I know of one or two other people who may have done this, but below you will find pictures of the manifold that I designed yesterday and just got back from having welded to fit my two new T25/28's independently to the front and rear rotors. I still need to clock the housings and the cartridges around to fit properly, but you can see how they'll fit. I haven't started work on the downpipes yet, but it's going to be quite the PITA (but worth it).

The primaries are 2.5", and the turbine outlets will be 2.5" into a 3" collector and back from there. I'd like to use 4" but I don't think I have the room. Runners are 304 SS, and I'm going to put a hi-temp ceramic on the manifold and the turbine housings as time and money permits. I also need to build a heat shield to fit in the tiny space between the rear turbine and the EGR path in the LIM.

I have contemplated putting together a GB on these manifolds, for anyone that has the time and patience and would like to use any of the following in pairs:

T25/25-28/28
GT25/28/28RS (would be tight)
T3/T3 Super 60/related
T3/T4's are too big to fit with this runner design.

If I were to start making these for turbos other than the T25/28, I would need someone to send me pairs of turbos to test-fab with, like T3's, T3 super 60's, etc. I am fairly sure that I can make it work with T3 flanges and still have clearance for the LIM.

Flanges and pipes would be 304 stainless, ceramic coated, with the innards ported. I've got about $350 in this piece after ceramic coating, so I may be able to get the cost around 300-325 on a GB.

If anyone is wondering, the turbos are technically Garrett TB25's, which are the stock turbo from the 2.4L (IIRC) 1994 Saab 9000S. They're roughly the size of a T28 with a slightly smaller turbine housing. You may have seen them on ebay; there's a guy selling them that managed to get his hands on several hundred.

 

That's sweet!

 

wow thats exactly what i want to do with my 7 rather then a single turbo.

 

wow, how much power are you looking to put down when everything is finished
?

 

You do realize that each turbo is now receiving half the exhaust pulses than in a single or factory twin setup, don't you?

-s-

 

That is typically what happens when you split the rotors from eachother... it wont have a detramental effect though, a single rotor will push enough air to spin them.

I really like it, I'm looking at going a similar route well down the road with some GT28's. Very nice.

~Kris

 

nvmd

 

you can adjust the housing

 

I realized that just as I hit submit.

 

Conservatively, around 350 WHP at 12-14 psi. This is based on math, not real-world testing, so who knows - I'll find out on the dyno. The compressors have the capacity (as a pair) to push about 480 HP worth of air, in my opinion, so I have some room to grow but still be practical.

Attached you'll find the top half of my theoretical (and linear) fuel injector duty cycle map generated by a tool I wrote, calculated for 14 psi with 4 850cc injectors.

 

I had thesame setup in mind because I' ve 2 T3 turbo's laying around from a Ford Escort RS turbo (1600cc, 160hp out of 1.6l)

They are T3's with 45mm cold side inlet. I'm not sure if they wil work good on my 13B. I'm looking for 350hp or something like that but having a custom setup would make it something different.

I"ll take pictures of them tomorrow, maybe you guys can point out what they exactly are or what I need to look for

Nice work on the twin setup, really like it....

 

Your standard Garrett T3-60 compressor flows about 23 lb/min of air at peak efficiency, so with two of them you've got at least enough airflow for 450 hp. The T3 turbine housings flow really well, too, and if you can get a nicely done Super 60, each turbo can support right at 300 hp. Gary at relentless makes some very nice T3 variants: http://www.relentlessracing.com Just don't tell him what you're using it for

 

ok, besides the manifold, turbos, ducting, lines and fuel...what has to be done to the engine itself for this to work?

 

Nothing any different then you'd do for upping the boost on your stock twins or running non-sequential or a single. I'm sticking with a stock motor for the time being and I'll be keeping the power down until I have time and money for a rebuild and a mild street port. I ditched the OMP in favor of premix, built a custom fuel system, and killed all the standard emissions stuff - planning on a PFC or a PEMS (haven't decided).

 

How do you think independent smaller twins will compare to Mazda's sequential system or a bigger single turbo in terms of boost response, low, mid and top end power and torque?

 

Naturally, I would expect more top end (bigger compressors) but less spool than a factory twin set-up, but more spool and less top end (but way more mid-range) then a large single set-up. Being that airflow should be up considerably in the mid-range area, since this is what these turbos are optimized for, the torque numbers ought to look pretty good. I'm not a fluid dynamicist and while my turbo knowledge is somewhat advanced, I've really got no idea save for some intelligent guesses and a few calculations until I put the car on the dyno and/or get that seat of the pants estimate.

I do know of one other group of people that did a twin T3 setup on an FD (I can't remember where, actually) and they reported considerable increases in drivability, response, and top-end power (as one would expect), and I'm not sure I agree with them here, but they went so far as to say it should have been that way from the factory. I am a big fan of the stock sequential set up, but I'm also a fan of the KISS principle so that's why I migrated in this direction myself.

 

i remember it in the classifieds but doesnt FEED make an aftermarket twin manifold as well?

 

I'm not sure. It took me two days and two trips to the machine shop to make my manifold, so I'm pretty happy with it. There's not much to it - the motor flange from mazdatrix, the two T25 flanges from I-don't-remember, and one 2.5" stainless mandrel elbow was enough.

 

From the pics it looks like you may have to readjust some things.I cant see how you can route piping.Have you thought of making the system work with your existing y pipe?

 

Nice work,it should look real good once you clock the turbos.

 

I'll get things clocked around sometime today or tomorrow. I don't see any way to do it with the existing Y pipe, no. I planned on just using some 2" mandrel bent aluminum with a collector into a 2.5" intercooler inlet, and probably a 2.5" or 3" into the elbow.

 

I would suggest welding in some stainless bars to connect the main flange and the turbo flanges, especially since you're just using T304 for the header. The purpose is to give additional physical support to holding up the turbos, otherwise you end up with welds on your tubing that crack over time. We used Inconel for the headers (much stronger than stainless) and still welded in two support bars for each turbo, given they are much larger turbos though.

Kevin T. Wyum

 

I had given some thought to doing that, and considering your suggestion, I will. Thanks, and thanks to everyone for your positive comments. I'll have some definitive results on the power as soon as time and money permit.

 

I knew Kevin would chime in sometime. I though about this many times but due to my lack of welding skills I opted out. Your getting me interested again though. So run me through it, you had a machine shop build the manifold? How did you do this? Did you cut pre-fabbed bends and then have them replicate it? Im just not understanding how you gave them the perfect measurements. It seems like being off an inch would eliminate your fitment. As far as the design of the manifold, is there no gain from collecting the exaust of both housings and then diverting it to both turbos? Im sure that would be a pain in the *** but do you think an x-over pipe would help?

 

wow that is awesome. Im really looking forward to this getting done! I was looking into getting a nice single, but if hits will make 450 hp and have more mid range, Im all for it! not to mention the "cool" factor hehe