OV9

GG. wrote: Wed May 22, 2019 10:08 am

NotoriousREV wrote: Tue May 21, 2019 8:15 pm

McSwede wrote: Tue May 21, 2019 7:56 pm

It isn't a single turbo. It's a twin impeller turbo with each impeller looking after 3 cylinders. Very quick spool up and lots of torque. Mine for example was running just over 400lb/ft as standard which is a fair amount.

That’s not how Twin-scroll turbos work. It’s a single impeller but with the exhaust gasses split in two and delivered separately to it at different angles, with the blades angled to make efficient use of the flow from each nozzle. One nozzle works best for response, the other for high boost. Overall you end up with a turbo with great response and great top end flow.

Ok - but presumably boost limited because of the overall size of the single turbo despite the fact that the exhaust gasses are delivered in two streams to minimise lag - i.e. less tuning potential? I would also imagine swapping to a bigger turbo would not be easy unless compatible with the twin scroll setup?

Sounds like a clever solution to minimise cost whilst not succumbing to the lag typical of a single turbo. I expect fiddling with the exhaust plumbing upstream from the turbo is cheaper than fitting two which was the main driver behind doing that.

And of course, back to my overall point, ditching Toyota tech in favour of using a BMW setup.

There's always a limit somewhere, obviously. With turbos it's a careful balance of having a turbo big enough to hit your target power vs response. Bigger turbos make more power but spool slower due to the higher inertia of the turbine wheels and lower gas velocity through the bigger housing. Twin turbo set ups were used to overcome this, either by using 2 equal-sized, but relatively small turbos for fast response and enough flow, or a small turbo for response and a larger turbo for top end boost.

The twin scrolls work by pushing half the gas flow at high velocity at the smaller diameter part of the impeller to get it to spin up quickly, and then using the other half of the gas flow to drive the larger diameter part of the impeller to drive the rotation speed and provide the ultimate boost. spacing out the exhaust pulses also makes them much more efficient in transferring the energy from the exhaust. You get the same characteristics without the expense of 2 turbo units or the complexity of control systems.

My 1993 Impreza WRX with a TD05 turbo made 300bhp (a TD05 is good for nearly 350bhp) from a 2.0 litre engine. The power delivery was nothing-nothing-BAM! IIRC, it didn't make positive boost until over 3k rpm, and full boost wasn't until 3750. My later 2001 WRX had a TD04 and made 280bhp but was a lot smoother (and less exciting) to drive but that turbo was at it's absolute limit. My Golf R makes 310bhp from a 2.0 litre engine and you barely know it's got a turbo, they're making boost just off idle, and that's not even a twin scroll design.

I haven't posted about it, given how uninspiring it was, but this jogged my memory about the Renault Kolon, sorry Koleos hire car I recently had in Portugal. EDIT: actually I think it was a Kaptur

I genuinely thought it was broken when I first prodded the throttle as seemingly nothing at all happened. After a while I realised it was just simply epic turbo lag - essentially pretty much no forward motion resulted unless you were above 3k revs. A good example of a woeful turbo application!

Anyway, when it comes down to brass tacks and on the basis that actions speak louder than words, the fact that all BMW performance cars, M2, M3, M4 use twin turbos and on the V8s (e.g. M5), twin turbos which are also twin scroll, it doesn't look like BMW themselves think a single twin scroll setup is an adequate replacement for twin turbos.

ETA: I think the above is actually only true now they've dropped the M3/M4 lump in the M2, prior to that the M2 looked to use the N55 rather than the S55 which I think is single, twin scroll.

GG. wrote: Wed May 22, 2019 11:31 am Anyway, when it comes down to brass tacks and on the basis that actions speak louder than words, the fact that all BMW performance cars, M2, M3, M4 use twin turbos and on the V8s (e.g. M5), twin turbos which are also twin scroll, it doesn't look like BMW themselves think a single twin scroll setup is an adequate replacement for twin turbos.

As explained, they're looking to hit a power target whilst not compromising power delivery and will choose a turbo/turbos that meets the requirement. There's nothing inherent to the twin scroll design that limits power other than size (i.e. exactly the same as a single scroll turbo), but a twin-scroll will have better response than a single scroll for a given size. BMW have chosen twin turbos in applications where they obviously felt that a single turbo would be lacking in response compared to what they wanted.

