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Discussion Starter · #1 ·
THESE WERE MY COMMENTS WHEN I STARTED THIS TOPIC BUT SOME THINGS HAVE CHANGED SINCE THEN. IF YOU'RE READING THIS FOR THE FIRST TIME, PLEASE ALSO HAVE A LOOK AT MY LATER COMMENTS FOR THE WHOLE STORY.

Chris

For all those looking for a Milltek DP, my suggestion is to pay the extra and go for the 2.5" one.

I admit that I haven't tried the 2.5 " one, but my suggestion is based on the many niggly issues that I, and others in the US, have noted with respect to 3" DPs generally. I have not seen as many reports about issues with 2.5" DPs and Milltek 2.5" owners seem very happy with their products. Other than price, I can find nothing to recommend the larger DP over the smaller one.

Finally, just to put my comments in context, I think that the 3" DP is a good product that gives significant gains over the stock system. IT IS NOT A BAD PRODUCT AND I AM NOT UNHAPPY WITH IT. However, I wish I had stuck to my original choice of the 2.5" one as I think I would have had fewer fitting, vibration and noise issues and would be happier overall.

Anyone wishing to do further research on this topic should search the VWVortex threads for the past couple of months. Many of the comments apply to 3" DPs generally and not to Milltek specifically. However, the problems all sound boringly and depressingly similar.

Just my 2 cents worth for those purchasing soon.
 

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Cheers Stewart, this could be well worth investigating for both of us!

What makes me wonder is the pricing, I paid over ?400 inc VAT for my Milltek 2.5" DP and 200cell cat yet these 3" DP's with 100cell cats are far less money.

I've had people telling me that I would experience a loss of low down torque with a 3" DP compared to a 2.5" DP but I was always under the impression that back pressure wasnt an issue with a turbo and you could practically run straight out of the turbo without an exhaust.
 

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Exactly! Turbocharged cars operate most efficiently when there's little or no backpressure , the bigger the exhaust, the the faster the turbo can spool up, so the sooner you'll get your torque and power.
 

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Discussion Starter · #5 ·
Stewart and Gary,

I didn't want to bore everyone to death with all the gory details but most of the issues relate to vibration, rattling and noise. Here's a long thread that covers a lot of it

http://forums.vwvortex.com/zerothread?id=1501848

and another one related to the dreaded ticking noise

http://forums.vwvortex.com/zerothread?id=1624767

more on vibes

http://forums.vwvortex.com/zerothread?&id=1589403

On the subject of power, here is a quote that comes from this topic (http://forums.vwvortex.com/zerothread?id=1638123

"As for 2.5" vs. 3.0", the "best" turboback exhaust depends on the amount of flow, or horsepower. At 250 hp, 2.5" is fine. Going to 3" at this power level won't get you much, if anything, other than a louder exhaust note. 300 hp and you're definitely suboptimal with 2.5". For 400-450 hp, even 3" is on the small side."

What I'm saying is that you seem to get more noise and vibration with the 3" and little else. I have no absolute proof of that, it's the impression that I have from the way mine behaves compared with the comments made by the people with the 2.5" ones. I don't think you make any more power with the 3" one if you're in the 200-250hp bracket. Spool-up may be a bit better but that's it and even Milltek didn't claim that when I talked to them. The 3" cat will probably not last as long either, and some people have had occasional CELs already. Finally, my understanding is that the Milltek 3" DP is not rated for high power outputs because of the quality of the cat so what's the point, apart from price?
 

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Can't understand why vibration should be an issue? Not read those Vortex links yet but unless the DP is touching something else, why should there be more vibration?
 

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"Milltek 2.5" DP and 200cell cat yet these 3" DP's with 100cell"

Think thats the other way round Gary? my 2.5" Miltek has a 100cel cat... less needed as its of a better quaility.
 

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I thought the 100 cell cats were used on Non DBW AGU's as theres no post cat sensor? I have a DBW AUQ which AFAIK uses a 200cell cat.

Now if somebody tells me that Im definatly wrong and I have in fact got a 100 cell cat I'll be a happy man.
 

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Yep as I'm sure when I spoke to Miltek last they said they had up'd the cell brick in the single lambda setup due to emmisions problems to 200 and the 3" runs a rare old 100 cell and 50 cell brick setup to give 150...
 

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Discussion Starter · #14 ·
Quote: posted by Stewart on 22/10/2004 08:23:54

Can't understand why vibration should be an issue? Not read those Vortex links yet but unless the DP is touching something else, why should there be more vibration?

I'm not sure either and I know that my DP is definitely not touching. It could be to do with the difference in the way stainless steel and mild steel behave perhaps, maybe the bigger pipe acts more like a lever and has less natural flex, maybe less give in the flex joint, maybe resonance caused by the air flow in the pipe. All I can tell you is that there seemed to be much more up and down movement at the end of the 3" DP with the stock dogbone. The poly dogbone bush now keeps the movement under control but at the expense of some vibration. I'm not just talking about vibration at idle either, I mean vibration when stepping on it. It's not massive but enough to move the car from the "wow your car is just so smooth" category if you know what I mean. It's also not constant which is annoying. One day there's hardly any of it, other days it's more noticeable. It's now caused something else like a heat shield to start vibrating at the same frequency around 2000 rpm. Will investigate this week-end.

I would have said it was just me and my car if others hadn't reported vibration too. Once again, these are guys with 3" DPs of various kinds, not just Milltek.
 

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I have just been on the phone to Milltek who confirmed that the only 100cell cats produced with 2.5" downpipes were the very early ones, she said that they have only been providing 200cell cats with 2.5" downpipes for quite a while now.

She said the new 3" downpipes come with 100cell cats which were just lower in price, the quality was the same as the 200cell units.
 

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Mine is 12 months old but she said only the first batch or so had 100cell cats.

When did Milltek enter the Golf MkIV scene?
 

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Gary back to your "torque" issue...... its down to the back pressure that you "feel" a loss of torque. Becuase the turbo can breath easier is spools up smoother and boost comes in nice and smooth. Thats why on a standard restrictive DP you get a kick at 3krpms, cos its restricted then all of a sudden.....BOOOM it hits you and pins you back. with the wider better flowing DP its so smooth you dont really get the kick!

So you dont loose torque you just "FEEL" like you have!
 

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Thanks for the explanation Tim, that makes perfect sense.

Im still dubious as to whether an increase in power would be felt between the two systems with around 240bhp at your disposal.

Obviously nearer the 300bhp mark it would be a necessaty to go for a 3" system.
 

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Discussion Starter · #20 ·
From the logging I've done recently, I can see that mine gets a move on from as low as 2000 rpm and the way the boost gauge needle whips round shows that boost builds very quickly. Definitely an improvement over the stock system and very much as Tim has described.

Gary if you'd like to compare the two in the interest of science I'm sure a lot of us would be fascinated in the results but I think they would be disappointing for anyone who already has the 2.5" DP. Yes, you'd need a 3" nearer 300HP but you'd also need a different cat from what I can gather.

If there is a difference between the systems surely it's going to be shown in spool time or something similar. Our cars are all different because of the various mods we've done but it would be interesting to collect a whole load of logs over say 2000 rpm to 5000 rpm just to see how much variation there really is. It's not very scientific but it would give an idea of variation and how much potential there is for gains with these simple bolt-on mods.
 
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