Hyper-X

Okay, got some info.

A stock 240Z (1970-1973) weighs in at 2355 pounds. Let's say for the sake of it that the car has some lightweight parts and make it an even 2300 pounds with the driver. Curtis' car is said to have a 280 motor (not sure if it's the Z or ZX model). The ZX came in a turbo model but we all know Curtis' car is NA. The NA version of the 280ZX came in a low compression model which made less power and torque than the 280Z engine.

Assuming for the better, if he is indeed packing the 280Z motor, the normal specs are...

2754cc SOHC Inline-6
Compression Ratio @ 8.8:1
Horsepower (SAE) 149 BHP @ 5,600 RPM
Torque 163 FT-Lbs @ 4,400 RPM

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Assuming for the worst, the factory specs on a NA 280ZX are...

2753cc SOHC Inline-6
Compression Ratio 8.3:1
Horsepower (SAE) 135 BHP @ 5,200 RPM
Torque 144 FT-Lbs @ 4,400 RPM

* I sincerely doubt he'd be running the ZX motor since increasing compression ratios are illegal improvements to do in street prepared class. Minor overbore is ok.

***************************************

Assuming stock figures for the Z, using our estimated 2300 pound value and ignoring the small weight difference between having a larger motor installed,

2300lb / 149bhp = 15.44 (rounding up) NOTE: Lower figures are better.

Assuming a theoretical figure of our SM2/ASP S2000 with a few lightweight parts and less than a full tank of fuel, let's assume 2700lbs, with the sum of the power mods adding 10hp...

2700lb / 250bhp = 10.8

worst case assuming high weight #'s and stock hp #'s...

2850lb / 240bhp = 11.875

Still better than a stock 240Z using a stock 280Z transplant.

(more to come)

Hyper-X

Hypothetically speaking, if the motor is good for a solid 200HP after modding, then Curtis' car have a theoretical rating of...

2300lb / 200 = 11.5

This would be enough to match up with the S2k's figures. Wow..., and with added plus of added torque (broader powerband) and the simple fact of being lightweight provides benefits by itself.

smccurry

So wait.. you're saying that we have a better power-to-weight ratio than Curtis? Then one third of the battle is already over. The next things to work on would really be driving skill, and added sizing on the rubber.

Jimmy: buy my SSR's and I'll upgrade to the CE28N's

Here's the question. Is there a way to get bigger than the 17X7.5JJ front 17X9JJ rear without clearance issues? Would it be more advantageous to find something with 17X8JJ front 17X9JJ.
I know there are wider front fenders for sale out there (big bucks!) but I haven't really seen anything for the rear. Also, the Japan tuners often go with same sizing up front and rear (Amuse and J's racing). I think they're running 255's all around. Obviously they got it to work. Would that be ridiculous for the auto-x, or could suspension tweaking make it worth it?

Hyper-X

I'm using hypothetical numbers for the modded figures, not actual facts. The stock figures are correct as I took it off a Nissan website. I guess you could say I'm taking the best guess I can in regards to the mods. I've been actively searching sites regarding the older Z cars and the power potential with the 280Z motor on 8.8 to 1 compression ratios. Quaife makes a diff for the 240Z that provides the Torsen LSD benefit to his car, and there's clues to transmission swaps that effectively allow his 1st gear to go no better than 40mph, but allows 2nd to take it to ~60. This would explain why he's in 2nd gear for the most part and only switches down when he absolutely has to.

What's tough for us is that his power curve is broader due to the higher displacement (more power available sooner) and he can push 2nd gear at lower rpms and still accelerate effectively whereas we'd lug in 2nd if caught below VTEC... so I'm convinced that we're losing some time in that area. Torque and the duration of how long you can be within your torque range is more important IMO than raw HP for HRP, because we don't have the space like the Nationals to open up and utilize our gearing to our advantage. You on the other hand Steve don't suffer the acceleration penalty like I do on my 4.10's.

There's a ton of talk regarding certain piston designs that Z owners look for (flat top type to increase compression) versus the dished type. 6 into 1 headers, an ignition pack, carbs (weber or dellorto), cams and such. His 2.8L is good for 200HP easy if done correctly but I'll bank on his torque figures also matching the HP figures closely.

My theory to his power figures appear to be close... he's probably at a little over 200hp if he chose the mods carefully and had some light machine work done to the head, with cams, carb tuning, MSD ignition system, perhaps even a 3 angle valve grind combined with his custom fiberglass cold air box. He can't alter his final drive gearing legally beyond what's availabe amongst the Datsun Z line via the update/backdate clause to include the 240, 260 and 280 models. My guess is that he'd choose the one that provides some gear reduction to optimize acceleration.

Hyper-X

I can't predict what the effects may be if you go the same tire all around like the Amuse car. It may be hard to do without having a variety of different springs sets on hand, experimenting with various spring rates and damping control. On my car, since both springs and shock settings are fixed, doing that would only spell disaster. On your car, the damping (both on compression and rebound) is adjustable, but you're primarily stuck to using 1 spring rate, however it allows you to lower your center of gravity which is always good for stability. If the Amuse car was tuned for Gymkana use, then it may make sense, but I'm almost certain that you'd need to run a particular spring rate up front and rear with specific damping rates in order to make (4)255's work in harmony. Don't forget that the Amuse car doesn't use the same kind of tires we do and I'm suspecting that there's a mandatory alignment setting to be used on their setup... which may not be ideal for street use.

Colin is right on with the need to increase grip in your car because of the equipment you have. Gear reduction and a suspension that lacks the stroke of the OEM suspension means the extra lateral/longitudinal force will tax your tires more. If your suspension isn't absorbing the cornering forces like it should, then your tires will end up taking on the responsibility of gripping the track and doing some of the job of the suspension.

