SPP RS or NR muffled pipe for CMB 21 BETA EVO

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The RS pipe is considered the faster pipe, the NR easier to throttle and heat race with. Either is a great choice, but I believe those pipes were more so designed around the wrap around exhaust systems.
 
I run my JAE 21 CMB 21 EVO with a CMB 21 NITRO Pipe.

Please watch both videos. 

It is an excellent all around pipe. Even for heat racing. 

Watch first video at the start. I am early (on purpose) Boat has great acceleration off pipe! 

 
Last edited by a moderator:
Tom David said:
First Video:

abc 1817-19-38

pipe at 7 3/4 inches

Second video:

cooler air (good air density)

abc 1819-19-38

pipe at 7 1/2 inches  

Fuel—John Otto   65%
Click to expand...
Tom,

Impressive that you can pull those props with a 7-1/2" pipe.  Is the pipe measurement from center of the engine to the weld, (accounting for the S bend in the step-up header)?, or is it plug to weld in a straight line?
 
Bob, the measurements are a straight line from center of bore to weld on pipe. 

The offset header that I use will add about 3/16 inch in length but I still reference everything in a straight line measurement.

Air density is everything—-especially on our little 21’s. 

The little 21’s really wake up when air temps are in the 50’s or cooler.

You probably won’t pull a 1819 in the 80’s.

Almost all records are set in cool temps. 

I do heat race with the 1817 and pull out the pipe in hot temps.

If your looking for optimum performance at each race, adjusting to air density is a must on our 21’s.   

I posted my opinion about the cmb nitro pipe to illustrate it is capable of obtaining very good results if you test and learn from that testing.

More time testing = more races won.

I also use different heat range plugs and less water during my testing   

I will also add that my cmb 21 is all stock except with a small removal of brass on the ramp fo the boost port. Timing was not changed.  

I was not able to keep my squish very tight on the stock turbo head button without detonation. I am opening the bowl and testing more in this area.   
 
Last edited by a moderator:
Tom David said:
I run my JAE 21 CMB 21 EVO with a CMB 21 NITRO Pipe.

Please watch both videos.

It is an excellent all around pipe. Even for heat racing.

Watch first video at the start. I am early (on purpose) Boat has great acceleration off pipe!

Click to expand...


I have noticed that a video was removed from this post by the moderator.

Was the video too offensive???

Tom David
 

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