Why are Supra turbos sequential?

[rick001]

Was just wondering why the Twins are sequencial and not parrallel when lots of people swap them out for a single??

[Alex]

Was just wondering why the Twins are sequencial and not parrallel when lots of people swap them out for a single??

 

OMG. Please, have a good long think about the goals the MANUFACTURER had for the Supra.

 

I can see it now all the designers sitting around thinking why are we bothering with the sequentials when loads of people buying them in 20 years time will fit singles...

[Gazboy]

They wanted power on tap from tickover to redline.

[rick001]

That just does not answer the question,surely its a valid question if i am seeking an answer Toyota must have asked them selves (i did post in tech but got it moved) - i just want the abridged version

[bolarbag]

And try getting that response through 2Cats with even a small single

 

Dont forget most single conversions wont pass emissions

[Alex]

That just does not answer the question,surely its a valid question if i am seeking an answer Toyota must have asked them selves (i did post in tech but got it moved) - i just want the abridged version

 

As already said. They wanted more lowdown punch. The seq. system gave a wider operating powerband.

[RedM]

And try getting that response through 2Cats with even a small single

 

Dont forget most single conversions wont pass emissions

 

..or be as reliable.

 

[rick001]

They wanted power on tap from tickover to redline.

 

Thanks mate

[rick001]

As already said. They wanted more lowdown punch. The seq. system gave a wider operating powerband.

 

 

See aint that hard to give an unsarcastic answer is it

[Alex]

But, your question was silly hence the first reply. Why would Toyota care about people years later putting on Singles? These same people couldn't afford the Supra new (in most cases) so arn't in the demographic that Toyota targetted.

 

The Supra is a GT, Grand Tourer, designed to get you places in comfort, sans fuss. The people that wanted that kind of car are hardly going to want a T78 lightswitch that only produces power at 4500rpm!

[rick001]

My question simply was - Why sequencial and not parrallel, in essence!!

[bolarbag]

..or be as reliable.

 

True a single is never going to be as reliable as an oem car but I dont see why I cant give it a bash

 

The problem seems(rather seemed to be) dodgy garages doing all the work and handing out dodgy advice into the bargain

 

If an oem manufacturer was to build a car that required no emissions/noise regulations/fuel consumption then we would all be running about in 1000hp beasts, that would be pretty reliable even at that.

 

But they have to meet these stringent rules which requires something like a Veyron to meet, hence all the R&D and the pricetag to go along with it

[The Raven]

WOW harsh answers!

 

I think he was trying to ask why twins, why not just dump a single in ala MR2 and GT4.

[colsoop]

They decided what they wanted the Supra to do in terms of market - GT car.

A GT car must be comfortable and reliable with a certain amount of sportiness and be easy to drive fast or effortlessly cruise along.

They were trying to beat the 300zx at the time so dropping in something normally aspirated wouldn't cut the mustard or be too expensive to extract the power they would need to beat the Z.

 

The seq system is the perfect balance as it doesn't have a higher powerband before power is available unlike a single or parallel setup.

Although now (some 15-20 years later) there are a few turbo's that produce good power and will spool nearly as quick as the seq system.

[Gazboy]

Don't forget they were also targeting the c4 corvette too.

[carl0s]

My question simply was - Why sequencial and not parrallel, in essence!!

 

To allow for positive boost (and as a result power) lower down in the rev range. Prior to VNT/VGT turbos (variable vane/nozzle/geometry) as found in the new 911 turbo and BMW 335i, a parallel twin turbo setup would not reach useful levels of boost and power until much further up in the rev range than with the Supra's sequential setup. With the Supra's sequential setup, the exhaust energy only has to spool up a small lightweight turbocharger, so less inertia to overcome with more exhaust energy. Come 4,000rpm, there's loads of exhaust energy so the second turbo can be introduced to the exhaust gasses and then we effectively have a proper sized turbocharger working for us (two half-sized turbos working together in parallel).

 

I think it's important to note that with a sequential setup like the Supra's, once the second turbo comes online, the first turbo is still working, so it has become a parallel setup by 4,000 rpm.

[tomgeer]

To allow for positive boost (and as a result power) lower down in the rev range. Prior to VNT/VGT turbos (variable vane/nozzle/geometry) as found in the new 911 turbo and BMW 335i, a parallel twin turbo setup would not reach useful levels of boost and power until much further up in the rev range than with the Supra's sequential setup. With the Supra's sequential setup, the exhaust energy only has to spool up a small lightweight turbocharger, so less inertia to overcome with more exhaust energy. Come 4,000rpm, there's loads of exhaust energy so the second turbo can be introduced to the exhaust gasses and then we effectively have a proper sized turbocharger working for us (two half-sized turbos working together in parallel).

 

I think it's important to note that with a sequential setup like the Supra's, once the second turbo comes online, the first turbo is still working, so it has become a parallel setup by 4,000 rpm.

 

Are you a solicitor mate? Good explanation

[carl0s]

Are you a solicitor mate? Good explanation

 

er no, thanks, I think

[Gazboy]

Are you a solicitor mate? Good explanation

 

If he was a solicitor it would have been a 10,000 word essay with lots of clauses and excemptions and a*se covering with the answer to a question buried very deep within a lot of waffle.

[charlton]

With the Supra's sequential setup, the exhaust energy only has to spool up a small lightweight turbocharger, so less inertia to overcome with more exhaust energy. Come 4,000rpm, there's loads of exhaust energy so the second turbo can be introduced to the exhaust gasses and then we effectively have a proper sized turbocharger working for us (two half-sized turbos working together in parallel).

