GtoRx7.

iTrader: (12)

Wow, these charts are even better than I expected! Very exciting to see. Seth (shm21284) is a very skilled engineer so its nice to have his talent on tap for projects requiring this type of knowledge. Excellent job buddy I have to admit I was really a bit nervous to see the results going against the c6 z06 and F40. Real eye opener for sure.

GtoRx7.

iTrader: (12)

Haha, Seth is a mystery motor science guy! He has been a best friend for many many years. Gordon now that Seth has all the formulas, he can enter any car and pit it against another. All we need are dyno charts of the cars Oh yeah, the GT3 is 375rwhp, its dyno chart is plotted out on the last graph for easy reference.

t-von

iTrader: (8)

If I'm reading the charts correctly, it would appear that the 20b is maintaining a higher more consistent levels of acceleration for a longer period of time? With the other cars, it seems they are loosing trust after each gear change, not so with he 20b. The funny thing is, those numbers would look even better with a closer ratio Rx8 style 6 speed.

t-von

iTrader: (8)

Would you mind doing another chart at near stock weight? This would give us a better indication of how a more street version of Logan's set-up would perform against those same vehicles.

BLUE TII

iTrader: (9)

Thank you so much Seth!

All this "torque" talk is just that- talk.

Gears for the win!

Would you share your charts so we can all input our various cars and or dream cars?

Or make this awesome tool available to us by some other means?

shm21284

Thanks, guys.

Looks like a transposed the colors on the last graph for the Ferrari and the Corvette.

It should be noted that the aerodynamic information that we can find is not as accurate at higher vehicle speeds due to increased pressure drag from higher amounts of turbulent separation in the wake of the vehicle. Cd is really a function of velocity rather than simply a set value.

BLUE TII

iTrader: (9)

I guess we have to keep in mind that the charts do not take into account limit of traction at the tires nor the effect of wheel/tire/driveline mass/inertia on rate of acceleration.

That would really even out the low speed 1st gear acceleration between cars of similar traction levels (note- Porshe has rear weight bias as an advantage).

The rotating inertia is going to be related directly to the traction issue- if you try to go skinny on wheel/tires for less inertia to accelerate your lower speed/gear acceleration will suffer from lack of traction. This could be a chart unto itself.

shm21284

Logan's car has the sharpest drop in acceleration due to a gear change (causing the stair-step looking curve on the first and second graphs). This is because his torque curve peaks much higher in his usable torque range than the other cars. (i.e. his peaks at 90% red line and the corvette 50%).

shm21284

A simple fix to the inertia (as well as driveline "aerodynamics" problems) would be to have a dyno graph for each car in each gear. Problem is, I don't personally know anyone with an F40.

shm21284

I just took the weight of an R1 out of my Rx-7 book by Jack K. Yamaguchi as 2,800 lbs and added 170 for the driver (consistent with what we have done for the others). Looks like the Ferrari now wins, the Porsche still loses, and the Corvette puts up a fight, but probably in vain.

Fritz Flynn

iTrader: (263)

Great example of why loosing weight is so important. Even if it's just 100lbs it will make a tremendous difference at speed over a given lap as you accelerate, brake and corner many times in that one lap. It will start to add up to a lot of gained time.

Strip that vette down to 2800lbs or the even the GT3 and look out.

shm21284

Note that weight does contribute less at higher speeds due to the increasing effect of aerodynamic drag (drag force is proportional to the square of velocity)

gnx7

iTrader: (10)

very cool build! Love all the innovative thinking....

10,000RPM redline.... love it!

Narfle

iTrader: (16)

A car's weight affects it's acceleration equally at any velocity in any direction. Drag happens to be a much larger force in resistance to forward motion. But, that doesn't diminish the effects of weight.

It should be mentioned driveline weight also has an exponential effect on centripetal acceleration at higher velocities/engine speeds. Double bonus.

