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200SX 5 spd, 1983


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#41 cruznude

cruznude
  • Location:Albuquerque,NM
  • Cars:79 king cab, ford ranger

Posted 16 April 2018 - 08:59 AM

I HAVE A 79 king cab l20b with a 5 speed. It has all been de smogged and legal in New Mexico. My concern is that 5 th bear really doesn’t seem to far difference than the 4th. Seems to whine out. I wish it had a further going and then it would be quieter at the higher speeds. Out here the norm on the freeways are 80-85 around town and 85 -95 outside of town. I cruise descent at 85 but after that is another story. Sometimes have to do 100+ just to get out of the way

#42 datzenmike

datzenmike
  • Location:Vancouver Island
  • Cars:'74 710 sedan, '76 710. prevoius... '78 620, '71 521, '68 510 new '76 B-210

Posted 16 April 2018 - 06:48 PM

You should have an 11.8% over drive so if at 4,000 in 4th... 5th would drop 472 RPM to 3,528

 

Top speed in all vehicles is limited primarily by wind resistance. Keep in mind that as speed increases wind resistance increases 4 times for every doubling of speed. Four times not double. If it takes 30 hp to drive along at 50 MPH it will take 120 hp to drive at 100 MPH. To make power a gasoline engine needs to rev up. It will make more power at 4000 than it will at 3,500. If you reduce the engine speed too much it will go faster in 4th revved up than in 5th at lower revs. This is called being power limited. Over drives are not intended to be used to go faster, only reduce engine revs at cruising speeds. Nissan engineers probably did the math and selected an over drive that will work fairly well with your 620.

 

If you can keep up with traffic I would just leave it as is. It's only noise, and an L20B red line is 6,500 RPM so you won't hurt it. You might go to a lot of trouble to go slower. Spend some money on sound deadner.


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#43 cruznude

cruznude
  • Location:Albuquerque,NM
  • Cars:79 king cab, ford ranger

Posted 17 April 2018 - 11:15 AM

Thanks for the reply mike