USAC Racing Forum
September 20, 2014, 10:05:15 PM *
Welcome, Guest. Please login or register.

Login with username, password and session length
News: SMF - Just Installed!
 
   Home   Help Search Login Register  
Pages: [1]
  Send this topic  |  Print  
Author Topic: Which exhaust pipe for Honda?  (Read 3767 times)
Kendall42
Veteran
**
Posts: 92


« on: February 14, 2010, 10:31:26 PM »

OK...we talked about which bumper is best, now can we get some feedback on which exhaust is best?  And why?

I have been running the S pipe on both 120 and 160 motors.  But I have one of the C shaped pipes that just loops and comes out toward the right rear.  The C pipe is obviously shorter.  One of my S pipes came off the flange at an angle to match the angle of the exhaust port, the other does not.  The one S pipe has an ID of 2 CM, the other has an ID of 1.8 CM.  The C pipe has an ID of 2 CM and pipe is angled on flange to line up with angle of port.  I have been running the smaller ID pipe on the 120 and the larger ID pipe with angle on the 160.  Thinking about putting the large ID S pipe on the 120 and the large ID C pipe on the 160.

I am open to any thoughts or input.  Anyone ever play with the pipes on the dyno to see if the flow vs back pressure affects HP, torque, power band, etc on these little motors?  Or does it not really matter?  I warp all my pipes too with header wrap...if for no other reason then to keep the burns down when I have to work on them while still hot. 

Thanks!
Logged
sfreitas20
Triple Crown Champion
*****
Posts: 525



WWW
« Reply #1 on: February 15, 2010, 08:02:13 AM »

I have heard conflicting information from various builders.  I have heard some builders say to run the 7/8" pipes on your 120s and the 1" pipes on the 160s, but then I have heard other builders say to run 1" pipes on both as they are better on the dyno.  Same goes for the "C" vs "S" pipes...heard it both ways.

Will be interesting to hear what others have to say on this one too...probably just going to muddy the water even more. Smiley
Logged

Scott Freitas
Patriot Motorsports Inc.
animalman
Rookie
*
Posts: 15


« Reply #2 on: February 15, 2010, 09:50:53 AM »

Just remember if you ran a 1/2 inch pipe or a 3 inch pipe it still has to exit out that wonderful restrictive B&S muffler !
Logged
Swartz
Feature Winner
***
Posts: 200


« Reply #3 on: February 15, 2010, 11:01:51 AM »

1. Cam overlap
2. Expansion Chamber
Logged
Kendall42
Veteran
**
Posts: 92


« Reply #4 on: February 15, 2010, 10:05:38 PM »

sfreitas20-  I had heard the same thing...that is why I had the smaller pipe on the 120 and the larger ID on the 160.  But I came across this C pipe that is 1 inch when putting motors back in (it was amongst my shelves of parts I know we all collect!) and I kinda went "Hmmm, I wonder if the big  ID C pipe would be better then these S pipes?" 

I am interested in what ANYONE has to say on here...may take some with a grain of salt, but some I am sure will be good.  I just know that in the big car stuff we used to use step headers to help with torque, etc.  I used to play with headers from stepped to 180 degree to straight dumps.  I used to love the sound of those 180's!  Sounds like a V6 even when bolted on a big 421 CID motor!

Brad
Logged
Kendall42
Veteran
**
Posts: 92


« Reply #5 on: February 15, 2010, 10:07:24 PM »

Swartz- Can you elaborate for me?  I think you are making a good point that I need to consider.  But not being a small engine guy, I need some more detail. 

Thanks!
Logged
Swartz
Feature Winner
***
Posts: 200


« Reply #6 on: February 16, 2010, 10:59:06 AM »

I'll try. The exhaust system on these things is the pipe, a tank, and the muffler, a relief valve. The whole system is a controled leak of the exhaust gasses. On the smaller or restricted engines where the muffler can allow the passing of enough exhaust gasses wraping the pipe to keep temperatures up and enhance velocity is good. On larger displacement engines, since the muffler (valve) is restrictive using a larger pipe (tank) gives more expansion room and volume to fill. Using a longer pipe gives the gasses time to cool and reduces the volume. That, and if you use a step up from the manifold to the pipe, helps with anti revision and smother flow creating a draw on the intake at valve overlap helping pull more frsh air and fuel into the combustion chamber. Or, you could do like some, dissasemble the muffler and drill all the baffle holes out a couple thousandts. Next time a noisey muffler jumps off a car for no apparent reason make sure you get a chance to look at it. I cant believe no one has ever insisted on checking the hole size in the baffles of these mufflers with a wire gauge.
Logged
Kendall42
Veteran
**
Posts: 92


