Corvette C5/C6 transaxle in a high horsepower GTV6 - Page 3 - Alfa Romeo Bulletin Board & Forums

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post #31 of 96 (permalink) Old 02-21-2017, 06:47 AM
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I was amazed by two initial findings:

1) How light that entire Corvette rear setup was - and
2) How close the initial measurements are for the length of the setup!

I was really worried about shortening the drive-shaft inside of the torque-tube - in addition to shortening the tube itself - in addition to all of the other variables! It looked SO long! Well, just from the initial eyeball that we have on it, we may not even have to touch the length!

The Corvette rear stance is WIDE though and we'll have to section the rear sub-frame to narrow it considerably! That - and then shorter side-shafts and a shorter anti-roll bar obviously. But that's it in terms of modifying the rear unit itself. Then there's the conversion to the bell-housing at the front and the front clutch arrangement, which is another story.
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post #32 of 96 (permalink) Old 02-21-2017, 07:01 AM
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The Corvette transaxle stops right behind the bulkhead - let's say right behind a rear passenger's heels. The torque-tube makes a perfect distance run from there right to the rear of the stock Alfa V6 engine! I mean, I couldn't have planned it better myself - it's like it was made to go there. The Corvette just looks SO long to me though! (The nose is long and it houses the extra two cylinders - must all be forward of the torque-tube!) The Vette engine must sit pretty far back in the chassis, I suppose...

Stated differently, the distance in the Vette from the rear of it's V8 engine to the center of the rear axles / side-shafts, is virtually identical to that same distance in the GTV6!

The biggest changes are going to be -
a) The amount of sub-floor that we'll have to cut away to make room for the Vette transaxle. (It's much taller than the Alfa transaxle. The Alfa box is actually quite flat on top! The Vette box is tall and round.) And -
b) The clutch arrangement. The Vette's clutch sits up front. (Ron opted for a Mantic clutch from Australia and had I a custom flywheel made that excepts it, but still has the correct forward and aft spacing and the starter ring-gear in the correct location!)

I'm still blown away by the paltry weight differences...
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post #33 of 96 (permalink) Old 02-21-2017, 09:08 AM
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198 versus 149 AND the 149 of the Alfa transaxle includes brakes! Plus the rear suspension is 186 versus 111kg. That is another 75 kgs

I don't consider 125 kg's to be a small increase. I remember putting an extra person in my Sud and it felt like the handbrake had been left on

I guess this shows how strong the Corvette transaxle/components must be
Pete

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post #34 of 96 (permalink) Old 02-21-2017, 09:58 AM
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198 versus 149 AND the 149 of the Alfa transaxle includes brakes! Plus the rear suspension is 186 versus 111kg. That is another 75 kgs

I don't consider 125 kg's to be a small increase. I remember putting an extra person in my Sud and it felt like the handbrake had been left on

I guess this shows how strong the Corvette transaxle/components must be
Pete
I thought he wrote the total difference was 107 pounds (~48kg).

This gearbox was originally paired to an LS2 V-8 which makes 400 lb.-ft. but guys are running stock T-56s in 10-second cars. The differential case was strengthened in '06 (the one in the photos is an '05 but I suspect it should survive all right).

Dialing in the custom suspension will be interesting. Cool project.
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post #35 of 96 (permalink) Old 02-21-2017, 11:30 PM
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I thought he wrote the total difference was 107 pounds (~48kg).
He did, so I guess my maths is wrong or I do not understand the scale pictures ...

Anyway hope he is right
Pete

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post #36 of 96 (permalink) Old 02-22-2017, 12:55 PM
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I just thought, disregarding the extra weight, that big lumps seem to be going into that little Alfa, probably not necessary to hold the undisclosed power from the engine.

Seen other solutions without those bulky parts, but I guess everything is possible if there is a will!

G.
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post #37 of 96 (permalink) Old 02-22-2017, 05:23 PM
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This kind of transmission strength is definitely only needed for bonkers levels of power!
Am thinking 500+hp with uber amounts of torque to back it up. So big capacity twin turbo V6???

