Made 275bhp on the dyno today but it appears my exhaust collector is a choke point. It's a race line exhaust 4-1 so I'm surprised but it's probably down to the bodging to get my silencer to fit and it needs repacking.

So where to get a good collector from that won't cost lots of money and any ideas on design. Will a venturi type design be beneficial.

What engine / spec is it and how have you come to the conclusion that the collector is holding it back? 275bhp sounds pretty impressive especially if it's N/A

I had a larger collector end welded in to the original
So count off the double step from can to collector and have a tube the same diameter as the can all the way to the collector

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Originally posted by Nickp
What engine / spec is it and how have you come to the conclusion that the collector is holding it back? 275bhp sounds pretty impressive especially if it's N/A

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• Omega HC pistons
  
• Saenz steel rods
  
• Raceline dry sump
  
• 1mm oversize Hi Port Neil Roper cylinder head
  
• Kent DTEC 80 cams
  
• RaceCo 54mm DTH bodies with 690cc injectors
  
• Emerald K3 ECU
  
• Raceline stainless 4-1 exhaust manifold and Wun-Off silencer
  

If you have the space a 4-2-1 will free it up and improve torque figures also.

Simpson exhausts will have them off the shelf.

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Originally posted by ian996

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Originally posted by Nickp
What engine / spec is it and how have you come to the conclusion that the collector is holding it back? 275bhp sounds pretty impressive especially if it's N/A

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N/A Duratec

Amongst other things, main parts are:

• Omega HC pistons
  
• Saenz steel rods
  
• Raceline dry sump
  
• 1mm oversize Hi Port Neil Roper cylinder head
  
• Kent DTEC 80 cams
  
• RaceCo 54mm DTH bodies with 690cc injectors
  
• Emerald K3 ECU
  
• Raceline stainless 4-1 exhaust manifold and Wun-Off silencer
  

I think i can get slighty better port matching from bodies to head, but the tuner said the collector was a bit of a choke point.
Cam timing is spot on, rev limit is set at 9200. Might be worth recleaning the head as i when i took it for a shake down it was badly over fueling - throttle pot was reading as stuck open so was throwing huge amounts of fuel in.

[Edited on 29/9/15 by ian996]

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9200! Nice

It couldn't be the silencer its self choking could it? Do they have a hp/flow spec?

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Originally posted by ReMan
9200! Nice

It couldn't be the silencer its self choking could it? Do they have a hp/flow spec?

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Originally posted by ian996
[

Anyone know of a good place to get merge collectors made up for reasonable money? maybe a longer flowing collector with venturi type pipe to silencer.

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If it's up at 9200rpm, your better staying with 4 into 1 collector, and as said above the collector itself looks ok but get a larger outlet pipe welded in place and then all the way to the silencer. You should be at 2.5" or larger ideally, what size is there now? (hard to tell from the picture...).

Ian

If it was mine I would chop a small amount off the 4-1 and round up the end.

Weld on a bigger link that suits the can inlet.

Please bare in mind I don't know the sizes.

Paul G



Description

^ What everyone else said then