Saying "a single twin scroll setup is[n't] an adequate replacement for twin turbos" is pretty pointless as there's too many variables. The twin scroll unit in the new Supra makes the same power as the twin turbo set-up on the old 2JZ, with better response everywhere, so in that use case the twin scroll is an adequate replacement. Most drag racers using 2JZ or RB26 motors switch to large single turbos when hunting for serious power, because they have different requirements (ie they're happy to only be making boost at 6000rpm because they're getting 1500bhp for quarter of a mile).

Here's a comparison of a single scroll vs twin scroll turbo (same specs otherwise):



Interesting article that it came from: https://dsportmag.com/the-tech/twin-scr ... at-divide/

Yeh I read that but as you note it only compares twin scroll to non twin scroll in a single turbo setup, not twin scroll to non twin scroll twin turbo which is what I was talking about.

I understand what you're saying (and don't think we're necessarily disagreeing?) but the crux of it is that BMW opted to revise the N55 setup to become the S55 for the M3 and M4 (and subsequently dropped that in the M2) in order specifically to move from the twin scroll single turbo to twin turbo non twin scroll (as not possible to have two, twin scroll turbos as only 6 cylinders feeding them).

Whatever characteristics they were looking for, they clearly think that the twin turbo single scroll approach is preferable. Saying that the single turbo twin scroll setup produces the same power and better response than the 2JZ engine isn't saying all that much as its 25 year old tech - I'd expect it to be significantly ahead!

The equivalent 911 turbo produces over 40% more power than it did 25 years ago so I think the reaction that this is not as powerful in context as its forebear is warranted to be honest.

GG. wrote: Wed May 22, 2019 12:23 pm (and don't think we're necessarily disagreeing?)

I'm not really sure what it is you're arguing, if I'm honest.

That twin turbos seem to be preferred to single turbo set ups (even twin scroll) by BMW for performance applications, the Supra really should have had the superior engine from the M2/M3/M4 (but didn't because BMW product line up reasons) and that it is yet another area where the new car is a compromise as a result of the tie up with Bee Em.

GG. wrote: Wed May 22, 2019 12:40 pm That twin turbos seem to be preferred to single turbo set ups (even twin scroll) by BMW for performance applications, the Supra really should have had the superior engine from the M2/M3/M4 (but didn't because BMW product line up reasons) and that it is yet another area where the new car is a compromise as a result of the tie up with Bee Em.

OK:

1) There will be a point in the power vs response requirement where twin turbos become preferable to a single. A twin scroll turbo extends this point but still has limitations. You also need to cover the additional cost of a twin turbo set-up, which is arguably easier to do in a halo model.

2) I suspect we'll see a higher power Supra in the future.

NotoriousREV wrote: Wed May 22, 2019 12:48 pm

GG. wrote: Wed May 22, 2019 12:40 pm That twin turbos seem to be preferred to single turbo set ups (even twin scroll) by BMW for performance applications, the Supra really should have had the superior engine from the M2/M3/M4 (but didn't because BMW product line up reasons) and that it is yet another area where the new car is a compromise as a result of the tie up with Bee Em.

OK:

1) There will be a point in the power vs response requirement where twin turbos become preferable to a single. A twin scroll turbo extends this point but still has limitations. You also need to cover the additional cost of a twin turbo set-up, which is arguably easier to do in a halo model.

2) I suspect we'll see a higher power Supra in the future.

3) Autocar factored it 0-60 on their Vbox at 4.0 seconds....Thats probably sufficient power for their "entry" supra.

scotta wrote: Wed May 22, 2019 12:51 pm

NotoriousREV wrote: Wed May 22, 2019 12:48 pm

GG. wrote: Wed May 22, 2019 12:40 pm That twin turbos seem to be preferred to single turbo set ups (even twin scroll) by BMW for performance applications, the Supra really should have had the superior engine from the M2/M3/M4 (but didn't because BMW product line up reasons) and that it is yet another area where the new car is a compromise as a result of the tie up with Bee Em.

OK:

1) There will be a point in the power vs response requirement where twin turbos become preferable to a single. A twin scroll turbo extends this point but still has limitations. You also need to cover the additional cost of a twin turbo set-up, which is arguably easier to do in a halo model.

