V2Rocket

Although I don't have track experience like you do, the basic principle should be pretty simple. The more downward force (weight) on an object causes it to grip more to the ground because the force needed to break it free (and overcome static inertia) increases due to the increased friction between the object and the ground.

F1 drivers don't need to rely on weight for grip, because they have aero grip galore and all kinds of mechanical grip from those fat tires and crazy suspension. In a car where even the torsion suspension is made of carbon weight is kept to a minimum for a reason.

Howabout a 911? They suffer(ed?) from chronic understeer since all the major weight in the car was out back. 911 cars can launch very well off the line, but at the same time it is very hard to do a burnout in one unless you are really revving it or it just makes stupid power. This doesn't even take into account weight transfer.
I think it was discovered that a fully dressed M44/01 is about the same weight as a bare LSx longblock and that the accessory package for the LSx made up the most weight gain.

Potomac-Greg

You have to factor in Newton's Laws. A big lump of weight going straight ahead wants to keep going straight ahead. It's not helping on a turn, it's fighting your tires. Keep the center of mass in the middle, and all four tires play a role in making the mass turn. This is the principle that explains the characteristics of front-heavy (e.g. Audi), tail heavy (e.g. 911) and balanced (e.g. Boxster) cars. The mass hates changing direction!

Sandbags in the trunk (in RWD) will help in the snow, but they will induce oversteer. And the 911's basic flaw (recently overcome with major engineering, electronics and tires) is OVERsteer, not understeer.

V2Rocket

Thats very true.

However with the 911 I believe that the problem was with turn-in there was understeer because the front tires couldn't grip well but then once the car got rotating it switched to oversteer because of the pendulum of weight in the back trying to come around, which is why you have to throttle around corners, right?

alordofchaos

Don't hate me for asking, but what kind of mpg are you looking at?

This is something I may consider in a few years after my current projects are done. Should be relatively easy to locate a beat 944 or 951... I like 944s too much to do this to a clean car

I actually kinda wish the 944 had a similar hatch to the 928, with the two fixed side panels. Be easier to tint and deal with delamination.

Potomac-Greg

Correct. It's actually true of any balanced car that you do not want to lift off throttle during a hard turn; more so with an older 911.

V2Rocket

please forgive me for any errors in my statements, although i did very well in highschool physics its been a few years

Whisper

Okay, first of all, we need to stop using the word grip.

You cannot grip the road; the road is a flat surface. If you think otherwise, go grab the wall and pull on it. Let me know how that goes.

By themselves, the "fat tires and crazy suspension" provide no friction whatsoever.

On a macro scale, force of friction is dependent upon only two things:

1. Downforce.
2. The characteristics of the two surfaces, generally expressed as a coefficient of friction.

(Notice that neither of these includes tire size. Increasing surface contact area does NOT increase friction one bit. Why we have big tires is left as an exercise for the student.)

It our case, downforce has two sources: weight, and aerodynamic pressure.

Increasing weight requires an increase in mass, or moving the race to a larger planet. Since increasing mass increases the momentum that we must use friction to overcome, obtaining more downforce by increasing weight is only a good idea when the coefficient of friction is greater than 1.

*Cough*Never*cough*.

Aerodynamic downforce is almost "free", except insofar as wings have weight and create drag, and vacuum systems have weight and get you disqualified.

But "handling" does not consist of the force of friction alone. It also includes the distribution of that downforce, and the moment of inertia of the vehicle.More mass on either end will increase the vehicle's moment of intertia. More weight over the front wheels produces more downforce available to steering, but decreases proportional downforce to mass available to the drive wheels.

harrisonrick

So...in layman's terms, driving Tony's car gave you a chub-on.

Potomac-Greg

I'm not Skip Barber, but I read his book!

It's actually a great book for understanding vehicle dynamics and the effect of weight/mass. But if you're not into track work, it would probably be pretty dull.

FSAEracer03

Is that "6' if you're going to wear a helmet" or "6'... period?" Hahaha. I'd love to hop into one. I think part of the allure is that you know it wasn't ever intended to be like that. I remember driving my first E30 swap (3.2l) and being giddy for hours afterwards.

333pg333

I don't think anyone really had any doubts as to how good these conversions can be. Looking at Travis' and Tony's cars it's clear that these are a fantastic alternative. I'm sure that most people would be instantly converted by going for a drive. Hopefully there are still some nice 4 cylinder versions that would elicit the same response.

Whisper

Tony's exaggerating slightly. I'm 6'2 and I fit under the roof. And most my height is in my torso; I'm actually taller than Spencer when we're both sitting down.

Spencer just couldn't fit his *** into the seat.

You know, that's the funny thing. The LS1 is such a perfect match for the 951 five-speed that you would never know it was a swap unless someone told you. When you first consider doing one of these, you tend to think, "why not go to a 968 six-speed?", but when you drive one, you realize that's totally superfluous; wider gears work out better, especially since the plethora of available low-end torque means that you shift less anyway.

OVERBOOST

On my trip to the Hershey Swap Meet yesterday I avg ~23 MPG, 188 miles round trip.
The ride was ~85% highway @ ~75-80MPH, with several full throttle runs up to the top of 4th. The remainder was @ ~30MPH.
I have a mild cam and the fueling is still rich, so It could be a hair better....

IIRC, when my car was a smooth running chipped turbo I could yeild ~25-26MPG all highway.

V2Rocket

Just for comment on the MPG, a Z06 with an even bigger engine gets 24mpg and weighs more than a swapped 944.

ninefiftyone

What is a good price for a complete LS1 motor? I really miss my old F-150 Lightning's torque (~500ft lbs) so the LS1 might be my ticket. I spoke with one guy who bought a complete car for $4500 and I've seen take out motors from $500 - $3500. Anyone want to share their experiences on acquiring an LS1?