Exhaust Design and Component Selection for Refreshed L26 in a 260z

[stevo_gj]

Hi All!

 

I am about to get my exhaust replaced to suit my reconditioned engine and new headers. My engine is a refreshed L26 with a mild cam and twin 240z SUs.

 

I want to know what to specify for my exhaust system to get a great sounding exhaust note when I open it up that won't drive me nuts by droning all the time.

 

I have read a few old threads (links below), googled around and I have come to the following understanding that will be the basis for my new exhaust:

 

• 2.25" is the best size for a slightly modified L26

• A straight through muffler (AKA resonator) should be placed near the extractors (close to the gearbox) to prevent droning.

• The second muffler (which has the exhaust tip attached) can also be a straight through design.

 

http://www.viczcar.com/forum/index.php/topic,5407.0.html

http://www.viczcar.com/forum/index.php/topic,1395.msg10080.html#msg10080

http://www.viczcar.com/forum/index.php/topic,2153.0.html

 

Magnaflow and Dynomax appear to be two of the big names in this industry when it comes to mufflers.

 

For those interested, Dynomax now supply a new type of straight through muffler called the Dynomax VT that incorporates a butterfly valve and spring that quietens the exhaust at low air flow, and when you give it some pedal opens it up fully. In other words, this design of muffler can be loud when you want it to be. A few threads on various forums mentioned issues that the early designs had with the valves chattering, but apparently these were issues with early models of the design, and the new versions no longer have them. Dynomax also offer to pay for labour and replacement parts if the valve does rattle, which is a good sign. Also it's a lifetime warranty. http://dynomax.com/mufflers.php?muffler=vt I am not really interested in this product for my exhaust, but it is interesting.

 

I have already purchased the ebay headers as per the attached photograph.

 

 

I really like the sound of this engine that Roberto posted, and it seems to be a good example of using two straight through mufflers in a 2.5" system that results in not being too loud but sounding great: http://www.youtube.com/watch?v=Pj4eWW4j3DY

 

I would be really grateful to get some input on the following questions from you guys to to help me achieve the design goals of being not too loud during regular driving, not droning and sounding great when I give it some gas:

 

1. If I was to select two Magnaflow straight through mufflers for the system, should I select two that are the same size, or should the one near the tip be larger/smaller?

2. To select the size of the magnaflow straight through mufflers, I am assuming that I simply pick the ones that have 2.25" inlets/outlets to match the size of the exhaust. But what is not clear to me is how to select the length. The 2.25" in/out has various combinations of lengths (14", 18", 22") and various core sizes (2", 2.5"). How would I select the length and core size?

3.      Should I buy these items from the internet and deliver them to the exhaust shop with instructions, or simply tell the exhaust shop what size and brand I want? Will the brands they have in stock be equivalent in quality?

3.      Any other general comments on exhaust setup for a slightly modified L26?

 

 

[dat2kman]

Do a bit of research on Gonzo mufflers, straight through, course spiral twist around a inner tube, inside an outer tube. It knocks the soundwaves without creating back pressure.

It goes next to gearbox.

Then run a Lukey Turbo at the back

Get some decent headers, try Stew awilkins , or up here, Jack Beavis up Sunny coast way.

 

Forget HM or Perry. Mass produced ones, no attention to detail, but cheap!

[C.A.R.]

Peter Mac uses Magnaflow - same as what Roberto has on his Zed. I can vouch for them as well.

IMHO a straight through in the centre & a dogleg/offset straight-through at the rear

 

Those headers you posed are mass produced junk, Steve.

Spend the extra $ on a set of Stew Wilkins race headers - far superior in design, performance & build quality

Ask Pete to get a price for you...

 

 

[Zedman240®]

Another thing is avoid the "hot dogs".. a straight through pipe gives the same results. Try to get the largest diameter straight through resonator you can fit. That way you will get very little to no droning. The best ones have no protrusions and just round holes on the inside and are fiberglass packed. They absorb all the high frequencies and just let the hot gas expand slowly which is the trick of having a quiet system.

 

And more importantly, find a exhaust place that actually LISTENS to what you want, and not what THEY think works. I've proven one place wrong already near my work.

