Top Speed Question

Oh Haha · 05-08-2004, 06:45 PM

I have been fine tuning the 911 since getting the engine and trans back in. Here's my question: I may have accidently took the car up to 250 kmh indicated on my speedo. Converting to mph equals around 155! Is this possible? Car felt smooth the whole time. The only change I made to the engine was replace the plugs. AC R42 XLS seem to be working great. (GM plugs are cheap here!)
RPM was 5400.
Thanks for the comments and feedback.

Yes, it was on a deserted road, no traffic or houses.

Gratuitous picture, of course.

RarlyL8 · RarlyL8's Garage

Pretty car.
It is doubtfull that you were doing 155mph @ 5400rpm with a 915 tranny unless the gearing and engine were both modified. I hear the stock speedos were a bit optimistic.

My '78SC with stock 8:31 gearing would only pull 140mph at redline in 5th gear.

turbocarrera · 05-08-2004, 06:52 PM

check the transmission chart in your owners manual.. provided you have the same gearing and tire size, you can just look from the y-axis @5400rpm, move over to the line for the gear you were in, and down to the speed you were travelling.. more accurate than the speedo

Oh Haha · 05-08-2004, 07:02 PM

Thanks guys. I forgot to mention that the speedo was calibrated last week. I don't have the manual but I thought that 155 might be a bit optimistic. Sure was fun, though. These are such a hoot to drive. When all is working well together it is a blast just driving at normal speeds.

1982911sc · 05-09-2004, 05:30 PM

Hey,
Where were you when you topped her out? Just curious as to where you would try 155 (or 140) in our home state. I have a few ideas if I was going to myself but just curious.

azasadny · azasadny's Garage

I'm in Michigan and would love to know your "secret route" so I could try it!!

carmad · 05-09-2004, 05:57 PM

When I visited my in-laws near Munger, there are some very straight roads around the potato fields. They are in good condition and you can see for miles. I had my mother in law, niece and nephew in the back and did 145 mph, they loved it.

David · David's Garage

I didn't really want to start a topic on this but since someone brought it up, I had a conversation with a friend on Friday that I'm dying to post.

This friend has a modified 996TT and he said he got close to 200mph the other day on I-10! Obviously this is not very smart, but I trust this guy completely and except for speedo error, I don't doubt he did it. Did I mention that the 996's are growing on me? Now where did I put that extra $100K?

Oh Haha · 05-10-2004, 06:37 PM

Ok guys, you need to make a trip up north. I work around the Bay City area and travel alot for my job, although not in the Porsche. I am always on the lookout for good driving roads. carmad is pretty close about the Munger area. Great roads with little, if any, traffic. My in-laws have a place near Oscoda and there a Ton of great driving roads as well.
We all know that exceeding the legal limit is against the law but yet we still do it when given the chance. WOO HOO!!

Jim Sims · 05-10-2004, 07:00 PM

At 150 mph a car has 4 times the kinetic energy that it had at 75 mph. If you hit anything of significance (like a dog) at 150 mph the results will be catastrophic for the dog, the car and you. Think about what you risk.

Find a track. Jim