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Locosaki
Spa-Francorchamps


Joined: 03 Jul 2016
Posts: 265
Location: Fife


PostPosted: Fri Jun 08, 2018 7:22 pm    Post subject: Equal length manifold Reply with quote

Having just fitted my 200cell cats and mild sport boxes it got me thinking about the manifolds, is there much to be had changing them and if so I assume going equal length would be the way to go.

Having had a search there doesn’t seem to be much on offer for equal length or would the cheaper manifolds into the merge collector be as good.
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Martin996RSR
Monza


Joined: 08 Dec 2016
Posts: 206



PostPosted: Fri Jun 08, 2018 7:31 pm    Post subject: Reply with quote

I've been looking into manifolds as mine also need changing. Manifold design has priorities for good performance which are:
1. Minimising the number of tight radius bends, especially those close to the cylinder head.
2. Tuning the length of the pipes to fit the rpm where the maximum power is required (you may want more meat in the mid range than the top end, in which case you would make the pipes longer).
3. Tuning for scavenging effect - this is where equal or close to equal length pipes come into play.

If you're going for performance then go with the 1st item on the list as your most important criteria, the other affect performance, but not as much. I did find some manifolds that looked pretty good in this respect but I can't remember where. You should also bear in mind that the difference between the best available manifolds with the exhaust end in the stock location and the worst Ebay Chinese specials is probably only 5 HP. They are limited by the packaging issues the engine location/configuration, and the stock exhaust configuration presents.
 
  
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Phil 997
Brands Hatch
Brands Hatch


Joined: 05 Dec 2015
Posts: 13254
Location: Bournemouth,Dorset

2009 Porsche 997 Carrera 4S

PostPosted: Fri Jun 08, 2018 7:52 pm    Post subject: Reply with quote

Nothing to add to that a great explanation Martin Thumb Thumb Thumb
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Dammit
Albert Park


Joined: 23 Sep 2016
Posts: 1503



PostPosted: Fri Jun 08, 2018 7:59 pm    Post subject: Reply with quote

I was going to go for these, but not 100% yet (Cargraphic equal length):

 
  
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Martin996RSR
Monza


Joined: 08 Dec 2016
Posts: 206



PostPosted: Sat Jun 09, 2018 4:51 am    Post subject: Reply with quote

Those look OK, but I'd wager they're not better than the cheapo Chinese Ebay jobs. I would forego the equal length rearmost pipe in preference to it being less bendy.
If it were my money, I'd buy the cheap ebay ones and spend the difference on other performance upgrades.
 
  
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Dammit
Albert Park


Joined: 23 Sep 2016
Posts: 1503



PostPosted: Sat Jun 09, 2018 7:42 am    Post subject: Reply with quote

I’ve got a set of the Chinese ones, they are pretty good -excellent for the money- but they’re a smaller diameter than the Cargraphic ones.

As are the TG ones, or I’d have been tempted by them.

X51 are 1.85”, Cargraphic are 1.75” and all the others are 1.65”.
 
  
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Martin996RSR
Monza


Joined: 08 Dec 2016
Posts: 206



PostPosted: Mon Jun 11, 2018 8:28 am    Post subject: Reply with quote

I should have mentioned in my earlier post that the diameter is also an important consideration.
The diameter needs to be appropriate to the amount of gas flowing, so larger is not always better. For a punchy mid range (what most of us really want in a road car) you would want a small diameter than what would give the absolute best power at the top end.

It would be great if some back to back tests were done with te dyno curves made available so you could make an informed choice based on your need and the data.
 
  
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Dammit
Albert Park


Joined: 23 Sep 2016
Posts: 1503



PostPosted: Mon Jun 11, 2018 9:01 am    Post subject: Reply with quote

I agree, and the reason I'm tending toward the Cargraphic is that they seem to be the happy medium, although they're literally 10 times the price of the Chinese ones that I already have, so I might stick those on first to see what the impact is. The exhaust side of the M96 doesn't flow very well at all (see hte flowbench testing Mike did in the Benchrace thread), hence why Porsche went to (relatively speaking) very large primaries for the X51 stuff.
 
  
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Stoo.c
Monza


Joined: 07 Apr 2014
Posts: 152
Location: Hertfordshire


PostPosted: Mon Jun 11, 2018 9:58 am    Post subject: Reply with quote

Also given the pretty severe bends in the rest of the system, having a perfectly designed manifold is going to make a fairly limited difference.
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Albert Park


Joined: 23 Sep 2016
Posts: 1503



PostPosted: Mon Jun 11, 2018 10:26 am    Post subject: Reply with quote

Aggregation of marginal gains, innit.
 
  
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Martin996RSR
Monza


Joined: 08 Dec 2016
Posts: 206



PostPosted: Mon Jun 11, 2018 5:51 pm    Post subject: Reply with quote

What if TG did an entirely new system, and ignored compatibility with existing parts? They could then have much longer primaries with less severe bends, and perhaps get much less severe bends in the rest of the system too.

If they produced an exhaust that released a dyno proven 30hp for £1500 then I'll bet it would sell in enough volume to justify the development cost.
 
  
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Albert Park


Joined: 23 Sep 2016
Posts: 1503



PostPosted: Mon Jun 11, 2018 6:43 pm    Post subject: Reply with quote

The limitation is ground clearance I thought - in terms of how tight you had to make the turns? Rather than connecting to the cat sections.

Perfectly prepared to be told that I'm 100% wrong, that said.
 
  
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Martin996RSR
Monza


Joined: 08 Dec 2016
Posts: 206



PostPosted: Mon Jun 11, 2018 8:22 pm    Post subject: Reply with quote

That is one of the limitations, but I would be happy for them to go down a little further than sump level. There is also the next set of bends; those that point the primaries to the rear which could use a bigger radius. The primaries should also be made a lot longer, with the collector further back and a joint after that.

The radius to bring it around to the rear of the car could be maximised and a 100 cell cat put in at that point, followed by a rear centre box fed from both sides and a centre exhaust. That one cerntre box would save a lot of weight as well.
 
  
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Dammit
Albert Park


Joined: 23 Sep 2016
Posts: 1503



PostPosted: Mon Jun 11, 2018 8:33 pm    Post subject: Reply with quote

I always wonder about 100 cell cats - as they won't pass an MOT, is there much point fitting them?

I did enquire of TG whether they'd make custom - the response was no, but Alex provided me with the details of a place that they recommended.
 
  
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