Repiv Posted August 19, 2009 Share Posted August 19, 2009 I just started driving my 240z and am wondering what my rpms should be at around 60-70mph. I have the stock 4 speed and at about 62mph it is at about 4k! http://www.geocities.com/z_design_studio/ according to this I should almost be to 90 at that point. Thanks. Quote Link to comment Share on other sites More sharing options...
MAG58 Posted August 19, 2009 Share Posted August 19, 2009 It depends. Which rear end do you have? Also you'll probably want to make sure you have the right speedo gear in the tranny for which ever rear end you have. If you do a search for your diff codes on here you'll figure out the ratios and exactly which color trans gear you need. Then you can accurately figure out if you really are that under driven. Quote Link to comment Share on other sites More sharing options...
Repiv Posted August 19, 2009 Author Share Posted August 19, 2009 As far as I know it is a stock rearend. My speedo is all out of whack though which may lead me to believe it is not stock. I used a GPS to get the speed I was going. [edit] Actually, putting 4.11 into the calculator makes everything close to how it is. 4k around 70mph and 2.3k around 40mph. I don't know why someone would add such a high gearing without changing the transmission though Quote Link to comment Share on other sites More sharing options...
PanzerAce Posted August 20, 2009 Share Posted August 20, 2009 Racing, probably. Quote Link to comment Share on other sites More sharing options...
hoov100 Posted August 22, 2009 Share Posted August 22, 2009 it says on my speedo that 60mph should be 1064RPM in 4'th. Quote Link to comment Share on other sites More sharing options...
Daeron Posted August 24, 2009 Share Posted August 24, 2009 I don't know why someone would add such a high gearing Hmmm. Couldn't say why, myself. Whatcha reckon you gonna do with that rear end? I'll trade you a nice 3.54 for it.. that will set you cruising at 60 mph at about 2800, 2900 or so. That 4.11, that thing isn't worth its weight in horse kidneys. Could you get a shipping quote to 33413? The above post is completely off, I don't know if he meant 1604 RPM and typed 1064 by mistake or what. I remember it being a little under 3K. (Its been about six years since I DDd my Z) Quote Link to comment Share on other sites More sharing options...
Repiv Posted August 24, 2009 Author Share Posted August 24, 2009 I got it out on the interstate again with it again. I got it up to 5k and I was only going 70-75 mph according to the GPS. Highly confusing. I'm picking the car up from getting wetsanded and buffed tomorrow so hopefully I can figure out what is wrong. Quote Link to comment Share on other sites More sharing options...
deja Posted August 24, 2009 Share Posted August 24, 2009 What size tires are you running? Quote Link to comment Share on other sites More sharing options...
Repiv Posted August 24, 2009 Author Share Posted August 24, 2009 205/60R14 I believe Quote Link to comment Share on other sites More sharing options...
deja Posted August 24, 2009 Share Posted August 24, 2009 With those tires and a 4.11 at 5000 rpm you should be doing 85.8 mph. Sounds like they have the wrong speedo gear. Quote Link to comment Share on other sites More sharing options...
Repiv Posted August 24, 2009 Author Share Posted August 24, 2009 I'm not using the speedo. I'm using a GPS. My speedo is way wrong 'cause according to it at some points I'm going 100+ Quote Link to comment Share on other sites More sharing options...
jc052685 Posted August 24, 2009 Share Posted August 24, 2009 I cruise at 70mph at like 4500 rpm or some thing. 3.7 rear, 225-50-16 tires. Quote Link to comment Share on other sites More sharing options...
deja Posted August 24, 2009 Share Posted August 24, 2009 You should be taching 3501 rpm. I'm taching 2393 with 215-50-17 3.7 ratio but with .7 overdrive tranny. I cruise at 70mph at like 4500 rpm or some thing. 3.7 rear, 225-50-16 tires. Quote Link to comment Share on other sites More sharing options...
Repiv Posted August 24, 2009 Author Share Posted August 24, 2009 What's with the conflicting results? Quote Link to comment Share on other sites More sharing options...
deja Posted August 25, 2009 Share Posted August 25, 2009 I don't know. I punched the numbers into http://www.csgnetwork.com/multirpmcalc.html What's with the conflicting results? Quote Link to comment Share on other sites More sharing options...
Repiv Posted August 25, 2009 Author Share Posted August 25, 2009 Me and my buddy took his 260z out with the GPS and checked his 4th (he has a 5spd swap) since they are both 1:1 and 60 was 3k, 70 was 3.3k and by 4k we're nearing 90. Same tire size and stock rear end as far as he knows. Basically what that calculator says. I wish I could figure out what was causing this. Even 4.11 gears doesn't explain the HUGE difference. Quote Link to comment Share on other sites More sharing options...
jc052685 Posted August 25, 2009 Share Posted August 25, 2009 You should be taching 3501 rpm.I'm taching 2393 with 215-50-17 3.7 ratio but with .7 overdrive tranny. Yeah, but I have a 4-spd..... Quote Link to comment Share on other sites More sharing options...
Daeron Posted August 25, 2009 Share Posted August 25, 2009 Me and my buddy took his 260z out with the GPS and checked his 4th (he has a 5spd swap) since they are both 1:1 and 60 was 3k, 70 was 3.3k and by 4k we're nearing 90. Same tire size and stock rear end as far as he knows. Basically what that calculator says. I wish I could figure out what was causing this. Even 4.11 gears doesn't explain the HUGE difference. http://www.atlanticz.ca/zclub/techtips/drivetrain.htm According to two different sources linked to from that page, no S30 ever had a differential with a gear ratio higher than 3.545. The 260 Manual cars had 3.364. You have 4.11 you say, and all the transmissions had 1:1 4th gears so that point is correct. http://www.geocities.com/z_design_studio/ According to that, a stock 260Z, in fourth, at 60mph with 215/60-14s, (thats probably what you are running, just a hair taller than 205) is 2808. 3300 for 70, and 86 at 4K. The 4.11, now, according to the calculator, puts you at 70 mph at 4K RPMs, almost exactly. The calculator says 3431 for 60 mph, and 3546 for 62 mph. If I am wrong about my guess with the tires, then the numbers go even more towards what you are experiencing... and if we were both were wrong and you've got 195 or 185s on there, then its even sharper. 205-50s maybe?? That would cross 4K just about 67-68 mph. ALOT can be done with shorter tires, and a Whole Boatload has already been done by dropping the 4.11 gears in there. Just pretend its a Civic or a Miata *ducks*flying*brake*rotor*aimed*at*head* Quote Link to comment Share on other sites More sharing options...
deja Posted August 25, 2009 Share Posted August 25, 2009 Thats what I put in the calculator. Your gear ratio is 3.7, tire size is 24.86", final tranny ratio is 1.00, 3501 rpm at 70 mph. Yeah, but I have a 4-spd..... Quote Link to comment Share on other sites More sharing options...
blue72 Posted August 25, 2009 Share Posted August 25, 2009 If your tire size is what you say it is, then you could have a 4.38:1 rear end ratio. 205-60-R14 + 1:1 4th gear + 4.38:1 rear end @ 80 mph = 5000 rpm Quote Link to comment Share on other sites More sharing options...
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