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Discussion Starter · #122 · (Edited)
Hello members,

So let's recap and try to piece together what Alfa 4 cilinder forced induction competition engines passed in the previous posts. But first a definition:
"Forced induction is the process of delivering compressed air to the intake of an internal combustion engine. A forced induction engine uses a gas compressor to increase the pressure, temperature and density of the air. An engine without forced induction is considered a naturally aspirated engine." Source: Wikipedia.

Types of forced induction:
1. Compressor charging with power taken from the crankshaft
2. Turbo charging with power taken from the exhaust gases
3. Combinations of the two (called "comprex" by Lancia)
Please feel free to add possibilities.

When talking about 4 cilinder forced induction competition engines, there are some options:
ad 1. Compressor charging
A system based on oilpressure driving compressors.
- GTA-SA, 78.0 x 82.0, some claim also 86.0 x 67.5 (approx.12 engines and 10 cars with this competition engine originally built/adapted from 1600 GTA's.)

Besides that there is
ad 2. Turbo charging
A system based on exhaustgas pressure driving a compressor. All Alfetta developments except for the GTAm 2000 Turbo engine. Mentioned were:
  • Autodelta GTAm 2000 Turbo competition engine (it isn't clear if the engine was developed past the prototype stadium)
  • Alfetta Berlina Turbo competition engine. Autodelta project for South Africa. "Also few cars (by the rumors 12 cars) were made for the VIP in Italy. Later AR SA preferred the local development and put on the market limited numbers of Alfetta Turbo designed by Alpine Motors"
  • Schrick Alfetta Turbo competition engines, 81.0 x 69.0, for Heinz Isert's Alfetta GTV Turbo, German DRM (Tony Adriaensens talks about a series of 12 engines/vehicles built)(12 engines built, the same number as the Autodelta SA engine, connection?)
  • Turbodelta Alfetta GTV 2000cc 16v competition engines, 84.5 x88.5 VSharp named
  • Early eighties Alfa Romeo Turbo competition engine
  • Angelini Gruppo 5 GTA Turbo competition engines (Angelini 1100, 1300, 1600cc, 2000cc Turbo engines)
  • Beninca Alfetta GTV Turbo competition engines.
A thread on 6, 8, 12 and other numbers of cilinders with forced induction can be found in the Alfa Romeo History section. The administrator moved the relevant posts from here to that thread.
The posts on the non GTA-SA forced induced engines have been deleted by the administrator.

Ciao, Olaf
 

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Over 800 HP for a 4-cylinder 2000cc engine, it sounds really weird. Powers of 400 HP per liter on turbo engines have only recently been reached and in very few cases (Steph Papadakis with 2500 cc Toyota 2AR) while for series engines (?),
Not weird at all… in the 85-86 F1 season, if you didn’t have over 800hp you didn’t qualify or ended in the back rows

Keep in mind that BMW 1500cc turbo ran over 1000hp in qualifying boost (on special fuel) and also Toyota had 2.1lt turbo 4cyl. GpC that also ran over 800hp for qualifying.
Rosche’s ace in the hole with toluene base nazi “rocket fuel” develops by BASF which stretched rules which mandated 101 octane related street fuel.

detonation resistant , it developed over 1300hp. He said they didn’t know exactly how much power it made since it pegged out the dyno. Perhaps a guesstimation of 1450hp as I vaguely recall him saying.

there were many mythical stories on the bmw M12 turbo based on a production car 2002 engine block. Starting from the high mileage motors poached out of the junk yard for being already rigorously feels tested to later being left outside and urinated improved surface tension! Haha.
 

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Not weird at all… in the 85-86 F1 season, if you didn’t have over 800hp you didn’t qualify or ended in the back rows
It is weird as we were talking about a Nord based engine. I think, by the sounds of it, the only Alfa part left was the crankshaft ...
Pete
 

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Perhaps not the final evolution but did anyone take the time to watch the second video I posted. You can clearly see the engine bay. Greg crick is literally embarrassed having to say the Alfa has more power than his v8. I can understand because the beninca car was rough as guts. How much power, enough to win sports sedan races outright. That’s a lot.
 

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Perhaps not the final evolution but did anyone take the time to watch the second video I posted. You can clearly see the engine bay. Greg crick is literally embarrassed having to say the Alfa has more power than his v8. I can understand because the beninca car was rough as guts. How much power, enough to win sports sedan races outright. That’s a lot.
Just did, and also the testing one. Definitely sounds good.

