Hymee

iTrader: (1)

Hi guys,

Someone started a bit of a thread hijack over in our place at the Aussie forum. Some particularly nasty comments were made about glass-packed mufflers, in particular to the systems I have been making availble to RX-8 owners around the world for nearly 2 years.

There seemed to lots of FUD (Fear, Uncertainty, Doubt) being spread about the use of glass-fibre/wool packed mufflers in a rotary engine.

I would like to make an attempt to dispel anyones concerns about this in the RX-8, especially in the "Hymee" catbacks. Yes - there is a temperature at which glass will melt. But lets just be sure what we are talking about here...

The highest EGT's will be seen in the exhaust manifold and the CAT. Right up front. The muffler in an RX-8 is right at the very end of the line, save for two foot long tail pipes. The majoritory of heat has dissipated by then.

The intermediate pipe in a stock RX-8 is 2.5" (in the old units). I use the term intermediate pipe as the one the connects between the rear of the mid-pipe, right up to the rear-muffler assembly.

The "Hymee" catback bolts up to the intermediate pipe, and straight away splits into dual 2.5" pipes, each with it's own 2.5" muffler. So now each pipe/muffler is handling 1/2 the exhaust gas that was traveling through the cat/mid-pipe/intermediate pipe. 1/2 the gas would mean 1/2 the energy, yeah? BTW - 2 x 2.5 inch pipes have the same cross-sectional area as a single 3.5" pipe.

It makes some sense that if we placed a single 2.5" muffler right up close behind the cat (lots of cars have mufflers there) the EGT's could cause problems in melting the glass. I don't believe this is a problem in the RX-8.

Here are some facts that I would like to set out.

• 40,000+ trouble free km on my "Hymee". It is the second one ever made. Wildcard has the honour of being "Numero Uno" and my trusted test pilot.
• My exhaust has seen lots of heat. I posted a long time ago about some problems experienced on a chassis dyno where we didn't put a fan at the rear of the car to carry away heat. Some plastic parts melted, the fuel tank didn't. The mufflers are still OK to this day. I found out later in the workshop manual where they state to use a large fan to ventilate the rear end of the car on a dyno... even with the stock exhaust. I guess experience counts. I have experienced it first hand.
• Many "Hymee's" have done track work. None have had problems. I'm sure I would be the first to know if they had. I've been to more than one outing (including track meets) where there have been more cars with Hymee a catback on them than without.
• The manufacturer of my Stainless Steel mufflers (made specifically for the "Hymee") had been quoted as saying that "glass-packed and rotaries don't mix". I will be getting a comment from the factory as soon as I can.
• The supplier of my stainless steel tips also supplies the glass wool to the factory who makes the mufflers It is a small world in exhaust land!
• One of the bits of FUD mentioned the mufflers only being inches away from the fuel tanks, and a chance of exploding mufflers (glass *****) taking out the fuel tanks. I just measured it. The fuel tanks are in front of the rear axle. The mufflers are behind. The closest they get is 600mm, or 2 feet. And the whole rear axle assembly is in between the two of them.
• It is also a well documented fact that the "Hymee" catback runs cooler than stock, as evidenced by reduced boot/trunk temperatures. Perhaps my mufflers don't get too hot after all.
• My supercharged RX-8 project used a "Hymee" catback. Future devlelopments in the project include headers and an upgraded mid-pipe and high-flow cat.

I'll close with a couple of comments from RotaryGod in respect to this issue. Thanks Fred! Thanks also to Gomez and sco for pointing these out to me.

http://www.rx7club.com/showthread.ph...st#post4646572
http://www.rx7club.com/showthread.ph...st#post1714860

Cheers,
Hymee.

PS - This is the correct place to now "argue" the pro's and con's of glass-fibre / wool packed mufflers.

PPS - I'd appreciate input from my many happy customers Comments based on experience and fact, not FUD.

Ciao

Got a link on fiberglass packed mufflers..A big no no

Quote"
That won't last long. In a few months all of that fibreglass will be gone, so it's lucky they were cheap. You should only ever use steel-packed mufflers behind a rotary. Quote"

Quote
" I'm sure its all melted by now but with the baffles still there it works like a flowmaster type muffler"

Quote
"Yeah, rotaries will melt the fiberglass out due to the extreme heat they produce. Itll be interesting to hear what they sound like then."

Quote
"glass packs will get progressively louder..."

http://www.rx7club.com/showthread.php?t=312668

Interesting to see the bits of fiberglass shooting out of the back of the muffler in the video down the bottom.

Imagine if it was your kid showered with melted fiberglass !!F$#@K that !!

I say again now with even more conviction , FIBERGLASS MUFFLERS AND ROTARIES ...A BIG NO NO

Stainless packed for me I say


BTW the posts mentioned by hymee show support also for Stainless ( in some parts)

BTW .2 there was no thread highjacks in that thread from what I could see

Just an informative view ,, not specifying makers ,just types of mufflers..after all thats what forums are about

Ciao

Dave

Ciao

Dave

Ciao

and another ..This is just with a two secon Google search

QUOTE"Random Tech is the only people that I know of off-hand that make rotary-specific cats. Also, we'll burn up fiberglass packed mufflers too, need mufflers that have stainless-steel packing/wadding."
http://www.dragva.com/forums/archive...hp/t-1039.html

And another ...
http://www.sa22c.org/cat_3/22732/
made my point ..no need to ramble on

Many thanx

Dave

dracoMJB

You keep throwing quotes around without any specifics. Hymee has linked to what seems like pretty good experienced comment about using fibreglass mufflers.

