Turbocharging the 1242cc 8v f.i.r.e engine

The standard 1242cc 8 valve f.i.r.e engine is a popular choice of engine to swap to the cinquecento sporting due to the fact it can be run directly of off the standard weber marrelli cinq ECU, and the basic seign is exactly the same as the 1108 engine.
And seen as the most popular big mod to do on the cinquecento is to turbocharge it i will cover the 1242 engine in a turbo tuning tech talk!

Before going ahead with the turboing of a 1242 turbocharged cinq it wise to decide what you actualy want form your engine as there are many specs and turbo etc to choose from when tuning it from a mild 90bhp right upto 150plus bhp.

Stage one small turbo low/high boost - 90-130bhp

The ideal turbo to start with in this spec is the small and responsive Garrett T15 turbo from some fords and vauxhall diesels which will ensure a flat torque curve starting as low down in the rev range as 2000rpm.
In low boost spec this turbo would be run at around 0.35 -0.4 bar of boost!, this should be combined with an intercooler mounted in the front grill from something such as a punto GT turbo or an astra diesel which will not only give more power but will help to keep the engine more reliable by keeping the chance of detanation as low as possible.
Running at such low boost means the standard compression ratio of 9.6:1 can be kept meaning power will be optimized and the engine will remain fuel effiecient etc, to put in the extra fuel required for the extra air flow made by the turbo a second injector will be required mounted in a plenum chamber ontop of the O.E throttle body,,Vanaaken developments then used a bosh 803 dark green injecotor (as used in the stage two cosworths) controlled by a fuel enrichment devise such as the mappable Aquamist MF2 with a boost input meaning as the air pressure reaches 0 and above (boost) the aquamist will kick in and deliver the extra fuel.
Because this turbo setup uses the standard ECU a precaution has to be made to stop the engine managment light coming on and that is to clap the 5 volt MAP sensor voltage so the ECU never sees positive boost pressure an therfore never nows the turbo is there.

With the basic turbo kit on it is now a wise idea to fit a free flowing exhaust syetm with a decat/sports cat and a free flowing air filter mounted somewhere where it can pick up cool air,,,these mods ensure the max power can be made from the turbo conversion!

Once all the pipework and plumbing is in and ready its time for a rolling road set up to see what it can do!!

Exspect to see around 90bhp on this setup with around 90-100lb/sf of torque!, if you want to squeeze the most out from this setup running low boost then its wise to free up the air flow into the engine by fitting a 36mm/40mm throttle body which will give around 6bhp onto the above figure (as proven on my own car), the 40mm throttle body does upset the standard map a little (rough idle,hesitation) but its a small price to pay as the turbo will come in faster.
And if you want to squeeze the power to around 100-104bhp then its wise to fit the camshaft from the punto 75.

High boost stage one

So with the above setup a possible 100-104bhp ish can be made but if you want more then you have to go high boost, to do this the first thing you have to do is lower the compression ratio,,,,a cheap way to do this is to fit a decompression plate, a 1.5mm decomp plate will lower the C/R too 8.5:1. This will lower combustion chamber temps as gasses are compressed thus alowing more boost and power to be made det free!
The next step is to fit a high flow 3-5 bar fuel pump to give not only the extra fuel but more imporatantly,,,the extra pressure!, this is beacause the standard fuel pressure on the cinq is set at 1-1.2 bar,,,,,and high boost applications run boost pressure as high as 1 bar which means the pressure will be equalized and no fuel will be injected.
To make this work an adutsble fuel pressure regulator has to be fitted with a rizeing rate function, plumbed in such a way that the standard injecotor continues to recieve 1-1.2 bar and second on boost injecotor recieves 3 bar pressure.

Now comes the good bit,,,,turning up the boost!!

0.6 bar on this setup should give around 110bhp

0.8 bar should see 115-120bhp

and running 1 bar will see between 125-130bhp plus!!

