131mirafiori forum

I've heard the expression "engine BHP" and "BHP at the rear wheels". What's the difference? The 113 BHP that the Sport has, is this BHP at engine or rear wheels   ???  :)

As you will have probably gathered I'm a complete novice at any mechanics but I want to understand how the 131 works. The more questions I ask you experts, the more knowledge I'll build up. Apologies given in advance of any further silly quesions  ;) 

Most if not all bhp figures are at the engine. You loose around 30% through the transmission therefore a standard 131 sport would be around 80bhp at the wheels.

And SAE is measured at the engine without alternator, starter motor and other things, DIN is measured completely functional. That's why old american cars have such high HP's :D

Paul all question will be answered as best as we can.

maybe alternator and water and oil pump can absorb relevant power, but I don't think transmission could do that, there is almost no mechanical dissipation here and absorbing 20Hp would break down the gearbox.

Yeah but there is the chocolate diff that absorbs the power but Sid 131 should know as he has a lower friction lsd in his so maybe 10bhp more at the wheel  ::) ::)

You do unfortunately get losses through the transmission and therefore the BHP at the wheels is always lower that at the engine. Autos tend to lose more power than manuals too.

Thanks guys  :)

The chap I bought the 131R from is claiming that it was recently dyno tested and was 135 BHP at the rear wheels and 170 BHP at engine.

Anyone know of a dyno testing station around the Kent/Essex boarders (near the Dartford crossing) where I can obtain my own results from please?     

There's a few in basildon and rainham and i new of one at brands hatch.
[urlhttp://www.redlinetuning.co.uk/[/url]
http://www.tracknroad.com/ (http://www.tracknroad.com/)
 john mowatts near marks on th a127

This would mean the head is heavily modified and ported 130 TC head with large valves, proper lift , double springs, and side draft carbs, etc.

This would be fantastic, but ask him for a printout  The cost of such engine modification alone is probably ca 4-5 GBP.

By the way - I heard a guy claiming his Fiat 126 had 80 BHP, but he lost lost the dyno printout.  ??? ???

Talk is cheap.

Miro

I certainly hope he was right, but you can't just take it at face value and need to re-test it to know for a fact. Also note than not all dynos are accurate and many of them depend on data you provide on gear rations and diff ratios, wheel size, tire size... etc.   Differences in readings from two dynos can be as much as 20%.    

Incidentally, as Einstein reportedly put it" "HP sells cars - torque wins races".

M            

Miro,
no dyno print out with the paperwork  :-\

However, looking through the original restoration work carried out (not done by the person I just bought the car from). It's report say's 128 BHP @ rear wheels.

These are the engine modifications/Transmission & suspension/ body work carried out.....

Engine:
Full engine recondition including rebore, high comp pistons from Fiat 124, 1800cc, balanced, flywheel from Fiat130 Abarth.

Cylinder head - flow & ported & re-profiled/built up camshafts.

Adjustable camshaft pulleys

Custom extractors
 
Inlet manifold by Guy Croft

New twin 45 Dellortos carburettors

Electric fuel pump & larger diameter fuel lines throughout

Crankshaft grind 10 on10 balanced & micro polished

Radiator recored

Transmission & Suspension:

Bearings in diff & gearbox stripped & replaced

Shock absorbers - new adjustable Konis front & rear all new bushes

Front brakes up rated to Fiat Uno turbo discs & callipers

Brake Master Cylinder - Mitsubishi mated to car to be compatible for new brakes

Wheel bearings - all new

Body:

Car stripped to shell

Body bead blasted/bare metal repaint

Re-paint

Re-fabrication/fitting of front horizontal beams from firewall through to front.

Re-fabrication/fitting of vertical front pillars

Full rust proofing/ Under seal of car & wheel arches

Powder coating of axle assembly/ brackets & front beams





   

It's standard to derate power at the wheels at around 20% of power at the flywheel, losses are higher still if it's 4wd.

I have seen where they convert mk1 ford escorts etc from leaf spring suspension to four trailing arms and panhard rod ala fiat 131 but the whole setup is on a much smaller scale ( tube size etc ) I cant remember where I saw this but they said this set up puts 30% more power on the road than leaf springs would ?  presumably because of axle tramp etc ?

Paulcas,

Based on the data you presented it looks much, much better , but I would find 128 bhp on wheel more likely than 137.( Assuming 20% power drop expected from engine to wheels , likelihood that that the engine has 160 bhp and not 170 bhp is much greater.

Re porting : what are the porting results. Unless the airflow has been actually measured you can just assume someone took a grinder and enlarged the port

One item caused my major concern ;

"Crankshaft grind 10 on10 balanced & micro polished"

Please remember this part works quite hard and require very had working surface. The working surface hardening  cannot be replicated. Most competent expert mechanics highly believe crankshaft grinding is an absolute no-no. Especially since the standard 131 crankshaft is known to be indestructible.  

I think i is a weak spot.

Miro;

PS: How high can you rev your engine ?
Will it go up to to 8000K ?

M    

  

Hi Miro,
thank you for your observations and technical advice. I am no way a mechanic and I have simply copied what was supplied to me on paper, so really appreciate you taking the time to work out what's been done.

I'm told that the person who owned the car at the time of restoration spent around NZ$ 25k and the work was carried out by reknown NZ experts - whatever this means!!

Airflow & Porting: The only data I have is that work was carried out to both areas. So hopefully they were measured and enlarged as you say.

Crankshaft regrind: No other data. Hope I have no problems with this area  :-\

Rev range: I have the camshaft specification. The cams have a mechanical inverted bucket type profile. The RPM power range is between 3500 to 7000+ with excellent mid-range torque and Hp (no data for latter).

When I took it out recently, it quite easily rev'd to just over 7k, although I felt it wanted to go further, I didn't push it as I'm still getting to feel how the 131 behaves.

I plan to have a dyno test done soon to establish it's curent power rating.         

As far as I'm aware the 2 litre twin cam has a steel crank as standard (rare) so I don't think it is a 'weakness' in the engine. However, there is a big difference between an engine being used for standard road use and use in competition. Crankshaft regrinds used to be quite common here in the UK but now few people do this as mostly a replacement engine is fitted instead as it is cheaper as labour charges are so high. If building a competition engine I can understand it is better to start with new parts, that is if you can afford them ::)

The 2000 cranks are steel but they were also nitrided which is a case hardening process that should be redone if the crank is ever reground and I am sure when I read up on this that there is a significant failure rate on manufacture ie the cranks distorting because of the extreme heat.

Just received some further info from a previous owner of the 131 ( cheers Duncan  :) )   

Engine: The brief was to build a fast road-use motor and everything necessary to do that was done. More could have been got out of the unit but at the expense of it being as user-friendly.

Crankshaft: Reason for grinding was because there was some wear. The level of grinding required would not have penetrated the thickness of the case hardening.

Cylinder head: Work carried out by a very experienced mechanic who works on 20+ cylinder heads a week - everything from standard repairs to full race work. The head would have been fully flow tested and the head was set up for fast road use.

 :) :)

Paulsac !

This is very good news and very reassuring !.

Mirafioriman :

You said " As far as I'm aware the 2 litre twin cam has a steel crank as standard (rare) so I don't think it is a 'weakness' in the engine."

Misunderstanding : it actually is much stronger that used in Lancia Delta Integrale for instance.  Fiat 131 crank is  one of the strongest - of not the strongest !  It is a very strong element of the engine.

Weakness comes from regrinding it.  Do not believe in grinding , polishing - yet . but not grinding.

Please look at this : http://www.guy-croft.com/viewtopic.php?f=3&t=2031

Miro