3" single exhaust instead of duals

[Anonymous]

Hell, Dean, I AM the village idiot!

Okay, I'm going to hunt down those books of Vizard's. The two books of his which I have now are great reading. It's great to get the ideas of a man who has spent his life on a dynamometer, getting hard results.

Interesting about the thermotape overheating exhaust valves. Two-stroke tuners who build sled engines report that they leave the thermo-tape off of the first several inches of the expansion chamber so that the reverse pressure wave that supercharges the cylinder doesn't pack it full of hot air. Of course, wave action in a racing two-stroke bounce-pipe (as we called 'em long ago) is pretty emphatic as compared to what goes on in my cars. In fact, I'll make a question of that: does any part of a street car exhaust system (a good system, with street headers) have an effect on wave action beyond the point where the pipe empties into the first muffler or resonator or cat? Seems to me all you'll have is one fairly weak negative wave working its way upstream. Actually, I'd think you want any wave action in a normal street car exhaust to be weak, mixed up, and confused; why would you want the power peaks and dead spots that pulse-tuning brings unless you're racing?

Hey man, I can babble along with the best of them . . . we all oughta be in a bar somewhere, slamming Buds!!!

 

[wsa111]

X, I have to agree with you on the benifit of the exhaust crossover or better yet the X pipe. Working at a lexus dealership all our inline 6's use an x pipe or a single pipe after dual headpipes, then to a dual exhaust 2 muffler outlet. This gives the benefit of more torque, power in the midrange & better yet the SOUND of a dual exhaust system.
I am about ready to assemble my engine after a piston change,camshaft,cylinder head & the addition of a dual outlet header made by hooker #6601 which can be purchased from FSPP. I will use a 2" pipe from each outlet to a X pipe then to a 2" dual exhaust system.
I'm sure the headers with the rest of the system should sound great & have the torque & horsepower to prove it. Can't wait to get this project done. William

 

[xctasy]

After having seen IS 300 machines haul but, I'm kinda interested in how peach your long pipe beast will be. Delayed gratification is at once the sweetest, and most anaonsing aspects of car work.

If a basic piece pipe of Americana is put together with the love and care the old Lex Luther Toyoda, it will run forever, terrorising ricers with a 105 year old Will shutting 'em down in 2070.

 

[6bangerbill]

Thought it might be interesting to look at header system for a typical hot hot rod 300 engine for comparison to those off the shelf offerings from aftermarket manufacturers. So I inputed the following big six specifications into my engine pro software just for jolleys:

cam-268 comp cams w/218 deg @ .050, hydraulic flat tappet
head- ported w/1.94 d intake, 1.5 exhaust,226 cfm @ 28"
compression- 10.5 to one
intake- stock efi long runner
hp-267 @ 4750 rpm
torque-342@ 3650 rpm

The results were as follows:

Primaries- 45" long, 1.625 id.
Collector- 3 1/4 dia.

This is probably pretty close for a long runner efi intake ( over 20"long runners, 1 5/8 id) intake manifold. A 4 barrel manifold would be difficult to analyze because of un equal runner lengths.

 

[Anonymous]

I just got a quick glance at it, but there looks to be a pretty good basic article on exhaust systems in Popular Hot Rodding, May, '05.

 

[6bangerbill]

Very informational article Smitty. First time Ive seen numbers derived on collector diameters and collector lengths. For the previously defined street engine, I get a 2.84 dia and about 24 to 25 " long for collector specs for peak hp even longer for peak torque. This compares to the 3 1/4 dia previously given by my program. The closest size mufler entry size is 3" dia. about halfway between both figures. Your PHR article also defined muffler choice based on flow and type based on desired back pressure and effective collector length. This article points out the lack of good after market headers for our favorite ford six. It seems home built is usually the best option.

neat stuff
bill

 

[Anonymous]

What I noticed, Bill, (and I have to get a copy for myself), was that even a good aftermarket performance muffler they tested would only flow about 315cfm. I guess this pretty well answers the question about dual exhaust, though it doesn't say anything about why MerBenz and others run dual pipes thru single mufflers.

 

[wallaka]

Hmm...yeah for n/a engines the exhaust gas velocity is very important for low- to mid-range torque, however if running a turbo or supercharger, or even nitrous, peak flow is king. That is why all of the high-end Japanese sports cars (Supra, Skyline, etc) all run big single exhausts...all of these cars run ~2.5-3 liter turbo sixes and make above 300 hp stock, and can easily make over 500 with little modification.

 

[6bangerbill]

My thoughts with a space limited under floor board crowd is modifying a flowmaster type thick wall header muffler by welding on an additional 3" inlet for the second header collector and running a single 3" tail pipe to the rear. Be careful to extend the collector length for your desired rpm range and use the muffler as a plenum chamber per smittys article in HR mag. I can only imagine the sound! The Borla muffler probably has less back pressure but the noise may rack your brain in about 30 min of highway cruising.