New Developments in Supra Turbo applications?

[Kirk]

The design and packaging of the sequential setup is pretty clever and elegant. With the BMW system to work from I still think a decent fabber could knock something up pretty quickly. There are only two actuators plus the wastegate one, and only one of those is on the hot side. There is some trick casting for the exhaust system but that's mainly for packaging reasons, we'd have twice the length of space to play with on the 2JZ hot side.

 

The N54 engine uses somewhat similar mounting design to the Supra, although the turbos are not at all linked like they are on the 2JZ

 

 

This type of design could and should work.

[mellonman]

High EGTs is why variable geometry turbos haven’t caught on in a big way yet in gasoline engined cars. Of course it all depends on how durable you want it to be.

 

I believe that Porsche and Maserati are the only OEMs using VGTs on gasoline production engines, compared to turbo diesels where they are virtually standard fitment.

 

i was told that mazda also use them on the mps cars

[Digsy]

The N54 engine uses somewhat similar mounting design to the Supra, although the turbos are not at all linked like they are on the 2JZ

 

http://2.bp.blogspot.com/_KkwAilVjAWI/STNxkTAvAZI/AAAAAAAAAD8/VA9y49ISP5g/s400/n54engine11.jpg

 

This type of design could and should work.

 

There’s nothing trick about that though, it’s just a boggo parallel twin setup (unless there’s a proper sequential version around). The bulk of the low down torque will be down to the twin variable cam timing and direct injection.

 

The BMW “Twin power” engines all use some form of pulse division in the exhaust manifolds. The I4s use twin scroll turbos, the V8 pictured earlier in the thread used two twin scroll turbos with crossover manifolds but the I6 can get away with two single scroll turbos because of the natural pulse division you get by dividing an I6 into two I3s.

 

If you want to see proper advances in turbocharging, BMW’s diesels are where you need to look. Twin charging using either a low pressure and high pressure turbo or a clutched supercharger and a turbocharger will probably be the next big thing in gasoline engines. Its already happening on diesels.

[Scott]

"If you think about revving an engine, the higher up the rev range you go... the quicker the revs increase."

 

 

Hmmmm.....

 

Until valving etc comes into play, that's when the power starts to tail off though.

 

Do you not agree that a car accelerates faster as the BHP increases... even when the torque remains the same? I thought that would have been gospel, otherwise why keep a car in the "power band" when driving?

[j_jza80]

I was just thinking about this on the drive home, what an exciting life I lead...

 

Torque vs RPM shouldn't make any difference to traction in my mind. It shouldn't matter if there is 500lbs rotating the rear wheel at 1500 rpm or 4500rpm... if the tyres aren't up to holding back 500lbs of accelerating torque then it won't matter at which point in the rev range this occurs.

 

On the move it makes quite a bit of difference. Depending what gear you're in, that 1500rpm could be 20mph or 60mph, so downforce and weight transfer can play a huge part.

[Kirk]

There’s nothing trick about that though, it’s just a boggo parallel twin setup (unless there’s a proper sequential version around). The bulk of the low down torque will be down to the twin variable cam timing and direct injection.

 

That I have no doubt of, I'm just trying to show that 2 VGT t28 could fit in a similar manor to the stock setup. That picture was the closest thing I could find to show the size of twin t28s .

 

i was told that mazda also use them on the mps cars

 

An MPS 3 doesn't use such a turbo.

Edited September 18, 2013 by Kirk (see edit history)

[Scott]

On the move it makes quite a bit of difference. Depending what gear you're in, that 1500rpm could be 20mph or 60mph, so downforce and weight transfer can play a huge part.

 

Near enough standstill for me, makes no odds..... I don't get any wheelspin. The only time I can break traction is launching hard off the line, in the dry of course.

 

All my diesels are the same, even my FWD Mondeo holds the road well unless being really silly or launching hard. That's down to half decent tyres though as it was a lot different when I got the car and it had ditch-finders on it.

 

Down force would make a bit of difference but so would the load on the engine, to get the engine to output 500lbs you would effectively need to be going uphill when in lower gears. I doubt very much, diesels especially, would load up enough to hit their top LBS in lower gears.

