inittab

Paul Yaw of Yaw Power Products has apparently set his sights on the RX-8! All you 1st Gen RX-7 rotorheads out there know Paul Yaw for his wicked Nikki carbs. Check out this guy's web site, he's sharp and knows his $hit about Wankels. I can't wait to see what he comes up with!

--Bob

j9fd3s

www.k2rd.com is working on suspension bits for it too.
i hope paul yaw does well with the 8

mike

inittab

I guess Paul Yaw is pretty serious about the Renesis. Check this out, he's developing a supercharged Renesis engine for competition in the Speed World Challenge GT Class!

http://personal.riverusers.com/~yawpower/

He's go some interesting detailed pics of the Renesis on this page:
http://personal.riverusers.com/~yawpower/renespic.html

wakeech

hmm... notice the "log" collector style header on there??? that (i don't believe) is the stock unit... er, wait... the stock one wasn't cast, so that might be it...?? hmmm... in any case, i'm interested to see how Mr. Yaw designs his competition header to deal with the weird intermediate siamesed half-ports...

SPDFRK

Mr. Yaw was nice enough to compose a little article on the torque factor too. Maybe this can put it in simple enough terms for all the haters to understand.

http://personal.riverusers.com/~yawpower/tqvshp.html

Keech, your a technical guy would you be kind enough to calculate the 8's acceleration rate vs. the some other popular cars using his method (if you feel like doing homework tonight). I'm still at work and have wasted enough time reading the article.

Buger

Hi Spdfrk,

Mr. Yaw always writes great articles doesn't he? If you haven't visited him already, you should check out his shop in Phoenix.

Below is a quick calculation of the RX-8 acceleration in first gear @ the torque peak:

Assuming 20% loss through transmission, estimated rear wheel torque at 5500 rpms is:
1st - 3.760 * 4.444 = 16.7094 * 159 = 2656.80 * .8 = 2125.44 ft-lbs

force = rear wheel torque / distance from rear axle to ground (assuming the 18" wheels)
force = 2125.44 ft-lbs / 1.08'
force = 1968.0

Acceleration @ torque peak = force / mass

Mass = 3029 + 160 (assuming manual RX-8 w/ options that Mazda estimates 30% of us to buy) + (driver weight of 160)

Acceleration @ torque peak = 1968 / 3189
Acceleration @ torque peak = .62 g

I hope I didn't make any dumb mistakes there.

Of course the above calculation doesn't take aerodynamic drag, rolling resistance, etc into account.

Below is another RX-8 first gear accelerative forces graph from Cartest. Results are pretty close huh? We've done these silly graphs before however, what we need now is a real dyno result.

Brian

Good Duck

Brian, I'm glad to see you're back in your regular analytical form.

yawpower

Hey...That's pretty cool. Im happy to know that someone read the article.

Buger pointed out something that I left out of the article. The acceleration rate does not include frictional and aerodynamic drag. In my experience, 15% is fairly typical for driveline losses, and then there is tire rolling resistance. Frictional drag is linear so if you double your speed, the frictional drag will also double.

Aerodynamic drag is another story. Aero drag will increase with the square of the increase in road speed, so if you double the speed, the aero drag will quadruple.

The aero drag can be huge. For instance, at 100mph, my 74 Mazda rotary pickup has an aero drag of 100 horsepower, and that's with no tailgate!

So....The acceleration figures do not represent actual acceleration, BUT if you are making comparisons between two different motors, the percent difference in acceleration IS accurate.

Thanks again Buger (Brian)

I'm glad the article was put to good use.

PY

MrWigggles

I thought the amount of power needed was a factor of 8 not squared (i.e. 4) everytime speed was doubled. For instance if you were to go 200 mph in your 74 Mazda, you would need 800 Horsepower not 400 Horsepower.

-Mr. Wigggles

Buger

Hi again Good Duck,

You didn't like my owned pictures?

Brian

Buger

Hi Mr. Yaw,

Welcome to the forum. We are honored by your presence and I'm honored that you uttered my name! I am so unworthy.

Your articles are always very well written and easy to understand.

Brian

Good Duck

Actually, they were hillarious. My co-workers got quite a kick from that one with the two babies.