It will be interesting to see how much transmission tunnel work is required.
The firewall's opening would have to be modified and that would give the owner a great oportunity to move the engine back a bit for better/more central mass locating. The bell housing needs to be modified anyway.

For the rear suspension, modifying the aluminium subframe would be a huge
Same said for those suspension arms. Making new steel/chromoly arms that are shorter would be the safest way to do things.
Or keep the effective and definative characteristic of the Alfa deDion suspension.

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post #38 of 96 (permalink) Old 02-22-2017, 09:17 PM
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Quote:
Originally Posted by Gabor K. View Post
I just thought, disregarding the extra weight, that big lumps seem to be going into that little Alfa, probably not necessary to hold the undisclosed power from the engine.

Seen other solutions without those bulky parts, but I guess everything is possible if there is a will!

G.
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This kind of transmission strength is definitely only needed for bonkers levels of power!
Am thinking 500+hp with uber amounts of torque to back it up. So big capacity twin turbo V6???

It will be interesting to see how much transmission tunnel work is required.
The firewall's opening would have to be modified and that would give the owner a great oportunity to move the engine back a bit for better/more central mass locating. The bell housing needs to be modified anyway.

For the rear suspension, modifying the aluminium subframe would be a huge
Same said for those suspension arms. Making new steel/chromoly arms that are shorter would be the safest way to do things.
Or keep the effective and definative characteristic of the Alfa deDion suspension.
The 100+ lbs weight gain does seem to be huge, but the initial post says it all: the guy was breaking stuff right and left, and that becomes tiresome and expensive. Not to mention the availability of all kinds of off-the-shelf gearsets, etc, and the fact that said weight is low and centralized.

Yes, the one-time cost of custom fabrication will be expensive, but it will likely be worth it in the end for such an extreme project versus the prospect of constantly paying for the repair of broken components when running an Alfa with that level of power.

The other benefit that has not been highlighted too much is the gain in torsional rigidity---the Alfa unibody is pretty flimsy and needs all of the help it can get. A torque tube that ties the front and rear sections of the chassis together will go a long way towards mitigating this!

Obviously all of this is overkill and not feasible nor practical for 99.9% of us, and this project will have its challenges even for skilled fabricators, but I am looking forward to seeing its progress!
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post #39 of 96 (permalink) Old 02-22-2017, 11:07 PM
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"The 100+ lbs weight gain does seem to be huge," Depends on the perspective...

For the car that the Vette bits will be added to, let's consider weight gains vs. horsepower gains:

Granted the final #'s aren't in as to where this car will end up weight wise when completed... but from these initial findings... 107 lbs added replacing existing parts... for a stock 2822lb car (US version)... equates to a 3.8% gain in weight. Now then... let's compare changes in horsepower due to an engine upgrade for this car. Stock 2.5L 12v Busso V6 = 160hp. A big bore, naturally aspirated 24v 3.5L Busso, depending on modifications, is rated @ 300-325hp... but for arguments sake let's be conservative and say 275hp (my modified 24v 3L in my 164LS is 250hp). That's still a 72% increase in horsepower over stock configuration...at a minimum. Is a ~4% gain in weight going to be a disadvantage here?

To equate to lbs per hp. Stock config 2822lb/160hp = 17.64lbs/hp. This project, 2929lbs/275hp = 10.65lbs/hp

That's at least a 65% improvement/reduction. I'd say a ~4% weight increase in this scenario does not matter.

Some additional bracing will be employed, but then some interior weight removal, torsion bars removal, and lighter brake calipers & brake rotors will also be used to counter weight. Also the rear IRS cradle will be narrowed, as well as half shafts shortened. So it will be interesting to see where the car finally ends up, weight wise. But in the end, given the BIG HP gains, whatever gains in weight that might be incurred, statistically are not enough to be of a significant detrimental effect. And the end goal here is that I get a bullet proof drive train aft of the flywheel. (Not to mention better shifting, 6 speeds, large selection of gears and final drive ratios, C6 diff upgrades options, large racing/aftermarket support for this Tremec based T/A, better availability and pricing of parts, etc, etc...)

