Fiat Punto 1.8 16v HGT Abarth Stroker Conversion Project

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John Finch
Posts: 3
Joined: April 3rd, 2015, 3:51 pm

Fiat Punto 1.8 16v HGT Abarth Stroker Conversion Project

Post by John Finch » April 9th, 2015, 3:23 pm


This article is rather lengthy, due to conferring to as much information within the article as possible to assist any other reader or interested person wishing to undertake a similar project.

A short biography about myself:
It is said we are all the product of our parents aspirations and the circumstances we grow up in. My father and his buddies were seriously involved in motor sport in the late 1950’s through to the mid 1980’s, thus I grew up and was weaned on Castrol R, noisy machines and race and rally events.

When my dad was in the RAF he rode about on a Matchless G45 motorcycle. The bike accompanied the family when we immigrated to Port Elizabeth, South Africa in November 1955. This bike was eventually fully race prepared for no other a person than Geoff Duke for him to race at the PE 200 mile speed trial in 1959. A road race through the countryside over four 50 mile laps like the Isle of White TT we know today.

At the time dad had a Fiat 500 Topolino that was modified within an inch of its life and he also raced the little machine. The Fiat 600 came out in the early 1960’s and was tinkered with, until eventually becoming a full race 1000TC Abarth machine. Dad won many race and 8 hour endurance events in the Abarth.

We had lots of Fiats in the family with the last one being the Fiat 131 Racing, which was only made in South Africa. What a machine! Only 20 odd 131 Racings ever appeared, as this vehicle was never homologated due the Alfa/Fiat factory in Britz, near Pretoria, South Africa being forced to shut down, hence their rarity.

As for myself, I finally finished the education grind and started my career as an automotive engineer for the likes of Ford and eventually at Nissan in South Africa where I was the Manager/Supervisor for the Experimental Workshop/Engine Dynamometer section.

I was involved in the rally scene and held both drivers and navigators competition licences. I built rally/race engines and also stroker conversions utilising diesel crankshafts that I could get to fit.

I returned to the UK permanently in 2000 and moved up to Scotland in 2009.

Having being forced into early retirement due to health problems I was looking for a project to keep myself busy. A Fiat Punto MK2B 16v HGT Abarth came to my attention.

I purchased the very clean 2005 Fiat Punto MK2B 16v HGT Abarth (Engine Code: 188 A6000 – Euro 4).

I was looking at a complete engine rebuild as the mileage and oil consumption was getting very high. An engine and gearbox was offered to me with only 31k on the clock through a friend of mine.

Before doing a transplant I thought it better to strip the donor engine down and replace all the usual wear and tear items. The engine was in perfect condition and practically brand new with no visual or measurable bore wear or any sign of wear/scuff on the pistons, crankshaft or camshafts etc.

At this point I was a happy man, but a thought started to fester in the depths of my mind as to the modifications I could do whilst the engine was in bits and pieces.

I very soon hit a brick wall after an intensive Internet search for engine performance parts. Let me explain:

1. Only Columbo & Bariani (C&B) did camshafts with standard base circle diameters. Any reground camshaft (Piper or Cat cams) would require going to mechanical lifters with shims and at the end of the day cost nearly as much as the C&B camshafts.
Fitting a reground camshaft reduces the base circle diameter by a few mm, thus the hydraulic lifter oil supply gallery can go of phase not filling up the lifter when it is on the base circle radius phase where it is supposed to be for correct hydraulic lifter operation. So C&B camshafts it will have to be then.

2. The vehicle is fitted with the Hitachi MFI-601 ECU that is not remappable, reflashable and completely locked. This particular ECU also learns that there is a piggyback fitted and reverts back to standard values thus rejecting piggyback ECU’s. I cannot go to stand alone ECU’s either due to the interface with the current vehicles set up. I would have to investigate the fueling situation later and come up with a plan. This situation also means I will be stuck with 7150rpm as the maximum rev limit as well.

After an exhaustive Internet search and contacting a number of aftermarket ECU suppliers regarding compatibility of their piggy-back units with the above timing events, only AEM in the USA were kind enough to get back to me with a solution. Should I not be able to get the fuelling right on my own I would have to go the AEM route as they did say that their unit can read the phonic wheel timing.

3. The only 4-2-1 so-called performance manifold is available from Supersprint. Would this manifold suite the modified engines state of tune. In my professional opinion it would not. I would have to develop and build my own 4-2-1 tuned length manifold once all the engine mods are completed as engine capacity and cam timing has a big effect on exhaust gas flow.

