Top Speed at the track ?

[Klasik-69]

Hello to everyone. I just bought my R300 superlight last year so I'm on a learning curve, probably always will be. My car is equipped with the Zetec 2.0L with a claimed 202 HP. I have yet to dyno the car so I can't be sure as to how much its really puting out. However, my top speed on the track is around 120. I'm a little bummed out about that so I did some checking. Turns out the Cd of the 7 is similar to a school bus. So I've starting to change a few things. I changed the big bug-eyed headlights for some smaller 3.5" units. Next, I'm getting rid of the windshield & replacing with the R500 windscreen. So I was curious as to what kind of top end you guys had and what powers your cars to get that.

 

By the way, I'm running a 5 speed tranny and running on 15" Miata pattern wheels. 5th gear on the track is useless since the car will actually slow down in 5th, which may indicate the rear end ratio is too high, not allowing enough revs.

[WestTexasS2K]

I've hit 132 at TWS 240 hp Ultralite. 7evin has done 160 at VIR long course about 400hp. John Meyers 169 at VIR he was running about 500 hp v8. It takes a lot of hp to overcome the poor aero of a seven.

[snookwheel]

It will be interesting to see what you gain with the changes you make.

[Croc]

Next, I'm getting rid of the windshield & replacing with the R500 windscreen.

 

 

Getting rid of the windscreen for an aeroscreen (I think that is what you are changing to?) makes a huge difference especially over 100mph. The car definitely feels more responsive with an aeroscreen on. I swap my windscreen to an aeroscreen once I get to the track. The windscreen is nicer for avoiding bugs, stones, etc.

 

I find that the tracks I drive dont allow me enough straight to get to max speed. I have GPS data logging showing me I have reached 131mph whereas the speedo dial was reading 141-142mph at the time. So your 120mph may not have been a true 120 if you were relying on the Caterham speedo?

 

In theory my car can make 155mph at redline 7500 in 6th but I am yet to see it. I believe it can get close to 150mph as I am still accelerating strongly at 130mph when I have to throw the anchors out to brake for the next corner. My engine is a Duratec Cosworth 275hp.

 

I drove a UK spec R300 2L duratec SV race car at Silverstone GP circuit last year which was making a claimed 195hp (probably what yours is really making). I was able to hit redline in 6th gear on the longest straight which translates to about 135mph. If you have the standard T-9 5 speed in your car then your 4th gear matches the 6th gear in the Caterham box. So if given enough straight you should be able to match my Silverstone speed.

Edited January 24, 2012 by Croc

[Kitcat]

Fastest so far in my Duratec powered Birkin is 118 mph (per gps, not crap speedo) w/600 rpms left til redline in 5th (6800 rpms). So theoretical top speed is abt 128 mph. This was w/lights, windshield etc. And, on a tight track. I suspect I can hit redline at a bigger track, like Mid-Ohio. Top speed isnt really these cars' forte tho.

[yellowss7]

I run 13 inch Hoosiers on my 195 hp (flywheel) Caterham with the 6 speed box. 3.62 diff.

 

I've pushed it to about 7000 rpm in 6th, which by my gear calc spread sheet is 120 mph. Still have 1000 rpm left to red line. I certainly cannot keep up with Croc and Karl with their almost 100hp advantage even though they are driving big fat bastards. :jester:

 

Tom

[Croc]

Fastest so far in my Duratec powered Birkin is 118 mph (per gps, not crap speedo) w/600 rpms left til redline in 5th (6800 rpms). So theoretical top speed is abt 128 mph. This was w/lights, windshield etc. And, on a tight track. I suspect I can hit redline at a bigger track, like Mid-Ohio. Top speed isnt really these cars' forte tho.

 

I think you are understating your car here. Looking at the NJMP video on Thunderbolt main straight shows you ahead of me maintaining gap when I am in the 123-128mph range. This is from the RaceChrono GPS datalogger in my car. I think you will be more like a 135mph top speed?

[KiwiBirkin]

If you want top end speed at the end of the track then change to a areo screen which you have done, but really are you worried about it that much ??, these cars are all about the corners and that's we're you will win over nearly every other car on the track and have the most fun.

[jimrankin]

Pull off your windshield, your lights, your fenders and wax your helmet, it will make you feel better but won't gain a whole lot. Just our "7" lot in life. LOL.

Even when adding, or starting with more horsepower a "7" is going to start losing after about 100-110 MPH to anything with a low CD. That means we are going to be seriously losing top end to just about every other car at the track.

