RX-7 rotary probs

You wouldn't get full boost as before if the engine isn't producing the same compression. The turbo can only work with whats being shoved out the exhaust manifold.

Unless the ECU is in limp home mode or you have the secondary set of plugs not functioning for whatever reason then you guess correct in that the apex seals have gone.

Check the former first.

What mileage is on it, and what has the servicing been like? You *must* use a good mineral oil in these rotaries, changed every 5000miles, NOT a synthetic.

Tim..

Good point. It's been puzzling me why I'm showing full boost - so could it be that there's some sort of turbo leak in the intake side?

Chris.

We've always used mineral oil and change it regularly - the car is pretty much just used once a week to keep it running and the odd long journey to give it a blast. We have bills showing it had an engine rebuild some 50,000 miles ago (or thereabouts) - so I'd expect quite a few more miles out of it unless something wasn't done right at the rebuild. Conor had a good point about the turbo boost... as I understand it now, if my apex seals had gone, I wouldn't be getting enough compression to give me full boost. Maybe the ECU is stuck in some odd mode - any clue how to find that out? It stalled once and flooded some time ago - I'm sure it's never been the same since then. We changed all the plugs a while back as well... for such a small engine, you'd think there'd be more room in the engine bay!

Chris.

Try pulling the ecu fuse for between 10 mins and a couple of hours, let the ECU reset, and then let it learn again. See if that makes any kind of difference.

Maybe but the dashboard guage is only a mickey mouse one akin to the petrol guage, i.e it'll give you an indication but isn't really accurate. You'd need to attach a proper guage that gives proper readings to find out what its truly doing.

The tips of the rotors were notorious for failing at low mileages and it was one of the reasons that that particular car didn't fare well.

Yes, but by the Turbo II Mazda had significantly improved the design... they were still a weak point but if you look after a 13B rotary turbo it should last up to about 120,000 miles. Still, a lot of the evidence for high mileages comes from the US, where it was one of the biggest selling import cars for several years running - of course, over there you'll see a lot more long-distance running and less rotary-killing town driving. Still, I'd think 50,000 miles is a bit low for a 2nd gen RX-7 turbo.

Chris.

Even if the rotor seals had "gone" I would still expect pretty much full boost- perhaps alittle higher up the rpm range than it used to, as when speed increases it will sort of regain the sealing abilities of the knackered tips.

I would go back to the plugs, double check you're actually getting a spark at both sets, changing them isnt good enough.

The ECU should have a window in the side of it with a red and green LED in it. If Red is flashing a code with engine running- note it down.

The later ECU's didnt have the LED's- bridge the test connector TF1 and TF2 and look at the check engine light.

It would be nice if you could perform a normal comprression test on a rotary!!!

Tim..

You might be onto something with the spark plugs. It really is down on power and feels like a misfire at full throttle under load. How would I go about checking to see if I'm getting a spark? Would just pulling off the HT leads on the second smaller set with the engine running be OK? IIRC, the secondary plugs don't start firing until somewhere over 2000rpm?

Mine's a late 2nd gen Turbo II, I suppose this doesn't have the LED's? I've never noticed them anyway and I've looked under the bonnet an awful lot... What would the check engine light show if I bridge connectors TF1 and TF2 if something were wrong? Shouldn't it come on anyway if something's up with the ECU/sensors/etc?

Yeah! I don't even know how to do a compression test! Time for some more googling (been doing it all day!).

Chris.

Sorry, I was going on the original ones.

Check all the hoses from the compressor on the turbo to the inlet manifold for leaks. It may be that but it sounds like worn apex seals.

Fraser

A few more miles ?

You should have had at least another 5 rebuilds done by now, no wonder it's knackered :)

I was just about to ask what sort of mileage it had done.

The rotary engines are known for only lasting about 60k between rebuilds - your 50k isn't unreasonable.

Get the work done, and it should last another 50k without problems - you can think of the apex seals like a cambelt on a normal engine.

Yes - as long as the seals are done once or twice within that period.

It'll do as much mileage as any other engine - but the seals need replacing every 60k or so.

Not really.

Hi Chris. I've got an RX-8 and after it was in for some warranty work the Mazda monkeys didn't put one of the trailing plug leads back on correctly and it ran like a dog for a while - misfiring and stuff. Popped it back on and it came back to life. Probably worth chgecking the sparks out. The trailing plugs are alse more likely to become fouled if it's been flooded.

Also FWIW, on the US RX-8 forum the whole synthetic/mineral debate has been done to death with people agreeing to disagree. There are people who claim to have been running RX7 turbos on synthetic for years with no problems and that synthetics actually burn better and cleaner than minerals oils.

HTH Paul

OK.. So we're probably talking apex seal replacement rather than full engine rebuild just yet.. Any ideas how much that would cost?

Chris.

Except it costs 3 to 4 times more than two belts on a V6.

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not really