There are mods to be done to increase engine performane and reliability at this stage such as a full thermostaic oil cooler setup, porting and polishing the cylinder head, fitting an electronic boost controller to controller boost characturistics much better and uprating the H/T leads and spark plugs to a colder grade plug.

to be continued,,,,,,,,,,,,,,,,,,,,,

Stage 3 130bhp plus

At this point it is time to upgrade the small T15 turbo because it will be at its max flow limits and therefore the turbo life will be cut much shorter not to mension the boost the turbo creates will be getting heated up by the compressor wheel operating at a low adiabatic effieciency speed and pressure.
The problem is with fitting a bigger turbo is the increased lag which equals poor drivability, to combat this you can fit a larger compressor housing and wheel to the T15. This is called Hybrid turbo, the advantage now is the turbo will still spin up very fast and give great drivability using the smaller T15 turbine while but the larger compressor and housing will pull in more air and run far more efficiently, thus giving vast improvements in power and torque for the given boost.

An ideal conversion to do would be the compressor and housing from either a Garrett GT17 or a GT18 turbo, however if you plan for more than around 150bhp then it is wise to look into the larger T2 parts.

With the turbo sorted its now time to make the fueling more efficient to cope with over 130bhp, the best way to do this is to fit the Muliti Point Injection manilfold and cylinder head from the punto 75, running MPI will ensure an exact amount of fuel with be atomized into each cylinder and all with the added bonus of a better flowing manifold and head with bigger inlet ports and valves!
To control the MPI set up the standard ECU must be ditched for either the 75 ECU with a piggy back or even better a fully indipendant standalone management system such as the Omex 700 series ECU or Megasquirt etc.
With MPI and the hybrid turbo running 1 bar or just over of boost you can exspect to see highs off 145-150bhp.
To go beyond this its now time to consider a new bigger turbo, yes the drivability will be a liitle worse off but the overall power gains will be worth it, something such as the Garrett T2 watercooled turbo would be a good idea or a newer GT series ball bearing turbo such as the GT20 turbo.

For the best gains in power torque and above all reliability and efficiency it is a good idea to fit a set off forged low compression pistons which will give better fuel squash and there fore more torque etc, these can be very pricey but if your serious about power you need them.

As always with every engine there are weak spots and design flaws that can interfear with tuning and cause reliability problems, and when it comes to turbocharging engines that were never ment to be turbocharged these weaknesses can lead to lots of stops in the hard shoulder!! -

The first and mager problem with the 1242cc is with the inlet manifold and injection method design, in normally aspirated form it doesnt cause a big problem but in turbo form it causes each cylinder to recieve a different amount of fuel meaning the air/fuel ration in each cylinder is different.
This has a few knock on effects such as, rich or weak running cylinders, unessasery stress on the crankshaft, poor or non smooth power delivery, overall loss in power and torque etc but more than anything when the car is on the rolling road getting a set up, the probe up the exhaust is used to monitor the fueling for the engine as a hole, but even if the machine reads say 13:1 A/F ratio for the engine, number 1 and number four may be at 16:1 and 2 and three may be at 11:1 giving an average of 13:1 for example meaning the setup looks safe but two cylinder are running lean and two are running rich!
The reason why this happens is because number 4 cylinder on the f.i.r.e SPI engine has a large take off for the brake servo assistor which means there will be a slight pressure differnce and a loss of fuel down that line which cylinder foutr doesnt recieve, so tipically cylinder four is always the one to fail due to detanation.
And having the single point injector placed at the top of the manifold means the atomized fuel can be incorrectly distributed into all four cylinders, with MPI this problem is avoided all together.

The next big problem with most fiat engine f.i.r.e engines is head gasket failiure which causes a big problem on N/A cars so when turbo'd the problem is more serious, my theory on this is that the head design and running temps cause premmature HG failiure, i always use Payen gasket and ensure the engine never gets over 85 degrees, this has worked for me running 1 bar of boost and two head gaskets! so it should work on a better setup.

The only other problem area when turboing a 1242 especially high boost is the fact that the standard setup has no saftey features to protect against detanation (a serious issue with the f.i.r.e engines when things go wrong), i run a knock sensor fitted to the centre of the block which will soon feed information into an active knock controller so when knock occurs the ignition timming can be retarded to provent detanation