Insane Driver

iTrader: (2)

Sick ride!!!! Why did you keep the stock bumper? Wouldn't you have some heat issues with it being a track car?

GtoRx7.

iTrader: (12)

I have a feeling the g-force dogbox has better ratios than the Rx-8, if only we had a way to plug in the Rx8 transmission to my vehicle and see the comparison....... OH WAIT! WE DO! I will have Mr. Science aka Seth do that for us soon!

I think we will do a plot of all vehicles running identical weight to mine. Just for fun to compare engine performance directly. Should be interesting.

Thank you very much! Think you can donate two of your LS7 pistons so I can have 575rwhp too?? Would that make a 20B7 or a Ls20? BS 207?

Thanks A few reasons- 1) It was free 2) I wanted to see if I could accomplish a race look with race function while staying factory. 3) Its a hunch but I think it provides less drag than aftermarket "large" openings, with a better inlet/ exit ratio.

So far its amazing for cooling. I can sustain hard 10k rpm use for a while and not budge the temps past 190 degrees. But more testing in 95+ degree weather will prove for sure!

shm21284

What year Rx-8? '04 or '09? The ratios (according to rx8club.com) are:

Car (1st 2nd 3rd 4th 5th 6th FD)
04-'08' RX-8 (3.760 - 2.269 - 1.645 - 1.187 - 1.000 - 0.843 - 4.440)
09' RX-8 R3 (3.815 - 2.260 - 1.640 - 1.177 - 1.000 - 0.832 - 4.770)

Honestly, I could do both, but is there a preference?

GtoRx7.

iTrader: (12)

Lets do option 1, the 2004

shm21284

That's right. I have been accused of making the same argument; that is, I argue that weight's effects don't change but aerodynamics do (as a function of speed). I suppose it depends on which side of the coin you are looking at. On one hand, aero becomes a much larger percentage of resistance to acceleration as velocity increases, but on the other hand, mass retains the same numerical value of resistance.

shm21284

Logan's FD with Rx-8 Transmission ratios. Not sure the Rx-8 Trans would withstand the torque that the T-5 would, but here's the theoretical results.

TERVO

A TRUE BEAST MAN! LOVE IT!!!...GREAT JOB!!!....

GtoRx7.

iTrader: (12)

Thanks, nice sig picture! So to sum up the technical graphs, I think its obvious here that when done properly, a small naturally aspirated 20b can put some of the BEST factory powerplants through their paces and win.

shm21284

Here is the final comparison. It compares the following final drives on Logan's 20B FD:

1) 4.10
2) 4.33
3) 4.77

GtoRx7.

iTrader: (12)

I had a lot of requests to post more pics of the sheet metal intake manifold, but I lost the pics. Recently was able to find the old memory card, so here it is. This setup uses a 90mm throttle body. All the port entrances are fully venturied for optimal flow. We manufacture and sell this part for anyone interested. Its a half-way step between the stock intake and Gordons fully custom tapered runner design.

Price is $1100.00

Trots*88TII-AE*

iTrader: (11)

My mind just exploded. Nice to see all your info in one thread. This is officially my dream track-car! Maybe a little nitrous for the streets for that angry barbaric power lust though...

I'm surprised you haven't tried port-phased rotors yet, I thought those were CLR's specialty? Surely that can gain you something without affecting idle/drivability too much, it does seem like you've found the mechanical limit for your current setup minus the variable length intake runners you mentioned. Either that or adding bridge ports, I know some drag racers on the giggly gas were fond of that setup, low end will suffer though.

You mentioned trying to eliminate the air gap between the semi-pp TB and port opening. This has been on my mind for a long time, as I'd like to someday build a semi-pp 13B with staged throttle. The only things I could come up with are a slide throttle body setup nearer the port face, or some reed valves. Although I'm not sure I'd be comfortable having some delicate reeds sitting near the port face waiting to be ingested! Any hints you wanna share?