What exhaust should I be running?
 

RC Tech nation, I am slowly but surely coming up to speed on tuning my motors, which makes understanding and selecting the correct pipe/header combination so important. I wanted to let you guys know what motors I have, along with the pipes I currently have, in order to see what combinations I should be running and if I should be going with another pipe/header all together to bring out the best in my motors:

.21 Mills:
Novarossi 21-5K (standard button) I heard the NovaRossi 9901 is a good pipe to be running on this mill
WERKS TL B7 Pro (turbo button)

.28 Mills
Sirio STI (standard button)
WERKS TL B7 Pro

Pipe Sets:
JP2
JP3
OS 2060

Thanks guys for your input!

Chad

people usually use a Top End pipe for 28 engines so I guess the JP2 or the JP3 should work good with your 28 mills.

about the Novarossi 21-5K, here's some info straight from A-Main Hobbies.com

"This engine works best with Novarossi 9886 or 9853 tuned pipes. The 9853 tuned pipe will provide more power on the bottom end with about the same top end as the 9886 pipes, however runtime will suffer. The best overal pipe for excellent runtime with smooth power delivery is the Novarossi 9886 with short header. The longer header will give a little more bottom end at the expense of runtime. The MSR1005 pipe also works well on this engine, but it also suffers from less runtime than the 9886 tuned pipes."

about the Werks engine, well i'm not sure, I used to have a Werks TL B3 and ran it with a Dynamite 086 "high speed" pipe and it worked good, but I didn't test it too much.

hope this helps.

Chad, this topic will open up a huge debate and you will hear alot of opinions and most of them will be decent. As far as what pipe is the best will depend on the motor. Each motor has different characteristics based on the design. For example: A Novarossi P5 with a 16.80mm stroke will make the most torque with a long header/long centered pipe and will make the most rpm with a short header/short centered pipe. The P5 can support the shorter pipe most of the time due to its longer stroke where as a short stroke motor like the V-Spec which has a 16.00mm may scavage properly with a shorter pipe.

Now before everyone gets bent out of shape, the V-Spec has the most aggressive intake crank timing of any stock motor I have seen and thats a huge reason why that motor is so wicked out of the box. Other than the crank timing being so wicked, the V-Spec is nothing more than a glorified RG. They have identical bore, stroke, port configuration and the V-Spec has 5 degrees more exhaust timing than the RG. Thats it, thats the big secret.

General rules of thumb:

Long Stroke Motors- make torque sooner and spool quicker with less peak rpm but depending on length of rod and radius of crank pin will determine piston speed between TDC and BDC which will in turn determine practical range of operation.


Short Stroke Motors- makes torque higher in powerband which usually means a long pipe is in order to get some bottom out of it in the lower revs. Most of the time a short stroke motor will require more aggressive clutching to get it to snap down low.

These general rules of thumb are just that-GENERAL. Motors with short strokes can still make power down low if they have low transfer timing and a long pipe to compliment that. For those of you who know the S7, the S7 has high transfer and exhaust timing and a shorter stroke (16.44mm) which makes it a high revving motor with not a ton of torque where as the Werks B-3 has low transfer and exhaust timing and it explodes off the line but doesn't have big revs in stock trim and thats why an S7 needs the longer pipe to get the torque and the B3 can get away with a short pipe. There are so many combinations engine manufactures have put together with their port timing and that is why every engine has different running characteristics.

As far as pipes, longer stroke and/or bigger volume motors tend to like the bigger volume pipes with bigger diameter stingers because the pulses are slower and stronger and the short stroke and/or small volume motors tend to like the smaller volume pipes with longer smaller diameter stingers. Don't confuse volume with length. For example: A JP1 is a long big volume pipe and the JP2 is a short big volume pipe. The 053 is a long small volume pipe and the 086 is a short small volume pipe. The inside diameter dictates the volume where as the length will dictate the scavaging characteristics but again will depend on the stroke and blow down timing of the engine its attached to. From my experience the bigger volume pipes produce more overall power where as the small volume pipes make less overall power but tend to be easier to tune because the window of tune is bigger or as we can call it less sensative to change and thats where you will get alot of opinions of which pipe to run because everyone's idea of properly tuned motor is a little different and what works in California with their altatude, humidity and barometric pressure may not work the same as someone in North Carolina.

So there really isn't an easy answer to which pipe goes with each motor. The best thing to do is to go to the track and get an idea of what people are running and how it looks and sounds to you. My absolute favorite pipe that has worked on all my engines is the JP1. I have run that pipe on every engine I use personally and is the most performance minded pipe with the best overall design. Other pipes I have tried that worked very well were the RB 2020, Ofna 053, 063, Mugen 1005, Sportwerks HT. Those are the longer pipes. Some of the shorter pipes I have tried that worked on the longer stroke motors with lower blow down timing were the JP2, JP3 and Ofna 086. I am sure there are alot of other pipes out there that will have similar effects and I do not have the time to buy and try every single pipe in existance with every motor in existance. So now its time to let the people speak and they will hopefully send you in the direction you want to go. This entry may not have answered every question but hopefully it puts you in the right direction.

Mark @ www.PowerHouseRCPerformance.com