ALFAGTV6.COM

Micke · Post by **Micke** » Tue Apr 11, 2006 10:00 pm

Is it due

Z: is what?

Vittorio: Why you need one?

PS!
The inertia values for an Alfetta (unmodified):
Front FW 0.103
Rear FW 0.071
Clutch 0.030
Crank 0.036
Prop shaft 0.010

la_strega_nera · Post by **la_strega_nera** » Wed Apr 12, 2006 4:32 am

Micke wrote:
Is it due
Z: is what?

Vittorio: Why you need one?

PS!
The inertia values for an Alfetta (unmodified):
Front FW 0.103
Rear FW 0.071
Clutch 0.030
Crank 0.036
Prop shaft 0.010

Micke, what units are those in?

I think half the point of moving to the 1 piece driveshaft is removing an extra failure point... I'd have no qualms about having one mad by the company that did the 3 1/2" shaft on my ford, for such a big shaft its thinwall and light.
I'd still put driveshaft loops in front and rear though!

Sporttunergtv6 · Post by **Sporttunergtv6** » Wed Apr 12, 2006 6:45 am

I understand that on the list of things to do, like mats said... this mod is somewhere slightly above lighter paint, but I will be lightening most of my driveline components soon (except for the crankshaft, as you mententioned Micke.. that will come with the motor i have not yet started), and it seems al can be done for less than cf... with that said I would just like to know if anyone has pursued this type of driveshaft, and where they got it done.
Thanks,
Vittorio

Mats · Post by **Mats** » Wed Apr 12, 2006 9:14 am

How much will you move the engine rearwards?

Micke · Post by **Micke** » Wed Apr 12, 2006 9:25 am

Sorry Strega,

as most guys don't know the numbers anyway, I just printed the numbers to get the relations. Unit is kgm^2

PS! It might make sense also to throw an eye on theses values before spending a fortune on any separate part like alu FW.

Sporttunergtv6 · Post by **Sporttunergtv6** » Wed Apr 12, 2006 11:06 am

Micke,

How do you compute inertia values? If those are the values of driveline components where the majority of the weight is centered very close to the turning axis what would an inertia figure be for.. something like a big heavy wheel and tire. Do these values ever exceed 1?
The Alfa i am working on right now is my first car, and i plan on keeping it as long as i can. Since i live in NYC the car is hardly ever driven on the streets; infact i have just pulled the registration. As time and money permit I would like to modify this car with out any particular purpose except to make it more unique. I would like to think the direction i am going in to be race oriented (in that i am gutting the car and only putting back necessary items like steering wheel {not even a horn button! 3 ounces for mats pile of things to toss and never look back at

}) , but there isnt exactly an unlimited class, so i guess that makes it a show car.
I have read too many import and muscle car magazines since i was 13 to not look into al driveshafts and stuff like that. However i am not looking into these parts to get more ho's on my shit... it is not a matter of bling... I do not want this car to turn into a ridiculous body kit with a motor, just a show up to the track, no headache, balls out performer that someone else can look at and say nice work. It is kind of like What Would Dahlbach Do? sort of mod scenario

... except not quite.
Between my father and I we have another GTv6 that can be used for E prod if I ever go for my SCCA license, and on that car we can keep it strictly business.
For now, as long as you are still reading, indulge me with hypothesis like whether or not to keep keep guibos or go to u joints? I have no idea is that even possible!? You tell me.
Regards,
Vittorio

Mats · Post by **Mats** » Wed Apr 12, 2006 12:37 pm

Do you have drivetrain problems? Are you planning on a 500Hp engine build?

WHY do you wanna mess with that shit? IT WORKS GOOD FOR ALMOST ANY MOD YOU CAN THINK OF. God damn it...

It's like spending 2000USD on a perfect replica of the floor sheet metal in stainless steel, only you will know it's there and you will gain absolutely nothing in terms of performance. We are talking 1/100 of a second per lap, can you drive that well consistantly?

I would pay for a thinner front window before a CF drive shaft, or rewire the car with lighter wires...