One thing we have to remember with Sports Sedans, is that the quality of the field varies greatly so you usually only have 2 competing cars with the rest keeping the track from cooling down. I remember watching them when I was a young chap and the only cars I ever watched were the first 2 ... bit like F1. The others blew up or retired for other reasons or were way off the pace
Pete
 

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It is weird as we were talking about a Nord based engine. I think, by the sounds of it, the only Alfa part left was the crankshaft ...
Pete
Yeah point taken. Are there any of these SA motors running in actual cars?

I wonder if these oil driven compressor are still available…we’re they from another application or a bespoke autodelta part? It will be great to built a replica motor with jenvey dcoe efi that looks the part.

i luv the look of this Frankenstein laboratory motor.
 

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Hello members,

So let's recap and try to piece together what Alfa "Nord" forced induction competition engines passed in the previous posts. But first a definition:
"Forced induction is the process of delivering compressed air to the intake of an internal combustion engine. A forced induction engine uses a gas compressor to increase the pressure, temperature and density of the air. An engine without forced induction is considered a naturally aspirated engine." Source: Wikipedia.

Types of forced induction:
1. Compressor charging with power taken from the crankshaft
2. Turbo charging with power taken from the exhaust gases
3. Combinations of the two.
Please feel free to add possibilities.

ad 1. Compressor charging
A system based on oilpressure driving compressors.
- GTA-SA, 78.0 x 82.0, some claim also 86.0 x 67.5 (approx. 10 cars with this competition engine originally built/adapted from 1600 GTA's.)(post #105)

ad 2. Turbo charging
A system based on exhaustgas pressure driving a compressor.
  • Autodelta GTAm 2000 Turbo competition engine (it isn't clear if an actual engine was built)
  • Autodelta? Alfetta Berlina Turbo competition engine (in post #151)
  • Schrick Alfetta Turbo competition engines, 81.0 x 69.0, for Heinz Isert's Alfetta GTV Turbo, German DRM (Tony Adriaensens talks about a series of 12 engines/vehicles built)(post #125)
  • Turbodelta Alfetta GTV 2000cc 16v competition engines, 84.5 x88.5? (post #136)
  • Early eighties Alfa Romeo Turbo competition engine (in post #159)
  • Angelini Gruppo 5 GTA Turbo competition engines (Angelini 1100, 1300, 1600cc, 2000cc Turbo engines, post #136)
  • Turbo Alfa 75/Alfa 155 competition engines
  • Beninca Alfetta GTV Turbo competition engines (post #157)
This list is to be added and corrected with specifics as we go along.

Ciao, Olaf
Any idea what psi or boost the pair compressor are generating or the compression ratio?
 

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Olaf,
Obviously GTAm engine was built and tested. Otherwise how engineers could get the testing reports?

Alfetta Turbo was the Autodelta project for South Africa, also few cars (by the rumors 12 cars) were made for the VIP in Italy. Later AR SA preferred the local development and put on the market limited numbers of Alfetta Turbo designed by Alpine Motors

Also regarding the photo of the Alfetta engine with a volumetric compressor that I posted in this topic. It was a fruit of Autodelta, the picture was made at the AR Museum basement
 

