'73 Fiat Abarth 124 Rally - project

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miro-1980
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Re: '73 Fiat Abarth 124 Rally - project

Post by miro-1980 » December 5th, 2014, 9:39 pm

Ho, ho...

2 x 48 is double 1 x 48 ( but only on paper !)

I am very well aware of the fact that it WILL not double the braking power.
I was just talking the "pure numbers" not dynamic results.

Incidentally , the brake efficiency issue is far more complex than most imagine. You have demonstrated this many times.

For the benefit of less experienced readers let me just stress that braking consists of three key elements: size, pressure and friction. But as a dynamic process the ability to slow down /or stop varies depending varies with other factors as temperature. It also involves the same 4 key elements of the tires as well as such factors car weight, disc material, pads material, road surface, to name just a few .

When comparing braking effectiveness of different discs and calipers combination we assume all other elements being constant, which they never are. While this is fine as regards all except temperature, this has to be given special consideration.

In sports brakes are not working under average conditions but mostly under extreme conditions.

Thus heat dispersion is far more important than in civilian brakes.

Following homologated upgrades in brakes for 124 Abarth and later for 131 Abarth an interesting lesson can be drawn:

The basic gr 4 131 abarth front brake homologation was 2x48 caliper ( exactly as in gr 124 ) but on a 300 mm ventiltated disc. During the running time they tried 4x38 Lockheed and Girling setup but gave it up. The basic front set up held until the end of rallying of this model, with the only variation of a smaller disc of 275.

The rear was 2x38 on a 252 ventilated disc (larger cylinder diameter but smaller disc then 124 ( 2 x 34 on 256 unvented disc).

My observations are as follows:

Given space under 13 inch wheel 256 is probably the largest disc to fit onto a 124. So the 2x 48 caliper must be working well. Importance of vented vs unvented is signified by homologation at a very late stage vented 256 discs for the front.

With more space under a 15 inch wheel in 131 the Abarth engineers went for a smaller rear disc but instead of 2x 34 - for 2x 38.

Abarth designers after a lot of trial and error decided that two elements really count: vented discs and larger discs. But they also seemed to prefer half the number (but slightly larger) pistons than the other way around.

Larger ventilated disks being better than smaller unventilated ones does not surprise anyone. We all intuitively would have the same guess. However, preference of 2 pistons with larger diameter over 4 pistons of smaller diameter is not intuitive at all.

By the way : this is exactly what you have been saying all along including your post just above.

C-h-e-e-r-s

Miro
www.131abarth.pl
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miro-1980
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Re: '73 Fiat Abarth 124 Rally - project

Post by miro-1980 » January 4th, 2015, 12:30 am

GREAT RALLY SEASON IN THE NEW YEAR TO EVERYONE ON GCRE FORUM !

Miro

PS: the work is progressing slowly as we are still collecting all the required parts. But things are looking good.

Hopefully , the car will be ready by early July.

By ready I mean the Abarth suspension and brake system in place. Looks : the rear lights , side markers and door handles as in a genuine piece. Interior stripped : carpeting removed, inner side door panels replaced with simple flat light material, big handles replaced by small ones. Dash - like in a gr 4 car with a Heuer stop clock and a Twinmaster Halda. Vintage map light. Roll cage will be in place. The car will be equipped with a n OMP extinguisher system plus a 2.4 Zero 2000 hand held extinguisher

The seats and safety belts are already FIA homologated.

Engine and ancillaries : new engine 160-180 bhp in place, remote oil filter, oil cooler, in-head thermostat, reduction gear starter, 90 AMP generator, 4-2-1 exhaust header, 2x 44 IDF Weber carburetors, mash filters with no air box, Two Red Top fuel pumps will feed fuel. The tank will be filled with anti explosion filler.

Gearbox: standard 5 gear with steel Porsche type synchro wheels. Hellix metallic clutch.

Brakes : 265 unvented discs front and rear , 2x 48 front and 2x 34 rear calipers, 2x 38 handbrake caliper ( if we can fit it onto a 13 inch wheels with a separate handbrake BMC. ( we will make it in-line if the 2x 38 caliper cannot be fit in the 13" wheels) . The servo will be removed. The single BMC will be ereplaced by a bias adjusted twin Girling BMC's.

This will be enough to rally in 2015 but will not be a finished project.

