RS101 Fuel System

[Joe Warren]

Many boaters have had there share of problems with the RS101 & fuel delivery problem. I own many of these engine & have had very litle problems. But I will share a little info I have learned to help your RS101 engine Live....... # 1 Is Fuel Delivery. I say this Because when we mod the carb for third channel operation the fuel problems begin. Now the New Mod Carb is Only a Throttle Body. Only able to deliver AIR. You must Now pay special attention to the Fuel system. It starts @ the Pipe pressure fitting.... Low Fuel pressure & a Wide Open Carb is a Lean Condition.... It Will Make the Engine fail premature..... A few things that are a Must. LARGE Pipe Pressure fitting. Something AS big as your water fitting 10/32 is Good. Next LARGE 5/32 Fuel Tubing. Fuel Tanks that Have Large Fuel tubing 5/32 A Xtra large Fuel Filter on the Fuel valve inlet. A Clean Needle, A long piece of 5/32 tubing on the low pressure side of the needle,(acts as a Sump tank Or a Fuel log) Clean Spray Bar. These engines pulling the props that they are intended to run will burn 25oz of fuel in 12-14 laps. YOU MUST BE ABLE TO SUPPLY FUEL PRESSURE to GO WITH THE CARB YOU ARE HOLDING WIDE OPEN. Any Restriction OR Low Fuel Pressure & You will have Lean Conditions... Also They are Hard On Header O`rings & Header Couplers. You Must keep these Items Fresh & inspected. Either One & You have a Air Leak Outside of the Carb & a Lean Condition. The RS101 Engine out performs Any Engine I have Ever Owned. But When you mod the carb from the way the mfger made it?? You must maintain the rest of the Fuel System & Pressure. Even a Stopped up fuel system can allow the engine to Run 1/2 throttle But will Not Feed it During WIDE OPEN Throttle Operation with Big props.

 

[Elias Vazquez]

Hi Joe,

Although I don't run the RS101's just wanted to express my gratitude toward you and anyone else that takes the time to share they're findings and knowledge with us, so that we don't have to learn the hard way "breaking parts" and spending alot of $$$.

btw making good progress w-the pitch guage you sold me, now that I've learned to use it some.

Much Appreciated, Elias

 

[Joe Warren]

Elias always glad to help out, Hopefully we can race together this year & I can see your progress with the twin, Today WE can Buy Awesome Engines for the Twin Applications, However many are use to the 67-80 engines & there fuel systems, There was room for error in the 67-80 fuel systems. But the Larger CID engine want More Fuel to be Delivered & we are only using Pipe Pressure to push the fuel. This may be why we have seen the (black) fuel pumps on the intake side of the XP 90 Picco? I have no idea if it actually worked. But I would guess they Needed More constant Fuel pressure than the pipe pressure would supply.......

 

[Tom Foley]

Good info here on the fuel systems . It seems that if you are able to needle the engine blubbering rich then your setup should be capable of feeding the engine no problem as long as you are using the 5/ 32 " tubing and tank outlets .

 

[Joe Warren]

Good info here on the fuel systems . It seems that if you are able to needle the engine blubbering rich then your setup should be capable of feeding the engine no problem as long as you are using the 5/ 32 " tubing and tank outlets .

AS long as you can remain RICH... WIDE OPEN THROTTLE Your Fuel system is capable of delivering Fuel. But If you know you are RICH & as soon as You Pop Open the throttle valve the Boat Jumps to Attention??? & Seems to Come Into Its Own Needle?... You better look @ a few things before you extend the WIDE OPEN THROTTLE POSITION...... If you get it Right & I know you Will, The only thing that can trip you up is a Dirty Fuel Filter. They Must Be Maintained DAILY.. Or it will become your New Needle.. For Twin engines If you have a Engine that really revs up in the corners But It is together with the other engine in the straights? It is having a starving fuel cond...... Could be just a filter. But you better look @ it... Epecially if the Needles are flowing the same numbers?

