Audi TT225 Compound Turbo Build

[Dowski12]

Ok, I have a build thread for this in the TT MK1 forum, but I figure I'll post it here too since I'll be meeting alot of you guys as soon as its done. Enjoy

Motor built and installed with powder coated valve cover and SEM intake mani









Both turbos back from welding and powder coat

[Dowski12]

IC mounted and cold side pipe finished and looking pretty






Header welded up and polished, ready for chrome ceramic coating





More to come...

[vegaspassat]

kick ass keep us posted!

[hans j]

Awesome project!

[Dowski12]

Thanks fellas, definitley will keep updating as things are happening.

[Hybrid_Hatch]

I'll be watching this for sure!

[corradoswapT]

pardon my ignorance, but what is the real bennifit of a compound turbo set up on a small motor that really cant handle high boost? Ive seen diesels run these to acheive 120-140 psi but thats a cummins running 8 seconds. a sequential turbo setup I can understand. anyhow I cant wait to see how this turns out.

[Dowski12]

Imagine a 500hp car that spools somewhere in the ballpark of 2500rpm. That is the benefit of having a compound turbo car. Yes, diesels have been doing this for a long time and some have pushed their boost all the way to 200psi and thats great if your motor can take it. You also have to consider that diesel motors rev much lower than our cars and have narrower power bands, so they have a much smaller window to utilize the power their creating. We don't need to creat 120psi to make big power like they do. 30psi is considered a relatively high operating pressure on small motors like ours, but in reality I could push this setup to around 50-60psi as long as the motor can take it. I'd rather not blow my motor up so in the mean time, i'll stick with 30

[corradoswapT]

makes sence. sounds like this is going to be a beast at launch!

[Dowski12]

Yeah as long as it doesn't explode and "launch" me straight to the moon If you wanna check out some end results, look up streetfighter on youtube. Its pretty sick

[Dowski12]

Got my Sigma 6 short shift kit in the mail

[Levi20AE]

What turbo combination will you be running?

[Dowski12]

The small turbo is a VF39 from a WRX and my large turbo is a 60-1. At first they weren't a perfect match up so we swapped the 39mm wheel in the VF for a 40. We also changed it from a journal bearing to a dual ball bearing to make sure the bigger wheel didn't hurt spool at all. Great thing about this combination is if in the future I decide to up my hp, its just a matter of swapping the 59mm in the 60-1. With my housing I can fit all the way up to a 67mm before I would have to swap turbos, and as long as I dont swap hotsides it will still match up with the VF39.

[Dowski12]

Throwing around the idea of making a full tube frame for my car. What do you guys think?

[pete@integrated]

Skip it, if you plan on ever driving it again...

[Dowski12]

Why's that?

[pete@integrated]

It'll just be a terrible street car by the time you are done, guaranteed. To be honest, if you want a nice street car throw on the VF40 or a GT3071r and be done.

[Dowski12]

haha...Im alittle past just slapping on a single turbo, and this is not just a street car. Eventually this wont see the street except maybe for quick fun runs through the canyons or maybe to the corner store when Im getting the itch to drive it

Agreed though, that with a tube frame it would make a horrible street driven monster haha.

[Levi20AE]

Take no offense to this question, but have you built a big turbo car before? A 3076 will get you really close to your power goals on a AWD and it will be livable. Be fast on the track is all about seat time in a predictable car. You will have more time to spend suspension tuning, which really brings your times down. Why compound turbos? You have six gears, just pick the right one and you will always be in the powerband. Buying tires will keep you broke if you keep it out at the track much anyways. Best of luck, and have fun with it.

[Dowski12]

haha...no offense taken what so ever. Yes I've had big turbo cars before, but not on a VAG car. I really want something that will out perform anything I could do with a single turbo. Yes, I could just buy a 3076 and I know I could be happy with it, but I also know I will get tired of my current setup at some point and would really like to be able to push the limits without having to buy a new turbo. Ideally, I could swap my 59mm with a 67 and make close to 700hp (I couldn't dream of doing that with a 3076). I also wanted to do something new, something no one else has done on a 1.8T. Not to mention its just plain bada$$

I know not everyone is going to agree with me, and that is almost always the case when doing something different, but as long as I'm happy with it in the end thats all that really matters to me.

In the works of getting a sponsor for tires so should be covered there

[Dowski12]

Sigma 6 Short Shifter Installed

[Dowski12]

Just thought I would snap a couple of pics, since the turbos should be in the car in the next day or two...stay tuned

[Dowski12]

Turbos are finally in the car...









