Info on 2nd Gen RX-7s

[SentraWV]

Anybody have any info pro/con on the 2nd generation RX-7? I spied one on the way home for sale (1991, non-turbo, 77,xxx miles) that I'll probably go drive tomorrow. Anything I should know going in? Any deep dark secrets?

Thanks,

[johnnytavo]

don't know much other than they are a very good ITS car ; )

[gtfour77]

I don't know anything abou them but if you need any help working on it let me know...I've been itching to take a close look at one for a while now (especially the rotary engine)... I am sure Bill might have some info for you...

[SeanB]

don't know much other than they are a very good ITS car ; )

And extremely loud Spec Wreckers... I mean RX7s.

[Potent357]

1991 is the last (and best) year.

All of the big 2nd gen problems had been addressed by 1991 so there is nothing major to look for but neglect from owners.

If it's a local car, look for service records. Raines has only occasionally had a mechanic that knew what they were doing with the rotary engine.

The hardest thing for a rotary engine is to idle. Look for excessive smoke on startup and a rough idle. If it will idle smoothly at approx. 800rpm it's a very good sign of an internally healthy engine.

It's a trick to set the idle abnormally high to mask major problems with the engine.

Interior bits and pieces are somewhat fragile and expensive to replace (if looking for a showroom interior). Conversely, if making an event/track car, a tidy sum can be made from stripping various pieces for sale on ebay.

Finally, the exhaust is usually a good sign for how the car has been treated. The factory twin mufflers are very expensive to replace so few owners actually do. Look for something nice that runs from the catalyst back. If the cats have been removed (common), that's a sign of a stingy owner.
The rotary exhaust is much hotter than a piston engine and cats and mufflers don't last as long.

Rear suspension complex and prone to crash and curb damage. It's wise to lay under the car and closely inspect the suspension arms for damage.

The engine itself (without turbos) is amazingly simple. Were it not for the emission controls, a 7th grader could understand it. Look for quality, and fresh, spark plug wires and fresh plugs are a must. A good rotary owner will replace the plugs every 5-10 thousand miles. (1500 for me)

Is it navy blue? I have been keeping my eye on a navy blue 1991 for years. It's owned by some couple that lived in Kanawha City. It always looked very well taken care of. I never agreed with their political leanings (always had a presidential campaign sticker on the back), but they sure seemed to take care of their car.

[sts 50]

Why not just buy a "real" 944?

[SentraWV]

Thanks for the info, Bill. It's either dark blue or black, depending on the light.

NP: The Mars Volta, De-Loused in the Comatorium

[erwendell]

As much as love them, in general the car is on the bad side of the power to weight ratio. The rotary just doesn't have that much torque and the second gen chassis added a lot of weight. You wouldn't believe how much that big glass rear hatch weighs. As I recall, the first gen GSL-SE is faster but with the second gen car you get a much better rear suspension and in my opinion better looks. The cool thing about a rotary is that they run so smooth it's easy to keep it wound tight enough to make use of the available hp and offset to some extent the poor torque. The problem is that the gas gauge drops like a rock. This has to do with poor thermal efficiency of the Wankel rotary relative to a piston engine. Due to the large surface area of metal that is exposed to the combustion gasses at their peak temperature a lot more of the energy that is produced by the combustion of the fuel gets dumped into the cooling system. Due to the way the rotor moves in the housing and the location of the exhaust ports a lot gets dumped out the exhaust as well. All this means that less energy actually gets turned into mechanical energy to move the car. In short, the Wankel rotary is good on the power to weight scale but poor in what's called brake specific fuel consumption which is a fancy way of saying how much of the energy contained in the fuel gets turned into usable power.

One more thing to keep in mind. Due to the aforementioned smoothness and the need to make hp you will be tempted to keep the tach wound tight but don't be tempted to over rev it. I have a book in a box here somewhere that shows a graph of loads on the eccentric shaft bearing and rotor gear teeth relative to rpm. Much beyond 7k rpm it starts to resemble a vertical line. In order to get the Renasis (RX8) motor to it's 9k redline Mazda had to do a serious redesign of the rotor in order to radically decrease its weight and therefore the inertial loads on the bearing and gear.