[Scott]

Your 535d make 500lbf.ft at 1500rpm? Sweet

 

Not quite the magic 500lbs, but it's definitely over 400

[Ian C]

The N54 engine uses somewhat similar mounting design to the Supra, although the turbos are not at all linked like they are on the 2JZ

 

http://2.bp.blogspot.com/_KkwAilVjAWI/STNxkTAvAZI/AAAAAAAAAD8/VA9y49ISP5g/s400/n54engine11.jpg

 

This type of design could and should work.

 

It worked back in the early 1990's on Skylines and Soarers

[Digsy]

Do you not agree that a car accelerates faster as the BHP increases... even when the torque remains the same? I thought that would have been gospel, otherwise why keep a car in the "power band" when driving?

 

That can't possibly be true. If torque remained constant then acceleration would at best remain constant IF you were driving the car on a perfectly smooth road with frictionless wheel bearings and tyres, in a vacuum. What actually happens is that frictional and aerodynamic resistance increase with speed, so the acceleration drops off.

 

What is usually called the "power band" is actually the peak in the torque curve, but modern torque curves are nearly flat anyway so there isn't really a "band" on production cars anymore. What might be muddying the waters is people with big single turbos where their torque curves look like power curves, and you get a much more gradual rise in torque than you would on a production car.

[Digsy]

That I have no doubt of, I'm just trying to show that 2 VGT t28 could fit in a similar manor to the stock setup. That picture was the closest thing I could find to show the size of twin t28s .

 

Ah. Does the new 135i I6 use a different setup, then?

[Kirk]

I don't think so, there isn't anything special about those turbos and from a bit of reading but they are roughly the same size of a t28 VGT, granted the exhaust housing are much smaller, thus I think it's quite possible to fit twin t28 VGT's in the same manor on a 2JZ which was the topic of convo on page 3.

[Chris Wilson]

With Digsy speaking so knowledgeably on cylinder phasing it reminds me of when V8's went from normal to flat plane crankshafts to allow neater and lighter exhaust header packaging. With a normal crank a V8 needs crossover primaries to get proper scavenging, and that was very awkward on rear engined race cars. Road cars usually used a balance pipe under the higher part of the sump pan to get some token effect. A straight six is ideal for simple and elegant exhaust primary plumbing, on N/A and pressure charged engines.

 

A V8 with a flat plane crank has some balance issues though and they are bit of a shaker, plus they don't sound as "nice" as a normal cranked V8. Does anyone recall Audi claiming the flat plane cranks they illegally used in one of the sports GT race cars was the result of an accident in heat treatment? Nearly as good as Toyotas trick valve on the GT4's..... They're all at it

[thetrashcanman]

A stone weighed down with an anchor.

 

Pretty much!

 

If I had the choice again and I was staying here I would get one in a heartbeat. Bugger the looks its a proper drivers car. A few remaps being released now too with 370bhp and over 410lbft.

 

I reckon it would teach all the hot hatches and most sports cars a thing or two. Check these out:

 

 

Yeah I saw the remaps, not quite enough power for my taste, but still would be an awesome little car, I'd be a little worried still about how much it would depreciate even if I only owned it for a year

[Digsy]

Does anyone recall Audi claiming the flat plane cranks they illegally used in one of the sports GT race cars was the result of an accident in heat treatment?

 

They really did that???

[Chris Wilson]

Ryan (mapper, globe trotter, playboy and entrepreneur ), had two Porsche VV turbos on a Lexus V8, the problem was even with the vanes fully open they were making far too much boost, far too soon. The lack of housing variations is one reason they are only applicable to a limited range of similar engine capacities and flow as the original engine they were designed for. The lack of VV turbo progress for gasoline fuelled engines shows that development is still fraught with issues and is very costly. Whether the F1 engines in turbo form will be allowed much turbo development leeway remains to be seen. I am not an F1 fan and I don't follow it closely, so I am not sure if they will even be allowed variable vane turbos in the first place? There's been skant engine development in F1 for a long time, due to current regulations, the Superbikes are pretty much the pinnacle of the science right now.

