ok guys this might sound stupid, but im still fairly new to the rotary engine and how it works. I was thinking about the whole "dont driver hard when the engine is cold" advice that i have heard in so many places, even refering to the rotary engine. Now i understand that in a standard piston engine, the warm up is to allow the internal parts to reach their expanded sizes and to do their job best, mostly refering to the pistons and their rings which protect oil from leaking from under the piston where it lubricates to above the piston rings where the gasoline - oxygen combustion takes place.

Now. My question is... if the rx8 and all rotary engines are supposed to burn oil, and there are only 3 moving parts, what is the point of not driving hard when cold?

I'm going to try and answer my own question with possible soultions, because i was bored this morning and tried to figure it out.:
1. the cat is very ineficcent when it is cold. This could lead to cat damage or muffler damage, but i dont know how.
2. The rotors expand slightly and better seal off the chambers from each other, preventing the accidental leakage of gas / oxygen / oil into another chamber.


ok thats all i got. thanks in advance for your replies.

 

I believe #2 is the best answer

 

but how could that damage the engine? it seems that it would just be alittle bit less efficent, but not damaget the engine......

wheres rotarygod when you need him?

 

1. Bearings and eccentric shaft, rotors, e-gears, seals - all need to reach operating temperature before you drive hard. Your bearing clearances will not be correct when cold, so you need to go easy until everything reaches operating temperature (which is NOT right when your coolant temp gauge reaches it's normal position - oil takes longer to warm up than coolant, and is a much better indicator of when your engine is properly warmed up. You need to run at least 5 minutes beyond when the coolant temp shows op temp).

2. Oil pressure - when oil is cold, the engine has significantly higher oil pressure than when the oil is warm. complicating this, the oil pump is gear driven off the eccentric shaft, so the higher you rev your engine, the higher your oil pressure is. With cold oil, it is possible that the oil pressure would be too high, resulting in blown seals etc.

Don't do it - be patient and wait until the engine is warm before using full throttle or high revs.

Regards,
Gordon

 

thanks thats exactly what i wanted to know

 

It is largely because of dissimilar metal junctions. The rotor and side housings are made of cast iron and the rotor housings are aluminum, and these metals have different rates of thermal expansion.

Running the engine hard will cause warping of the rotor and side housings as they heat faster than the rotor housing, and will result in poor sealing and increased friction and imbalance.

The computer is also programmed to swamp the engine with fuel on wide open throttle to compensate for the air surge, in order to prevent a temperature spike in the engine from running lean for a short period. When the engine is cold, the computer already must run overly rich just to sustain ignition, since the fuel atomizes much poorer than when warm. The added fuel on top of this promotes fouling of the plugs by allowing a buildup of unburnt hydrocarbons and ash to build up around the plugs and on the side seals, increasing friction and the odds of detonation events once the engine heats up. Not to mention that it degrades the finished surfaces of the combustion chamber.

Modern catalytic converter systems are highly efficient even after just 20 seconds of engine running time.

 

Long story short: Don't do it unless you're leasing.

 

Wrong. Even if your temperature gauge is showing normal operating temperature in less than a minute (seriously?), I explained above that coolant temperature does NOT mean that the engine is fully warmed up. The engine's metal parts and the oil take significantly longer than the coolant to reach proper temperature.

Regards,
Gordon

 

Also, I don't know if the ECU will even LET you romp on it when the engine is cold. The RX-7 had an extra set of throttle plates that restricted the intake when the engine was cold. I imagine the totally computer-controlled throttle plates make that easier - the ECU just won't give you full throttle travel when the engine is cold. But, this is speculation, I'd have to dig into the shop manual to be sure.

Dale

 

The rev limter is reduced when the engine is cold - to something around 6000 rpms. It doesnt take long for the restriction to go away though, the temp gauge only has to be a couple of ticks north of dead cold for the cold-rev-limit to disappear, which is prior to when then engine would be fully warmed up.

My guess is the amount of 'danger' increases exponentially the colder the engine is, so beating up a dead-cold engine is far far worse than when the temp gauge has started to move, which is a bit worse than waiting until the temp is normal.

Simon.

 

this might sound stupid but i just got my rx-8 a couple weeks ago and the people who sold the rx-8 to me told me that i always have to wait 1 min before driving and 1 min before shutting off the engine everytime i use it(not just in the morning) and i didn't see it anywhere in the manual so i'm wondering if this is true??

 

I don't drive it hard until it's warmed up. After starting it, I don't wait to start driving it (although I try to start it before putting on my seat belt, etc) nor do I rev mine before shutting it down unless I have not drove it for more than five minutes or so. My 1st rotary, 10 k miles, never flooded.

rx8cited

 

why anybody would want to drive hard when the engine is cold is a mystery to me. i mean.....does it really suck that bad to let the car idle for ~30 seconds then drive slowly until full operating temperature is reached? i realized some may have to merge onto highways or whatnot but you still take the time to warm up the engine properly. same should go with shutting it down....i usually let the car idle down for 30 seconds or so depending on how hard i drove prior to stopping.

keichi tsuchiya says on a cold motor you should let it idle for ~30 secs.......then drive slowly until normal operating temps are reached. that way the differential can warm up properly as well as the engine oil. his analogy is that would you run a marathon as soon as you woke up?

 

I've had my 8 since sep '03 and I now have 18000miles on the car. Never once followed that... i just suggest you don't drive at WOT until your engine temp goes to normal operating temp