Happy B-day to me! Got some F-off time and this is what I am enjoying this morning.

I have been playing with my rig on the computer. I was recently spurred by Conanski to upgrade to Desktop Dyno 2003 from 2000. I also got Drag 2003, found a good spreadsheet to see shift points and a speed/rpm calculator to choose shift points in my Tweecer tune. While I might think I am Ricky Racer, I am not but this is what I have found.

I found a most cool spread sheet to look at shift points, torque and horsepower. I used my DD03 dyno output to complete the spreadsheet and used the spreadsheet and MPH/RPM calc to reprogram my shift points. MPH/RPM calc: RPM/MPH From Gear Ratio Calculator by Wallace Racing



Inputs, torque in each gear at tranny output:


RPM after shift


Torque at tranny output shaft vs engine RPM:

 

What this spreadsheet, Desktop Dyno 2003, and Drag 2003 taught me or reinforced, is that you want to shift at red line to get the most speed, best time over a distance. Nothing new here but it illustrates that fact well. If you look at the torque output at 5,600rpm in 1st VS. hitting second, at any RPM, there is a huge difference in power! The same goes for staying in second as long as you can before 3rd. The spreadsheet allows you to play with different transmissions or gear ratios to get the most out of your power/engine build.

 

The second thing the spread sheet reinforces is the fact that the more power you have at higher rpm and the longer the engine will make it, the faster you will cover a distance. This is why cams selected for drag racing make more power up high and into higher RPM. DD03 helps you build to get the most power and Drag03 lets you simulate what differences in gearing and build can make in elapsed time.

The cam I am using, left over from my rock crawler, makes great torque down at low rpm and drops off at high rpm. I used a gear/speed calculator to choose shift points. Here: http://www.wallaceracing.com/gear-speed.php When my rig shifts, at 5,500rpm, it was putting out 1,160ftlbs at the tranny tail shaft (from spreadsheet). That's 100ftlbs less torque than whats available at 2,000rpm! It is picking-up 2nd at about 3,150rpm (from spreadsheet). So I am missing the great torque the old, go slower, crawl cam make down low! A similar thing happens from 2nd to 3rd, it's hitting 3rd around 3,600rpm. Now all the power is there on launch, cause it's got to climb through the rpms, from launch rpm of about 2,300, but it's too much for my tires to grab. It's wasted down low, kinda feels, looks and sounds impressive but it ain't moving! My shift points are a bit conservative, which means I could go a bit faster, red line is about 6,500 but I want to keep this thing together and the torque does drop off.

I am going to back-up a bit and post my current DD03 output and Drag03 simulation. Then I will post up the output for the same build with a better cam and tires for lower times from point A to B. I checked DD03 against stock engine outputs and it is accurate.









"Wheel Speed" is greater than rig speed down low, what's that all about?

 

The power output utilizing Crane's 220 cam, note the higher rpm power:






Shifting spreadsheet with Crane 220:

 

Same build but with Cranes 220 cam and added performance street tires for better grip:



Much less wheel spin!


The Desktop Dyno 2003 Software has been awesome to play with and relatively inexpensive. Cheap when you consider the help it gives and the mistakes it might keep you from making with a build. I highly suggest it as well as the Drag simulation. You can download a demo for free then activate for a fee.

Note: I don't have tires to go that fast, nor the injectors to support that cam, nor the proper flowing Kenne Bell Blowzilla intake, and I would likely have to upgrade the fuel lines, plus a cage would be in order to run that fast. I'll stick and work with what I have a bit.

I am intrigued that Drag03 shows that if I add better tires to minimize wheel spin, it would drop to around a 6sec. 0-60 and 14.6sec 1/4. Just Tires! I can't launch now at full throttle without wasting tires.

Any questions?

 

Great info there Swat....ummmmm Blown349!