BorgWarner R2S Sequential Turbos

[kenny3737]

Hi Everyone,
I just noticed that BorgWarner is starting to produce the R2S Sequential Turbocharger. It is a small turbo mated to a larger VGT and is being offered to a number of industry auto makers. Do anyone have any idea if my MoTec can handle the engine management of such a new system and where I might find the specs for it online.
Thanks Ken

[930gt-40r]

Ken- Which Motec do you have? I am sure you have at least one extra output that can be used to produce a signal that could opperate the varible portion of the turbo.

[copbait73]

You could possibly control it but this system produces boost - 40 PSI on the Ford 6.4L PowerStroke Diesel.
This is not to be confused with the squential system that Porsche installed on their 959 24 years ago

[beepbeep]

If it's diesel turbo then it will be geared towards high boost, won't tolerate high EGT's and compressor size will be slightly mismatched to turbone size. But it will probably work....for a while.

[willtel]

That is an interesting system.

The new Ford Scorpion turbo looks pretty cool too. It uses a Garrett single sequential turbo, (SST) featuring two compressor wheels mounted on a single turbine shaft. The lower inlet feeds the first compressor wheel, while the upper inlet feeds the second.

[964 T #304]

Cummins did the same principle thing a few years back on gig 18 wheeler type NTC engines with one turbo in front of the other turbo, and if I rember turned a big cam 350 into a 475 hp engine with the set up

[totle]

Volvo is also going fort his technolegy for their diesel turbo's
2007 Volvo C30 Sequential Turbo Setup Photo
Volvo D5 twin-turbo diesel revealed for S80 - Photos

[copbait73]

Just a couple of comments:

Without controls these systems are more properly called series set-ups... one compressor feeding the next with the goal to supply high boost pressure. Not what gas applications want.

Historically, it's been a generally true statement that turbos installed on diesels have lower temp materials for the turbine housing and sometimes turbine wheel therefore not ideal of gas applications. This is not the case with the newest generation of diesels here in the states.

High EGR, and high power power density plus emissions tuning have moved the EGTs up. At the same time vane mechanisms require dimensional stability of the enclosing housings. All this means better materials. Not to the level of an all out race car but acceptable for homegrown experimenting.

Regarding the BW system, if you know what you are doing it's possible to separate the twin sequential turbo systems, duplicate 959 type valving and run them.

The newest Honeywell(Garrett) has the potential for eliminating some of the valving required of a true gas application sequential system. To accomplish this you will still need to read and drive the VNT plus control the inlet of one of the compressor stages.

To the best of my knowledge, none of this is impossible for people adept with Motec or Megasquirt. You should be aware that these are/will be expensive.

All this said most posters could open the door for major HP improvement with improved response IF they would adapt twin turbos. There are limits and compromises to what can be done with one turbo. Porsche knows the benefits of Sequential (959) vs Twin (993, 996, 997) systems and they have chosen Twin, it really is the next step-up.

[beepbeep]

Similar technology has been around in Europe for at least 4 years:



But still, diesel EGT's are much lower than gasoline equivalents. Also, turbine/compressor sizing is matched to this and doesn't fit gasoline applications well.

On the flip-side: diesel turbo bearings have always been very sturdy, as they boost much more than gasoline equivalents.

It shouldn't be too hard to make this work with Motec. Most of stuff is mechanically regulated.

[copbait73]

Goran:

You are right from your marketplace perspective, however I was speaking to the US market BW and Honeywell systems referenced above. They do not have the critical valving in the exhaust flow that stages 100% flow from the smaller to larger turbine, nor the check valves to isolate each or both.

Also since 03 US diesels have had high EGR % operation strategies and they are going higher. Not to mention you can not light and burn their soot traps without high EGT. I think you would agree that 1800degreeF is high.

Most diesel turbos in the 'States used 713C turbine wheels and Ni Resist turbine housings back in the late 80s. Unlike your market, the States have not yet to warmed up to small passenger car diesels and light duty vocational trucks that until recent times retained lower EGT typical of diesels.

The point still is why? Diesels need them for emissions reduction during accel then high boost. If you commit to packaging two turbos do yourself a favor and go twins. Nowdays they are properly sized, of acceptable materials and relatively cheap (W/G not VNT). One must remember 37 years ago when Porsche worked up the the 930 TURBO there were no options. The 3LD was a small turbo at that time and there was no market for W/Gs so they made their own.

[beepbeep]

copbai73:

I agree, but we still have the problem with low A/R's and mismatched compressors as diesel turbos are geared towards low EGT's while in normal operation (no purging of particle filter). They've probably increased EGT tolerance on turbine nowadays to take care of increased EGT's during purging, but they are still geared to work on "normal" EGT's.

