ray green

iTrader: (14)

I've always heard that it is important to use the Mazda thermostat because cooling is so important on a rotary, but could this just be another Myth being used to increase profits at the Mazda dealers?

Yesterday I installed an Autozone thermostat ($6.90 vs the $25 Mazda version) and FINALLY I'm getting a nice steady temp reading of about 1/3 on the guage. This after generally high readings and random fluctuations on the temp guage over the last three months, mostly a problem at highway speeds, that sometimes approached but never fully reached overheating.

I've checked or replaced everything I can think of in the cooling system, including three Mazda thermostats in a row, all without fixing the problem. Now this cheap little Autozone thermostat seems to have done the trick.

It's true that Autozone people don't know much about rotaries, but I've found the Mazda parts people don't either, and most of the time they have to special order stuff you can find on the shelf at Autozone. So I don't see any difference here. And Autozone is always much much less expensive.

Parts is parts, sometimes not going with OEM can be a problem. I'm thinking about that Autozone oil filter I got for our MP5 that didn't seal properly and would have burned up the engine if I hadn't caught it right away.

But sometimes it might work the other way, I've been messing with this cooling problem for months and if this Autozone thermostat fixes it, well OK, I'm happy. I just wish I had figured it out before I spent all that money on Mazda thermostats.

Now I'm starting to wonder about the standard advise against using Denso spark plugs because only the NGK's are correctly designed for Mazdas. Of course the NGKs cost twice as much as the Denso's.

I have a set of Denso's that came with a car I bought and of course I immediately replaced them. But they are practically new and they look like they are constructed as well or better than the NGK's. So is the NGK spark plug advice a myth too? I think I'll give them a try.

What are other people's experiences using after brand parts vs the much more expensive Mazda versions?

Ray

Re-Speed.com

iTrader: (3)

I have always used NGK plugs and Mazda oil filters. Everything else has always been what ever I ended up with including thermostats.

Not sure why on the oil filter, I just always have. I like the fact that I can drop by a dealer and pick up 5 or so and they come with new drain plug washers.

-billy

Tsi_Xtreme

I'm using a autozone thermostat. But i got the best one, Failsafe, if the engine reaches over 220 degrees it locks open so the engine can't over heat.

84RX_Se7en

Using an Autozone thermostat too. Duralast model that costs $6.90. It has had no problems with fulctuation. Now the motor itself on the other had has had a bad bad time with cooling.

hanman

I have had horrible luck when I have tried non Mazda thermostat's. Not only on RX's but on my Millenia and my Probe (MX-6). All of them had overheating problems until I replaced them with Mazda tstat's. So, I am a believer. IIRC, the issue is the bypass valve built in to Mazda tstats. Maybe with a better quality aftermarket that is built in also? I don't know. But for the measly difference in price I will always buy Mazda.

As far as plugs go, NGK's or Nippondenso's will work fine, and if you search you will see that is what has been posted. It's just the NGK's are easier to find.

84RX_Se7en

Keep in mind Nippondenso originally made a lot of things for the car electrically and they make starters and alternators for them much like Mitsubishi. I'd trust Nippondenso plugs. I have a ND starter right now that has worked great. Even after sitting in an empty engine bay exposed to weather in my GSL.

Nicholas P.

iTrader: (1)

I don't have NGK spark plugs or wires or a Mazda thermostat. Works fine accept that its a summer time thermostat.

I actually started to think its just for advertising. The rotary is a 2 stroke just like any other small motor.

A motor is a motor.

OnlyOnThurs

Ughhhh i hate the DURALAST brand!! BLEH!!! terrible quality!

fluffysheap

Nippondenso makes good spark plugs, it's just that the NGK are more common. Just avoid the Autolite is the important thing.

ray green

iTrader: (14)

OK it looks like the problem was the thermostat, what a difference a $6.90 Duralast thermostat from Autozone can make (part #15397, rated at 170 degrees and yes it has the jiggle pin, just like the Mazda part).

It's been a couple of days and a couple hundred miles now and the temp guage is holding rock steady at 1/3, the idle is much smoother, throttle response at highway speeds is stronger and steadier and gas mileage is up.

All this after three OEM Mazda thermostats in a row didn't fix it and three months of pain-in-the-*** trouble shooting (it couldn't be the thermostat, right?, since I just installed a new Mazda OEM part).

I have always wanted nothing but the best for my RX-7 so I always got Mazda parts. But they are way overpriced ($25 vs $6.90 for the thermostat, for example) and some (but not all) of the Mazda parts people seem to have this attitude that they are providing a service just to be able to get parts for our "twenty five year old cars", whatever the price.

So from now on I'll start at Autozone (or CarQuest, A-1 Auto or whatever the local car parts supermarket happens to be) and give their parts a chance first, then only use Mazda only as a last resort.