If you really wanna improve how the car drives, move the engine right up to the firewall (then hit it with a sledgehammer and move it again), move the seat back to the cross member and down to the floor (move the pedals and steering wheel if you have to), fibreglass dash, ditch std instruments, get a new roof panel if you have a sunroof, throw the e-brake in the bin, make the exhaust out of 0.5mm steel tubes, 3Kg flywheel, 4" clutch, lighter starter motor, run it on a battery instead of having an alternator and so on...
I can go on like this for a while you know.

But DON'T get a CF driveshaft!

Micke · Post by **Micke** » Wed Apr 12, 2006 12:52 pm

I simply calculated the inertia. They are not 100% exact but close enough.

The tires are about 2.9 (4 of them) and rims 0.9. (mass * effective radius ^2)

Then again the parts rotating with engine speed have to rev from 5-8 krpm in a couple of secs where the wheels just accelerate a couple of hundred rpms.

Again from the stock Alfetta the wheels consume 3% in the first gear which drops to 2% in the fourth. The values for the parts rotating with engine speed are 30-10 % for the same gears.

la_strega_nera · Post by **la_strega_nera** » Wed Apr 12, 2006 4:13 pm

Mats wrote:Do you have drivetrain problems? Are you planning on a 500Hp engine build?

Well... I was contemplating putting my 5.8 in a GTV... pulled back under the dash maybe...

Sporttunergtv6 · Post by **Sporttunergtv6** » Wed Apr 12, 2006 10:52 pm

FINE! gad damn... Yea, i talked with a company today who decided they could do it and the estimate they gave me was right at 1500 for a one off al driveshaft with al trans fork and crank fork. They said it would be lighter than the cf with steel pieces but 1500 is too high for now. The polls are closed on this one, if i do order it by accident or something, expect to see photos. I guess i will just have to settle with ligtened flywheels for now.

By the by, mats, i never thought about moving the motor back for a front mid engine setup... interesting.

SO... as we move past the al driveshaft; if the two piece unit was reassembled incorrectly and vibes, is there any way to have it re balanced?

Vittorio

Mats · Post by **Mats** » Thu Apr 13, 2006 12:23 am

My firm belief is that the pieces are perfectly balanced separately, it makes no sense what so ever to balance them as a unit.
loosen (not remove!) all the nuts on the shaft and start the engine, rev it gently and bring it to a stop, retighten the nuts. If that doesn't work I would check all the centering bushings/bearings and replace if needed and look for axial load problems (i.e. seized splines or stuff binding when engine and GB is loaded up) or alignment issues (center bearing).

If all else fails take the parts to the company you talked about and have them check the parts for straightness/balance and correct them if they are bad.

Sporttunergtv6 · Post by **Sporttunergtv6** » Thu Apr 13, 2006 6:25 am

thanks mats

Reale · Post by **Reale** » Thu Apr 13, 2006 10:09 pm

Believe me, trying to get the car down to something approaching minimum weight has been a chore. Losing 10lbs by swapping out the driveshaft was a relief, and was actually kind of a bargin. Losing the center donut/center support bearing was an added bonus.
When you are attempting to lighten a race car, everything goes.
As I recall, I never advocated this item for street cars.
I will, however, add "lighter paint" to my list of off-season projects. I would welcome any and all suggestions from the "experts" about lightening the car. And no, I can't move the motor back, thanks.
-Allen

Mats · Post by **Mats** » Thu Apr 13, 2006 10:33 pm

What is the current weight and what have you done?
Is there a set of rules somwhere we could read?

This could be fun.

Reale · Post by **Reale** » Thu Apr 13, 2006 11:36 pm

If you go to www.scca.com, and search under "GCR" you will find the SCCA's ruoes. I race in the Production category. I have done all the things that are legal. My current "minimum fuel" weight is 2340, and my allowed minimum is 2300. Believe me when I tell you that reducing the weight of the car is something that I spend a lot of time thinking about.
Something I should say is that attention to many small details adds up to a big gain. By considering weight in everything you do to the car, from design to fabrication to mounting, you can make a really big difference. I kind of take exception to a statement like: "you will gain absolutely nothing in terms of performance." This is definitely true for a completely stock car, but not for racing.

CF driveshaft

Weight