818 stock WRX setup and Mk III/IV Roadster side by side comparison

[skullandbones]

Performance Numbers, Car & Driver Magazine
The vehicle tested was powered by a modest 325 HP small block Ford 302 engine with an 8.8″ Ford rear end with 3.55 gears and Factory Five 3-link suspension.

Performance
0-60 in 3.6 seconds
0-100 in 9.0 seconds
1/4 mile in 12.3 seconds @ 113 MPH
70-0 braking in 181 feet
Skid pad lat G – 1.00
Curb weight – 2,162 lbs.
Price as tested – $32,109

Based on the above specs I would like to see how the two FFRs would compare in the real world. FFR is already doing launch tests for the go kart 818 so it would be really interesting to see them launched side by side when a prototype body is revealed. How about a time trial around the same road course like used for the demo of the go kart. I bet it would be more interesting than the challenge with the Shelby 427 done on Muscle Car TV. Thoughts? WEK.

[shinn497]

Since the 818 weighs 300 pounds lighter, and has a stiffer chasis, wouldn't it perform Much better on a track? But yes I too am interested. I think the real question would be for a modded 818 that cost the same as a stock mark IV.

[skullandbones]

I don't know the reason for the big $$ figure for the roadster (maybe paint, big name brake kit, etc) but the running gear is pretty basic (3 link should perform well on track) and so the roadster would have more hp but the 818 would have weight advantage with a little shortage on hp. I'd just like to see how well the 818 will fare. It may be closer than you think. WEK.

[PhyrraM]

I would think the much lower polar moment would be the defining difference between the siblings.

[Silvertop]

I would think the much lower polar moment would be the defining difference between the siblings.

Polar moment? Whuzzat? Center of Gravity? Don't mean to sound ignorant. I just don't know the term...............

[leetfade]

It's that moment when you realize a polar bear thinks you're lunch...

[cmcintyre]

Polar moment of inertia =

spinning skater with arms out = high polar moment, slow rotation. 944 with transaxle. Barbell.

spinning skater with arms in = low polar moment, fast rotation. Lotus Europa. Bowling Ball.

[CallawayTurner]

Polar moment of inertia - a function of both the mass and the distance the mass is from the center of rotation. He is referring to the rotation about the vertical axis (turning the vehicle). The 818 will have both less mass and its mass will be closer to the axis of rotation so it will take less torque (from slip angle of tires, not from engine power) to turn the vehicle. In other words, the 818 will be much easier and quicker to turn.

As demonstrated by the figure skater example. Lower polar moment = faster turning.

[metalmaker12]

Polar moment of inertia - a function of both the mass and the distance the mass is from the center of rotation. He is referring to the rotation about the vertical axis (turning the vehicle). The 818 will have both less mass and its mass will be closer to the axis of rotation so it will take less torque (from slip angle of tires, not from engine power) to turn the vehicle. In other words, the 818 will be much easier and quicker to turn.

As demonstrated by the figure skater example. Lower polar moment = faster turning.

In the engineering world it is all about power to weight, Friction (Positive/Negative) Traction and drag coefficient properties in relation to the aerodynamic shape of the mass.

Roadster: 325hp=(loss in drivetrain FRWD) 275whp@2200lbs=+driver=275whp@2400lbs =1hp per 8.7 pounds
Traction/Drag will play a part, lets just say they are close on the two

818: Wrx 225hp=( loss in drivetrain RRWD) 200whp@1800+ driver=200whp@2000lbs=1h per 10 pounds= loss
818: Sti 300hp=275whp @2000 =1h per 7.3 =Win!! and with a tune forget about it stock roadster
Now obviously as you mod these stock mills things will change a lot

[skullandbones]

In the engineering world it is all about power to weight, Friction (Positive/Negative) Traction and drag coefficient properties in relation to the aerodynamic shape of the mass.

Roadster: 325hp=(loss in drivetrain FRWD) 275whp@2200lbs=+driver=275whp@2400lbs =1hp per 8.7 pounds
Traction/Drag will play a part, lets just say they are close on the two

818: Wrx 225hp=( loss in drivetrain RRWD) 200whp@1800+ driver=200whp@2000lbs=1h per 10 pounds= loss
818: Sti 300hp=275whp @2000 =1h per 7.3 =Win!! and with a tune forget about it stock roadster
Now obviously as you mod these stock mills things will change a lot

First off the roadster used for the performance test was not stock. It would have been a 225 hp 5.0 but thats what they used to establish the performance numbers that most of us have seen for years about the roadster.