On to a few more specific points. The rear suspension of the second gen rx7 uses rubber bushings and some fancy linkages in order to produce dynamic rear toe changes that are supposed to provide a sort of rear wheel steering in order to provide better handling. The problem is that as the rubber in the bushings gets old or you throw big sticky tires on the car you end up way outside the design parameters and as a consequence end up with tricky handling. You should think about replacing said bushings or if allowed install a kit that replaces the bushings with metal spacers. This isn't a BTDT on my part as the last one I drove seemed just fine but it had stock size non performance tires. All the serious second gen RX7 racers eliminate the bushings though.

Check for signs of coolant leaks at the interface between the rotor housings and endplates and for mysterious loss of coolant when running. The engine is basically a sandwich of cast iron side housings and aluminum rotor housings with o-rings in grooves keeping the coolant inside the engine and away from the compustion chamber. The problem is that corrosion can attack the edges of the o-ring grooves and pretty soon coolant gets around the o-rings and in places where it's not wanted. The only solution is an engine rebuild and replacement of the rotor housings. I'm not sure if Mazda uses a special color anti-freeze at the factory but it would be interesting to know if the coolant is the factory color and whether or not its been changed frequently. Over time the additives in the coolant that are there to fight acid build up wear out and then corrosion takes place. On a related subject, overheating is the rotary's worst enemy. The foot and a half long studs that hold the sandwich together are steel while the rotor housings as previously mentioned are aluminum. Aluminum expands at a greater rate than steel. If the engine gets overheated the rotor housings have nowhere to expand to and can crack under the stress.

Bill's tip about smooth operation at the correct idle speed is spot on. That and careful listening at the tail pipes at idle is about the best indication of internal engine condition you can get short of having a shop with the specific compression tester needed for rotary engines. A normal compression tester will just show you the peak pressure developed by any one of the three combustion chambers of each rotor and won't reveal damage to an individual apex seal. The proper rotary engine compression tester hooks to either a chart recorder or an oscilloscope display so that you can compare the peaks of the compression pulses. That said, the normally aspirated 13B has had well over two decades of development work behind it and AFAIK is pretty reliable. The turbo motors are another story as the apex seals usually get blown to bits the first time some zero cranks up the boost. I've got one of those sitting in my garage right now and no, I wasn't said zero, just the guy who bought the motor for real cheap after the fact.

In summary, it's a really cool car, a current classic that is likely to only go up in value from here on out. I just wouldn't have one as a daily driver (fuel consumption) and I'm not certain that it's classed competitively.

Phew, some day I should just write a book or at least open a shop. Hope that helps. BTW, if you're curious, the first car I ever bought (in '92) was a barely running '73 RX2 with the twin distributer 12A. Look it up, you've probably never seen one nor have I since I was stupid enough to give mine away.

[Potent357]

Thanks for the info, Bill. It's either dark blue or black, depending on the light.

NP: The Mars Volta, De-Loused in the Comatorium

Seriously, if it is dark blue and it formerly resided in Kanawha City, I have watched the car for years. It had Clinton stickers on the rear of the car for years and then I think they were replaced with Kerry.

The car was always kept very clean and I actually spoke with the man driving it once when I was in my Rx7. He complimented my car and was surprised when I heartily returned the compliment.

[SentraWV]

Eh, nevermind - I didn't really fit in it (not without performing some Zen-like contortions that are probably illegal in public), surprise surprise. I did fire it up and it idled a little high (about 1500rpm) and died when the A/C was turned on. The interior is in great shape, particularly for a 16-year old car. I didn't crawl around underneath. Oh well - that wasn't really what I had in mind for next year, anyway.

It is deep blue, Bill, with a little bit of paint peeling off the rear spoiler.

$4500, if anybody of more appropriate proportions is interested. It's at the small used dealer (forget the name) on Route 35 between the St. Albans off ramp and Teays Valley Road.

PS - thanks for the extra info, Roy.

[gtfour77]

It had Clinton stickers on the rear of the car for years and then I think they were replaced with Kerry.

So which one was the problem character? Clinton or Kerry? Maybe both? heh

[Potent357]

So which one was the problem character? Clinton or Kerry? Maybe both? heh

Well, for me, both of them.