87jap951

With the lighter rotars and different setup, is this a better engine? Long term? Do they suffer from the same flooding problems with age? Who out there has 89+ na RX-7's with over 100k? What has your experences been like?

NathanRX7

I have 140,000 miles on mine. It has not given me problems. I believe the 89-91 13Bs has less problems with flooding maybe none at all. Mine has never flooded.

Ryde _Or_Die

Well the 89+ do not flood near as much from what I have heard. I do know that the 89+ rotors have higher compression, which would lead to less engine life. It really depends with how the previous owner(s) treated & maintained the car before you had it though with these older cars.

Aaron Cake

iTrader: (1)

This is only my opinion, but I don't feel they are as reliable as the 86-88 engines because of the electric metering oil pump. It's much more prone to failure than the 86 style mechanical pump.

Icemark

I had a 91 coupe that had 110k on it when I sold it (needed the room, wasn't driving it) but it was fine, and had decent compression.

The only thing I don't like about the 89-91 NA motor is the electrical OMP, which tends to be prone to failure more than the 84-88 mechanical one.

SpeedRacer

I've gotten just over 100,000 miles on my 90GTU. When I first got it flooded occasionally, only after starting it and moving it and then shutting it off before letting it properly warm up. Then I soaked the fuel injectors in degreaser and the flooding stopped for 8 months or so. Now its starting to do it again whenever I don't drive it for 4-8 hours. But the greatest thing about the 89+'s is that if you simply floor it, while cranking the engine, it cuts off all fuel, so if it doesn't start within 2-3 seconds, I just put the pedal to the floor and then it starts right up, stutters for a few seconds while it blows out all the extra fuel. Before I knew about this trick, I'd always have to pull the EGI fuse to cut off fuel while cranking the engine, but this saves me SOOO much time, almost every day I have to do this now. My engine I think is starting to lose compression(I've done the ATF trick a couple of times). But I'm not entirely sure if its engine compression yet. Either way, I have driven me car harder than 95% of the people on this board. Lots of Auto-x's and lots of 1 hour plus backroad driving excursions, where my engine spends most of its time damn near redline. The engine has been solid as hell for me the whole time I've had this car. I've put about 35k miles on it, in the last just over 2 years, and I've never had a problem with it, except for the tranny going out a week after I bought it, but that had just been rebuilt, so I think the person who rebuilt it messed it up. My engine still pulls strong all the way to redline after all the abuse I've put it through. I don't have any experience with 86-88's so I can't say whether its more reliable or not.

Ryde _Or_Die

Ya if anyone is worried about the flooding problem just install a fuel pump kill switch. I have one in mine but never use it because my car doesn't flood really, only did once in over year.

pd_day

iTrader: (6)

Why would you say the higher compression will lead to less engine life?

Ryde _Or_Die

Bacause higher compression means more stress on the engine. Why do you think when they add a turbo to a non-turbo engine they lower the compression(if done properly)?

pd_day

iTrader: (6)

But isn't this taken care of when they put in lighter rotors and better engine design.

Adding a turbo to an engine = increase compression. Compression + boost = pressure within compression chamber = more a/f = more power.

9.7 compression in the 89+ 13B is not that high. Even my corolla has a compression of 10.1

Ryde _Or_Die

I never said anything about more power. We all know the 89+ has more power I am just stating that the higher compression does usually mean shorter engine life. But by this time in an engine's life it just really depends how well a car was taken care of. That formula of yours does equal more HP, but also lowers the engine life.

pd_day

iTrader: (6)

Assume all cars are taken care of equally

When you say high compression = short engine life, is that for all engine applications or just the rotary?

When you say shorter engine life, which parts are you suspecting that will fail first?

Moreover, the 89+ engines are DESIGNED to run higher compression with the lighter rotors. Higher compression = more stress, but lighter rotors = easier to move = less stress. Doesn't that offset the stress factor??

Ryde _Or_Die

Well the general rule that I have heard is that the 86-88s usually last somewhere around an extra 20k if both taken care of properly. Like I said before, at this point in the engines life(10-15 years old) it might not make any difference.

pd_day

iTrader: (6)

What if I have a brand new series 4 and a brand new series 5 engine.

And given that 89+ engines are DESIGNED to run higher compression with the lighter rotors. Higher compression = more stress, but lighter rotors = easier to move = less stress. And also the 89+ has a computer that controls the engine which is 2x fast.

Will you still still say series 4 will outlast the series 5?

BTW, you haven't answered my questions above.

Thanks.

ps. Not picking on you, just trying to strike an interesting conversation.

Ryde _Or_Die

Well yes, the series 4 should outlast the series 5, brand new(which brand new won't happen anymore). I understand what you are saying about the lighter rotors, I just have to stick with the fact that the higher compression takes away from the engine longetivity. I still would take a series 5 if I had a choice, no doubt. Hey you know something though? The series 4 actually has a better quarter mile time, NA at least. Guess that weight does make a difference.

pd_day

iTrader: (6)

SHOULD? Can you be more definite? As I said before, the lighter rotors will offset the stress created by the higher compression. So on what grounds would you say compression is still a factor?

