconds and a goose egg in round four was good for 7th place by 119 points if I remember right.

So much fun!

 

[Joe Warren]

Doc One thing I missed... Take your Propane Flow tester & turn up the propane regulatior to 15, Check the resistance to flow on Your fuel Tanks. Especially if you are buildng them & NOT Buying them from Walt barney.... Just a slight bend on the supply line to fill the small tank can make a big difference when you have a boat that is blowing 50 plus Oz of fuel threw it every 10 laps....... & also the Pipe Pressure Fitting is the Fuel Pump for a High fuel flowing Twin. the Pipe Pressure fitting MUST be large enough to keep fuel flowing and pressure on the system at the same time. P.S. Even though you Suspect a Problem at the needle location?? The Real Problem is Everything Outside of it........ B) One last thing!!!! if you really want to test the entire system to find the difference? Hook The Boris flow meter to the Pipe pressure line and flow the entire system all hooked together completely thru the Tank, Filter, Needle & Spray Bar. If you Find a difference & the needles are flowed the same? Disassemble it and find the probelm with the flow meter. Yes, the spray bar is part of the fuel delivery system & many flow around it?????

 

[dr gary turner]

. Tried 4 channel with a v-tail mixer by Ace radios, not good. Too much going on!!'

Doc,

In setting up my first twin, I set my two remote needles up with one servo. I must have lucked out with my needle valves as they do flow the same throughout the richer/leaner adjustment of the third channel.

I agree with your idea of the inboard/outboard being separate. I would possibly suggest having both adjustable on their own servo and running a 4 channel radio. This way those who could have time to adjust, they could adjust both if needed. With enough testing, one button on radio could adjust both servos at different rates-keeping flow equal if the radio is capable.(programmable mixing) Not sure if 4 channel radios can do this function on the 3rd and 4th channel. I know my 3rd channel can change like this from steering or throttle control.

Right now, testing is the only place I adjust the needle on my twin. I agree with many of the posts above that once you have a boat setup, you really don't need to change needle during a race--- unless you are that close on pipe/prop setup.

I do run the remote needle behind the engine and have about 3 inches of fuel line between needle and carb to act as a reservoir and never have an issue with fuel supply. I think that behind the engine-fuel is mainly delivered to the engine based on fuel pressure from pipes and vacuum from piston action. In front of motor, I think centrifugal force and constant change in direction can alter fuel delivery. (purely theory with no backup and probably so minimal we could never tell). Clean tanks and no filters to crap up. Multiple fuel filters while fueling. Keep pump and fueling lines in sealed ziploc containers while not fueling. Haven't had fuel issue in my short 3 years in rc boating. I think if I ran where there is quite a bit of sand - beach like - onboard fuel filters would be best. Sand particles attach to everything and go everywhere you don't want them and see that being a problem in the needle valves.

As Joe mentioned above so well, good principles and accurate engine setup-followed in a systematic routine is the best. Had I remembered to properly tighten my glow plug in the 4th round at Hobart this year, I may have been able to maintain first place with my two week old twin. Four seconds and a goose egg in round four was good for 7th place by 119 points if I remember right.

So much fun!

 

[Albert Araujo]

I run a pair of BVM needles up front with no remote setting. I set both needles with the Borris meter. After my first heat I tweak based on plug readings. This works for me and it keeps it simple. I swear by the Borris meter.

Albert