Turbo V Supercharger?
Discussion
Alpineandy said:
maybe this has been mentioned (not read it all as must go out NOW!
Has anyone mentioned the problem of extreme heat in the engine bay (with a turbo), which isn't a problem with superchargers.
nope and for fibreglass bodied cars very relavant. I already have enough underhood heat without adding another radiator thankyou...
..and the Powerdyne/vortech/prochargers are significantly easier to package..
...plus I like my V8 exhaust note the way it is(I'm sure that adding a turbo would significantly change/muffle the exhaust note..)
BogBeast said:
...plus I like my V8 exhaust note the way it is(I'm sure that adding a turbo would significantly change/muffle the exhaust note..)
Erm....nope! Your exhaust note will probably become much harsher, and probably louder, as the gasses are now being forced in and out of the cylinders at much higher pressures.
Hi all,
joined into this a bit late, as usual, but when I was concidering between a turbo or supercharger I went for a supercharger as it seemed easier to get it to fit, exhausts are extreemly tight in the cobra engine bay, it would run cooler, as already stated, and I always think of turbos as the boy racer brigade. Where as a supercharger is more related to Mercedes, etc. Just my opinion thats all.
As for the exhaust noise, well Ive just got the blower running in mine and the noise from it is quite loud, does tend to drown out the exhausts a bit,
Phil
joined into this a bit late, as usual, but when I was concidering between a turbo or supercharger I went for a supercharger as it seemed easier to get it to fit, exhausts are extreemly tight in the cobra engine bay, it would run cooler, as already stated, and I always think of turbos as the boy racer brigade. Where as a supercharger is more related to Mercedes, etc. Just my opinion thats all.
As for the exhaust noise, well Ive just got the blower running in mine and the noise from it is quite loud, does tend to drown out the exhausts a bit,
Phil
Hi Ken,
Its a centrifugal Paxton SN-93 (upgraded to 11psi). I guess the noise is nice, but at tickover the belt is a bit noisy so sounds like theres something wrong, but there isn't. Once its going along it sounds great, going to take some getting used to. Im hoping that the belt noise will be drowned out by the blower when I up the pulley ratios. The rootes blowers are a lot quieter but not quite as efficient and are larger, but because I had very little room and needed it to be a efficient as possible (as Im running 9.75cr) I had to go for the centrifugal. Have a look at my site for more details,
Phil
www.replica-cobra.co.uk
>> Edited by daxtojeiro on Friday 5th March 09:05
Its a centrifugal Paxton SN-93 (upgraded to 11psi). I guess the noise is nice, but at tickover the belt is a bit noisy so sounds like theres something wrong, but there isn't. Once its going along it sounds great, going to take some getting used to. Im hoping that the belt noise will be drowned out by the blower when I up the pulley ratios. The rootes blowers are a lot quieter but not quite as efficient and are larger, but because I had very little room and needed it to be a efficient as possible (as Im running 9.75cr) I had to go for the centrifugal. Have a look at my site for more details,
Phil
www.replica-cobra.co.uk
>> Edited by daxtojeiro on Friday 5th March 09:05
Back to the original thread question, basically a supercharger is for use with low revving engines. This is why (I persume) luxury car manufacturers use them, as your average owner doesn't want to thrash a luxury car.
Turbocharging is meant for higher revving engines. For a given power output the engine should be smaller and lighter than an atno engine, as well. (Mind you with new materials, not sure whether an engine with a turbo is gonna be lighter anymore?)
But the main turbo advantage is the increase in volumetric efficiency (fuel mixture entered into cylinder) is around 100% or more, which means roughly a 10% fuel consumption saving over a similarly tuned atmo engine.
The Honda VTEC and new Ferrari atmo engines are also close to 100% volumetric efficiency (VE), which shows the advances in engine design. A 'good' efficiency 4 cylinder engine in the 70-80's period would hit around 75% VE and a yank V8 60-65%.
P.S. If anyone wonders, I still prefer a nice larger capacity engine.
P.P.S. BRM did a 1.5litre engine with twin superchargers in 1949 that knocked out 500-600bhp.If you want to see the car and hear it, go to www.gothmog.dircon.co.uk/Page2.html .
P.P.P.S Oh yeah, before anyone flames me, they can be used in other formats, i.e. turbos on a relatively low revving engine like a V8. And I do know the Formula 1 V8-V10's rev to 18000rpm. But then Honda had GrandPrix 4 cylinder engine that revved to 22000rpm, so they are still 'relatively' low revving.
>> Edited by Dinodelta on Wednesday 17th March 11:10
Turbocharging is meant for higher revving engines. For a given power output the engine should be smaller and lighter than an atno engine, as well. (Mind you with new materials, not sure whether an engine with a turbo is gonna be lighter anymore?)
But the main turbo advantage is the increase in volumetric efficiency (fuel mixture entered into cylinder) is around 100% or more, which means roughly a 10% fuel consumption saving over a similarly tuned atmo engine.