[PZG302]

Steve,

 

Get some decent headers, Wilkins Motorsport or magnaflow, as recommended by the others.

 

For the system, go to Fat pies in Lawnton and talk to Les. They do very good work at a good price and actually know how to make performance exhausts that work and are quiet. They work on a lot of race cars, both drag and circuit as well as show cars. I have uused them a couple of times for the Zed and will be using them for the Chugger.

[Ledge]

HI

What ever Peter Mc done to Roberto's

DO IT

It Sounds bloody sweeeeeeeet

[stevo_gj]

Hi Guys!

 

Thanks for the responses. So, to summarise:

 

• The headers I bought are poor quality and I should get better ones, even though I am only running a slightly modified L26.
  
• Magnaflow straight throughs give good results.
  
• Lurch recommends a centre centre version in the middle of the system, and a centre/offset version with a tip on the offset. (this matches the exhaust that I took off my car BTW)
  
• I should find an exhaust place that listens to what I want.
  

 

I have PMd Peter Mac and will check the price.

 

I still have a couple of questions:

 

How does one select the length and core size of the muffler? Zedman it sounds like you are saying the biggest possible core diameter will have the maximum reduction in droning, as the flow goes slowly through it (flow velocity being inversely proportional to cross sectional area). Should I therefore pick the biggest core size I can get? Will it still sound good at higher RPM?

 

Assuming I get the better headers, will I notice much of a performance gain over the ebay versions, since I am running a motor that will be not much faster than stock? Will the better ones sound different? I realise that they will probably last longer due to being better made and will have tuned lengths to suit the RPM range that a street car would be operating in, so I guess there will be some gains in that (probably having more torque at low RPM?). It would be good to understand exactly what I am paying for with the better ones.

 

With the magnaflows, any comments on oval vs round designs? It seems like newer exhausts use round ones, while older exhausts uses oval ones. The magnaflow FAQ says there is no real difference it is just for clearance purposes. So selection of the type would seem to be for aesthetic purposes only.

 

I bought those cheap headers months ago, I'm sure they are fine in relation to the stock manifold, just not as good as well made aftermarket headers. I'll see if anyone wants to buy them.

 

Cheers!

 

Stephen

[peter mc]

one like this

[KatoKid]

Pete.

 

What is the diameter of the Magnaflow resonator and do does the system go for ground clearance ?

[peter mc]

no prob mate i made it fit up in the tunnel Heep's of room with a 2.5 inch even with the 3 in there is no prob

[dat2kman]

Stevoget some decent headers, the correct header gasket, get it all and the car up to Les at Fat Pipes Lawnton, ask for thickest wall tubing, tell him it has to meet Lakeside raceway requirements for nose.

Tell him you dont want drone sound.

He has done enough to know what works.

 

You could consider having him dock the 2into 1 outlet, fit a twin flange, and twin pipe it all the way back.

Get a nice note then.

 

I had them do a 13B peripheral Port in my mid engined sports sedan, did the twin longs, into a Y, then into the biggest magnaflow can he could fit.

I thought, this is gonna be noisy, but bugga me, it aint. The twin longs knock a lot of adverse pressure waves compared to the headers your have pictured above.

 

If you really like, i can get in those oh so sexy Kameari Drag headers!

[Zedman240®]

The bigger the resonator, the more time the hot gasses have to expand and cool then travel through the rest of the system before its out to atmosphere. Think of lightning and thunder; once the strike heats up the air very quickly, the sound you hear is the thunder..if the hot air had time to cool, you wouldn't hear anything..but that is impossible but controlling the hot gas from an exhaust is.

[peter mc]

the ones we build have no drone and meet any noise regs in the country some say there to quiet , even on 300hp engines by good parts and you have no problem , magnaflow work

[stevo_gj]

one like this

 

Hi Peter! Those are the ones- cheers!

 

What are you thinking for the headers?

 

Thanks!

Stephen

[peter mc]

I have tryed many pipes and i keep saying the SW pipes work . up to 330hp they work, after they need some work in the merge and sec pipe  but they make torque in the mid range and thats where you need it

[stevo_gj]

Thanks Peter!

 

So to clarify you think I'll see a benefit using the SW headers over using the cheap ebay ones?

