and you thought FD's ran hot...
 

I'm snowed in on a Saturday night, so I've been trying to read up on newer engine designs just to sort of keep up with the times. And look at these little gems I came across. Many of you may be familiar with BMW's N54 engine, the direct injected twin turbo motor in the 335 etc. I had heard that these things ran hot but I am kind of stunned at the temperatures they run from the factory, intentionally.

These cars have ECU controlled electronic water pumps with various water temp targets. It turns out that the temperature a stock FD might run on a hot day is the same temperature the N54 runs at when it wants to be "eco" friendly:

https://www.rx7club.com/attachment.p...1&d=1264915498

I'm kind of stunned at how hot this (108C/226F) is for an intentional target temperature. I hope this doesn't compromise reliability over time. And to all of us worrying about our oil temps, how about this?

https://www.rx7club.com/attachment.p...1&d=1264915854
148C/300F oil temps and the ECU doesn't even bat an eye!

But it's a piston motor, so at least the exhaust temps are cooler than a rotary... or not.

https://www.rx7club.com/attachment.p...1&d=1264915498
1050C/1922F preturbo exhaust temps! I know it's direct injected, but this is a piston motor straight off the showroom floor! I don't know if I should be impressed or worried... maybe FD's don't run so hot after all? I mean this doesn't make them more reliable or anything, but it just puts things in perspective.

and at this point I'm starting to think the FD doesn't even run that rich compared to other cars, except at idle/low load (hence the airpump). I've collected a lot of OEM fuel maps for turbo piston motors that run deep into the 10's and 9's AFR from the factory.

interesting read. Maybe I'll re-think my desire for an Z4

Its likely to make it last only long enough for the warranty to run out. I have a great disgust towards that brand.

High temps to be eco friendly makes sense. The extra heat helps burn hydro carbons.

I don't doubt it makes sense for fuel economy and emissions, but was the motor manufactured and tested well enough that it can run at or near those temps for years? Hence my comment about not being sure whether I should be impressed or worried.

The high temps also lead to greatly increased NOx production...

Yes but the N54 is not a stratified charge direct injected engine so its NOx concerns are not as great.

1900 oF doesnt seem right....
my DIESEL TRUCK.... we keep it under 1600 before slugs melt...

I know the Germans have traditionally liked running their motors hot. An old roommate had an early '90s VW Corrado that ran some crazy temps stock.

The killer on German cars is they LOVE plastic cooling system parts. You thought our plastic AST was bad? Try plastic water pump impellers, that's good fun when that disintegrates and you have to pull the timing belt and everything to fix it.

BTW, the Corrado actually had a recall because the heater cores would rupture, sending hot coolant all over the driver's legs. It was a full on NHTSA safety recall since you'd likely get in a wreck with that happening, or come away with some nasty burns.

Dale

I cant say for sure as i have NOOOO information at all about them... But generally BMW does build pretty reliable stuff and put alot of R&D into their cars. As far as I know a bmw is not normally one to have engine failures and the sort. I assume alot of research (maybe years prior to its release) went into those engines.

Interesting info... care to share your source :)

^ http://www.e90post.com/forums/showthread.php?t=38856 engine management document page 44

lol.....BMW spent a lot of time on that engine....it is designed to last. One of the premier manufacturer's of our time is NOT going to embarrass themselves.

Anyone remember Smokey Yunick's adiabatic engines? Now THOSE ran "hot".

well I know there was some kind of oil cooler debacle on that motor

I'm reminded of a story I heard from my dad when I was a little kid, about a Rolls-Royce owner whose car had broken down. As the story goes, the man was picked up by representatives from the factory, wined and dined and treated like royalty until his car was repaired.
When we commented on how wonderfully he was treated while his car was fixed, a Rolls official says, "Sir? You MUST be mistaken....Rolls-Royce automobiles do NOT break down."

"Debacle"?

Hmmmm....I just searched two different BMW forums and don't find more than a couple of posts about this. While I agree it is a problem that should not occur on a high-end car, I don't see it having been a huge issue.

