Alfa Romeo ONLY please!
kevin
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Re: Project 2 : front mount SA GTV 3.0 - Sei diff

Post by kevin »

A fellow Alfa racer here in UK ( Nick ) did some research into using these couplings when he saw them on the 155DTM at Donnington in 1994 . They did not have his pcd and to make one for him back them was out of budget .
Here are some more links to read up on these couplings courtesy of Nick .
http://www.spinning-composites.com/imag ... hPower.PDF
Some more good reading from a rival company
http://www.ctgltd.com/motorsport-composites

More links in the Motorsport side .
http://www.gkn.com/driveline/our-soluti ... fault.aspx
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Re: Project 2 : front mount SA GTV 3.0 - Sei diff

Post by kevin »

Some pics of another front mount set up using Cosworth diff and box . Thanks again to Nick for sharing pics with me .
I think this cradle set up is the best way to go if some one is going to do this conversion . I would then use the BMW 7 series diff as they are many ratios to choose from and cheap .
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Re: Project 2 : front mount SA GTV 3.0 - Sei diff

Post by kevin »

Even though my race set up brake design 290mmx28mm disc with six pots fit perfectly in the 15 " compomotive rim as in pic I have found someone to remake this compomotive design for me in a 16 " rim . I will then run a 225/45/16 semi on a 8J which will suit my ratios and the wider wheel arches .
The replica centre hub will be identical to the 15 " but just with bigger in and outer dishes .
Their had been interest from a few of my friends to make a perfect replica 15" set as second hand rims have got so thin a actually are dangerous . Plus import costs from SA are pretty horrendous .
I did not realise that this compomotive design was so sought after but then it was a genuine Alfa Romeo Part number in the SA factory and was specifically commissioned with that offset for racing when they designed the gtv3.0 back in early 1983 .
If anyone is interested drop me a pm as this is not a place to put pricing . Also no profit is being made but just to help spread costs of the CNc work . The wheels will be made by a reputable manufacturer as well who make a huge amount of rims for racing .
Pic is of Ewen at my place with his awesome 3.5 parked inbetween the carbi and the race car . He was checking how much clearance their was between three caliper and the bolts inside the rim .
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kevin
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Re: Project 2 : front mount SA GTV 3.0 - Sei diff

Post by kevin »

I think this car will take another few months to sort out with all the fancy detail finishes inside . Yep Im bored and want to get this car more refined . Probably gonna add back another 6kg of assorted crap to make it friendlier to do a ring trip in . Right now its pure race package with real short final drive to suit the track it last raced on ie Zwartkops in SA . I will probably add some non flammable paneling in the rear boot / back seat area . NO carpets :)
Heat shields underneath - http://www.demon-tweeks.co.uk/motorspor ... eat-shield
and ironically a light weight heater unit . http://www.t7design.co.uk/index.php?mai ... cts_id=180
Exhaust DB is ok for time being
I have another automatic 119 diff with me which I will put . Here are some pics of the Alfa Sei diff ratios for those who are wanting to use one of these . I have also included the BMW ZF ratios which are common through the range including the E36 M3 and the E46 328i

The BMW ZF ratios are as follows in car at present
4.21 - 1st
2.49
1.66
1.24
1.00 -5th

The Alfa Sei diff ratios are :
2.5 manual carb came with a 11:50 (4.54:1) and the injection manual came with a 11 :47 .( 4.27:1 )
And the automatic a 13/47 ( 3.61:1)

I found this site a for quick calculations but just change the info in the blocks

http://www.unixnerd.demon.co.uk/revs.html
And with my tyre size of 225/45/16

Note I'm using 5500rpm benchmark as its a 3.7 and no need to really rev more on the road .

My speeds are at 5500rpm in each gear give me with the 4.27:1 ratio
1st -35km/h
2nd - 59.37 km/h
3rd - 89.05 km/h
4th - 119km/h
5th - 147km/h


And the automatic box of 13/47 ( 3.61:1)
My speeds are at 5500rpm
1st -41.53 km/h
2nd - 70.26 km/h
3rd - 105.34 km/h
4th - 153.39km/h
5th - 174.86 km/h
.
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MR2 Zig
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Re: Project 2 : front mount SA GTV 3.0 - Sei diff

Post by MR2 Zig »

Dang....even that auto trans ratio is super short with the 1:1 5th gear :shock:

The Ring trips will need even taller gears or a E46 6speed box that has an overdrive top gear. You may want the taller gears just to get there...
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Re: Project 2 : front mount SA GTV 3.0 - Sei diff

Post by Giuliettaevo2 »

There are three of those sei diffs in my shed. I have the auto one for my car and two of the 4.27 ons for spare. I have an overdrive fifth gear That's is 0,81:1.

Doen the newer six speed box have longer radio's?
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Re: Project 2 : front mount SA GTV 3.0 - Sei diff

Post by 75evo »

What would the average speed be on the road to the ring? Around 130 km/h? That would be about 4000 rpm-ish with the auto diff. That's sort of alright I guess. Would still be a bit buzzy with no sound deadening.

