EVIL ENGINE goes Twin Turbo - Your Chance to Design the 930tt Exhaust System

[mb911]

my turbo setup uses a straight through design you can stick a small childs arm all the way through. and it is very reasonable in all rpm ranges. more so then our NA counter parts mufflers. My can is 14 inches long . this would be complicated by the twin turbos but can still be done

[MattAlpha]

Wouldn't it be nice if someone had a CAD program with all of your turbo parts/components already programed into it. Then you could try several arrangements and if it were a really nice program it might tell you simulated pressures and so forth. Just a dream, but I know such programs exist. They're developed by major automotive and airline companies. Too bad for us, maybe there is someone on this forum that is in the inside.

Just a thought, I'm not serious.

The picture of the 993 turbos do look like exact copies of one another. Even if they are a set, it looks like their orientation in the engine will not be symmetric (one will have to be turned 180 degrees) in relation to the other one.

[sand_man]

I'm changing my vote to rear mounted! That freaking engine of Amac's is just scary (good scary)!!! Heat management might also be better with rear mounted...not having the turbos located so close to the valve covers. I dunno, maybe it's a moot point.

[sand_man]

Maybe this will be discussed in another thread of yours, but CIS? Or some form of simple EFI?

[RarlyL8]

The induction system will not be discussed in this thread. I have something planned and will divulge after the exhaust side is taken care of.

Rear mount has a total bad-ass component. Not a bad thing at all!

[RarlyL8]

Got the twins mounted up front today. Jury is still out on that one. There is very little room for everything that has to be plumbed. When you look at the turbos hanging in the air up front it does not look "natural" for lack of a better description. The side mount configuration has a better relationship to most plumbing issues.

Does anyone know how high or low the turbos need to be in relation to the case? Stock 930 oil tanks and oil circulation system will be used. I assume there is no restriction on the inlet side but don't know about the scavenge pump return flow.

[ZLP]

Most rear mounted twin set up have the exhuast sides facing each other...

[sand_man]

Yeah, they alost look like they need to be reversed or flipped around...

[RarlyL8]

The turbos are have the exhaust facing out because the bumper on my car is too low to allow twin tailpipes in the center. I would rather not have to change bumpers unless I have to.

In this picture you can see the bumper places the license plate low due to an air duct above the plate to vent the hot exhaust system.

One more hurdle for the rear mount design ..........

[Lukesportsman]

Brian,

I see you've passed me in your designing. I've taken a break from the TT's this summer to play with the Mustangs and drive. I'm subscribing and will watch with interest. I'm still thinking side mount, but I don't have the benefit of a 930 oil pump.

I like the weight low, but not necessarily any further back than necessary. I'm sure you've toy'd with this but you ask pro vs. cons. Are your shorty's SS? Durability?

[RarlyL8]

Hey Luke, long time no hear.
Don't know what material the shorties are made of. They are thermal reactor replacements for early US 930s. Very good construction but have a small ID compared to N/A headers. Interestingly the collectors are the same ID as the 993tt turbo inlets.

I have considered the weight bias of rear vs side mount turbos. With the elemination of any muffler on a rear mount system it seems like a wash. I am concerned about noise level - I have never personally heard a rear mount twin turbo 911 but cannot stand the Zork tube noise of a single turbo 930. Stephen Kaspar's rear mounted TT, "Monster", was sold buy him some time ago partially because of the noise.

Next I will mount the turbos on the sides and see how I like that. The dual plumbing involved is simplified in a rear mount design. The turbos are close together and can share some plumbing. Side mounts have two of everything. You also complicate valve adjustments and oil leak repairs with side mounts, but that is a minor detail. I also don't know how much interfearance there will be on the passenger's side with the oil tank and lines.
On the plus side you have easy muffler fitment, shorter header run, and possibly better weight distribution.

Another plus is that if I use the shorty headers I can sell the 993 heat exchangers with flipped flanges along with a matching M&K muffler. That alone should recoupe all my costs so far.

What have you decided with your project? Still going with the 993tt headers and 996tt intercoolers?

