JGTC Cars

[princenigel]

Why are JGTC cars (and their european equivalents) in GT so expensive? Do they actually cost that much to develop? What exactly sets them apart from their roadgoing versions. As far as I know, it's just increased power, reduced weight, and upgraded suspension.. surely these improvements can't add up to the car costing more than 1,500,000??

Also, how does one make a production car in RL/GT match the handling of a jgtc car, to get the same sharp turn in/tight turning circle? Is it done in RL by increasing the steering rate? Can it be accomplished somehow in GT?

 

[Cap'n Jack]

Most the JGTC cars are not anything like the road cars. Take a look at a GT500 Skyline GT-R and a road going R34 GTR, theres a big difference. I reckon the JGTC cars are probably made out of Carbon Fibre, so that would explain why they're expensive

 

[Jacks]

JGTC cars are mostly made of carbon fiber, which costs a hell of a lot of money. My dads mate had a front wing made from carbon fibre for his race car and it cost nearly £10,000 thats ~$18,000 - $20,000. The other differences from the road cars are. The gearbox is a semi auto racing gearbox, engine is completely modified and basically is nothing like the original engine, Carbo-ceramic brakes (i think), basically theres nothing from the original car. and yes if you could buy one in real life it probably would cost ~$1,350,000.

You cannot make a production car match the handeling of the jgtc car unless you where able to widen the body lighten the car, put racing slick tyres on wider wheels, and use a racing suspension. Some of this can be done on GT but not all of it.

 

[princenigel]

forgot about carbon fibre, it would definately jack the price up a bit

i did some research and am pretty sure that what it mainly comes down to is the steering ratios. an rx7 lm handicapped with simulation tyres will still spank a fully modified production version with more power, around the same weight, and race tyres... but if you could lower the steering ratio (see below), the odds would probably be a bit more even.. for a lot less than whatever the LM costs.



"Steering ratio is the difference in how many degrees your front wheels are turned compared to how many degrees your steering wheel is turned.......

The lower the ratio (12:1) the quicker the steering response. You'll notice that using a lower steering ratio will require less turning of the wheel to negotiate a corner. This low steering ratio can result in a twitchy car since the smallest of steering inputs will be felt in the car. It is very easy to over steer a car with such a low steering ratio.......

A car with a higher steering ratio (32:1) will require more steering input to get through a corner. Too high a steering ratio might give the feeling of a tight race car as you find yourself turning the wheel further to negotiate a turn....

As a general rule of thumb, the smaller the track & tighter the radius of the turn, the lower the ratio you'll want to run. Road courses are a track with slow sharp turns that would require a lower ratio. High speed long sweeping corners would not require such a low steering ratio since you are not required to turn as sharply on tracks like these.

Steering Ratio synopsis:

The lower the ratio the quicker the steering response.

The higher the ratio the slower the steering response.

Lower ratios require less turning of the wheel to negotiate a corner.

Higher ratios require more turning of the wheel to negotiate a corner."

 

[JNasty4G63]

.....i did some research and am pretty sure that what it mainly comes down to is the steering ratios. an rx7 lm handicapped with simulation tyres.....

Well, first off, there is no REAL RX7 LM. That car is just a "Gran Turismo" special. Its just a fun, fast car you get in the game, not a real model.

And, while I'm sure the steering ratio is probably different with the JGTC cars, that has very little to do with them being so fast and expensive.

JGTC is the Japanese version of NASCAR. The cars are built to LOOK like the stock version, but under the skin, its all race car. The chassis is totally different, the body is all CF, the engine and trans are completely different, and the engine management is using custom hardware for on track changes, and so on and so on.

They are very high level race cars, especially the GT500 cars. They are very fast, handle very well, and are very expensive cars. Thats why the $$$ it high.

Hilg

 

[[FPV]Rusty]

one other factor that makes them so much better is their center of gravity, very low. You may notice from some of the slighty older model JGTC cars to the latest ones (eg- 03' Nismo model) the cars have gotten lower and lower, the ride height is so low the wheel arches on the Nismo JGTC skyline protude higher than the bonnet, & the bonnet on the Woodone Supra is also been flattened out to give space for the wheel arches, definately totally different low to the ground chassis.

