Turbo V Supercharger?

[lotusguy]

mk1 said: Just as another talking point within this thread there is another type of forced induction which pound for bang is hard to match - Nitrous Oxide. Having tried both nitrous and Turbo i must say the Nitrous is quite fun if properly set up. IE correct CR correct air/fuel mix correct plugs etc etc. It has to be considered. But admittedly i found the draw back is the refilling of the bottle and change of plugs for "hard/soft" running. I believe the Luftwaffe used it on their fighters during the war! Or was that water methanol?

Hi,

I agree with you that Nitro can be fun, what I have a problem with is that is Nitro is not really a form of forced induction.

Nitrous Oxide, or N20 was initially used both as an anesthetic and for recreational purposes in the middle 1800's.

It's initial use in internal combustion engines was in aviation. This use was not to specfically increase power, but to increase range. That is, to allow aircraft to fly at higher altitudes. This allowed aircraft to take advantage of the fact that since air is less dense at higher altitudes , the aircraft suffers from considerably less drag, thereby reducing fuel use and consequently increasing range. The same is true of adding turbocharging to aircraft engines.

Nitro and turbocharging permitted an aircraft engine to receive enough oxygen to combust it's fuel mixture at altitudes where insufficient oxygen existed to do this (although sufficient air exists to produce 'Lift' under the wing, insufficient amounts existed for proper combustion at altitudes over say 25,000 ft.). But, each method accomplished this in different ways.

In turbocharging, greater volumes of air are forced into the cylinders. Since there is less oxygen per unit/volume in air at higher altitudes, more volume equated to more oxygen being delivered into the cylinders for combustion.

With Nitro, additional oxygen is supplied with the gas itself as N2O has 1 atom of oxygen for each molecule of gas as opposed to 0.4 in regular air which is only 20% oxygen by volume (20.947% actually).

The fact that more power was produced was almost secondary, I say this because in propeller driven aircraft, the propeller also loses efficiency at higher altitudes and so must spin faster to achieve the same speed (or put another way, to fly fast enough to produce the same amount of lift).

In automobiles, you really don't want to achieve greater altitudes, but Nitro and turbocharging can produce more power. Also, there is a phenomenon of very rapidly expanding a gas which causes the gas to shed it's heat, so injecting Nitro also allowed the air/fuel mixture to cool. This allows more fuel and higher compressions to be used bfore detonation becomes a concern. Happy Motoring Jim'85TE

[lotusguy]

JonGwynne said:

grahambell said:

lotusguy said:

JonGwynne said:

Why not? The XKR is a high-performance car.

He He...Ok, ok... I thought you were serious about this post 'til this last bit.

Grand Tourer, certainly! Luxo Cruiser, perhaps. $96K worth of Chic, no doubt. But, at nearly two tons and automatic transmission exclusively, 'High Performance'?? Can you say Streeeeeetch???

Perhaps all the steroids pumped into it's Coventry Squirrel-box have leaked into the cockpit. I'd love to match up my Esprit with it, 'course your concern over direct comparisons would say that it wasn't fair that my lowly carburetted 4 cylinder 2.2 Ltr. blew the doors off your 3.9 Ltr. V-8! ...Jim '85TE

Sorry Jim, but I have to point out that despite the auto box and weight the XKR coupe will - just - out-acclerate all but the later SE and S4S Turbo Esprits and has a higher (limited) top speed. Not as quick along the bendy bits though.

Thanks. I didn't want to say it. He wouldn't like to hear it from me. ;->

But just to get a word in, I could also point out that the Jag's performance is more accessible to the majority of the driving public due to the TC/ABS and (especially) the auto box. The latter does wonders for making acceleration benchmarks consistent and repeatable by nearly anyone with a foot.

We'll give Jim the benefit of the doubt that he is both familiar and adept with his car and drives it as well as just about anyone but my grandmother in an XKR could out run him.

Lotus introduced fuel-injection a good way back. So when Jim says he has a pre-FI car, its probably a Giugiaro model and those topped out at around 200bhp if memory serves. Certainly an astounding output from a 2.2 liter 4-pot back in the day. But it would barely pass muster in a hot-hatch now and certainly has no business going up against an engine that produces twice as much power and lower down too.

p.s. Don't get me wrong, I adore Esprits in general and the S4S in particular but I don't pretend they're something they aren't. Next he'll be telling us his car seats four.

>> Edited by JonGwynne on Thursday 23 January 16:37

Hi,

"Me thinks thou dost protest too much"... My Esprit has been accurately clocked 0-60 in 4.9 sec.(including turbo lag) and a top speed of 164mph vs 5.2 and 155mph for the XKR and that's the vaunted 'Silverstone' variant.

