why such a low power output????????????????

Discussion in '1990 Jaguar XJR-15' started by DR GODAGUN, Jan 14, 2003.

  1. if its a race car why dont it have good power ???????????????
     
  2. Re: why such a low power output????????????????

    i agree for such an expensive high tech car this is a stone age engine
     
  3. Re: why such a low power output????????????????

    i cos some races doesent allow over a certain hp rating. and this would still #$%#ing fly
     
  4. Re: why such a low power output????????????????

    low power output? 450 hp for only 1050kg. That's more than enough for me.
     
  5. Re: why such a low power output????????????????

    oh ok
     
  6. Re: why such a low power output????????????????

    Well a good answer to your question could be that it has very low output because it is a SOHC engine and it has 2 valves per cylinder, it is not turbo or supercharged and it doesn't have variable valve timing.... It's like a pushrod if you are talking about valves but it has 2 camshafts instead of one, like pushrods.... But in the mid 60's, Ferrari used this head technology (with weber carburators) and they delivered over 100hp/Liter. So this car should have been improved.... It has the output of a Mazda 323, what takes it out of problems is the size of the engine... The same story goes with the Dodge Viper... They didn't use their heads to put some technology on the engine, they just installed a simple big mass of iron.... any company could do that and make a car go fast, even Hyundai or Kia.... The weight of the car is not bad, that's technology on the structure and chasis, but the engine........... :S
     
  7. Re: why such a low power output????????????????

    LOW POWER OUTPUT- NOT POWER TO WEIGHT RATIO. It's got a damn racing-tuned V12 but it's still got a lot to improve on. 450 hp from a V12 is ridiculous. No wonder British cars are poor on performance.
     
  8. Re: why such a low power output????????????????


    British cars poor on performance???? ok... Jaguar XJ220 V6 3.5 L engine with 680bhp and a 0-60mph time of 3.3 seconds..... you call that poor performance.. oh i almost forgot it wont stop till 230mph and it was the fastest true production road car for years!

    I read in a jag magazine that the track versions put out well over 600bhp but were detuned for road use, its cheaper to detune the race V12 than to design/refit the car with a V6 of V8 that would involve a redesign of the engine housing and rebuilding it!!
     
  9. Re: why such a low power output????????????????

    with jaguar, it usually a case of not needing to tune the car to produce a high power output, but only doing what is necessary to get the job done, no more, no less...surely enough, this engine has great potential, and can be modified to the extreme, ie. bored out to 8.0L, with twin superchargers...scoff all you want, it has been done by Tom Walkinshaw Racing, the same company that owns HSV...thats right, holden lovers, ur precious HSV tuning arm is a subsidiary of an overseas company...so suck on that...anyways, the power to weight ratio allows for the car to compete with a lower power output...much like the lotus elise and GT1...small engined cars, lightweight cars..all proportional to the dynamics of what is required of these cars...if you would like more horsepower, i recommend the batmobile, it is my personal favourite car...<A BORDER="0" HREF="http://www.supercars.net/emoticons.html"><IMG BORDER="0" SRC="http://speed.supercars.net/cboardhtml/emoticons/smile.gif"></A>
     
  10. Re: why such a low power output????????????????

    Well, the XJ220 is an obvious exception (But think of the Veilside Supra's 3.0 V6 making 1040 hp).
    By the way, on tests it "only" reached 213 mph / 340 kph, not the 220 mph in its name.
    IF IT'S CHEAPER TO DETUNE THE RACE V12 THAN TO DESIGN/REFIT THE CAR WITH A NEW V6 OR V8 THEN WHY DOES IT COST ALMOST A DAMN MILLION DOLLARS!!?? yOU DAMN PISSING ME OFF, REALLY! FOR THAT PRICE, I EXPECT MORE!! I AIN'T THAT STUPID, MORON. EVEN IF I HAVE ENOUGH MONEY, I WON'T WASTE ANY OF IT ON CRAP.
     
  11. Re: why such a low power output????????????????

    Whoa there budy, here is another exception to "poor performing jags". Jag built this car that did 60 FASTER THAN THE XJ220. Its called the XJR 15 dumbass. 3.1 is bad performance? And how bout using a v12 to produce low horsepower rather than a v6 to produce high because the v12 could be just a little bigger but without super or turbo chargers (no lag and better reliability) and a far broader power band? or is that hard to contemplate. This car performs insanely well and i doubt it could accelerate much faster with more horsepower ne way, its rear tires already spin like a mother#$%#er on acceleration
     
  12. Re: why such a low power output????????????????

    Yeah, but with more power, it would perform better, but of course, there would be more mods to handle the power. But it won't hurt cause it already costs a million. I mean, for a million, I expect MORE.
     
  13. Re: why such a low power output????????????????

    Nice looks, but low power for a race car.
     
  14. Re: why such a low power output????????????????

    You have to remember this car was released around 1990, there weren't 600 HP cars all over the place back then. The top road cars back then like the F40 (478 HP) and 959 (450 HP) were way ahead of the average performance car. A freakin' Corvette only had 245 HP when the XJR-15 came out and a Porsche 911 Turbo 315 HP!

    Plus look at the acceleration, that's the bottom, line. The XJ220 would have been much better with a 540 HP version of this V-12 instead of the turbo V-6. The Le Mans verions made 700 HP.
     