You still haven't answer my questions:
When you say high compression = short engine life, is that for all engine applications or just the rotary?

When you say shorter engine life, which parts are you suspecting that will fail first?

When you say the series 4 gets better 1/4 miles times then series 5, it depends what you compare. If you compare a 86 sport with a 89 GXL, of course. What if it's a 87GXL vs. 89 GTUs, what would you say then?

Ryde _Or_Die

Ok, so you know I am not any mechanic at all. But the engine does still receive more stress(I would still think the apex seals would get that stress).

All engines life is shortened some by higher compression. You know all those Honda/Acuras they put turbos in? Well if they are doing it right they lower the engine compression for that.

About the 1/4 mile times:
86 GXL runs 16.5 & 90 GTU runs 16.7

pd_day

iTrader: (6)

We are talking about NA's here. Turbo is a different story. All engine has a limit. The reason honda/acura turbo cars lower the compression is because their engine has a limit too. The total pressure you can hold in the combustion chamber is finite. As I said before, compression + boost = total combustion chamber pressure. If they don't lower the compression, the boost added would put them over the limit and pop their engine immediatly. That is off topic though, we are taking strictly NA's here ok?

Base on your arguement, all the civics' engines should blow up before the RX7s' since they run a compression of 10.5!

BTW, apex seals don't break because of compression. They break either because of wear and tear, or bad maintanence.

btw, I said 86GXL vs. 89GTUs not GTU

Thanks.

ps. Please don't reply with high compression = faster wear. I have explain how the lighter rotors overcome that. Also, please use some more explaination in your post so I can better understand it.

pd_day

iTrader: (6)

We are talking about NA's here. Turbo is a different story. All engine has a limit. The reason honda/acura turbo cars lower the compression is because their engine has a limit too. The total pressure you can hold in the combustion chamber is finite. As I said before, compression + boost = total combustion chamber pressure. If they don't lower the compression, the boost added would put them over the limit and pop their engine immediatly. That is off topic though, we are taking strictly NA's here ok?

Base on your arguement, all the civics' engines should blow up before the RX7s' since they run a compression of 10.5!

BTW, apex seals don't break because of compression. They break either because of wear and tear, or bad maintanence.

btw, I said 86GXL vs. 89GTUs not GTU

Thanks.

ps. Please don't reply with high compression = faster wear. I have explain how the lighter rotors overcome that. Also, please use some more explaination in your post so I can better understand it.

check out this page for 1/4 times

http://2ndgenrx7.freeservers.com/performance.html

Ryde _Or_Die

I am only going by what I have been told previously, that the 89+ engines do not last quite as long as the 86-88. Ask around, I am sure there are people on here that know exactly why. I only used the 90GTU v 86 GXL because if you go to General Automotive, then to the top to Performance Numbers, those are what they have.

Sorry I don't know exactly why the 89+don't last as long, I just know they don't. Maybe someone else will chime in sometime, hint, hint.

pd_day

iTrader: (6)

All right, cool cool. It's just that I don't want the series 5 engine to have a bad rep, due to hearsay.....With no direct proof.

Later.

turboedRX-7

A interesting topic! Perhaps a short poll on what year/model you have and a quick respose as to how you think its been taken care of over its life? Turbo owners can chime in as well! I now have a 88T2 just hitting 119k well mainatined, very strong runner! Never floods...No smoke at start up or running.

kliftin

My 89gxl has 157,000. Not original miles. The first engine blew because of a cloged cat. With this engine I beat it down bad. I raced it with an intake leak, or leaks. I drove and raced with the leading coil disconected for 2000 miles. The timing has been advanced through the roof. So far It wont go anymore. (almost). And has been like theat since the rebuild. A also have a slipping water pump but never over heats. I have ran over curbs huge bumps bottoming out and autoxsed it. My cars compression is up and is very strong. original shocks and springs are still intact and working great. I took it for a road causrse and was awsome performing. My car feels like its invinsible although the primary injector just started to flood(dirty) only because I took the manifold off a few times and played with them carelessly. Easy to re engineer thou.
Enough said I think the 89 plus are more reliable. My oem pump is the original as well and has not failed even after 157,000 miles...

Scott 89t2

higer compression = higer temp in the compustion chambers = more wear/stress.

lighter rotors have nothing to do with stress. they just rev faster. same as having a lighter flywheel.

mguire

It's all in the timing. I think the reason turbo's have lower compression is so that they are less likely to ping. If you tune a car right, it should last. You can put a turbo on or inject nitrous into a higher compression rotary and still get longevity, but proper tuning is critical.

BTW, compression and rotary weight aren't the only differences between early and late FC NA's. Don't worry, just give the engine the tuning it deserves and drive it as far as it will take you!