Is the Mazda RX8 that bad?

JonnyGeee said:
I own an RX8.. i bet 90% of the people ****ging them off on here haven't even sat in one let alone drove one..
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The RX8 does some things quite well, but other things rather badly, the problem comes when you look at the car as a package, it simply has too many faults and shortcomings.

I personally think the RX8 looks good, the interior is ok for a jap car and its quite tidy to drive, other than that i wasn't bothered, the S2000 is a much better package in its market segment.

The main thing many like about the RX8 is it's price, yes the RX8 is cheap to buy, but it’s cheap for a reason, very few people want a compression failure prone underperforming high fuel consumption car, this is why it's worth 50p and this is why they take months and months to shift, it's nothing special, end of.
 
Its not underperforming though, some of the tradeoff is for the smooth engine and its free revving. You have to remember its only a 1.3 as well, what other NA 1.3 engines make 230bhp.
 
always liked the look of these, iv heard its had its fair share of problems but then its been reported that a lot of this is down to user error and general lack of maintenance. (which you could argue the car should be built a little better)

I cant believe how cheap they are! i understand why people are comparing it to a s2000 (which is a nice car) but then your forking out an extra £6K + for one of those!
 
robj20 said:
Its not underperforming though, some of the tradeoff is for the smooth engine and its free revving. You have to remember its only a 1.3 as well, what other NA 1.3 engines make 230bhp.
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Insurance companies will say 2.6. Anyways. What I disliked about the car was the lack of torque and fuel/oil consumption. Other than that it was great.

The next RX Mazda decides to make needs a turbo.

Wonder if we'll have this discussion next year!
 
iamtheoneneo said:
always liked the look of these, iv heard its had its fair share of problems but then its been reported that a lot of this is down to user error and general lack of maintenance.

I cant believe how cheap they are! i understand why people are comparing it to a s2000 (which is a nice car) but then your forking out an extra £6K + for one of those!
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Yeah imagine what happens when it comes to selling the S2000!

;)
 
Remember we're talking whole packages rob, so take the running costs and slush funds required for the Rx8 and you can have something which is better. Something Porsche perhaps...
 
robj20 said:
Not its a 1.3, just because insurance and tax decided to say it was a 2.6 doesnt make it so.
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Only if you want to compare apples and pears, might be worth a read....

http://www.rx7.com/techarticles_displacement.html

As rotary engine enthusiasts, we all know the obvious, intoxicating charms of Wankel wonder. Unique, unusual, lightweight, compact, high revving, what’s not to like? One of the most commonly deliberated subjects is “what is the rotary engine’s displacement”? An excellent question. Here’s our best to make the case for the engine’s displacement.

Conventional reciprocating engines are the standard that most relate to. We all know that these engines are measured by measuring the area of the bore, multiply by the stroke and then multiply by the number of cylinders. Simple as that.

For simplicity, we’ll use the 13B engine as the standard we’re calculating. You can use these ideas and apply them to a 12A or 20B yourself. The rotary engine is obviously unique. The engine has two rotors shaped roughly like a triangle. This makes for three combustion faces per rotor and a total of six for a standard two-rotor engine. Each face has a “swept volume” or displacement of 40ci(654cc) and there are a total of six faces. With this known, the engine displacement should be 40ci(654cc) times six to equal 240ci(3.9L), right? In a way, yes, but that would not be a comparable displacement to the 4-cycle engine.

The key for comparing the displacement between the 4-cycle engine and the rotary engine is in studying the degrees of rotation for a thermodynamic cycle to occur. For a 4-cycle engine to complete every thermodynamic cycle, the engine must rotate 720° or two complete revolutions of the crankshaft. The rotary engine is different. The engine rotor rotates at 1/3 the speed of the crankshaft. On two rotor engines, front and rear rotors are 180° offset from each other. Each rotation of the engine (360°) will bring two faces through the combustion cycle (the torque input to the eccentric shaft). This said, it takes 1080° or three complete revolutions of the crankshaft to complete the entire thermodynamic cycle. Obviously, we have a disparity. How can we get a relatable number to compare to a 4-stroke engine? The best way is to study 720° of rotation of the two-rotor engine. Every 360° of rotation, two faces of the engine complete a combustion cycle. 720° will have a total of four faces completing their cycle. 40ci(654cc) per face times four faces equals 160ci or 2.6L. That’s a well-reasoned number and now gives us something to be able to compare to other engines. In addition, since four faces passed by in the comparison, it’s like a four cylinder engine.