 

[xcsti]

My dad (an avid auto motive enthusiest) thought the same thing about jgtc cars. He thought they were just tuner cars not full racers. The he watched a C+D where they mentioned that the guys at nissan had decided to replace the rear glass with carbon fiber and install a camera for the driver. That just seems a bit excessive.

 

[JNasty4G63]

.....the guys at nissan had decided to replace the rear glass with carbon fiber and install a camera for the driver. That just seems a bit excessive.

Might be excessive, but its not new, thats for sure. Thats a common thing now a days for sports car racers. The new C6-R has that setup, as does the Caddy CTS in World Challenge I believe. As the cars get more and more chassis additions and roll-cages get bigger, the view out the back with the normal rear-view gets worse, or goes away completely. Couple that with the fact that many of the drivers seats are mounted to the floor with no brackets to get the COG lower, and you probably can't see out the back anyway. So, why not put a small little cam with a semi-wide angle lens and mount a screen on the dash. Its not like they look out the thing all the time. Just a quick glance to see if someone is behind or passing. Just one of those new high-tech things in racing these days. Might seem a bit excessive, but then again, just about everything in racing is.

Hilg

 

[princenigel]

thanks for the replies.. FPV now that you mention it, the race cars sure do go a lot lower than the production ones. will test the theory out tonight by slamming a Lotus Elise, which from memory can go pretty low.. if i can get it to handle somewhat like a jgtc i'll report back.

jnasty i had no idea, i thought the thing was real and raced in le mans.

PS: FPV Now that I think about it, the SPOON S2000 has race car handling but is NOT excessively lowered to the ground (see below):




So perhaps it's the steering rate after all... Tried looking up it's suspension specs but they are pretty hard to come by; did find some nice pics though

 

[princenigel]

Just found this, a complete listing of suspension parts on the Spoon S2000. Presumably, somewhere within this list is the secret to making a production sports car handle somewhat like a racer.

couldn't see anything about steering ratios, but the "suspension arm set" sounded promising

http://www.spoon-sports.com/chassis.php?chassis=AP1&type=Suspension

http://www.spoon-sports.com/s2000.php

 

[princenigel]

Apparantly the unsprung weight can have a significant effect on turn-in/steering response as well; i imagine the JGTC cars would have wheels that weighed less than an rx7's cigarette lighter

 

[Jacks]

I don't quite understand what you mean about steering response, a real JGTC car has only 200 degrees of steering. which of course will make the car more responsive if you turn the wheel more, but its useless unless your tyres can grip that much, if you fit a jgtc steering column into a standard skyline or whatever it still wouldn't corner like a jgtc car. Also i went home and thought about it and its downforce that makes a car turn quickly, the front splitter on a JGTC car can create ~150kg of downforce at 75mph, thats an extra 150kg over the font wheels, this would also help front end grip and steering.

It all comes down to front end grip. JGTC cars produce a lot of downforce, have sticky tyres, and have a good suspension setup to give them the best grip possible 👍

Lower centre of gravity doesn't mean that the car is lower to the ground, if you have ever seen into the engine bay of a sports car the engine is always pushed right to the bottom corner of the engine bay and all weight is at the bottom.

 

[Jacks]

Oh and the spoon S2000 doesn't have race car handeling in real life, PD have added huge amounts of downforce to a car that has no visible downforce producing modifications, this was disscussed somewhere before, i'll go find a link

Here we go: https://www.gtplanet.net/forum/showthread.php?t=44679

 

[princenigel]

I don't quite understand what you mean about steering response,

Basically I just want to know how to make a light sports car turn as tightly as a jgtc. At first I thought they turned better due to racing slicks, but even handicapped with simulation tyres, the jgtc's/spoon s200 race car will still out-turn an rx7 or s2000 with sport tyres.

thanks for clearing up that lower centre of gravity stuff, never knew it had more to do than simply lowerering the susp. i did some trials today and last night, and lowering an elise test car as far as it would go (which i used to think would compromisde handling, due to bottoming out) made it turn much sharper. also, after raising the s2000 race car as high it would go, it began to handle more like a normal production car. so i guess centre of gravity and downforce must be it then, which is pretty disheartening as i was wondering if it were possible to get my rl 200sx to turn as sharply as a jgtc!

