At 70 MPH, what tachometer readings do you guys see?
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In the 3500-3750 RPM range. I'm running slightly lower profile tires than normal.
3000
70mph for me is 2850 rpm about
At 70 I am at 3,200.
Robert---I thought I was super low but 2,850?? Sounds more like a Chevrolet of some kind.
What about the Subys---what rpms @ 70?
2800 rpm for me.
Jack Crosby posted:At 70 I am at 3,200.
Robert---I thought I was super low but 2,850?? Sounds more like a Chevrolet of some kind.
What about the Subys---what rpms @ 70?
Do you know what your transmission setup is? Mine is a stock setup from Kirk at VS with a 3.88 transaxle. I checked my speedometer with a GPS and the speedo on 80 is 78 mph and I'm just a hair over 3,000 rpm. At 70 mph I'm below 3,000 and it looks close to 2,850. I could be a little off (well okay I know personally I'm a little off) but not by much.
David, I'm afraid to look.
at 3,000 I'm doing 60 so I'm thinking at 3800 I might hit 70...(4:12 r&p)
at 70, I have many more years before I hit that number.. 
.. No, I think I am running about 3200rpm.
I have 3:88 trans, 185x60x15 tires, at 70mph tach is just below 3,000rpm.
I have standard VS 3:88 train, 1915 VS mild build, 165x80x15, at 65mph I'm about 3000rpm... 70mph would be under/about 3300rpm.
David:
Do you know what transmission(3:44, 3:88,) gear ratios (1,2, 3, 4) and tire size you have?
then we can go from there........
TEBS
PS don't listen to them they all eat fruit loops for breakfast and have Farrah faucet posters on their garage walls.... Wait a minute..................... so do I
I've got a 3.44 with .93-4th gear and 185/65-15 tires and at 3000 it's about 72.5 so I would guess at 70 it is 2850-2900.
I put your gears in the chart (gearset 1), Frank. The discrepancy is probably speedometer error.
http://calc.teammfactory.com/i...26+2&trannytype=
Just for fun I included the 5 speed. What engine are you running?
That speedo does seem a little iffy. I've got a 2110 from CB.
Given the archaic technology, our speedometers are never going to be "spot on" through the whole range. If it's only off 1 or 2 mph at 70-75 I'd consider that not bad at all.
ALB posted:Given the archaic technology, our speedometers are never going to be "spot on" through the whole range. If it's only off 1 or 2 mph at 70-75 I'd consider that not bad at all.
Even my North Hollywood recalibrated Porsche 914 speedo was off by a couple of miles per hour. Almost impossible to get them to be spot on.
Interestingly enough, so was my tach before I had NH recalibrate that too. I thought it read a bit on the high side and after I hooked up my laptop to my (piece of crap) CB fuel injection it did show a difference of 200 rpm.
I do about 3800 at 70mph with 175/70 tires. I supposedly have a 3.88 trans but now I am starting to wonder about it.
I have a 3:88 final with a .89 4'th, 205/16 tires, polished wheels, black lug nuts, a wooden steering wheel, ivory dash knobs and color-matched floor mats.
At 70mph on my Tom Tom GPS, I'm running just slightly between 3,100- 3,200 rpm but I have a slight rumble at that speed so most of the time, rather than do the sensible thing and slow down for the rumble to go away, I go up to 3,400-ish where it's a bit over 75 - pushing 80 and it smoooooooths right out. So, basically, I'm keeping up with I-90 traffic at 3,400. Especially if the scenery is decent (no, not the distant scenery..... The decent scenery).
Rule of thumb: 2X the tach. 3,000 RPM = 60 MPH, 70 MPH = 3500 RPM. Seems to be about right for me, and was exactly that on my old 356s. Have not checked with my Garmin nav system, but could do that one day, I guess. Am pretty sure my speedo is just a rough guess, as it jumps about and is JPS OEM, i.e., Chinese crap. Tach was definitely Made in China crap, so was re-mfr by No Hollywood Speedo with VDO innards and should be pretty good.
So, if my 2110 engine with 225x50x15 tires tachs 3500 to 3750 @ 70 MPH, I must have a high rear end/tranny like 4:12 and not a 3:44 or 3:88?
DAVID BAYNE - BAYNIAC posted:So, if my 2110 engine with 225x50x15 tires tachs 3500 to 3750 @ 70 MPH, I must have a high rear end/tranny like 4:12 and not a 3:44 or 3:88?
Read this previous post by @justinh
https://www.speedsterowners.com...4#331887649598646144
His is the 8th post down and it shows approximate rpm's etc for different configurations. He also tells you how to figure out what you have with a simple test.
Thx Robert M
Bayniac wrote: "So, if my 2110 engine with 225x50x15 tires tachs 3500 to 3750 @ 70 MPH, I must have a high rear end/tranny like 4:12 and not a 3:44 or 3:88?"
In a nutshell, yeah.
I used to have a .89 fourth and a 4:12 final and 70 was running around 3,500. Only difference was 225X50X16" tires (so I would be going a couple of miles faster).
Me to I have a high rear end and I need special made to measure pants
When I had my track Miata I would occasionally take it on short trips and at 70 mph is would rev at around 4000 rpm. Strangely enough, the high revs didn't bother me, but one time I cruised my IM at 4000 for 20 minutes and the engine noise/sound really bothered me. Not a pleasant sound at all. On top of that, the engine oil temps went way up too.
The engine felt/sounded just right (to my ears) at around 2800 to 3000 rpm.
Mine actually smooths out quite a bit at 4k and becomes quieter.
Mine sounds best at about 5000-5500 but I don't spend a lot of time there.
I get scared at 50...
Lane Anderson posted:Mine actually smooths out quite a bit at 4k and becomes quieter.
Did the oil temp go up? My engine definitely did not like cruising at 4000 rpm, but then-again my engine never did run properly.
Engine temp stays steady even in hot weather. It may be steady at a slightly higher point, but not much.
I verified 60 mph on my gps at 2,800 so that translates to 3266 rpm at 70 mph. I've got a 3.44 r&p with stock gears but with what I think might be short tires. I measured 11.25 " from the floor to the center of the hubcap.
Yeah Dave, those tires are 1.5 to 2 inches short of Standard.