Remaining elements will have to wait for the new 2016 season.

Updates with pictures as we go along.

Wish me luck

Miro
www.131abarth.pl
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TomLouwrier
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Re: '73 Fiat Abarth 124 Rally - project

Post by TomLouwrier » January 4th, 2015, 4:23 pm

Hi Miro, gents,

Of course a very happy, healthy and prosperous 2015 to you all!

Progressing well there Miro, good to read your updates.

I see you plan on using the standard 124 gearbox to start with. I'll be very interested to learn your experiences with that, since it has a reputation of being limited to road use / about 140 bhp (although transmissions are really specified by torque, not power).
I know of a very neat German finned alloy sump for that box that gives more oil capacity and better cooling. That should help, no idea how much.
You will probably agree that 5th gear in these boxes was an afterthought giving only 12% drop between 4th and 5th. A mild overdrive, not a proper driving gear. You should have no problems getting your hands on 125 / FSO gears or complete boxes that have slightly better spacing, especially on 5th. They are much closer to the Italian design than the Lada ones, which are poor. FSO quality was much better after the GM takeover. I have not been able to confirm the interchangeability of the FSO 5th gear cluster with the Italian box. You may have to use an entire box (again: you are much closer to all those parts and sources than me).

I'd be quite happy to discuss this with you, since it falls within my own plans for upgrading my Spider. Unfortunately lack of time and funding means I've been doing research and calcs instead of actual purchases and building :-(

regards
Tom
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miro-1980
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Re: '73 Fiat Abarth 124 Rally - project

Post by miro-1980 » January 4th, 2015, 8:21 pm

Thanks Tom,

The plan to use the Porshe style steel synchro rings may do the trick. Will also look into the possibility of using an FSO 125 box.

The problem with the box is that current attachment K and attachment J of the period clearly prohibit changing the number of gears ( thus the 2k Euro Hungarian box is out) and the Italian replica of original is a prohibitive 6k Euro just for the gear set). 131 box which is like a panzer would require modification of the tunnel and once done there is no return. ( Shortening of the shaft is no problem though lengthening it later would not be likely !)

Using an upgraded 124 box is a possibility we are currently considering. At the moment it looks like the best option on the table. I have three of them so if one fails we will put another on to keep the car going, though removing a gearbox in 124 is not as easy as in 131 ( due to a crossmember position) and obviously changing it anytime soon s not a preferred solution. ) we will see what happens.

Re: German finned alloy sump for with gives more oil capacity and better cooling. This is something to consider. I would appreciate if you could help me source it. We are also looking Mocal oil accumulator (1.5 quart). This is a solution GC suggested for my 131 and it works perfectly. We have space for it and the under the hood arrangement will be done in such a way as to reserve space to fit it, if oil pressure proves to be a problem. However, oil starvation - as you know - can occur without much oil pressure drop (especially on sharp long curves) thus use of properly modified sump to start with is of key importance. This is the first order of business.

Miro
www.131abarth.pl
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miro-1980
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Re: '73 Fiat Abarth 124 Rally - project

Post by miro-1980 » January 4th, 2015, 8:54 pm

Re: 124 -131 gear ratios

By the way, the 131 gearbox gear ratios for gears 3-5 re very close to that of 124.
124 - 131 compare.jpg
124 - 131 compare.jpg (14.62 KiB) Viewed 3615 times
The real difference is in gears 1 and 2.

I have found the 131 ratios to be quite comfortable. The long 3rd gear is useful and the slight overdrive in the 5th serves well when using a high diff ratio (like 6.14 or 5,375).

Obviously the top seed, at such high diff ratios is reduced in favor of acceleration and ability to go uphill. It is either one of the other. The engineers have came up with such differing diff ratios select your reference based on the actual rallying conditions. Note that there were 10 different homologated diff ratios for 131 Abarth, starting with 3,63 at the low end and ending with 6,83 at high end.

There was a good reason for it

I do not think that the 124 ratios will be a problem. The question is will it sustain almost 200 Nm of torque.

We will see in practice

Miro
www.131abarth.pl
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TomLouwrier
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Re: '73 Fiat Abarth 124 Rally - project

Post by TomLouwrier » January 5th, 2015, 7:30 pm

hi Miro,

PM sent about the alloy sump.

