Exhaust System - Converting double flexi to single [Archive] - BerlinaSportivo

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AlfaJack

06-10-07, 11:25

Hello,

Was speaking with wrinx about how the exhaust pipe on a standard Q4 goes from one downpipe, then splits in to two pipes for the cats, and then back to one.

As the flexi's on my downpipe are leaking I am looking to replace them with a 254mm x 54mm flexi from http://www.camskill.co.uk

However I would like to simplify the system by getting rid of one of the branches and have just one flexi - I do not have any cats in the system - If I needed one then I would just get an aftermarket one and fit it in.

I know the Integrale and Coupe have a single downpipe and exhaust as standard so I do not expect for it to cause a problem but I thought I would ask if anyone thinks differently - would I possibly choke the engine? Why did Alfa design it like this?

Cheers
Jack

AlfaJack

15-10-07, 09:25

Any input guys?

cuore_sportivo_155

15-10-07, 13:06

maybe they wanted toi increase the underbody clearance? i haven't seen a q4 exhaust in the flesh, but is it possible that a single, thicker flexy would hang a fair bit lower?

AlfaJack

15-10-07, 14:25

Nope, would be the same. bit odd really.

Do you think it would have a negative effect on the way the engine performed?

cuore_sportivo_155

15-10-07, 15:12

hard to say without a pic... are both pipes the same length?

If the rest of the exhaust isn't standard anymore, I wouldn't worry though

155-tbo

15-10-07, 15:35

I don?t see any problems if you take off that double flexi and put one back.
There is one poor foto under my car. As you can see, there is lot of space ;)
My car has dyno run after they had built that pipe and the power increase was almost 30 Hp.

Don?t notice that cicarette box, just a very bad habbit...

AlfaJack

15-10-07, 16:11

Thanks very much :)

Looks like the ciggy box is holding the exhaust up :tongue2:

markgq4

15-10-07, 23:33

my exhaust is a bit of a mess granted, but most people say its sounds good :)
anyway it has just a single pipe from front to rear, (one back box) and everything runs just fine , much quicker than wth 2 cats and pipes.

jimnielsen

16-10-07, 11:25

wrinx

16-10-07, 18:40

Watching this with interest...when's your MOT due Jack?

wrinx

AlfaJack

16-10-07, 22:51

Next June - will be looking to make it legit with a proper cat for MOT time :)

wrinx

16-10-07, 23:47

Ahhh, now that's no fun!

I'll be waiting until I get a bit of money and sorting the exhaust next I reckon. It took a few bashes whilst the suspension was fecked and also has a blowing joint...so, ditch the pre-cat and the race cat...then go argue with the MOT men! ;)

wrinx

Juan AR155Q4

17-10-07, 03:45

I think is just a ground clearence as cuore_sportivo_155 said. Using a single pipe with an unrestrictive cat would be bigger than using 2 smalls cats.

155-tbo

17-10-07, 15:38

Hey 155-TBO - The picture that you posted of your exhaust is what I am shooting for too.

Can you tell me what the external diameter of the new main pipe is? On my standard one, the external dia is 60mm. Did you use the original flange that connects to the turbos base

(as seen in this pic..)

www.nielsen.org/alfa155Q4/exhaustbit.jpg

or was it all new? I was planning on getting a 60mm mandrel bend and using it in place of the Pre-Cat... but your pipe looks bigger than 60mm to me?

JimN

Hello Jim,

External diameter is 76mm as known 3". My exhaust is made from steinless steel, so it was quit expensive, but now no need to worry about it. It maybe last longer than this car. It is all new from turbo to back silencer. I have two silencer and the sound.... hmmm... It is good, not too loud.
I have also mounted new turbo and all the flanges are custom made for this exhaust pipe. My downpipe is also 76mm (3").
Hope this will help you.

AlfaJack

04-11-07, 20:39

Finally got it done, its really not a pretty job but it works and no more leaks :)

RMB-Racing

06-11-07, 18:24

Hi,

I have made a 3" downpipe and 3" exhaust system from stainless steel, and with some Simons silencers.

Its not TIG welded, but MIG welded with stainless steel tread, and a mixed Argon/CO2 gas.

Here a some pics!

AlfaJack

06-11-07, 18:34

Very nice job!!

Steve Webb

06-11-07, 20:11

Hi,

I have made a 3" dowmpipe and 3" exhaustsystem from stainless stell, and with some Simons silencers.

Its not TIG welded, but MIG welded with stainless stell tread, and a mixed Argon/CO2 gas.

Here a some pics!

With my non-cat exhaust I use a downpipe that had the flexipipe built in where the precat used to be. (running down the side/rear of the engine) you lose the rear exhaust mount though. The pipe then runs down the passenger side of the car (usual route) and across infront of the rear diff.

RMB - any reason you use 2 silencers? I ran with just the rear silencer for quite a few years, its not that noisey. Certainly quiet enough for the 98db trackdays.
Also have you had any probs with running the exhaust down the drivers side of the car? Heat build-up etc around the middle silencer?

jimnielsen

06-11-07, 20:25

Great pictures as well, RMB-Racing! Can you tell me what you did at the flange that bolts to the turbo housing - did you remove the original pipe from the flange and grind out the hole to 3 inches as well, or have you welded the original pipe to the 3 inch pipe we can see in the pics?

thanks, JimN

RMB-Racing

06-11-07, 22:48

RMB - any reason you use 2 silencers? I ran with just the rear silencer for quite a few years, its not that noisy. Certainly quiet enough for the 98db track days.

Well - not really! Other than my wife drive the family 260 bhp VW Passat, so i?m left whit the Q4, which I don't mind. :tasty:
But a 3" exhaust system does make some noise, so an extra silencer is welcome - was my thougt...cause I use the car as an daily transport.

Also have you had any probs with running the exhaust down the drivers side of the car? Heat build-up etc around the middle silencer?

I haven't experienced any heat problems yet, from that silencer

Great pictures as well, RMB-Racing! Can you tell me what you did at the flange that bolts to the turbo housing - did you remove the original pipe from the flange and grind out the hole to 3 inches as well, or have you welded the original pipe to the 3 inch pipe we can see in the pics?

thanks, JimN

I have used the original elbow mounted on the T3 turbo. Then I have fitted it together whit my 3" downpipe with to flanges which are the same size an the original.
It will be re-arranged when I mount my new T3/4 turbo. Then I will make a new elbow in 3" stainless steel. But I make it, so it fits like the original!