It was beginning to look as though I had an engine builder’s lemon on my hands, not to mention the complexity of the electronics of the rest of the vehicle to contend with.

I purchased a full workshop manual and studied all the necessary chapters relating to the engine build (dimensions, tolerances and torque specs) and specifically the fuel injection system operation and timing parameters.

The first major thing I noticed was the unusual crankshaft timing gear (phonic wheel) set-up. Not the usual 62-2 as on most crankshafts, but three graduated timing marks on one side of the phonic wheel and three on the opposing side.

Basically I was back to square one again so had to use the standard phonic wheel timing events no matter what I did to the engine.

There was basically very little that could be done to the engine to get a meaningful power improvement. Other than bolt-on boy racer go-faster noisy bits, aftermarket off the shelf parts were few and far between.

I was not going to spend all the time and money to build an engine that I could only extract 15 to 20 additional horsepower out of, if that, all happening near the redline, and lose out on mid range torque and everyday driveability. This car is for everyday road/touring use after all.

So what did I have as a basis for the project? Probably one of Fiat’s finest engines waiting to be unleashed? Aurelio Lampredi would be proud!

The standard engine specifications are as follows:
Bore: 82.0mm
Stroke: 82.7mm
Compression ratio: 10.3:1
Cubic capacity: 1747cc (not a true 1.8)
Power: 96Kw at 6300rpm (130 bhp)
Torque: 164Nm at 4300rpm

- The piston crown to deck measurement is .15mm
- The standard piston compression height is 28.5mm
- The standard connecting rod length is 145mm centre to centre
- The standard crankshaft throw is half the stroke at 41.35mm
- The standard deck height (block height) is 215mm.
- The standard cylinder head volume is 39cc
- The standard MLS cylinder head gasket thickness is .40mm

The stroker project:

I have built quite a few rally/race engines in the past and even stroker engines utilising longer stroke crankshafts into other engine blocks and this was the route I now intended to follow. After all, ‘There is no replacement for displacement’.

I was thinking that if I could bore/stroke the current engine from 1747cc up to the 2000cc mark and have a ‘proper’ 2.0 litre engine in my Fiat Punto HGT Abarth with no external sign of any modifications having been done.

The Alfa/Fiat parts bin is quite large and a number of parts are interchangeable between engines so I had a good look to see what was out there.


- The Alfa 2.0 16v TS crankshaft has a 91mm stroke.
- The cylinder bore would need to be machined out and honed to 83mm diameter to give a maximum of 1970cc.
- The Fiat phonic wheel will not fit.
- The connecting rod length would now have to be 140.850mm giving a connecting rod to stroke ration of 1.54:1
- The H-beam connecting rods seriously foul the bottom of the cylinders.
- The piston skirts protruding excessively from the bottom of the bore fouling the piston oil sprayers, not to mention a compression ratio of 11.67:1 which is not suitable for everyday use.

The next crankshaft on the list was from an early Fiat Diablo 1.9 JTD (115hp) with a 90.4mm stroke.
The big end and main bearing sizes were the same as the 188A6000 engines. Namely; 50.8mm diameter big end journals and 53mm diameter main bearing journal sizes.
- The phonic wheel fitted with a slight removal of material on the flange edge so no fouling interfered with fitment.
- The 1.9 JTD crankshaft received was practically brand-new. I measured up all the journals and every journal was within tolerances.
- The connecting rod length would have to be 141.150mm and with a 83mm diameter bore a capacity of 1957cc.

Utilizing the perfect condition standard 82mm pistons and bore would give me 1910cc.

I was of the opinion a rebore and a new set of 83mm pistons, not to mention the cost, would only give me 47cc extra capacity. The cost of the rebore and new pistons would easily cover the C&B camshafts I was intending to purchase at a later date. Besides, boring out the block from 82mm to 83mm leaves a thin bore wall, which is not ideal.


Cylinder head:

- The head was stripped of all parts including oil gallery plugs.
- All the ports were cleaned up removing casting flash and any misalignment. - The valve seat machining marks in the runners and the gasket/manifold matched on both the intake and exhaust sides.
- A final 80-grit cleanup was done on all the ports.
- The valve seats were given a radius cut and recessed by 0.75mm and all
machining marks blended into the combustion chamber.
- The valve stems were also shortened by 0.75mm due to retaining the hydraulic lifters.
- The combustion chambers were volume measured and optimised to all measure the same volume. The final result gave me just on 40cc*.
- New Viton valve stem oil seals were fitted throughout.