Be Happy! Think of the shorter tighter tracks where you are going to kill everything except full on race cars! And on the longer tracks think about carrying speed late into the brake zone as if your set up properly not much but a mid or rear engined race prepped car is going to out stop you. The heavier high powered cars can't put all that power down till they are "straight" enough so it's all about you keeping the right line and powering on quicker where it's the "slow" part of the track to everyone else . Nothing pisses off someone who passes you down the straight at 140+ in a Big $ car like getting a blue checked flag or seeing you stuck to his bumper four corners later.

It's even better when someone like RNR does it because (no offence RNR) I don't think he's washed it since he bought it. I'll bet he's caused more than a few driver of "polished $$" cars to delete that corner sequence off their GoPros. "you got passed by THAT" !LOL.

[rnr]

It's even better when someone like RNR does it because (no offence RNR) I don't think he's washed it since he bought it. I'll bet he's caused more than a few driver of "polished $$" cars to delete that corner sequence off their GoPros. "you got passed by THAT" !LOL.

 

When I choose between washing and driving I'll take driving every time.

 

Plus you can only see the dirt while standing still :driving:

[hoefi]

 

...I just bought my R300 superlight last year....

 

I'm a little bummed out ....

 

I see in your signature that you own (owned) a Z06. I also own a Z06 as well as a Caterham. I track both of them. The truth is that, on a track, the 7 will not be able to stay with the current generation of supercars. It just doesn't have the top speed. And the "big" cars are no slower in the corners either. I have always said that if there is price money for the fastest lap, I will be crazy not to bring the Z. The two cars have different personalities. Accept that and just enjoy the way it drives, regardless of what the top speed is.

[pi7ot]

104.6 MPH in fourth in a stock zetec powered Birkin.

But a 10 second faster lap time than my M3.

 

m

[Kitcat]

My '08 M3 was (much) faster than my X-flow at the track. I sold the M3 after 2 years tho, because the Cat was so much more fun to drive. Then sold the X-flow for my Duratec Birkin to try to gain some speed back and keep the wonderful handling.

 

Croc, you were pulling me the last 1/2 of every significant straight at NJMP. Not as much as the event before when I was in my X-flow (Wh/my GPS said topped out at 106 mph), but ya definitely owned the top speed contest.

[DeanG]

About 80 - 85 Talladega BMC 948 bored out to just under 1000cc with 2 large guys and a full windscreen.

[Klasik-69]

Hey guys, thanks for all the input. Many good points made here and a wealth of information.

 

1. We all agree that the 7 is aerodynamically challenged............weird, however, since by looking at it you'd think it was a rocket.

 

2. It is best in the corners............absolutely no argument from me.

 

3. It won't run with the big $ high HP cars on the straights. Yep, that's right. My Z06 at Roebling is good for 158-160 MPH, 1:16 lap time. The 7 is good for 118 mph and 1:26 lap time, but with more practice and better driving, can be improved.

 

4. Higher top end takes BIG HP with the 7.

 

Ok, accepting all the above, I wanted to be able to roll down the straight at Roebling while still accelerating, not just maintaining. I'm not looking to match the speed of my Z06, won't happen. I've hit 175 @ Daytona (and scared the poop out of me). But if I can help the aero of the car a little and possibly get it up to 130, I'll be happy. Some of you pointed out that my speedo may be off to begin with. It is, which is why I use my GPS based electronic track box to base my numbers. Also, as some of you pointed out, my real HP may not be 202 at all and actually be a lot less. It seems all suppliers fudge on their engine's HP, like the fish caught and the guy's .....never mind. HP doesn't mean squat anyway, torque does. I will get the car dyno'd in the next few weeks and find out where the torque curve is. Do any of you recommend paying attention to the rear end ratio ? Jon @ Caterham told me most guys move up to my ratio but some of you seem to have gone to a higher ratio (around 3.65)

 

At this point, I'm waiting for the new non-windshiel windscreen (fiberglass) from Jon since it had to be ordered from England. Once I get that installed, I'll get back on the track and see where I am. Please keep chiming in on suggestions and advice. I'm new at this with the 7 and need to learn as much as possible. Thanks a heap.

[Klasik-69]

Just to clarify a few things about the car. Its a standard T-9 gear box, 5 speed. Rear suspension is the stock R300 with the Dedion rear axle setup and the rear end ratio is around 3.3:1

 

Track wheels are 15"x7" fitted with Hoosier R6 SM6 tires (205-50ZR15). Front wings are custom made aluminum fitted with asphalt dragging mud flaps to keep me from getting rocked to death. Weight of car is 1180 without me.........I won't say how much it is with me. Other than that, its a basic stock R300.

