Ok, let me get 2 things clear first.

1. I’m not Dr. B with a beautiful car, BriGuy or Sith with the ¼ mile performance, Eagle1 with on-track destruction of Z06s and such, or even GQ with ridiculous turbo experimentation.
2. I know that this is a G-tech. Please don’t take any exact figures literally.
3. This is gonna be a long post.

That said, I’ve been wondering for a while why the BMW M3 cuts a full second off the Z car’s quarter mile time. Sure, it’s got 46 more rated horsepower, but also around an extra 200 lbs to drag around (I think some of the M3 models can have a lot more than that). Oh, I’m talking stock here too. My Z can show up at the track with 300 lbs less than it showed up at the dealer with. But that’s not the point.

The NHRA has formulas in which you basically input horsepower and weight and you get your ¼ mile time out of it. With a 180 lb driver in each car, the M3 has about 10.7 lb/hp. The Z has 11.7 lb/hp. And for fun, the C5 Z06 has 8.14 lb/hp and is a second faster than the M3! I don’t actually know what any of this means, but I think the M3 shouldn’t be that much ahead of the Z.

However, as I was testing with my brand new G-tech Pro RR (in, uh, closed tracks with professional drivers and all that, certainly not about 6 miles north along 277 at this bridge that is exactly a ¼ mile long). So, I put the numbers on the computer, had it do its horsepower and everything analysis and I saw this.

(Note, the black line is a pull I did through 2nd gear just to get the whole curve. The Red and Green lines are ones that the G-tech selected to calculate HP. The RPMs are measured through the cigarette lighter, so they’re consistently off- say, 300 rpm. However, I’ve compared this output to many online dynos and the shape is the exact same.)

 

Ok, notice that we have in this motor, a nice long, flat torque curve that goes from 3700-5000 rpm. Beautiful! Great for passing on the highway. Now, notice that both 2nd and 3rd gear begin AFTER the curve falls off when running the ¼. DOH! From what I understand about drag racing (that is, not much), you stay in the lower gear as long as possible, even though the torque curve falls off, you still get more effective torque through gearing.

From this graph, see that 4th gear starts even higher than 2nd and 3rd (~5400 rpm)!

 

So, for this car running around a “13.9,” 2nd is 5300-6600, 3rd is 5000-6600, and 4th is 5400-wherever. The point I’m trying to make is that everyone racing his or her car and wondering why they don’t bring home the greatest times is cause Nissan handicapped the Z to keep us from breaking it. The only time you spend in gears other than first is when you get less than optimal acceleration. In any gear, the best acceleration in that gear somehow relates to making torque in that gear.

To change this curve’s shape to make it look like a Porsche or Ferrari (similar size engine, tons more power), I think the two most beneficial types of modifications are head work (P and P, valve job) and cams. The problem is that these are some of the more expensive modifications out there/ you could buy a Procharger for a little more than these two together. So, this kinda scraps the desire for anyone to make a monster NA Z and it keeps us from getting rid of the damn V8 trolls in the street racing section. “It’s not fair if the Z is using N20, S/C, TT, etc.”

Ok, back on topic. I’ve modified the curves to show what it would look like if you could keep the torque curve flat, or even just from dropping off so ridiculously and I raised the redline to 7100 too. This is how Ferraris and Porsches make power. And I also bet this is how the M3 does so much better than the Z in the quarter. It actually makes the power in the RPM band it’s using. Then again, if I dropped $20K into a motor and it only made 333 hp, I’d be pretty upset. So upset that I wouldn’t be able to enjoy my nice BMW and have to come bother the pretty Z cars about it all the time

 

Also, for kicks, I drew a picture of an S2000’s dyno as well.

(I don't know why the pictures don't work, but they aren't so interesting that you can't go without them.)

 

Is the way the cars geared a factor?

 

Is the way the cars geared a factor?

 

If you save your pics as JPG or GIF, that will fix your problem (as long as they're not too big).
--
Jeff

 

Hmm... the new 2005 Track model will have

300hp/260tQ, 7000RPM redline. I wonder if the 260tQ will stay relatively flat to 7000RPMs and what the 0-60 and 1/4 mile will look like

 

The only problem with that is the torque peaks at the same 4800rpm...so one can assume it rolls off in a similar fashion on its way to redline.

The higher redline will probably shave a tenth and the higher HP will read as a higher trap speed in the 1/4.