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Supercharged Exhaust Advice

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#1 Donmizzi

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Posted 28 January 2021 - 04:38 PM

Hi everyone, I have a Speedster (VX220) for a few months and I am doing a general check and optimizations.

I would like to ask you for some advice on the exhaust.

I mount an Eaton M72, 75mm throttle (I know big, but in the meantime it's okay), 470cc injectors, side chargecooler.

I have read various discussions, mostly old ones, about the exhaust.

I am writing to you what I understand, so you can give me confirmation or not.

1) 4-1 or 4-2-1:
4-2-1 should move the torque down RPM, but with supercharged this is less important for me.
Also the assembly is easier for the 4-1 so I would prefer this.

2) Tubes Size
With the target of 260 hp I would like to have the primary tubes of 44-45mm and for the output I'm uncertain between 63 and 70mm (2.5" or 2.75").
If it is not necessary for power purposes I prefer 63mm for noise and also fitting... manufacturing... ecc...

3) Manifold design
Here on the forum I found this design that inspires me, because it has an adequate primary length (> 600mm), while instead the various Tullet, etc ... (OEM design) have short tubes, which should decrease the performance as I read. I attach photos

Attached File  exhaust_1.jpg   64.33KB   16 downloads

 

Attached File  exhaust_3.jpg   83.94KB   15 downloads

What do you think of these considerations?

Over the years, has there been any news or best solutions regarding the supercharged exhaust?

Is there any valid plug-and-play product, with the correct specifications, so that I don't have to have it custom made?

Thank you



#2 gertje

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Posted 28 January 2021 - 04:58 PM

2.5 is more then good enough for 260hp
I drive tullet mainfold original downpipe with turbo cat, turbo backbox and u bent



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#3 smiley

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Posted 28 January 2021 - 09:35 PM

I am on 2.5" with 335 bhp.
Is this for trackdays, or street only?



#4 Donmizzi

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Posted 28 January 2021 - 11:22 PM

Thank you for your reply

 

It's 70% Track, 30% Street

Now I'm getting more doubts.

 

1) Maybe it is more convenient to take a ready-made manifold? (money and time saved)

What can be the performance difference between the one proposed above (longest pipes) and a tullet 2.5"? 3-4 hp or more with my setup (stock internal)?

 

2) Now I mount a 2.25" line and the Regal manifold + decat. I have no idea of the current power but I wonder, does it make sense to upgrade to the full 2.5" Tullet with decat? Can there be a noticeable performance improvement?

 

 

Finally, I would like to ask for another info, when I bought the car I was told about 260hp. Is this possible in your opinion with my current setup?

 

Thank you



#5 smiley

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Posted 29 January 2021 - 07:41 AM

With stock internals, you are looking at a restriction of 260 bhp max to not break anything.
You can get 250 with just a stock M62, and stock engine.

 

With mostly trackday in mind, noise is important. (Unless they are more relaxed in Italy on this)

So spending lots of money on a fancy full exhaust for a 250 bhp conversion is a bit of a waste in my book.
Some people just remove the oem precat section and replace the backbox for a turbo version (2.25") and they end up with a quite system.
Some people just replace the manifold for a 2.5" tullet one, as the oem casted one does get a beating and cracks.
The tullett manifold also can crack after quite a few trackdays.

 

If you do go for a full tullett one, keep in mind that by default they use a ceramic cat that can get damaged after a few years of tracking.

You can ask for a HJS steel cat to be welded in, but that is pretty expensive.

 

1. Peanuts on performance. This is about longevity of the system
2. Neglect able difference, and not worth the investment. Just more noise.

Yes 260 could be. Like i said, 250 easy, and the extra 10 are relatively expensive.
Once you are looking for way more, it's engine enforcement, and then the exhaust discussion becomes more important.


Edited by smiley, 29 January 2021 - 07:47 AM.


#6 Donmizzi

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Posted 29 January 2021 - 08:39 AM

Many thanks, this post save me money and time

 

In Italy the noise problem is not yet so present, but the restrictions are advancing quickly.
In fact I'm thinking about how to silence more with a bigger box.

Now I have an empty 60cm x 12cm diameter silencer :huh:

 

Thank you



#7 smiley

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Posted 29 January 2021 - 08:54 AM

Track noise meters are sometimes triggered by inlet noise also.

If you use the oem filter box, it is very quite, and capable of 250.
If you put on an open cone at the end, it is much more noisy. (Lovely sound for road use though, as air get's sucked in very close to your ears)

 

The oem NA and turbo backbox are so called chambered exhaust types.
That means they are canceling the noise by air travelling through multiple chambers in the box, killing the noise.
Something like a tullet backbox is an absorbtion type. That means a perforated straight pipe, with absorbtion wooling around it (that may require replacing at some point, as the material desintegrates)

 

So in this case, bigger is not always better. The absorbtion types are louder then chamber types.


