You did your math wrong. If you want to figure out what the crank HP is from 268 WHP, it should look like so (based on your assumed 14% drivetrain loss):

268WHP/.86 = 311.63

Not a huge difference, but a difference.

 

Many people calculate differently. from 14% to 18%. FWIW, stock M3's & 911's (02' 996) were dynoing in the high 260's so I think 16% to 18% is a bit more realistic. From my calculations above that would have put the 03' & under S2000 right at 240 hp at the crank. Most 350Z's dyno at around the high 230's which if you calculate at 17%-18% comes out in the 286-290 range.

I absolutely agree with you that this car is not really 238 hp, but I would say it is closer to 220-228 hp.

A nicely tuned CZ will get you to almost high 190's-200 whp (from the dynos that we have seen), that would be right around the stated 238 hp. It's where the car should have been in the first place.

 

Is this 268 Tuned with a new map? or just with the bolt ons..

 

Thanks for the correction. I knew that felt a little off. Anyways, still a mod of the greddy kit that I would be happy to have in my car.

 

You are a very bright guy, you were at Racing beat... did you see the engine dyno for the 8? It was 208-212 period. That's it. I have no idea why people continue to think this engine makes any more power than that. Mazda did a great job with the drivetrain on this car. Anyways let me do the math with those numbers

lets be optomistic

182 (close to avg dyno for rx8) / 212 = ~86% or 14% loss

so

268 * 1.14 = 305.52 which is WAY more in line with what 7lbs of boost should be making over the stock 212.

I am not trying to insult Omi or anyone else, I am just asking the people here to get realistic. You bought a car with 212Hp at the crank... not 228 not 238. The engine dyno doesn't lie, Mazda does... emprically if you look at the evidence, there are very few companies that lie about HP numbers more than mazda. I do however believe that a well tuned 13B-MSP will make ~240 at the crank, just not hte way that mazda sells it to you.

I got realistic..............and i sold it.8 was an ok car but a 33k i payed for it and the 16 mpg i got hell no.Yes it handled well yes it looks nice but wasted money on a **** engine and tranny.They would have been better off dumping the rotary and putting that 2.5 turbo that the mazdaspeed 6 will have in the 8.

 

^^^wow, at least you're not bitter :D

 

Just we want in our engine bay a piston engine...not. The problem is not with the engine, it's with the tuning & engine management. Canzoomer has already shown us that a properly tuned Renesis engine is capable of putting out the claimed 238 hp. With a Greddy turbo kit this car is already putting out 240 to 275 whp (from 180 whp). Not bad, and not even turning the boost up yet. The SSR is getting even more hp (albeit for more $). But if a nice light car that can get to 300 whp with a turbo kit isn't enough (not to mention daily drivable), then the RX8 isn't for you. PS nothing wrong with the tranny. One of the best shifters on the planet, not to mention I am running the stock unit with 240 whp right now.

 

Where the hell did my reply go? I'm not writing all that again. It just went away.

Ok then I'll just give a clue. You can't figure % of driveline loss because it is not a constant loss. There is a loss to start with and then there is the friction loss which will go up with the power.

Added HP at the flywheel is subject to a lot less loss then the original power was.
You pay a base tax then a VAT so to speak.

Say a gain is shown on the engine dyno, give a value of X. A % value can be figured from this. Then put the engine in the car. You will find that the HP gain from the Dyno in real numbers is almost the same. Therefore % wise you gained more.

This is one of the reasons a good supercharger system can show more then the math says it will. Let me back up a second. I mean on the engine dyno you will see this. That is because you paid the original tax for all the accesorys the engine has such as the oil pump. water pump, etc. All the valvetrain losses will stay ery much the same. So the added air you provide give yoiu power without the tax the first air had to pay.

The turbo has to pay for the added resistance of getting the exhaust out and rejecting the extra heat. The supercharger pays the price of the added crankshaft drain. Nothing is free. But the best engineering from the start will give the best results. Everything is related and interconects and reacts. There no longer is easy power gains like your great grandpa had. He just added a carb to his flathead Ford and it went faster. Next week it was a cam of any kind and it went faster. Now everything is so tuned that you can loose power very easy from a change.

Not like it used to be even 40 years ago when the factorys had the right parts for you over the parts counter. Now you must be very carfull not buy snake oil. It is almost inconcivable how much money Rx8 owners will pay for 2 hp. Just because the were promised 20. If an aircleaner, engine oil or ground wires could add power don't you think the factorys know this and cars would come this way. Those items from the factory would cost them pennies. On top of that the items I just mentioned would also give the MPG. That is if they worked.

I'm not writing any more

 

Thank god you sold the car.

 

Yea kinda sad really being my 3rd rotary I had big plans for it.Look im a bit bitter with the bs hp numbers and i think mazda could have done alot better job with this car.Maybe the 7 will come back with some factory fi or at least something that will take a bit of boost and a tranny that would not snap every 15k.

As far as 4 door sedans go its not bad except for 15 mpg for 175 whp is kinda lame.I will say that the new z is a helluva lot more car.