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Here is the GTA SA story:
Alfa Romeo GTA SA
The rarest and least known of all the GTAs was the SA (supercharged) version, presented at the third competition car show in Turin in March 1967 and then re-presented at the Geneva Motor Show that year. The acronym SA was an acronym for Sovra Alimentata, and indicated the presence of the two centrifugal coaxial compressors fixed to the sides of the carburetor group, which fed the two double-body Weber 45 DCOEs, typical of the GTA, by means of a watertight collection box. The car was designed for group 5, which in the permissive interpretation of the FIA rules, left the possibility of massive processing on the production models. This concept, exploited at the time by the English and German tuners, which often changed the lazy family sedans into real racing cars for the tracks, prompted Alfa Romeo to join the GTA (already crowned queen of the European Tourist Challenge Championship), its sister push with forced feeding. The engines with the compressor were already in the DNA of the Casa del Portello, and the memory of Alfetta 158 and 159 indicated the choice of the turbocharged engine to increase power as a natural solution. The paternity of the project at the Experience Center was of the engineer Gianpaolo Garcea, and the lack of enthusiasm with which Carlo Chiti accepted the idea is known, but as a good commander on the battlefield, he set to work to translate it into a useful weapon. In truth, the project was obsolete right from the start, and the idea of dramatically increasing the power of the small aggregate and putting it in a position to compete with Ford or Porsche "monsters" was destined to be short-lived from the start. However, GTA SA passed like a meteor, leaving a long trail of unanswered questions, mysteries, and uncertain data, which are still the object of curiosity for historians and simple enthusiasts. Very little is known about GTA SA, starting from the number of assembled units, the geometry and origin of the engine, its stay on the tracks and its fate after retiring from competitions. The SA represents perhaps the rarest and most mysterious object in the entire history of the Giulia 105 racing cars. Already during the winter of 1966, the "strange" GTA was noticed on the Balocco track, where Dorino Zeccoli was trying to extract the secrets of its wild nature and decipher the oddities of character, which only years later he would describe as "a tragedy, the car on which a driver of today would certainly not have set foot”. Told by Zeccoli, the driver who more than any other knew the secrets of the Alfa Romeo cars, this judgment takes on even greater weight. According to Zeccoli, the GTA SA was an unpredictable car, difficult to drive, delicate and fragile, but also full of charm, and in some situations, it became the winning opponent. GTA SA hid its secrets well and from the outside nothing, not even the initials, betrayed the difference from the other GTAs. Only the well-trained eye could notice the rear wheel studs placed to accommodate the larger Dunlop 65SC-5.50 M. racing tires. Looking for the differences, one could have noticed only a pressure gauge on the dashboard and until the opening of the engine compartment, the appearance of the SA remained unchanged compared to the other racing GTAs. Instead, once the bonnet was raised, the differences jumped out. The already restricted space of the engine compartment of the GTA was drastically reduced with the "additions" to the carburetor side containing complex structure of the compressors and the watertight box that fed the engine of the GTA SA. As already mentioned, the place of the air box of the air intake of the racing GTA was replaced by the watertight box, with at the ends two turbines of FIAT aeronautical origin (cabin blowers) of small diameter (7 cm). Schematically, the operation of the supercharging system followed a simple logic. A piston pump, located on the suction side of the engine, driven by a chain from the engine, sent oil at high pressure (80 kg / cm2) into two coaxial turbines with two centrifugal compressors that rotated at a maximum speed of 95,000 revolutions per minute. The compressors sucked in the air from the outside and sent it compressed into the fuel supply box of the carburetors, forming the mixture that, through the inlet ducts and the intake valves, reached the cylinders, and this air-petrol mixture was not only " aspirated "by the pistons but also compressed by the compressors. This resulted in a significant improvement in volumetric efficiency. With a high number of revolutions, the turbines created a pressure of 0.6-0.7 bar, which pushed the mixture into the mouths of the usual Weber 45 DCOE 14, which in turn put it compressed at 16.8 bar into the combustion chambers, generating a power of 220-240 hp. This tremendous engine thrust in theory had to be available immediately and in a linear way, since the feeding pump was connected directly to the crankshaft to avoid the classic "gap" of the turbines. The jump in power, however, occurred only (and often unpredictably) from around 3000RPM up to 7500 RPM. To remedy the immediate problems, such as the very high temperature of the oil that moved the pump and the danger of detonations, caused by the small inevitable leaks, an additional radiator was installed to cool the oil, with the appropriate creation of a system of water injection in the ducts to the combustion chambers, to avoid possible fires during operation. Nonetheless, the SA proved to be unreliable and prone to catch fire easily. The other flaw was its behavior, which Zeccoli described as "unpredictable power surge, which came suddenly and without warning, making the SA difficult to steer when cornering or in maneuvering situations". Up to 3000 rpm the engine was suffering and below the performance of “normal” GTA, but when