Fiat 131 Abarth
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Fiat 131 Abarth
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| EVO II ENGINE My rallycar engine exploded one time too many last march. I was very frustrated and then I thought, why I dont build next engine as good as it is possible to do it?? Here you can see something of my dream engine, it will be true!!
Commonly about TC engines. Basic engine in these TC type engines is the same, all the way to Them/Croma/Integrale. In the middle of eightees they turned cylinder to opposite way, but even that is interchangeable with earlier heads. At the same time they also modified block so, that old fashion oilpump was changed to more modern, and at that meaned side axle was junk, it was not used ever since. Earlier that same axle used also fuel pump, and distributor, but these late models had injections with electric fuel pumps, and Digiplex ignition that was moved to end of camshaft, so why we should use axle just for oilpump? In most 2,0 models block also has balancing shafts, and it gives about 15-20kg extra weight to engine, and turning masses propably more than 5kg. Ofcourse I didnt want balancing shafts, but neither I wanted sideaxle.
Block What would be then the best possible block. I had to read my rally technical regulations book very carefully, so I wouldnt brake any rules. I chose Croma block, it dont have side axle, and it didnt have balancing shafts either. So I could dump axle+pulley, alltogether 1,6kg, also belt will be shorter. This new model have oilpump on front end of crank, it has suction pipe made of steel tube, so if I drive to rock or something, it only bend. Aluminum leg usually brakes and then it sucks air... This block looks exactly like old block, only no sideaxle, some threads too many, some less. I will need to make some and plug some I dont need. One little disadvantage is that it dont have alternator mounting at all, so I need to make it.
Flywheel, stroke, bore, rods, flywheel. These are a lot more difficult things that choosing right block is. 2.0 litre Fiat TC have 84mm bore and 90mm stroke. We have been using for couple of years 86mm bore, this increases capacity to 2091cc. Our rally regulations say that crank is free, except longer strokes are not legal. Bore is free also. Very much bigger bore isnt reasonable, and almost impossible because wery narrow cylinder distance. 87mm should be possible, I have heard 88mm been used too. I talked with my machinist and he sayd we should use minimum of 87mm, that would give 2140cc. These pistons are not available anywhere, so they must be custom made. We chose Wiseco. Main problem getting power in 2,0 TC engine is, atleast my opinion is, that long stroke vs small bore give long narrow tube which is slow to fill and get empty in high rpm. Long stroke also gives very big piston speeds, this mean piston problems, excpesially if pistons are heavy. Solution to this is shorter stroke. There is one rare Seat 1430 Especiale with 1,9 litre Fiat based TC engine. It has 86,6mm stroke crank, problem is that it is rare, actually almost impossible to be found. There is also possibility to regrind journals so that it give shorter stroke, that isnt so easy as it sound. Then you should use smaller bearings, that mean, you couldnt use Fiat rods, also nitrited crank cannot be grinded without new nitring, and that is pretty expensive. Ofcourse Italians produce 86mm stroke billet cranks, but you can guess how expensive they are, 2500 Euros/each. That would also cure another problem, original crank has only 4 counter weights. These billet cranks havare fully counterweighted, giving you possibility to use even higher revs. So, only reasonable solution is to use original crank, knife edge it. We will make it 2kg lighter than original was, that should make problems yet, actually balancing just gets more correct, because piston and rod is also lighter. We can use either Croma type crank or RWD type crank. Old crank is possible to modify so it fits to late type block and oilpump. Rod-stroke ratio with stock rods is 1,61 All factory Kitcar homologations show that they use 1,70-1,80 rod-stroke ratio. In our local top rwd rallycar, GT Corolla, is always used with longer billet rods, that give 1,75 ratio. There is cheap cure for this. Chevy small block rods are made for 2,0" rod journal, same as Fiat. Stock Fiat rod is 5,7", and there is many options for 6,0" rods. This rod gives 1,69 ratio, that is more like it should be. There is also 6,125" that would give 1,73 and 6,2" that would give 1,75, but these either have rod journal 2,1" or they are made by some expensive rod maker like Carillo. Those cost from three to four times what Scat cost. When we start using those longer rods, piston of course come through block, here you can see how much it does. Stock piston has 38mm compression height, and longer the rod is, shorter piston is needed. That is actually a good thing in race engine, lighter piston is better, though it will rattle more, but noise and wear isnt usually problem in these engines.
