Flybye

That's what some BS mazda tech or mag editor said when he was asked why they didn't turbo charge the 8.

Since when is exhaust temperature part of the equation needed to spin a turbo?

ExpensiveHobby22

I got some RX-8 sub-issue propaganda from Road and Track and it talked about forced induction being in development for the 8. They wouldn't say whether it would be super or turbo charged but they said it would be over 300hp. This was the Mazda people saying it.

Sounds good to me.

ShortBusRiot

exhaust temperature is part of the equation for the cats. Because the gas is actually close to being done burning by the time it leaves the block the temperatures are much lower. So low infact that if they had to take the time to go through a turbo they "in theory" would be to low to make the cats worth anything.

BigIslandSevens

iTrader: (4)

it won't be very reliable if it has a high comp.ratio like i've seen.(11:1or12:1) Can we say detonation!! Espeacially with our catpiss fuel!! Good luck with the 8 i'll stick with and take anyone in a SEVEN any day

rynberg

The guys at www.rotarynews.com had a sit down session with one of the Mazda Renesis engineers. The engineer said that the Renesis motor was BUILT to be turbo-charged....so who knows.

The word on the street is still that Mazda will stay N/A and enlarge the rotor chambers -- a "14A" will probably power the Mazdaspeed RX-8.

ZeroBanger

I'm routing or a 15B. Just skip the 14 like Mazda skipped the 11 going from the 10A to 12A.

911GT2

What'd I miss? Where does it say exhaust temps matter for a turbo? And too low?? Thats good, that means you don't need a huge *** intercooler.

My understanding of turbos is this: if it has an intake and exhaust manifold, it can be turbo'd. You just need someone to take the time to fab a turbo manifold and dp and intercooler piping. It should have nothing to do w/ exhaust temps.

ExpensiveHobby22

low exhaust temps = the cat not working = bad emissions

diablone

iTrader: (2)

Parked RX-8 was an RX-7, moving RX-8 was an RX-8.

rynberg

What the hell does cooling the intake air charge have to do with the exhaust gases? It's sounds like you are a bit confused.....the exhaust gases spin the turbine wheels which in turn spin the impellers (or compressor wheels if you like) which compress the intake air. The temp of the exhaust gas has little to do with the intake air temp.

As several people have pointed out, the lower exhaust temps make passing emissions extremely difficult, especially when the engine is cold -- Mazda already had trouble with this with the FD, which is why there is a pre-cat.

kyle@insight

I really don't see any reason as to why you'd want to put a renesis into an FD. Sure the reliability would be nice, but you really lose a lot, I just don't think it's an even trade off. A motorswap is supposed to benefit performance, not hinder it.

As someone else said, the motor is similiar to a honda motor in power delivery. It makes little torque and you need to rev the **** out of it produce any real power. This is simply not the case with Turbo 13Bs.

Someone asked besides the power and the cool effect, why else would you want a 20B in an FD as opposed to the renesis. My response is simply, what else is there? Upgraded performance is the reason you swap motors. These cars weren't meant to be day in day out drivers (even tho some do, no offense at all to any that do, You're VERY brave ). These cars are performance machines, if you wanted a daily driver for your commute to work then you picked the wrong car.

I just can't understand why you would want an NA rotary in an FD. To me, it just would be taking all the fun out of it. As someone else said, sure the car would probably lose 150lbs with the motor swap and all, but then you'd throw off the weight distribution by a pretty big number. The spring rates in the front would also be setup for more weight. So not only is acceleration compromised, but so may be handling. Thus you're taking away everything that an FD is.

The chassis in the RX-8 was built around the motor. It's a very capable chassis, capable of much more than an FD w/ the renesis. My opinion is that if you want renesis power, buy an RX-8. They aren't that expensive for a new car, especially when you compare it to the price you pay to maintain an FD.

rotary-tt

Rotaries have a higher exhaust temp than a boinger so I would guess that the Renesis maybe only lowers temps to "Boinger" temp levels. So a regular cat should work.

I would put a turbo Renesis into my FD. Many more years of engine deveopment, better oil\coolant sealing, better emissions. It will both top the REW on hp and torque with forced induction...

kyle@insight

The renesis may be stronger, but you'd basically just be better off using the renesis block. The rotors are a much higher compression which wont work well for just bolting on a turbo and going. Emissions is a pointless argument to make for a sports car, who cares honestly as long as you pass. As far as better oil and coolant sealing, they only thing that will prove that is the test of time.

