toddk911

Is this the same as variable vane turbos??

HIGHBOOST

No it's not. This is what the turbo has that the Evo is equipped with. It is supposed to reduce turbo lag by essentialy keeping the exhaust pulses undisturbed while entering the turbine housing.

toddk911

Would be interesting to see one of these fitted to a 951

So the exhaust has dual passages to get to the turbine, basically doubling the flow right? so it spools twice as fast.

But without the headaches of the variable vane turbos.

NICE!!

toddk911

Found this:

DUAL-SCROLL TURBO

Another technology unique to this motor is the use of a dual-scroll turbocharger. Dual exhaust passages from the engine to the turbine move the exhaust gas to the turbo more efficiently. This in turn reduces the time needed for the turbo to spool up and cuts the lag time commonly associated with turbocharging at low rpm. Guard told PHR: “The engine feels more like a naturally aspirated engine since there is virtually no lag. Throttle response is immediate.” Max boost for the intercooler system is about 20 psi and the motor is in boost as low as 1,700 rpm with peak boost at around 2,500 rpm. This turbo is well tested in currently used in boosted Saabs.” According to Ed Groff, assistant chief engineer of the Ecotec turbo: “Direct injection technology works well with turbocharging and helps deliver a great balance of power and economy. The Ecotec 2.0 liter turbo produces the power expected of a V6, but in a smaller, more efficient package – and the driving response is simply terrific.” We asked Guard why GM chose a turbo over a supercharger and he had this to say: “This engine from day one was designed as a global engine. Turbos are well-received in Europe, but the same cannot be said for supercharging. The turbo also suffers less from parasitic losses typically of supercharging. Also, the dual scroll turbo coupled with SIDI results in virtually no turbo lag, so a supercharger was even less necessary.” Being able to effectively market the engine overseas means that the overall cost for the powertrain development can be spread over the international market.”

toddk911

Here:

87944turbo

Not the best illustration, but you get the picture.

fortysixandtwo

Sounds like a regular divided hot housing. From what I understand, they're made to work when the turbo is mounted to the header. If this is attached to the end of the crossunder pipe on our cars, we wouldn't see any difference in performance. Personally, I think fabricating a split crossunder may be a little labor/effort prohibitive considering the dual tube would occupy about 50% more space than the factory one. That aside, I'd be interested in the results this might net.

toddk911

Wow! So it is that simple of just having two exhaust chambers into the turbine??

I was seeing some write ups of getting full boost by 2,500rpm on most cars. And making a fair amount of boost by 1,800.

Mike1982

Well, if you ran to pipes to the turbo as well, you have to REALLY watch out for heat lost then. Plus, what a pain that would be to remove from the car doing oil pan gaskets, clutch, bearings, etc. If one did fab it up to headers or at least that side some how, you would need to route the air intake down to that level then back up to the intercooler. Getting full boost by 2,500 rpms but how small is that turbo and what boost level is it at? Like to see a chart on that turbo really to see how much air it moves at different PSI.

AL951

here is a better idea

why not instead of having two crossover pipes, keep the same one and at the intake ports of the turbine, have a butterfly or something simular to close on port antil a specified RPM or boost level. this would greatly icrease the flow to the one open antil it spools up.

what do you guys think?

Regards,
AL

Mike1982

Backpressure comes to mind??... Running two pips in one would have a much smaller pipe that runs to the turbo.

AL951

well I didn't say to run two pipes inside one, no I said to keep the original one we have or something simular and at the turbine inlet ports have a mechanisim to close one of the two ports antil the turbo spools up.

Regards,
AL

Porschefile

A twin scroll exhaust housing is only really effective when the header is specifically designed as a twin scroll header. What constitutes a twin scroll header? Basically you just split the exhaust pulses according to the firing order. Pretty much all 4 cylinders are 1-3-4-2. Basically, you'd keep runners 1&3 together, but separate from 2&4 (separate all the way through the collector and to the exhaust housing). It's fairly simplistic actually. Ultimately though, I highly doubt a twin scroll setup would have any noticeable or worthwhile effect on a 951 using the crossover setup. The length from the headers is considerably long, and I think at that point the difference would be nil if anything. With the turbo mounted directly to the header, that's a completely different story and it can actually have a substantial effect on spool. The only downside I can think of is, when using a twin scroll setup in conjunction with a much larger turbo, it might be necessary to run a compressor surge housing as you could start spooling a little too low in the rpm and run into surge issues. It's neat stuff to think about, and I always find it interesting how "little" things like tuning airflow pulses can have such a drastic effect on a motor's actions. With our cars you'd probably just be better off using exhaust wrap on the headers and crossover or having them swain coated or something. Running a "twin" small crossover setup would be too much of a hassle IMO, and ultimately probably wouldn't accomplish much.

toddk911

That's interesting as that would kind of blen a dual scroll and a variable vane desing into one. At least in theory.

AL951

yes, that is the idea. I saw once a 917 turbo engine with this set-up. in fact it was one of the early turbo engines in the 917/10 development. But it is a good idea. This would yeild very good responce and power. I think honda is doing something simular on there turbocharger SUV, and all the mazgazine that have tested, have agree that it has great throttle responce. Some say it is even better the Mazdas engine.

regards,
AL