Also i went home and thought about it and its downforce that makes a car turn quickly, the front splitter on a JGTC car can create ~150kg of downforce at 75mph, thats an extra 150kg over the font wheels, this would also help front end grip and steering

the thing i don't get about that is, the race cars still turn tightly at low speeds, when there is not really likely to be much downforce generated at all. i remember tiff needle reviewing the 360 modena, and saying all the money spent on the underbody aerodynamics is not really going to matter much to the average customer, since the downforce it generates at roadspeeds is insignificant. as you said it's prob the low centre of grav which comes into play at low cornering speeds..

Oh and the spoon S2000 doesn't have race car handeling in real life, PD have added huge amounts of downforce to a car that has no visible downforce producing modifications

dissapointing to hear that, but glad you cleared that up, i've been going crazy trying to figure out how it handles so well. PS is it possible that the real spoon does handle as well as in GT3, but due to a lowered engine/centre of grav as opposed to more downforce?

 

[xcsti]

If you want the turn in to be quicker I would play around with the camber. I would also put a wing on the car before doing this because the car can get real unstable at high speeds.

 

[princenigel]

Conducted more tests today, using my NSX R against the ARTA NSX. Both had the same ride height (93mm), camber, spring rates, and sports tyres, but my NSXR has the advantage in weight, torque and horsepower.

Even with the NSXR's power-to-weight advantage, the ARTA was still quicker around Cote D'Azur (inspite of someone blocking the TV at the chicane). It's turning circle was noticeably tighter at moderate to high speeds, but when things slowed to a crawl on the final bends the Arta turned *no better* than my NSX R.

So it seems that downforce is the answer; This would also explain the exorbitant price tags for jgtc cars, that is apart from the body being carbon fibre the wings and underbody panels would need to be engineered and wind tested.

IN CONCLUSION, giving a road car more power than a race car is relatively easy, and so too is getting firm suspension; but getting a roadcar to turn as tightly as a race car is practically impossible, since racers have far lower centre's of gravity and far more downforce than any modified prod car could hope to achieve. Thanks for all the suggestions/info

 

[Jacks]

dissapointing to hear that, but glad you cleared that up, i've been going crazy trying to figure out how it handles so well. PS is it possible that the real spoon does handle as well as in GT3, but due to a lowered engine/centre of grav as opposed to more downforce?

It would handle better than an original S2000 especially through low speed corners, but it wouldn't stick to the roads as well as in GT due to the lack downforce which means it wouldn't make much difference through high speed corners. Also i'm not 100% on this but does an S2000 have an inline 4, if it does it would most likley be already moved to improve the centre of gravity.

About your 200sx i've looked up some stuff you might be interested in:

Most people with 200sx change there wheels for 17" x 9" on the rear and 17" x 8" on the front, instead of the standard 15" x 6" wheels, apparantley theres plenty of room to fit these wheels btu you'll have to check that out for yourself, the tyres to fit these wheel are not cheap and ride comfort will suffer but hey its a sports car 👍

Also a nismo suspension kit (springs and Dampers) should help a lot.

 

[princenigel]

Also i'm not 100% on this but does an S2000 have an inline 4, if it does it would most likley be already moved to improve the centre of gravity

yep it does, and now that you mention it the S2000 has almost a 50/50 weight distribution. After all this talk, the first mod I'd want to try with any real car is modify the chassis so that the engine sits lower (would prob have to fit a dry sump to the engine as well?), then fit lowered race suspension.

Most people with 200sx change there wheels for 17" x 9" on the rear and 17" x 8" on the front, instead of the standard 15" x 6" wheels, apparantley theres plenty of room to fit these wheels btu you'll have to check that out for yourself, the tyres to fit these wheel are not cheap and ride comfort will suffer but hey its a sports car

Hey thanks for looking that up, the only prob is i can't modify the car at all due to unsurance! should have looked up premiums and policies before i bought it

 

[JohnBM01]

