Quote:
Originally posted by JKWright
Strictly speaking, all production engines are internally balanced. But that doesn't mean that an inherently raucous design such as a long-stroke inline four can't benefit substantially from balance shafts. That's why Nissan sucked it up and increased the cost and complexity of the QR25 by installing them.
The term "barely perceptible" is of course relative. What's barely perceptible to a gung-ho-nitrous-equipped street rodder is overwhelming to John Four Door. Clearly, if the gain in adding a substantial amount of cost and complexity in the form of balance shafts in the QR25 were as small as you describe, the Nissan beancounters would never have approved their installation. Considering that the company couldn't be persuaded to part with an extra hundred-spot per Altima to upgrade the interior to, say, Malibu level, it makes no sense to assume that the company would drop several hundred on balance shafts that provide only "barely perceptible" decreases in NVH.
My advice: If your Altima or Sentra is a mild daily driver that you plan to keep for a few years and also in fact hope to sell for actual cash monies one day when you're done with it (rather than the alternative of wadding it up and tossing it into the ditch), leave the balance shafts in there. [/b]
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In the first Jarrod, you are wrong, there are many production engines that are externaly balanced, like most domestic engines!
As far as the validity of removing the balance shafts, no its not going to affect the engines durabilty and may even improve it under some conditions. The first few QR25's that were modifed for racing use failed because of extensive damage caused by balance shaft assembly failure. The shafts seize at high rpm, much past 6500 rpm in fact.
The reason for the balance shafts exsistance is not for durabilty but because the NVH target for the QR25 was to meet or exceed the NVH chariteristics of the VQ30DE engine. However I bet that many people wouldnot be able to tell that the balance shafts were removed if they were not promted, thats how subtile the differences are. In fact I had a hard time telling myself!
Plus for most people, finding 8-10 hp in a naturaly asperated engine is quite a large amount, especialy if its free hp without a fuel consumption penalty. This mod is also easily reversable, you can reinstall the balance shafts when you sell the car.
What you are stating as fact is only conjecture on your part and your opinion. You have never done any of these mods nor do you modify any of your cars. I have had these sorts of arguments with you on other forums before. In fact your famous Bosch spark plug argument was proven wrong once more data was avalible but after you dropped off that mailing list.
You are correct in your advice that if you are not a person into modding the car whose primary concern is to have a warranty and a lack of NVH, then don't remove the balance shafts, in fact don't consider any modifcations, keep your car totaly stock.
Here are the facts without any opinion from you or I.
1. Will void engine warranty
2. Will give 6-10 wheel hp depending on how done
3. Will improve durability under racing conditions
4. Will increase NVH by a very small amount.
5. With the JWT kit, is easy to reverse and put back to stock.
6. Will not hurt the engine under normal street use.
7. Will increse the amount of oil avalible to the main and rod bearings
8. The JWT kit will improve oil control, reduce windage and reduce oil starvation under cornering.
Whether or not this has any value to the consumer is up toi the consumer, anything else is just opinion.
Mike