Just reading on the net and see that some people put a supercharger and a turbo on their engines, the turbo is used for low rev power and a supercharger for more power at higher revs. Is there much point in really doing it? I would of thought it would be expensive to do.
I also read that when modifying your engine to be twin turbocharged you can put one big turbo on the engine and the then the other would be a small turbo. I heard they do it to try and stop turbo lag as the small turbo would power for low revs and then the big turbo will take over at higher revs to try and beat turbo lag. Does it actually work.
Could someone who knows a lot about turbocharging/twincharging a engine actually explain to me why it does or why it doesn't work please, I dont really understand it as the website that it was posted on didn't actually say how it works or if it does actually work.
I am aware of a few different types of multi-charging.
The old Lancia Delta rally car had super and turbo chargers, as far as i gather the super charger was basically a way of upping the power whilst the huge turbo was still spooling up. I've also heard rumors of the old 205 T16 using Nitrous as an anti-lag early in the revs...how true this is I have no idea.
The twin turbo jap-mobiles I saw years ago in Max Power used to have a smaller turb and a larger turbo. Obviouslt they spooled at different rates, and the smaller one gave boost at lower rpm whilst the larger one gave more affect at higher revs.
Thats what they was sort of saying on the site I saw it on. It said the small turbo was for the lower revs and then the bigger turbo took over after it spooled up. What do they mean by spooled up, does it mean that whilst it was like booting up? I thought turbo's didn't kick it to about 3,000 revs but a supercharger is always kicked in.
Sam are you sure you don't have it mixed up? I've not read up on twincharging but the Turbo lag is the reason you would twincharge - so the supercharger gives you power at the low rev ranges and then the high boost turbo once its spooled up.
Speaking simply then you have got it right. Superchargers are always running so will produce boost pressure at low revs as it runs off the crank pulley. While a turbo needs exhaust gas to spool and to have enough exhaust gas needs higher revs = lag. Superchargers have the advantage of low revs though while a turbo charger doesn't. Supercharges don't work too well at higher revs while turbos do. So the advantages of twin charging is obvious as it offers the best of both worlds.
The same goes for 2 turbos as well, a smaller turbo to spool quickly and a larger turbo for higher up the revs. Also if a twin turbo is set up correctly you can have the power gains of a large turbo while keeping a (relatively) smooth power delivery. I have seen it in where a small turbo is used for low revs and the boost from this turbo is used on the exhaust side of a larger turbo. The time I saw this though was really for just showing off the turbos was still interesting to see.
There is alot of factors though that effect spool time. Taking it to an extreme take a turbo off a smart car it would be useless on a boat engine as it is soooo tiny. While visa versa a smart car would never produce enough gas flow to spool a boat turbo.
Edit: I don't know the 'scientific' definition of spool time but it is simply the time, or revs needed, for a turbo to spin enough to produce boost pressure.
I will have to look up on sites to see how it works. Thought I would come here first because I knew someone would give me a answer. I will look through google to see if there are any websites that give you more of an inside look into how it works and what the results can be.
a turbo's spool up time isn't fixed, it all depends on many factors, the main ones being exhaust flow, inlet and exhaust turbine geometry, housing size and shape, engine airflow demands, inlet manifold and tubing, air temperature etc etc.
if you have an engine that only gains revs slowly and is fairly large, say a 3lt in a high gear and you put a small turbo on it, say one that's normally fitted to a 1.4 vw, then if you give it full throttle from low revs the turbo will start producing boost way before 3000 rpm but will either over spin at high revs / exhaust flow or have to be artificially limited, either way it wont produce much boost. conversly you could put a turbo off a rs500 sierra on the vx polo and while it would have the potential for very high boost the "lag" would be terrible and i doubt you'd see any real boost before 4000 rpm. when the rs500 came out clarkson, who at the time still actually tried to do road tests rather than articles, commented that the larger turbo meant the lag was so bad that after giving it full throttle, you could pop into the pub whilst waiting for the turbo and talk to all the skyline owners who had the same turbo and were waiting for their boost to arrive.
turbos have always been a balancing act between high boost capability and response time though modern variable geometry units and modern management systems have improved things a lot. i ran a mitsi lancer 2000 turbo in the late '80s ( think 4 door starion ) and as standard it needed close to 3000 rpm for any boost but after i changed the turbo for a unit off colin blower racing, it would show positive boost from 2000 rpm and full bosst from 2500rpm, the ultimate capacity was lower but still above what i required and it made the car far faster in real life.