Kaotic Dan

No it wouldn't be a simple bolt on... you would just have to use the rotors out of the REW motor you just pulled out for the swap ;-)

Maestro

Sounds like a load of S**t to me. And I work @ Mazda

Only thing the RX-8 might get would be. The new Wide Rotor Renesis. And that is aimed for the New Rx-7.

Oppppsss Did I say that ?

HeX

Yeah, that rumor has been around awhile. A wide Rotor Renesis with forced induction will definitly kick ***. I would have rather had three smaller Renesis Rotors as opposed to two larger ones. But hey, let's hope Mazda has it all figured out. I just pray to the Rotary gods the 4th gen RX-7 does not resemble the RX-8 one bit.

Kento

Negatory. He's not referring to "wide rotor Renesis with forced induction". What he's talking about is Mazda's development of a NA engine using wider rotors (same number, not less) for more displacement/surface area. More power, better throttle response, without the complications of emissions related to turbocharging the Renesis engine.

rynberg

Yep, the word on the street is that the Mazdaspeed RX-8 will use a "14A" or "15A", naturally aspirated.

And yes, the 4th gen 7, if it comes out, will look a lot like the RX-8. If you look at the 99 front end, you will see that the main air opening is shaped almost exactly like the RX-8's. I'm sure they will want to remain consistent within the new Mazda styling envelope (and reduce costs).

christi

If It was built to be turbocharged, then why didn't they do it? Is my question.....

christi

There was a 10A? I just thought it started (with rx-7s, not the cosmos, rx-3s etc) SA, FB, FC, FD...which the SA was a 12A? Maybe I'm wrong. Correct me though, if I am!

Mr. Wankel

I myself have started a whole thread devoted to the Renesis FD conversion, here was my reasoning:

What you do is you find an FD that already has a blown engine so you can get the body for a reasonable sum...not too difficult to find FD's with blown motors.

So now you've got an FD without an engine. Buying a whole new FD motor AND the turbos (chunks of apex seal destroy both) can be a tad expensive so...what about getting the Renesis motor instead?

The only way to make the Renesis and FD project worthwhile is to do an ULTRA LIGHT project car. Since the engine saves about 150 pounds you can then go about ripping a bunch of other **** off the car and possibly get it down to 2600 pounds or less. This will enhance cornering big time and would make a Renesis FD swap worth it if you were heavily into cornering...if not just go with a FD that has the turbo motor intact.

jimlab

Despite the denial raging on this and other forums, apparently the lesson was not lost on Mazda that a turbocharged rotary can be a warranty nightmare...

The goal of the game is not to have to repair a significant percentage of the cars you build before their warranty period runs out.

jimlab

It's mazing what you can find with a search on "history rotary engine" at Google...

http://www.mazda.com/history/rotary/n1-1.html

jimlab

Here's a thought... leave the interior alone, quit worrying about shaving another 50 lbs. and toss an LS1 and 6-speed in the car.

Oh, I see... you'd rather keep a rotary engine in the car at any cost, even if that means you have to listen to the vibration of sheet metal to get the weight down to where a Renesis would have a chance of making an FD fast.

On to another topic... just because an engine makes the same peak power as another engine, does not mean that they will accelerate the car in the same way. Comparing peak power to curb weight can be (and usually is) misleading.

The statement below is likely incorrect...
"Ok, with that said, my car weighs 2712 now, at under 2600, with 250 hp n/a this car will be faster than a stock RX-7, but yes You will have to rev more."

At 2,600 lbs. (vs ~2,800 lb. curb weight for a stock R1) a 250 hp Renesis will not be faster than the stock 255 hp 13B-REW in the R1. Why? Powerband. The turbocharged 13B will reach peak power more quickly and sustain power for a longer period (rpm range) of time.

When your powerband looks like a spike at the top of the rpm range, that's not a good thing. RPM is one way to post impressive peak numbers from a very small engine, but it's not ideal where performance is concerned. A car is more drivable and will accelerate faster over time with a broader powerband. Peak power is reached only once in the rpm range, and only for a very brief period. It's the rest of the powerband that we should all be concerned with.

