Exhaust 4-1 to 4-2-1 modification

[frankyknuckles]

On various threads both on BC and r300.net there has been mention of 4-2-1 exhausts being better (providing more torque) than 4-1.

The Caterham Rx00 collector is 4-1.

With the larger silencer, the collector pipe is reasonabley short. Is it worth modding it to 4-2-1? Will I get a better torque curve?

If so, which pipes should be collected into 2's? ie, the 4 primaries form a square, should the 2 on the top and the 2 on the bottom go into seperate pipes before becoming 1 pipe, or should the 2 left and 2 right hand side pipes become 2 before going into 1, or does it not matter?

 

www.R300.net

[DohNut]

 

They would link realative to the order that they fire in.

If firing order is 1-3-2-4 then 1&2 link and 3&4 link.

 

Think of the slugs of air coming out of the cylinders you want them to "merge in turn" into the pipes so you dont want consectutive firing cylinders emptying into the same pipe.

 

Nick

[frankyknuckles]

thanks.

 

www.R300.net

[Myles]

Is it really worth doing the mod?

 

I don't mean in terms of the change in torque etc., but in terms of battling the existing system.

 

My (limited) understanding from previous threads has been that there are some 'magic lengths' or ratios of primaries to secondaries (it's all about resonance I guess) - but also that you can rapidly run out of room for the silencer if you are not careful.

 

Sell old and buy new?

 

I'd be interested to hear how the costs etc. shape up though - I've got a 4-1 (long) system and would be interested in a cost-effective 'upgrade' to a 4-2-1.

 

Project Scope-Creep is live...

 

Alcester Racing 7's Equipe - 🙆🏻™

 

Alcester-Racing-Sevens.com

---

[frankyknuckles]

exactly, is it worth doing, is there enough room? if it is done will it be crap? etc etc

 

www.R300.net

[Ozzy]

I thought you were selling it Franky. Not spending more money?

 

Oz.

 

Still Shaking

 

6 speed 1600k Supersport

 

[oilyhands]

Mike Bees did some testing at Emerald on the affects of changing from a 4-1 to a 4-2-1 and there were very worthwhile gains to be had in the mid-range.

Oily

[frankyknuckles]

I thought you were selling it Franky. Not spending more money?

Just planning ahead if it does not sell by the spring

 

 

www.R300.net

[Petrolhead]

Would take oily's advice a spend you money else where, like advertising :)

 

NE7Club Web Site

R5 no 65 😬

[DohNut]

 

As a modification in isolation the economics are not going to be great but if you were combining it with changing the Silencer (RaceCo/Techcraft) to one that had a different outlet diameter then you could keep your standard collector and get a 4-2-NewSilencer collector made up, easy to revert to standard and you have a saleable collector / silencer combo 😬

[EFA]

Doh Nut, You say its logical to link pipes based upon firing order, They would link realative to the order that they fire in.

If firing order is 1-3-2-4 then 1&2 link and 3&4 link.

 

On a VX the firiing order is 1-3-4-2 (I'm not sure what engine runs 1-3-2-4) which pipes would you have linked in a 4-2-1 system?

 

 

 

[Shaun_E]

I thought about modding my existing 4-1 but you may well run out of room for a decent sized silencer - if noise is likley to be an issue then it probably doesn't make sense. I guess if you shortened the primaries it might work. In the end I sold my 4-1 and bought the Caterham 4-2-1 VHPD system. The cost to change ended up being about £400 but I also went from a 5" silencer to a 7" which I would have had to do anyway for noise reasons. You could probably sell your 4-1 for more than I sold mine for and thus reduce the difference. Mine was the Caterham competition one that retails for £495+VAT so I sold it for £290 which is about half the new price (and very good value for the purchaser). The Rx00 system costs more new so you should get more for it. The Caterham 4-2-1 links primaries 1 & 4 and 2 & 3.

 

Yellow SL #32

[DohNut]

Arnie

I could easily be mistaken over the firing order.

The thing I would be clear on is that the

first cylinder to fire goes down secondryA

the second to fire goes down secondryB

the third to fire down SecondryA

etc.

 

VX the firiing order is 1-3-4-2

I would suggest linking 1&4 3&2

 

Nick

[EFA]

Thats better........ 😬 😬

 

 

 

Edited by - EFA on 18 Dec 2005 18:51:07

[jerrypike]

caterham sell a 4-2-1 as a direct cat replacement- not cheap £170 IIRC- but a true bolt on swap

can't tell you the difference as apart from cat removal i had a couple of other mods done at the same time before it went to RR so no direct comparison

must be worth the usual second a lap 😬

 

jerry

[PAUL MARRIOTT]

If you look at the nice Mr Oily's site there is a spec for pipe lengths and diameters for a 4-2-1 system which I followed on my 1800 K when I did my head. I got 189bhp bags of torque mid range and the nice Mr Walker recons that I got at least 5 bhp from the pipe diameters, which are fairly skinny but apparently that makes the gas velocity higher and increases the scavenging effect.

 

PAUL m

[Weirdy]

Selling? Get a better fix of Upgraditus you'll feel better 😬 😬 😬 *thumbup*

 

Weirdy

 

Its not the winning thats important, its the taking them apart.......

[David M]

4-2-1 exhaust gave me a clear 10% increase in torque and an additional 5bhp. From a standard 140bhp 1.8 Xpower measured on the Emerald rolling road (138bhp actual) as measured when car was standard, to a second emerald run after a power speed 4-2-1 exhaust was fitted. I have a lovely graph with the two runs plotted and the whole line is shifted up showing a nice 10% increase in torque along the length of the curve....... very happy.... the best way I can describe it is as though the car has been fed multiple packets of airwaves.... Dave also made up a 4 into 1 converter attached to my old silencer for future mot tests.....

 

David

 

 

 

GF04RCE.... every day is a Caterham day!!!! He heee!!... pictures here. Problem is every day seems to be a GT4 day too...!!!