 

[Mark Bullard]

Elias always glad to help out, Hopefully we can race together this year & I can see your progress with the twin, Today WE can Buy Awesome Engines for the Twin Applications, However many are use to the 67-80 engines & there fuel systems, There was room for error in the 67-80 fuel systems. But the Larger CID engine want More Fuel to be Delivered & we are only using Pipe Pressure to push the fuel. This may be why we have seen the (black) fuel pumps on the intake side of the XP 90 Picco? I have no idea if it actually worked. But I would guess they Needed More constant Fuel pressure than the pipe pressure would supply.......

One of the old school ways of delivering fuel was to drill the case and install a fitting that had a check valve in it. This allows the pressure to come from the crankcase. This is how the Pico is working and that is how the perry pump works. I think that the old perry pumps had a built in regulator also. These old pumps are what was used on ducted fan engines. This is were a lot of our boat engines (K&B 45's, Rossi 65's, OPS 45's/65's) came from in the early years.

 

[Joe Warren]

Mark I know you have thought of this..... & we have about exceeded our Old Design fuel systems of yesterdays Boats........ Some of the gas engines are running perry pumps on them for the same reasons........

 

[HendricX]

You can regulate the flow on the Perry pump ... mine is set to flow 8L/h , and works like a charm.

This is the way I make pressure fittings on a CMB :

 

[brett english]

You can regulate the flow on the Perry pump ... mine is set to flow 8L/h , and works like a charm.

This is the way I make pressure fittings on a CMB :

View attachment 27013

JOE..that were on the topic of fuel flow i just had to thank you and ralph to making me fix mount my bob violet needles vertically..wow what a difference..my needles are so much more consistant and you can fine tune them so much easier..never again will i have free

floating needles!! just looking foward to the big race that we can all compete against eachother

 

[Joe Warren]

You can regulate the flow on the Perry pump ... mine is set to flow 8L/h , and works like a charm.

This is the way I make pressure fittings on a CMB :

View attachment 27013

JOE..that were on the topic of fuel flow i just had to thank you and ralph to making me fix mount my bob violet needles vertically..wow what a difference..my needles are so much more consistant and you can fine tune them so much easier..never again will i have free

floating needles!! just looking foward to the big race that we can all compete against eachother

Your Welcome, WE have made about a Zillion laps with Nitro Twins in the last 6-7 years. When you are running 2-3 Twins Under 1 Tent you learn very Fast what Does & Does Not work........

 

[Joe Warren]

Good info here on the fuel systems . It seems that if you are able to needle the engine blubbering rich then your setup should be capable of feeding the engine no problem as long as you are using the 5/ 32 " tubing and tank outlets .

Tom, Ever single one of those Pistons you fixed that were holed...... That same boat it came out of had a Fuel delivery Problem that caused it...... Too small pipe pressure fitting. (cannot keep the tank aired up) too small fuel tubing (cannot transport the fuel from a-z fast enough) Stopped up fuel filter (became secondary needle restriction) Trash in a Needle valve (for those that dont run filters) Burnt Header Coupler or Header O Rings (air leak outside of the carb ) Cut or split fuel pressure hose (causes low fuel pressure or insufficient Fuel Delivery) to the Needle Valve....... as you start to push for more prop & speed with the 91`s This is a problem too....... They will turn the same cup props. Just dont have the Explosive Speed out of the Corners like a RS101......... Most twins haul total 40 oz for the Vac 91`s.. The Modified RS101`s will Need 50 oz to run the same laps....

 

[Tom Foley]

ote name='Tom Foley' timestamp='1304947280' post='414216']

Good info here on the fuel systems . It seems that if you are able to needle the engine blubbering rich then your setup should be capable of feeding the engine no problem as long as you are using the 5/ 32 " tubing and tank outlets .

Tom, Ever single one of those Pistons you fixed that were holed...... That same boat it came out of had a Fuel delivery Problem that caused it......)