Granted, I have increased the compression ratio from 7.5:1 to 8.5:1, re-jetted the carburettors and added a mildy higher lift cam (4.12" vs 3.78" stock), raised the boost pressure from 6PSI to 10PSI, but these are minor mods (no porting or intercooler added) and I can easily run with the SE's, in fact, an SE owner I know has driven my car and said it is much faster than his SE. The later model Esprits suffer from a pretty good weight penalty. I have tracked my car with a variety of other Esprits and have no difficulty mixing with the latter models at all. An S4s and V-8 will always beat me, but for the rest, it's a real race. The only way my car will seat 4 is to strap 2 across the hood, and that's fine by me.

But, journalists have described the Jag XKR as 'barely a Sports Car'. It takes much more than just power to achieve this status such as chassis balance and braking and turning ability. The Jag suffers in each of these areas. I have driven the XKR on the track and find it woefully wanting in performance. The traction control and ABS take away a significant amount of driver control/input.

However, it is a great car - wonderful styling, excellent engineering, lush interior, but as has already been pointed out, let's not pretend that it is something it is not. It is a great Grand Tourer, period.

The Marketing Guys in Coventry will profer the performance abilities of the car, but that's not the same as pure statistics... And, just because the Jag is "more accessible to the public" doesn't make it a performance car either...sorry the Jag is no performance car...PERIOD! Jim '85TE

>> Edited by lotusguy on Thursday 23 January 17:46

PS - As this was brought up, I'll comment. Stock horsepower on carburetted Esprit is 218bhp@6,250rpm and 200 ft.lbs @4,400rpm of torque. My car has been dyno'd at 258bhp@6,200rpm and 238 ft.lbs. torque@3,900rpm. This yields a horsepower/weight ratio of 0.096:1

The Jag (Silverstone) boasts 370bph@6,150rpm and 387 ft.lbs. torque @3,600. it's horsepower/weight ratio is 0.088:1.

This makes you believe that the Jag is faster than the Esprit????? Happy Motoring! (or should I say Grand Touring) Jim '85TE

>> Edited by lotusguy on Thursday 23 January 18:23

[grahambell]

Sorry Jim,

Have to disagree with you about the XKR not being a performance car. 0-60 in 5.2 seconds and storming acceleration that continues way after that - I'd call that a performance car. Not a sports car - as you say, it's really a grand tourer - but definitely a high performance one.

And if you want to know which I'd rather have, an XKR or an Esprit, well it'd be an Esprit. Sport 350. Probably my favourite drive out of all the cars I've tested. Have to say I did enjoy the original XKR coupe though - especially the whine of the supercharger...

[lotusguy]

grahambell said: Sorry Jim,

Have to disagree with you about the XKR not being a performance car. 0-60 in 5.2 seconds and storming acceleration that continues way after that - I'd call that a performance car. Not a sports car - as you say, it's really a grand tourer - but definitely a high performance one.

And if you want to know which I'd rather have, an XKR or an Esprit, well it'd be an Esprit. Sport 350. Probably my favourite drive out of all the cars I've tested. Have to say I did enjoy the original XKR coupe though - especially the whine of the supercharger...

Graham,

I agree with you on the Jag as being a Grand Tourer. As far as performance, I also agree that it has pretty good forward speed, although it's numbers are being replicated by a somewhat disturbing number of Coupes and Wagons these days, so maybe the bar is rising. There was once a day, not too long ago, when 0-60 in 6.5 was remarkable. I think we're getting close to the absolute mark however, because people's ability to shift is limited. Maybe automatics are the only way to break through to lower times. Btw, I think your analogy of your Grandmother being able to go fast in the XKR detracts from rather than supports it's reputation as a performer...just my $0.02- Happy Motoring! Jim '85TE

[fatbutt]

Absolutely, speed alone does not make a sports car. Autocar recently provided a subdivision between Ferrari 360 vrs Porsche 911 and XKR vrs Maserari coupe - this is something that seems very correct IMHO. The ferrari and porsche are sports cars, the Jag and Maser are sports coupes.

I've an XJR which is just as fast as an XKR and I'd never class that as a sports car! Now, I've never driven an XKR but I've driven an XJS (on which the XK is based) and its too damned heavy. I jumped out of my MX5 (don't laugh) into the XJS and I couldn't beleive the difference. Sure, the XJS was quicker but it felt like a slug when you threw it around. From what I've heard of the XK8 series since it was launched the effect has been the same.