Do you know what EGT's turbine expirience during "purges"? Wikipedia says that particulate matter burns at 600 deg. C.

The "typical" hi boost EGT in gasoline engines can be around 900 deg. C. Certain cars go as high as 950 deg. C.

Big diesel turbochargers have been used with success by people in drag-racing scene. They are very sturdy but tend to produce very peaky power, due to low A/R's.

When you say "go twins", do you mean two parallel turbochargers? I agree to certain extent, but I believe that parallel twins should be used when application allows to use fairly big twin turbochargers. While rotating mass per turbocharger is reduced with twins, aerodynamics are still there.

What I'm trying to say is following:

Single ball bearing GT35R might boost both sooner and hold boost later than two small TD04's. It will have more "living mass" (inertia) in the shaft, but economies of scale apply here. It's easier to produce good tolerances in big turbocharger than a small one.

Parallel to jet engines: One big Boeing 777 120klbs GE90 engine is usually more efficient than CFM56, even if you could use four of them. Spoolup would be somewhat quicker on CFM56, but GE90 will give more thrust per lbs of fuel.

Anyway, I applaud anyone who ventures out and tries to adopt sequential system on 911! We had 3DLZ and CIS for a very long time.

[copbait73]

I agree, but we still have the problem with low A/R's and mismatched compressors as diesel turbos are geared towards low EGT's while in normal operation (no purging of particle filter). They've probably increased EGT tolerance on turbine nowadays to take care of increased EGT's during purging, but they are still geared to work on "normal" EGT's.

Do you know what EGT's turbine expirience during "purges"? Wikipedia says that particulate matter burns at 600 deg. C.

Consider the EGT, to the first turbine (expansion-temp drop), second turbine (expansion-temp drop) tailpipe (expansion-temp drop). Must be high to start the process. No, the changes are in materials.
The "typical" hi boost EGT in gasoline engines can be around 900 deg. C. Certain cars go as high as 950 deg. C.

Except Autobahn, where can a street car stay on boost, therefore high EGT, to develop these temps and heat soak the housing? As installed on the 930 tubing header this is even less of a consideration. Diesels routinely run prolonged periods of high EGT because of load and high elevation. I’m not saying diesels are as hot, I’m saying that diesel engines are rapidly changing and conditions driving what you saw even 5 years ago does not apply in broad statement today.
Big diesel turbochargers have been used with success by people in drag-racing scene. They are very sturdy but tend to produce very peaky power, due to low A/R's.

This is match and not a fundamental difference.
When you say "go twins", do you mean two parallel turbochargers? I agree to certain extent, but I believe that parallel twins should be used when application allows to use fairly big twin turbochargers. While rotating mass per turbocharger is reduced with twins, aerodynamics are still there.

Parallel is more descriptive however twin is adequate. I have read your understanding of exhaust back pressure and it is spot on however in this statement you may be forgetting this most overlooked factor in power production. At the time you open the W/G what happens to effective turbine EFF of a single? It goes in the gutter and from there on EBP climbs at the detriment of HP production. PT turbos function through a wider RPM range before the W/G is needed.
What I'm trying to say is following:

Single ball bearing GT35R might boost both sooner and hold boost later than two small TD04's. It will have more "living mass" (inertia) in the shaft, but economies of scale apply here. It's easier to produce good tolerances in big turbocharger than a small one.

All match and marketing. The impact of BB is overstated. The point is a BB GT35 turbo is vastly superior turbo to a TD04 in stage and bearing system eff. A back to back comparison of GT35 bearing systems will show the BB superior but not to the level of your example.
The impact of tolerancing (running clearance) is only significant in the really tiny turbos, not the framesizes being considered.
Parallel to jet engines: One big Boeing 777 120klbs GE90 engine is usually more efficient than CFM56, even if you could use four of them. Spoolup would be somewhat quicker on CFM56, but GE90 will give more thrust per lbs of fuel.

Exactly, on a short runway I’d go for the four units regardless EFF. That aside we are talking compromises to a goal. Like the jet needing to get the most air behind it soonest, 2 turbos can feed the engine quicker than 1 or can provide the same air at low RPM but still give more at the top end.
Anyway, I applaud anyone who ventures out and tries to adopt sequential system on 911! We had 3DLZ and CIS for a very long time.

And so do I, that’s why I say buy them and give them a try.
There is nothing wrong because of their diesel roots.

There is fundamentally no difference in diesel or gas turbos. Behind the scenes, outside of marketing hype, ALL significant turbocharger advancements, especially aerodynamics, has been for diesel first then adapted sometime later for gas. The reason is simple, within the industry gas applications are considered less sensitive to efficiency, they are driven by cost. The entire GT line was developed for and applied to diesel OEs for years, it’s only recently configurations were established for single unit sales in the aftermarket.