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M135i- Paul Welder mod?

3K views 26 replies 13 participants last post by  Tooney 
#1 ·
Anyone had Paul Welder () modify an M135i exhaust?

I'm looking to modify the standard back box or go for a straight through mid-pipe.

Any recommendations?

Cheers

Josh
 
#5 ·
AndytheGreek said:
I've only heard good things about this Paul chap. Maybe it's worth paying to get a proper job well done. We don't all have access to welding gear or the knowledge to do this type of mod.. just saying.
Same - he seems very highly regarded in the M communities.

What are others doing? Cutting back box, then sealing vents in the pipe?
 
#9 ·
I've been looking at MPE, but £700!!!

To me, mid-pipe is the cheap option and not one I am hugely interested in.

Paul seemed like a good place to go seeing as people are taking their brand new M2/3/4s to him.

I'm assuming the back boxes on a proper M car is pretty similar to a MPE??
 
#12 ·
Great timing - I just picked up an almost new M140 exhaust last night with the aim of getting the inside welded as a mod.

Certainly cheaper than MP£ but still seems like a lot for some welding (appreciate it's a skilled job!). Wonder if my local powerflow outfit will be able to do something similar for cheaper.
 
#13 ·
Quattrodave said:
Great timing - I just picked up an almost new M140 exhaust last night with the aim of getting the inside welded as a mod.

Certainly cheaper than MP£ but still seems like a lot for some welding (appreciate it's a skilled job!). Wonder if my local powerflow outfit will be able to do something similar for cheaper.
Any exhaust place should manage it and it shouldn't cost much. There was a thread before and Paul could do 6-8 exhausts per day.

Fair play to the guy for managing to command more per job what many skilled tradesmen command per pay.
 
#14 ·
I watched a very interesting video on YouTube about exhaust design, was about 30 or 40 mins long and an american guy from magnaflow I think was the company. Well worth a watch, if anything it'll probably stop you wanting to mess about too much with your car as it could end up costing you bhp, especially these mods which involve putting in straight through sections and welding up holes inside the back box
 
#16 ·
Jamesno1 said:
I watched a very interesting video on YouTube about exhaust design, was about 30 or 40 mins long and an american guy from magnaflow I think was the company. Well worth a watch, if anything it'll probably stop you wanting to mess about too much with your car as it could end up costing you bhp, especially these mods which involve putting in straight through sections and welding up holes inside the back box
To be honest, if your bothered about power you wouldn't do this mod, you would get a decat or complete exhaust and remap (or something like this) but if you are just looking for a cheap option to make your car louder this is a pretty good fix for your craving!
 
#21 ·
interesting what the guy from magnaflow said though about having the perforated pipe, that on a WOT run the silencers fill and any new exhaust gasses effectively cant enter there and the perforations allow the cushion of air to flow more smoothly, so what Paul Welder does in taping the perforated holes externally is mimicking this as its still retaining the holes internally. so shouldn't this mean that the exhaust is effectively permanently in WOT mode so lots of fast exhaust gasses and lots of noise, with no additional turbulence or slowing of gasses?
 
#22 ·
What Paul does is basically replicate the design of the Mpe. It will give no improvement in performance like the Mpe it's purely just for sound enhancement. As stated if you want Performance and sound you fit a decat.

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#25 ·
Two strokes need back pressure to control the flow of gasses through the crankcase and transfer ports.

Four strokes need no back pressure to function correctly, although changing an exhaust to one that produces less back pressure would lean out the mixture. On a modern vehicle the ECU would compensate for this, but a carburetted engine would require upjetting.
 
#26 ·
HammyUK said:
ItsMeKyle said:
Engines don't need back pressure, they need to be able to breathe. It could make you run leaner which would affect power.
You keep believing that twinkle - you'll be just fine...
You don't know what you are talking about fella. Have a little read and educate yourself!

exhaust backpressure on turbo engines- Never good!

Exhaust backpressure on turbo engines is one of the most misunderstood aspects in tuning to many people, but it's pretty simple- It's not good.
On non-turbo engines backpressure is a single issue, the pressure in the exhaust system, but on a turbo engine it's actually two issues, pressure in the post-turbo exhaust system, and pre-turbine backpressure in the exhaust manifold.

A lot of people still think turbo engines 'need' backpressure or they lose low down power, but that's total crap, in fact the opposite is true- The BEST post-turbo exhaust system would be no exhaust system at all. Bigger really is better for both spoolup and power, especially directly after the turbine wheel, and it's why fitting a big downpipe to a turbo engine makes a massive difference to spool especially, much more than the rest of the system; in fact some new very high performance production cars turbo have amazingly big turbine outlet elbows for this very reason.

I'm not one for going in to the science of why things are how they are, as in the real world it usually doesn't matter, but a big part of why a turbine spools is the pressure drop between the inlet and outlet, the bigger the pressure drop, the better for spool, so having as little as possible in your post-turbo exhaust is what you want.

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