I find it interesting that a high polar moment is a desirable number for stability to avoid a tweechy and unpredictible handling. The roadster obviously would have that. Will the large differential of the 818 hanging out back give it a reasonably high polar moment to allow for the same advantage? I don't think we have seen enough of the performance traits of the 818 to tell yet. IMO. WEK.

[el_jefe]

I find it interesting that a high polar moment is a desirable number for stability to avoid a tweechy and unpredictible handling.

Anyone who says that has never watched a Spec 944 race lol

[PhyrraM]

Let me expand upon my earlier comment.

I don't feel there will be much difference in acceleration capabilities between the Roadster and the 818 (even the GTM and HotRod too). All are light cars with limited traction. All have various challanges getting the power to the ground. All have proven, repeatable, and well documented pathways to obtain more power than the weight/tire combo can handle. Acceleration will basically be a wash.

Where the 818 differs from the Roadster and the HotRod is the placement of the mass/weight and the total weight. Where it differs from the GTM is total weight.

When I quickly said 'the defining difference will be the polar moment', I should have phrased it "the defining difference will be its cat-like reactions". The 818 should be on a completely different level compared to ANY car with a big V8 over the front wheels. It should be noticably different than the GTM with a 400+pound motor over the rear wheels (albeit that helps the GTM with traction). I think the 818 is going to be all about finesse and feedback. Rewarding practice and patience over butt-clenching 'yank-and-spank' antics that some cars seem to prefer.

Not to say that any of the other FFR cars are bad - I've read enough to know they are considered great drivers cars - I just see the 818 as being capable of even more.

[metalmaker12]

Let me expand upon my earlier comment.

I don't feel there will be much difference in acceleration capabilities between the Roadster and the 818 (even the GTM and HotRod too). All are light cars with limited traction. All have various challanges getting the power to the ground. All have proven, repeatable, and well documented pathways to obtain more power than the weight/tire combo can handle. Acceleration will basically be a wash.

Where the 818 differs from the Roadster and the HotRod is the placement of the mass/weight and the total weight. Where it differs from the GTM is total weight.

When I quickly said 'the defining difference will be the polar moment', I should have phrased it "the defining difference will be its cat-like reactions". The 818 should be on a completely different level compared to ANY car with a big V8 over the front wheels. It should be noticably different than the GTM with a 400+pound motor over the rear wheels (albeit that helps the GTM with traction). I think the 818 is going to be all about finesse and feedback. Rewarding practice and patience over butt-clenching 'yank-and-spank' antics that some cars seem to prefer.

Not to say that any of the other FFR cars are bad - I've read enough to know they are considered great drivers cars - I just see the 818 as being capable of even more.

I agree, i think with the right engine (Say STI), tires, and suspension specs. this car will be a winner. The kicker is that it will still be more affordable than all the others, and be maybe the toughest competitor on the track and street.

[skullandbones]

Well, it's true I haven't followed Porche racing although I think I may have seen a few (helped rebuild a speedster). I've watched a lot of races: Nascar, Road Atlanta, dirt track, go karts. So the statement I made was not an empirical one just an opinion backed buy some reading on the subject (I thought someone might add what they thought about the 818 stability. I think someone else started the conversation about that parameter. So why not add value to the conversation by including your expertise on the subject instead of assuming something about my life experience? Or you could make the statement as is and then support it. That would be worth while. Thanks, WEK.

[el_jefe]

Well, it's true I haven't followed Porche racing although I think I may have seen a few (helped rebuild a speedster). I've watched a lot of races: Nascar, Road Atlanta, dirt track, go karts. So the statement I made was not an empirical one just an opinion backed buy some reading on the subject (I thought someone might add what they thought about the 818 stability. I think someone else started the conversation about that parameter. So why not add value to the conversation by including your expertise on the subject instead of assuming something about my life experience? Or you could make the statement as is and then support it. That would be worth while. Thanks, WEK.

It was a joke, as some folks call the Spec 944 class Spec Drift after watching the tail slide out from car after car. . .

