3x2 exhaust query

[g72s20]

Hi there,

With respect to the L 24--> L28 engine, if the exhaust system is set up as two separate pipes from headers (3 into 1, times 2) to outlets,does this pose any tuning issues? The induction is 3 x2 choke dcoe sidedraughts. The reason I ask is any factory system I've seen with twin exhausts seem to incorporate a single(common to both pipes) muffler somewhere. Anybody got any technical experience of this setup? or can advise on what I should be considering?

Thanks guys!

Jim.

[beandip]

I ran duel pipes years ago on a inline 6 and found that if the two pipes were interconnected part way back that it helped with the resonance and back rap when decelerating when down shifting. Now this was with just glass packs Bullet type mufflers. As far as tuning I dont remember any problem either way. the inter connection can only be a single section of tail pipe welded to simply connect the two pipes.

[g72s20]

Thanks for the reply Gary,

The background on this is; I had a '66 Prince Skyline GT, original exhaust was twin system ending in one common muffler with a twinpipe out. After a mild cam upgrade this was changed to a "hotdog" muffler in each branch as in intermediate muffler, I think these are the same as your straight through glass packs, ending in a separate larger muffler for each branch....absolutely glorious sound, very ferrari like on the right road, you know ...6800.. change!, 6800..change! My next project I would like to get as close to the same sound, but as i said earlier I haven't seen any modified systems on the L series that run two completety separate pipes out the rear. This got me thinking there may be issues that make it necessary to join the two pipes into one at some point. Your notes on resonance and back rap (good description!) are definately food for thought. Now I wonder if the fact my earlier system had mufflers right on the end of each branch helped reduce the effect to something acceptable. I know I'm just gonna have to try it and see! But please...any and all comments, advice will be welcomed.

Jim.

[ecp48]

g72s20

If you look at old catalogs from almost every supplier, Sharpe, BRE, even MSA today; they all had a two/twice pipes system. Datsun Competition listed it as well.

Don't have my old Datsun Competition catalog handy, or I'd provide the numbers. The MSA 10th Anniversary edition catalog show them on page 44, 70-78 Z with headers was 15-6030. There were three other parts numbers for various years stock exhaust manifolds.

The Datsun system was listed as competition only and came with the glasspacks or straight pipes (from a failing memory).

Noise/glass packs and a modern trend toward 2.25 and 2.5 turbo type exhaust systems has displaced their popularity.

ecp48

[symon]

I thought that a doble exhaust system would sound nice & be powerful. Have a quick look at my gallery for a few photos.

http://www.zclub.net/gallery/showgallery.php?cat=500&ppuser=1011

[g72s20]

Interesting fact about the cattledogs..it would suggest as you do ecp48 (wassat?), that noise was the issue with a twin pipe street system.Thanks for that!

YES!..well almost Symon, that shiney system in your gallery is almost the same layout as the old Prince GTB, without the collector at the front.

I just gotta try it!

..Oh , while I think about it Symon, remind me to send you some Silvia pics and info I've gathered. There may be something amongst it you don't already have.

Cheers,

Jim.

[Phred]

This is how I did it. The header is made by Stahl. It was made with 1.5 in. primarys, and a two inch collector/ tail pipe size. This was sized for a 240, but I'm going to run it on a 3.0 L-motor for vintage, track fun, and street mayhem. As Gary mentioned, a crossover/conector pipe can be seen installed in front of the muffs. The muffs exit at the diff. I have 3 inch ID short race muffs acting as resonators which exit at the stock location. The two pipes are only connected at the crossover point. Great sound. All bends were cut fron mandrel tubes and heli-arc welded. The muffs lay up close under the drive shaft, and the car can sit low with no road rash.

Phred

[beandip]

Phred, that's a hell of a systime . Looks like you did a lot of work to keep the plumbing equal in length . How is the sound with the glass packs , I know you said great sound , but for a race car or for a street driver . I dont want to be setting off a bunch of car alarms ! Great looking set up , I hope to see it soon. Gary

[symon]

Hi G72s20,

The exhaust I made from 2 RC40 systems that are sold by Mini Spares in the UK. I´ve calculated that there should be no powerloss up to 260 hp ! The car certainly pulls a lot harder & sounds great but not too loud. & took a whole weekend to make !

& a quick reminder to send all the Silvia photos that you´ve got !!!!! Feel free to send large files to symon@csp311.com . Do you like to e mail address ?

[ecp48]

Phred,

As usual Stahl makes a super looking header! I didn't know they made one for the L6 Z.

Is there any benefit to mounting the glass packs in the center of the system rather than at the end like the twice pipes?

I had thought of installing a resonator in the center and leaving my glass packs at the rear. Any thoughts? The crossover you installed is what I'm planning, only a little closer to the header.

ecp48

[g72s20]

"I'm going to run it on a 3.0 L-motor for vintage, track fun, and street mayhem"

My intentions exactly!! You can see why those 'glass paks were called "HotDogs" down here in Oz.

I like anything that turns money into noise!!