the idea with the lancia s4 was to fill the hole before turbo boost with the supercharger and then let the turbo take the load at high revs when the supercharger drive losses would be highest. CCC mag and dave vizard actually used NOS on their turbo metro in the early 80s to cover the lag, it was activated on full throttle and because it was a very small power increase figure, it could be triggered at lower revs than normal NOS systems without risking engine damage, when the turbo started producing boost, it cut out. a nice benefit of it was by burning NOS and the extra fuel required, the exhaust gas flow was increased substantially so the turbo picked up speed quicker anyway, infact the NOS used to only activate for 1/2 second at a time.
the thing about "lag" is that it has 2 forms, the actual physical property of the delay in producing boost and more power and the perceived quality of nothing happening when the throttle is opened, which is only heightened by the substantial increase in power that turbos can provide when on boost. NOS apart from actually producing a power increase virtualy instantly and reducing spool up time also has the effect of the driver feeling an increase in power when he pushes the pedal so the car feels faster.
dave vizard also used ignition retard as a rev limiter on a road legal mini turbo he built for his daughter, what this meant was when drag racing she could floor it in neutral and the engine would sit at the red line but be on full throttle and have all the cylinders firing so the exhaust gas flow was high and the engine was on boost, the moment she dropped the clutch the revs dropped and the ignition returned to its normal setting.
p.s. i'm aware that NOS is a brand name but its easier than spelling nitrous oxide every time
EDIT if you want an idea of how bad lag can be, dereck bell reckond that the early single turbo 935s were so slow responding to the throttle that you had to floor it as you turned into a corner to get power as you got past the apex, which was fine until you made a mistake or found a slower car there and didnt want that power, renault had a similar problem with their first f1 car.
You can just type n2o. Just as many keystrokes as "NOS," and more accurate.
Now, for my actual contribution to the thread. On old diesel engines, detroit diesel to be exact, they use both a supercharger and a turbocharger. (Sometimes no turbo at all). The reason for that is because the supercharger basically generates no boost pressure. It is just to increase the speed of the air. And then the turbo is there to pressurize the air. Because since diesel engines have longer stroke, and greater compression ratios, it wastes power to have the cylinder pulling air through the intake and down into the combustion chamber. So, the supercharger takes the job of putting the air into the cylinder, so that less force is lost on the intake stroke. And the turbocharger is there to pressurize the air so that even more air can be shoved into the cylinder. The miller cycle engine requires a supercharger for a simmilar reason as a large Detroit diesel, I think.
That is a lot of power out of a 1.4 So a 2ltr Z20LET engine that produces 200bhp. Put a aftermarket turbo on it and a supercharger and it should be near enough 300bhp wouldn't it?
Would need more than just a turbo: You would probbably have to sort the fuelling out, change the compression ratio, etc etc, if your turbo will be adding 100bhp, it's probbably more than advisable to get an intercooler as well, as all of these non intercooled turbos (on Audis and some Vauxhalls) only add about 35-50bhp, probbably even less.
I know you would have to do more to it. How much would it cost for a intercooler, supercharger, turbo and the other mods that would need to be carried out to get the most from the turbo and supercharger? About £3k-£4k?
I seen the Range Rover Sport Supercharged version actually accelerate properly yesterday, those things are quick for a 4x4 so a supercharger alone should add a lot of power, correct? A turbo is just there for higher revs?
There's probably a reason that it only makes 170HP. The block is probably not designed to reliably handle any more boost. They probably wanted to cut costs a little. Because, I think that they probably COULD make it have 340HP stock, but then it would probably at least quadruple the cost of the engine.
You could say that, but it's not quite that simple. The supercharger and the turbocharger both have different flow maps. So, at low pressure ratios the supercharger is more efficient. The high efficiency of the supercharger makes up for the low efficiency of the turbocharger while providing boost also. As the RPMs go up, the supercharger may be less efficient at compressing air. Then the turbocharger's higher efficiency makes up for the low efficiency of the supercharger at that given RPM. But, if you were to put a larger turbocharger on, then there could be a gap in efficiency between where the stock supercharger and stock turbocharger used to even each others efficiency out. And, the engine has to flow a certain amount of air through the exhaust. With an engine that is only 1.4L, the only way to get more air through it is to increase the volumetric efficiency, increase displacement, or make the air more dense. A more efficient intercooler would make the air more dense. It might make the turbocharger spool faster. It would not really make any more power though. Because when the engine is dynoed, it is probably loaded so that it builds boost before they do the dyno run. So a better intercooler would not actually increase the max HP. It would give you more power earlier since the boost would build ever so slightly sooner. It would probably only make a difference in a drag race though.
