That's an intersting topic. Is a 135 hp 2.8 liter ITA citation X-11 really the same car as a 125 hp ITA 2002 tii? Especially after tuning?
Here is what I think a dyno would tell us.The V6 block chevy pulls maybe 120 hp at the wheels before IT build. maybe 150 after. It gets a lot of help from headers and tuning. The 2002 might be 120 befire IT build and 135 after cause the BMW built it as a performance car.
Because of its displacement, the not great breathing the citation make 130 hp at 4500 rpm after shifting, peaks at 150 at 5500 and is back at 140 Hp at 6000.
The BMW, starts at 107 hp at 4500 RPM after shift making and makes 135 hp at 5500 and maybe 130 at 6000.
Race em together, its the X-11 down the straight, the 2002 in the turns and braking.
Now to your point. even if a 5 liter mustang on the street has the same HP and weight as a 2.8 liter 328 is, I think the same story will unfold. It certainly has for me racing a 160 hp Del Sol against a TR-8. Can hang with them through the corner, eat him through braking, and hang till we both shift. Then he goes from maybe 140 whp at 5500 rpm to 140 whp at 4300 rpm. I meanwhile go from 156 whp at 8200 RPM to 120 hp at 6500 RPM. He's gone.
If somebody has good dyno numbers, cool. I think they would show that the 5 liter cars HP curves are pretty flat across the shift points compared to a 2.8 BMW which I expect is flat tourque and peaks HP at rev limit. Therfore 25% rpm loss at shift is 25% hp loss. I don't have the data at hand, but this is an educated idea of the differences that exist.
How could such cars have the same lap time? I think it comes down to strut suspensions, solid axles and relatively small brakes on the V8 cars just like my X-11 vs a 2002tii.
The one point that gets lost here is that I think diversity like this doesn't make better racing. With their cheap costs, we could get a lot of V8 cars. When there is such a big differences, if the V8 cars are wrong for the class, there will be a lot of pressure to fix the class. If one shows up with a rocket, is it great prep or great cams, nobody knows. A lot of problems are solved when similar cars are classed together. There is no diversity in spec miata and SRF, they are our largest classes.
By my estimation, ITR will be about BMW's, Porsche's, Acura's and Honda's with remarkably close racing. This is what shows up in lower classes. Although they are classed, I will be surprised to see many 300 zx's as these are complex and expensive cars to develop and race. Especially if you have to build them from scratch. I think it would be better for SCCA turnouts and the participants to run the V8 cars in their own class. Based on the enthusiastic response, we might be surprised how many show up.
Just another enjoyable hour on the IT forum.
bob