5k in rx8=maybe 240whp
5k in a z=400whp
The novalty of the rotary only gos so far with me i guess.

 

Well thanks for the lopsided compliment. :D And I'm not insulted at all by your analysis. But problem is, I wasn't at RacingBeat and I didn't see the dyno they did. I would *guess* that the BHP was no more than 215, but didn't have that info conclusively, so I started my calculation using Mazda's BHP number.

I've actually been watching this thread just waiting for someone to take issue with that number as a basis. Thanks for speaking up. 15% driveline loss is much more realistic.

 

The 350Z is the Japanese Camaro. All engine, nothing else. The interior is garbage, and it is about 200+ lbs. heavier than the RX8. If all it is about is hp # then the 350Z looks like a pig when placed against the new Mustang or GTO. HP #'s are not the only things that matter, especially for the RX8 owner. If that was all that mattered to you than you are right to sell the RX8. Even in stock form compared to the S2K or 350Z performance wise the RX8 doesn't make sense. I wanted looks, handling, decent weight, usuable back seats, & didn't really care to make a 400-500 whp beast. If I get to the 275-300 whp, everyday car area I am more than happy.

Also your calculations are off. For $5K you can get the Greddy turbo (street price = $2900), labor, gauges, etc probably still have $ left over & get 240 whp. For $5K you can barely afford just the kit on the 350 Z (Greddy Twin Turbo = $5400+, Vortech SC, ATI Procharger, Stillen, etc are all at around $5K), if you include labor, gauges, etc. you are looking at (much) more than $5K and around 320 to 350 whp. At that price you are looking at the SSR/SFR kit for us getting to around 280-290 whp. Honestly we are not going to be the tops in the hp race, even the RX7 was not (compared to the Supra & 300 ZX). If all out hp is your #1 concern, go get a Mustang, or a EVO.

 

What is sad is that you are still here bitching about a car that you don't even own anymore.

 

Was no more banning someone else before?

 

Don't forget that with the Z...you might get the FI kit for 4k...but then you'll be buying a new bottom end in a few months...thats more then another 4k. I'd say to properly do FI in the Z, you've really gotta replace the rod bearings and rods...which means a bottom end buildup...so your looking more around 10k (Cause you might as well do everything while your down there).

The instances of Z's bending or breaking rods under FI are extremely well documented and rampant across the internet. It is an extremely poor platform for forced induction...just like the new 2005 GT Mustang. Would be better to pick another car if your looking to try and compare the 8 to something else...the 8 doesn't toothpick rods to bend . Heck even the mazda 6's bottom end is about twice as strong as the Z's.

 

Im not going to get into a pissing contest but get a clue here.The vq is not bulletproof supra but of all the fi's ive seen not one blown motor.

 

You haven't seen much then, as I belong to www.my350z.com as well. Haven't been back there much lately, but when the ATI Procharger came out they had several blown engines, & there have been a few on the Greddy twin turbo system documented on the board.

 

200 lbs heavier because it actually has some *** to it.Yea ll the camaros ive seen have carbon reinforced driveshafts.Pay an installer to put in a sc kit?Got a free saturday and a socket set?stillens 3500 320ish wheels.ati and vortech 370 to 390 whp for 4400 street.

 

Cause they buy ati tuner kits and dont know wtf they are doing.ati does not have one documented blown engine with the tuned package.

 

BTW someone buy these damn wheels from me.Least youll look good.

 

Let me reiterate what I said earlier.

 

The Stillen STAGE 1 is about $3700, has no IC & is about 300 whp, not 320 whp (claim is 354 hp at the crank, about low 300 whp). The Stage 2 & 3 will set you back $5000+. The ATI & Vortech are closer to $4800+. Your reaching here with all your #'s. The HKS Rotrex SC put out 325 whp (Turbo magazine test). Please show me a Vortech dyno that has put out 390 whp STOCK, no mods. That is about 470 hp at the engine. Even in their own marketing they were claiming 412 at the crank (about 360 whp). Not bad, but all your #'s are hype.

So if you get a free weekend to put in the Greddy, you are still looking at $2900 vs. $4000+ for the 350Z. If you argue you are only getting 240 whp for $5K, be consistent. If you are taking installation cost out for the SC & Turbo systems for the 350Z, then do it for the RX8. I can say 240 whp for $3000, not $5000.

BTW, In HKS test of the Rotrex with D Sport they said they could have gotten about another 100 hp with headers, exhaust, increased boost, but they said this was not feasible as it would need major engine strengthening (rods & piston swap).

 

Again that is incorrect. When the ATI Procharger kit first came out there were no tuner kits, they blew the engines because their stock FMU was bad. Later they tweaked them and the problems went away for the most part, but there were several people that blew their engines upfront with the ATI kit. They were not the tuner kit, because the reason they came out with the tuner kit was because people bitched & moaned because the ATI FMU was so **** poor they wanted to use their own & not pay for the FMU that came with the original kit.

 

http://www.everything350z.net/product/407350
Call em they will shave 100 bucks easy.Ive been quoted 4100 for the ati kit already.