2) I suspect we'll see a higher power Supra in the future.

3) Autocar factored it 0-60 on their Vbox at 4.0 seconds....Thats probably sufficient power for their "entry" supra.

Given everything is now turbo and a Carrera S is 3 seconds dead to 60 I'm not sure it is in 2019. The whole point of a Jap coupe is that you should be getting Carrera performance for 2/3 the price, no?

NotoriousREV wrote: Wed May 22, 2019 12:48 pm 2) I suspect we'll see a higher power Supra in the future.

The Supra Dupra?

mik wrote: Wed May 22, 2019 1:02 pm

NotoriousREV wrote: Wed May 22, 2019 12:48 pm 2) I suspect we'll see a higher power Supra in the future.

The Supra Dupra?

Maybe they'll go with a US flavour... the Supra [Grand] National. Cough.

GG. wrote: Wed May 22, 2019 12:58 pm

scotta wrote: Wed May 22, 2019 12:51 pm

NotoriousREV wrote: Wed May 22, 2019 12:48 pm

OK:

1) There will be a point in the power vs response requirement where twin turbos become preferable to a single. A twin scroll turbo extends this point but still has limitations. You also need to cover the additional cost of a twin turbo set-up, which is arguably easier to do in a halo model.

2) I suspect we'll see a higher power Supra in the future.

3) Autocar factored it 0-60 on their Vbox at 4.0 seconds....Thats probably sufficient power for their "entry" supra.

Given everything is now turbo and a Carrera S is 3 seconds dead to 60 I'm not sure it is in 2019. The whole point of a Jap coupe is that you should be getting Carrera performance for 2/3 the price, no?

according to Evo the carrerra S does it in 3.7...So id say for 2/3rds of the price you are getting it!

scotta wrote: Wed May 22, 2019 1:20 pm

GG. wrote: Wed May 22, 2019 12:58 pm

scotta wrote: Wed May 22, 2019 12:51 pm

3) Autocar factored it 0-60 on their Vbox at 4.0 seconds....Thats probably sufficient power for their "entry" supra.

Given everything is now turbo and a Carrera S is 3 seconds dead to 60 I'm not sure it is in 2019. The whole point of a Jap coupe is that you should be getting Carrera performance for 2/3 the price, no?

according to Evo the carrerra S does it in 3.7...So id say for 2/3rds of the price you are getting it!

Yellow seatbelts.

Normal black seatbelts would be 3.7s.

Sneaky Germans with their peformance options. Clearly the Austrians who build the "Supra" (I've decided i'm putting it in quotation marks from now on) have yet to cotton on to the tricks used by their brethren over the border.

That's a Carrera 4S

Good spot - I'm guessing the 2 wheel drive model is not 0.7 seconds slower.

I guess its sports chrono with overboost that means it figures quicker than 3.7. Given sports chrono is only about a £1,500 option, I think you can still class that as a standard Carrera S.

aracist wrote:

mik wrote: Wed May 22, 2019 1:02 pm

NotoriousREV wrote: Wed May 22, 2019 12:48 pm 2) I suspect we'll see a higher power Supra in the future.

The Supra Dupra?

The Supracarifragiristicexpiaridocious?

Mate, that's racist.

GG. wrote: Wed May 22, 2019 1:33 pm Good spot - I'm guessing the 2 wheel drive model is not 0.7 seconds slower but in honesty haven't got a fucking clue.

EFA.

scotta wrote: Wed May 22, 2019 1:20 pm

GG. wrote: Wed May 22, 2019 12:58 pm

scotta wrote: Wed May 22, 2019 12:51 pm

3) Autocar factored it 0-60 on their Vbox at 4.0 seconds....Thats probably sufficient power for their "entry" supra.

Given everything is now turbo and a Carrera S is 3 seconds dead to 60 I'm not sure it is in 2019. The whole point of a Jap coupe is that you should be getting Carrera performance for 2/3 the price, no?

according to Evo the carrerra S does it in 3.7...So id say for 2/3rds of the price you are getting it!

I would however like to retract my 2/3rds price statement and change it to almost HALF. £98k base vs £52k base.