On my car, the benefits of increased grip is limited to the suspension's ability to keep the car under control from lateral forces. It's more than up to keeping the car from diving during braking and lifting the front from accelerating, but if I increase the grip potential of my tires, naturally I'd be able to apply more lateral force (higher G's), however my suspension will travel more (compress) on the outside of a turn while the inside expands making the car roll even more. Speaking for myself, I don't know if I can keep things under control when the car rolls more since I'm used to the car behaving the way it does now... I can deal with better roll resistance, but can I manage it on the worse side of things? Since the OEM springs/shocks has no additional damping control outside what Honda intended for S02 tires, the action of rebound (expansion) won't be fast enough to allow for quick side to side transitions, ending up with that "lazy feeling" in the slaloms.

If you want to apply more force side to side, then you need more grip from the tires. However you must increase the car's ability to resist roll (leaning) at the same time, otherwise the full benefit may not be realized. The other way around will involve upgrading the suspension without increasing grip. The extra lateral stability may fool you into thinking you can take the corners faster, but your tires won't be able to hold because the suspension is absorbing less energy and transferring extra stress on the tires.

smccurry

So in the short, unabridged version, what does that mean?

Probably easier and more of a sure thing to just continue with the staggered set-up and get them as wide as possible in the rear. 9JJ is probably the most possible without rolling the fenders or swapping out for wide-body versions. hmmm, there's a thought though...
Even with 9JJ it's possible to put on 275/40's, and that would be an additional advantage.

Hyper-X

Sorry Steve. What it basically means is that Curtis' Z is better balanced so he may need less to outperform us. His car is lighter to begin with, so he doesn't have to match our power hp to hp... but he has more torque also. His powerband isn't as peaky as ours.

A lighter car is always perferable than a heavier one... even though their power to weight ratios are the same because it's easier to stop a lighter car, and more forgiving to throw around due to less mass.

Curtis is using 255's, so I think we need to go bigger on ours. Your 275 idea is a good one, I was thinking 265s or 275's also. Keeping the front to rears staggered is a good idea. Even if the car oversteers a bit (being on the loose side), you can tune that out using a stiffer front sway bar.

Patrick Olsen

I see I was brought up in the first thread, but then the only person anyone is talking about is Curtis. WTH?? Strangely enough, I brought this subject up on another board a few months back. See the thread here: http://www.corner-carvers.com/forums...ad.php?t=17165 .

I have a 2 part plan to try to catch Curtis:

(1) Quaife front diff, higher spring rates in the rear to make the car rotate a bit better, possibly 225/45-15 Avon Tech Rs (after I try the 205/50-15 Kumho V710s in the garage), maybe lower the car another 1/2" or so if I can get the suspension to cooperate, and maybe try a quicker rack (STi?).

(2) Hope it rains.

I just got my replacement V710s, but won't have them mounted yet for the Test n Tune this weekend. The closest I've ever come to catching Curtis was the one event I ran on the first set of V710s (before they got recalled) - I was about 1/2sec behind him. I can't really say it was the tires, though, because Ken VanOrman was right behind me, so I think Curtis probably just had an "off" day. The V710s are supposed to be substantially grippier than the V700s I've been running, but they don't make a 225/50-15 V710 yet, so I'm stuck with the 205/50-15. Based on measurements I took they're about 7/10" narrower than the 225/50-15 Victoracers I've used for the past few years, so who knows which has more overall grip. The shorter V710s do give me a little bit more of a gearing advantage, plus they're a few pounds lighter (wheel/tire combo is about 28-1/2# at each corner), so..... I dunno.

I think I may just try the V710s for a couple events, then sell them to one of the Miata drivers so I can try the Avons. Very similar-looking to the V710s, in that they have just 2 grooves and no other tread. I've read mixed reports on sccaforums.com about how they compare to the V710s and Hoosiers, but I think it's safe to say they're grippier than the old Victoracers I run now. What I really like is that they make a 225/45-15, and the dimensions indicate that they'll fit OK on my car. (Even if they made a 225 V710, it might not fit - I only have about 3mm clearance between the rear tire and strut housing, a small enough gap that there's a clean spot on the struts from where the tires rub, and I rub on the fender lip under heavy cornering loads).

I'm not too sure about the Quaife diff. It would certainly help, but it's also about $1000-1200 + install. Ouch. I can certainly afford, it's more a question of whether I need to afford it, and I need to find someplace I would trust to install a front diff. If I do the front diff I may also upgrade to 4.44:1 final drive ratio (versus my current 4.11:1) which would help overcome the fact that I'm waaaay behind on power-to-weight ratio.

Hyper-X

Sorry about not including you Pat, but our goals is set to take out Curtis, not you.

To take out Curtis' car, we'll need more power and grip to overcome the weight differences alone. An ASP car IMHO is not capable of doing it easily since I'm limited to using the OEM final drive which severely limits my acceleration potential. His 5 way Tokico Illuminas are easy to tune (i've had a set before) and feels very nice for our track.

Grip wise, I'm thinking 265's in the rear is an absolute minimum, 275's being preferable. 245's in the front may be what we need, combined with a good adjustable front sway bar and shocks with good external damping control.

smccurry

We haven't forgotten you, Pat.
Naturally, by aiming for Curtis, we are also trying to beat you.
Actually, I see it as a race to beat Curtis, as you are closer to reaching that goal than we are. Not by a whole lot though. You are consistently beating me, but not by as much of a lead as Curtis is.
Right now he must feel the big 'bullseye' on his back. Then again, he's still so far ahead, he may not feel it at all.
We'll keep fighting the good fight, and I'm pretty sure his reign will not remain intact throughout the 2005 season
Let's see who gets there first!