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post #40 of 96 (permalink) Old 02-23-2017, 01:55 PM
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I have reason to believe that all that work is unnecessary and that upgraded propeller and drive shafts together with another transaxle gearbox would be enough to cope for an upgraded 3,2 twin turbo engine.

Actually focus on making the engine big power relyably would be a concern!

G.
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post #41 of 96 (permalink) Old 02-23-2017, 03:15 PM
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The other benefit that has not been highlighted too much is the gain in torsional rigidity---the Alfa unibody is pretty flimsy and needs all of the help it can get. A torque tube that ties the front and rear sections of the chassis together will go a long way towards mitigating this!
I'm not sure how you think the torque tube will add to the structural integrity, especially the torsional rigidity of the chassis???
The torque tube is attached to the engine and the transaxle. And they are attched to the chassis via rubber mounts..............

Obviously any added weight has a negative effect on performance. But the added weight is about as low and as central as it can be added. And if you transmission is broken, then there is NO performance!

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post #42 of 96 (permalink) Old 02-23-2017, 07:16 PM
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Pete, you have lost me! The total gain is ONLY 107 pounds TOTAL - about 48kgs.

The bottom left-hand corner number in each corner scale picture clearly shows the total weight for that associated collection of parts!

Anyway, while the pictures of the various components on the scales were cropped to fit the associated scale shots, the full shot of the entire Corvette rear setup CLEARLY shows that the Corvette rear brakes ARE included - another benefit here (gaining outboard brakes which in this case are a gain because of the better serviceability and better performance and easily available upgrades such as the GiroDisc brake upgrade!)

I had to do a double-take myself on the numbers... The first picture in my series of replies clearly shows the totals - the Corvette setup will only add about 107 pounds TOTAL. While 107 pounds may be a lot in race car terms, for a street-track car (considering the gains in ALL other areas such as engine-transaxle alignment, gear-ratio selections, final drive ratios, a 6-th gear, maintaining the TA layout etc etc), it's a small sacrifice.

53 pounds OFF the 107 pound total gain lays inside the tunnel - at the center of the car, low to the ground, and BETWEEN the front and rear axles! The other 54 pounds sits AHEAD of the rear axles - again at the center of the car - and LOW!

And yes, eliminating the twist between the engine and the transaxle is a definite gain!

As far as power; for now she's getting a street-track trim, naturally aspirated, 3.45 litre 24 valve V6 with about 300 horses. The planned future power will be from a twin turbo plant with upwards of 700+ horses! So, yes - the modifications are all being made with the future in mind.

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post #43 of 96 (permalink) Old 02-23-2017, 08:56 PM
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As far as power; for now she's getting a street-track trim, naturally aspirated, 3.45 litre 24 valve V6 with about 300 horses. The planned future power will be from a twin turbo plant with upwards of 700+ horses! So, yes - the modifications are all being made with the future in mind.
You could always simplify your torque tube mounting, further improve weight distribution, and make even more power by going with a 6.2L V-8. They make ones that bolt right up...
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post #44 of 96 (permalink) Old 02-23-2017, 09:07 PM
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You could always simplify your torque tube mounting, further improve weight distribution, and make even more power by going with a 6.2L V-8. They make ones that bolt right up...
I've heard you can even get a chassis that these parts will bolt right into, with a lightweight fiberglass body that will mount on top.

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post #45 of 96 (permalink) Old 02-24-2017, 12:57 PM
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Pete, you have lost me! The total gain is ONLY 107 pounds TOTAL - about 48kgs.
Referencing you photos and weights:

53 GM torque tube
198 GM transaxle
186 GM rear suspension and brakes
437 total

149 Alfa transaxle and brakes
111 Alfa rear suspension and axles
70 Alfa driveshaft and roll bar and dedion
330 total

Yep difference is 107. As I am not living in the dark ages, my standard weight reference is kgs, hence why I thought we were carrying around an extra heavy person
Pete
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