Edited by smiley, 29 January 2021 - 08:59 AM.


#8 sford

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Posted 29 January 2021 - 09:33 AM

On mine (Eaton SC and front mounted cooler) I have a tullet manifold, standard downpipe with the cat removed and then turbo ubend to turbo backbox. It's quiet enough for UK track days (tested 89db at Coombe) and made mid 250's on the Dutch software power test. Think it was averaged at 252bhp. I wouldn't say it sounds brilliant but then I don't think many 4pots do tbh. It sounds good enough I was happy with it. 



#9 Donmizzi

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Posted 29 January 2021 - 01:34 PM

Thanks for the filter tips and also on the box models

 

I have the cone filter, lovely sound it's true. and the perforated straight pipe silencer

 

I also have Dutch software (correct me if I'm wrong, but it's obdtuner, right?)

 

I am curious to try a power test,

but first I want to check that everything is ok.

 

Thank you


Edited by Donmizzi, 29 January 2021 - 01:35 PM.


#10 smiley

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Posted 29 January 2021 - 01:50 PM

Yes, odbtuner is a Dutch invention.

Basically a speedster owner into programming, that was fed up with limited options available for our NA cpu.
He locked himself into his attick for a few years and came up with obdtuner 1.0 for NA engines.

Then later on 2.0 was introduced for forced induction, and that is when tuning went through the roof, resulting in 500 bhp 2.4 liter engines.



#11 The Batman

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Posted 29 January 2021 - 09:18 PM

let me know if you want a 2.5 or 3" tullet system :)



#12 TheRealVXed

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Posted 04 February 2021 - 07:56 AM

I have a standard manifold & cat on a SC around 250hp also.  I have a Larini back box though so it is loud.  101db at last track day.  I'll be looking to replace soon as this prevents me from most UK tracks nowadays :(

 

Want a Larini? :lol: 



#13 dominik

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Posted 04 February 2021 - 11:18 AM

I have a milltek VXR backbox on my Turbo which is an absorbtion damper, but a real big one.

I have to repack it every 10000km an i am trough with all  the expansive fillings , nothing lasts long.

 

If you want to go the absobtion way , look for a silencer which can be screwed and not have to opendend  with a grinder and rewelded after repacking.



#14 smiley

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Posted 04 February 2021 - 01:26 PM

The only silencer that can be opened that i know of is the tullet one.

Keep in mind that tullet choose to have the u-bend section that meets the cat section flenge a few degrees off versus the rest of silencer vendors.
That means modding it, if you want it to mate up to something else then a tullett cat.

 

You can see it here. On the left is the tullett ubend.

On the rights the ubends like oem NA/turbo, janspeed, miltek etc.
ubendcrap.jpg


Edited by smiley, 04 February 2021 - 01:30 PM.


#15 oakmere

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Posted 07 February 2021 - 10:53 PM

Had mine re-welded for about £20.
The back box was second hand so didn’t mind would not be happy if purchased new.

#16 titus

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Posted 07 March 2021 - 12:55 PM

Interesting contribution for the discussion which exhaust for a SC conversion. I've tried everything possible ...

OEM 2.2 manifold and OEM KAT (pre-cat removed) and VSE muffler. Was ok and especially nice bang and pop noises ...

Then upgrade to Dbilas Manifold and DBilas 2.5 "downpipe with 200 cell Kat and VSE ... and it got louder!

Last upgrade, installation of a Larini backbox. That was too much! Very loud> 105db!

So Larini down again and OEM Turbo Backbox. This is the perfect compromise, reasonably good sound, <90db and absolutely sufficient for about 260hp (3 "pully and M62 Eaton). I can recommend this combination.



#17 gertje

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Posted 07 March 2021 - 12:56 PM

Got a full tullet 3" for sale
Static 92db at 4000rpm

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Edited by gertje, 07 March 2021 - 12:57 PM.


#18 titus

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Posted 07 March 2021 - 01:15 PM

Here some pics from the dbilas manifold and downpipe.

Attached Files



#19 smiley

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Posted 07 March 2021 - 01:33 PM

Do you know if anyone ever reported a cracked dbilas manifold on his SC?

Ie if it can take a beating over years of tracking?

 


Edited by smiley, 07 March 2021 - 01:34 PM.


#20 titus

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Posted 07 March 2021 - 03:50 PM

good question .... dbilas only says that the manifold should not be exposed to temperatures above 900 ° ...

 







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