[Weight Distribution vs. Polar Moment (Yaw Intertia)]

I don't post often but I have a question about the PMOI vs F/R weight bias. I am interested in the curious case of the Miata. Clearly with a low PMOI it would seem to fit the bill for autoX and indeed this likely explains why everyone and his brother seems to drive them at autoX's (at least from my experience).

 

However, they are also often toted as the closest thing to a "race car" and I always presumed it was because of the low PMOI and the connotation has always been that being like a "race car" is a good thing. In fact when inquiring to a friend who used to race for Porsche about cars to consider for track days he recommended the early miata's attributing their low PMOI as one of the reasons. He did seem to think this made it easier to wreck them too.

 

This got me thinking about F1. They should definitely have a lower PMOI than just about anything else on this planet you can sit in and I would assume that while the drivers have little trouble driving them around the track I would likely kill myself in one in several seconds. If I didn't, the low PMOI would make it impossible for me to drive anywhere near the limit, which seems to be the argument against too low a PMOI. (ya the power and downforce etc. would make it impossible too but just go with the thought experiment).

 

So why would there be too low a PMOI for a street (touring) car if the F1 cars can be driven just fine with the lower PMOI. It even seems intuitively right from my experience that a car with too low a PMOI would hurt my times because I would be scared to death of it. But sense I am not anywhere near an F1 driver I was wondering if I missed something. Thanks.

[Suspension Tech / Motion Ratio / Unsprung Weight]

WOW! That is so much more helpful than the vague generalities I have usually found in car books. I will have to pick up a copy of that. I may be getting off topic here, but is there a list somewhere of books with descriptions like the one you just gave (say for aerodynamics or engine design)? I did my undergrad in physics but it was mostly theoretical so I don't know the books to read for the more mechanical engineering based stuff.

[Suspension Tech / Motion Ratio / Unsprung Weight]

I ran the car with the 450 lb/in rear and 425 lb/in front with the 1" sway bar. The weight transfer worksheet gave me a magic number of 9.4% which predicts understeer (which it did). With the new sway bar and swapping the springs front to rear, the weight transfer worksheet gives me a magic number of 3.2% which is much closer to neutral.

 

If you don't mind me asking, what is this weight transfer worksheet you speak of? And do you have a copy of it or book that would have it?

[DIY 180 Degree/Single plane/Flat plane V-8 crankshaft…]

I have heard a handful of L-6s that also had this sound where most did NOT quite; I understand what you are saying and would LOVE to have a looong conversation with you about what makes the sound of an engine, because I have been asking that question since I was about five years old and have NEVER had it adequately answered... thanks!

 

I think this would be helpful if someone can explain it. I know all the physics, thermodynamics, harmonics, etc that would likely be incorporated. I just don't have the explanation.

[DIY 180 Degree/Single plane/Flat plane V-8 crankshaft…]

As for that "Ferrari sound"...Ferrari tunes their exhaust and intake boxes using the Bernoulli principle.

That's why Ferrari's sound the way they do. Flat plane crank and extensive intake/exhaust tuning.

 

I too have heard this. It would explain why Ferrari could make my Briggs and Stratton sound insane and I could have all the V12's or flat cranks in the world and not get that sound (at least not without 15k RPM's).

[DIY 180 Degree/Single plane/Flat plane V-8 crankshaft…]

So I came across this video on youtube and was a little confused. From what I've been reading here, Ferrari uses flat plane cranks and not 180* headers right? Or maybe both? Anyways, towards the beginning of the video, theres a car with headers like the engine above, 180* and in the valley. Could this engine use both flat plane crank and 180* headers? It seems like it'd be a little overkill if not counter productive? Maybe I'm just a total newb? Explanation anyone?

Car/engine in question is seen at about 20 secs.

 

http://www.youtube.com/watch?v=39uqfnW1wS8

 

Ah the 312. nothing sounds like that At first I was also like, "Ya, why did they do that?" But if you look close that is a V12 not a V8. I don't remember the reason for Ferrari using the "Spaghetti exhaust" as that engine was based off previous ones that had the intake on top (maybe for aerodynamics?) It also isn't a jumbled mess like the GT40. It's a clean 3 into 1 times 4 design. I am pretty sure all F1 Ferraris were V12's (Lampredi engines) until they started using the "Dino" engines designed by his son in the late 60's (I think this car actually ran in F1 with both kinds of engines). But I digress.

 

This raises a good question though. That "Ferrari Sound" comes from all Ferraris (ok maybe not the 4 cylinder 500 TR's but even they sound good). Here is a link for the V6 Dino's that came after the V12 you see in that video. V6 has NEVER sounded so good!!!!!

 

[250 GTO Owners Thread]

Welcome Tensor. I think the one place to get a GTO would be e-bay. I've seen unfinished kits on there every so often. Kinda rare, once every few months, but unless someone else has ideas I don't really know. I bought mine off E-bay a few years ago and had big plans at first but a job change stopped that. Now I just drive it as is, it's still a lot of fun. I campaigned it last year in our local autocross circuit. Didn't win any trophies (it's mostly stock) but it was a blast to tear around the course. Your post was almost like serendipity. I've been thinking about letting the folks on this board know I was going to sell it, give anyone here first dibs before putting it back on e-bay. My Garage space is very limited now and I've gone back to bikes as my main hobby. If it's something you may be interested in, let me know.

Hmm. I can't get the pic to show up. I'll try later to post one. Or I can email something to you.

 

It will probably be 2-3 months before I can afford to consider that. Just out of curiosity, what engine do you have, how much is finished, and what are you looking for price wise.

[250 GTO Owners Thread]

Thanks for the GT California website. I'd already seen it, but it confirmed there isn't anything else. Is there any particular reason why the 250 TR doesn't have a larger replica community? I mean it looks about as easy to fabricate as a 550 Spyder (not a lot of interior, extra wiring, trim, etc. plus they were all different) and I think it is way more beautiful (which is saying a lot because the 550 is gorgeous). If I was looking into a 250 GTO that was mostly finished where would you suggest I look? I have done significant mechanical and body/interior work before but I don't want to have a car in my garage for three years before I can even drive it. Thank again for everyones advice.

[250 GTO Owners Thread]

First I would like to say I have been thoroughly impressed by the level of mechanical intelligence in this forum. I have not seen it matched on the numerous car websites I have seen in my years. It's nice to see people who hear "polar moment of inertia" and don't picture a polar bear in a photograph.

 

Secondly I have had a long interest in both 240z's and early model Ferrari's, especially the GTO and GT California. Which brings me to my question(s). Is there a group dedicated to the 250 California like the group here to the 250 GTO? Also, I see a lot of information here about the exterior of the GTO but what about the interior? What has everyone done for this? I have tried to dig up all the pictures I can find but haven't come to far. Thank you everyone and I hope to learn and contribute all I can