[Chris Wilson]

They really did that???

 

It was a bit like my wife blaming the oven when the cakes come out on fire, I guess.

[Chris Wilson]

Big torque Audi S8 anyone? A bargain given the mod price as a percentage of the cost of a new S8

 

http://www.pistonheads.com/news/default.asp?storyId=28484&utm_source=newsletter&utm_medium=email&utm_content=html&utm_campaign=2013-9-18

[Chris Wilson]

They really did that???

 

For the 1992 season, Audi had changed their engines to use a 180° flatplane crankshaft, which they said had been re-forged and bent from the original 90° crossplane part as used in production model. The DTM organisers found this highly modified crankshaft deviated from original homologated standard crankshaft, and therefore deemed it illegal. Audi subsequently withdrew from the championship

[Ian C]

Looking at the piccies of the BMW sequential setup, I reckon you could get a stock log manifold, and then put a more bespoke bit onto the two outputs that points exhaust gas upwards to the little turbo and downwards, via a butterfly valve, to the bigger turbo. Stick a wastegate bypass after the control valve but before the second turbo and you've got your boost control. The intake side is just a bit of tubing knocked up, and bam, you've got your prototype

[Chris Wilson]

Only glanced at the photos, but is that not COMPOUND turbocharging? I can't see how it could be sequential with differentially flowing turbos, one would back feed the other? Looks like the small one pressure feeds the intake side of the bigger one?

[Scott]

That can't possibly be true. If torque remained constant then acceleration would at best remain constant IF you were driving the car on a perfectly smooth road with frictionless wheel bearings and tyres, in a vacuum. What actually happens is that frictional and aerodynamic resistance increase with speed, so the acceleration drops off.

 

I'm solely talking about the engine though, I was just using the power band as an example. I guess the "power band" is more down to the gearing, and keeping it at the upper (easier to pull) area of the gears. In gear the acceleration will increase when the torque stays the same though, as the opposing friction force via the gearbox will decrease as speed increases.

 

Clearly a car in gear can't go any faster from 1000rpm to 6000rpm than it can in neutral. IMO the rate at which it can do so, 1000-6000, is down to BHP rather than torque (that's basically my point). Torque is the force, BHP is the rate at which it can be applied. IME an engine with 100bhp & 100lbs of torque increased to 120bhp and 100lbs of torque would rev faster in neutral.

 

I'm happy that I could very well be making all this up though

[Digsy]

Only glanced at the photos, but is that not COMPOUND turbocharging? I can't see how it could be sequential with differentially flowing turbos, one would back feed the other? Looks like the small one pressure feeds the intake side of the bigger one?

 

Yes, the BMW turbos aren't sequential in the 2JZ sense. They are compound. The small one spins up first, then both in series, then the small one is bypassed altogether.

BMW also do a tri-turbo setup where the smaller turbo(s) don't have to be bypassed at high RPM.

[Chris Wilson]

OK, so I am not going totally mad I have yet to see a sequential set up with disparate turbo flows. But I may be well behind the times! Thanks Digsy. we must have a beer together sometime.

[TBDevelopments]

From the research I've been doing when making my Supra turbo kits I was looking at the other turbos, sequential, compound etc and in the end for a 500-550bhp street car with similar torque figures it just turned out to be something very simple. Simple cast manifold ported, and a GTX35 of some description. From collecting users accounts I've found this turbocharger is on the limits of traction low down anyway, so more torque or "response" will just have you eating tires all the time, so a faster spool or faster torque production is just pointless.

 

They are also saying it'll hold boost to redline and give a very flat liner power band, making those figures around 1.5bar. Boost production from rolling is almost instantaneous when WOT is applied.

 

For a street car where anything above this on street tires just gives traction issues on anything other than a nice surface and bone dry why would you want anything more. I feel anymore and your just fighting the car all the time.

 

You could compound this setup but again this is just going to cause traction issues low down or when boost comes on, spinning tires is just a waste of money (sorry drifters) and its not moving forward. Plus compound turbocharging has a habit of getting the IAT very hot from what is basically double compression.

 

Just my opinion

 

Tim