I am doing a swap into a beetle and trying to get highway speeds close to that of the stock RX8.

So my question is: What RPM will a 2004 6-port 6-speed Manual be at when going 70 MPH?


Here's the link to my build if you missed it:

https://www.rx8club.com/rx-8-multimedia-photo-gallery-6/reincarnated-rx8-193949/

Thanks,
Josh

 

3,500RPM . Plus or minus the error rate that is present.

The 6th gear is basically 500rpm per 10mph. 3rd gear is 1,000rpm per 10mph.


Of course, this is assuming that the final drive is 4.444 and the "gearing" created by the tires size is on 18inch rims with 40 sidewalls. Change either of these, and you will have to change the other to keep the effective final drive the same.




This is a much self-debated question on my plans with the Miata swap, and if I should attempt to have the same rpm/speed as an 8. The tires won't ever have the same diameter, so the rear end would have to change to bring it to match, but "do I really want to do that?" Should I get even more acceleration out of it? Should I give up some of that acceleration for low RPM cruising? etc...



Edit:
Since people have differing opinions below....
Caviate #1: There is an error rate present in the tach needle's interpretation of the analog signal from the ECU, generally the needle running high.
Caviate #2: The 500rpm per 10mph is the approximate number for the series 1 transmission and series 1 final drive of 4.444. This number changes with the Series 2 transmission, which has taller gears 1st through 5th, a shorter 6th, and a taller final drive (4.777).

 

mine sits at 4000rpm at 75mph I have never paid attention at 70mph

 

Mine sits between 3,500 and 3,600rpm

 

about 3500-3600
I know at 80mph Im at 4100rpm

 

Here I compiled some photos for you this morning. I hope you enjoy them.

 

with the s2 trans in my s1 car i am at approx 3.2--3.3 at 65-70---oem size tires.
OD

 

Would the 6-port 6-speed auto be different because I don't remember having that high of an RPM while on the highway?

 

The auto's have a different rear gear ratio. I don't have it on hand, and am not searching for it

 

Yes, 3000 RPM = 74 MPH.

 

I believe that's about right for the 4-speed automatic ( about 25 mph per 1000 rpm )
For the 6-speed automatic, 3000 RPM = almost 90 mph ( about 30 mph per 1000 rpm )

 

With my winter tires (215x55 @ 17) i run at around 3.5 - 4.0 rpm @ 70mph

 

Wait. Is this a new Beetle or an old Beetle? You gotta be crazy to put this engine in a new Beetle; new VW chassis have so many parts that are designed to wear out on a regular basis, it really isn't funny.

 

Old beetle....you should check out his build thread before making that conclusion. He even linked it for you.

 

lol

 

4000 Rpm equals 80 Mph on my speedometer, and 79.2 as per GPS.

 

9850 rpm

 

Lol imagine just rolling at 9k @ 3rd gear to maintain 70mph .... so much for engine carbon buildup

 

he didn't specify which gear, that is 2nd gear in mine, hardly breaking a sweat in 3rd@70 mph

 

yeah I was about to say thats second gear lol. 3rd goes past 90. I actually thought about doing that then I remembered about mazda denying new engines if you did such things since they read these.

 

Aha, well, looks like I have something to test out on my way to work tomorrow

 

My 07 6spd auto ran about 2425 @ 70 mph.

It now runs about 2500 after shorter 225/40r18 tires.

 

6MT speed-to-RPM chart (2003-2008 models)


You're welcome guys.

 

My car is at 2400 at 70 mph.