Now we know, the 13B compare well to a 2.6L 4-cylinder 4-cycle engine.
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Thats only a recent thing though, get an RX7 and you can even tax it as a 1.3, some insurance will still as well.

I dont want to compare it to anything, anyone saying its a 2.6 are the ones comparing it. Just because a rotary completes its cycle faster doesnt make the displacement suddenly change the fact is each rotor is about 650cc and in one revolution of the shaft it fires 2 rotors = 1300cc.

"The 13B is the most widely produced engine. It was the basis for all future Mazda Wankel engines, and was produced for over 30 years. The 13B has no relation to the 13A. Instead, it is a lengthened version of the 12A, having 80 mm (3.1 in) thick rotors. Each rotor had a displacement of 654 cc, for a total of 1308 cc displacement in the engine."

There currently working on a 1.6 version the 16X
 
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robj20 said:
Thats only a recent thing though, get an RX7 and you can even tax it as a 1.3, some insurance will still as well.

I dont want to compare it to anything, anyone saying its a 2.6 are the ones comparing it. Just because a rotary completes its cycle faster doesnt make the displacement suddenly change the fact is each rotor is about 650cc and in one revolution of the shaft it fires 2 rotors = 1300cc.

"The 13B is the most widely produced engine. It was the basis for all future Mazda Wankel engines, and was produced for over 30 years. The 13B has no relation to the 13A. Instead, it is a lengthened version of the 12A, having 80 mm (3.1 in) thick rotors. Each rotor had a displacement of 654 cc, for a total of 1308 cc displacement in the engine."

There currently working on a 1.6 version the 16X
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You asked which other 1.3ltr engines makes 250hp, due to the design and operation of the wankel you can't compare a rotary to a 1.3ltr piston engine, it’s not a fair comparison due to the number or rotor faces, chambers and rotations of the shaft needed to complete a cycle, whilst the displacement of the wankel engine is 1.3lts using conventional piston displacement measurements, in practice the wankel engine isn’t.

When you compare the RX8 engine to a 2.6ltr conventional engine the 250hp numbers suddenly don't look so great.

http://www.drivingsports.com/site/2008/12/rotary-vs-piston-engine-equivalency/

Conclusion
Rotary and piston engines can be precisely equated on some fronts, like volumetric displacement, but issues of thermodynamic and volumetric efficiency cloud any true formula for how many liters of displacement of one type of engine produces equivalent output to some displaced volume of the other type of engine. In other words, we can say a 1.3-liter rotary engine is factually the equivalent displacement to a 2.6-liter piston engine, but that does not make them necessarily equal in horsepower output or torque characteristics. This is why racing sanctioning bodies tend to either use oddball numbers for equivalency that have only superficial relation to volumetric equivalency (e.g. 1.7:1), or utilize some other means, like spec carburetor chokes, spec porting or alternate engine size, to level the actual performance, as typically done in SCCA. True equivalence is elusive, but volumetric equivalence is simple math: 2:1.
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Thankyou and goodnight ;)
 
its swept capacity is indeed 1.3L, no question about it, the calculator doesnt lie but id you look at how the rotary works, it actually does two "power strokes" per revolution so it burns its swept capacity twice per engine revolution

odd how they look at it that way, imo, because if you look at my Golf, its 1.8L swept capacity, but when its running i can put a BAR through it, in theory then its burning 3.6L of capacity...
 
Matt82 said:
its swept capacity is indeed 1.3L, no question about it, the calculator doesnt lie but id you look at how the rotary works, it actually does two "power strokes" per revolution so it burns its swept capacity twice per engine revolution

odd how they look at it that way, imo, because if you look at my Golf, its 1.8L swept capacity, but when its running i can put a BAR through it, in theory then its burning 3.6L of capacity...
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Assuming 100% VE then yes, this however won't be the case.

A rotary is more like a 2 stroke than a 4 stroke aswell.
 