 

I've found the website for SW, but can't see any photos of the headers or a price listed. Does anyone have a photo and idea of the price?

 

Cheers!

 

Stephen

[peter mc]

there no cheep but they work  and there made well

[MaygZ]

Thanks Peter!

 

So to clarify you think I'll see a benefit using the SW headers over using the cheap ebay ones?

 

I've found the website for SW, but can't see any photos of the headers or a price listed. Does anyone have a photo and idea of the price?

 

Cheers!

 

Stephen

 

Try here:

http://www.viczcar.com/forum/index.php/topic,4168.msg98434.html#msg98434

 

[stevo_gj]

Try here:

http://www.viczcar.com/forum/index.php/topic,4168.msg98434.html#msg98434

 

 

Thanks for that!

 

I just spoke with Tim on the phone and he is going to confirm the price and lead time for me.

 

He advised that the primaries are 1 5/8", secondaries 2" and the outlet is 2 1/4". On the thread you reference the outlet is 2.5", which means they are not quite the same.

 

For the HPC coated version he said I would be looking at around $620, which seems reasonable.

 

I will update back with the photos that he sends me.

[peter mc]

hahha i think tim  might have miss led you all the ones we have are 2.5

[stevo_gj]

hahha i think tim  might have miss led you all the ones we have are 2.5

 

Thanks Peter. Tim from Stewart Wilkins says that there are two types, and that the 2.5" outlets ones are the high performance ones suitable for L28s and strokers, and that the 2.25" outlet is the one for smaller motors that he would recommed for my application.

 

I just spoke with Les from Fat Pipes at Lawnton and found him to be very friendly and willing to work to my specifications, but also very happy to make helpful suggestions.

 

In summary:

 

• He recommends hurricane mufflers and resonators, as they have an additional layer of steel wool that the magnaflows don't have which increases the life of the fibreglass in the muffler. The hurricane website leaves a lot to be desired in technical information, so I am not sold on this. Can anyone comment on Hurricane mufflers?
   
   
  
• He can do a mild steel system with mild steel hurricane mufflers for $500
  
• He can do a mild steel system with stainless steel magnaflow mufflers for $660
  
• He can do a stainless steel system with stainless steel magnaflow mufflers for $780 - this is my preference
  

 

As he is able to do the stainless steel system for only $120 more I think I will go that route for increased life. Should I be worried about wall thickness?

 

Cheers!

 

Stephen

[PZG302]

If Les says it will work then that's all you need to know, so go with what works best for you keeping with his recommendations.

[peter mc]

do what ever you want mate the hurracane stuff is crap down about 6hp from the magnaflow ones that we use ,, we use them for a reasion ,,, not because we like to run expencive things lol ,

[stevo_gj]

Hi All!

 

Photos of the SW extractors to suit a stockish L26 attached below. The photo shows them coated with heat proof blue paint and the price for them is $420. To have them HPC coated is an additional $300 so $720 all up.

 

It is intersting to compare them to the headers I posted in my first post using the photos.

 

SW Version:

• 1 5/8" primaries, 2" secondaries 2 1/4" outlet
  
• Pipes from cylinder 1 and 6 are taking a relatively shorter route to get to the collector.
  
• Primary pipes seem shorter
  
• Pipes are not very ovalised (not circular cross section) through a better bending technique
  
• Secondaries are relatively longer
  

 

Max Headers (ebay) version

• 1 5/8" primaries, 2" secondaries 2 1/2" outlet
  
• Pipes from cylinder 1 and 6 are taking a relatively longer route to get to the collector.
  
• Primary pipes seem longer
  
• Pipes are a bit ovalised (not circular cross section) from bending
  

 

Really good articles on the functions of primary and secondary sizing and lengths here: http://www.carcraft.com/techarticles/header_basics/viewall.html and http://www.popularhotrodding.com/tech/1111phr_how_to_size_headers/viewall.html

 

Cheers!

 

Stephen

[luvemfast]

Considering you're having a stock ish L26, will it really matter? Clearly not chasing hp, or you'd go L28.

I guess it comes down to price. What's going to give you bet bang for buck?

Maybe cheaper headers and better mufflers will suit you bet?