*Note: I could not remove much material from the cylinder head combustion chambers to lower the static compression ratio further, so had to use a .82mm MLS cylinder head gasket which gave me 10.67:1 static compression ratio.


Since the standard 82mm pistons (-4.12cc recessed crown) were as new, I decided to stick with the 1910cc stroker conversion giving an increase of 163cc in capacity.
- The pistons were marked relative to the bore positions and carefully cleaned.
- Each piston had an additional 8x 1.75mm diameter oil return holes added to the oil control ring groove. 4 holes on either side of the wristpin.
- Each piston was weighed and the heavier pistons had material removed to weigh exactly the same as the lightest piston that was 283 grams*.

*Note: Any removal of material from the piston to reduce its weight must be done where material is available to do so and left smooth with no gouges/scratches that might propagate fractures leading to piston failure.

Piston rings:

The original rings were of the Goetze type with a single piece oil control ring.
I opted for the NPR ring set with a three-piece oil control ring for better oil control and increased piston stability in the bores
- All rings were gaped to Fiat piston ring nominal clearance specifications for this engine.

Engine block:

- The bores were deglazed using 320-grit Flexhone.
- The block was ultrasonically cleaned and oiled and the exterior painted.
- The oil galleries were cleaned again.

Note: On the first dry assembly the connecting rods fouled the bottom of the cylinders, which had to be ground back to clear the connecting rods by 1.5mm.

Piston oil sprayers/cooling jets:
As the pistons were now 7.7mm further down the bore at BDC I removed 8mm from the ends of the oil sprayers. The inside diameter of the oil sprayer was not affected in this modification. The oil sprayers now cleared the piston skirts at BDC.

Custom H-beam connecting rods:

Having decided on the 90.4mm stroke 1.9 JTD crankshaft I ordered custom H-Beam connecting rods made to my required dimensional specifications which are as follows:

- Between centres: 141.150mm
- Big end dia: 53.897- 53.909mm
- G/pin bush material: Aluminium/Silicon/Bronz alloy bushing
- G/pin bush inner dia: 20.006 – 20.012mm
- Big end width: 25.705*mm
- Small end width: 21.850mm
- Fasteners: 3/8” ARP 2000 bolts

*Note: Normally the connecting rod centres on the piston and not on the crankshaft. The standard big end and small end width on the Fiat engine is 21.95mm. The big end journal width is 26.829 - 26.879mm leaving the connecting rod to float about over 4.8mm across the crankshaft big end journal.

The bearing shell is only 19.5mm wide. Careful measurement of the crankshaft oil gallery to the side of the bearing shell with the connecting rod over to one side (extended cornering for example) left only 2.8mm of bearing surface left to the oil gallery. A lovely situation to get a loss of oil pressure and a blown engine, especially during track days.

To correct the situation for piece of mind I now centred the connecting rods on the crankshaft utilising the above custom connecting rod dimensions.

Clutch kit:

Due to the increased torque and power output I used the clutch kit from the Alfa Romeo 2.0 TS 155bhp engine.

Final actions prior to engine assembly:

- Pistons, rings, wristpins and clips were re-weighed and corrected to the lightest weight piston assembly.
- Connecting rods with bearings weighed and corrected to the lightest weight connecting rod.
- Crankshaft, flywheel and pressure plate balanced to zero static and dynamic balance.
All parts were spotlessly cleaned and wrapped in Clingfilm until required for final assembly.

Final engine assembly:

The engine was assembled using assembly lube, new OEM seals, new cylinder head bolts, new water pump and timing belt kit and a new clutch and thrust bearing kit. All bolts were torqued to Fiat’s specifications.

For the moment the standard camshafts were fitted and timed up as per specification.

The complete engine/gearbox assembly was then fitted to the vehicle.


As mentioned above, the Hitachi MFI-601 ECU was a problem. The vehicle also has an in-tank fuel pressure regulator with a single fuel line to the fuel rail.

I manufactured a fuel tank return adapter, bypassed the in-tank fuel pressure regulator and fitted an adjustable fuel pressure regulator in the engine bay with a 8mm fuel return line back to the fuel tank.

The Hitachi ECU is self learning as previously mentioned, so providing I fitted the correct size injectors for the engine capacity/estimated power output, the ECU should sort out the short and long term fuel trims by itself when in closed loop mode.

At high/full load rpm when the ECU is in open loop condition, I had to ensure there was no leaning out of the fuel mixture.
- The standard injectors are IWP006 units (226cc/m at 3 Bar at 80% duty cycle).
- I calculated that I required the IWP042 units (250cc/m at 3 Bar at 80% duty cycle) for a 150 to 160 bhp engine power output.

