Exhaust Question

[Knock-on]

I'm a Confessed muppet on anything after fuel exploded and have (probably) a silly question.

 

After the manifold and 4 into 1 collector, what must happen to the gasses to get optimum power.

 

I'm thinking of buying a stubby end can and finishing it just after the collector so it's easier for the passenger to get out without leaving horrible skin marks smoking on my existing can. Fortunately the cans quite load so it drowns out the screaming but the odour of burning fiancé is still rather unpalatable.

 

So, are there any considerations or consequences to performance by shortening the pipe and fitting a stubby can?

[Knock-on]

Sorry, can a Mod change the title to Exhaust and not Zest. Bloody auto correct!

[tractor]

no loss of performance it will just be louder

[tractor]

wot this short

[tractor]

ended up this long cos it isn't any quieter but because of its position there is less noise into cabin area

[Guest ali2992]

well there would be a loss of performance, but it would be negligible and I doubt you'd notice.

[Guest 2b cruising]

Bloody selfish passengers. A chrome or polished stainless heat shield usually cures the need of repolishing your exhaust. It still gives off a nasty painful reminder to your inconsiderate passengers and teaches them a lesson in consideration to other people's possessions without you having to put up with horrible smells their body makes, and requires no cleaning off of you nice shiny exhaust pipes.

Also as tractor said. " it I'll be a lot louder in your cabin. Fun to start with but awfull after any long periods.

[Dave R]

title altered....

 

you will find most people only burn their leg the once

[Guest 2b cruising]

title altered....

 

you will find most people only burn their leg the once

very true but still leaves a mess on your system. They also blame you so won't clean it off. Bloody cheek.

[Snapperpaul]

To calculate correct exhaust header length you have to understand the harmonics caused by the cam opening and closing incidents

To proper calculate you also take into account the intake runners from trumpet the valve head

I had a guy on Turbosports forum calculate for my Pinto and the standard manifold did well, collector needed lengthening a bit and distance to the can then end of pipe cam out quite well

 

 

Re: Manifold calculations

The output from the second program gives me the following lengths

 

32.8" primary pipe length

38.5" inches to end of exhaust pipe

 

Primary diameter = 1.5"

Main exhaust diamter = 2.5"

Tuned Inlet length = 13.2" 335mm

 

The measurements in both messages are from the manifold face and not to the valve.

The secondary pipe length is very important when developing power and should be considered as nearly as important as the primary length.

 

Edited January 30, 2015 by Snapperpaul

[Snapperpaul]

This is the more complex set of calculations and shows the different harmonics that you can utilise

I was most greatful to Tom from Turbosports for the complex calculations and had my manifold, collector and exhaust modified to suit.

I confess I erred on the large and have a 3" pipe

 

--- Single Primary Pipe Specs --- for 127.723 CID from 5100 to 7600 RPM

Diameter= 1.487 to 1.612 Length= 29.9 to 32.2 inches long

 

--- 2-Step Primary Pipe Specs ---

1st Dia. inches= 1.487 Length= 14.9 to 16.1

2nd Dia. inches= 1.612 Length= 14.9 to 16.1

 

--- 3-Step Primary Pipe Specs ---

1st Dia. inches= 1.487 Length= 10.0 to 10.7

2nd Dia. inches= 1.612 Length= 10.0 to 10.7

3rd Dia. inches= 1.737 Length= 10.0 to 10.7

 

--- Header Collector Specs (Conventional Straight Tube) ---

Diameter= 3.010 Tuned Lengths= 16.5 best and 8.2 or 32.9

 

-- Total Exhaust System Tuned Lengths (Primary ends to TailPipe end) --

Best HP/TQ Tuned Collector Lengths= 16.5 , 32.9 , 65.9 , 131.8 inches long

 

Worst HP/TQ Loss Collector Lengths= 24.7 , 49.4 , 98.8 , 197.7 inches long

 

Note=> measured from where the Primary Pipes end inside the Collector to

the point the tailpipe exits into the atmosphere.

 

Note-> all Pipe Diameters are OD and based-off .0625 inch Pipe thickness

 

---- Primary Pipe's Harmonics ----

1st Harmonic = 129.6 inches long ... typically never used

2nd Harmonic = 49.5 inches long ... longest recommended

3rd Harmonic = 29.9 inches long ... highly recommended , best Torque Curve

4th Harmonic = 21.0 inches long ... shortest recommended

5th Harmonic = 16.0 inches long ... typically never used

6th Harmonic = 12.7 inches long ... typically never used

7th Harmonic = 10.4 inches long ... typically never used

8th Harmonic = 8.7 inches long ... typically never used

 

---- Collector's Harmonics (includes Intermediate, Muffler , TailPipe) ----

1st Harmonic = 131.8 inches long ... longest with Mufflers and TailPipes

2nd Harmonic = 65.9 inches long ... longest recommended with Mufflers

3rd Harmonic = 32.9 inches long ... more bottom-end Torque

4th Harmonic = 16.5 inches long ... highly recommended , best Torque Curve

5th Harmonic = 8.2 inches long ... reduced Torque , more top-end HP sometimes

6th Harmonic = 4.1 inches long ... reduced Torque , not recommended

 

29.9" to 32.8" x 1.5"

Collector to end 8.3"

Pipe to can 18" overlap 4"

Can 14"

Tail pipe 10"

[Knock-on]

Blimey o'Riley Snapper. Proper head banging and no mistake

 

I may have a way around the sound issue Tractor. My can is a bit shorted and my manifold is inboard so am thinking of locating the end can inboard with just the exit pointing 45 degree away and down under the bottom of the chassis. Bit Aussie V8 like.

 

Bit of sound insulation around scuttle and passenger footwell and no more external exhaust.

[tractor]

cripes that must be a really small silencer

[fry61]

It's on the passenger side --- YOU are on the drivers side --- no problem then.

[Knock-on]

I know exactly what you mean Florin. They should be grateful Im compromising the BHP / Tonne by taking them at all

 

As an aside, are you aware of the new Camera that's just out? Apparently the shutter speed is so fast that you can take a picture of a woman with her mouth shut!!