Turbo V Supercharger?
Discussion
Supercharger every time. My XJR is a dream for power delivery - every experience of turbo'd engines has been very frustrating (I hate lag).
Personnally, if a supercharged option wasn't available, I'd go for a bigger engine rather than a turbo.
Isn't it the case that you really need a larger engine to mate with a supercharger as you lose a certain amount of BHP powering the pump? Provided the net gain is high, a supercharger makes sense.
Personnally, if a supercharged option wasn't available, I'd go for a bigger engine rather than a turbo.
Isn't it the case that you really need a larger engine to mate with a supercharger as you lose a certain amount of BHP powering the pump? Provided the net gain is high, a supercharger makes sense.
Bit of a half a dozen of one 6 of the other situation as the latest superchargers tend to be pretty efficent in power to drive (vortech etc) and the with the boost control now available turbos can be made more driveable than ever before.
There is no correct choice it really depends on the application.
Matt
There is no correct choice it really depends on the application.
Matt
IIRC, newer variable geometry turbos are better because the angle of attack of the veins on the turbine are ajusted depending on various parameters so that the turbo will spin up quickly from low revs / low gas speeds but will not overspeed and deliver high boost and high efficiency at higher revs / gas speeds.
Feel free to shoot me down if this is bollocks, but I'm sure I read is in VW's blurb somewhere on one of their TDI's...
Feel free to shoot me down if this is bollocks, but I'm sure I read is in VW's blurb somewhere on one of their TDI's...
I have almost no experience of superchargers (save for a test drive in an SLK230 a while back) but I do know my Impreza P1 suffers lag even though it's a modern turbo with all the blow-off valves etc attached. Still quicker than my Chimp 450.
I've heard that a device called the "Dawes Device" aids lag and spool up quite a bit. Have not tried one so can't comment, but have read the blurb (which I didn't understand). It is dirt cheap to buy, though.
I've heard that a device called the "Dawes Device" aids lag and spool up quite a bit. Have not tried one so can't comment, but have read the blurb (which I didn't understand). It is dirt cheap to buy, though.
Its probably an old talking point but being pro Turbo (given todays technologies and efficiencies with them), why go for superchargers?
Supercharger pros:
no turbo lag
positive displacement types give full boost down to low rpm
no messing about with oil and water lines, exhaust manifolds etc
cons:
requires belt drive so harder to package
most positive displacement types are less efficient so need more charge cooling at high boost
consumes a significant amount of power
low-rpm blow-through occurs unless a low-overlap cam is used, the blow-through loses power and cooks the exhaust/cat. Low overlap cams have less top-end performance and tend to have a more aggressive profile which means they don't last as long.
High boost at low rpm is relatively bad for engine wear.
Back pressure does not inherently reduce the boost (as with a turbo) so it is easier to grenade the engine if set up wrong.
That's leaving aside the issues of capital cost and installation hassle. So it should be an easy decision in favour of the turbo, but that effortless low-end torque from a supercharger makes it really attractive ...
Peter Humphries (and a green V8S)
It's turbos for me because they're thermally and mechanically more efficient then a charger. You won't get lag on a street biased engine of reasonable capacity and if your base compression is around 9:1 cr then you will be on boost by 1500-2000rpm anyway. So you have normally aspirated performance off idle and at high cruise it's economical, plus there's some 30% additional torque when you hit the pedal, maybe more. You could run 5-8 psi on that compression ratio without intercoolers in a street application. Whats more there are so many turbos on the market, new, re-con or second hand that removing them and changing them for another turbo is simple and needn't be expensive.
boosted ls1 said: It's turbos for me because they're thermally and mechanically more efficient then a charger. You won't get lag on a street biased engine of reasonable capacity and if your base compression is around 9:1 cr then you will be on boost by 1500-2000rpm anyway. So you have normally aspirated performance off idle and at high cruise it's economical, plus there's some 30% additional torque when you hit the pedal, maybe more. You could run 5-8 psi on that compression ratio without intercoolers in a street application. Whats more there are so many turbos on the market, new, re-con or second hand that removing them and changing them for another turbo is simple and needn't be expensive.
have you ever driven a car?
ive yet to drive a turbo car even with anti lag that didnt lag to some extent.also anti lag systems tend to keep the turbo so hot they ned replacing every 100 hours or so(depending on application)
as for superchargers when fitted and set up correctly they will give 10,000 hours or more of reliable lag free use.
that said on my day to day runabout i run 2 small turbo's in a feeble attempt to combat lag.the only reason for the turdboat is cost.simple to fit easy to plumb in and easy to replace.
atmo engines are the only way to go
The blow by problem mentioned with superchargers and overlap valve timing would surely affect turbos as well. (presumeably not to the same extent due to the back pressure generated by the exhaust turbine obstruction).