[shinn497]

One big advantage I think the roadster certainly has would be its neutral weight distribution (50/50). In fact I might surmise that it would have a lower polar moment of inertial than the 818. It is cab rearward with the motor and tranny set further back, behind the front axle, and closer to the center. The 818 is projected to have a 42f/58r distribution and has a cab center design with the motor in between the center and rear axle. As noted before, so of the transmission sits behind the rear axle, but I remember seeing that this is project to be just 20% of the mass. Remember that the moment of inertia increases linearly with mass but as the square of distance. In other words, placement is important. An engine placed twice as far will have 4 times the moment of inertia. OF course I am not so sure how different the cars weight distributions are and indeed that is difficult to actually measure (though would be easy if inputed into a cad file of some sort.

One thing I also noticed is that the FFR roadster has a shorter wheel base than the 818 (90 versus 95 inches). This would reduce the turning radius and make the handling sharper. This is a tough call indeed.

One thing no one has mentioned is turbo vs NA. The roadster won't have to deal with turbo lag at all.

Anyway my prediction would be that a stock 818 would have a tough time against the roadster and certainly a spec racer. Certainly it would oversteer and that would take some getting used to. However it would have greater potential as well. It has intrinsic advantages, lighter, more compact engine, and lower COG all come to mind. In addition, greater power, quicker spooling turbo, better setup suspension would make it cream even a heavily modded roadster. Cost is also the 818s biggest advantages. Roadsters can get expensive really easily. I've seen some 80k ones 0.o .

Perhaps the biggest advantage is the experience FFR has put into the design and the collaborations they are doing with other parts and subaru tuning companies. I'm sure everything about the 818 is intentionally designed to wring out the most performance given the constraints they have put on themselves (weight, price, and buildability). This is FFR and 15 years of experience we are talking about.

[Kalstar]

Stock for stock......

1) GTM. 350hp @2350 lbs = 6.7 PW
2). 818 227hp @1800lbs =7.96 PW
3). Roadster 215hp @ 2100lbs = 9.76 PW (assuming a 95 GT was used as donor)

The hotrod has no stock engine but assuming A base 306CID 340hp M-6007, the hotrod would push the 818 to #3. these all assume straight line acceleration.

[leetfade]

Are people really intending for this as a drag car? I see this as much more of a nimble road course, auto-x, time attack style car that you can drive daily and turn heads in. The agility and rigidity of the car are what I'm looking forward to. I would think it has a leg up on many of it's predecessors in that area.

[Xusia]

Are people really intending for this as a drag car? I see this as much more of a nimble road course, auto-x, time attack style car that you can drive daily and turn heads in. The agility and rigidity of the car are what I'm looking forward to. I would think it has a leg up on many of it's predecessors in that area.

+1!

[skullandbones]

Thanks for the clarification. I obviously missed the joke (not enough exposure to that sort of racing)! Sorry. But I did have a look at a 944 a few weeks ago with my son to buy and flip it. We ended up not getting it but I couldn't forget my first impression: "that's a Porsche?". I had never seen one up close and under the hood. WEK.

[Xusia]

It's really more of an Audi with the Porsche name badge IMO! LOL

[RedJoker]

I, too, would be interested in the handling difference. If you haven't seen the roadster, you should know that it's not a big V8 sitting over the front wheels. And it's not just the center of the engine that sits behind the front wheels, the ENTIRE engine does. In fact, I still have about a foot from the front of the crank pulley to the centerline of the front wheels. My roadster has a 49/51 F/R weight distribution. Another fun fact is that the roadster drive shaft is only 10 inches long! The transmission almost connects directly to the rear pumpkin. Don't under-estimate the roadster; it's still Factory Five, after all.

Fun stuff indeed!

[skullandbones]

I, too, would be interested in the handling difference. If you haven't seen the roadster, you should know that it's not a big V8 sitting over the front wheels. And it's not just the center of the engine that sits behind the front wheels, the ENTIRE engine does. In fact, I still have about a foot from the front of the crank pulley to the centerline of the front wheels. My roadster has a 49/51 F/R weight distribution. Another fun fact is that the roadster drive shaft is only 10 inches long! The transmission almost connects directly to the rear pumpkin. Don't under-estimate the roadster; it's still Factory Five, after all.

Fun stuff indeed!

I'm glad you are impressed with the design of the roadster. So am I. When I set the engine for the first time, I couldn't believe how far back it was. I know you see a hundred pictures of roadsters but if you are working on it and it's right there in front of you, it has more effect. I can't wait to see the two siblings side by side one day to see really how it goes. Just like the Muscle Car Challenge but this time there would be some real competition like a couple of pretty evenly matched boxers exchanging blows!! WEK.