Look at new 2013 CMB91 RS EVO

[carlnoki]

Mauro

 

[Bart Drieghe]

The new engine seems to have more power and allows us to pull bigger props . Main difference is the crankcase , the crankshaft and the liner compared to the RS engine .

It is either we pull more prop....???? Or we think we pull more prop.....???? :huh:

You race 6.5 and now with no change you have to run 6.7.....????

Chuck ,

i cannot speak in terms of pitch but i can tell you this , we run 54mm props and with the evo type engine we can run 55mm ( and maybe more ) props . Its not thinking , it is so , Believe me

So your talking in terms of the new 3.5 Evo?

Or overdriving a 15cc Evo?

I was talking about the 15cc EVO

And yeppers , in FSR V .

I assume that , compared to the "improvement" we have that you guys will either run higher pitches or bigger props with the same "old" pitch .

The engine has more torque and easily takes the same props ,wich gives you the feeling being underpropped . From what i've seen , i don't think that there is an rpm improvement but i can't say this for sure as i haven't tested with the rpm meter in the boat and compared it to the RS .

IF i can say one "weak" point , its the crankshaft . There have been a few people who had a failure with the crankshaft ( once again , in FSR V ) but their problems seemed to be solved .

Chuck , i cannot say that Mauro was running this new engine at the WC , perhaps he had the insides in his Limited edition engine but thats something only Mauro can tell .

What has changed compared to the RS 91 :

Crankshaft ( has been made heavier )

Liner : has been changed in the outer diameter , inside diameter and piston are the same . 5 inlets , 3 exhaust

Carb is 13 mm

Crankcase has been changed , crankshaft can be used in the RS 91

That should be it i think .

B

 

[BigChuck]

Bart................Big thanks for the info. We will see how the motor holds up to the Knief and the High nitro. B)

 

[dwilfong]

 

[dwilfong]

Im more interested to know about the piston durability

David is there any noticeable change to the piston crown, pin height, crown thickness, pin boss thickness or materials change.

Too many guys are / were holing pistons. Even if at the time they went lean there needs to be more margin for error for most guys. 1 lean motor on a twin and you habe a holed piston.

The piston casting look good. plenty of meat on the boss and the crown is .115 thick. the taper is the same as the old piston with the pinch just above the wrist pin.

 

[Ian Folkson]

The first tests last year were in a RS case and the engine went very well.

But the extra torque came when Mauro put it in the new case with larger diameter liner and reduced transfer volumes in the case.

Mauro was actualy excited about the way the engine went in the production case (mauro does not easily get excited)

If the liner is modified and put in a Red case you will get a good engine but not the extra torque

Ian

 

[Joe Warren]

The Current RS 101 with the Correct Head Volume and the Corrected Intake Timing can turn more prop at high RPM than most boaters can drive in a Twin......... With No crankshaft issues and with Great life.... as long as you keep an eye on the location of the piston seal....... These engines could only be improved by CMB making a Billet alloy piston. So you could manage the piston to liner fit and the location of the piston seal.

 

[dwilfong]

.

 

[Tim_Duggan]

I'm going to play Devil's advocate here so be kind, but someones gotta say it - why not just run less nitro %?

if it makes plenty of power on less of the hot fuel than previously, and you're having to bend huge amounts of cup into the same prop blades now to keep the motors loaded (all the while the speed is still being governed to an extent by the L/E), then maybe, just maybe that nitro is being wasted anyway until better props are around. Kinder on parts, and you won't need as much fuel per run as the amount of fuel required per run drops when you lower the nitro %.

OK - flame suit on!

 

[Danny King]

There is no reason in heat racing to run that high of nitro. It is just popular.

 

[BigChuck]

There is no reason in heat racing to run that high of nitro. It is just popular.

I would almost agree with you....................But I have seen the difference.

 

[Danny King]

I'm not saying in certain set ups it doesn't make a difference. It's all about set ups. However when I was in this hobby about 13 years ago I was VERY FAST and only ran 33%. And a lot of people were still running 60 and 70% then.

The only reason I'm running 50 and 60 now. Is I just got back into it and it seems most available motors are set up for higher nitro. So until I can make my own head buttons I just went with the herd.

 

[dwilfong]

RPM is where it is at for speed. I have tried big props with big leading edge pitch using the eng toque to push them on lower nitro %50 and it was plenty fast.

But with a H50 6.9 cup spinning at 26000+ it is a blast.

High nitro is needed to run at higher RPMs.

Yes you can win races with less nitro and save fuel.

Heck I was going half throttle at the last race and almost a lap ahead of Jeremy's twin 45 boat and ran out of fuel with half a lap left.

I have learned my lesson DON'T GO SLOW!!

I race to go fast!!!!!!!!!!! Not just win races because I am the last slow boat running.

I don't want to race a Honda CIVIC.

But that is just me.

Slap the nitro to it and lets race!!!!!!!!!!!!!!!!!

 

[Tim_Duggan]

High nitro is needed to run at higher RPMs.

Not entirely correct. Lets call if for what is. "It's just easier with liquid torque."

 

[dwilfong]

So you think it is easy to burn 60% in a RS 1.01? :huh:

You ever burn a hole in one or pull the pin out of the piston at almost 28000 RPM?

 

[BigChuck]

High nitro is needed to run at higher RPMs.

Not entirely correct. Lets call if for what is. "It's just easier with liquid torque."

Tim....I go to "Loud Pedal Races" for one reason and one reason only!!! TO FEEL the punch in the chest as I am gasping for air. So yes you are so right!!!! B)

 

[Tim_Duggan]

So you think it is easy to burn 60% in a RS 1.01? :huh:

You ever burn a hole in one or pull the pin out of the piston at almost 28000 RPM?

Did I say it was easy to burn it, no. It's easier to find a setup with higher nitro than less was what I was getting at. Liquid torque gives margin for less than perfect everything. For example - the head button isn't right for the fuel either in volume, squish velocity etc etc. Altering the nitro content by upping it might bring it to a more acceptable set-up.

You said High nitro is needed for RPM like it's a definite thing. I can give you examples of motors pulling more than 28000 with zero nitro - pylon racers, tether car engines etc. Sure the power curve is totally different, but it's certainly possible to make a statement that rpm with low (or no) nitro IS in fact possible, in a generalised way, just like your statement.

28krpm with an RS101 crank equals massive harmonics. stuff like steel carb needles break clean off and go thru the motor. Yes - seen it. Wasn't pretty.

Hey Chuck,

Yep, nothing like that nitro hit - I agree 100%. The "high beam" effect it has on the female anatomy when a fuel car does a pass is, well - priceless!

 

[BigChuck]

Tim, we are on the same page on a few things. It was with my EVO motors that had this same style of mod that showed the issues of running high RPM in these motors.

Have attended a few plyon races and seem a few planes set up and tested for these events...........Mad scream!!!

"high beam" effect, yes a very polite way to explain what is..................Really going on!!!! :lol:

 

[Tim_Duggan]

I wish we had a Smilie for the high beam effect. ^_^ This one is kinda close!

 

[Stuart Barr]

Allan,

The 91RS EVO's are in my hands now. Email me at [email protected] if interest.

Stu