The Honda VTEC and new Ferrari atmo engines are also close to 100% volumetric efficiency (VE), which shows the advances in engine design. A 'good' efficiency 4 cylinder engine in the 70-80's period would hit around 75% VE and a yank V8 60-65%.
P.S. If anyone wonders, I still prefer a nice larger capacity engine.
P.P.S. BRM did a 1.5litre engine with twin superchargers in 1949 that knocked out 500-600bhp.If you want to see the car and hear it, go to www.gothmog.dircon.co.uk/Page2.html .
P.P.P.S Oh yeah, before anyone flames me, they can be used in other formats, i.e. turbos on a relatively low revving engine like a V8. And I do know the Formula 1 V8-V10's rev to 18000rpm. But then Honda had GrandPrix 4 cylinder engine that revved to 22000rpm, so they are still 'relatively' low revving.
>> Edited by Dinodelta on Wednesday 17th March 11:10
I've used turbo's on bigger capacity rovers. I was on boost at 1500 rpm and the noise from the exhausts and induction was wonderful. The turbo's also 'talk' to you when they start to get excited! As for the heat, all you do is shield them from pipework etc with an aluminium or card heat shield. I use rotomaster TO4B's.
Dinodelta said:
But the main turbo advantage is the increase in volumetric efficiency (fuel mixture entered into cylinder) is around 100% or more, which means roughly a 10% fuel consumption saving over a similarly tuned atmo engine.
Don't see why increased volumetric efficiency would lead to reduced fuel consumption. Turbo is likely to have better fuel economy that a similar power bigger capacity NA engine because the friction loses will be less, and worse economy that a similar capacity NA engine because the CR will be lower. But I don't see how volumetric efficiency has anything to do with it, unless you're talking about fuel efficiency under wide open throttle conditions (don't think economy under WOT is going to worry most people though).
Firstly the CR doesn't effect the turbo at all. In fact, lowering it may help lag as torque is increased because the mixture dosn't heat up as much if it isn't compressed as highly.This means a slower burn through the crank rotation.
When the turbo starts working then as you have more mixture entering the cylinder, the cylinder pressure at TDC will be the same or higher than the atmo engine.( I can show the mathes but I would have to go through my old physics text book and I don't particularly want to
)
That is the original point of a turbocharger, that for a given application a smaller engine can be used, or that a current engine could be used instead of fitting a larger engine.
For example the FIA used to use a multiplier of 1.4 to find out what the equivalent atmo capacity would be for a turbo at their given boost limit was (which I can't remember.It was on the first turbo F1 cars.)
So if you wanted 2.0litre performance with a smaller engine package at this boost, you would use a 1.4litre engine. (1.4litres x 1.4 = 1.96litres).The bottom end torque would be worse than a 2.0litre but the fuel consumption would probably be around a 1.6-1.7litre atmo engine.
And using the 1.4 multiplier ford 2litre 16V cosworth motor(210bhp),the cossie comes out at 2.8litres. Surprise, the Ford Cosworth V6 2.9litre 24V knocks out 220bhp.
If you use the multiplier as a rule of thumb. You must compare valve types together. Ie 2valve->2valve...4valve->4valve.
For example, with 2 valve engines:-
a Ford 2litre Pinto (105bhp), turbocharged (147bhp)
the cologne V6 2.8litre was around 140bhp( usually claimed higher)
P.S. Before anyone starts shouting massive power/fuel usage, this is with a turbo that is not overboosting.Ie around 1 bar. This is to get the Volumetric efficiency to 100%, anything higher is tuning your car for power.
>> Edited by Dinodelta on Thursday 18th March 21:55
When the turbo starts working then as you have more mixture entering the cylinder, the cylinder pressure at TDC will be the same or higher than the atmo engine.( I can show the mathes but I would have to go through my old physics text book and I don't particularly want to
) That is the original point of a turbocharger, that for a given application a smaller engine can be used, or that a current engine could be used instead of fitting a larger engine.
For example the FIA used to use a multiplier of 1.4 to find out what the equivalent atmo capacity would be for a turbo at their given boost limit was (which I can't remember.It was on the first turbo F1 cars.)
So if you wanted 2.0litre performance with a smaller engine package at this boost, you would use a 1.4litre engine. (1.4litres x 1.4 = 1.96litres).The bottom end torque would be worse than a 2.0litre but the fuel consumption would probably be around a 1.6-1.7litre atmo engine.
And using the 1.4 multiplier ford 2litre 16V cosworth motor(210bhp),the cossie comes out at 2.8litres. Surprise, the Ford Cosworth V6 2.9litre 24V knocks out 220bhp.
If you use the multiplier as a rule of thumb. You must compare valve types together. Ie 2valve->2valve...4valve->4valve.
For example, with 2 valve engines:-
a Ford 2litre Pinto (105bhp), turbocharged (147bhp)
the cologne V6 2.8litre was around 140bhp( usually claimed higher
) P.S. Before anyone starts shouting massive power/fuel usage, this is with a turbo that is not overboosting.Ie around 1 bar. This is to get the Volumetric efficiency to 100%, anything higher is tuning your car for power.
>> Edited by Dinodelta on Thursday 18th March 21:55
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