G2G

On 2nd gens the rear rotor is the most likely to lose compresion or blow a seal first because it doesn't get as good of air flow to it as well as not enough fuel, from what I hear this is the same on the 3rd gens. While the cooling system does it's job it isn't able to overcome the increased heat temperatures that the rear rotor sees. Think about it, before getting to the rear rotor the air must first pass through the radiator then through the intercooler then across the front of the motor next past the front rotor housing, across the side plate then finally to the rear rotor. By now it has absorbed much more heat and thus isn't able to cool as effectively. Add all the various components, emmisons, turbos, power steering, ac pump etc, which diverts air flow and you may have a reduced amount of air reaching the rear rotor housings, which doesn't help either. Someday hopefully when I get a good laser thermometer I'll go out for a spirited drive and then measure the temperatures on both the front and the rear housings. I'm guessing that between this site and rx7club someone has probably done this and has readings although it may be hard to find. I'm just too damn lazy to go searching for it right now.



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rfreeman27

The airflow to the motor does not really affect temps to the degree you are thinking. The rear runs hotter because the coolant route, the front rotor gets the coldest coolant.



On the FD the rear rotor's intake tract in the manifold is much straighter, making it run leaner and hotter then the front rotor as well.

Jims5543

The problem with stock FD's is the turbos + precats. The precat gets glowing hot and when you shut it down that heat rises into the back turbo (already cooking) and then heats the **** out of the rear rotor.



The rear rotor gets a lot of abuse like rfreeman27 said because of the coolent flow too. It doesnt help matter that a pair of blow torches are bolted on to it too.

G2G

You'd be surprised at the temperature differences. If you take the stock underbody cover off the FD you'll notice that you will run hotter. Airflow plays a major part. But if the rear rotor on the 3rd gens runs leaner due to the runner design than I would think that would be the larger factor playing into them grenading quicker than other generation 7's. And if the precat causes that much heat exchange than that will effect it greatly as well. Regardless I will still be interested to see how many miles Jim can get on the motor, then compare it to an fd with similar mods.



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j9fd3s

when we used to run the fd up in the hills, you can get to the top open the hood and the turbos are glowing enough to see the studs holding it together. those turbos are the reason the -rew doesnt last very long.

rfreeman27

Yeah, Removing the belly pan diverts air away from the rad/ic, which are the things actually cooling the motor! Do you think that the FC gets much air to the motor to make any difference?



It doesent really have anything to do with actual air hitting the motor.

G2G

If you fabricate an underbody tray that covers the bottom of the engine bay and design slits in the back to dissapate the air, you will find you have lower under hood and running temps because the airflow is concentrated in a certain area and has no other way to flow but out of it. I think the REW would run lower as far as cooling temps in an fc because you have a larger air space, and less crap cluttering the air flow. But like I said since you guys have just brought up something that I didn't know before about the turbos running so extremely hot and the intake runners design which promotes lean conditions in the rear rotor, I am forced to believe that those two components effect the motor more than the airflow. That's why I want to see what the difference is really like by comparing an FD with similar mods to Jim's. Although I believe most likely Jims will be put through a harder test considering that from what I understand he autocrosses and I guess roadraces often, which will subject the motor too much different conditions than the daily drive to work or the store.



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j9fd3s

thats another difference, the fd oil cooling DOESNT WORK below about 20mph. i put an oil temp guage in my r1 and it just pegged if i was below 20mph, but above 40mph theres nothing you can do to make the oil temps go over 180f

Jims5543

You're reading way too much into this. It has NOTHING to do with V-8 swaps. I have said before I dont like them but who the hell am I to tell you what to do with your car?? Its your car do what you want.



My point was that, here I am contemplating chipping the ECU, upgrading the turbos, upgrading the exhuast and adding a better intake to the wifes A-6 2.7T some day and making it an M-3 killer. Then I looked at the odometer and it reads 50K miles and I think, "****! Thats too many miles to be boosting the hell out of this car the engine might give out."



Then I thought:



"Damn! How many people buy Turbo RX-7's with over 100K miles on them and immediatly turn up the boost add some bolt ons and double the horsepower. Then 6 months (if that) later the engine pops and they scream and yell Rotaries suck?"



It really has nothing to do with a V-8 swap honestly. It was more of a "this is why Rotaries get such a bad rap" thread.

j9fd3s

after looking at working on my mercedes, i have no idea why people think piston engine are even a good idea.....