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Hybrid Turbo thingies


GavinL
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Hi...

 

I am advised that stock MKIV turbos can be re-worked with oversize compessor

wheel and therefore more boost (I suspect a few other things need to be

done)....does anyone know about this e.g boost levels, is it both Turbos,

costs etc.

 

thanks

 

Gavin MKIV UK TT6

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The stock turbos can be hybridised to a specific level. You cant go totally mad with it otherwise the turbo casing gets too weak and cracks. The turbos will also have 360degree bearings put in as well as an enlarged wastegate.

 

All of these changes add up to higher boost but also increases the efficiency range of the turbos. However, it will increase lag due to larger internals. Combined with a FMIC it will make lag quite noticeable.

 

I know a few people who are running hybrids and they are all happy with them. Leon normally has a set sitting there waiting to be fitted and does them on an exchange basis. Costs about £800 per turbo I think, and then you have to get them fitted.

 

When my jap spec turbos blow then I will get a set of hybrids dropped in.

 

JB

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The stock turbos have a tough time when boost is consistently turned up above 1 bar. What happens is the casing of No1 turbo (the front one) cracks due to the sheer heat.

 

A hybrid turbo, having a larger compressor wheel, will generally give greater flow at a given boost pressure than the stock turbos. Which means you could have 2 cars, both running 10 psi boost, and the car with hybrid turbos will be faster. So hybrid turbos are great for  getting more power with lower boost.

 

Plus, 360 degree turbine bearings are a useful thing where people are running low back-pressure exhausts such as the Drager and the Hiper. None 360 degree bearings rely on a little exhaust back-pressure to help stop oil being sucked into the exhaust pipe.

 

There was a case recently of a MKIV owner who went too radical hybrid-wise and the turbos had quite a short life. Still, it must have been fun while they lasted. :)

 

I reckon you could get an extra 10% flow fairly safely. But try and go beyond that and the laws of thermal dynamics will swiftly begin biting back.

 

Yours,

J

 

 

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If you fit a larger compressor wheel to the stock turbos you will increase turbo lag. Which means you will have a tendency to make *less* power lower down the rev-range. Plus, having an imbalance between the turbos will mean that each bank of three cylinders will see a different resistance to flow - which is not a setup I (for one) would recommend.

 

Thing is, it's obvious Toyota spent a *lot* of time and effort designing the stock turbos and fine-tuning the system. Which means there is not a lot you can do in order to make it better. As far as sequential systems go, it was all pretty much state of the art. Not only that, increase flow too much and you *very* quickly reach the flow-limits of the manifold and of the turbine housings. Not too mention all the nasty adverse thermal effects.

 

I spent 12 months researching all kinds of different turbo configurations, all to no avail. What I wanted was maximum power with minimal lag. And it's simply not possible with turbocharging. Big power requires big turbos, and big turbos give a *lot* of lag. To counter this I tried designing a whole new sequential manifold with uprated valving, etc. But it ended up being a case of just too many pipes in just too small a space.

 

So I decided to junk the whole lot and use a different method of forced induction and replace the whole turbo setup with an ordinary high-flow exhaust manifold.

 

Yours,

J

 

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Okay, an extra 50 bhp is a bit *too* reasonable if you are thinking of fitting Leon-spec hybrid turbos together with other mods such as a better flowing intake, exhaust, etc.

 

50hp is readily achievable by junking the cats; fitting a straight-through exhaust such as the HKS Hiper or Drager; fitting the HKS FMIC; fitting the HKS mushroom filter as per our cool-air filter mod; fitting electric fans; changing the Jap cams for HKS 256 intake and 256 exhaust. Plus, you will need a boost controller and some kind of fuel cut defencer. And I would very strongly advise you to uprate your current oil-cooler setup by the addition of an oil-to-air radiator with a temperature sensing bypass; and to add Redline Water Wetter to your coolant.  

 

Running 15psi of boost, with this setup, will give you a *significant* extra push in the back and yet keep the motor running within sensible thermal limits.

 

Some members may argue there is no need to fit stuff like the FMIC, etc. that all you need is a boost controller and away you go. As an engineer, of many years standing, I feel these people are not considering that the whole issue surrounding engine tuning is that of improving efficiency... thereby opening up potential for gains in power. Of course, increasing boost pressure increases power. But without requisite efficiency improvements, this path to power is fraught with increased thermal risk.

