TWIN TURBO, OR BIG SINGLE TURBO---AND WHY?
Discussion
Twin turbos are restrictive for big power, that's why you won't see something like a 335i going much over 400bhp without a single turbo conversion - which would totally ruin the character of that particular car.
With the more "Banzai" character of the Jap beasts, it's all about out and out performance.
Twin turbos - small one for quick response, then the big boy for the big power. What do you do if you want more power? A bigger smaller turbo, and then a bigger big turbo?! It isn't plausible - you'd need about 16k RPM and you'd still have lag for the first 3000 revs!
Single big turbo is the way for big power, just have to put up with a little lag - but that's all part of the fun
With the more "Banzai" character of the Jap beasts, it's all about out and out performance.
Twin turbos - small one for quick response, then the big boy for the big power. What do you do if you want more power? A bigger smaller turbo, and then a bigger big turbo?! It isn't plausible - you'd need about 16k RPM and you'd still have lag for the first 3000 revs!
Single big turbo is the way for big power, just have to put up with a little lag - but that's all part of the fun
The 993/996/997 turbo has stuck with two blowers, the big Mercedes V12 saloons/coupes are twin-turbo;
maybe a massive single one is better for outright power, by being smaller and lighter overall than two individual ones, leaving room for other stuff, at the expense of turbo lag?
Maybe!
maybe a massive single one is better for outright power, by being smaller and lighter overall than two individual ones, leaving room for other stuff, at the expense of turbo lag?
Maybe!
Simple really, its easier to do, less fabrication, plus modern turbo's means your big turbo makes as much wind as two little ones did at lower rpm's.
This makes 0.5 bar of boost at 2k rpm, 1.0 bar by 3k rpm, rated at 560bhp if required. Currently runs 1.4 bar. Its so responsive its plainly daft & there is nothing thats makes it special, just off the shelf parts on a standard 1JZ engine.
The all in cost to do this was probably less than buying two new standard tubbies
This makes 0.5 bar of boost at 2k rpm, 1.0 bar by 3k rpm, rated at 560bhp if required. Currently runs 1.4 bar. Its so responsive its plainly daft & there is nothing thats makes it special, just off the shelf parts on a standard 1JZ engine.
The all in cost to do this was probably less than buying two new standard tubbies
Edited by cptsideways on Friday 3rd August 12:25
BMW 335i is sequential, as in, small and medium sized turbos.
I agree that huge turbo lag sucks for the street, because it means it's so much less likely on the road that you're going to get your best power on a regular basis and is much harder to drive and also much harder on components, when 600 or however much lbs-ft, suddenly arrives at once!
I am beginning to think that a nice 'true-twin' turbo is best for a high-performance street car.
Sequential best for all-rounders like the 335i and 535d.
I agree that huge turbo lag sucks for the street, because it means it's so much less likely on the road that you're going to get your best power on a regular basis and is much harder to drive and also much harder on components, when 600 or however much lbs-ft, suddenly arrives at once!
I am beginning to think that a nice 'true-twin' turbo is best for a high-performance street car.
Sequential best for all-rounders like the 335i and 535d.
Gazboy said:
True, some garages claim to give you a 500hp singled car for £3k, where the more respectable places tell you it's £8-12k.
Mine would have cost quite a bit less than 3K a GT35 turbo costs 7-800, manifold £150-500 (some good cheap ones about) downpipe £200, intercooler & pipework from £300 up, some oil & water feeds £100. It does'nt need to cost a bomb, its simple engineering at the end of the day. There are so many off the parts bits its just a bolt on job for many cars.
Beemer-5 said:
So would you have single or twin turbo, on your dream 750 bhp 2.8 litre Skyline?
for 750bhp I'd rather stick to twins, but much more than that and it's single time. The obvious downside is the lag which comes with big bhp setups. Some people actually like the fact they get no boost before 4500rpm for pootling around off boost, I'd say they're nuts personally.
The big single option isn't as hard and fast as single = lag, twins = response, especially with turbos on the market now giving much better spooling characteristics than the days when T88's and the like were de rigeur for big power.
The trouble in comparing a single and twins is that people tend to think of T78's and T88's and the like as a comparison for much newer twins, which simply isn't right as they're old turbo's and lagtastic. There's pleanty of single turbos available that are suitable for lower power these days, and I'd put money on there being suitable turbos to replace twins for say 500bhp which will spool faster if not the same as the twin alternative, it's just something that's not really been done to any extent.
The trick is in the selection of the turbo(s) and ensuring it's suited to the application, in so much as the spool characteristics and boost delivery should be suitable to the car's application.
There's also the fact that buying one turbo is cheaper, less to go wrong, free's up space, bit less heat and so on.
The only thing possibly not in it's favour is how suitable 6 exhaust pulses are in driving the turbo as opposed to three per (smaller) turbo, but there's definately results in favour of both.
The Mitsubishi GTO TT may be different to other cars in that it has one (smallish) turbo for each bank of three cylinders. Lag is negligible, torque is huge and flat from 3000 rpm.
Changing to bigger turbos for even more power is not a huge problem but is likely to need higher rated injectors and fuel pump to match.
Changing to bigger turbos for even more power is not a huge problem but is likely to need higher rated injectors and fuel pump to match.
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