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Roger King 155 Xflow exhaust system


randybugger

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does anyone have any experience with a 4-2-1 exhaust system on a Xflow? Mainly any improvement in lower revs power/torque over the standard 4-1 system.

I have a 155bhp Roger King on 40’s with mega jolt 3D iginition and caterham 4-1 primaries and collector into a powespeed 7 inch silencer. It drives well and pulls strongly so don’t have any complaints, just wondered if it’s a worth while excersise.

 

 

 

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The standard Caterham 4-2-1 system is totally inadequate for your engine, largely because of its small bore. The 4-1 system is far from perfect, witness the fact that the primaries are not all the same length, but as an "off the shelf" solution it was the best available at the time.

If the car is for road use, a custom built 4-2-1 would likely be the best solution, but sorting out lengths and bores will be a matter for calculation/experimentation. For a high revving track car, an equal length 4-1 system may well be perfectly fine, but again you would need to work out lengths and bores.

If you are really after a perfect system, you would have to have it individually tailored to suit your engine's specification in order to take into account the cam profile and other factors that affect the power band. Realistically, this is only practical for someone with a huge budget.

Incidentally, back in the 1970s, when I was building the works Ford BDG rally engines, we tried one of the car's exhaust systems on the dyno and power dropped from 255bhp to 215bhp when compared to the dyno's own race derived 4-1 system. A couple of days work and we had a car system that was perfectly useable, but only lost around 4bhp by comparison. It was, I think, Ari Vatanen that they gave it to, to try, and he raved about the new development engine; no-one had told him that the engine was actually knackered and in dire need of a rebuild. 

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Thanks Roger, I’d hoped you would see the post.

I’kl talk to powerspeed and see what they come up with. The car is only used on the road and the engine has been brilliant. Haven’t got a huge budget but it sounds like a worthwhile purchase if they can do an improved package.  

Tony

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