Hey everyone, love the forum. It's like instant access to a whole crew of experts all around the globe!

I've got a question about the top speed for my car. I've got a 2000 996 C4 Cab that is all stock, no mods.

I was at Watkins Glen (my favorite place in the world) for a DE over the weekend. On the back straight, I was in 5th gear and the rpm's were nearing redline at 135 mph. I upshift into 6th and noticed that my rpm's went down to just under 6000. I got up to 138 before I had to brake.

I thought the top speed was supposed to be 178 mph? Could there be a 155 mph governor on the car I didn't know about?

Thanks for any ideas. I hope there's nothing wrong with my car.

Phil

 

well i believe the c4 is actually 161 top speed for some reason, ive had my 99 c2 cab to indicated 178 but the gps said 173 and it was still pulling but i was running out of nice desserted road

 

Well, you ran out of room before you could hit top speed. Just because you are on a race track, it doesn't mean you can reach top speeds. You probably need another few hundred yards to get there.

 

Wow ... you must be movin pretty good through the Ess's ... doesn't that just feel like heaven??!!

I've never had the nerve to look just before I brake to go into the bus stop, but I have seen 135 mph not too far from the braking point. My speedo is off by about 10 mph {at that speed}, so that's 125 which seems to jive with the GPS which says 128 is my top speed {ie I picked up a couple more mph before I hit the brakes}. BTW, my best laptimes are about 2:27, this is in my 99 996 {the track car} which is totally stock with street tires {S-03's}.

I have never hit top speed anywhere. I once had my 01 up to 145 but ran out of empty highway, it still felt strong like it was ready for much more.

 

Viken, sorry, I didn't complete my thought. My point was that I thought 178 was top speed. And, given my rpm/6th gear/138 mph, I didn't see anyway I could squeeze another 40 mph out. So, I started to question the 178 top speed.

Pete, yep I was flying through there. Exited at around 120 or so. Looking back on it, Heaven is a good approximation. Though, at the time it was a little too terrifying to be Heaven

I'm on street tires, too, and I just hit my best times this weekend. 2:25 was the best, with a whole bunch of others under 2:32. Boy was I surprised when people told me!

By the way, there was a Jagermeister 962 there turning in 2:00 flat lap times. He was in the red run group and just flying past the race cars like they were standing still. In the Esses, no less. He was asked not to run again on the last day for routine "inappropriate passing"!

 

I managed 168 indicated before i had to back off (approaching slower traffic). There was a good cross-wind blowing which made it hairy, but the car remained predictable. Did it this weekend coming back from Monterey southbound 101 before Paso Robles.

 

No speed governors on Porsches, these are not Mercs
My C4 on slight downhill (180mph)

 

Not a specific speed, but there will be a governor on RPM's which will translate into a speed. So I'm thinking the speed that your car is limited to will depend on the rolling circumference of your wheels. If your wheels are a little bigger then your top speed could be higher {assuming down hill with no wind etc}.

Phil, based on the numbers you give ... I would guess you would be limited to 163mph. This assumes a rev limiter set for 7,250 {which is my guess based on my 99 ... no idea what it really is} my math: {(135/6000)*7250=163.125}

 

Besides not having "speed" governor/limiters (like the 155mph on MB/BMW that he mentions)... the RPM limiter will not limit top speed either since you can't hit the rev limiter in 6th gear, if you look at my video grab I'm only hitting 7k RPM at 180mph already (stock wheels), so the RPM limiter has nothing to do with top speed limiting, unless you fit a Cayenne set of 20" wheels

In that slight downhill straight were the pic is from I was doing already 150mph in 6th gear when hiting 6000RPM, but then mine is a coupe.

 

A stock 996 can get close to 150MPH before braking at this spot. Maybe 145 with the cab.

You'd need another half mile to see north of 160!

 

Carlos, Sorry I know I'm being a pain, but if {theoretically} you did fit a set of cayenne 20" {275/40R20} wheels on a 996, that would lower the RPMs at given speed. So down hill with no wind you are certain to hit well over 200mph!

 

well since atleast 2 of here have gone over 170mph pete im not so sure your math and a topspeed of what was it 163? really apply

 

Hey Phil,

I was there too...in fact I think you relieved me on Saturday afternoon at the front gate so I could get my run in? Thanks again, even though you didn't have to stick around. That Jager car was unbelievable. Small world.

regards,

 

The numbers you posted seem the indicate different gearing for your cab than on the standard 996 which I don't think is the case. There's no way you should be as high as 6k at 138 indicated (porsche's always read high). Also the cab probalby has a slightly lower top speed due to more drag.

 

The straight at the Glen is rather short for top speed runs. It also is an uphill climb through the esses before the straight. To give you a comparison, I run down the chute and shift into fourth then turn into the esses. I climb through the esses and shift fifth about midway through the left as we crest the hill. I accelerate fifth out almost to the redline, somewhere in the 150-155 mph range before the bus stop. This is in the neighborhood of how fast you can get my car on a track. Pocono full is a little faster at abotu 160. I did not get to do Pocono Nascar style, but with the full bowl, I could probably 10 mph faster. These speeds are lower than what the car is capable of, but you simply run out of track. Also keep in mind the entry speed on a track is key. Entering the esses 10 mph faster will make a huge difference at the end of the straight. Do you keep on the floor after the right turn into the esses or do you modulate your throttle? Other factors like aerodynamics come into play. The setting on my rear wing is supposedly worth 2-3 mph, you convertible top up verses down is probably worth 10 mph. Even open windows come into play.