 

Yours,

J

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Then, apart from a few other bits and bobs, details of which I gave in my previous post, the main thing you need are the hybrid turbos. They'll give you about an extra 10% flow which ideally should be matched to a more efficient intake. There are also fuelling questions to be addressed, but Leon will no-doubt have the answers as he has fitted a number of these kits and people have been v.happy with them.  

 

Beware, though, there are hybrid turbos being offered by a number of companies and it's all very tempting to go to the place that advertises the big power gains. I do know of one set of these big-power hybrids that had a very short life. Yes, this car did make big power... for about 2000 miles only.    

 

Yours,

J

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Leon's hybrids also come with some level of warranty which is nice to know. They are running on quite a few cars now and they seem to be pretty good. The main advantage for imports is the enlarged waste gate as the stock wastegate on import turbos just isnt big enough to flow properly. The UK spec cars are slightly different as I believe they have a turbo bypass pipe which is why removing the cats on a UK spec doesnt give them same boost as it does on an import.

 

Send Leon a mail about hybrids and see what he comes back with. Leon has always gone for optimum power across the range, theres no point in lagging all the way to 4500rpm and then it goes crazy, so he does everything he can to make sure there is power across the range. That gets a bit tricky with the HKS twins as they arent sequential but it is possible to keep lag to a minimum.

 

JB

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I'm pleased to note at least someone else agrees about the going crazy at 4500rpm aspect. You get next to nothing and then, suddenly, all hell breaks loose. Fine for scaring your friends, I guess. But I too could *never* see the attraction. Not only that, it must place a terrific strain on the engine internals and transmission apart from being a total pig to drive.

 

Yours,

J    

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it becomes a question of at what point you change to twins or a big single. As you know the manifold is the limiting factor in the sequential setup, and to be honest I think if you managed to get the manifold sorted then the slam at 4000rpm as the second turbo came on line would be huge. I can break traction when the second comes on line as it is and Im not even running hybrids.

 

I think Leon has done everything he can to keep it driveable, he nips down the shops in it some times so he doesnt want to be redlining it to get it to move. Theres still lag, but with the twins thats unavoidable.

 

I want a car that is as quick as possible off the line, so I dont see me ever changing from the sequential system. Hybrids will be the next step once I blow the stock turbos, and at 1.45kg that day cant be that far away.

 

JB

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JB

 

when you say "i can break traction when 2nd turbo comes on line", what gear are you in ?    (I assume it's in the dry).

 

and are you really running 1.45kg boost all the time ??   isn't aht about 20 or 21psi ?    methinks that you're *trying* to blow up the stock turbos so you can get hybrids...       I bet your stock turbos will stubbornly hang on in there for ages !!

 

cheers

 

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It would be first or second on the autobox, normally when pulling away from traffic lights the power comes in strong, and then when the 2nd turbo comes on line the rear will squirm about even in the dry. I used to actually have the TC come on with the old Bridgestone GridII tyres, but the s-02s are much better and it just spins a bit. In the wet I just stay off the 2nd turbo as much as I can, theres just no point as it really wont grip as soon as the 2nd comes on line.

 

It gets up to 1.45 with my foot flat on the floor on 3rd. The boost is relative to the load on the engine so at lower speeds and lower gears its a more reasonable 1.2 or so.

 

I still maintain the stock import turbos are bloody strong, the failures we have seen have been few and far between and either attributed to seriously overboosting or just poor maintenance. That said, I bet mine will blow in the next month or so just to prove me wrong. Trax is going to be the biggest test, its normally quite hot at Trax and there are some long straights.

 

JB

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John, have you done a compression test of your engine recently? Not being funny or anything, please don't get me wrong, but I'd be very wary of running the boost levels you say with the stock turbos.

 

Justin was running boost levels similar to yours and the detonation damage to his valve heads and erosion of the exhaust seats was quite severe. Plus, the casing of his No1 turbo had a huge crack in the region of the wastegate. And I too was running similar boost, when I had the stock turbos, and my No.1 had a similar crack although not quite as severe as Justins. Not sure about my head as I haven't lifted it yet.  

 

Justin's oil temps must have been through the roof also, judging by the state of his big-end shells. All of which had to be replaced.

 

Yours,

J

 

 

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