Everything is tach'd in place for now and I'll try and get better pictures of the header and up pipe later. We still need to fab up the pipes for the waste gates and the elbow from the large turbo to the small turbo's inlet, but I'm pretty happy with the current progress

[Dowski12]

Not much progress, but its somethin...





I know the transition pipe between the turbos is welded and ground so I'll get more pics tomorrow morning.

[DarkSideGTI]

That tiny turbine housing is a big restriction for the second turbo. I don't see this having much top end.

If you wanted to go custom and have great spool I think a GTX3076R with a modified twin scroll housing would be pretty slick. People are adding a flapper in the twin scroll housing with an actuator so you can spool quickly without having a twin scroll manifold.

[Dowski12]

Your right, I should change my entire setup and go with a single 3076, and be just like everyone else, why didn't I think of that? Nevermind the money I have invested in my current setup...you cant take it with you right?

On a seriouse note, I'm way beyond a single setup at this point. A compound setup is what I had planned from the first day I bought my TT and I'm sticking to it. It's never been done before on a TT, which in my opinion makes it much more bada$$ than any single turbo setup. And with or without a little flapper on a twinscroll, I bet I still spool faster than any 3076 out there.

Top end wise I think Ill be ok. Most of the exhaust gasses are going to bypass the smaller housing through the wastegate anyway, so it shouldn't hurt my top end too much. Right now we are going to run a 38mm Tial, but if it proves to be restrictive then we will put a 44mm in its place.

[DarkSideGTI]

There's a reason people go with single 30R setups.

A 38mm WG is an even bigger restriction than that turbine housing.

[Levi20AE]

what are you doing for stand alone and boost control for both circuits, that is going to be a chore to get to run smoothly and you should look into building a bypass for the first stage turbo. Not only will the exhaust restriction prevent the potential spool of the second stage but the EGTs are going to quickly limit your available power for any duration of time.

[Dowski12]

There's a reason people go with single 30R setups.

A 38mm WG is an even bigger restriction than that turbine housing.

Well, we wont know till its done I guess, that is unless you, yourself have built a compound setup before...must have missed that build thread

JC has done a similiar setup before, and I have complete confidence in his abilities. If he says it will get me to my power goals then I have no reason to question it.

Yes the 38mm by it self is a restriction, and yes the smaller turbine housing is a restriction, but the combination of the two should supply the 60-1 with enough flow to make my desired power. As I said before, if the 38mm isn't large enough to get the job done, it will be replaced with a larger wastegate.

[Dowski12]

what are you doing for stand alone and boost control for both circuits, that is going to be a chore to get to run smoothly.

Im using maestro to tune and as far as boost control, right now each turbo will be preset to a specific psi, running off the wastegates. Later I plan on running tandem boost controllers, one for each turbo but controlled by one source(preferably a touch screen) so I can adjust my boost while maintaining the pressure ratio between the turbos.

and you should look into building a bypass for the first stage turbo. Not only will the exhaust restriction prevent the potential spool of the second stage but the EGTs are going to quickly limit your available power for any duration of time.

What your describing is a sequential turbo setup, only one turbo is actually producing boost at a time. The smaller one for down low power and then through a solenoid of some kind, the small cuts out and is bypassed just as the larger turbo comes on hard. Totally different setup then what I'm doing and a whole lot more complex. The whole point is to keep both turbos spooled, just bypassing the extra exhaust gasses around the smaller one through the wastegate and back into the larger turbo. The smaller never stops feeding the larger turbo in my setup. The wastegate isn't meant to supply the larger turbo with 100% of it's flow, it's just there to bypass the excess exhaust that the smaller turbo doesn't need to maintain its preset pressure. Being as that this has never been done before on our cars, its going to have to be alittle trial and error before everything is perfect, but I know its doable...I hope

As far as the EGT's, Im not 100% on how hot this sucker is really going to be. Im going to be running E85, and direct port W/M injection so I'll have to wait and see how high my temps actually get.

[DarkSideGTI]

I know a bit about compound setups. One of my good buddies is running a compound setup on his truck.



The difference is his small turbo is a GT37R and the large one is a BW S378

[Dowski12]

Is he running one wastegate or two? It was explained to me by a diesel guy that the way they run and tune their compound setups is they only use one wastegate on the small turbo, crank up the boost, and control it by tuning their fuel down till they hit their desired level of boost. If that is the case, they don't have to worry about bypassing turbos and what not. I wish my setup could be that easy

[DarkSideGTI]

Is that picture working? You can see a big WG on the large turbo. No point in controlling the smaller turbo, may as well max that out.

[Dowski12]

My bad, I said that backwards, I meant on the large turbo. Thats why I was asking because you cant see the small turbo or a second wastegate.

[DarkSideGTI]

I don't think he is. I would though on a car.