[Gumby_F80]

Originally Posted by klipseracer

Currently these are made by an existing downpipe manufacturer, however they are currently a one-off product done by request. This also applies to the midpipes. Once they are all installed and everything I'll report back and maybe there will be enough interest to justify making a marketable product.

i think there is definately enough interest seeing as how they would be the ONLY true 3" dps. should pass the word on or show them this thread...

[Sniz]

Originally Posted by klipseracer

Thats why I'm having the mid pipes taper back down to 2.5". I agree that full 3" is completely overkill. It sounds nice as a number, however not necessary.

We've seen 7hp+ gains by extending the 3" turbo outlet diameter another 1-2 feet before tapering down to 2.5"... Why shouldn't we be able to expect another improvement by going another two feet? The exhaust gasses will certainly still be quite hot and I'm sure would respond well to the excess room before cooling. Remember, more than 1/2 the exhaust system is still 2.5" even after this change has been made...

yes gains will be there, but certainly minimal after you've uncorked the downpipes and secondary cats.

my car might pick up some HP for sure if I eliminate my single race cat and move to 3.5" piping, but there are other places to pick up a lot more power

You will really benefit once the baby snails are upgraded to something a little more.....grown up.

[klipseracer]

Originally Posted by Sniz

yes gains will be there, but certainly minimal after you've uncorked the downpipes and secondary cats.

my car might pick up some HP for sure if I eliminate my single race cat and move to 3.5" piping, but there are other places to pick up a lot more power

You will really benefit once the baby snails are upgraded to something a little more.....grown up.

Well. It will be hard to highlight the difference between 3" dp and 3"-2.5" dp's but I'll be happy to put up my overall dyno sheets.

[Sniz]

Originally Posted by klipseracer

Well. It will be hard to highlight the difference between 3" dp and 3"-2.5" dp's but I'll be happy to put up my overall dyno sheets.

looking forward to the data....I might be back in a n54 platform one of these days so I like keeping up to date on what works and what doesnt.

[eclipsor]

I wonder if those would even fit on an XI, what with the massively limited space and all.

[klipseracer]

Originally Posted by eclipsor

I wonder if those would even fit on an XI, what with the massively limited space and all.

I'm not sure, but I'd think that it would work.

[NiVeDh]

Subscribed for updates.

[klipseracer]

Here is an update:

[ramair311]

I was just there today - saw your DPs and mid-pipes... looking really good so far.

[klipseracer]

Originally Posted by ramair311

I was just there today - saw your DPs and mid-pipes... looking really good so far.

Wish I was local to more people...

[klipseracer]

They are about done.

[GreenPlease]

Are you using the stock mufflers? Who made those midpipes? Any chance BB could do a setup like this with some race cats?

[klipseracer]

Originally Posted by GreenPlease

Are you using the stock mufflers? Who made those midpipes? Any chance BB could do a setup like this with some race cats?

BB fab made it all. And if you want a set made with race cats, you'd have to call and make a special request... Personally I think a test pipe with removable cats is a better way to go. I'm going to have my stock cats welded with 3" flanges and test pipes flanged into my midpipes. So I'll still get the same performance as catless but I will be able to swap in the cats when I go to emissions.

EDIT: Yes, stock exhaust from the end of the midpipes back.

[Gen_E92]

Originally Posted by klipseracer

BB fab made it all. And if you want a set made with race cats, you'd have to call and make a special request... Personally I think a test pipe with removable cats is a better way to go. I'm going to have my stock cats welded with 3" flanges and test pipes flanged into my midpipes. So I'll still get the same performance as catless but I will be able to swap in the cats when I go to emissions.

EDIT: Yes, stock exhaust from the end of the midpipes back.

Why would you do that if you run 3" DPs and MPs? I would think that's not any more efficient than running the usual 2.5" catbacks with 3" DPs that tapers to 2.5" at the end.

[klipseracer]

Originally Posted by Gen_E92

Why would you do that if you run 3" DPs and MPs? I would think that's not any more efficient than running the usual 2.5" catbacks with 3" DPs that tapers to 2.5" at the end.

I was pretty sure the reason for this was obvious. Whether or not its worth while is up for debate. But its the same reason people go with 3" downpipes vs 2.5" downpipes. Why go with bigger piping you say? Well do I really need to explain the hopeful reasoning here? I'm hoping for better flow at higher rpms and boost. I think most people understand the hypothetical goal here. The restriction isn't in the mufflers so much as I want to maximize efficiency near the turbos without being too excessive, hence the drop back down to dual 2.5" which is the equivalent to a single 3.125" pipe.