[beepbeep]

Hello!

A hint: It's easiest to rear-mount the turbochargers with exhaust flanges face to face, then let exhaust pipes cross each others and let them go inside of small cherry-bomb silencers hidden behind rear valance.

That way you don't need long oil hoses and Y-joint of air hoses is much simpler (in case you really want to use CIS).

[Lukesportsman]

I'm just about as bad as you in the parts collecting. I've got early HE's & 993TT's. I've got the 996TT IC's along with a universal, rough core and air/liquid coolers looking at me. I have the GT20's but am really questioning these. Not because of Garrets rating (should be good for 450+ hp) but because the impellers "look" smaller than just about anything I've seen with my domestic roots.

I've bid on several kkk16 combos recently on Ebay, this would make plumbing much easier. I concour that the 993TT primaries and collectors are very small.

[RarlyL8]

You can pick up a set of K16s for a good price these days.
what does the flange look like on your GT20s? Can you post a picture?

Well I ran out to the garage and swapped turbos per everyones suggestion. Not as bad as I thought. There is actually more room in some places.

Goran - it looks like I might be able to squeeze in a cross exhaust. My bumper is not nearly as large as the one on ItsFun2.

If I leave the turbos mounted in the rear what header configuration would work best? The 993 heat exchangers or the shorties with a connecting lenght of pipe?

[Facey]

to me it looks like the cross over ehxuast will be keeping really hot air under the bumper, near the engine for a much longer (hotter) duration then the non-cross over setup.

however, i guess i'll bow to the experience of the members who have spoken.

did u decided to go with the shorty's or the 993's?


wicked project!!!

[TerryBPP]

As far as the exhaust goes I would go the Amac way...None. I had dimensionaly the same turbo on a 318i 4 banger. Running just a 2.5" downpipe is was as quiet as my 911 was with a Flowmaster. The turbo makes a great noise reducer.

I also like how Amac merged the 2 downpipes together to use only one wastegate.

The only problem I see with the outerward facing intake is that the plumbing to fit a conical filter on each housing will get complicated. Where do you plan on drawing air from?

If you need some intake hose, little turbo parts, etc., let me know. I have a garage full.

[beepbeep]

Originally posted by TerryBPP
I also like how Amac merged the 2 downpipes together to use only one wastegate.

There is a slight downside to this as adding a X-pipe (which this merged wastegate pipe really is) will also lower the amplitude of exhaust gas pulses. With other words, pulses from left side will cross-talk to right side trough merged wastegate pipe annd vice versa.

As turbocharger is partly driven by pulses (as well as flow) you might expirience worse spool-up characteristics by X-ing headers in a TT-system. It does decrease the noise though.

[sand_man]

I know you don't care for the sound of Zorks, but maybe run with them for now, just to keep moving forward. It is a very simple solution...and light weight. Or are you afraid if you don't allow for the dimensions of a muffler, now, that you'll be screwed if you attempt to fit one later?

[TerryBPP]

Originally posted by beepbeep
There is a slight downside to this as adding a X-pipe (which this merged wastegate pipe really is) will also lower the amplitude of exhaust gas pulses. With other words, pulses from left side will cross-talk to right side trough merged wastegate pipe annd vice versa.

As turbocharger is partly driven by pulses (as well as flow) you might expirience worse spool-up characteristics by X-ing headers in a TT-system. It does decrease the noise though.

Excellent point. Tieing them well after the 90 should help help the cross pulse.

[RarlyL8]

Couple of issues/considerations:

- I must allow for the possibility of mufflers. I'm cranky and I don't like noise.
- The K16s have internal wastegates so the X-pipe isn't an issue.
- I don't know what the stock boost level is for the K16s but they look adjustable.
- Fresh air will come from the top of the engine.
- I will be needing bits and pieces (thanks Terry!). Right now I am missing one (1) heater hose. I found one of my old orange ones, can't find the other. I will be in Tampa next month, maybe we can meet.

What headers/heat exchangers would work best for the rear mount application?