« Reply #7 on: February 16, 2010, 06:50:10 PM »

FYI...I talked to Ziggy today because he does my motors.  His input is that after testing many pipe configurations and wrapped vs not wrapped...there really is no noticeable gain or loss on the dyno.  So...I guess we can all have our theories but with such a low compression low HP motor, not sure if it matters.  I still believe bigger is better?  So I think I may opt for the larger diameter pipe and I also believe that the port angle matching the pipe angle must have some affect...the less that air flow is disrupted by running into a pipe wall, the better.  Just laws of physics in my opinion. 

I have to agree...that muffler is the negating factor anyway.  I always wondered why some cars had more of a cackle to them with these little Honda motors.  Now I know.  Is there a written rule on the mufflers other then to call out the part number? 
Logged
Swartz
Feature Winner
***
Posts: 200


« Reply #8 on: February 16, 2010, 07:56:42 PM »

Dyno numbers are a good benchmrk but I can prove it is imposible for bumblebees to fly in a lab. Real world wins. I think the rule does give a part number from Briggs but it also says "or suitable replacement" or something. Never used them but if you go to TSC they sell a replacement muffler that is identicle, except, it has twice as many holes in the baffle spaced closer together.
Logged
USACRULES
Rookie
*
Posts: 31


« Reply #9 on: February 17, 2010, 02:32:32 AM »

Quote
Or, you could do like some, dissasemble the muffler and drill all the baffle holes out a couple thousandts. Next time a noisey muffler jumps off a car for no apparent reason make sure you get a chance to look at it. I cant believe no one has ever insisted on checking the hole size in the baffles of these mufflers with a wire gauge.

What Rule Book Says:

723 Exhaust
A. Exhaust systems must be designed to create a minimum fire hazard and a
minimum hazard to other competitors.
B. Exhaust system must extend outside of engine housing.
C. Exposed portions of exhaust system must not be higher than the rear tire.
D. Exhaust system must not extend outside of a straight edge extended from
rear edge of rear tire and rear of the rear bumper.
E. Exhaust systems facing forward must not extend outside of nerf bar.
F. Drilling holes in the baffles is prohibited. Inside seam of baffle must be straight,
although seams may not be parallel in baffle) A nut or washer welded onto
muffler flange is allowed for safety wiring.

G. All classes must use a tailpipe and muffler combination
conforming to technical manual specifications. Muffler must retain the threaded
flange on Honda exhausts.
H. Clamps should be positioned with screw adjustments, bolts and excess strap
material facing inboard when possible.
I. Exhaust system must be intact at scales. If any part comes off during race and
not replaced before the checkered flag the car will be disqualified at the scale. No
repairs after checkered flag is waved.
J. All exhaust must pass through the mufflers.
Logged
Swartz
Feature Winner
***
Posts: 200


« Reply #10 on: February 17, 2010, 10:27:24 AM »

Yeah, that's what it says but it does not say anything about enlarging the holes that are already there nor have I ever seen anyone check them.
Logged
Kendall42
Veteran
**
Posts: 92


« Reply #11 on: February 17, 2010, 01:17:49 PM »

Oh crap...looks like a can of worms has been opened!  Or maybe just a grey area exposed. 
Logged
sfreitas20
Triple Crown Champion
*****
Posts: 525



WWW
« Reply #12 on: February 17, 2010, 02:09:04 PM »

There is no gray areas according to the Tech Director, so I would say this is more of a can of worms. Wink
Logged

Scott Freitas
Patriot Motorsports Inc.
Swartz
Feature Winner
***
Posts: 200


« Reply #13 on: February 17, 2010, 04:09:01 PM »

I wouldn't worry about it. It can do more harm than good. The best thing quarter midget racing could do is abandon the whole notion of "box stock" unless there is a seald engine program. I don't know how many engines I've seen go through tech that had the absolute largest or smallest dimensions as provided by the rules. No way those engines came off an assembly line. They do cost around $1200 but it would be a lot cheaper if the work was not considered cheating. No, I didn't have one.
Logged
Pages: [1]
  Send this topic  |  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.18 | SMF © 2013, Simple Machines Valid XHTML 1.0! Valid CSS!