BTW with a front gearbox, why did you go with a 5-speed when you initially built it? Time to look for 6-speed. Make the 1-5 stack close together than make 6-th gear an 0.8ish and couple it with the auto diff, perfect car for ring trips.
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Re: Project 2 : front mount SA GTV 3.0 - Sei diff

Post by MR2 Zig »

Provided I'm remembering right, the 6 speed BMW box is the normal spacing with a 1:1 5th gear and about a .8 overdrive for 6th. I have the 5 speed in my (ahem) other car. The gear spacing is more even than the Alfa GTV6 box.
M3 Coupe E36 Coupe Manual
4.2 1st

2.49 2nd

1.66 3rd

1.24 4th

1.00 5th

-

3.89 rev

3.23 diff

6500 redline rpm

E46 Coupe manual
4.23 1st

2.53 2nd

1.67 3rd

1.23 4th

1.00 5th

0.83 6th

3.75 rev

3.62 diff

8000 redline rpm

I hope that helps.
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MD
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Re: Project 2 : front mount SA GTV 3.0 - Sei diff

Post by MD »

Ziggy as far as I can remember we have always been pretty much in agreement with points of view where we have intersected but I am stunned by this comment:
"Dang....even that auto trans ratio is super short with the 1:1 5th gear :shock: "
I just don't get it with the US insistence with tall ratios ! If you run taxis all day for a living perhaps fuel economy is an issue and you want a tall diff. In which case get a diesel Chevy. :D
Alfa catered for this mindset when they released the 75 3litre with a tall diff of similar order. These sort of ratios turn fun sporty engines with good power to weight chassis into slugs.

For a general run around for a 1250Kg car with a 3 litre donk, a 4.1 diff is about right. Gets the torque band humming just right for a sporty feel and at the end of the day, isn't that why we have Alfas anyway.

Sorry mate, not a crack at you per sei, it's the whole US mindset really.
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Re: Project 2 : front mount SA GTV 3.0 - Sei diff

Post by Giuliettaevo2 »

MD, you're forgetting it's not an overdrive gearbox.

4.1 ratio behind a v6 works perfect in for example a 75 because they have an overdrive fifth gear. Imagine the same 75 V6 with only 4 gears so minus the overdrive fifth and you would not be very happy on the motorway.
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Re: Project 2 : front mount SA GTV 3.0 - Sei diff

Post by MD »

I see, I overlooked that for Kev's car in which case a compromise would be a 3.9 diff for 200khr @ around 6800rpm and let's face it, how often is he going to get a chance to do that off the track? I think those speeds are illegal in the UK.-stand to be corrected.

As for the tall diff 75's, I have driven them and it absolutely stuffs the car up. It's an economy ratio and not a sporting ratio at all.

Don't turn your project into a slug Kevin is all I am saying. No point having the top speed if it takes 3 weeks and visa to get there... :D
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Re: Project 2 : front mount SA GTV 3.0 - Sei diff

Post by kevin »

Scott that's interesting about the six speed box as that will give a 210km/h top speed . At silverstone trackday my mates 75 3.0 was doing over200km/h and at ring were were often at that speed .
This box will be on my list but I heard from the race guys that the old five speed box is a much stronger box . Not sure where they get the info from unless its just from testing and racing .
MD , no chance of this car been a slug . If anything I'm glad it will slow down a bit but adding back max 10kg not gonna make big difference . ( just like a big bag of biltong during a rugby match :D )

Edit : just checked bm forum ( aaarrgghh ) you can't swap boxes with changing clutch , flywheel , gear linkage and prop set up . Also again looking at those ratios I'm going to be worse off through the gears with a torquey motor in order to gain the top speed . Hmmm I like the top speed in sixth .
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Re: Project 2 : front mount SA GTV 3.0 - Sei diff

Post by MR2 Zig »

My other car :wall: is a bmw z3m coupe with the 240hp S52 engine and the ZF 5 speed and 3.23 diff. I want to put the 6 speed in it and the next shorter diff (3.46 ). Overall I'd get a little lower highway rpms, hopefully a bit better mileage, and more fun out of the lower gears.

The change takes a clutch disc from a 535, a shorter propshaft, different trans mounts, and mods to the shifter to get it in my car. It may take modifying your trans tunnel depending on how tight the rear of the tunnel is on your car.

I know Aussieland is a big spread out country, but I don't know how that compares to the US. Having done a weeeeeeee bit of driving in Europe (more 'e's is less right?) I can understand that short gears and high revs at speed don't matter that much because you aren't going all that far at a time. Here I go 60 miles a day on just my commute to and from work. The nearest road race track is 120 miles away and the Sierra Nevada mountains are 30 miles away and have endless twisty roads. Things in the western US are s p r e a d o u t.
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Re: Project 2 : front mount SA GTV 3.0 - Sei diff

Post by kevin »

Calling LSD gurus ( Mats , Jim anyone )
I'm going to pull out the LSD on my Alfa 6 Diff . From the the manual pics it looks like 45degree ramp angles for accelerate and coast which I'm happy with as its a road track car and will be doing quite a bit of wet weather driving .
Now I need to service or change clutches but I can't find any info on the the preload setting . Only once I take out the inner and outer friction plates I will be able to measure them and then search if these parts are avaliable or try match similiar .
If I can't get exact friction plates what preload setting should I look at if I must change the shim washer ?
Secondly if I can only get friction plates with with same internal diameter but slightly smaller outer diameter . This will probably bring the percentage lock up or bias down a bit .
Lastly is there away I can check without stripping and micing up the friction plates to see if they are worn ? Note the diff is out on the table already .
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Re: Project 2 : front mount SA GTV 3.0 - Sei diff

Post by Mats »

Don't be afraid of opening the diff, it's very straight forward. Check the parts, then you will know.
Preload will give you understeer but a more predictable behaviour in the transition between coast-drive and the opposite, passing "neutral". More preload means more wear -> more service.
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