 

When people upgrade to big twins is there any benefit to this? Or if you upgrade to a large turbo and have a smaller turbo would this have the same effect as the OEM sequential twins?

[SimonB]

If he was a solicitor it would have been a 10,000 word essay with lots of clauses and excemptions and a*se covering with the answer to a question buried very deep within a lot of waffle.

 

Plus he'd have charged us 100 quid to write it. Or at least to get his secretary to write it after sitting on his arse for 4 weeks...

[carl0s]

When people upgrade to big twins is there any benefit to this? Or if you upgrade to a large turbo and have a smaller turbo would this have the same effect as the OEM sequential twins?

 

I'm non technical so not the best to answer, but big twins would be a straight parallel setup, no sequential, so it would have much less

 

One small and one big turbo doesn't work the same. With that sort of setup, you have the small turbo by itself at low load/rpm, and the big turbo by itself at high load/rpm. This is what BMW do with the 335d diesel motor I think. The BMW 335i (petrol) that I mentioned before uses identical VNT turbos in a plain old parallel setup, but because they are VNT turbos they can provide boost at very low rpm/load anyway.

 

Someone was working on a small/big twin turbo setup like this on the Supra, it was a home DIY project on Supraforums I think, and it was going OK last I looked, some problems with the switchover valve or something.

[carl0s]

Although Sound Performance are supposedly working on a sequential big twins setup..

I suppose this would have the same lag as a regular big-ish single, but potentially double the maximum power?

http://www.supraforums.com/forum/showthread.php?t=455869

 

Not really of interest to me I don't think.

[Wez]

Sequential 60-1 turbos would be interesting.

[carl0s]

Here's the small/big setup, where the car uses the small turbo and then switches over to the big one, using only one or the other but not both together.

 

WTFauto Sequential Turbo system initial results

More torque, more power, faster response, less complexity and (arguably) more reliability than stock? Yes to all of the above!

 

Mesmerize & WTF Auto’s sequential turbo system hit the dyno and this is what we got. We also dyno tested a relatively identically modified JZA80 with stock sequential turbos as comparison. To illustrate that this “stock” supra is running well, it did manage a 12.9 second pass at the strip.

 

Both cars had comparable exhaust, intake and intercooler mods. Both cars are automatic. Both cars are running identical stock ECUs, unmodified. The dyno used for testing was a Dynapak hub dyno which eliminates any losses from wheels and tyres to ensure an accurate comparison. Both cars were tested back to back on the same day in the same conditions.

 

To summarise:

The WTF Auto turbo system achieved the following key points

1. Faster low rev boost response than the factory sequential turbos

2. Higher boost levels off the first turbo than the factory sequential turbos

3. Totally seamless transition from first to second turbo / identical boost levels in both stages of turbo operation, unlike the ‘two stage’ factory sequential turbos

4. Higher torque and power figures at ALL rpm points from auto stall RPM to redline, despite running less boost and richer mixtures in the top end.

(the richer mixtures were due to Mesmerize running a much larger fuel pump arrangement which the stock pressure reg cannot keep up with. This is, if anything, hampering its performance against the stock car. The stock supra saw around 12:1 AFRs in the top end whereas Mesmerize was in the low 11:1s)

 

In other words, its performance is superior to the stock system in every conceivable way.

 

What should this particular set up be capable of? Unlike the stock turbos, it does not run both turbos in parallel as a second stage, it has a complete transition from one to the other. Therefore its limitation is that of the large turbo’s maximum flow. In this case, it is a GT3582R with a 1.06 A/R turbine housing. Garrett rates these things at 700hp. I estimate 550-600rwhp should be the realistic limit.

Small turbo is a 320hp rated 0.64 A/R GT2560.

 

The big advantage of this system is that the large and small turbos can be sized at what ever you desire. We are now building a more extreme combination including a 290hp GT2554 and an 850hp GT4294. This should produce boost far sooner than the system in Mesmerize, while enabling a much more powerful top end.

 

An added bonus is that larger than usual turbos should be possible. The small turbo helps the larger turbo to spool sooner than it usually would, and also goes a long way to preventing mid RPM surge from very large compressors.

 

Additionally, this is still a development system. Further improvements can and will be made to produce even better spool times and power.

 

Finally, the tapering boost curve was due to a faulty waste gate, not a design flaw in the system.

 

And now, the dyno graphs. Please excuse the poor print outs, the printer ran out of black ink . I have written in the relevant numbers.

 

Firstly, torque vs power. This one I like!

Dotted lines are the stock turbos, solid lines are the WTF Auto sequentials. Green is torque, Blue is power

Note the huge mid range torque increase, and earlier ramp up of the torque curve.

With the boost control / wastegate issue sorted, the torque curve should stay much more flat to redline... and of course, power stay significantly higher than stock all the way too. But slightly more power on 4psi less boost is a good initial result!

http://austweb.com.au/~wtfauto/images/forums/powervtorqueeditsmall.jpg

 

Secondly, boost vs power.

Of particular interest is how much sooner the boost begins to build compared to the stock turbos. Note also the flat boost curve, showing seamless operation.

http://austweb.com.au/~wtfauto/images/forums/powervpsieditsmall.jpg

 

Peak power was 336rwhp on 15psi for the stock system and 340rwhp on 11psi for the WTF Auto sequentials.

 

 

All questions welcome! And yes, I will be obtaining better print outs soon.

If you wish to ask questions or discuss anything outside of the forums, please email to [email protected]

 

The development of this turbo system was discussed in some length throughout this thread:

http://www.supraforums.com/forum/showthread.php?t=156380

from http://www.supraforums.com/forum/showthread.php?t=456989

 

Sorry for spamming the thread with all that