The adjustable fuel pressure regulator required adjustment to 3.2bar to give Lambda 1 (14.7:1 AFR) reading when checked on a Bosch exhaust gas analyser at 2500rpm which is the MOT exhaust gas test protocol.

On Road driveability and performance:

I filled up the fuel tank with 98 RON petrol just in case any detonation was going to be present.

After 1000 miles run-in period and an oil and oil filter change the car was due for an MOT and passed with a slight adjustment of the fuel pressure regulator down to 3.1Bar to get back to Lambda 1 again.

The IWP042 injectors are thus apparently perfect for the current capacity and state of tune.

There were no signs of any detonation during the run-in period, or during the last three tankfulls of 95 RON petrol either. Under WOT from 1500rpm to 6500rpm in 4th gear there are no detectable signs of hesitation, flat spots or surging anywhere across the rev range.

The engine is turbine smooth in operation (all the balancing is a must) and a joy to drive.

In conclusion:

I have not done a rolling dynamometer run yet as I first wanted to sort out all the wrinkles, if any, first.

The current power output is estimated at 150-155bhp according to ‘Horsepower Calculator’ depending on barometric conditions?

I still have to get around to fitting C&B camshafts and build the tuned length exhaust manifold and free-flow exhaust system.

Another 10-15 hp gain perhaps?

The 1910cc stroker conversion in the 1040Kg Fiat Punto HGT Abarth has made a major difference especially in the torque department. The power increase is certainly noticeable and the vehicles driveability and performance has transformed the driving experience.

All in all an interesting, time consuming stroker conversion certainly worth all the effort. The early Castrol R infused bloodstream has never left me and has become part of my DNA.

Would I recommend going down this route? Oh Yes!
A rear view of the project vehicle
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Combustion chamber cleaned up and volumes optimised
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Port matching on the cylinder head
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All porting and combustion chambers done
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A view down the cleaned up ports
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Block painted and honed ready for assembly
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Inlet manifold ports cleaned up
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Shrtened oil sprayer and view of connecting rod relief at bottom of bore
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Piston near BDC showing connecting rod relief
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A view showing connecting rod to crankshaft journal clearance
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Rotational assembly fully installed and torqued up
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A view of the pistons and bores prior to fitting the cylinder head
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Camshafts fitted and timed up
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Front view of the cambelt etc
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Front view of the completed engine
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View of completed engine
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Posts: 333
Joined: July 28th, 2010, 3:09 pm
Location: Leiden, The Netherlands

Re: Fiat Punto 1.8 16v HGT Abarth Stroker Conversion Project

Post by TomLouwrier » April 9th, 2015, 9:19 pm

Hi John,

What a lovely write-up!
Always good to see a pro at work and double so since I'm running the same engine in my Coupe (nearly 340.000 kms in 16 years and still going quite fine). Your project answers a lot of things I've been thinking over for when the Coupe comes out of daily duty and into project land.

Have you ever considered replacing the Hitachi ECU with the Bosch setup as used by Alfa on their version of the 1747? That has a twin spark head (who cares?) but is the same engine really. Alfa fitted hotter cams too, their 1.8 performing like a Fiat 2.0 and their 1.6 more or less like the Fiat 1.8.
Clear case of marketeers' triumph over engineers....

Thanks, will be in touch for sure.


John Finch
Posts: 3
Joined: April 3rd, 2015, 3:51 pm

Re: Fiat Punto 1.8 16v HGT Abarth Stroker Conversion Project

Post by John Finch » April 9th, 2015, 10:07 pm

Hi Tom,

Many thanks for the compliment.

My particular Fiat fitted with the Hitachi ECU is a Euro 4 specification vehicle with fly-by-wire throttle, dual climate control, ABS, ASC (anti skid control) and two pre catalytic converters both fitted with O2 sensors and the main catalytic converter under the floor with another O2 sensor just behind it.

The speedo/tripmeter runs off of the ABS system as well.

I did in fact look at the Alfa wiring harness as an option, but to be honest the complexity and work involved was ruled out as I was dogged in my determination to get the current setup working and I am happy to report that after a 1000 miles plus of running the new engine in, I am more than happy with the results. All the electronics in the car are fully operational.

With reference to the Alfa 1.8 16v TS power output, it depends where you get your information from. The CF3 specification Alfa's have exactly the same camshaft specification as the Euro 4 Fiat HGT's. 9mm lift on the intake camshaft and 8.5mm lift on the exhaust camshaft. The detuning was to meet emission targets. For example the Alfa 2.0 16v CF3 engine only puts out 150 bhp!