Rod More length compression height needed rod-stroke ratio 6,00" 7,62mm 30,4 mm 1,69 6,125" 10,48mm 27,5 mm 1,73 6,2" 12,4mm 25,6 mm 1,75 Proper race pistons can go as low as 25mm, so all of those are possible. I have thought this for long, and I decided that I will start using 1,69 rod-stroke ratio and I will buy 6,0" long Scat rods. Scat is one of the cheapest, and they look best :)
This means that cost will be still reasonable, and some experts told me that it might be even worse when using longer rod. Reason we are using longer rods is, that because angles are different, piston will stay in TDC longer than earlier. That will cause better burned air/fuel mixture = more power. Also longer rod dont push piston agains cylinder wall as much as shorter rod does, this mean less friction taking power, and also less wear. Many have asked how they fit in to Fiat block. They are littlebit narrower at bottom end, but bearing is wider than Fiat bearing. We didnt do a thing to that. Biggest problem was that this rod maximum distance sideways is 87,5mm, so its impossible to fit in to smaller bores... I have 87mm pistons, so I only needed to grind 0,25mm off from both sides. Im not sure if some other manufacturer have narrower Chevy rods. I just bought new state of the art pressure plate, Sachs MFX, its aluminum casing, steel spring and friction ring. Its also possible to by new parts to it, so if friction ring wear out, I just need to buy new ring, not fully new plate. It weights only 2,6kg, and its about 1kg less than my present pressure plate. I found out that its not possible to assemble my new pressure plate to my old fly wheel. I sold it to US, and now I need to make new flywheel, I will try to make it even lighter than my earlier was. It was 4,3kg this will weight 3,5kg, I hope.
Less rotating masses Here you can compare how much stock parts, my present parts, and my new parts weights. stock present EVO II crankshaft 18kg 18kg 16kg clutch plate 1,3kg 0,75kg 0,75kg flywheel 9kg 4,3kg 3,75kg pressureplate 5kg 4kg 2,6kg connecting rod 815g 750g 680g pistons 750g 496g 452g sideaxle+pulley 1,6kg 1,55kg Im not going to use it! alltogether 39 kg 32,8kg 26,2kg Some of these weights are estimated, some are accurate. I will have about 6kg less ROTATING masses, that is quite a lot!!!??? I think it will accelerate like real race engine now? I will also start using aluminum pulleys, that might take some time, its not the first thing to do. I do have adjustable pulleys with aluminum center allready, but Im making EVO II from them too, even lighter!
Lubrification This is the place to stop, and start really thinking.... Lack of oil is the most common reason breaking TC engine, usually rod bearing get stuck. Common reasons that cause this:
Solutions ofcourse are; new pump, bigger sump for more oil, good quality oil, proper baffles and blueprinting. We allready have new and big enough sump, thats the only thing we DONT need to change.
Sump have baffles and reservoir boxes on sides. We also use another "sump", kind of total baffle between sump and block. These must be done again because oilpump type changes.
Stock oil draining from head is going to be
changed totally. Originally it drains from two 12mm holes per side, straight
against rotating crank! That cannot be good for either power, or oil aeration.
We will try to put somekind of pipes to drain oil back to sump straight. Oil cooler is must item. When we started to use Ritmo Abarth oilcooler and thermostat (opens at 82C) we also attached VDO oiltemperature meter. We found out that oils are unbelievable hot if stage is over 5km. Summertime temperatures go over scale if stage is longer than 10km. Temperatures over 150C.... This CANNOT be good, David Vizard tells optimal temperature would be 80C, and thats where Abarth engineers have set thermostat too. We changed to biggest cooler we could set to airstream beside radiator. Even we have XXL oilsump, and cooler is pretty big too, our latest engine had over 140C on long stages... It dont make me smile... We have no good cure for that, we should use even bigger oil cooler, but then its always behind something, and I think thats not reasonable. Only thing I can imagine is that we should use drysump with 10-20litre reservoir. This would guarantee airless oil, and pump wouldnt suck air anymore. We could even make negative pressure to block, that would be good too. But price, pumps only cost over 1000 Euros + reservoirs etc. that brakes me a bit. Atleast now... Abarths had those at Alenīs time. Original breather is little too small, but what can we do about it. Not much, just be sure you dont use any smaller hose than hole in block is, also breather tank MUST have big enough air hole as you could. I should sometimes measure how much block inner pressure is, if there is pressure, that isnt good for power. Good way to help to save engine is to use oil accumulators. They will pump pressured oil back in engine if something goes wrong. We will use Moroso product, 1,5quart size.
