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Edward the Elephant's New Exhaust - Part 2

The story of one elephant and his exhaust

By a Frederick Witherspoon

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This article was first published in 2000.
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Last week we saw how Edward the Elephant was severely taken for a ride when he bought Georgina's Nissan EXA turbo. He'd been expecting a quiet, powerful, grunt machine - and instead he'd been saddled with an excruciatingly loud grunt machine. An inquisitive elephant, Edward had looked under the car - only to find that a whole section of the exhaust was missing! After spying that terrible sight, he'd decided to visit Mr Mark's workshop to get a completely new exhaust fitted - but there was a major problem. Having spent all of his peanuts on the car, poor Edward was broke...

What was he to do? Last week we saw how Edward flow-tested a heap of used OE mufflers that he'd discovered out the back of Mr Mark's workshop. He'd tested and tested until he had found thee best. And now? It's time to fit those mufflers to the EXA. Will Edward finally get to be a happy elephant?

The night before Edward's appointment at Mr Mark's, the elephant had given some considerable thought to his new exhaust.

"Florence," he'd said to his long-suffering lady elephant, "I think that I'll get Mr Mark to use quite a lot of press-bends in this new exhaust system."

Florence had looked disinterested. (Perhaps his apologies over the absent vacuum cleaner had not been effusive enough - maybe some chocolate-coated peanuts would do the trick? But where was he going to get those at this time of night, especially when his noisy, noisy EXA attracted police attention like a rogue bull elephant in a hotted-up 350 Monaro doing donuts around the McDonald's carpark?) Edward's thoughts of the loud EXA brought his wandering mind back on track, "And perhaps just a few mandrel bends up the front near the turbo," he belatedly finished.

"Oh yes," muttered Florence.

"You see Florence," said Edward, "lots of elephants believe that mandrel bends flow heaps more than press-bends, but that's not actually the case. In bends of less than 90 degrees, the difference isn't much at all - but the cost is. Mandrel bends are really expensive," he finished off.

"Really?" said Florence, riffling through the TV guide.

"So I reckon a mandrel off the turbo and another straight after it, then press-bends for the rest of the system. All in two-and-a-half inch tube."

"Well, we have either Backyard Blitz or The Simpsons, dear."

"In fact," continued Edward imperturbably, "the Holden muffler and resonator that I flow tested with such good results aren't even two-and-a-half inches; they're probably two-and-a-quarter."

"I always think that the backyard makeovers aren't really done as cheaply as they say. Anyway, there's no point in getting any ideas for our backyard - look at the mess you make out there wallowing around in those mudholes you dug! "

"And the idea that the bigger the tube size, the better the muffler flows is another furphy - some of those mufflers with larger diameter tubes flowed worse than mufflers with small tubes. So I reckon that the flow will be fine, even with plenty of press bends and the two-and-quarter inch mufflers. We'll see...."

Edward stirred himself. "Now darling - what were you saying? Why don't we watch Backyard Blitz tonight - they have a story on putting in swimming pools...."

So when the elephant arrived at Mr Mark's, he had a pretty clear idea of the exhaust he wanted - all in 2.5-inch tube, mandrels off the turbo, a flex joint, the straight-thru Holden resonator, then the large rear Holden muffler. And you know what? Edward was just bubbling over with excitement!

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The first job was to remove what was left of the old, broken exhaust. Edward helped Mr Mark do this - Edward was never a precious elephant, afraid to get his hands dirty.

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Mr Mark had suggested that instead of using mandrel-bent bends off the turbo, it would in fact be even better if they used a donut. Edward was pretty excited by this news - he likes donuts - but when he tried taking a bite, he found that Mr Mark had just been fooling with him. This wasn't a donut at all!

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Mr Mark grabbed the donut back from Edward, looked crossly at the tusk marks, then used a friction saw to chop it up, one piece for the section off the turbo, and the other for use at the base of the dump pipe.

