RX8

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The Brummie

Original Poster:

7,780 posts

132 months

Friday 16th August
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Currently scouting round for a replacement for my slightly knackered E46 BMW.

I have looked a couple of RX8’s however I don’t know what potential trouble spots I should look out for with the engine.

How complex is it compared to a normal engine & what, if anything, needs to be done on a regular basis to ensure that the engine doesn’t break.

Stupid question i know however I need to know what I should look out for.


Thank you.

Dave.

5,546 posts

198 months

Friday 16th August
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Buy one with a blown engine and take it to a specialist for a warrantied rebuild.

Or buy one from a specialist with a warrantied rebuild.

ETA - https://m.youtube.com/playlist?list=PLzleYhq4aqPvI...


The Brummie

Original Poster:

7,780 posts

132 months

Friday 16th August
quotequote all
Watched the video but it doesn’t give me too much info as to what I should be wary of.

Low compression was mentioned - how do i check this & how do i know if the car is ok or knackered?

What are ‘cold start issues?’

What different maintenance is required day to day?

I’m guessing that buying an RX8 privately is probably not the best thing to do.




Gary C

5,259 posts

124 months

Friday 16th August
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Get the latest you can afford. An R3 has the most reliable engine with a better map for the oil injection.

Look out for a bottle of delexia oil secreted in the boot as thats an indication the owner keeps it topped up (it doesnt use as much as people think though)

Start it, go for a run and get it hot. Stop the engine, then attempt to restart after a minute and note if it has any problem

If it does, its not the end of the world and could be coil packs rather than the tip seals.

The only real way would be to get a compression map test from a dealer with the correct equipment (not a normal compression tester) and check both rotors give more than 7.5 for each three chambers per rotor adjusted to 250rpm
(see https://www.rx8club.com/series-i-tech-garage-22/co... or buy on condition of body and get a rebuild engine (probably best for a long term prospect)

If you get a rebuild, go for standard 231 and get a SOHN adapter, then you can run proper oil in the case to oil the bearing, and inject ashless oil into the combustion chamber rather than run the Mazda compromise oil.

BTW, they are fun smile but I sold mine because it was ruinously thirsty. Was drinking a gallon every trip to work and back and I only live 7 miles away !

If you take one for a run and the red coolant warning lamp comes on, dont worry, its a common fault with the sensor in the expansion tank.

231's have gas discharge lamps and have level sensors attached to the suspension, these can fail and its a MOT failure if the aim of the headlights goes out (actually prefer the standard lights myself as they dont have such a severe beam cut off)

The LSD can break off the tabs and become ineffective so give it a little throttle with one wheel on gravel wink (the traction control will cut in, but you can feel it start to spin if its broken)

err, what else

They are great cars, and I would still have mine if it wasnt for MPG (as a daily it was just too much and the 911 in the garage meant I couldn't keep it).

Gary C

5,259 posts

124 months

Friday 16th August
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The Brummie said:
What are ‘cold start issues?’
Because the engine is a spinning Dorito in a case, the 'pistion rings' are actually seals along the thickness of the tips of the 'triangle'

These are spring backed to slide out as the engine warms and the casing expands slightly to maintain contact with the walls of the casing. When these tips wear down, they dont seal as well, more so when the engine is hot.
As such, the engine becomes harder to start when hot.

They seal better once the engine is spinning and the tip seals are also pushed out by centripetal force, so once running they are normally fine, but fail to restart when shut down hot (such as stopping to fill up).

To lubricate the tip seals, oil is injected into the engine along with the fuel and air (like an old 2 stroke engine). This oil needs to be specifically designed not to leave deposits in the engine which can increase the wear of the tip seals. Unfortunaley this oil isnt as good as modern oils at lubricating the 'crankshaft' bearings. Rotary engines used in aircraft don't use the same oil for both and have a separate tank to contain the oil to supply the oil injection metering pumps (look up SOHN adapter)



Edited by Gary C on Friday 16th August 13:37

Rotary Potato

27 posts

41 months

Thursday 22nd August
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In general there are 2 ways of doing this.

Buy cheap - keep your fingers crossed and be prepared to either rebuild the engine or to break the car for spares.

Buy expensive - recent rebuild from a reputable specialist, still in warranty, etc.

Either will cost you about the same to get to owning a decent RX8 with a solid engine (about £3-4k for an S1)

Either way, the first thing to check is the condition of the body (I know everyone screams about the engine, but these are a known commodity that can be rebuilt by a specialist for a fixed cost - so you can account for the risk). The RX8s rust for fun. Front wings and sills are where you're most likely to notice it from above ground level, but stick your head underneath and it's likely to look like the Titanic down there.

Then you've got a decision on whether you want an S1 (2004-2008ish) or an R3 (2009ish onwards).

They only made 800 R3s, so they're rarer, and they're newer. The exterior looks are personal taste (I actually prefer the look of the S1, but I appear to be in a minority), but the interior did get some nice upgrades (the seats sell for £800 on their own in half decent nick).They got an extra oil injector, and a few subtle mechanical changes, so in theory are more reliable than the S1 engine. In practice, there are thousands of S1s, and they're older, but only 800 R3s and they're newer ... so naturally you hear of a lot more S1 engine failures and a lot fewer R3s. Personally I don't think the R3 engine is night and day more reliable than the S1, but I'm sure you can find plenty of people (including a lot of R3 owners! smile ) who'd say otherwise. The R3 also came with upgraded suspension compared to the S1 (roughly comparable to the suspension on the PZ special edition S1).

