RGHTBrainDesign

Next time you take your exhaust manifold off and inspect the turbo, take a look at the impeller blades, shaft play, and of course, for a sooty residue. What's more important, at least for rotaries using the original OMP is the fact that a turbo generates a lot of heat and is oil cooled. This means that when you shut off the engine immediately, oil cokes itself (burns) inside of the turbo's oil line, which if not already clogged, will continue on to the inside of your engine.

Have you ever felt burnt oil? It's just like everything else that's burnt and carbon based. It's a powdery, dry substance that DOES NOT LUBRICATE. The choice is yours, but there's a definite reason why a turbo timer is one of the best investments for longevity of any car, NA or FI. Oil cooling is important.

Sgtblue

iTrader: (16)

^Wrong. The stock twins are not oil-cooled, they're water-cooled. As mentioned earlier, sitting and idling, or adding a turbo timer has VERY little value on the FD. It can even be counter-productive since engine temps tend to rise at idle, not lower.
Soot on the hot side impellers means nothing other than possibly your running rich. In any event it's common and generally harmless. And I've never heard of any direct relationship between the OMP and oil coking in the turbo feed or return lines. Please, connect that dot for me.

RGHTBrainDesign

First off, while the FD might not be oil-cooled, most turbocharged vehicles are. Water and oil temps alternate in parallel. When one goes up, so does the other... Idling would then, in that case, bring temperatures down after a drive (assuming you drive your SPORTS car the way it was intended).

Assuming you upgraded your turbo, which most of us do, to something with an oil cooled system while retaining the OMP, the oil would now circulate through the entire engine, be burnt off internally, and also lubricate and cool the turbo. During a fast shut-off period, the oil would coke the turbocharger's bearings possibly restricting the flow of oil. It would also dirty the oil faster which is then being pumped through the OMP to the inside of the engine where it is burnt again. "Crankcase" oil would lose all lubrication value almost immediately and destroy both turbocharger and engine (most likely the turbo first - smaller bearings and 100x the RPM).

I'm only trying to save an engine here, not create a debate about it. Its your car, do what YOU want. This is what keeps them going, plain and simple. Whether or not YOU choose to listen to the facts is your doing, not mine.

Sgtblue

iTrader: (16)

Let's pause here for a moment. The OP has a low mileage, all original FD. All your nonsense is then, useless.
After a drive air stops moving through that heat-exchanger called a radiator. And NO air is being forced through the oil cooler(s). Sitting and idling after a drive then, brings temperatures up. Even with electric fans. Watch it yourself on any decent aftermarket temperature gauge.
And cupcake...chances are I've been driving a sports car longer than you've been on the planet. So please...
It might be close, but most of us are probably still running the stock twins. Regardless, all this has absolutely nothing to do with the OP's car or this thread. He has the stock twins. They are water-cooled and will not benefit from a turbo-timer. Even if it were accurate, for all the relevance you might as well be discussing single turbo conversions on a Yugo.
No. You were wrong and giving bad advice in the New Member Section. It wasn't going to save anyone's engine and would do more harm than good.

Akagis_white_comet

iTrader: (4)

Sgtblue and SirLaughsALot, flaming each other is NOT permitted, especially in the New Member Technical Section. Keep the bickering crap in PMs.

Let's have a recap of the issues and pertinent data on the vehicle in question: The car is a low-mileage FD, presumably near or entirely bone-stock. Its factory twin turbos are cooled just like any other turbo rotary: coolant and oil. My 20B's twins work just the same.

The FD's cooling systems are already stretched thin in capacity, with a radiator and oil coolers downsized from the FC's parts. Touring and Automatics are specially known for this, having only a single oil cooler compared to the R1/R2's twin coolers. Add in a second turbo and the whole package will need as much cooling capability as it can get, hence Coolant AND Oil Cooling for the turbos. Compare the turbos' oil feed and return temperatures and you'll see for yourself how much cooling the oil delivers.

Coking oil on a turbo is well known among the rotary community as the result of improper shutdown procedure. This can happen to any turbocharged car after the fun pedal has been in use for an extended period of time. It's the whole reason turbo timers were invented and last I checked, quite a few FD owners have one for this reason.

