Go over 150 MPH on the Bonneville Salt Flats with a stock-bodied (but lowered) '53 Stude powered by a draw-thru turbocharged flathead 6.
Though there is no record in XO/BGC, we are expected to go about 150+ mph. The XO motor to beat would be a GMC 6 since it is the biggest thing in the class at about 300 ci, and has overhead valves. We want to see what a stock flathead is capable of, so we will set our goal as >150 mph.
Weight, Frontal Area, and CD
Using the Ray Hall calculator: http://www.turbofast.com.au/ We can calculate the horsepower generated with the following parameters:
To get the 74% adiabatic efficiency, we used the compressor map for a T3 "60" trim compressor section. The TO-308 used on the 79-81 Buick Turbo Regal has a compressor wheel measures 2 3/8" exducer, 1 13/16" inducer and appears to be comparable to this map. The compressor housing is stamped .60 just inside the outlet. If we are correct, at 15 pounds, the plot puts the efficiency in the highest "island" if the V.E. is over 55%. The compressor will be spinning about 117,000 rpm. The turbine housing for the earlier Turbo Regal is 0.82 A/R. Neither turbo was marked, however, I believe this is the correct number. Measuring the size of the orifice at the inlet of the scroll showed it to be about 2". The center of the orifice to the center of the turbine was about 4". The A/R would then calculate out to:3.14 x R x R = A = 0.785 which is close to 0.82. The larger A/R scroll was abandoned on the Buicks to improve the lag situation, but this would have to be at the expense of the greater power supported by the bigger scroll. Our application be at a predominantly high rpm, where, I believe, this particular turbo is quite efficient. Spool-up should not be an issue on the Salt Flats, as this will be occuring at a time when we don’t particularly want a lot of power in a low traction region.
The draw-thru set-up which was stock on the early Regals was a poor design for a daily driver used in all types of weather. Gas pooling was a problem in practice, but for Bonneville, with an ambient temp of about 80 degrees F, this is a non-issue. The simpler design, and the fact boost possibilities are greater in an unpressurised carb, make it a natural for our combination. The Ray Hall calculation indicates that the turbocharged CFM may be as high as 403 cfm. I expect that we will have plenty of Rochester Quadrajet available for that purpose, and may even have to add a restrictor plate, or radically adjust the secondary side for less flow.
Tom Porter felt comfortable spinning this motor to perhaps 6100 rpm. It has forged pistons, Forged rods, forged crank, a good windage system (stock) and a high output oil pump. Using: http://davewin.com/tech/mean_piston_speed.shtml At 5185 rpm, the mean piston speed is 3780 ft/min. At 6000 rpm it would be 4375 fpm. Optimally, one should probably stay under 3800-4000 fpm or, in our case, 5485 rpm. At Bonneville, the "seat of the pants" rule is to discount about 15% , so 5185 is a good working rpm down from 6100.
To calculate approximately how much horsepower is needed to push our car up to about 150 mph, we assumed that the car with fluids and driver would weigh in at about 2900 pounds. A stocker is about 2700, but with less gas, less interior and about a 200 pound driver we are up around 2900. A conservative cooefficient of drag would be 0.35 and frontal area with a drop in the body is about 22 square feet. Using the calculator: http://www.prestage.com/Car+Math/Gear+Ratios+and+Tire+Sizes+/Calculate+MPH/default.aspx one finds that to achieve 150 mph, one needs about 189.7 hp to reach 155 mph one needs about 208.6 hp. Above, our calcs indicated that if V.E. is 55% at 5185 rpm, the engine will be putting out About 190.7 BHP. This at least puts us in the ballpark. The engine may make quite a bit more than this depending on the boost level possible without detonation and the real V.E. which is yet to be determined. A V.E. of 70 would yield 243 BHP at 15# boost. Same V.E. at 20# would give 310 BHP at 6000 rpm (maybe next year……)
Aerodynamic HP Calculations by Bowling and Grippo
http://www.bgsoflex.com/auto.html Input Parameters Are the Following:
Computed Rolling Horsepower required is 67
Computed Frontal Lift Force is 95 Lbs.
Adding the aerodynamic hp and the rolling hp will give the total hp used to get to 150 mph
171+67= 238 hp (Not sure if this is BHP)
The car should do 143 at 5185, 152 at 5485 and 165 at 6000 rpm
http://www.bgsoflex.com/rpmmph.htmlThis indicates that if we are able to make horsepower, it might be worth having a numerically lower rear ratio with us. A 2.8:1 would give us 153 mph at 5185 rpm. Going to the 26" tires in back would give us 134 mph with the 3:1 if power was down significantly from what we are predicting, and need more ratios.
Using the following formula:http://davewin.com/tech/longitudinal_cg.shtml and assuming the wheelbase is 120", for a bias of 51% front/ 49% rear (Hart’s Stude)
55%/45% CG is 54" behind