5.0 Turbo build w/CPR's prototype kit!!! Warning: Pic heavy!!!

[truebluedevil02]

Ahhhhh yes, let the experts hash it out! I'm just here to drive the car and make it look good! LOL!

:beer:

 

[acrbill]

Any pics of how the exhaust runs? It looks like it will run under the K member. I assume the K member you designed takes this into account I am just curious.

 

[CPRsm]

Here's the GT500 k-member. Same idea, a little different because of the new elec rack though. But the bar moves up and behind the rack to clear room. Then, oval tubing passes under that bar

Car is so low here I had to take the bumper off to get my car on the trailer. LOL

 

[Scuba-Matt]

Great workmanship, Very nice build.

 

[keoni1984]

Progress..

 

[CPRsm]

This is in no way a poke or jab. But this was posted yesterday and happened to stumble across it today. Thought I'd share. I've seen him post here and there on another site. Always on EFI and the dude is VERY smart. An instructor at EFI university.

If you are running your O2 sensors pre turbo then be aware of a few things,
#1 the exhaust temp is higher before the turbo inlet... so all the way from the port to the turbo inlet.
#2 as back pressure increases and it will, the reading the O2 will show will be richer than it actually is.
#3 the hi exhaust temp may kill O2 sensors in a shorter time.

I also brought this up as one of the problems of Hellions kit. I remember him saying "It's unfortunate people have to make up lies." Although I'm still here and waiting for them to come and show where I lied about anything. Suppose it's hard when I have data and video to prove it though.

 

[12GTPDX]

The welds I'm seeing in the photos are just beautiful ... could be from an instructional guide on how to lay down clean welds!

Nice work!

 

[keoni1984]

The welds I'm seeing in the photos are just beautiful ... could be from an instructional guide on how to lay down clean welds!

Nice work!

Especially after seeing this in person and comparing to other kits...

 

[CPRsm]

LOL, not quite there but thanx guys. Some of these guys that do it all day long every day would embarrass me. Until I weld like John here, I will be making no book lol. Marcella Manifolds - images

 

[seank]

You are 150% wrong. How is backing up exhaust gas After the turbine wheel going to Increase spoolup? If your slowing the turbine down, your slowing how fast it spools up. You can NEVER go too large on a downpipe.

Backpressure is NEVER good post turbine. A 1:1 ratio Pre turbine is good, but you never want back pressure because your exhaust is restricting the turbo.

On a race car you are 100% correct. On a street car there are many more packaging issues and it doesn't make sense to have a gigantic turbo outlet that immediately necks down to the rest of the exhaust system that doesn't just dump right off the downpipe, there will be more back pressure because of the drastic change in x-secton. Ideally you want a slightly increasing diameter, aka a cone, exit on the exducer of the turbine, which will reduce pressure and increase velocity.

Still not knocking this setup it looks AWESOME!

Those manifolds just posted are works of art, absolutely stunning work!

 

[90goldtsiawd]

Sub'n for results! Kit looks great! So this will be getting the GT4202 or a different turbo?

 

[StevenStarke]

On a race car you are 100% correct. On a street car there are many more packaging issues and it doesn't make sense to have a gigantic turbo outlet that immediately necks down to the rest of the exhaust system that doesn't just dump right off the downpipe, there will be more back pressure because of the drastic change in x-secton. Ideally you want a slightly increasing diameter, aka a cone, exit on the exducer of the turbine, which will reduce pressure and increase velocity.

Still not knocking this setup it looks AWESOME!

Those manifolds just posted are works of art, absolutely stunning work!

So what your saying is a 5" downpipe going into twin 3" downpipes is WORSE than a 4" downpipe going into twin 3" downpipes? The diameter of the twin 3" downpipes is a negligible neck down. Would you agree that 4.25" exhaust would NOT be a restriction on a coyote motor making under 1000whp? With an external wastegate dump remember (on mine at least). The twin 3" pipes are equal to a 4.25" exhaust. If you think a 5" - 4.25" reduction is going to cause any backpressure issues at these power levels your mistaken. And going straight 4.25" off the turbo and never changing in diameter vs going from 5" - 5.25" would NOT be better.

The area of a 3" circle is 7.065 cm2 so two of them is 14.13 cm2.

The area of a 4.25" circle is 14.179 cm2

The area of a 5" circle is 19.62 cm2.