To summarise Hymee's links - if you are using Fibreglass mufflers close to the engine then you will have problems due to the heat/velocity of exhaust gasses. Used as mufflers towards the end of the exhaust while retaining a catalytic converter = no problem.

Gomez

Ciao, did you read Hymee's post on this thread? Did you see him point out that his mufflers are at the end of a long pipe....not up the front bolted onto the headers? Can you understand that a lot of heat has dissipated by the time the gases reach the rear-mounted mufflers? Do real world results mean nothing to you? Does the fact that there have been no failures of a Hymee system over 3 continents and 2 years indicate anything to you?

timbo

I've had a Hymee for over 35,000k -- used in a range of conditions including track. No problems. And, as mentioned, the boot (trunk) is clearly cooler than with the stock muffler.

Also, I am not sure we should immediately adopt all the thinking that arises with the pre-Renesis rotaries. The oil debate is a classic example. And, when I was looking at getting a cat-back, I asked an exhaust professional about rotaries and exhausts, and the one think he said was "beware stainless systems with rotaries, because the higher temps can sometimes affect stainless welds". That was based on his experience.

Finally, I think it is worthwhile bearing in mind the use to which the car is being put. Mine is primarily a road car; any track work is limited to a few occasions and then I would do less than 10 laps per session. This is substantially different to serious drag related activity which seems to be the source of concern in relation to earlier RX's. I must say if I was considering that activity I would probably be considering a substantially different exhaust set-up, end to end

truemagellen

Sorry Ciao but I believe you are full of **** today that video link hasn't operated for quite sometime...

plus relying on a small sample of anecdotal evidence compared to an expert source is foolish...wouldn't hold up in court and damn sure wouldn't hold up in the scientific community (just finished my LSAT :p)

Stop harassing Hymee...he makes great products and we are all greatful for his work.

So unless you have statistically sound or irrefutable physical evidence I suggest you shut your trap.

Gomez

TM, succinct.....as usual .

truemagellen

Hey Gomey how are those ******* change wallets :p

(those poor poor wallabees)





:D

Gomez

I can attest to the fact that there are quite a few 'roos about with high pitched voices....for sure :D .

truemagellen

Hmmmmmmmmmmmmmmmmmmmmm ?

truemagellen

I see...a 'touch of australia' well let me tell you I sure as hell don't want to be touched by an Aussie the next time I visit :p

Ciao

:D Naugthty,, Naugthty,, Naugthty,, Naugthty,, Naugthty,, Naugthty,, Naugthty,, :D

All these personal attacks ..What will I do :D

I researched for some time on what I know is to be right ...Backed up by local and international exhaust specialists

I knew of this link ages ago with the avi .but only made it public after another member made it an issue so G.A.F.Yourself :D

Thanks ( "cheap shots") gomez what you say means so much to me :D

I urge all to search and do their own discovering..But please if you have to ,,by all means take cheap shots at me ..no problem :D

Cant wait to catch up with you in person at the Nats in OZ..

Dave

truemagellen

but the real question is...why are Kangaroo ******** sold EVERYWHERE in OZ! :p :D

Gomez

You haven't responded to any question put to you.....you just fire from the lip.

Ciao

Never seen them .********

Thankyou for all your comments by the way truemagellen !

Much Love

Dave

truemagellen

they even sell them at the airport! Must be a touristy thing :p

just like my cousins who live at the base of Table Mountain in Cape Town, South Africa....many have never visited the top! Said....well one day I guess...it is more of a touristy thing they think :p

Well this week stop by a cheesy tourist trap and pick one up...you can use it for many purposes :p

BUT Vegemite...jeez I had that and almost choked and died when I was there...it is in a tie with hullavah...which is like eating sweaty sand that has been sweetened...gag and barf I say! :D

Ciao

Is that how you feel ..no problem . shoot from the lip Eh

Bring on the Nats :D

Dave

xxup

Try it on slice of bread with butter or on a SAO with butter...

truemagellen

sorry guys...I wanted to fit in with the vegemite there but I wimped out :o

but I sure got a nice Sunburn to match everyone there :p

Hymee

iTrader: (1)

Crikey!

Thanks for the thread hi-jack, guys.

Should have left it in the Aussie forum. At least that way I could edit it :D

Cheers,
Hymee.

sco

All of the links in this thread are referring to RX-7s which have a different port configuration to the Renesis.

I quote pg 60 of the Yamaguchi book ... "The engine's internal exhaust gas recirculation (EGR) has been greatly reduced by the elimination of port overlap. It is now at a level comparable to that of a typical piston engine , stabilizing combustion in low-load operations such as idling."

I suspect that this will result in a reduced exhaust gas temperatures in the RX-8 compared to the RX-7.

dannobre

iTrader: (3)

^^ could you please explain that ?? What is the relationship between port overlap and EGT ?? The Yamaguchi quote is refering to the leak back of the exaust gas being similar to a piston engine in the 8................ie..compared to previous rotaries where this was a problem.

truemagellen

I think you should close this one up and leave it in the Aussie forum