switched to supercharging, it proved to be a beast of enormous power, capable of downgrading concurrency cars. At the time, in the absence of the "wastegate" valve, the compressors were difficult to manage, and the SA, otherwise identical to its GTA sister but with a good 70 HP less, was unable to exploit the braking power of the engine, and in any case showed poor stability in sudden braking. What was certainly not lacking, beyond 3000 rpm, was the enormous torque, which pushed the 780 kg of the SA with incredible ease in every gear ratio at lightning-fast accelerations. Another innovative element that appeared on the GTA SA was the transistor ignition, the true progenitor of future systems, which since 1968 replaced the classic Marelli S119 distributor. But the real Achilles' heel remained the easy overheating in conditions of medium and low speeds. Excessive heat dissipated better at higher speeds, aided by a good cooling system, but in circuits at low speeds and not very high rpm, engine overheating was the order of the day. Another problem consisted in the frightening consumption of petrol, which reached 32 liters per 100 kilometers in running regime, and penalized the SA in long races, forcing it to stop frequently for refueling. The torque that the SA developed sometimes caused easy rear slippage even in longer gears, and the more frequent use of the brakes in endurance races (given the poor performance of the engine braking effect), exposed the entire braking system to fading. But the real mystery in which the history of the Giulia GTA SA remains shrouded begins with its technical content, never completely revealed (or the data have been lost), so much so that over time two schools of thought have developed, which see the SA with different eyes. The majority of Italian authors, describing the engine of the SA, cite the bore and stroke values as 86x67.5 mm, consonant with the search for a super square engine, which perfectly corresponded to the research of a brilliant engineer such as Chiti was undoubtedly. Given the period of development of the SA engine which coincides with the absence of the 1300 engine, with which the SA would theoretically share the stroke of the piston, the crankshaft, the bearings, the connecting rods, and other mechanical components, some seek in the experimental engine developed for the F2 (86x68.5 mm), the base from which all the specific mechanical components have been transplanted. The cylinder head could only be the classic "double ignition", slightly adapted to the purpose; otherwise, the bulk of the changes concerned the base, where the oil pump that powered the compressors was housed. The shortened stroke and the larger bore were the logical way to reduce the speed of the stressed piston, and many are inclined to believe that this was the solution adopted, given that even the specialized magazines of the time highlighted this innovative technical side. But given that the compression ratio was significantly lowered (8.5: 1) and that it was not possible to adopt the classic pistons of the GTA, this opens the bore chapter, which really contains several unknowns. On an engine destined to run continuously even for the entire time of long race events, thinning the shell of the barrels to a thickness much lower than usual, with subsequent weakening of the housing of the same (significantly enlarged holes) meant exposing the base (the whole thruster) to a critical weakening, absolutely not able to perform the task of duration under a regime of high stress. Since they all agree that in the case of the GTA SA engines, only the separate barrels were always used, and that the single barrel (perhaps more robust and rigid) only appeared on the GT Am, the presence of detailed descriptions and many Precise data cited for an unlikely solution certainly remains a mystery. Perhaps, we must take into consideration the presence of two different variants of the same engine, already at the time. In favor of this thesis, the different origin (Portello and Settimo Milanese, with respective markings) of the various surviving engines can also be found. However, it seems that all the engines recently examined (and here we are at the second school of thought) are based on the classic geometry of the GTA, i.e. 78x82 mm, and this data speaks in favor of those who have long argued that the engine block was the traditional 10532.01.010.99 processed for GTA. Given the presence of the same values on the classic racing GTA, it is to be assumed that particular pistons were adopted, considering the lowering of the compression, which only approached the declared 10.5: 1 with the boost factor. In this case, things were simpler, and the use of the 10532.01.053.99 cylinder head, the sodium-cooled valves, and the rest of the GTA kit was logical and easy. The mystery of the number of engines assembled, however, has never been solved. No one can say with absolute certainty how many engines and how many cars have been assembled in the SA version. Opinions are fairly in agreement on the hypothesis that no more than twelve engines were produced for competitive use, while for the number of cars the estimate does not exceed ten GTAs in SA setup. Data that can be found regarding certain chassis numbers list the following cars, present in races between 1967 and 1970: AR 613015, AR 613016, AR 613056, AR 613069, AR 613470, AR 613929, AR 613919. Later 1969, almost all the GTA SAs were converted to the classic aspirated 1600 or 1300 version, with atmospheric pressure carburetors and the last certain appearance of a GTA SA dates back to March 8, 1970, when the GTA SA (AR 613069) driven by Christine Beckers finished second overall in the uphill race in Condroz. Shortly thereafter it was converted to an experimental version with the 1300 engine, but this changes little. GTA SA was already in the legend ...
Great insight here! Thanks for posting

