.12 Headers

[ClayGlover]

howdy. what headers are you guys using on these rear round spring-held exhaust .12 engines? it's a sirio .12. i'll be using a mac 2.5 pipe, so a 180 degree header that will butt up right with that pipe would be preferred. :-

 

[MikeP]

The header for the Associated truck and the Picco exaust motor.

They say it is a bit small for some of the .12's but can be made to fit.

Tower hobbies has them. They are made by Picco

http://www2.towerhobbies.com/cgi-bin/wti00...p?&I=LXTB61&P=7

-MikeP

 

[ClayGlover]

thanks Mike, yep that's the type.... $32 (out os stock) i was hoping to find a "cheep" one. i can get a whole pipe system for that much here-

cheap exhaust system

maybe it can be modded to work with a mac pipe. that exhaust is one Tom Moorehouse suggested. maybe i'll try it out first. this one might work?-

ebay header and pipe

any others out there? thanks.

 

[ClayGlover]

well, after a manifold/header search on ebay, it seems there are a lot of headers there for little cash. for anyone else interested-

header 1

header 2

header 3

header 4

 

[wswatzell]

I have the Associated 180 header for my HH12. I have an OS TR/PT. the same kind that you have linked in "header 1" don't know how it works yet, but it looks really cool with the blue cooling head on my engine.

 

[Ron Olson]

Clay, that Associated header isn't a bad price for what he wants for it. I paid $15.00 for a Traxxas header on the HH .12 at the LHS.

 

[ClayGlover]

here it is at tower-

blue

silver

black

 

[MikeP]

I have noticed the ID is .49" on the Associated 180 headers. Thats as big as my 3.5. I will double check my Picco pipe's ID.

Here is a little cheaper place. 25.00

http://www.teamtrinity.com

-MikeP

 

[Don Templeton]

By the time you cut the Macs pipe down to the correct length, the match on the Associated header ID is perfect! But I don't know how it fits the Sirio port.

Don

 

[MikeP]

The Picco header is .45" still a little big, Need to find a header around .38"-.40" inside diameter. I don't think the R/C car guys have figured out the performance gains from having the correct ID.

-MikeP

 

[ClayGlover]

hmmm, good point mike. i didn't take the tube ID into consideration. obviously you'll need a good seal at the flange/joint, but i just assumed that the round picco type .12 headers were so similar that they were basicly universal as long as the gasses were contained and the length is tuned properly.

now that you mention it, i'm thinking that maybe a slightly larger/smaller diameter header tube could be compensated for by adjusting the pipe length to give the optimal exhaust system volume? but if other things like exhaust gas velocity are sensitive factors, then it can't be that simple. smaller ID= faster exhaust gas travel :-

i always wondered why many rc car tuned pipe systems were preset, and not easily adjustable...

 

[GTR]

Hi Guy's

The use of big diameter headers for IC cars is driven by the environment they are operated. Eg the nature of the beast which does not rely heavily on the torque of the motor as it has gearing to fall back on. The key element for the use of large diameter headers and very short pipe lengths is the ability to accelerate gases over a broad RPM range. Hence the larger the header the better. Short 21 headers on 15's. Short, fat pipes. Horses for courses.

just my $0.02

GT

 

[TimD]

Hmmmm,

Goes against my test results on side exaust .12 car engines and 21 rear exhaust engines:-

We found the same length header with the smaller id gave more torque and defined band. Might have just been the engines I was using - don't know.

How about someone measuring the exhaust port area - that will be a good indicator of ideal id of the header.

 

[Ian Inverarity]

Tim,

Most of the engines I have measured have a larger area at the exhaust stub than at the exhaust port in the sleeve. About the closest to the same I have measured was the A100, which had an unusually large bore and the same size stub as the A-90.

Do you remmeber the whole time/area discussion on rcboat.com started out from a discussion on the header size of the Mac 21 motors? It was suggested that most 21 headers were oversize, but after all that discussion they only talked about piston ports in relation to time/area, they never related it back to things like exhaust stub and header size.

Nitrocrazed racing: Need more engines to measure.

 

[GTR]

Hi Guy's

I won't pretend to be a guru but in line with what TimD stated a small dia and fixed length probably does provide the most torque in a defined band, it is likely a larger header provides slightly less torque over a greater rpm range. ???

I do think that it also has something to do with the velocity of cooling gases and the ability to scavenge them effectively within a tuned effect pipe. eg 1/4, 1/2 or full wave pipe. I don't pretend to understand the maths behind all this.

What I meant by the gearbox use was more of a torque multiplication effect so that ultimate torque was not the limiting factor. A balance of mass X torque X gearing X RPM - something like that as cars are all about acceleration not terminal speed which is closer to the domain of boats.

As I said, my $0.02 - I never said it was worth more than that. LOL ;D

GT

 

[TimD]

I agree, horses for courses! Cars are all about accelleration - boats about prolonged top speed.

I too don't profess to be anything regarding pipes. I just wanted to share a few little things I found when testing smaller engines. These tests were not just for boats BTW...... cars too.

 

[MikeP]

I got my Sirio in yesterday, the Picco header is too small. It would take some grinding to get it to fit.

-MikeP

 

[Chester]

try to find a thundertiger .21 header, which fit OS15RX and Picco 15