Full 3" exhaust has proven losses on more than one occasion. Thats why I went back to 2.5"...

Here is a quote of a post I made on another forum:

However, don't forget that the flow diameter is not continuous throughout with my exhaust. It flows from 3" down to 2.5" just like everybody elses 3" downpipes however that extension of larger piping is extended a few more feet. The length of the exhaust also plays a role here. This is my interpretation of how it works using nothing but common sense:

Once the exhaust gasses are expelled from the turbines, they are extremely hot. As we all know hot molecules bounce around rapidly and require more space. As the temperature of those particles cool, the volume required shrinks. Yes, 3" single could flow well for a 600hp car, but there are so many factors in determining what is optimal for our cars. Flow requirements hinge on: How many cylinders? How much displacement? What RPM's were reached? All of these factors and surely more will play a part in determining optimal diameter for flow. Regardless, we've SEEN 7hp+ gains by just expanding larger than your 3" 600hp capability example by going to 4.5" diameter instead of 3.125 on the exhaust even if its for a very short time. I believe this is because the hot gasses require more room than typically necessary on paper in the first section of the exhaust system. This is poor math but if you take the average, 3.125 and 4.5 it comes to 3.81 as an average diameter of the exhaust. Take that number for what its worth.

Once these exhaust gasses cool, they no longer require such large diameter and flow capacity. So if the pipe were to remain 3" its very likely that the gasses would shrink and then slow down and start to 'tumble' and swirl inside the exhaust pipes causing turbulence because there is more room then necessary. If the 'swirling' is a bad representation then the 'pulses' of exhaust will start to slow down and smack each other causing reduced torque. These exhaust gasses become a sort of dead weight with less velocity and now will need to be pushed out of the exhaust. With a 4" dump tube right off the turbo outlet, it doesn't matter how big it is, there is no dead weight to push because the gasses are released to the atmosphere and are not being restrained inside of a pipe with only one direction to exit. This is where my concern for diameter lies and this is the reason for reducing back to a 2.5" diameter just like stock, to retain velocity of the exhaust gasses and to prevent the 'dead weight' torque/power losses. Hopefully someone can come here and scientifically explain my logic.

[chris b.]

Originally Posted by klipseracer

BB fab made it all. And if you want a set made with race cats, you'd have to call and make a special request... Personally I think a test pipe with removable cats is a better way to go. I'm going to have my stock cats welded with 3" flanges and test pipes flanged into my midpipes. So I'll still get the same performance as catless but I will be able to swap in the cats when I go to emissions.

EDIT: Yes, stock exhaust from the end of the midpipes back.

perfect!

[Gen_E92]

Originally Posted by klipseracer

I was pretty sure the reason for this was obvious. Whether or not its worth while is up for debate. But its the same reason people go with 3" downpipes vs 2.5" downpipes. Why go with bigger piping you say? Well do I really need to explain the hopeful reasoning here? I'm hoping for better flow at higher rpms and boost. I think most people understand the hypothetical goal here. The restriction isn't in the mufflers so much as I want to maximize efficiency near the turbos without being too excessive, hence the drop back down to dual 2.5" which is the equivalent to a single 3.125" pipe.

Full 3" exhaust has proven losses on more than one occasion. Thats why I went back to 2.5"...

Here is a quote of a post I made on another forum:

I think you misunderstood. I can see the potential benefits of 3" MPs...but IIRC the stock exhaust is 60mm (2.36") and pancaked badly in several locations. Not to mention the weight savings if you go with complete catback system.

My point is, if you are using the 3" MPs and then stock exhaust rest of the way, the difference would be negligible compared to the usual 3" DPs and 2.5" catback. I thought you're gonna do custom 2.5' piping and mufflers after the MPs?

