Engine type

[Richyrichless]

I have a 2005 rx8. How can I tell which engine it has? Also the handbook says it's a 1300, but the DVLA tax her as a 2600...how does that work? Incidentally, she's the most enjoyable car I've ever driven.

[nightfire10]

5speed =192
1300 per rotor x2

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[bigpete8]

If she has six gears and revs to 9k + is a six port
If it has 5 gears and less rev range it's a four port.

Mazda tried to be economic with the truth and get cars into lower tax brackets claiming 1300.

[PaulAV]

There was a change to the taxation classes, I believe some rx8s, that are in lower tax bracket are taxed as a 1.3. they are all the same size regardless, but have different porting 4 port 192, or 6 port 231 usually coinciding with 5 speed or 6 speed gearbox respectively unless desired after manufacture

[warpc0il]

In the UK all RX8s should be recorded as 2.6 and only those whose V5 have not be replaced (for change of owner etc) will show 1.3.

This is regardless of the taxation class, which changes for pre & post 2006, just because that's when legislation changed.

However some JDM private imports may still be recorded as 1.3, depending how the paperwork was completed.

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[qwakers]

I am dismayed and astonished by the amount of mis-information here, on the owners club, no less.

I have been into this with both MSUK and Mazda technical in depth and the fact of the matter is this.

its 1300cc. 650cc per rotor x2. that is what Mazda technical say. they also say that they had a agreement with the DVLA to register it as 2600 for tax class reasons ONLY. this is the same for the 192, 231 and R3/series 2.


Motorsport UK state they accept the RX8 is a 1300cc engine and are happy to disregard the V5c in this case because they accept that it was for Taxation reasons only.

I had to go into this in depth as the scrutineers and club secretary of the motorsport club i am a member of wanted to put me in a cc class higher than i should be in.

cutting out the 10 of 15 emails to each, the pertinent (if oversimplified) reply's from MMUK and MSUK are as follows.

Subject: RE: Sprints, Hill Climbs and Drag Racing tech regs query.

The engine itself physically is a 1.3L engine, however as per the regulations the actual capacity when viewed from a motorsport perspective after the multiplier would become 1.95

Kind Regards,

Reece Tarren
Technical Support Engineer

msuk.jpg

T: +44 (0) 1753 765094

Good morning Mr xxxxx,

The only thing we could provide would be an extract from the workshop manual which shows the following:

MMUK.png

Which of course gives a capacity of 1308cc however; We do have an agreement with the DVLA that for all taxation purposes, the engine size is doubled to 2616cc.

Yours Sincerely
Emma Seal

Customer Relations Manager
Customer Service Division


Mazda Motors UK Limited

Victory Way, Crossways Business Park, Dartford, DA2 6DT
Phone: 03457 48 48 48
E-mail: mmukassistance@mazdaeur.com Web: www.mazda.co.uk



Mazda Motors UK Ltd is registered in England & Wales No: 4212655.
Registered Office: Victory Way, Crossways Business Park, Dartford, Kent DA2 6DT.

that aside...


the easiest way to tell if you have a 192 or a 231 is simply whether you have a 5 speed gearbox or a 6 speed.

the other easy way is the redline which is much higher on a 231 vs a 192.


here endeth the lesson or rx8 capacity.

[SprintRX8]

And to confuse you ever more.
The early RX4-7s where 2300 12A or 2600cc 13B.
RX8 13B Renesis is 1300cc which is basically the same engine as a RX7 13B.

RAC blue book (The Bible)
States Rotarys will be classed as 1 Rotor =3 Cylinders
2 Rotors =6 Cylinders.

[Richnzj]

RX8 13B Renesis is 1300cc which is basically the same engine as a RX7 13B.

Um these engines are not the same at all

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[Milos_Balunovic]

It is either 1300 or 3900 depending on the definition of displacement.
One complete combustion for each rotor which takes 1 revolution (same as 2t engines) and is 1300cc
One complete combustion of each rotor face which can be regarded as separate combustion chamber which take 3 revolutions and is 3900 cc....

2.6 is only taxation similarly for competition where 2T engines of 250cc are classed as 450 4t ones if im not mistaken now (in motorcross).. or if turboed 4t than it counts in class as 1.8* engine displ.

[SprintRX8]

RX8 13B Renesis is 1300cc which is basically the same engine as a RX7 13B.

Um these engines are not the same at all

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Basically the same internals which give the same CC.
You can swap Rotors Housings etc even the E Shaft and you’ll still end up with the same CC.


I believe they where dropped to a 1300 cc because of the Very high Tax classes in Japan from 2300/2600.

[warpc0il]

Taxation classes have very little to do with physics, rather they're determined by politics and revenue generation.

In the ROI our cars are taxed as 1.7L, which makes no physical sense.


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[Milos_Balunovic]

I believe they where dropped to a 1300 cc because of the Very high Tax classes in Japan from 2300/2600.

2.6 makes no sense what so ever. Only if we measure how much it displaces in 2 revolutions. Which is not a definition on any of the engine displacement measurement definitions. By that all the 2t would be calculated as twice what they are. Or anyy other non 4t engine's...

[Richnzj]

OK your blanket statement! un like the post before yours !did not answer his question about what rx8 engine he has! or the fact you don't answer the other question about tax in the UK! or the fact that you can build a 13b rx7 engine with 13b rx8 only parts you can't there a different engine ! but hey your right well done on your answer and yes 2 rotors = 6 compression strokes did you just add 00 to the end and make 2600 like the UK government and forget a triangle has 3 corners

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[Milos_Balunovic]

... ! but hey your right well done on your answer and yes 2 rotors = 6 compression strokes ....

Try reading the definition of the combustion volume. Might help ypu out instead of being a

[PaulAV]

Things get sightly complicated when you start using combustion area X crank shaft revolutions, the rotor revolution does not equal the eccentric shaft revolution, there is gearing involved, this is where the discrepancy/disagreement arises I believe

[Richnzj]

... ! but hey your right well done on your answer and yes 2 rotors = 6 compression strokes ....

Try reading the definition of the combustion volume. Might help ypu out instead of being a

OK my post is meant in a slap stick way no offence to any one

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[Milos_Balunovic]

Things get sightly complicated when you start using combustion area X crank shaft revolutions, the rotor revolution does not equal the eccentric shaft revolution, there is gearing involved, this is where the discrepancy/disagreement arises I believe

Engine displacement is the measure of the cylinder volume swept by all of the pistons of a piston engine, excluding the combustion chambers. (loosely quoted on Wiki from technical papers).

there is no mention of how many revolutions one of those complete cycles takes (2T engine vs 4T for example)

It can be discussible that:
-one rotor is considered one piston an its displacement is thus 2x 650cc. (completed in one revolution)
-each rotor face is considered a separate "piston" or combustion volume and is thus equal to 6x 650cc. (which takes 3 revolutions)

these are 2 physical options, there is no 3rd and that is used purely for states where tax or insurance is defined by displacement and not power and/or CO2 and that gives "equivalent" 4T volume... but having that as definition of engine displacement is a BS.... it should be stated that for wankel engines engine displacement should be doubled when calculating premium and tax...

[delta0]

I’ve always been under the impression the 2600CC is because it’s 1300CC but it fires on every rotation whereas a 4 stroke piston engine fires on every 2 rotations of the crank. It was the easiest way to convert the rotary engine to fit the way the tax system was intended to work at the time.