The 124 ratios you quote are from the close ratio Colotti Abarth Corsa, the 124 road going ones were 3,667-2,100-1,361-1,000-0,881.
Your 131 here is an Abarth too, the regular ones had 3,612-2,045-1,357-1,000-0,834 (as far as I know). You see the 131 road box has a more modern (longer) 5th. Good for highways and cruising with even less noise and fuel consumption than the original 0,881 5th which was just a mild overdrive added to a 4-speed design.

You should judge a box by the overall ratio (1st/top) in order to see its' spacing and thus character. As far as my information goes:
- 124 road: 3,667/0,881 = 4,160 (very short 'overdrive' 5th, uneven spacing)
- 131 road: 3,612/0,834 = 4,331 (that's due to the longer 5th gear. A much better spacing for modern driving)
- 131 Abarth: 3,612/0,870 = 4,151 (pretty much identical to the 124 road, no idea why they chose that again)
- 124 Abarth (Colotti): 2,724/0,840 = 3,242 (close box, nice even spacing between all gears, bit of a longish 3rd)
Practically all our road boxes are around 4,2 - 4,7. The close ratio ones range between 3,2 - 2,7. Quite a difference!

So for competition you may assume: the shorter, the better. Overall gearing can then be set up by selecting differentials, usually the required 'top speed in top gear' determines the diff and all the rest follows from that.
All road boxes always have 1st and 2nd very low because of the need to drive a saloon up a hill from standstill with you, your wife, 3 kids fighting in the back, a full load of luggage in the boot and probably a towing a caravan too.... A sports car with less weight and a more powerful engine can do with a lot less reduction. As trade off you get all gears much closer together so you can keep the engine on full song.

Regarding torque: the highest numbers I have found for cars with the 124 road box are the 2000 Volumex (206Nm) and the 2000 turbo (172Nm). All competition cars and Abarth Stradas had a Colotti or Cima box. You mileage may vary... literally :-)

regards
Tom
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miro-1980
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Re: '73 Fiat Abarth 124 Rally - project

Post by miro-1980 » January 5th, 2015, 7:44 pm

You are right Tom,

The ones I quoted are Abarth Collotti ratios. the proper standard 124 box ratios are:
124 standart box ratios.jpg
124 standart box ratios.jpg (39.53 KiB) Viewed 3590 times
The differences between standard 131 and standard 124 do not seem excessive, though I fully agree with your comments.

It looks like I will have to work with diff ratios as the box ratios seem to be fixed for me.

Well we have to make do with what we have.

Miro
www.131abarth.pl
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TomLouwrier
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Re: '73 Fiat Abarth 124 Rally - project

Post by TomLouwrier » January 5th, 2015, 7:52 pm

There may be an obscure option as last resort, if you're willing to go mix'n'match with parts from different Fiat and FSO boxes. Looks workable on paper but no idea if they will acutally fit together in the real world.
I'll come back to you about that.

Tom
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miro-1980
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Re: '73 Fiat Abarth 124 Rally - project

Post by miro-1980 » January 5th, 2015, 8:01 pm

Well,

Ths is exactly my secret plan.

What I have decided is to give my box to an gearbox expert friend whu has cut all his teeth on FSO Fiat type gearboxes. I told him :
-"I do not care what you put in it as long as it works and fits the car - just make it fly !!!"

He replied : but just do not ask me how I dd it . it is my t4rade secret .

Hopefully he will do his magic and make it work Abarth style ...

Rgds

Miro
www.131abarth.pl
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miro-1980
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Re: '73 Fiat Abarth 124 Rally - project

Post by miro-1980 » January 18th, 2015, 3:18 am

Need small part !

Just bought handles of the early style ...
new handles.jpg
new handles.jpg (21.2 KiB) Viewed 3076 times
A small but painful problem appeared .
The new handles did not have anything to keep the lock in place and connect the back of the key cylinder to the main door lock

There should be a small plate / lever with a push in connector that enables you to connect the back of the key cylinder to the door lock.
Turning of the key releases a latch blocking door from opening , and pushing the button actually releases to door lock and opens the door.
There is also a small spring to return the key to its proper position.

These handles often brake. Main cause is braking of a one of two bolts mounting the handle to the door. Once this brakes the handle is useless.

I desperately need two of such broken handles , just for parts, or just the small parts that bold to the back of the handle.

Anybody by chance have such spares?