found the answers to my earlier question…

Great stuff
 

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Pete I agree with the quality of the field comments but fact is this car raced in fields of considerable quality over many years. Best thing some of it is on video for all of us Alfaholics to see.
 

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Discussion Starter · #133 · (Edited)
Olaf,
Obviously GTAm engine was built and tested. Otherwise how engineers could get the testing reports?

Alfetta Turbo was the Autodelta project for South Africa, also few cars (by the rumors 12 cars) were made for the VIP in Italy. Later AR SA preferred the local development and put on the market limited numbers of Alfetta Turbo designed by Alpine Motors

Also regarding the photo of the Alfetta engine with a volumetric compressor that I posted in this topic. It was a fruit of Autodelta, the picture was made at the AR Museum basement
Hi Max,

GTAm text corrected in the recap in post #161
Alfetta Turbo text corrected idem
Volumetric compressor. Question; was this done on an Alfa Romeo 4 cilinder competition engine?

Ciao! Olaf
 

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Discussion Starter · #134 · (Edited)
Yeah point taken. Are there any of these SA motors running in actual cars?

I wonder if these oil driven compressor are still available…we’re they from another application or a bespoke autodelta part? It will be great to built a replica motor with jenvey dcoe efi that looks the part.

i luv the look of this Frankenstein laboratory motor.
Hello davbert & members,

It came to my attention that at least one of the people here on alfabb is actively building an original GTA-SA engine at this moment. I suspect he is reading this thread.

He has an original oilpump and has difficulties finding out the dimensions of the pipes and hoses on the oilpump to the other components. And wants to know dimensions of several mechanisms/clips around the oilpump. He would like to talk about the GTA-SA with the owner of the "Dutch" GTA-SA engine I shot at Spettacolo Sportivo and shown here in this thread.

This would be my invitation to him to share his progress here and ask his questions himself. I made a mention of this thread through messenger to him. I can imagine his hesitation (for me(us?) being critical) but he contacted me nonetheless. It could also give him valuable information or even parts to finish his project.
It would be a learning lesson on GTA-SA for most of us.
And it would make this thread even more interesting and factual.

Ciao, Olaf
 

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Hello davbert & members,

It came to my attention that at least one of the people here on alfabb is actively building an original GTA-SA engine at this moment. I suspect he is reading this thread.

He has an original oilpump and has difficulties finding out the dimensions of the pipes and hoses on the oilpump to the other components. And wants to know dimensions of several mechanisms/clips around the oilpump. He would like to talk about the GTA-SA with the owner of the "Dutch" GTA-SA engine I shot at Spettacolo Sportivo and shown here in this thread.

This would be my invitation to him to share his progress here and ask his questions himself. I made a mention of this thread through messenger to him. I can imagine his hesitation (for me(us?) being critical) but he contacted me nonetheless. It could also give him valuable information or even parts to finish his project.
It would be a learning lesson on GTA-SA for most of us.
And it would make this thread even more interesting and factual.

Ciao, Olaf
Nobody in the world knows Alfa Romeo GTA SA engine better than Loris Paone (son of the Autodelta technician), who owned three SA engines, and made a detailed restoration of each of them. Then for the questions of technical problems he is a true magician with encyclopedic knowledge (also applies to the GTA). He is a helpful and kind person and can be contacted at the address: [email protected]. The full address is: Turbo Motor of Paone Loris 10, Via Quarto - 20811 Cesano Maderno (MB), Tel. +39 333 5794953 You need to know Italian to speak with him.
 