I searched for a dyno chart for the Renesis to illustrate, but wasn't able to find one. If anyone knows the location of one, I'd appreciate it. Regardless, an engine doesn't remain at a constant rpm, so power to weight ratio is constantly changing. Therefore, comparing power to weight (unless you're going to average the results over the rpm range) is an effort in futility. You can't really compare two power to weight ratios, unless they're widely different, and say with any certainty that one car will be faster than another, all else being equal. 7.0:1 vs. 7.3:1 is far too close to call without knowing more about the engines. 7.0:1 vs. 11.4:1 isn't.

If you can, find a dyno chart for both cars (engine or rear wheel) and average the results. For another forum member's single turbo 13B, peak power is 612, but the average from 2,000 to 8,000 rpm is 338. That alone should tell you what the power curve looks like. By comparison, my engine (so far) has made a peak of 647 horsepower, but the average from 2,000-8,000 rpm is 466, almost 130 more than the rotary. Any guesses on what the power curve looks like?

In a 2,500 lb. car, do you think the rotary engine mentioned above would have an advantage over my engine in a 2,700 lb. car? Comparing peak power to weight, 2,500 / 612 is 4.1:1. 2,700 / 647 is only 4.2:1. Looks like the rotary has a small advantage by being in a car 200 lbs. lighter, right? However, that ratio only applies at peak power, which occurs only once on the rpm curve. Comparing average power to weight, 2,500 / 338 = 7.4:1 and 2,700 / 466 = 5.8:1. Still think the rotary has an advantage? Don't answer; it's a trick question.

Let's look at 4,000 rpm. His engine is making 175 horsepower, and mine is making 393. Power to weight? 2,500 / 175 = 14.3:1. 2,700 / 393 = 6.9:1. Which car is accelerating harder? How about 5,000 rpm? He's making 322, and I'm making 530. 2,500 / 322 = 7.8:1, and 2,700 / 530 = 5.1:1. Starting to get the picture?

Here's the difference in power...

2,000 rpm - 58 vs. 153 (+95)
2,500 rpm - 84 vs. 204 (+120)
3,000 rpm - 104 vs. 255 (+151)
3,500 rpm - 139 vs. 320 (+181)
4,000 rpm - 175 vs. 393 (+218)
4,500 rpm - 230 vs. 467 (+237)
5,000 rpm - 322 vs. 530 (+208)
5,500 rpm - 418 vs. 581 (+163)
6,000 rpm - 498 vs. 618 (+120)
6,500 rpm - 564 vs. 639 (+75)
7,000 rpm - 602 vs. 647 (+45)
7,500 rpm - 612 vs. 637 (+25)
8,000 rpm - 589 vs. 615 (+26)
Average - 338 vs. 466 (+128)

And here's the difference in power to weight...

2,000 rpm - 43.2:1 vs. 17.6:1
2,500 rpm - 29.8:1 vs. 13.2:1
3,000 rpm - 24.1:1 vs. 10.6:1
3,500 rpm - 18.0:1 vs. 8.4:1
4,000 rpm - 14.3:1 vs. 6.9:1
4,500 rpm - 10.9:1 vs. 5.8:1
5,000 rpm - 7.8:1 vs. 5.1:1
5,500 rpm - 6.0:1 vs. 4.6:1
6,000 rpm - 5.0:1 vs. 4.4:1
6,500 rpm - 4.4:1 vs. 4.2:1
7,000 rpm - 4.2:1 vs. 4.2:1
7,500 rpm - 4.1:1 vs. 4.2:1
8,000 rpm - 4.2:1 vs. 4.4:1

And finally, here's what the difference looks like for people who like pretty charts.



The point of this post was not to pick apart Zerobanger's assertion; far from it. The point of this post was to illustrate that you can't always accurately judge the performance of two cars based on a single point in the rpm curve, and even with average figures available, it's still not a sure thing. Driver skill is always a factor in any match-up, not to mention traction, and gearing, and the phase of the moon... and elevation. At 5,000 feet, my car wouldn't stand a chance against the rotary above. Naturally aspirated engines lose about 3% horsepower for every 1,000 feet of elevation.

Unfortunately, I see people comparing power to weight ratios in the Kills forum all too often and assuming that it's a foregone conclusion that the car with the lower ratio would be the victor, even when the difference is fairly close. Hopefully this post illustrates the vast difference in performance that can exist even when peak power to weight ratios are very similar or favor the lighter car slightly. Limiting the comparison to peak output fails to communicate the whole story.

BATHURSTFD3S03

damn great post gotta love the forum