If you have a gander at the Cat Cams website they say the lift on both camshafts is 9.5mm. I searched high and low for a pair of these camshafts for months but could not find them anywhere. I visited many a scrapyard with my vernier in hand without any joy. Who knows?

I trust the above answers some of your questions.

Best regards
John Finch

Guy Croft
Site Admin
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Location: Bedford, UK

Re: Fiat Punto 1.8 16v HGT Abarth Stroker Conversion Project

Post by Guy Croft » April 10th, 2015, 3:49 pm


Guy Croft, owner

Posts: 71
Joined: August 7th, 2013, 10:37 pm
Location: Pembrokeshire, Wales, Uk

Re: Fiat Punto 1.8 16v HGT Abarth Stroker Conversion Project

Post by Slim » August 9th, 2015, 8:53 am

Great post John, thanks.

Re: ''I cannot go to stand alone ECU’s either due to the interface with the current vehicles set up''

Can you elaborate on this point please?

Also, I'd like to see a dyno printout...



John Finch
Posts: 3
Joined: April 3rd, 2015, 3:51 pm

Re: Fiat Punto 1.8 16v HGT Abarth Stroker Conversion Project

Post by John Finch » August 26th, 2015, 5:03 am

Hi Liam,
Appologies in the delay in getting back to you as I had not visited the site in ages.

To answer your question regarding the fitting of a stand alone ECU I respond as follows: The vehicle is a Euro 4 model (drive by wire) which includes traction and stability control, ABS, climate control and all the goodies not found in earlier models. Going stand alone would of course cost a fortune, lose a lot if not all the current features, not to mention the phonic wheel at the end of the crankshaft only having three timing pickups and another three at 180 degrees which would mean having to fit an external 62-2 teeth timing wheel on the crank pulley.
I looked at all and every option regarding the timing and decided to rather fit IWP 046 injectors ratted at 250cc/min @3 bar (as fitted to the Renault Sport 172 HP, fit a return fuel line back to the tank with a fuel pressure regulator set at 3.2 bar (the regulator in the fuel pump was bypassed) and set up the fueling in closed loop mode which was on a Bosch exhaust emmissions analyser at my friendly MOT station. So far the Hitachi MPI ECU has not complained.

As per a rolling road printout as you mention, this has not been done for the following reasons: Rolling road testing or evaluation of the vehicles performance is rather pie-in-the-sky due to numerous factors I am not going into here, besides, I am in Inverness, Scotland and there are no rolling road facilities here or even close.
What I did do prior to the engine swap was on-road real world performance checks which included rolling start acceleration tests over 1/4 mile and 1/2 mile distances noting the times and indicated speeds (three runs at each distance). the quarter mile distance speed runs were deemed too short to get a meaningfull result as the vehicle was nowhere up to speed in the top gears where it matters the most on the open road so only 1/2 mile runs (on a private road) were compared to the stroker engine once it was run in. For example the standard engine gave me an average of 105mph at the end of a half mile which was entered in third gear and a speed of 30mph. The 1910cc stroker engine exits the half mile run at an average of 120mph. A 15mph increase which is quite significant considering standard camshafts and exhaust are still fitted.

Now that it has been proved that the current fueling setup is managable, the next obvious step is a decent pair of fast road camshafts and a bespoke tuned length exhaust manifold and exhaust system which may give me another 15-20 bhp. To be honest for all the money another 15-20bhp will give me it's not actually worth it considering how well the car is going at present. But then, I can always change my mind later on!

2014-12-08 21.08.26.jpg
Fuel pump fitting for return line to tank
2014-12-08 21.08.26.jpg (32.78 KiB) Viewed 13515 times

Posts: 65
Joined: February 11th, 2013, 6:37 pm
Location: Cape Town. South Africa

Re: Fiat Punto 1.8 16v HGT Abarth Stroker Conversion Project

Post by FiatRally » April 14th, 2017, 1:12 pm

Hello John,

I have found a Punto HGT 1.8 motor with very low km here in South Africa.

For now it will go into storage.

I have worked through your post a few times and it is fantastic!

At this point I am hunting for a good std early 1.9 crank for this engine.

I will use this engine in a 131 race car.

What would be interesting is what is the actual wall thickness at its thinnest point on these blocks? The conrods looks like a very costly excercise?

We did not receive many HGT cars here so parts is a problem. Do you know the engine code for the engine that you got the crank from?

Any more info and help will be appreciated!



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