The gulf of difference between my Griffith and my Jag is huge: something comparible to the Esprit and XK8! While the Lotus may be nimbler, you can't drive it across continents the way you can with the XK.

And all this guff about Lotusguy's Hp output, surely its a warmed over special and so a completely invalid arguement. A stock Esprit is slower than an XKR - a modified one is not. Fine. Modify an XKR and I'm sure it'd go quicker, so why compare the two re. outputs?

Personnally, I like esprits, they look great. But (until the V8 came out) they were a small displacement engine with a turbo and sounded like crap, which put me off totally. From what I've heard, the V8 is only marginally better re. aural output.

[JonGwynne]

johnelliott said:

JonGwynne said:

johnelliott said:

JonGwynne said:
The XKR is a high-performance car. And a significant number of "performance" marques are supercharged. Jaguar, Aston Martin, Mercedes all offer supercharged models at the moment. Many other marques have done so over the years.

As has already been explained to you, the fitment of superchargers to the above cars is not an engineering/performance decision, it is a MARKETING decision.

John

Is that an assumption on your part or do you have specific experience with this?

It is an assumption on my part, but one that is based on observation. Other assumptions based on my personal observations are that(1) night will follow day, and that (2) you will not hear any argument that shows that turbochargers have major advantages over superchargers

John

I didn't say that turbochargers don't have advantages over superchargers as a means of increasing engine power. Clearly they do. They have disadvantages as well. Different tools for different jobs.

I'm just saying that the claim that turbocharging is "better" is a subjective one and even if it is right in one specific situation, that doesn't make it objective fact.

As to your assumption that marketing is the only reason to use a supercharger instead of a turbocharger, I'm simply saying that you're wrong.

There are certainly engineering reasons to prefer supercharging and your refusal to recognize this is puzzling.

And when you say your assumption is based on "observation", can you elaborate at all? What sort of observation? Have you attended marketing meetings where these sorts of decisions were made or are you just making your assumption based on the types of customers who drive supercharged Jags, Astons, Mercs, etc.

That's no less absurd than assuming that the preference for turbocharging is hormonal because of the number of testosterone-addled boy-racers who favor Mitsubishi Evos, Cossies and the middle-aged equivalent who dart around in their 911 turbos trying to pick up women half their age.

[v8guinness]

JonGwynne said:

v8guinness said:

How about aftermarket turbo kits for the Aston Martin V8? With those ratty old Rootes blowers, AM were able to get 600bhp and 600lb/ft of torque out of their 5.3L V8 by the end of its life.

Funny old thing but those Astons have around 900bhp before the Supercharger...

Naturally, they're looking for a way to try to drop a third of the engine's power...

Nice try.

Ok, I'll explain better, the Astons Superchargers take around 300-350bhp to drive, therefore it has to be built strong enough to cope with 900bhp through the crank... a handicap a Turbocharger doesn't cause... btw Jag claim their Supercharger on the lastest S-Type R 'only' takes 70bhp to drive it at full power.

[accident]

lotusguy said:

PS - As this was brought up, I'll comment. Stock horsepower on carburetted Esprit is 218bhp@6,250rpm and 200 ft.lbs @4,400rpm of torque. My car has been dyno'd at 258bhp@6,200rpm and 238 ft.lbs. torque@3,900rpm. This yields a horsepower/weight ratio of 0.096:1

---

lol @ lotus guy.
after i said he was perhaps overstating his case buy saying that he was maybe over estimating the performance of his plastic car he responded with"the only car faster than theTT Esprit V-8 was a Viper. This comparison was even filmed and shown. Granted, there are faster cars, there will always be. I concede your point, perhaps I can only smoke 95% of the others out there, or, heavens forbid, it may be as low as 93%. In your 'expert' opinion, what would it be? I don't see any mention of the car you drive, either in your post or on your profile ...Hmmmmm???? And, can I help it that you can't shift a car?? All in fun."
and then i find out he has a mild tuned carbed 2.2 turbo.
i had talbot sunbeam rally car with more power than that(same 2.2 lump only atmo)and my knock about tow car worth approx 600 gbp would give you a good run on any road in the wet(more power=better,more steel=worse,more traction=better)
as for the gear change on the esprit ,be honest you cant claim its smooth or precise in its opperation can you?
im not saying its not usable,just that compared to any good setups it feels clumsy and botched.
oh and my fun car is a 5000 gpb 900 cc 375kg red thing that will beat your esprit to 60 by nearly a second(on road tyres of couse)however its terminal speed is only about 130 mph,but thats enough for most tracks and roads in the uk.