Cooling Fiat have originally good waterpump, but there is two different models in 2,0 engine. Earlier, that have welded pulley, and later that have pressed pulley. Newer is assembled to third body Mirafiori and that time other bodies too. Late model have longer pump axle, propably they were looking for more length between bearings to give them more lifetime. Also later type pulley is stronger, but also heavier. We use later type, we had one pulley failure in rally with that earlier type, and that was enough for us. Original 131 cooler is big enough, if its working properly. We took our to professional cooler repairman, and he opened it, and reassembled it. There was about ten pipes stuck. Original electric fan is good too, but heavy and very thick. We use original now. You must NOT take thermostat off!! It sure is terrible mess originally, but you must have somekind of thermostat, if you have overheating problems, you may even get it worse with no thermostat. Water flow too fast and it dont have time too cool in cooler. This is a fact. Problems is that there isnt available cool enought thermostat for rallying use. And original thermostats are very expensive too. We made it like this. We took away all original hoses, then lower hose straight to pump, upper hose straight to cylinderhead. Then, you know that "leg" for hose in cylinder head? Take it off, and you can see there is place for normal type thermostat! It isnt propably designed for it, but its possible to put thermostat in there, and it still works too. Because water dont flow at all when engine is cold, engine heats really quick, then it works pretty fine. There was another problem with pipe going from pump to inside cabin, it always twisted a little and it started leaking from pump side end. We took hack saw, cut it, and made new end from 8mm thick steel sheet. No twisting after that and its worked fine. Waterpump and alternator drive ratio should be dropped. Originally best power is at 6200rpm. Now engine goes up to 8000rpm, and alternator turns 30% faster than it should. I have used 1,6 litre tc pulley, its little smaller and fits straight in, it drops speed about 20%. If we didnt drive at street speeds at all, we could make it lot smaller, in US they use in circuit about 50-70mm pulley. But we just cannot use that small, even now, when engine is idling, it starts heating pretty fast. I can cure it by keeping rpm at about 2000 for a while. These things are working nice now, and we can use them in this new engine. Small problems come when Croma block is used. Croma engine is attached to engine bay by lifting it from the pulley. Because of that pump have 8mm bolts (fine threats, dont loose them), this propably is cured by drilling bigger holes to 131 pump. If not, its possible to use Croma pump too, hose goes in right angle, and its possible to hacksaw extra aluminum off. There is one difference more, pipe going to inside cabin is changed to hose, this might be a problem, because it goes under header in 131. I didnt measure axle length, it might be different, I will check it out.
Exhaust This will give me lots of trouble. Our present header is 4-1 type with 40mm primary pipes that are 800mm long. After that there is about 80cm 55mm pipe and rest is 63mm with one very large silencer at back. Its propable that we need to try also 4-2-1 header and maybe "can" type headers they use in our top g.F cars. This is difficult, because there is no ready headers, they must be made and tried. Usually 4-1 gives more power, but 4-2-1 more torque. Those cans are used to cure dead spots in middle range.
Intakemanifold/carburettors/injection There should be done some desicions in basics first. We should could calculate how long intakesystem should be compared to exhaust system. Because I have no recourses to do this kind of research, we just choose longer manifold. And ofcourse straighter is better, and we dont need swan neck because of distributor on block. Usually longer give more torque and vice versa. We are planning to use our present PBS straight manifold, its about 85mm long and absolutely straight. Absolute fuel system would be fully programmable injection with slide plate throttle body (quillotin). Other choise for throttle body would be carb type butterfly body. This dont give as much flow as slideplate, but is lot more reliable.
Ignition Optimal ignition would be fully programmable direct spark, so thats what we bought. It will have no distributor at all, only two double coils that we run at wasted spark mode. It will have one trigger on crank pulley, and knock sensors. We are going to use Bosch coil, it has those two double coils in one pack, looks cool, and Bosch igniter also.
Cylinderhead and camshafts My cylinder head will be made by owner of Esatech. He is propably the best Fiat racing engineer in Finland and he has been building these engines for fifteen years or so. He will raise intake ports upper, so it will have lower angle to cylinder head, this will be the best head he have ever made, atleast I hope it will be! He is building it right now, and sayd that it will flow 250-270hp at Superflow 10" bench. Camshafts will be same type as we used earlier, these will have 12,8mm lift though! Retainers will be titanium and custom made for us. They will have adjusting plates on retainer, not on follower. This will save more than 350-450 grams of weight in valve train. New shims will be from Peugeot, they weight only under 1g compared to original which weight 25-30g each. We are also planning to make billet cams, then we could use as high lift as we want to. Ofcourse that will mean also that we will need to modify also cam houses, because any larger than what we use now cannot just be installed, bearing is too small now.
THIS IS WHAT IT WILL BE THEN; Block Croma i.e.block with 131 Racing crank which is lightened several kilos. Wiseco 87mm pistons giving 2140cc. Scat H-profile billet rods with ARP bolts. Flywheel will look like swiss cheese and it will have Sachs MFX aluminum pressure plate. Total Seal piston rings and Clevite bearings, full baffles and new type of draining. Cylinderhead Esatech head flowing 250-270hp. Straight PBS intakemanifold, titaniumretainers, adjusting plates under followers weighting á 1g/each, also Arrow Precision race followers. RR-Exhaust header 4-1, dbilas 45mm throttlebodies and Link+ injection Other stuff Direct ignition, aluminum adjustable cam pulleys, oil cooler with thermostat. If I can find, 1" wide cam belt, normal is 3/4" Moroso oil accumulator will help keeping engine alive. All pulleys will be aluminum with multigroove belt. How much it should produce hp/torque? Im waiting for 210-215hp with 24-25kg/torque, but It COULD have even 230hp or so, I will tell you, thats for sure!
8.1.2004 Now its running, only with 10,4-1 CR, so its not producing what it could. I will raise the CR later at spring. Now it produces 215hp and 24kg. It will produce 10-20hp more after I will raise the CR to 12,5-1 I hope.
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