 

[CPRsm]

On a race car you are 100% correct. On a street car there are many more packaging issues and it doesn't make sense to have a gigantic turbo outlet that immediately necks down to the rest of the exhaust system that doesn't just dump right off the downpipe, there will be more back pressure because of the drastic change in x-secton. Ideally you want a slightly increasing diameter, aka a cone, exit on the exducer of the turbine, which will reduce pressure and increase velocity.

Yes, a cone would be a bit nicer, it's literally rocket science and have studied it some what to understand it better. Very interesting to say the least. Gave me some other ideas to experiment w also. But like you said, space. So I'm sure I could be causing vacuum in the corners a bit if the angle isn't perfect for the application. But this should only have a 4in downpipe by the housing flange. I think the pressure drop will be worth any possible losses from the wrong angle. The angle I have is actually CNC'd into the V-band, so it's not just a flat surface dump. But, even with the flat surface dump I have done before because I just cut and welded on a v-band, worked great. I see what you are talking about more in the import world, and makes sense. Exh dumps into the down pipe which is larger and the exhaust slows and backs up the gases exiting behind it. Problem is though in everything I have seen and tested it hasn't caused a problem. It always pick up. I would have liked some more room to give the gas more time to go from rotational to linear flow, but again space. I did think about a 4in for that reason, but chose larger in the long run. Don't worry I don;t think you;re knocking it. I've always asked people to ask questions. For the most part I want people to know why I did it, and why it's better than the way others do it.

Sub'n for results! Kit looks great! So this will be getting the GT4202 or a different turbo?

Yeah son! GT4202. Sizeable from 64-91mm LOL

 

[seank]

So what your saying is a 5" downpipe going into twin 3" downpipes is WORSE than a 4" downpipe going into twin 3" downpipes? The diameter of the twin 3" downpipes is a negligible neck down. Would you agree that 4.25" exhaust would NOT be a restriction on a coyote motor making under 1000whp? With an external wastegate dump remember (on mine at least). The twin 3" pipes are equal to a 4.25" exhaust. If you think a 5" - 4.25" reduction is going to cause any backpressure issues at these power levels your mistaken. And going straight 4.25" off the turbo and never changing in diameter vs going from 5" - 5.25" would NOT be better.

The area of a 3" circle is 7.065 cm2 so two of them is 14.13 cm2.

The area of a 4.25" circle is 14.179 cm2

The area of a 5" circle is 19.62 cm2.

No, I never used numbers and you chose sizes that are acceptable. The point I was trying to make is that making broad sweeping statements that bigger is better is wrong. You need to consider the system as a whole.

4.25" exhaust I agree would be fine.

As CPR pointed out above going unecessarily large and then dropping back down to a smaller diameter especially if it is 12-18" post turbo, the flow will just begin to back up. The more drastic the change the higher the friction losses will be and the greater increase in back pressure you'll see.

My experience is from smaller displacement import motors. But I did testing on an A4 I had with a 2.75" and 4" testpipe. Going to the 4" lost torque down low and only gained ~5hp up top making it not worthwhile. AWE Tuning who specializes in VW/Audi/Porsche has similar experiences documented on their website if you are interested.

 

[Turbo900rr]

This is why I love svt! Lots of good info and pissing matches kept to a minimum. Great info here guys.

 

[CPRsm]

As CPR pointed out above going unecessarily large and then dropping back down to a smaller diameter especially if it is 12-18" post turbo, the flow will just begin to back up. The more drastic the change the higher the friction losses will be and the greater increase in back pressure you'll see.

My experience is from smaller displacement import motors. But I did testing on an A4 I had with a 2.75" and 4" testpipe. Going to the 4" lost torque down low and only gained ~5hp up top making it not worthwhile. AWE Tuning who specializes in VW/Audi/Porsche has similar experiences documented on their website if you are interested.

I also weighed heavily on making a nozzle w a calculated cone because I had the room if I went w a tight radius 5in bend. I couldn't have both though. For now have decided a shorter cone w an 8in radius on the 5in. Sean, I think cid VS down pipe area has to play a role in return. An Audi (2.0 liter) with a 4in down pipe (about 6.28in in down pipe area per liter) would be like coyote with a down pipe a little over 6.25in in diameter. Engine liter to area of down pipe being the same. I think this size is a bit more appropriate for the volume this engine is going to crank out.