Vaillant

From what I understand, having no tailgate can actually create MORE drag, not less. It seems counterintuitive, but here's what happens. With the tailgate up, an air bubble (higher pressure area) forms in the bed. This causes the airflow from the top of the cab to flow over the bed minimizing the drag (base drag) caused by the flat backside of the cab. With the tailgate down, however, that air bubble disappears and you get a larger amount of drag due to the flat back side of the cab. There's a good reason why the trailing edge of wings are tapered!

Anyway, here's an article about it:
Click and Clack

What would make the truck even better is a tonneau cover.

But, anyway, I'm not trying to hijack this thread. I'm really excited about tuners coming up with new products for the RX-8. I wonder if the turbo or supercharger will reign supreme? :D

- Matt

wakeech

...like a two foot spoiler.

Mr. Yaw, it's a pleasure to be graced with your presence in this forum... i've got a zillion questions... *add to buddy list* hope you don't mind *PM'ing your inbox to full* answering *emails like crazy* a few of them??

juuuust kiddin' around. great to have another legitimately smart person on board (FYI, i'm not one of them, yet).

most sincere and respectful regards,
Andrew

ZoomZoomH

iTrader: (1)

and Mr Yaw, please keep us updated on the development status of the Speed GT RX-8!!! :D

yawpower

You guys are killing me! I appreciate the respectful tone but I'm a rotary geek just like the rest of you. Maybe someday I'll post an article describing all the bad ideas that I have applied to the rotary engine. Or maybe a short story describing the time that I spent all day fabricating a new collector for a GT-3 motor that was on the dyno, only to find that I lost 10 horsepower.

Then you will all refer to me as Paul Yaw, not Mr. Yaw.

Seriously though, thanks for the welcome.

PY

ZoomZoomH

iTrader: (1)

alrighty then, 'Paul'

yawpower

You and Buger are sure keeping me on my toes! The answer to the aero drag question is that we are both right. The aerodynamic drag will quadruple with a doubling of road speed, but since that force is being resisted at twice the speed, the power required to overcome it must also double. The result being 8 times the required horsepower.

That's where the time term in the definition of horsepower comes into play.

That brings me to another point. It seems that every automotive writer on the planet has bashed the RX-8 for having low torque. That has nothing to do with the acceleration rate of the RX-8. Note that most who have driven their new car are surprised at the amount of squirt the car has.

I read an article in a news paper the other day where the guy described it as having a "piddling" 159 lbs.-ft. of torque!

Someone should either grasp him firmly by the shoulders and pull his head out of his ***, OR tell him that he is no longer allowed to write about something that he does not understand.

I wonder how many sports car enthusiasts were turned off enough by these comments to consider buying another car.

Anyway.... that's all the adrenaline I have for today. I guess the rotary crowd will just have to live with these comments until the writers realize that cars come with built in torque multipliers, more commonly referred to as gears.

PY

wakeech

it's been a problem, right from the beginning...

anyhoo, about the car: why a supercharger?? is that the only option the series is letting you do?? what kind of supercharger is it?? Lysholm, or centrifugal, or roots...?? um, could i be so bold as to ask about a compressor map, just to get an idea??

i must say, i love the "de-techifying" of the whole system... using the pull-cable throttle (made of bits from various RX-7's), and a "more traditional" return-line fuel system, getting rid of all the crap you dont' need to run then engine... just brilliant.

...i've heard the rules are different for every car, and because you're obviously going to be the only wankel entry, the rules would obviously be different for you... god... i've got SO MANY questions... but i know you don't want to give away too much... maybe??

i'll ask anyways... what's the ruling on porting?? what about electronic government: will you be able to use something like a Haltec or MoTeC unit (although probably not in the budget for option 2 )?? do you have a target maximum rpm?? what about engine internals: will you be cutting your own e-shafts, and how much can you clearance the rotors, and what compression ratio are you thinking about?? i've heard (from The Man Boowanna) that the outer gears that are coming stock are good for well over 13k rpm or something, will you be running anything different??

hahaha... i'm sorry, i could go on for pages... anyways, yeah... i think i might turn out to be your biggest fan this season.

:D

yawpower

SCCA prefers a supercharger because it is easier to police. Not much easier in my opinion, but that is their position. We will be using a centrifugal unit. The roots has absolutely awful adiabatic efficiency, and the Lysholm is only marginally better. The centrifugal will not build boost right off idle like the positive displacement, but the efficiency is equal to any good turbocharger.