Actually in some cases it was because the Mothership ( CMB ) decided to mill flat the underside of the dome rendering it too thin to dissipate heat without burning through under situations of less than perfect conditions in the combustion chamber . No doubt lean = heat = improper combustion and possible detonation etc ..but ..this never used to happen to the degree it is now . Can't blame this one on ethanol LOL . :lol:

 

[Joe Warren]

Whats the First thing you must do when you prop Up????? Richen up the needle???? Well the 7.0 CMDI props will load the Engine.... & IT WILL CALL FOR FUEL.. Better have some Fuel PRESSURE......... Same thing happens on a Drag motor in a 1/8 mile pass. If the Fuel pressure drops while you have the NOS Button DOWN??? The EXHAUST Valves are Tuliped It unloades the Valve Springs & things begin the come apart Quick............... I have seen it many times in Drag boat motors........ Just like a Blow torch When you are adjusting the Air & Fuel right before you make a cut....... OPS we have it Real hot & introduced more air...... You know what happens......Pointing the finger @ the piston is Simple. But the Real problem will still exist....... I tested a Exhaust pyrometer on a tow trk one day that would run about 700-850 degrees on the front barrrels of the carb. if you mashed it to the floor & opened the back barrels it would rasie to 1300-1500 ex temp quickly under a load...Problem was NO Fuel Pickup Tubes in the carb hsg @ the rear barrels. WE were suppling plenty of Air But NO FUEL to GO WITH the INCREASED AIR...... They had fallen to the bottom of the float bowl. the same vechicle had already burnt up 2-3 complete engines prior to this....... Fixed the fuel delivery problem Fixed the Trk........1st Mechanic should have found it..... The Pipe pressure works Good on many applications of Boats But A BIG Modified Engine Swinging a MAXXED OUT Prop & Your going to NEED MORE FUEL TO KEEP IT ALL HAPPY.......

 

[dwilfong]

Joe what are you using for a pipe pressure fitting. A strait fitting makes it very hard to rout the hose on a rigger. the sweeping 90 fittings I am using are only .080 inside diameter and feel this is a choke point in the system.

David

 

[dwilfong]

Joe what are you using for a pipe pressure fitting. A strait fitting makes it very hard to rout the hose on a rigger. the sweeping 90 fittings I am using are only .080 inside diameter and feel this is a choke point in the system.

the BV needle is only .100 ID on the nipples. would drilling them out help. I run a .100 spray bar on my MAC .550 carb and I am thinking that every thing in front of it in the system should be larger to make the system work good.

David

 

[Joe Warren]

Joe what are you using for a pipe pressure fitting. A strait fitting makes it very hard to rout the hose on a rigger. the sweeping 90 fittings I am using are only .080 inside diameter and feel this is a choke point in the system.

David

David I use a CMDI LARGE Pipe Pressure Fitting 10-32, & Tibadough sells some Stainless Pipe pressure fittings here on IW That I have bought also They are LARGE With a slow bend..... (very nice)

 

[Joe Warren]

Joe what are you using for a pipe pressure fitting. A strait fitting makes it very hard to rout the hose on a rigger. the sweeping 90 fittings I am using are only .080 inside diameter and feel this is a choke point in the system.

David

CMDI Large Pipe pressure fittings. Or about any 10-32 fitting something as BIG as you water pick up fitting in the ruddder.

 

[Joe Warren]

David the large Fitting in the Pipes will allow the Fuel Tanks to see the Pressure Changes in the Pipe Quicker........ NO DELAY........ This is what you want consider it only take a split second to Crack the Throttle Wide Open. It would be nice to have a Fuel injection for the R/C engines. They set there with 40-60 psi of fuel that can be delivered in mill sec as soon as the throttle angle changes & it is atomized @ the same time it comes in. Our carbs & the delivery of the fuel is Extremely Old Design..... But there are a few things we can do to make them Perform Better. If you have seen some of the latest trick carbs they want to Emit a Stream of Air Right thru the center of the spray bar as the fuel is coming in. This helps atomize the fuel too. Also a few things have been done to cut down on turbulence of air coming into the carb throat.... That is why we see dividers in the center of the Throttle body hsgs of most fuel injection systems.