So, for those hyper sports cars, a multi turbo setup would be fun, but at the same time a pit pointless, because electrification of some parts in the drivetrain just does the same job but then better. A Peugeot 207 with a small engine is driven within it's small power band all the time and doesn't really care about a bit of lag. The fun thing about that, is that the use and development of turbo racing engines look more like small underpowered cars then hypercars, who have to go around roundabouts and do trackdays. Indeed, racing engines have to be efficient at a very narrow power band, anything else is a waste. These technologies have varied from pre turbo throttles, throttle jackers, fresh air systems, subaru's rocket system etc right up to modern day MGU-H which effectively makes the turbo into an electronic supercharger decoupling spool from rpm/mass flow. if you are at 6000rpm and you go from 5% throttle to 100%. What we do see a lot of is development of anti lag strategies and by that I mean how quickly boost is available under transient throttle conditions above your boost threshold. Therefore your turbo selection will be to maximise the rpm range that you will spend the most time in. Yes, you want a nice wide powerband, but it doesnt need to start that low. The engine isnt going to spend much of its life at 1,500 rpm. I hope my English is good enough so you understand my twisted mind.Īssuming this is relating to racing engines rather than commuters, boost threshold doesn't tend to be that big an issue. This twin turbo fed from 1 valve each cylinder will work fine with 2 equally big turbo's, but what about 2 different sized ones? Would the path of least resistance be taken dominantly, even when the paths split so early in the head, being so close to the actual explosions? It would think the first pulse in the exhaust, the actual leftover from the explosion, would not take the path of least resistance very much, yet the actual outlet stoke will by some extend. Since I'm a Peugeot man (sorry) underneath PSA UX and EW engine heads will also have that option, albeit the plumbing would be hard. Parallel to this I would like to ask what you think about twin turbo's fed from 1 valve each cylinder. The inlet air would also need to be diverted in a way the big turbo will not surge the small one somehow. It would be hard to select a pair that's are a perfect match for sure. A very big waste gate would be needed closed at 1.5, yet fully open at 2, and in turn also be fed into the big ones exhaust inlet. If the small one would be at 1.5 and the big one at 2 bar for example, otherwise the small one would surely reach breaking point rpm at 4000 engine rpm orso. I would think it should at least start to be waste gated at 0,5 bar lower than the big one. Not cheap, but possible.Īs with the nizpro in the picture, I would think the small one would need to be exhausted though the big one. It will probably break more than temptation island. A check to sadev for a 4 x 4, 1000 Nm gearbox would be advisable though. With this in mind, a 2 liter with 600 bhp's that doesn't have a turbo lag of 2 months, would not be very hard. The very big one would then react on this volume and start at say 3000 (up to 8000), whereas it would have only started spinning at 5000 without the small one. Sticking to a 2 liter inline 4 as a reference, a very small one could spin as early as 1 bar rpm and perhaps 1.5 at turning the engine into a 4 to 5 liter from than point on. I would think this would be an excellent idea. Probably because my idea is hard to get right and expensive, but even in racing it's rare (I think) I've seen small/big combo's, but almost never a big difference and mostly parallels. I've been thinking why one almost never see's very small turbo's next to very big ones sequential or compounded. I would like to bring an idea past you and see what you think. I hope this is allowed since there's not much F1 relevance:įor yours I'm walking around with the idea's what to do, should I ever win the lottery.
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