[amsfighter]

Originally Posted by klipseracer

However, don't forget that the flow diameter is not continuous throughout with my exhaust. It flows from 3" down to 2.5" just like everybody elses 3" downpipes however that extension of larger piping is extended a few more feet. The length of the exhaust also plays a role here. This is my interpretation of how it works using nothing but common sense:

Once the exhaust gasses are expelled from the turbines, they are extremely hot. As we all know hot molecules bounce around rapidly and require more space. As the temperature of those particles cool, the volume required shrinks. Yes, 3" single could flow well for a 600hp car, but there are so many factors in determining what is optimal for our cars. Flow requirements hinge on: How many cylinders? How much displacement? What RPM's were reached? All of these factors and surely more will play a part in determining optimal diameter for flow. Regardless, we've SEEN 7hp+ gains by just expanding larger than your 3" 600hp capability example by going to 4.5" diameter instead of 3.125 on the exhaust even if its for a very short time. I believe this is because the hot gasses require more room than typically necessary on paper in the first section of the exhaust system. This is poor math but if you take the average, 3.125 and 4.5 it comes to 3.81 as an average diameter of the exhaust. Take that number for what its worth.

Once these exhaust gasses cool, they no longer require such large diameter and flow capacity. So if the pipe were to remain 3" its very likely that the gasses would shrink and then slow down and start to 'tumble' and swirl inside the exhaust pipes causing turbulence because there is more room then necessary. If the 'swirling' is a bad representation then the 'pulses' of exhaust will start to slow down and smack each other causing reduced torque. These exhaust gasses become a sort of dead weight with less velocity and now will need to be pushed out of the exhaust. With a 4" dump tube right off the turbo outlet, it doesn't matter how big it is, there is no dead weight to push because the gasses are released to the atmosphere and are not being restrained inside of a pipe with only one direction to exit. This is where my concern for diameter lies and this is the reason for reducing back to a 2.5" diameter just like stock, to retain velocity of the exhaust gasses and to prevent the 'dead weight' torque/power losses. Hopefully someone

This reminds me of the original TurboXS turboback exhaust system for subies. Went from 4"@dp>3"midpipe->2.5" axleback. Their logic was based off of basic bernoulli's principle and venturi effect...later, they amended their design to eliminate the 2.5" reduction b/c people were seeing gains on the dyno with a full 3" midpipe w/o the 2.5" reduction.

Will be interesting to see how things go with this. I'm definitely excited and waiting to see if this becomes available to the general public!

[klipseracer]

Originally Posted by Gen_E92

I think you misunderstood. I can see the potential benefits of 3" MPs...but IIRC the stock exhaust is 60mm (2.36") and pancaked badly in several locations. Not to mention the weight savings if you go with complete catback system.

My point is, if you are using the 3" MPs and then stock exhaust rest of the way, the difference would be negligible compared to the usual 3" DPs and 2.5" catback. I thought you're gonna do custom 2.5' piping and mufflers after the MPs?

Ah I see. The plan is a custom exhaust, but not at the moment. I'll be sporting a slip joint onto stock exhaust or type of adapter to make it work for the current moment. Then in a few months I'll have a custom 2.5" exhaust made. It may also be easier to pick up the bmw performance exhaust also at this point considering I cut the midpipes at exactly the same point that the bmw performance exhaust connects for this very purpose.

[roozie2001]

Originally Posted by cstavaru

They may gain a market. Selling a combination of 3" downpipes and 3"-2.5" tapered midpipes as a package with a nice discount may gain some traction...not bad.

i think that would defeat the whole purpose of going 3 inch right? if ur gonna go 3 inch might as well go all the way to the tips 3". Just my opinion. this is gonna be necessary soon as those bigger turbos come into play.

[klipseracer]

Originally Posted by roozie2001

i think that would defeat the whole purpose of going 3 inch right? if ur gonna go 3 inch might as well go all the way to the tips 3". Just my opinion. this is gonna be necessary soon as those bigger turbos come into play.

Yes, I had this mindset as well. But I promise you going too big will cause a loss in power/tq.

[klipseracer]

Originally Posted by amsfighter

This reminds me of the original TurboXS turboback exhaust system for subies. Went from 4"@dp>3"midpipe->2.5" axleback. Their logic was based off of basic bernoulli's principle and venturi effect...later, they amended their design to eliminate the 2.5" reduction b/c people were seeing gains on the dyno with a full 3" midpipe w/o the 2.5" reduction.

Will be interesting to see how things go with this. I'm definitely excited and waiting to see if this becomes available to the general public!

Perfect!

Considering they have two less cylinders then I'd expect to be right in the ball park. They went from an overall diameter of 4" -> 3" with 4 cylinders. I'm going from an overall diameter of 4.5" -> 3.125" with 6 cylinders.