Motec will make the fly by wire system functional on the car, but for the sake of dyno testing, it is easier to use a cable. Now that the cable pull TB is built, we will always have it for dyno testing on any motor, so it is mostly a matter of convenience. Besides, the butterfly is so big that we would have to build some type of progressive linkage, or the throttle would be hard to modulate on the track.

Motec also has the ability to pulse width modulate a fuel pump for pressure control, but we will probably maintain the return style system for the race car.

No porting allowed. All the power must come from boost. Porting would cause some difficulties for SCCA tech. Let's say for instance that I port the motor, and reach the target horsepower with 12lbs of boost. SCCA would then specify 12psi in the vehicle technical specifications. If you then do a much better job of porting, and show up with the same 12psi, but 40 more horsepower, they have a problem.

Because they work hard to fit many different types of cars into the class, they have to limit performance variables.

We will probably run within the stock parameters unless we find that we need rpm to make power. I would not be at all worried about 10,000 rpm, and I suspect that the exhaust ports would start to limit us above that. Afterall, we do have to pass 2 atmospheres through the motor.

I never cut the shafts. I always get the clearance from the bearings.

We can do what we need to for reliability. The required side clearance should be less since the rotors are lighter.

We will run the stock 10:1 ratio. That's no problem for a boosted motor on race gas. It's pump gas that requires us to run low ratios.

As for the gears, I don't know what rpm they are capable of. They are obviously capable of running fairly high or Mazda would have a lower redline, but I don't think anyone can know exactly until someone runs them to failure.

Once the motor is done on the dyno, we will install it in an RX7 racecar that we have here, and abuse it on the track. We will do our best to break it so we can find the weak points.

Don't anyone be offended if I don't always reply to a post. I can only spend so much time staring at a computer before I get stir crazy, and I have been spending an awful lot of time doing that lately.

As things progress, we will post information to the website.

Thanks for your interest.

PY

mac

Hmm, just read a post in the discussion section where adamp316 had his 6spd dyno'd... 173.8 hp!!!! dyno result (scan not included)

I'm getting a little concerned. First it was a stuck tertiary port (copyright by wakeesh ), now a 30% loss in power. Ok the car has not been broken in completely but would that explain the significant missing hp.

sun stroke

This is a great thread! I wanted to get on here sooner!

Hello Paul!

I actually ran into Paul at our local Mazda dealer on Wednesday, we were both checking out the first delivery of the 8's in AZ. Car looks phenomenal and the motor is scary quiet.

anyway... I had a million questions as eveyone else does, and the subject of the wheels came up. I don't want Paul to be bombarded any more than he already is but they have considered designing an RX-8 specific wheel.

Since this is one of the first mods many people will do and it doesn't affect the warranty I thought eveyone might be interested.

I have to run I will post a bit more about my talk with "Mr. Yaw" when I get back online.

SPDFRK

If you go back to that thread now someone pointed out he has a automatic car. Which would reflect a 17.24% total loss which is right inline or better than most cars especially with autos.

P00Man

yeah but now he says he has a 6spd cause he was originally gunna get an auto but changed his mind at the last min so to speak...
________
Glass bongs

wakeech

...let's just leave all that in the other thread...

sounds great so far Paul...

(hahaha... i realized that i just wrote all this stuff, and forgot to ask this one first) have you had time to get a good base-line, and get the engine apart?? (if no, ignore most of this post )

now, about those stock ports: will you be utilising the tertiary ports, or will you use only four?? oh, and on that note, what're the port timing degrees like?? similar to the 13B with 32* ATDC open and 80* ABDC close, or is the cycle earlier?? those secondary ports look wickedly big, and have a funny shape to them: do you have any idea why, or how that would affect intake operation??

and the rotors, are the rule-makers saying anything about clipping the corners to change timing/introduce a minute amount of overlap?? i was just thinking that it might work into the clearancing...

how about manifolds?? the intake side is already pretty awesome: will you be incorperating some of the stock features (like the multi-runner system) into your supercharging system?? and how about the expiration side?? in the stock mounting location, will you be able to work around a multi (3?? 4??) runner, tuned length manifold?? how will you work around the weirdness of the siamesed intermediate out-hole?? what would be the benefit of staying with the collector-log manifold, other than the space issue??

speaking of mounting points, will you be keeping with the stock suspension mounting points and components??

...jeez, i should get off my "lunch" here and start a print job or something...

thanks a lot for your time Paul :D