Speed Ventures this weekend at California Speedway

[sdcat]

I'll be at California Speedway this Saturday with Speed Ventures. They are also having an autocross in the parking lot - only $80 for all the runs you want, and you don't have to work! I'll probably just do the big track.

http://www.speedventures.com/events/eventdetail.aspx?id=230

Would love to see another seven or two.

Justin

[sdcat]

Go Navy!

[moosetestbestanden]

Looks good Justin. ALMS ("sportscar") course I presume. Did you get any times?

[sdcat]

It was the "ROVAL." My best times were in the 1:58's. I discovered early in the day that my car tops out at 105. I'm at about 6500 rpm in 4th gear at 105, still not at the rev limiter. If I shift to 5th it stays about the same speed. So from half way down the track on the big straight, I'm at 105 all the way around the bank to the next turn. Watching everybody go by me that I just passed in the infield! Even Miatas, which seem to be able to do about 120.

Of course, my speedometer may not be accurate, but the fact that stock Miatas are walking by me like they're muscle cars makes me think it's not too far off. I had the same experience at Big Willow. A friend with a stock Miata would gain about 50 yards on the straight.

After I became resolved that this was my fate for the day, I had fun catching and passing in the infield. The car is working beautifully. Brakes, handling, even the engine (although not as powerful as I'd like) ran wonderfully.

Justin

[slomove]

I don't know....either you engine does not push as much power as it could do or the gearing is not optimal.

I think I mentioned before that my top speed was 129 there but I guess that was keeping on top of the oval for most of the time and then diving into the final curve of the oval. That was the only way of getting by some faster cars who put already the foot on the brake at this point.

For comparison: same engine with 13" wheels and 4.11:1 diff. I have a semi-close gearbox but 4th and 5th are the same as the standard box. Also I typically take the engine to about 7000rpm before shifting. Don't know what else may be different...

Gert

[sdcat]

I usually shift at 7000 as well (right at the rev limiter). I'm not sure if different gearing would help, since I've maxed my speed at 6500 rpm in 4th gear, which should be at the peak of my power curve, and below the rev limiter. I'd think that if I could pull more speed, that's the rpm I'd want to be at. The dyno from the original engine build showed power not falling off at higher rpm. I didn't notice what rpm I was at when I shifted into fifth, so maybe a lower fifth would help.

To start with, I'm going to get the car on a dyno soon and see what it's putting out. I'd actually be thrilled if it was much lower than I had thought, which would mean I'd have some room to tune.

At the current power level, I couldn't help noticing that the car still gets around the track quickly, had no oil starvation or overheating issues, and the car just didn't seemed stressed at all even in the August heat. This is nice coming from a heavier car where I'd always come in with an overheated engine, transmission, and tires, with brakes smoking! It almost made me think I should just leave it as it is, but I'm sure that won't happen!

Justin

[slomove]

........ the car just didn't seemed stressed at all even in the August heat......

What do you mean "August Heat"? Stan and I drove back from Monterey today and all morning along Hwy1, I had my fleece on plus wind breaker and gloves. Was something like 60 degrees and foggy. Only took it off at lunch time in Los Alamos. But very light traffic and a fun drive.

The good news for your car is that even even if you are not satisfied with the engine you are still faster around that track than I ;-)

[moosetestbestanden]

I can't pull top revs there in 5th either, w/ 13s and a 3.62. Measured RWHP a buck fifty. I usually shift to 5th somewhere just past S/F line and the revs climb (verrry) slowly until they don't anymore. Then in turn 2 the revs drop to about 5500 which is a result of increased resistance at the tires due to the tightening radius.

Aerodynamic brick syndrome. W/ that as the limit (until more ponies arrive) the fastest way around is to stay as low as possible all the way around the oval as it's the shortest possible distance. At the exit of 2 I let the car drift up towards the wall prior to braking for 3.

Pity you couldn't come out the previous weekend. That would have made 4 of us.

[Elv15]

Chris,

What is the top speed you've reached with your current motor?

[moosetestbestanden]

I'm not too sure. I seem to remember seeing about 130 +/- on my GPS device at Cal Speedway last year but...

This year I was pulling about 6200 in top gear. That's w/ 13's, a 3.62 diff & whatever ratio 5th is - I'll have to look it up before I can do the calc. If your box is a 5 speed from SPC it's likely we have the same gears. Do you know?

[sdcat]

I took the car in to be dynod this week. When the engine was first built, it put out 163 RWHP. We first did leak and compression checks, which it did well on, but on the dyno is putting out much less power and running very rich. After some tuning, they were able to get it back up to 150 HP, and they will fiddle with it some more next week.

I've noticed that on the Caterham site, even the cars with 1600 cc sigma engines with rated 150 HP are supposed to do 125 mph. I've got my fingers crossed - maybe with some better tuning I'll have a better time on the straights!

Justin

[slomove]

I believe the standard T5 and the Quantum Mechanics semi-close version have 0.825. The Quaiffe semi-helical is said to have 0.87 and I have no idea about the SPC version.

[Doug Liedblad]

SPC semi helical has .87 fifth gear.

I've read on Blatchat that the gears are made for SPC by Quaife.

Doug

[moosetestbestanden]

Because I can't install any executables on this computer (and thus can't run gearcalc) I've used this here and w/ a guess at the diameter of the slicks I'm using and a 1.00 5th gear value it returns 130 mph at 6200 rpm. The car (well, engine really) in it's current form will not pull any more than that. So let's just call it 130.

Everybody (like box stock new Camaros - ugh) but the Miatas and the Honda racecars blow by me on the oval. Until it comes time to put on the brakes that is, whereupon they come back to me pretty rapidly.:D

Edit: For the record, my current engine dynoed (on a 90 deg. day in Fontana last year) right at 150 rwhp

[GWise]

Justin,

Looking at that Dyno plot..you should be much better off now- Seeing has how it was dropping all the way down to 120hp at 6500 RPM. I agree with Gert though- I would think adding the compression would really help those cams. I also wonder how accurate the dyno is as I know they will vary.

I was thinking about this thread while looking at the top speed thread on usa7s.com. By going to the wider slicks you have on the car, you've probably added another 1.25-1.75 sq ft of frontal area to your car - Not only that but the tires themselves probably have a Cd of close to 1 or more, especially since they create turbulent air. The FIA roll bar and mirrors likely don't help either, though it's good you've gotten away from the barn door windscreen.

http://www.bgsoflex.com/aero.html

Using this calculator, I used .7 for the coef of drag, 18 for the square ft (assuming you've added about 2 sq ft, total). 100 deg F, 30 in Hg, 105mph, 1200 lbs, tires inflated to 20 psi, and .1 lift. - I get about 92 horsepower. Keep in mind, this isn't exactly real world as it doesn't account for frictional losses, etc. Let say you remove the headlights...which are about 2 sq ft by themselves, that should give you about 5 more mph (maybe more considering their Cd values are probably closer to 1). If you play with the calculator, you can see just how much more power is required to go faster (138hp for 120 mph, 175hp for 130 mph). I also ran it with a miata (.38 with an 18.5 sq ft area). They only need 97 hp to do 130 mph. It makes you really want to reduce the drag as much as possible.

Very interesting though - My car should have a lot more drag (clams and full windscreen) and only makes about 100 hp and I can do about 100 mph.