Exhaust system rebuild

[stephen low]

The exhaust I had fitted originally was a pretty cheap system to get me through compliance. Job done!

Want to look at rebuilding the system to develop a nice note without being overly raucous and keen to get some ideas on sizing.

Running a standard 5L Windsor as the 220kw variant with headers taken from an RMC and the standard AU cats for the model at the time.

Just to make it be a nice street car.

So what is the suggested sizing from the headers through to the rest of the system?

And while I'm asking what does a balance pipe achieve linking left and right exhaust banks?

The one future plan I might explore, though a long time off, is supercharging the motor, how does this affect exhaust sizing?

Cheers

[Modena]

slowy, 1 & 3/4" primaries are ample for your motor. Shorter primaries will give you better low down torque, longer will give better high-end power. A x-pipe balances the flow and (allegedly) gives more power as it can create a bit a venturi effect and give greater gas speed.

If you did put a blower on you would probably want to be at 1 & 7/8" primary size depending on boost and power levels.

I used 1 & 3/4" on my 6.2L, this is a 340kw motor from the box. For a non race-car low down driveability wins hands down over top end power.

As you have asked about a balance pipe I guess you're talking about an under-car system?

[stephen low]

Thanks Ben

Yes undercar exhaust for a street level driver.

Might have to live with the current headers then and just attach a far better system behind these for the moment.

Cheers

[750hp]

Twin 2.25" with a balance pipe is all you need for your current power level. Go with twin 2.5" if you're likely to get the blower.
As far as primaries - what Ben said!
Hooker Aerochamber mufflers are a good all rounder for price, sound, volume and power.

[stephen low]

So am locked into an exhaust provider with good results and history to do my work next week hopefully.

For just the normally aspirated 5L he had talked 2 1/4 pipework but also said go 2 1/2 if going to SC the car down the track.

What will the slightly larger piping do to the 5L for the moment in terms of power?

I talked about trying to improve clearances under the car.

This because the 2 into 1 segment on the passenger side after the headers is hitting the bottom of the chassis, the drivers side equivalent is hanging well down as is much of the rest of the system.

So to better redirect, after the headers each 2 into 1 will direct the cats under the tranny tunnel to gain some space and height, followed by a crossover and I am planning on running a pair of small hot dogs each side to gain space and a little more note.

Going a full stainless system with mandrel bends.

Interestingly 2 1/4 mandrel bends are more expensive than either 2 or 2 1/2 bends and he can use nice food grade 2 1/2 pipe.

Looking forward to a better system shortly!

[SVO 050]

I built a 34 chev coupe with a 671 blown small block, used 1 7/8 primaries, 2 1/2 system with single offset stainless mufflers. If your contemplating SC later don,t worry about a cross over as this is only to improve scavenging on normally aspirated engines. I used 304 stainless steel milk tube, sweet mandrel bends, easy to tig weld and polishes a treat. You can buy concentric and eccentric tube reducers and use profile cut flanges to make fitting and fabricating the system easier.
I,m running a 5L SVO, Tremek 5 speed , Jag 3.07 diff, it has 1 7/8 short primaries with collector into 3" cats under the chassis rail, have 4" live side pipes plus a full 2 1/2 rear exit system with high flow mufflers tucked under rear of boot floor. Passed rego on rear exit 90db.
Engine has a GT40 cam, is rated at 340hp at flywheel and makes exceptional torque from 2200 RPM up
Cheers
SVO

[dhs.buckley]

]Hi Slowy, I Have block hugger manifolds on my 302 with straight through cats 2 1/4"and 4 hotdogs ( 2 each side 6" long) Mufflers wont fit.
The sound is very disappointing compared to my ute which has 2 hotdogs 12" long. i think there is just not enough length in the pipes to get a nice note out of it. sounds a bit like a V8 speed boat. not sure if the link will work
https://youtu.be/oFE84Vf9i6M
hope fully it work this time.

[stephen low]

David

Your right link didn't work and I couldn't find it on your face-ache site through my wife's connection.

Steve

[boxhead]

Originally Posted by 750hp

Twin 2.25" with a balance pipe is all you need for your current power level.
Hooker Aerochamber mufflers are a good all rounder for price, sound, volume and power.

This is very similar to the mandrel system I built for George.
Only different is my mufflers are before axle, and it was recommended to step it up from muffler exit to tip with 2.5 inch
I assume in Cobra the mufflers will be in the back of rear guards.

[Aussie Mike]

A couple of interesting videos headers I found recently

[ame]https://www.youtube.com/watch?v=azPKIjxmmdU[/ame]

[ame]https://www.youtube.com/watch?v=O1bXPNy1Yn4[/ame]

Cheers

[deano59]

Originally Posted by Aussie Mike

A couple of interesting videos headers I found recently

https://www.youtube.com/watch?v=azPKIjxmmdU

https://www.youtube.com/watch?v=O1bXPNy1Yn4

Cheers

i saw that a while ago pretty amazing how smashed in they had to be b4 dropping power

[stephen low]

Currently have 14" mufflers in the back corners. Both mufflers were panel beaten to fit so not good. Don't know but doubt these are high flow jobbies so pretty good at sound deadening.

Essentially one hot dog will go into each back corner and being so small will fit a treat, the second dogs will be located just in front of the diff and the pipe work will be high near the lower suspension arm pivot to keep the exhaust as elevated as possible.

Using two pair of hi flow dogs to compensate for the reduced noise reduction capacity of these compared to the 14" mufflers.

And an interesting vid Mike, I too would have sworn big HP loss with the bashing, even early on.

[Jaydee]

Mine has very short collectors into standard cats then into 1200 mm hotdogs with perforated pipes inside. I haven't had an official sound test, but it sounds really nice. I have also double wrapped the whole system.
JD

[stephen low]

Thanks guys

Sounds like quite some variability between systems despite somewhat similar setups.

In the hands of my bloke to an extent I guess but he has already made a statement about nice sound from what is proposed.

It is his level of experience and exposure I based the decision to use him and I'd like to think he has heard enough examples to know what will be nice.

The cats and dogs will be high flow parts but am still curious what the collective believe the effect of the 2.5" system will have on the standard 5L engine's performance.

It is stock at the moment except for a pair of Ali Edelbrock heads.

So until I get it supercharged what is the likely effect of the slightly larger exhaust system to be on engine performance?