added a Hushpower resonator...

[haiku88]

Elv15 at the Calif. Caterham forum posted a link to a Blatchat thread http://blatchat.com/t.asp?id=145840&pn=1&ps=15&c= that detailed how someone added a second muffler and had good results. I decided to do the same as I wanted my car quieter and also want to autocross it with a local club that has tight noise restrictions. I used a Hushpower resonator and it fits well under the back of the car and should be fairly unobtrusive once I paint it and the plumbing flat black with BBQ paint...actually with the plate and spare installed it is partly hidden already. The noise level is way down, tone is much deeper, and now the intake is actually louder from the drivers seat...but the car still sounds good when I get on it. FWIW the primary muffler is also a Hushpower. Power feels about the same by seat of the pants...

Tried to add a photo but it won't take for some reason, upload goes but shows as 0 bytes in the upload directory:banghead:

 

edit:-picture fixed

 

 

 

 

 

 

 

http://www.usa7s.com/aspnetforum/upload/972583829_resonator.jpg

[MHKflyer52]

That looks quite good.

Looks like you did not loose any ground clearance at all.

I like the color of your car.

[slngsht]

The picture upload problem was my fault... we were out of storage capacity. More added.

[haiku88]

The picture upload problem was my fault... we were out of storage capacity. More added.

 

thanks very much, it uploaded ok today...also FWIW did not lose any ground clearance as Martin observed, other parts of the car are lower and since the case is insulated I was able to safely mount it close to the body

[Winston]

Ack! Hot exhaust tip right below fuel filler! Danger Will Robinson, danger! :willy:

[haiku88]

Ack! Hot exhaust tip right below fuel filler! Danger Will Robinson, danger! :willy:

 

ummm.....no....not nearly hot enough, the exhaust is cooled down considerably after passing through two mufflers, can touch the tailpipe briefly after a long drive

MUCH higher temperatures are required to ignite gasoline, see

http://tinyurl.com/6r4aap

[Winston]

 

ummm.....no....not nearly hot enough, the exhaust is cooled down considerably after passing through two mufflers, can touch the tailpipe briefly after a long drive

MUCH higher temperatures are required to ignite gasoline, see

http://tinyurl.com/6r4aap

 

I understand that; I am concerned about the ignition of gasoline vapor, not the liquid gasoline. With the horizontal orientation of your tailpipe and its position almost directly below the filler, It is possible to get gasoline vapor to flow *inside* the exhaust pipe during refueling, which can then be ignited further up the exhaust tract (especially if you have a catalytic converter).

 

Take a look at this abstract for a research paper published in the Journal of Applied Fire Science:

 

FLAMMABLE VAPOR IGNITION BY ENGINE EXHAUST SYSTEMS

 

GREGORY J. HAUSSMANN A1 and LAWRENCE M. MATTA A1

 

A1 Exponent Failure Analysis Associates

 

Abstract:

 

Gasoline spills during the refueling of a hot engine creates a fire hazard. A unique hot surface ignition mechanism has been discovered involving exhaust systems on hot, shut down engines. The present research involves small engines up to 45 hp that operate at relatively high tailpipe temperatures. Although exhaust temperatures in excess of 700 C were common, external surfaces were found to be incapable of causing ignition for the conditions studied. After engine shutdown, however, a buoyancy-driven flow pattern was discovered in which gases enter the exhaust pipe. Heating of flammable vapors drawn into the exhaust pipe resulted in ignition, even though ignition was not possible on external surfaces. This ignition mechanism exists when the tailpipe discharges upward or horizontally, but was not observed in downward facing configurations. For ignition to occur by this mechanism, an exhaust diameter of 3.8 cm or greater and a temperature of 550 C were required.

 

(Unfortunately, I don't have an account to get the entire paper.)

 

Granted, the engines upon which the research was performed likely have higher exhaust temperatures than your typical Se7en engine, but the presence of a catalytic converter (not sure if you have one) would provide a ready ignition source in the 550+ degC temperature range.

 

Now, I'm not saying that this is a *likely* scenario, but I think that it is possible. It just struck me as a danger when I first saw it.

 

 

Source:

 

http://baywood.metapress.com/index/0ENW464057AMJ92V.pdf

[haiku88]

no catalytic converter, and vapors could enter the tailpipe from spilled gasoline if it were on EITHER side....if this was something that happened with rear exhaust Sevens (or rear exhaust cars in general) it would probably be common knowledge...but thank you for sharing your concern :7fume:

[Winston]

no catalytic converter

 

That's good. That alone probably eliminates any chance of ignition since gasoline vapors need about 1000 degF to ignite.

 

vapors could enter the tailpipe from spilled gasoline if it were on EITHER side

 

Theoretically, yes; however, since gasoline vapors are heavier than air it is a lot more likely when the tailpipe is directly below the filler. And I'm not talking about spilled gasoline so much as the vapors that can cascade out of the filler neck when refueling. Even Stage II vapor recovery units don't capture 100% of the gasoline fumes generated.

 

if this was something that happened with rear exhaust Sevens (or rear exhaust cars in general) it would probably be common knowledge

 

I think this event would have to be exceedingly rare. Anyway, :_deadhorse: I doubt you'll have a problem. The setup looks really great, and I'm glad to hear that it made a difference in noise level. Thanks for sharing. Do you happen to have a part number for the resonator, or does Hushpower only make one model?