Look closely at a JGTC Race Car. Even if you could take away the rear wing, specialiezed front and rear bumpers, overfender, racing tires, and hood, do you realize that they really look like their street car counterparts? Right now, I can imagine something like the Motul Pitwork Nissan Fairlady Z (in Japan. But in America, 350Z), give it the stock front and rear, no overfenders, and I think I could make a machine that looks more like its road-going version. It isn't like the current NASCAR in which the cars look almost the same in terms of aerodynamics. I don't care what anyone says, "stock" cars in NASCAR and every other emulated oval racing series with such cars (including the road racing SCCS (Stock Car Championship Series) that does all road course races) are only based on production based on looks but maybe not in terms of actual dimensions. Do a Monte Carlo and a new Charger look the same aerodynamically? Thought so. I think all or most GT racing series look very close to their stock counterparts, give or take modifications to make them perform better aerodynamically (such as that huge snorkel above the engines of the Mugen/Dome NSX teams back in 2003).

So they are pretty close in terms of looks. In terms of body material and such, not quite.

 

[VIPFREAK]

I still want to know why they cut off the rear bumper so much??

 

[Jacks]

I still want to know why they cut off the rear bumper so much??

Its all to do with under body downforce modification, something to do with the air flow

 

[Duke]

princenigel: Stick to the correct topic and no more nonsense crap like yesterday.

This board is for discussing real cars: you know, those heavy things made out of metal and plastic and glass that you may actually sit in and be able to drive in a few years.

If you're going to discuss GT4 cars, do it in the GT4 forum.

 

[VIPFREAK]

Its all to do with under body downforce modification, something to do with the air flow

I figure that but there's no other kind of race car that just cuts off the bumper like that.

 

[Duke]

They're limited in the amount of aerodynamics they can run. So what they do is run as large a front air dam as NASCAR allows, then they lift the rear skirt up high. Venturi effect and the spolier creates a bit of suction under the car to help with downforce. Also, since full belly pans are prohibited, the inside face of the back 'bumper' would be a big drag scoop if it was low enough to look more normal.

 

[VIPFREAK]

Are you following me?!

Anyway, ok yeah but it's like they just take a saw and literally chop off the bottom part of the bumper... Even in Nascrap there's some what of a "design" to it? It seems to me?

 

[Driftster]

going back to the Carbon fiber thing, I don't know about costing a million dollars, but since $ isn't as big an issue as it is in REAL Life it's alright to jack the price up a bit so you can't just buy every single one right off the bat. But a company can build you a carbon fiber EG6 body for $60,000 US. I'll look for the site again, but yeah

 

[rjones]

Why are JGTC cars (and their european equivalents) in GT so expensive? Do they actually cost that much to develop? What exactly sets them apart from their roadgoing versions. As far as I know, it's just increased power, reduced weight, and upgraded suspension.. surely these improvements can't add up to the car costing more than 1,500,000??

The GT500 cars are built from scratch, sharing almost no components from the road going counterparts. They're closer to prototype GTs than ie. GT2(now GT1) cars of ALMS. Many drivers have mentioned that the GT500 cars drive like formula cars.

 

[[FPV]Rusty]

Are you following me?!

Anyway, ok yeah but it's like they just take a saw and literally chop off the bottom part of the bumper... Even in Nascrap there's some what of a "design" to it? It seems to me?

they do not jsut chop it off, thats a big simplification of hte process, you may notice if you look at previous years JGTC cars that the high rear bumber was not the case. It is hard to see becuase they are usually plain black unpainted CF but there are now diffusers at the rear of the car that stabilize the air passing under an out of the back of the car as well which in turn stabilisers the rear end of the car a whole lot, its not as effective if the bodywork inhibits the air passing inbetween the diffusers.

 

[Duke]

The GT500 cars are built from scratch, sharing almost no components from the road going counterparts. They're closer to prototype GTs than ie. GT2(now GT1) cars of ALMS. Many drivers have mentioned that the GT500 cars drive like formula cars.

In fact, the only things the JGTC cars share with their supposed donor cars are the front and rear firewalls. Everything else is purpose-built out of carbon fibre and hung on a tube frame chassis. They vaguely fit the profile of the original car, and they are door slammers, which makes them closer to real cars than recent NASCAR 'stockers', but not a whole lot. They are nothing like as close to stock as NASCAR cars were 20 years ago.