"But it'll never handle..."

In reply to Swank Force One:

I'm curious to hear Keith's take, but my understanding is that there's nothing magical about 50/50, and that you can likely turn a faster lap with more rear bias if your tires are suitably sized. Rear weight bias uses all four wheels better under braking, and puts more weight over the drive tires on acceleration. Midcorner is where it can fall down, but if the tires are appropriately staggered, that's not necessarily an issue either. Look at tire sizes and engine locations on the vehicles which have rules that allow playing with that sort of thing...

OTOH, this might be just like my pretty much dead wrong "the extra rear weight's in the diff" comment earlier in this thread, in which case I'll probably shut up for a while...

By your guys math, how much horsepower would a 102mph trap equal in a 3200lb car? Because there are more factors in play than just raw power.

50:50 is a holy grail for Miata people, although the car isn't really 50:50 I've never gone chasing it in particular so I can't say I've ever done any back-to-back testing of just weight distribution and nothing else. To do that, you'd have to add fairly significant weight to move around.

Did you know that dropping the top moves the F:R balance 0.3% toward the rear?

The main reason I posted these numbers is to hopefully lay to rest the old chestnut about how V8 Miatas are nose heavy and can't handle. I would have thought that setting lap records on a tight track would have taken care of it, but some people simply don't believe it. Still, showing that the balance of a V8 car is equivalent to that of the very same car with a turbo powerplant might help a few people past their knee-jerk reactions.

I agree that rear weight bias is probably the fastest setup, and that too much front bias is going to be a problem. But it's pretty difficult to make those changes in a given car without making other massive alterations that might mask the weight distribution.

yamaha wrote: By your guys math, how much horsepower would a 102mph trap equal in a 3200lb car? Because there are more factors in play than just raw power.

I think that's aimed at the quick-n-dirty math I was doing earlier. There are numerous calculators online, and essentially it works out that trap speed correlates well with weight and peak HP for most cases. Interestingly enough, turbo cars could ruin these generalities because their torque curve can be much different than a naturally aspirated car. Anyway, I used

http://www.wallaceracing.com/calchpm.php

and got 285 from your numbers. It usually works out to be closer than you would expect. It was within spitting distance of being right with Joe's.

In reply to tuna55:

Car in question was N/A and probably around 200fwhp.......I think that pretty much throws a monkey wrench in that one

yamaha wrote: In reply to tuna55: Car in question was N/A and probably around 200fwhp.......I think that pretty much throws a monkey wrench in that one

It's intended to be crank horsepower, so it's actually pretty close.

I doubt the engine made over 240hp at the crank......I'm still convinced there are many more variables left completely out of those.

yamaha wrote: I doubt the engine made over 240hp at the crank......I'm still convinced there are many more variables left completely out of those.

oh there are - tons. Tons and tons. It's a ballpark, nothing more. They all work on the interesting principal of trap speed though. If you take a car and put crappy tires on it and launch at idle, you'll get roughly the same trap speed at 1/4 mile as a wheels up 3K trans brake launch. If you use weight and HP, it turns out to correlate to trap speed rather well.

In reply to tuna55:

Thank you, ballpark estimation would make sense, just needed that verification for those that took it as fact.
Oddly enough, said car ran a high 14.

yamaha wrote: In reply to tuna55: Thank you, ballpark estimation would make sense, just needed that verification for those that took it as fact. Oddly enough, said car ran a high 14.

A high 14 at 102 means (and I have owned a car with results like this) you have terrible traction and/or gearing or your engine isn't pulling hard the whole time and there is some massive bog. I had all three.

Or high drag. My Locost was clocked at 13.8 at 98 mph with a good launch. The acceleration curve showed it falling off dramatically above 80 mph.

Keith Tanner wrote: Or high drag. My Locost was clocked at 13.8 at 98 mph with a good launch. The acceleration curve showed it falling off dramatically above 80 mph.

Good call.

I should let you have your thread back now, eh?

In reply to tuna55:

Its a terribly designed fwd for launching, no power until 4k rpms, and the ZOMG GOTTA GO DAWG power above 4k rpms. Gearing is actually the only reason they're reasonably fast. Drag coefficient is actually better than most(even by today's standards)

I'll also give keith his thread back.....

I just meant the "other" guys are lame and I would expect nothing less. haha but seriously. . . . they are

interesting stuff on the contract agreement though

A V8 makes sense as an upgrade for so many cars. My fabricator has been trying to get me to put one in the Datsun for some time, in this case as the A-Series motor and tranny only weigh 215 lbs combined so I could complain about the balance but given it would end up a 1900 lb car with an easy 300 HP it's not like it would matter.

The Ford small blocks with Aluminum heads and a T5 tranny is about the lightest package for american V8's , something like 390lbs for the motor and 70lbs for the transmission, given many iron block 4 cylinder engines are at the low 300 lb mark and the transmissions weigh about the same as a T5. Like many people when I found out just how much a turbo four with all the accessories weighs, the V8 option makes real sense.

I also am amused by the number of people who bemoan the lack of balance in V8 converted small cars yet talk loving of AC Cobras.................mmmmmm isn't that a small sports car known as AC Ace converted to a V8, can't be that, that would destroy the balance.

On a Different note I know about the Aero effect my dual sport bike, Beta 525RS will hit 60 in well under 5 seconds and I think low 13 1/4 mile time but top speed 106 MPH. Past about 80 your the human parachute and I'm sure the high front fender is an awesome air brake.

                    Tom