One Q: Is there much point running a supercharged turbo engine other than having no loag for low rpms? E.g if you ran both at say 7psi, would you only get 7 psi overall 'boost'. Would there be any benefits from reduced stresses on either component.
Currently l can only see doing both as an advantage if you have a whacking great turbo that doesn't spool until 4k rpm!
One Q: Is there much point running a supercharged turbo engine other than having no loag for low rpms? E.g if you ran both at say 7psi, would you only get 7 psi overall 'boost'. Would there be any benefits from reduced stresses on either component.
Currently l can only see doing both as an advantage if you have a whacking great turbo that doesn't spool until 4k rpm!
funkihamsta said: The blow by problem mentioned with superchargers and overlap valve timing would surely affect turbos as well. (presumeably not to the same extent due to the back pressure generated by the exhaust turbine obstruction).
One Q: Is there much point running a supercharged turbo engine other than having no loag for low rpms? E.g if you ran both at say 7psi, would you only get 7 psi overall 'boost'. Would there be any benefits from reduced stresses on either component.
Currently l can only see doing both as an advantage if you have a whacking great turbo that doesn't spool until 4k rpm!
I don't have any experience with turbos but I've been told that boost and backpressure work out similar, so the blow-through problem is negligeable. The silly cams I've been hearing about are for superchargers only.
Apparently S/C + turbo is a 'good' combination in that the S/C gives enough instant boost to spin the turbo up (overcoming the low rpm handicap that turbos have), and the turbo is more efficient so it can be run up to higher boost and higher rpm once it is up to speed. Also the turbo back pressure neatly solves the S/C blow-through problem, as you said. But in terms of cost/complexity/bang-per-buck I think you'd have a hard time justifying it.
Cheers,
Peter Humphries (and a green V8S)
ACCIDENT said " have you ever driven a car?
Now what kind of a daft question is that?
I assure you that a decent v8 running 9:1 c/r with a pair of rotomasters set at 7 psi has no lag, absolutly none at all. After all its running on stock compression. What's there to hold it back apart from traction issues? It's like having an engine on 11:1 but with 33% more torque. Nothing daft about this!
Now what kind of a daft question is that?
I assure you that a decent v8 running 9:1 c/r with a pair of rotomasters set at 7 psi has no lag, absolutly none at all. After all its running on stock compression. What's there to hold it back apart from traction issues? It's like having an engine on 11:1 but with 33% more torque. Nothing daft about this!
tuffer said: I seem to remeber that Lancia were working on the Delta S4 (group S rally car) that had both a turbo and supercharger, this avoided lag and gave boost from low rpm. Unfortunatly the project was canned when group B bit the dust.
Lancia did run the Delta S4 in several rallies. I can't recall the exact figures but they extracted 500 to 600bhp from a 1.8litre four cylinder. Even more telling was the fact that one works car went round a GP track fast enough to qualify for the Grand Prix!
The control mechanisms of the engine must have been quite complex but it has been done. Check this out: www.gtr.co.uk/forum/upload/showthread.php?s=7bcbf3d2ed7d01f24cde3dd050b45a55&threadid=6700 Some posts in that thread by a guy who'd actually built a roadgoing car with a super- and turbocharged engine.
MDG.
Interesting to read Gordon Murray's views in EVO this month who goes for normally aspirated then Supercharged and pretty much dismisses turbos as 'missing the point'!
As for Peter....
Again in EVO - mention of the 1300+bhp out of a 1.4 in the old F1 cars!
As for Peter....
....well, are you forgetting blowing up Dave's R5?
I don't have any experience with turbos
500 to 600 nags from 1.8!
Again in EVO - mention of the 1300+bhp out of a 1.4 in the old F1 cars!
Interestingly the new GTO-3 from Noble has a little switch to turn it off and on - very useful in the wet - the sudden rush of power spins the wheels on a damp surface in 1st, 2nd and 3rd!
However, I do love the "turbo" effect for driving - donno why - probably beacuse since 23 i've owned a turboed car
J
However, I do love the "turbo" effect for driving - donno why - probably beacuse since 23 i've owned a turboed car
J
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