I'll try the Denso's next!

alex_the_hipple

The rotary engine isn't a two stroke.

You're an idiot.

hanman

"I don't have NGK spark plugs or wires or a Mazda thermostat. Works fine accept that its a summer time thermostat.

I actually started to think its just for advertising. The rotary is a 2 stroke just like any other small motor.

A motor is a motor."


First of all, it's an engine. Engine = mechanical, Motor = electrical.
Second it's not a two stroke. It may resemble one, but it's not the same.

And take the advice or leave, it's up to you. But, I am convinced the Mazda Tstat is worth the money.
As far as NGK plug wires, they are fine, but there are better products out there.

There are many parts from the parts stores that are as good or better than OEM Mazda parts.

85rx12a

the bottom line here, is that you only get what you pay for. if you buy a less expensive tstat, sparker, starter, motor, or engine, you are going to end up with a product that has a less quality construction, material, or has been designed as semi universal, that is the only way they can sell the parts and profit. the RX7 is one of mazda many little children, they build only the best, or at least perfectly suitable parts for them.

trochoid

iTrader: (6)

Fwiw, concerning plugs, if one has an owner's manual, it lists the ND plugs, which, btw, is what they came with from the factory.

Even at the dealers outrageous price for a thermostat, I still think they are worth it. Particularly when balanced against the cost of a rebuild. When I 1st built the wb, I installed a brand new Stant, drilled out the jiggle pin, thinking it would help. Hole was no biger than the oem one. After driving 1300 miles to Denver and back, Christmas '85, and the temp gauge never going over 155 on my Autometer gauge, freezing the 'nads off, 1st thing I did when I got home was chang out thermostat. The oem one I installed was used and have not had a problem since.

Little Nicky, it's time for an afternoon nap, you've put your foot in your mouth, again. LOL.

ray green

iTrader: (14)

"the bottom line here, is that you only get what you pay for"

85rx12a, I generally agree with this statement, that is why I've been dishing out the extra bucks at the Mazda dealers for the last 5 years. But it didn't work with their thermostats.

Repeat: The 25$ Mazda thermostats DID NOT FIX MY NAGGING COOLING PROBLEM. Three different Mazda OEM thermostats in a row, two brand new out of the box, produced unsteady temp readings that every few days would rise up more than 2/3 on the temp guage, enough to make a rotary owner nervous.

Each of these thermostats passed the boiling water test, they started to open at 185 and were fully open at 190, but for some reason they were not performing well at highway speeds and were not regulating the coolant flow properly. When I first noticed this problem the first thing I did was replace the thermostat, with a Mazda one, of course. When this didn't work I then spent countless hours trouble shooting every possible aspect of the cooling system without any luck. Fortunately I had enough sense not to replace the water pump, temp sensor and temp guage.

I'm a true believer Trochoid and before this episode I would have been singing with the choir. But think about it, if you were selling Chevys, would you recommend to a Chevy owner that a Lexus that can do the same job better? I've never seen an owners manual that recommends anything but OEM parts, so does this mean that all cars were made with the best possible parts?

Mazda, in my opinion, does not make the best possible thermostat for their 25 year old RX-7s. Duralast part #15397 ($6.90 at Autozone and probably other discount stores) works much better, at least in my stock 85 GSL.

I've got nothing against Mazda, I'd like to see them stay in business long enough to produce another rotary powered RX-7. I'm just sharing some hard earned information and trying to save fellow rotor heads some trouble and money.

For once I'm going with the aftermarket crowd.

Ray

hanman

Ray, I completely understand where you are coming from, and I can't dispute your situation.
BUT....I have the exact opposite evidence in three Mazda's.
I am glad the aftermarket worked for you. It just didn't for me. I don't even look at the owner's manual when it comes to stuff like that.

I would say that if you are going to go aftermarket, then your advice on the Duralast is probably key. I know that some aftermarket tstats for Mazda's don't have the bypass. And therefore don't work right.

Nicholas P.

iTrader: (1)

OK why is it not a two stroke

I thought it was a two stroke because it does not take 2 passes of a rotor to compress and ignite the engine. It ignites intake and pushes out the exhaust all in one turn revolution of the driveshaft..

Instead of calling me an idiot why don't you just teach me. I'm sure I am not the only one mistakenly thought that.

capt murph

Don't be an *** AH.

rotaryspitfire

iTrader: (1)

It's not a two stroke, it's not a four stroke, IT IS NOT A PISTON ENGINE.

A rotary engine is an internal combustion engine, but it works in a completely different way than the conventional piston engine.
In a piston engine, the same volume of space (the cylinder) alternately does four different jobs -- intake, compression, combustion and exhaust. A rotary engine does these same four jobs, but each one happens in its own part of the housing. It's kind of like having a dedicated cylinder for each of the four jobs, with the piston moving continually from one to the next.

