Axle upgrade necessary for road racing? FD3S 4 rotor
 

Hey guys,

4 rotor build currently underway. 1.5 way carbonetic differential installed and trying to decide whether to bite the bullet and spend the money on axles or if they will be unnecessary for the goals.

Car will be making 750-1200rwhp, increasing upwards over time as driver mod gets used to the power and trans is upgraded soon after start up.

The car will not, under any circumstances, be launched. I have no desire, ever, to drag race, or dump the clutch. I'm a 2nd/3rd/4th stomper.

On the last setup, never had an issue, with stock diff and axles on r compounds with 650rwhp 20b.

Will stock axles handle the power so long as there is no torque shock/launching?

I think you'll be ok as long as you aren't launching. I don't see how you will be using a full 1000 WHP off a corner anyway.

I think it will be ok. Just run it and see before spending more money .

I ran a stock set up with 355 slicks for years with no problems on a roadcourse. What happens eventually is the cv joint itself will develop stress cracks around the shaft and fail . If you break axles without a launch you will probably be doing a full 8.8 swap with bigger Porsche cv 's/ dss axles.

Thank you for the insight, I will definitely see how things works first. Those driveshaft shop axles are inssnely pricey!

Stay away from the curbs.

... on the throttle and under power!

Eric

In what class could you possibly use 1200 HP in road racing? Even an FD will never be able to put that to the ground without massive aero.

FWIW, road racing does involve drag starts occasionally.

I guess you actually mean time attack?

Valkyrie In what class could you possibly use 1200 HP in road racing? Even an FD will never be able to put that to the ground without massive aero.

*shrug* La Sarthe used to have a 3.7 mile straight each lap, but I guess those days are gone.

Nurburgring still has a 12 mile straight I think and they let anyone on that track.

But yeah, I guess this could be race car that would be fun on the freeway as well and help defend the rotary reputation against junkyard turbo LS set-ups.

I guess I should clarify,

Motivations behind the build are both personal, but also investment/value potential.

The boost can be turned down, and the car can be driven at more reasonable power levels for those that are serious about tracking. When there are comparable price range vehicles in the world, now making 1200+rwhp, it needs to have the that potential to draw in those outlier buyers.

As far as Aero, widebody currently underway, RE wing for downforce and front splitter/canard setup, along with aluminum undertrays

There's nothing reasonable or sensible about any of this and that's the point.


So,

quite simply, if the axles will hold the power for a few videos on a straight away, be it TX2K while it smokes a 1000rwhp GTR or Supra, or an interstate run against a Ford GT, that's the goal.

I suggest getting some advanced traction control/boost control/turbo speed sensors as well as drive by wire.

Turbo p-ports have an "interesting" power-band and throttling control.

Your power will be related to turbo shaft speed and engine rpm mainly and not throttle position as we are accustomed to controlling power output.

Or, what I would do is make a side intake port turbo 4 rotor by using street ported 13B-RE Cosmo intermediate housings and RB aluminum rear and front side housings with the ports machined to 13B-RE spec (or JB welded ported 13B-RE housings flowmatched to the intermediates).

If you want more aggressive porting you can add semi-peripheral porting.

The advantage (with a turbo) is that at some point side ports and semi-p ports are physically blocked by the rotor.

A full P-port is always open, just switching flows between intake, exhaust, exhaust & intake and back to intake.
This means the only thing ever impeding intake flow (and thus creating boost) is dynamic engine principles and the physical limits of the compressor; thus the unpredictable power-band and throttling control.

that is a good way to describe it. mine is NA, but once the throttle is more than 50% open, it feels like the only real parameters to power are rpm, and the intake/exhaust tuning. the ignition timing and AFR's don't seem to matter much at all.

And you have an unlimited supply of 14.7psi air pressure and fixed exhaust geometry!

Now add in a turbo surgeline, exhaust manifold burn accelerating the turbo shaft, exhaust manifold pressure choking the engine VE and finally the turbo choke line all conspiring to make throttle input a vagarity.

Well, you'll find out real quick...lol

I don't think any wing smaller than about this big would be enough....

http://www.singularmotorsports.com/w...uzukiS15-1.jpg

lol

LOL that's a fighter jet!

I didn't realize it could be this severe,

It may not be too late to have the construction changed to side-ports, its just a lot more expensive/more work for intake manifold design. We are doing a water-to-air core incorporated into the UIM.

So driving this vs a turbo 20b,

I'm assuming, say you're on the interstate at 3.5K rpm, cruising. Wastegate set for 8psi, say around 600hp. Roll into it 50% throttle, car starts to slightly accelerate with a few psi of boost, but once it hits 5-6k rpm its as if you went full throttle even though you haven't? Like acceleration is unpredictable so long as the throttle plate is cracked open? That does sound dangerous.

Yeah, and it only has about 900 HP... You could go with someone smaller if you weren't trying to actually set lap times, I imagine.

size of wing =/= low lap time...

we've run aero here and there, its very difficult to actually quantify what its doing, although chicks dig it. we had an E46 BMW for a season and it had a HUGE wing on it, and everyone thought it was SoooooOOOOooooo fast, but it was a 325i, so it was 155hp and like 3800lbs, so it was a slug. terrible car, the E46 like a danish cookie tin with windows 8...

My point was more about how hard the car would be to drive fast with 1500 bhp... not lap times.

Wait Wait Wait Wait Wait Wait ....... p ports. cruising? :lol:

Blue TII hinted at you having a turbo p port 4 rotor, to make 1200hp..

is that the engine you are building, you think it will cruise?
i'm building some home made p port, because i was told they can be made streetable, but i have also been told they will not cruise at steady state speed, you are always accelerating or not.
same for bridgeports.

define streetable.

good point!

The trick is to get the engine loaded down enough to run smoothly.

I don't think a 3 or 4 rotor can be loaded down enough. A 2 rotor barely can.

NSUs were all peripheral port. The first one was a one rotor. The Ro80 was a small two rotor (10A sized IIRC) in a heavy car, with an automatic transmission so the torque converter helped smoothness a lot.

For reference, my full bridge 13B cruising at ~3500 was about 75mph. With the car packed full of tires and spare parts (removed passenger seat so I could get the spare trans and diff in there!), 50% throttle was enough to accelerate past trucks going up some of the steeper hills along I-44 in Missouri. Not downshifting.

That's a two rotor. No forced induction.

Do not underestimate the ability for a high overlap engine to make ridiculous amounts of mid range torque.

yeap same with above. 13bbp vs 13bpp the pp makes more tourqe everywhere. interesting enough with latest one I have done with rx8 internals(rotors slotted to run conventional seals) it's more streetable even then a bridge. it quite happily cruises at our suburban speed limits of 50km/hr with no throttle modulation. I was blown away had to keep checking what gear I was in lol