Of course...one can say 'yet', as this IS a relatively new engine. One COULD wonder what the experiences of the 2nd and 3rd owners might be like say in...5 - 10 years from now. :scratch:

On VW VR6 they intentionally run coolant at 240F with a 1.3 bars cap. They also have an electric auxiliary water pump to cool off the heads after shutdown. These are all 2004+ VR6.

The problem with our car is that we have micro-boiling too close to the o-ring using the 0.9 bar cap. Solution for me at least is the Evans NPG+ with a 7 lbs cap and boiling point at 375F.

I have run the NPG+ equipped engine at 280F coolant temp in Arizona at 118F ambient and 0.9 lbs of boost without ill effect.

I'm not so sure about that. I live right across the street from a BMW dealership and that dealership will literally line the block with broken down cars. I know that's anticdotal information about their overall reliability but I can tell you a lot of their reliability has to do with perception.

looking out the window right now, I can see no less than 30 BMWs that have been there for an extended period of time. Most of them were brought in on flat-beds. (some of these are the super high end models)

There's also a guy here in the building that has a mid-level BMW coupe and had the engine replaced in under 150miles.

BMW had to replace thousands of engines in the e46 M3. Same for the 4.0 V-8 in the 540i.

When I used to work in a repair shop, we used to joke that BMW stands for "Break a Man's Wallet."

Hmmm, you know, here in Europe, we have some troubles with BMW specs ...

The better example is about the gear oil, they are always sticking "Use only ATF" or better, "Longlife oil, do not purge" on their gearboxes and for example, many many users of the E46 3 series have been (are) in trouble with major problems in gear change etc...

Go to BMW => "Your gearbox is broken, you need to replace it".
Go to some 80W90 or 75W80 gearbox fluid => Oh god, no problem now.


The fact : BMW and some constructors are actually making their vehicles runing good ONLY for a certain period (like 5 years, most of the guarantees), and don't care about the "second hand life".

Exactly like these plastic water pumps, or these E46 rear wing literraly tearing !!

All these things appears about 5 years + or very hard driving ...


There is the "post 2000" political for BMW at least. I ran an old M30B35 engine in an E28 '1985 and it's rock solid, only one oil service with 13 drift events a year. You won't see that anymore.

it looks like in the reliability game, misery loves company

I just took a look at my neighbors BMW. It's a 328i. 2door.

i dunno, 1050C exhaust temps, 108C coolant and 148C oil temps would melt a rotary... BMW isnt using any more exotic material than mazda... what makes you think THEY can get away with it, when nobody else can?

I'm really not all that surprised. Back in the days when I was involved with some engine development for circle track racing, we were running our motors right at around 220 deg with oil somewhat above that. As long as the water temp was stable, and it did not boil, everything was fine. The limiting factor was that we were mandated to run pure water on the track. (It was not uncommon to put 20# or more of pressure in the cooling system to raise the BP.)

In fact, the motors consistently produced best power when everything was HOT, at least 220 deg.. I know is seems counter-intuitive, but the dyno (and race results) proved it out.

We did not consider it overheating unless there was boiling, loss of coolant or a spike in temperature.

The key, IMO, is to maintain ALL the hot areas in the engine at or below safe temperatures. The main problem with the rotary is to keep the rotors and the stationary combustion face (and the exhaust ports) from becoming too hot, since the rotors are not water-cooled, and the block combustion faces are used for EVERY combustion. So, a 180F (or 200 or 220 or whatever) water temperature does not mean that the rotors and stationary combustion faces run near that temperature. They run MUCH hotter in comparison to the coolant temperature. A piston engine, by comparison, can more effectively control the temperature spread.

That is why:
1. Piston engines can run hotter coolant, especially with insulating materials on the piston tops, and
2. Water/meth injection in a rotary does such a good job of allowing high HP w/o destructive heat in the combustion areas (ref Howard Coleman's articles).

So, IMO, hotter coolant temp in a high-power rotary would cause problems.