 

[CPRsm]

Oddly enough, this is an Audi....Audi TT RS turbo irrc. Know anything on it Sean, or any changes the aftermarket made to this system to improve?

 

[seank]

I also weighed heavily on making a nozzle w a calculated cone because I had the room if I went w a tight radius 5in bend. I couldn't have both though. For now have decided a shorter cone w an 8in radius on the 5in. Sean, I think cid VS down pipe area has to play a role in return. An Audi (2.0 liter) with a 4in down pipe (about 6.28in in down pipe area per liter) would be like coyote with a down pipe a little over 6.25in in diameter. Engine liter to area of down pipe being the same. I think this size is a bit more appropriate for the volume this engine is going to crank out.

I agree the 4" was poorly sized. I had a free weekend, a few cases of beer, and a length of 4" tubing and said what the hell, bigger is better right? Wrong!

In general I think tubrine THEORY and I highlight theory says 8-12 degrees of taper out of the exducer for optimum performance. This is purely dragging numbers out of my cloudy brain on hot afternoonthough so don't hold me to that. And we all know theory is only good to start with you need to do real world testing to catch all the variables.

Honestly, I think your setup looks great. And I think going with a nozzle and tight radius wouldn't have produced much for you because of the tight radius right off the turbine. My only concern, and we talked about it before in another thread is how much heat is going to transfer from your downpipe to the intake manifold inlet sitting just above it. Perhaps some DEI gold foil on the intake pipe? I saw ~15-25 degree decreases in intake air temp on my STI after wrapping the factory airbox with that stuff.

I know nothing about that Audi turbo but as you can see they do have the nozzle there at the exducer. I've been out of the Audi scene for about 4 years so I'm not too up to date on what's going on. I can talk with my friend who is an engineer at AWE Tuning and see if he knows anything.

Awesome job man, and I'm glad your not as cagey as some others on here and willing to talk through stuff rationally and view all sides of a problem.:beer:

 

[keoni1984]

Wow, this is awesome! Sooo much info in this thread, the learning never ends. Welcome to turbo college, everyone!!

 

[CPRsm]

Wow, this is awesome! Sooo much info in this thread, the learning never ends. Welcome to turbo college, everyone!!

Nahhh, was told it was so easy a caveman could do it. Hence my avatar. It's just tubing. Then the same guy was asking for help a few weeks later about building a kit on another website. :lol:

I agree the 4" was poorly sized. I had a free weekend, a few cases of beer, and a length of 4" tubing and said what the hell, bigger is better right? Wrong!

Hell, you gotta start somewhere. Lots of good shit is just stumbled across by experimentation. I've done it. Some made me drink more because they didn't work and I wanted to cry from wasting so much time lol.

In general I think tubrine THEORY and I highlight theory says 8-12 degrees of taper out of the exducer for optimum performance. This is purely dragging numbers out of my cloudy brain on hot afternoonthough so don't hold me to that. And we all know theory is only good to start with you need to do real world testing to catch all the variables.

That sounds about about right. There was more on the convergent angle and nozzle size that would dictate that divergent angle..... But it would all change with different turbine size. So I'd be chasing a ghost unless I made ea different for ea turbine size. F all that noise lol.

Honestly, I think your setup looks great. And I think going with a nozzle and tight radius wouldn't have produced much for you because of the tight radius right off the turbine.

Actually the larger radius puts the bend right at the turbine...if they end in the same place. The tighter radius would have left me straight after the turbo for the cone. But then stuffed it in a sharp 90deg bend which I didn't want to do if I didn't HAVE to.

My only concern, and we talked about it before in another thread is how much heat is going to transfer from your downpipe to the intake manifold inlet sitting just above it. Perhaps some DEI gold foil on the intake pipe? I saw ~15-25 degree decreases in intake air temp on my STI after wrapping the factory airbox with that stuff.

Did your inlets drop at wot? As long as the tube isn't effected at WOT I'm fine with that. Even with coating it's going to heat soak to a point. Then the intercooler will cool it off. I've seen some ideas I like if need be though.

I know nothing about that Audi turbo but as you can see they do have the nozzle there at the exducer.

You saw that. :beer: Liked how they kept the wastegate way out of the way.

Awesome job man, and I'm glad your not as cagey as some others on here and willing to talk through stuff rationally and view all sides of a problem.:beer:

;-)