In terms of S1s, there are 2 main options. 231 and 192. These stand for the horsepower outputs of each engine, but it seems Mazda's horses were very optimistic, and neither made the power quoted. In simple terms, the 231 revs to 9k (and has a rev counter that goes up to 10k) and the 192 doesn't. The 231 also got a load of extras (6 speed gearbox, upgraded headlights with washer system, leather interior, electric seats, metal pedals) some of which could be optioned in by 192 owners when new. Personally, as there's no difference in tax levels, reliability, or anything like that between the engines, why have less power, less revs and less equipment? Others say that the extra low down torque of a 192 mean that on the road it's just as fast as a 231 (I've not driven a 192, so can't comment).

If you choose an S1, you then have the elephant in the room ... tax! Pre-mid-March 2006 cars (in general anything up to and including a 55-plate ... but there are a couple of exceptions) pay about £300 a year in tax, after that and it's £600 a year. Up to you how much that impacts your decision, but my steer is that buying the wrong RX8 will cost you a lot more than the £300 difference in tax brackets, so don't have it as a deal breaker. If you choose an R3, you're straight into the high tax bracket, so no decision to make.

You then have a handful of special edition S1 models (Nemesis, Kuro, PZ, 40th Anniversary, etc.). Some of these were cosmetic exercises with exclusive interior/exterior colours, whereas others were more substantial, with suspension upgrades. Plenty of info online about what came with what.

If I were buying another (after 2 of them, both of which burnt my fingers, I've learnt a lesson and moved on to a Porsche Boxster), I'd ignore the R3 (too rich for my blood) and stick to the S1. I'd then completely ignore the engine, and buy the best shell I could find (as long as it was priced appropriately for whatever the condition of the engine was - sub £1k for an unknown, running engine ... up to about £4k for a recently rebuilt one with decent paperwork to prove), then slather the underside in a decent rust preventer and go from there.

vernz

179 posts

75 months

Thursday 22nd August
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Just coming back a bit from all the excellent and extensive technical responses you have received.

I came out of a company car scheme and leased a brand new one is 2006. I tried both models back to back and felt the 192 was probably a bit more drivable, with the extra bit of torque sometimes making up for the reduced BHP, in much the same way that torque and not BHP is often what gives you the sensation of performance.

That said, given the choice and for your usage, I'd probably now go for the 231, just for the fun factor and all the extra's.

I did have a workmate that had a 231 and he got noticeably worst fuel consumption than me and as it was effectively a company car, I did 20k miles a year for the three years and typically averaged late 20's during visits and a 20 mile (each way) commute.

I had one client that was a straight drive up the M1 and if I stuck at 70 all the way, I could achieve 32 - 34 MPG.

I gave the car back three years later with 60k miles on it and in all that time had no issues or warranty claims, which tells you something about the car.

The wheel quality was poor and I suspect most owners referb fairly early in the life span, but otherwise all was good.

Of course we all know they like a bit of oil, but I generally topped mine up every other week and from memory got through about about 25 litres of oil in total for the 60k miles.

I did Le Mans in 2008 and covered about 1000 miles there and back without needing to top the oil up and checked it at the campsite and it at hardly changed, so I suspect at normal motorway speeds they use a lot less oil than when you are banging into the limiter

I only managed to cold start stall the car once...totally my fault as I turned it off too quickly, but generally I found if I give it a couple of minutes to clear it's throat, I had no issues then re-starting it.

delta0

1,191 posts

51 months

Friday 23rd August
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Make sure you check out the RX8 owners club. A huge amount of info there and if there are any cars you are interested in we can give some opinions and things to look out for.

captain_tripping

38 posts

3 months

Friday 23rd August
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I'd say these cars are more for a hobbyist rather than someone after a reliable daily.

Most technical points have been mentioned. Rust will be your biggest nightmare, get a good body. It is worth budgeting for an engine rebuild at some point, unless it has recently had one (but then it will be a more expensive car initially).

Someone may need to correct me on this, but it would be worth buying from an enthusiast rather than "one careful lady owner from new". When idling at factory idle which happens a lot when doing small trips and driving around, the oil pressure is not enough to evenly distribute oil along the apex seals, causing uneven wear and accelerating the need for a rebuild. These engines need to be pushed every now and again to clear up carbon deposits... I know in the first gen rx7 manual it says to redline it occasionally.

Decent cooling and premixing is the key to these. If you are in to modding cars, cooling is the first thing to address.

Gary C

5,259 posts

124 months

Friday 23rd August
quotequote all
captain_tripping said:
I'd say these cars are more for a hobbyist rather than someone after a reliable daily.

Most technical points have been mentioned. Rust will be your biggest nightmare, get a good body. It is worth budgeting for an engine rebuild at some point, unless it has recently had one (but then it will be a more expensive car initially).

Someone may need to correct me on this, but it would be worth buying from an enthusiast rather than "one careful lady owner from new". When idling at factory idle which happens a lot when doing small trips and driving around, the oil pressure is not enough to evenly distribute oil along the apex seals, causing uneven wear and accelerating the need for a rebuild. These engines need to be pushed every now and again to clear up carbon deposits... I know in the first gen rx7 manual it says to redline it occasionally.

Decent cooling and premixing is the key to these. If you are in to modding cars, cooling is the first thing to address.
Certainly a good thrash is worth it, but I would not bother with premix, get a SOHN instead.

Also, I never understood the 'lack of torque' argument some made, who cares, thrash it !

Torque is for people who cant drive.