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View Full Version : High Rpm's, why?

shayrgob240
07-10-2005, 09:47 AM
Hey!

I just bought a 95 240sx w/ a rb20det. I dont know if the tach is messed up or if the car is supposed to be revving high. I drove the car on the highway and i was going fairly slow(60-65) and the rpm's were at about 4K and if i went a little faster it was at 4.5K. The speeds that i have listed are just a rough estimate b/c the speedo is messed up from the swap. Can you guys tell me what the norm is for the rpm's when on the highway? thanks!

PS- The reason why i think this is abnormal is b/c of my last car(eclipse gst) that was always at around 3K when on the highway.
EEdude
07-10-2005, 10:16 AM
For a 6cylinder, RPMs around 60mph should be roughly 2,500. The guy who had it before you probably changed the final drive to something a lot lower, for quicker accleration.
shayrgob240
07-10-2005, 11:05 AM
well, im not sure what the guy before me did w/ the car and i really have no idea how to really find out. So, i have 2 questions:

1) How do i find out what happened if the previous owner doesnt know.
2) Does that not put a lot of stress on the engine if continously driving w/ the rpm's at 4.5K

thanks!
Maeda
07-10-2005, 12:50 PM
Taller final gear?

OR

Broken Speedo.
JDMs13
07-10-2005, 02:14 PM
Does it sound like 4K? Prolly has japanese final drive out back. When Im on the highway just takin it easy, Im at 4K also. Sucks on highway, but worth it everywhere else. Kinda forces you to keep it around 60-65, at least for me it helped. That and the japanese speed warning bell thingamigigy.
TheSnail
07-10-2005, 02:27 PM
Its like this. 89-90 tach does not work. 91+ works, but its horrably inaccurate. The higher the rpm on the tach the more inaccurate it gets. Im sure you pin the tach quite easy. Well, buy the time its showing 7k rpm, the motor is only turning at 5.5k. Get a tach from a skyline and it will work flawlessly.
shayrgob240
07-10-2005, 05:29 PM
ok, I'll try and get the cluster in ASAP. thanks!
420sx
07-10-2005, 06:41 PM
why just not get a aftermarket tach and wire it into the speed sensor?
TheSnail
07-10-2005, 06:48 PM
ok, I'll try and get the cluster in ASAP. thanks!


You dont need to instal the cluster, just unscrew the three screws that hold the tach in, trim the plastic on the rb20 tach a little, then place it in your 240 guage cluster.
TheSnail
07-10-2005, 06:55 PM
Like this, here's a pic one of mine, takes 10min.

http://www.imagestation.com/picture/sraid128/p8cbaf7f1ac62da75b9bb8562601adfb3/f7e40254.jpg
shayrgob240
07-10-2005, 06:55 PM
that sounds like a good idea but the problem is that the speedo is screwed b/c its trying to read k/ph instead of MPH. So i was thinking that if i swapped in my skyline cluster it would solve the problem since it would be meant for it. Or is there a way to get the stock cluster to read the proper speed? thanks!
TheSnail
07-10-2005, 06:58 PM
Use the stock KA speed sensor. The trannies are the same. So the stock one just bolts on.
allstar
07-10-2005, 07:05 PM
my friends s14 with a rb25 does the same shit.. At freeway speeds hes rpms are around 5k, and then if he punches it the rpms go all the way to 8k and stays there for 1 sec intill he has to shift.. I always thought that shit was off or maybe the ecu was tuned b4 he got it.