In regard to the oil coolers simply doing nothing when sitting idle, such as at a traffic light, this is complete BS. Please re-read Aaron Cake's article here:
The Myth Of The Electric Fan

Same thing applies to the oil coolers. My FC oil cooler has a thermostat, as do the FD ones. Heat is transferred from the oil to the material of the oil cooler's core (usually aluminum) by means of Thermal Conductance. From here, the heat is transferred to air flowing through the core by means of Conductance again. This is why Oil Coolers, Radiators and Intercoolers are colloquially referred to as HEAT EXCHANGERS.

Yes, it will be hotter when idling after a spirited drive than compared to idling after warmup. This is called Heat Soak. To solve the argument, how about you go for a spirited drive to get everything nice and toasty, then stop in a parking lot with the hood up and take measurements of the oil cooler's temperature at the inlet and outlet every minute for 30 minutes. Then graph the results.

Unless the vehicle is so poorly designed in getting air through its heat exchangers (the FC & FD are certainly not), I doubt it would heat soak unless its oil cooling capacity was so ridiculously undersized for what it is being demanded to do. Regardless of airflow, heat exchanger performance is directly correlated to the surface area of the core. This is the whole reason why heat exchangers such as a radiator have boatloads of tiny fins.

Anyway, enough about thermodynamics for now, I'll leave the rest of it up to our logic genius Aaron Cake. Back to the FD now stuck in Limp Mode with a wacky OMP and impending 4-digit pricetag.

stauren1203, you drove the car while paying attention to the pertinent gauges. That is the correct thing to do. 5 minutes of idling after some heavy-foot fun is perfectly fine to cool everything down. A redline a day keeps the mechanic away. As for the OMP issue, you're getting fleeced. There's no doubting a new one is as expensive as a Standalone ECU ($1537 from Mazdatrix), but I know without a doubt you can get a good used one on here for maybe $100. Go retrieve your car, premix and drive it back home. PM Logan at Defined Autoworks (GTORX7.). I'm fairly certain he has an extra FD OMP at the shop at any given time. If he somehow doesn't have one, he most likely knows someone that does and will hook you up on the cheap.

I know the mechanical Pre-1989 OMPs can be rebuilt, not too sure about the S5 and later electronic ones. Logan would know more about it than I do.

To get to the OMP, you'll have to remove the turbos and possibly the water pump housing (been awhile since I played with a FD, download the FSM from the 3rd Gen FAQ for more info). Removing & reinstalling the turbos is a good experience for a new owner, with proper direction from an experienced owner. Can be done in an afternoon, excluding jacking up the car. Anyway, be extremely careful with the OMP lines as replacing them means removing the Upper Intake Manifold and is generally a PITA to get to them on the rotor housings. At $40 each, it's not very fun either. Someone makes braided stainless steel OMP lines for ~$100 per pair, so it would be the better option. On my 20B FC, I just converted it to use 03AN braided stainless steel brake lines instead.

Sgtblue

iTrader: (16)

Who in the hell is flaming? I'm not perfect, but would put up the accuracy and usefulness of my posts in this thread against his anytime. I told the OP how to check the CEL code, correctly predicted what code it would be, and linked my how-to to help him. Along with providing what I think is some other good advice for a new owner with an original low-mileage FD. But OK, you handle it from here. The only thing is....you don't have to remove turbos, waterpump housing or anything to remove change the OMP on an FD. See the earlier link to my how-to. Sorry if that's bickering.
Awaiting deletion of this, but that's OK.

RGHTBrainDesign

Thank you Akagis. As I already stated, I was only trying to save an engine, not start a debate.

I might be new to rotaries and to this forum, but I sure as hell am not new to cars and turbos.

Sgtblue

iTrader: (16)

https://www.rx7club.com/3rd-generati...-timer-869548/

https://www.rx7club.com/3rd-generati...-timer-712374/

https://www.rx7club.com/3rd-generati...-timer-685788/

https://www.rx7club.com/3rd-generati...-timer-864015/

Sgt Fox

iTrader: (3)

Just wanted to weigh in here. Akagis did not mean to accuse anyone of trying to start a flame war, he simply wanted to remind everyone to keep to the facts. This thread seems to be full of good information, so lets continue as we were.