Rgds

Miro
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miro-1980
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Re: '73 Fiat Abarth 124 Rally - project

Post by miro-1980 » January 22nd, 2015, 1:53 am

Typical "building a replica" problems : "making it look like an original"

Here everything is in the detail.
As you know the car we are working on is a CS0 US version and it is to look as a CSA .
So one of the issues we are facing is the external body looks.

The most obvious are most visible differences:

1/ different front markers and indicators
2/ front and rear side markers
3/ rear lights
4/ tank cap
5/ doors and handles

To make them look right some parts and some body work is required. Fortunately, most parts are easily available.

The front indicators now look like this :
124 abarth Winner 73 Rally Poland.jpg
124 abarth Winner 73 Rally Poland.jpg (119.89 KiB) Viewed 3158 times
I am quite happy with it.

The side markers will be removed and welded over while on the front fender there will be a small turn signal repeater:
1973 side .jpg
1973 side .jpg (29.02 KiB) Viewed 3158 times
side repeater.jpg
side repeater.jpg (17.58 KiB) Viewed 3158 times
Rear lights ;
rear lights .jpg
rear lights .jpg (18.61 KiB) Viewed 3158 times
They are not cheap but available. I got my replicas for a decent price in Germany:
rear replicas .jpg
rear replicas .jpg (31.13 KiB) Viewed 3158 times
Tank cap : Monza style caps are readily available and not too expensive:
1978 Andrej Jaroszewcz original..jpg
1978 Andrej Jaroszewcz original..jpg (32.32 KiB) Viewed 3158 times
Making the doors fit the old style handle is only a torch and a hummer away. What I have found to be most frustrating was the handles. Or actually the little plates that screw to the back of the lock cylinder and serve to connect to the main door lock are the hardest to find.

I bought my new replica handles ( very nice ) in Germany , but these vacanot be connected to the door lock and in fact the key cylinders will not stay in place unless you have these little devils.
Finding a set of these plates sold separately proved to be impossible, so I had to buy another set set of (complete0 used handles in US - just to get these two small parts.
handle parts to find .jpg
handle parts to find .jpg (39.84 KiB) Viewed 3158 times
Oh, well - if is a never ending story to make all elements be and look right.
Unfortunately I am sure there will me more such small frustrating issues as we go along. There always are.

Hopefully, however , we have solved the rod ends for the anti roll bars by ordering a set specially designed for high wear and corrosive environment. The rods we got are all pre- tenssioned , which means they will not rattle after just a few rallies. I use the same kind on my 131 and after several years of use we see no signs of wear whatsoever.

Well, the never-ending story continues.

Miro
www.131abarth.pl
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miro-1980
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Re: '73 Fiat Abarth 124 Rally - project

Post by miro-1980 » October 23rd, 2015, 12:18 am

This is just to confirm I am still alive and have not abandoned the project.
big shl_img_8778.jpg
big shl_img_8778.jpg (307.91 KiB) Viewed 3145 times
This recent picture from rally Bohemia clearly shows that a standard suspension is not for sport !

Good news : we have bought a 1800 cc engine for this project and are working with Guy on the sump and other details

The project is planned for completion early next year.

Will try to update this thread more regularly , now

Miro

PS: just to make sure we all know the 131 is also in full working order :
This is a recent picture from a rally in Austria:
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miro-1980
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Re: '73 Fiat Abarth 124 Rally - project

Post by miro-1980 » October 23rd, 2015, 12:21 am

Help needed

It has come to my attention that gr 4 replica tanks, FIA homlogated roll cages and aluminum door sheets for 124 Abarth are available somewhere in Germany.

Anybody in the know ?

Rgds

Miro
www.131abarth.pl
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TomLouwrier
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Re: '73 Fiat Abarth 124 Rally - project

Post by TomLouwrier » October 23rd, 2015, 1:52 pm

Miro, good to see you back!

Just did a quick search and find OMP lists roll cages for the 124 Abarth. They have dealers in Germany but 2 in Poland as well.
Haven't found a German producer though. Will have another look this weekend.

gr
Tom
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Spider 1969
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Re: '73 Fiat Abarth 124 Rally - project

Post by Spider 1969 » October 23rd, 2015, 7:48 pm

Hi Miro,

Aluminium doorplates available in Holland.
I'll PM you on this.

Regards,

Charles
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