I totally hear what you guys are saying and that is why I posted here. I know that I know a lot about racing/building motors etc and that I don't know sh*t about the salt.
Just a few quik replies/thoughts:
Knowing more than they did, I proceeded to ventelate pistons for two years until Marlo convinced me to fatten the jet by .030. The car sounded great and ran up through the gears like a banshee, just like a drag race motor should, but then it would get these inspection ports in the pistons. Handy for checking for debris in the pan though.............p.s. Marlo's jet got me an instant 34 mph with no holes!
One thing I haven't considered is my choice of fuel management/data acquisition vs the rules. The EMU I have chosen has real time w/o the need to hookup to the laptop to modify fuel/spark/AFR etc. The Halltech has the ability to let you set up specific scenarios and then modify the system with a preset remedy. For example the fuel pump controller will boost fuel pressure X number of PSI per LB of boost, retard/advance spark as rpm/boost changes, duty cycle etc with real time wideband afr monitoring etc. I do not know if this is acceptable under the rules.
Your mention of 1000+ hp indy motors just won't get it on the salt where you don't have the traction of asphalt and mile wide tires. You will be running on tires that are about 5 inches wide and will have 70-90 lbs. of air in them and the salt on a good day has the coefficient of traction of about .4 that of asphalt. Ask Johnr about running a high hp full power/no power small motor. He has done it successfully, but to get one of these to hook is a chore. Forget HP at b'ville. One of the better things I ever heard came from Jack Costella during an interview. He said "you need a truck motor, something that can pull a long hill as running on the salt is a long hill to climb" or something to that effect. You need a torque motor. You are in the gears for so long there. Plot your speeds with a rear gear that you will need to go 260 and see how long you are pulling the high gears.
I was hoping that having AWD gives me double the traction of most of the vehicles I would compete against therefore giving me some advantage to compensate for the additional parasitic losses. Besides big power the car is projected to make almost 800ft/lb of torgue which gives it some pretty good grunt with a motor that spins 9250RPM @ the power peak. Air consumption is nearly 125lb/min under boost.
The chart you posted on the other post is a guide not something written in stone. How do you know the exact Cd and area of your car after you have made the purposed changes? Is that HP at the crank, rear wheel?? Is the HP at the exact RPM you need it to be there. An example we have the dyno numbers on our car and this year ran an exit speed of 241 at 7070 rpm and the rpm was about flat there and we only picked up about 3 mph in the whole last mile, so we are at the limit of this configuration. But the Dyno says we should be making max HP at 7400 rpm, so why can't we pull that? The reason is that the difference in HP between 7000 rpm and 7400 is only 10-20 hp and the HP needed to run 253 (7400 rpm) is 100 HP more than that needed to run the 241 that we ran. So even though the motor makes more HP at 7400 it isn't enough to run the 253. See how critical the gearing can be. Gearing (all gears) is just as important, in my mind, as HP and aero to get the job done if you are going for the last mph for your combination. We are now looking for a 5 speed where we can change evey gear in it (except the 1 to 1 5th) to maximise our effort. We need to as we are not running a good body for our class.
Chart entails rear wheel horsepower plotted vs Cd X Frontal area vs speed. It does not take into account tire friction vs road surface. I was planning on using air density, road/tire friction, and coast down to determine the new Cd after any mods. Fluid dynamics(which I understand and have the math skills to calculate) would provide a pretty good ballpark of the effect of the changes. Gearing has been considered as the 6 speed gear case from the STI is converted with straight cut gears, non synchro'd, and all 6 gears are changeable. The R180 differentials were used in several high HP imports and a variety of gearsets are available as well as the center torque splitting differential having the ability to send a varying amount of torque to the front wheels at the drivers whim.
You are talking about the HP to go certain speeds. Have you figured the weight needed in the car and where you will put it to get the traction needed to get that HP to the ground to reach the speed? At about 230 we were out of traction with our 3000 lb. car. We had to add over 800 lbs. to go faster than that and run the 241. But now that has hurt the acceleration of the car so we need more HP to accelerate faster and more HP to go faster and we will probably have to add more weight to run over 250. There is a lot going on that is very hard to just figure on paper. If you try and add traction with a spoiler now you have hurt the aero of the car and will need more HP to fix that. Also you can't just dump the weight over the rear as then the car won't go down the course without spinning. You probably have read about "center of pressure" and "center of gravity" and how they can work to make the car go straight.
Again I'm hoping that the AWD will negate some of the traction issues. I've had to ballast and cornerweight my drag cars to compensate for traction/drag/air stacking under the front end at speed. The car does have the benefit of the boxer engines lower center of gravity than other engine configurations. I might go more later but other engagements are intruding on my forum time. Thanks for all the advice!
