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worldwidewebs

Exhaust Questions

16 posts in this topic

Has anyone done a comparison between an S2 k-series manifold and an aftermarket 421?

 

I've got a 2bular 421 on my S1 111S which has given much improved torque over the standard item. The only downside is that I'm sure it's quite a bit noisier than before, but as it was fitted so long ago I can't remember what it was like! I think a lot of the change in sound is probably down to the change in material, from a cast item to tubular stainless. It may not be noisier, just more metallic, if that makes sense.

 

I've been on a bit of a mission recently to try and reduce noise volumes in the car - it's an age thing I'm pretty sure! So far I've added carpet, put the std airbox back on and fitted a quieter silencer and it has made the car so much more enjoyable (for me) without really taking anything away. The next thing on my list to look at is the manifold.

 

I've read a few posts over the years that suggest there are two potential improvements that could be made to an S1 on the exhaust side whilst staying pretty standard. The first is to grind out the clag in the standard S1 manifold, the second is to fit the S2 manifold and link pipe.

 

So, am I right in saying that the standard cast items are quieter than a stainless system? Also, would a cleaned up standard S1 or S2 system be that much different in performance terms to the 421 on an otherwise standard VVC S1?

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There's a low weight, simple and low cost way of reducing noise.

It also follows the Chapman principles.

 

 

 

 

 

 

 

Ear plugs :)

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I lost about 20bhp when I did this to my s2 111s vvc - it improved torque but lost me power, think Jamie with the red 111s might be worth asking - think he had only small gain on standard bhp and he had done more to his that I had done to mine if I recall. like the dyno guy was saying to me, the 111s compression was porbably so finely done, lotus would have like £100k's development to get optimum performance with exhaust systems and aftermarket companies are spending only small percent of this , as for the noise it was slight louder, not noticibly than standard nothing significant though, made the note more raspy when I had it done

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I lost about 20bhp when I did this to my s2 111s vvc - it improved torque but lost me power, think Jamie with the red 111s might be worth asking - think he had only small gain on standard bhp and he had done more to his that I had done to mine if I recall. like the dyno guy was saying to me, the 111s compression was porbably so finely done, lotus would have like £100k's development to get optimum performance with exhaust systems and aftermarket companies are spending only small percent of this , as for the noise it was slight louder, not noticibly than standard nothing significant though, made the note more raspy when I had it done

I'm not quite sure I follow, sorry. Are you saying that removing the 421 and going back to std lost you 20bhp? I certainly wouldn't say that putting the 421 on mine made any difference in power but it did give a useful torque gain. However, I've since learned that the S1 manifold is restricted by weld clag and benefits from a clean up - it may be that a cleaned up S1 manifold isn't "that" much worse than the expensive 421 that's on now.

 

So basically I have 2 questions: how does a cleaned up S1 or S2 system compare to the 2bular 421?; would the standard system give a slightly less metallic/harsh sound?

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Can't help with the answers Andy but when you do find out & if you decide to swap for a standard S2 set up I will do you a swap + some £££s smile.gif

 

Russ.

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Can't help with the answers Andy but when you do find out & if you decide to swap for a standard S2 set up I will do you a swap + some £££s :smile:

 

Russ.

I'll bear that in mind Russ :)
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I have a fully de-clagged S1 manifold & 3yr old Elise Parts down pipe (with flexi section) that I would be interested in swapping and possibly some ££.

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I think it'll all end up staying on tbh as I can't determine whether the std items are quieter.

 

I did think about wrapping the manifold but most people seem to have longevity issues with it. There is some stuff called magma wrap from thermal velocity which is supposed to be better but whether it would last or not I'm still trying to find out

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IIRC the VVC likes a bit of back pressure so freeing up the exhaust flow doesn't have much of an effect as it does in the non VVC.

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IIRC the VVC likes a bit of back pressure so freeing up the exhaust flow doesn't have much of an effect as it does in the non VVC.

 

 

+1.... I have heard that the VVC requires back pressure.

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I've used the magma wrap on previous cars and it lasted as long as I had the car. It's brilliant stuff. But it on damp and its fantastic...

How long did you have the car? And what was it?

 

Some people "report" issues further back when using wrap - did you experience any problems?

 

Cheers

A

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It was on my scoob. Everything that could be wrapped was. I started using some "cheap" wrap which basically became brittle and just fell off. But the magma stuff, applied damp was superb. Must have been on 3 years, and still on when I got rid. You get what you pay for is what I concluded... I think the art is getting it on right, apply wet and as tight as you can....

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I think the art is getting it on right, apply wet and as tight as you can....

 

 

Phnaar, phnaar

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The more you search about vvc and back pressure and the more you realise it appears to be a forum rumour based on A test done on one MGF and related on MGF ultimate. The difference was very small; 3bhp...

There don't seem to be further "scientific" evidence. People who are racing vvc elise S1 with decat don't seem to get that mythic power loss. S2s are supposed to be raced with cat.

The 5" silenced decat makes the car quieter.

Before 100 to 101db @ 4.5krpm

After 90 to 93db @ 4.5krpm

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