Kinbote

Hey, first post.

I've read enough of this forum to know what I'm inviting with this topic, but let me explain...

A couple of weeks ago I bought a 2006 RX8 6AT (unfortunately; another driver in the house insisted on automatic). Had the compression test done first and all was good.

Then yesterday I finally had some spare time, so I decided to take both the RX8 and my old car out to some B roads to test the 0-100km/h time.

Found the flattest piece of road I could (although it goes slightly downhill and then slightly uphill) and let them have it. First was my 2003 Nissan Teana, which is about 1540kg, has a 2.3l V6 developing 173hp and a 4 speed auto gearbox. On paper it's meant to do 0-100 in ~10.7 seconds, and I did my stretch in ~9.8.

Then the RX8; flicked it into manual mode and redlined it before shifting, but in 3 attempts, my times were between 10.1 and 9.5 seconds. From what I've read, the 6 speed auto is meant to do 0-100 in about 7.2 seconds.

Now I know the times I got aren't strictly comparable to the published times, since my road wasn't perfectly flat, and there'd be a bit of fuzziness in the measurement too, but I find it pretty surprising that a car with about 20% less horsepower, ~150kg more weight and 2 fewer gears would roughly match / beat the RX8.

Compression isn't an issue as mentioned, and the previous owner had the coils replaced and the plugs cleaned a couple of months ago, and had been getting the air filters cleaned as part of his regular 6 monthly service.

Any ideas what the problem could be?

Kinbote

Maybe this message was too long, so I'll summarise (and this will be the one and only bump):

1. Given that the compression is good, the spark plugs have been checked, the coils replaced and the air filters cleaned all within the past 3 months, is there anything else logical to check that might be slightly impeding acceleration?

2. Should a 2006 6AT RX8 accelerate faster than a 2.3 litre 4 speed automatic Nissan Teana/Maxima? Am I just imagining a problem where this isn't one? It's not like I bought it for the acceleration, but if there's something wrong I'd like to know so I can fix it.

Any advice appreciated.

Kinbote

Turns out the garage that had been doing the services for the previous owner was next to useless. I replaced the spark plugs; they were filthy despite allegedly having been cleaned 3 months ago.

Their 'coils replacement' turned out to be 'coil replacement' -- just one -- so I've replaced the other three, which were A-series so I'm assuming never changed since the car was made in 2006. Feels a lot livelier now.

Next I'll replace the air filter they'd allegedly been checking and cleaning, which looks pretty worn out and which I'm assuming has also not been changed since 2006.


One question: if I take off the cat, am I going to be able to tell anything by looking at it? And is it possible to clean them, or do they just fail and need to be replaced?

Junkman 6394226

Cats just fail and need to be "replaced".

Good on you for the maintenance though! May I suggest spark plug wires?

Fendamonky

Did you make a comparison run after replacing the coils and plugs?

Kinbote

Hmm okay, thanks. Won't bother removing the cat then.

Yeah, I forgot to say: wires next, then air filter.

It definitely feels a bit livelier after replacing the coils and plugs, especially in the low revs, but I still feel like it's being held back by something when the revs get high, which is why I'm thinking cat, but the air filter's probably not helping either.

I'll do another timed run to see if there's any measurable difference after I've done the wires and air filter.

Loki

iTrader: (1)

I'd get that cat checked. Clogged cats kill engines.

alnielsen

iTrader: (4)

You can inspect the cat by pulling down the front and doing a visual inspection. They deteriorate from the front, plugging up or burning open. In a perfect one, you will see a honeycomb pattern. A little burning in the center will be OK.

Yes, a clogged cat will create too much back-pressure that will destroy the seals on the rotor.