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He then used a hydraulic press and differently shaped mandrels to force the inside of the tube to nearly match the inside shape of the new flange that was to bolt to the turbo outlet. Mr Mark was very proud of the fact that he did not have to use a gas flame to heat the inner part of the pipe before he changed its shape - taking this approach reduces the embrittlement of the metal, he told Edward the attentive elephant.

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After the first section of pipe had been made, Mr Mark placed a high quality flexible coupling in the exhaust. "Never use truck-flex," he sternly said to Edward. "Had a bloke here a few years ago who insisted on using it, and guess what happened?" Edward shook his big head wordlessly. "It broke after a year, that's what happened!" said Mr Mark. He trailed off grumpily, "I told him it would...."

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With the first section of exhaust built, Edward came close to check it out. It looked good! In fact Mr Mark had wanted to grind back the welds and spraypaint the pipe black - but Edward wouldn't let him. "Only bad workers cover up their welding," he told Mr Mark who looked astonished at this compliment before replying "Ain't that the truth...."

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The new section of exhaust was so nice that Edward just wanted to hold it. He admired the custom flange (now with the inner pipe perfectly matched to the ID of the flange), the donut bends, flex joint, first press bend and the second flange. Edward wanted to take it home to show Florence, but Mr Mark said it should really be bolted to the EXA.

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One point that Mr Mark earnestly made to Edward was that, to get best resonance and vibration suppression, big rubber hangers that still allowed some fore-aft movement should be incorporated. "Cost the same," he said to a very close elephant, "but work heaps better than the old ones."

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As Edward had requested, the rest of the exhaust was to be made with press bends. Edward watched Mr Mark making some of these bends using a big, expensive machine. Mr Mark had obviously been doing this for a long time, but Edward figured that the poor human was confused. Why use a big machine? Perhaps it was just that Mr Mark wasn't strong enough?

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Edward , er, 'borrowed' a piece of pipe from a nearby bin and decided to do some bending of his own. A big strong elephant - all those Weetbixes that Florence serves up each morning - he bent that piece of tube just perfectly. But did he show Mr Mark what he had done? Nope, being a thoughtful and caring elephant he didn't want to make Mr Mark look silly - "Just let him keep using that stupid machine," thought Edward wisely.

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But then disaster struck! No, not Edward temporarily getting his trunk jammed in the candy machine (though that happened too) but the news that the resonator wouldn't fit! The resonator was from the centre part of the Holden system that Edward had so laboriously flow-tested, and Edward had been sure that the resonator would go under the EXA without any problems. But it was not to be. "Don't need it anyway," said Mr Mark. Edward wasn't so sure - he so wanted a quiet system.

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Finally, they were nearly there. The huge Holden muffler was put into place ("Too big," muttered Mr Mark, "let me put on one of my small stainless ones") and then it was time to choose a secondhand exhaust tip.

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Edward looked through the rack of secondhand mufflers (lots were shiny aftermarket ones, which is why he'd not been looking in this area previously) until he found a big, oval, chrome tip. "Haaah," he chortled to himself, "looks like it's off a 200SX!" Mr Mark looked askance as Edward brought it over, but by this time the elephant was getting very excited and couldn't be deflected from his task. It's a bit hard to deflect an elephant....

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And then it was done. Edward and Mr Mark posed for a celebratory picture before Edward took the car for a test drive. Aaaaaah, the quietness - but not too quiet. Without the centre ressy there was a little rasp, but the noise level was dramatically lowered over having no mufflers at all.

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Edward used his noise meter and measured 88dB(A) at the tailpipe at 3000 rpm. But the decrease in noise to Edward's sensitive ears was much larger than that - no more head-shattering resonances, no more pops and bangs and roars. Just that little rasp - and a lot of engine tappet noise.

Tappet noise?

"Where's that bloody Georgina?!" bellowed Edward.

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Footnote: Testing showed that the exhaust flowed so well that there was no performance penalty over having only half an exhaust and no mufflers. The 0-100 time was measured at 9.5 seconds - actually a little better than recorded with the exhaust-less car.


Exhaust Technology

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