Like a piston engine, the rotary engine uses the pressure created when a combination of air and fuel is burned. In a piston engine, that pressure is contained in the cylinders and forces pistons to move back and forth. The connecting rods and crankshaft convert the reciprocating motion of the pistons into rotational motion that can be used to power a car.

In a rotary engine, the pressure of combustion is contained in a chamber formed by part of the housing and sealed in by one face of the triangular rotor, which is what the engine uses instead of pistons.

Like a piston engine, the rotary engine uses the pressure created when a combination of air and fuel is burned. In a piston engine, that pressure is contained in the cylinders and forces pistons to move back and forth. The connecting rods and crankshaft convert the reciprocating motion of the pistons into rotational motion that can be used to power a car.

In a rotary engine, the pressure of combustion is contained in a chamber formed by part of the housing and sealed in by one face of the triangular rotor, which is what the engine uses instead of pistons.

The rotor follows a path that looks like something you'd create with a Spirograph. This path keeps each of the three peaks of the rotor in contact with the housing, creating three separate volumes of gas. As the rotor moves around the chamber, each of the three volumes of gas alternately expands and contracts. It is this expansion and contraction that draws air and fuel into the engine, compresses it and makes useful power as the gases expand, and then expels the exhaust.

The heart of a rotary engine is the rotor. This is roughly the equivalent of the pistons in a piston engine. The rotor is mounted on a large circular lobe on the output shaft. This lobe is offset from the centerline of the shaft and acts like the crank handle on a winch, giving the rotor the leverage it needs to turn the output shaft. As the rotor orbits inside the housing, it pushes the lobe around in tight circles, turning three times for every one revolution of the rotor.

As the rotor moves through the housing, the three chambers created by the rotor change size. This size change produces a pumping action. Let's go through each of the four strokes of the engine looking at one face of the rotor.

Intake
The intake phase of the cycle starts when the tip of the rotor passes the intake port. At the moment when the intake port is exposed to the chamber, the volume of that chamber is close to its minimum. As the rotor moves past the intake port, the volume of the chamber expands, drawing air/fuel mixture into the chamber.

When the peak of the rotor passes the intake port, that chamber is sealed off and compression begins.

Compression
As the rotor continues its motion around the housing, the volume of the chamber gets smaller and the air/fuel mixture gets compressed. By the time the face of the rotor has made it around to the spark plugs, the volume of the chamber is again close to its minimum. This is when combustion starts.

Combustion
Most rotary engines have two spark plugs. The combustion chamber is long, so the flame would spread too slowly if there were only one plug. When the spark plugs ignite the air/fuel mixture, pressure quickly builds, forcing the rotor to move.

The pressure of combustion forces the rotor to move in the direction that makes the chamber grow in volume. The combustion gases continue to expand, moving the rotor and creating power, until the peak of the rotor passes the exhaust port.

Exhaust
Once the peak of the rotor passes the exhaust port, the high-pressure combustion gases are free to flow out the exhaust. As the rotor continues to move, the chamber starts to contract, forcing the remaining exhaust out of the port. By the time the volume of the chamber is nearing its minimum, the peak of the rotor passes the intake port and the whole cycle starts again.

The neat thing about the rotary engine is that each of the three faces of the rotor is always working on one part of the cycle -- in one complete revolution of the rotor, there will be three combustion strokes. But remember, the output shaft spins three times for every complete revolution of the rotor, which means that there is one combustion stroke for each revolution of the output shaft.

Nicholas P.

iTrader: (1)

I'll go sit in the corner now.

lol



-nick-

t_g_farrell

iTrader: (1)

I see your point but I suspect the results. I got my tstat from one of the mega auto stores and the car always ran a bit hot. Then I switched in the tstat from mazdatrix ($17.95+shippin) and the temps are now good. Along with that I changed oil hoses and of course refilled the coolant. Was it the tstat, the oil lines, or the rebled coolant? I'm not sure myself. Maybe all three did it.

My question is while swapping out these three tstats your talking about, did you change anything else ? Could it be that this last time you changed one other thing or maybe did a better job of bleeding the cooling system than before?

resjsu

When I bought NGK plugs 2 days ago the guy at Kragen told me that one of those companies bought the other out so they are the same company now. either NGK bought out ND or vice versa.

alex_the_hipple

Hmmm...
thank you.

chedda_j

AGREED. Ive had this arguement with someone before. Stroke is definded as a motion that goes to a point and returns in the opposite direction. Therefore a rotary engine is more like a 1 stroke or no stroke motor. lol

j_tso

iTrader: (2)

Speaking of Mazda OEM vs aftermarket, let's talk oil pan gaskets.

VB has one that's $10, Mazdatrix & Racing Beat's are $30. Is there a big difference between the two, considering some people don't even use a gasket on their pans? Is the OEM one more expensive just because it was cut by Mazda?