You forget that the 4.4l V8 in a Range Rover kicks out 320bhp on it's own, anyway.
Since I was woken up by some tosser setting fireworks off at 2.30am, I'm too tired/can't think to explain so you should wikipedia Turbo and Supercharging and read their appplications and advantages/disadvantages. Don't forget there is more than one type of each.
I spent a while trying to find this thread. It was interesting when I first saw it, but from flicking to the end the guy never hit his target of 800AWHP.
If you completely redesign the engine, which you need to if you want to get the most out of forced induction then the maximum power output is pretty much limitless, although anybody who builds an engine with maximum peak power as the only design criteria is a blithering idiot. Simply bolting on a turbocharger and a supercharger is likely to result in only a minor (if any) power increase over a well set up naturally aspirated engine and will result in all manner of other issues and complications.
Thats the supercharger my dad has fitted, looks like a turbo and in some ways acts like one too. I only know about the Honda engines, big power is available from them, he bolted that thing onto a standard engine, lasted about 8000 miles then it blew up, after that i think we swapped 5 engines in total after it just smashed the linears to smithereens, even had some guy that does F1 engines do an autopsy, before the supercharger it was 220bhp, after it was quoted 360 but more like 310-320 at best, so about an increased 100bhp, install with intercooler, labour etc etc was something like 4-6k . Eventually he decided to get the engine tricked out and that boosted it to 500bhp, which imo is money better spent than the supercharger 200bhp increase and its more reliable. Only bad thing now is it overheats and looses power so in the process of watercooling it. (wrote more than i thought) So yeah, you can fit a supercharger onto almost anything if you know the right people, just don't rush into things and get the money spent on the engine at first instead.
When it spits flames like the bottom pic, you know you done good :P
This seems like it would be rare. There are two basic types of superchargers, some provide more boost at higher rpms, others produce about the same amount of boost at any rpm. The near constant boost superchargers are also called blowers, and they're usually roots type superchargers (look up 671 or 871 superchargers or blowers).
Supercharged engines aren't as fuel effcient as turbocharged engines. Since fuel milage is important for race cars (fewer pit stop), they use turbo-charged engines. Heat and lag are the main disadvantages of a turbo charger. Most high end drag racing cars use superchargers.
The advantage of two smaller turbo chargers versus a single larger turbo charger is less lag. Using different sized turbo chargers is also relatively rare these days.
Weight is a factor for supercharging racecars as well. They take a bit of weight and it's all placed on the topside of the engine where it's the worst place to put weight.
A supercharger will always lose efficiency the higher the RPM when compared to a turbo. They have much more rotating mass that the engine has to overcome before it can increase power.
A turbo is small and light, making it ideal for small cars. Turbo lag is still a factor, but nothing like it used to be back in the 'old' days. Keep the revvs up and with a steady foot you can keep boost positive, making for a much quicker spool.
Turbo's are positive feed, meaning the more boost the faster, until maximum efficiency is reached, it will spool so even a couple pounds pressure will give you a lot less turbo lag. WOT (Wide Open Throttle) shifting helps keep the turbo spooled on shifts. My car cuts the spark but keeps the fuel going so when the fuel hits the exhaust manifold it explodes, spooling the turbo during shifts.
IMO for efficiencies a turbo is much more efficient over a supercharger.
Turbo's are finicky things though and must be set up properly for each engine. Turbo's typically operate up to 100,000- 130,000 RPM and require lubrication, usually run off the oil pump, some turbo's if your lucky enough also run the engine coolant through it to keep temperatures reasonable.
You can get kits for certain cars that let you operate two turbo's but like Jeff said they are rare, but I think there is a cost factor involved =) Heat also prevents turbo's from making unlimited amounts of power. Because the inlet air is passing right next to the exhaust it heats up and the turbo makes for a great heatsink. Air also warms up as flow increases. Intercoolers help but they can only do so much.
In theory turbo's are 'limitless' but engines can handle so much and for a factory engine you would be lucky to get past 300BHP with an aftermarket turbo before having to change out internal parts. A lucky few engines can go past 400BHP before the engine becomes a ticking timebomb.
With enough money you can get I4's to run over 1200HP with a big turbo setup, but compression rates are so high and stresses so strong that it's not practical to go much higher.
There's nothing else to do!