Firestar_3x said:
You asked which other 1.3ltr engines makes 250hp, due to the design and operation of the wankel you can't compare a rotary to a 1.3ltr piston engine, it’s not a fair comparison due to the number or rotor faces, chambers and rotations of the shaft needed to complete a cycle, whilst the displacement of the wankel engine is 1.3lts using conventional piston displacement measurements, in practice the wankel engine isn’t.

When you compare the RX8 engine to a 2.6ltr conventional engine the 250hp numbers suddenly don't look so great.
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Well, I've just had mine dynoed and be wary of anyone stating they have 228bhp or above on stock engines as they'll be lying... having spoke to a lot of guys over the last couple of weeks, Mazda basically was talking out their arse with 228bhp... 210bhp a lot are saying was more realistic. In the USA Mazda said the RX8 would come with 250 when it came out in 2003, then Mazda back tracked and said 238 was more realistic... and in the UK we got 228... IN THEORY! It's the usual ******** figures firms come out with... there's not many cars that if you checked have what was stated in the manual :-) Also, as soon as mileage and age creeps in... you could be looking 10-20% reduction in power anyway due to wear and tear.

Also, depends what dyno you go on and especially on dyno dynamics and you need to select Shootout mode 2R for RX8's, anything else will give over inflated results. I had mine remapped on Tuesday finding another 20bhp... blue line is pre filter and remap... red obviously post remap. I've seen two other posts on forums using this same Dyno Dynamics equipment showing higher figures more like factory however they're been using a different mode... meaning it's calibrated in a completely different way...



You could take a car to 5 different dyno's and they'll all give different results... simples, any flywheel figure is based on calculations unless that engine is out of the car.

Check here for an interesting read. Anyhow, back to RX8's, yep after the remap the car 100% pulls better.. we all love big numbers, but hey tough luck for me, we can all fiddle numbers on a dyno and people been getting over inflated unrealistic results for years on dyno's due to idiots doing the runs, not setup correctly blah blah...for me it's how it drives on the track or road and mines flying at the moment... K&N panel filter, and remap and hey presto... just shy of 200bhp. Wanting either a super charger or Group B's port work done next year... will see.

Compression figures were:

Rotor 1: 7.5/7.6/7.7
Rotor 2: 8.0/7.9/7.9

Overall, for a car on 51k miles, they reckoned in top nick apart from the two engine mount dampers were on way out... nothing urgent or nasty, just need doing... apart from that, job done.Have to admit, falling in love with this car, was only meant to be a cheap temp runabout until the M5 comes, but now, looking like it could be a keeper for a while, just drives fantastic, looks great with it's ltd edition colour... and it's in body-shop getting some tasteful side skirts and front lip. Will post pictures when I get her back tomorrow.

Matt82 said:
its swept capacity is indeed 1.3L, no question about it, the calculator doesnt lie but id you look at how the rotary works, it actually does two "power strokes" per revolution so it burns its swept capacity twice per engine revolution
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Easier to post it than describe it for anyone thinking of buying one.

Wankel_Cycle_anim_en.gif

The best way to visualize the action of the engine in the animation at left is to look not at the rotor itself, but the cavity created between it and the housing. The Wankel engine is actually a variable-volume progressing-cavity system. Thus there are 3 cavities per housing, all repeating the same cycle. Note as well that points A and B on the rotor and e-shaft turn at different speeds - Point B circles 3 times as often as point A does, so that one full orbit of the rotor equates to 3 turns of the e-shaft.
As the rotor rotates and orbitally revolves, each side of the rotor is brought closer to and then away from the wall of the housing, compressing and expanding the combustion chamber like the strokes of a piston in a reciprocating engine. The power vector of the combustion stage goes through the center of the offset lobe.
While a four-stroke piston engine makes one combustion stroke per cylinder for every two rotations of the crankshaft (that is, one-half power stroke per crankshaft rotation per cylinder), each combustion chamber in the Wankel generates one combustion stroke per driveshaft rotation, i.e. one power stroke per rotor orbital revolution and three power strokes per rotor rotation. Thus, power output of a Wankel engine is generally higher than that of a four-stroke piston engine of similar engine displacement in a similar state of tune; and higher than that of a four-stroke piston engine of similar physical dimensions and weight.
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