  15. Re: why such a low power output????????????????

    er, HSV has a PARTNERSHIP with TWR, TWR does NOT own HSV. Holden owns HSV, but HSV is an outright company.
     
  16. Re: why such a low power output????????????????

    Why use a turbo'd engine? Turbo'd engines suffer from lag (if you press the accelerator, you have to wait to let the turbo spin up). Normally aspirated engines deliver instant power.
    Ofcourse there are engines with a higher hp/liter figure, but the higher this figure, the shorter the lifespan of the engine. Think of F1 engines, they can be thrown away after each race. American cars from the 60's, 70's or 80's are still around because their low hp/litre ratio.
     
  17. Re: why such a low power output????????????????

    Firstly, this is a racing car, built by TWR. I'm sure the engineers are capable of getting more power out of this engine.

    Secondly, competition cars are subject to power restrictions, amongst other things.

    Thirdly, the specs may be wrong, they frequently are at Supercars.net.
     
  18. Re: why such a low power output????????????????

    I think that the stats are wrong as usual,im sure it has over 600.Or and RalphCM is an idiot,british cars arent poor on performance:TVR's,Westfields,Catherhams,Radicals,Marcos and Noble would destroy just about all around a track.
     
  19. Re: why such a low power output????????????????

    450 was lots of horsepower when this was released. Godagun, don't make stupid threads to get overenthusiastic indie people fighting each other.
     
  20. you aint that stupid?

    i don't know about that..
     
  21. SOHC 6.0 liter V12 with 450 hp...now that is pretty crappy. Granted, I'm sure there was a power limitation for the racing, but...come on, I know Jaguar can do better than this. They're known for having engine problems when they start hitting higher displacements. Why not sport-tune a smaller engine? That's why they had to replace the 6.0 liter V12 on the original XJ220 concept back in 88 since the displacement was giving it problems. Just stick to smaller stuff and work on technology from there.
     
  22. Absolutely. The reason for this "low" power output is stone-age technology. Like the engine in the original Viper, this engine was primitive even for the early 90s.
     
  23. Umm... I remeber reading reports about this car as being "Too powerful to control." and "Narly undrivable in acceleration". That "The racing drivers were afraid to go full throttle in the road version," so as for performance, obviously there was no lack of power in the car, at least not for the design, and in fact you'll see most older road-going LMP-2 cars have less under the hood than you'd expect, at least as far as power is concerned.

    However there is more to a car than just the power output number, a V12 out-performs a V-6 when they opperate over a certain power level due to RPM advantage, gearing, throttle feel, and throttle response.

    The reasons are several:
    Tubocharged engines in 1990 were more peaky than honda engines today, you had... nothing... nothing... nothing... EXPLOTION, this made high-powered turbo cars of the day difficult to drive on the road.

    Supercharges were a better option for peakyness, but they had crappy comparitive efficiency to a naturally aspirated engine, as they use a percentage of the power from the engine to opperate (Between 3 and 20 percent.) This means that in a race where pit strategy is important (Esp. Endurance racing (what the car was designed to be raced in)) having a massive supercharger is probably not the best system of opperation.

    So we're left with a naturally aspirated engine at this point, so now we're dealing with the variables of valves, displacement, rotating mass, and cylinder size, as well as bore to stroke ratios (Power:Torque ratio).

    The XJR-15 has a relatively even bore:stroke ratio producing a comparatively even number between the two for the power of the engine, and the cylinder count, a reasonable choice.

    Then comes rotating mass, while DOHC and QOHC, and more valves to increase power, more valves=lower economy (more fuel in the engine per RPM) and the extra camshafts used to drive them increase rotating mass, reducing maximum RPM values, shortening time between shifts, and thus decreasing acceleration by up to .041 seconds per shift (that's a lot).

    So, for minimum rotating mass smaller numbers of cylinders seems appropriate as well, however you also want accessable power at all RPM to the wheels (mostly by converting that even torque<A BORDER="0" HREF="http://www.supercars.net/PitLane?displayFAQ=y"><IMG BORDER="0" SRC="pitlane/emoticons/tongue.gif"></A>ower to a continual flat number of torque or power through good gearing). This leads to the fact that for those power levels the V6 has a very peaky setup, with most power at higher RPMS, which increases engine vibrations tremendously, which is bad, as it wears on motor mounts etc. especially with an engine that big, that's why you rarely see a 4 cyl. over 2.3L. so no V6 then, next is the V8 which isn't a bad choice, low rotating mass, good even power distribution, and it wouldn't have been a bad choice, except that the cylinders would have to have been much bigger, and that would lead to a less optimal bore:stroke ratio, leading to the use of a V12.

    (At least that's how I'd narrow it down, the engineers at jag. working on this car probably had a lot more info. to go on than I do, and a lot more experience, but that's the general argument.)

    Basically: A transmission can better use 480HP at 6200RPM and 420FT/LB of torque at 4800RPM than the same at 7000RPM and 6200RPM respectively, or 390HP and 500 FT/LB at slightly higher RPM for each.

    Also the power to weight ratio in this car is about 382.97 HP/Ton and 305 Ft/Lb per Ton, about the same as an LMP1 car, compare to the 1000HP Velliside supra that's about 20 lower in both, and the RPMs make is much less accessable in a tight course, and it'd fail in an endurance race horribly (nothing wrong with that it was made for something different so it was designed with a different objective.)
     
  24. 450hp is not bad for a light racer.
    it probably ate the competition
     

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