 

Now I'm going in the garage to wax the helmet.......never thought of that before :cheers:

[yellowss7]

 

Do any of you recommend paying attention to the rear end ratio ? Jon @ Caterham told me most guys move up to my ratio but some of you seem to have gone to a higher ratio (around 3.65)

 

On the Caterham 6 speed, 6th is a 1:1 ratio, so no overdrive. Typical diffs for the 6 speeds are the 3.62 or the 3.9. I believe the 3.62 gives a little less accelaration but a little better top end as compared to the 3.9. Tire circumference also has an impact on top speed, as my speeds in gear are less with the low profile slicks vs the slightly larger Avon CR500's or the Toyo R888's.

Not sure about the 5 speed options.

 

Tom

Edited January 25, 2012 by yellowss7

[hoefi]

 

4. Higher top end takes BIG HP with the 7....

 

 

Actually, it takes big power for any car. Engine power is proportion to the third power of speed when it comes to aero drag. This means at the higher speed range, it will take almost 8 times the power to go twice as fast. Once you dyno your current engine, you can estimate how much you will need to go faster.

[Croc]

 

3. It won't run with the big $ high HP cars on the straights. Yep, that's right. My Z06 at Roebling is good for 158-160 MPH, 1:16 lap time. The 7 is good for 118 mph and 1:26 lap time, but with more practice and better driving, can be improved.

 

Ok, accepting all the above, I wanted to be able to roll down the straight at Roebling while still accelerating, not just maintaining. I'm not looking to match the speed of my Z06, won't happen.

 

I've hit 175 @ Daytona (and scared the poop out of me). But if I can help the aero of the car a little and possibly get it up to 130, I'll be happy.

 

Do any of you recommend paying attention to the rear end ratio ? Jon @ Caterham told me most guys move up to my ratio but some of you seem to have gone to a higher ratio (around 3.65)

 

I assumed you had the standard 3.62 diff ratio - my fault. The 3.36 ratio that you have is more for touring. I chatted with people when I was deciding this point on my current car and landed on 3.62 as it was the best compromise. There is a 3.92 but that is going to hold you back on top speed although you should get there quicker but it is a pain for road use. The UK R300 duratec with 3.62 is geared for 135mph area. The 3.36 will gear you higher but as you discover you are running out of track and maybe "oomph" to get you higher. The 3.92 will lower the top speed down to around 125mph - I am guessing 10mph as that was the change impact it had in the spreadsheet for my car.

 

Also going against you is the 5 speed box. 5th is the overdrive so you have just the first 4 gears to really get you going. The six speed box adds two extra ratios to help you keep in the power band. That would help you accelerate quicker to vmax in the limits of the straight length.

 

Roebling is a fairly open circuit that is always going to disadvantage a seven since it has one very long straight where the big cars will disappear instead of a tighter circuit with maybe 2 straights to break up the top speed potential. On your circuit you are always going to have difficulties.

By comparison, at Lightning circuit at NJMP which is fairly tight and has two smaller straights, the sevens group in June 2011 was molesting everything in sight, including several Z06s. This included Kitcat in his old crossflow which is down 100hp from you. By contrast on Thunderbolt circuit at NJMP the more open layout (more straight) allows the higher speeds to come out from the higher horsepower cars.

 

But with aeroscreen, 6 speed box, and higher diff ratio you should be starting to match what I saw in the UK in the same car 135mph. That is probably not enough for what you want?

 

Supercharger time?

[Klasik-69]

But with aeroscreen, 6 speed box, and higher diff ratio you should be starting to match what I saw in the UK in the same car 135mph. That is probably not enough for what you want?

 

Supercharger time?

 

Actually, 135 mph would thrill me spitless. 130 would put a big smile on my face. I don't want to destroy the virtues of this car, that being a very quick corner car in order to get the high speed buzz. You're right about Roebling being a big HP track with the long straight. I also run at Sebring with a nearly as long straight from 16 to 17. I'm going to research the papers that came with the car to see exactly what my gear ratios are. I do know that if I go into 5th gear on the straight at Roebling, the car slows down since I'm going down into a lower power band.

 

What is making this car have such a high Cd ? Is it the wheels sticking out or just the shape of the main body and the lack of low ground effects ? I read on the history of the 7 that Chapman added a full body later on to help with the aero of the car, although with an added weight penalty.