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Jun 14, 2004
South Central Texas
Just read a write up on the new Northstar 4.4 supercharged V-8 in HotRod magazine. It has variable valve timeing (VVT) and piston oilers which spray a mist of oil to the underside of the piston. This engine is a techno wonder. It should be included in the great engines of today. Does the VVT use a separate pump? The article states that it uses a separate oil circuit. Also do the "piston oilers" spray sequentially or are they spraying continuously? Anyone have any other input into this engine? Also, what other wonders of engine design/alternative designs are Cadillac (and GM in general) working on?
MAJA as of 1 year ago they were still trying to get the VVT working. The slightest amount of dirt in the oil was pluging up the actuator. We will have to see how it does in the long hual! I hope they are spec.'ing a synthetic oil for it. The N.Star has had a lot of issues with oil consuption, oil leaks and noise issues with the oil pump and water pump discharge sides. They also have way to many sub assemblys and gaskets wich can complicate repairs and increases the chances of leaks! It is not a bad engine but it is not even close to a Lexus V8 or a Mercedes V8!
MB OM 616 and 617 turbo engines had piston oilers from late seventies, oilers were also common in lots of Yamaha and Honda high performance motorcycle as well as car engines. In case of MB, the oil was sprayed continuously. it was also cooled through a huge, oversized oil cooler.
The new generations of Northstars don't have near the problems that some people credit them too. They have the awful 4.1,4.5,4.9 reputations and some early N* problems to overcome, but they are doing it. -T
Oil Sqirters are not new. Volvo was using them on the later 94-95 4 cylinder Turbo's. Great performance safety item to have with an engine that is running under boost. You could also refer to them as piston oil coolers. My sister has a 95 Eldorado and my brother-in-law has a 99 Deville with the North Star engines and have had ZERO problems with either car.
Wow, John, you sure know your stuff! I had no idea that the NStar motors had such problems. I also saw that article in Hot rod, the thing that caught my eye was the integrated intake manifold/intercooler. Some interesting technology in that intercooler, though with intake charge temps are still rather high. An external-type intercooler is still best but presents packaging problems with a roots/twinscrew blower mounted atop an engine. Lots of engines - especially performance engines - spray the undersides of pistons with oil, including BMW motorcycles if I'm not mistaken. But it's fairly common at any rate. I love articles like this. [Cheers!]
I think that any engineer working on an engine should always try to make it with as few parts as the design will permit! Useing small subassemblys to make a larger part like an intake manifold or tensioner is always bad news! THe fewer gaskets you have the less chance they are going to fail prematurly. The more flat surfaces you have at mateing surfaces the eaiser to seal inclined planes are never a good idea. Transitioning the water and oil inlets and outlets with reguard to pump rotation and galley flow should be comon sense especialy to an engineer. Not useing so many stamped parts and cheap tubeing also is an issue on an engine in a $40,000 plus vechile! Only the best materials, designs and assembly practices should make it into an engine in the price range of $40,000-$80,000! They still have issues with excessive oil consuption as well! I still belive that Cadilac wold be better off useing a Corvette block makeing the changes I recomended years ago (wich have almost 100% been done on the latest greatest ZO6)and then add their own twin cam VVT heads and PCM to it! It would cut cost across the board as production numbers increased, increase reliabilty and durability and slove all of the gasket issues andother N.Star realted problems! THey would also be able to do without the forced induction or lower the pressure even more. By lowering the pressure reliabity goes up and the intercooler could be eliminated as well! If one looks at the Lexus V8's and Toytoa's V10 in the Crown and the 4.7 iForce V8 the simplicity of all of the complex systems is incredable! The gasket are kept to a minimum as well! Very little plastic and stamped steel parts inside orpart of the engine itself! Anyone that has ever had to rebuild a N.Star or help someone rebuild one has an idea what I am talking about they are a nightmare!
John ,what seems most interesting to me is that the manufacture cut any thing to the absolute minimum to increase the profit .It seems the most simple would be to reduce the parts needed to get the job done . I prefer no moving parts well maybe one.
John Browning makes a very good point, the Land Cruiser and the venerable Nissan Patrol is among the prime example. Both till the early nineties used push rod iron block and head engines carried over from the 60s with subtle yet effective mods, They were rated to be among the most durable engines to be built, you can see quite a lot of them trudging the deserts of Australia, Africa or ME. The old Mercedes OM 616/617 were another prime example of minimalist yet effective feat of over-engineered design. MB will never come close to making engines like that anymore, probably as it does not make good economic sense.
Gurkha,I really like push rod over built engines ,simple easy to repair and trouble free. Lots of people don,t understand .
It comes down to engineering and R&D time. You can build a simple manifold with an upper and lower section and call it good or you can build it with 5-7 pieces.You can have a variable vale timeing system with 6 parts or you can have on with 20 parts.You can make you mateing surfaces on inclined planes knowing that you can not maintain the clearnaces and depend on a cheap unstabil elastomer gasket to keep it sealed up or you can make the surfaces flat and either precision machine the surfaces so no gaskets are need or you can use a cheap paper gasket that is stabil and not have an issue. You can always make a design from fewer parts if you try a bit harder. It is just like many of the machines the Germans made dureing WWII were incredable feats of engineering but were often so complex that a machinest had to come out and custom fit the part when someting broke! You can also make a comparison between a Thompson SubMachine gun and a AK-47. If make a machine more complicated then it needs to be to fullfil the mission all you have done is increased it's chances of failure! Far better to concentrate your time on refineing the design and it's manufacture. igh qulity controls will almost always beat out complexity every time!!! Know with that said I have no problem with VVT or 5 valves per cylinder or directinjection etc.... I just think any design should always be as simple as it can be made and still function as needed. Durability has almost always favored simplicity!
robbobster, GM's current V8's have a lot of potential!! Performance with out refinement in my mind is not that big of a deal in a production car! IF they wanted to make their cheap to producr push rod engines world class I would love to help them! I doubt it will ever happen though. A lot of the changes that they made to the block for the latest Z06 fall right in line with what I have been saying they needed to do since day one! THe only thing I wish they would do that they have not done is push the rings down the piston some, give it a better skirt. Rework gasket sealing surfaces. Dapen the engine better in most of their line up!
Push rods specially in low revving engines are the best and easiest to maintain. However when HINO decided to go for OHC design, instead of chains which will eventually stretch, they decided to go for alloy gears which work out pretty good, surprisingly quiet too.
JB, do you consider the lightweight castings used a major cause of alot problems? With computer engineering things can be designed to a minimum alot easier.
JB, your posts are a little hard to follow, but what potential refinements are they currently missing in THIS Cadillac pushrod engine, keeping in mind this is not an assembly line regular GM V-8? Have you read the Hot Rod writeup I mentioned in the original post on this Cadillac engine? It appears, to me, to be a very refined engine, with a complex, yet technological advanced intake/supercharger manifold. But explain the need to "push the rings down the piston some" and "Dapen the engine better". I think this engine, along with the pushrod 7.0L V-8 for the '06 Corvette should be included in the list of "Elite" engines of today. Of course, we will have to see how they perform in the marketplace before the jury is out, as with anything.
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