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Discussion Starter · #136 · (Edited)
In regard to the bore/stroke dimensions of the GTASA, most likely was the traditional 78x82. Even the picture in Fusi's book of what is presumably an official factory photo, shows the distance above the water pump to the head as that of the normal dimension, as Alleggerita pointed out in a previous post. The larger mono-bore/shorter stroke version has no height distance in this area and is easily identified from the front.
Here is the GTA SA story:
Alfa Romeo GTA SA
The rarest and least known of all the GTAs was the SA (supercharged) version, presented at the third competition car show in Turin in March 1967 and then re-presented at the Geneva Motor Show that year. The acronym SA was an acronym for Sovra Alimentata, and indicated the presence of the two centrifugal coaxial compressors fixed to the sides of the carburetor group, which fed the two double-body Weber 45 DCOEs, typical of the GTA, by means of a watertight collection box. The car was designed for group 5, which in the permissive interpretation of the FIA rules, left the possibility of massive processing on the production models. This concept, exploited at the time by the English and German tuners, which often changed the lazy family sedans into real racing cars for the tracks, prompted Alfa Romeo to join the GTA (already crowned queen of the European Tourist Challenge Championship), its sister push with forced feeding. The engines with the compressor were already in the DNA of the Casa del Portello, and the memory of Alfetta 158 and 159 indicated the choice of the turbocharged engine to increase power as a natural solution. The paternity of the project at the Experience Center was of the engineer Gianpaolo Garcea, and the lack of enthusiasm with which Carlo Chiti accepted the idea is known, but as a good commander on the battlefield, he set to work to translate it into a useful weapon. In truth, the project was obsolete right from the start, and the idea of dramatically increasing the power of the small aggregate and putting it in a position to compete with Ford or Porsche "monsters" was destined to be short-lived from the start. However, GTA SA passed like a meteor, leaving a long trail of unanswered questions, mysteries, and uncertain data, which are still the object of curiosity for historians and simple enthusiasts. Very little is known about GTA SA, starting from the number of assembled units, the geometry and origin of the engine, its stay on the tracks and its fate after retiring from competitions. The SA represents perhaps the rarest and most mysterious object in the entire history of the Giulia 105 racing cars. Already during the winter of 1966, the "strange" GTA was noticed on the Balocco track, where Dorino Zeccoli was trying to extract the secrets of its wild nature and decipher the oddities of character, which only years later he would describe as "a tragedy, the car on which a driver of today would certainly not have set foot”. Told by Zeccoli, the driver who more than any other knew the secrets of the Alfa Romeo cars, this judgment takes on even greater weight. According to Zeccoli, the GTA SA was an unpredictable car, difficult to drive, delicate and fragile, but also full of charm, and in some situations, it became the winning opponent. GTA SA hid its secrets well and from the outside nothing, not even the initials, betrayed the difference from the other GTAs. Only the well-trained eye could notice the rear wheel studs placed to accommodate the larger Dunlop 65SC-5.50 M. racing tires. Looking for the differences, one could have noticed only a pressure gauge on the dashboard and until the opening of the engine compartment, the appearance of the SA remained unchanged compared to the other racing GTAs. Instead, once the bonnet was raised, the differences jumped out. The already restricted space of the engine compartment of the GTA was drastically reduced with the "additions" to the carburetor side containing complex structure of the compressors and the watertight box that fed the engine of the GTA SA. As already mentioned, the place of the air box of the air intake of the racing GTA was replaced by the watertight box, with at the ends two turbines of FIAT aeronautical origin (cabin blowers) of small diameter (7 cm). Schematically, the operation of the supercharging system followed a simple logic. A piston pump, located on the suction side of the engine, driven by a chain from the engine, sent oil at high pressure (80 kg / cm2) into two coaxial turbines with two centrifugal compressors that rotated at a maximum speed of 95,000 revolutions per minute. The compressors sucked in the air from the outside and sent it compressed into the fuel supply box of the carburetors, forming the mixture that, through the inlet ducts and the intake valves, reached the cylinders, and this air-petrol mixture was not only " aspirated "by the pistons but also compressed by the compressors. This resulted in a significant improvement in volumetric efficiency. With a high number of revolutions, the turbines created a pressure of 0.6-0.7 bar, which pushed the mixture into the mouths of the usual Weber 45 DCOE 14, which in turn put it compressed at 16.8 bar into the combustion chambers, generating a power of 220-240 hp. This tremendous engine thrust in theory had to be available immediately and in a linear way, since the feeding pump was connected directly to the crankshaft to avoid the classic "gap" of the turbines. The jump in power, however, occurred only (and often unpredictably) from around 3000RPM up to 7500 RPM. To remedy the immediate problems, such as the very high temperature of the oil that moved the pump and the danger of detonations, caused by the small inevitable leaks, an additional radiator was installed to cool the oil, with the appropriate creation of a system of water injection in the ducts to the combustion chambers, to avoid possible fires during operation. Nonetheless, the SA proved to be unreliable and prone to catch fire easily. The other flaw was its behavior, which Zeccoli described as "unpredictable power surge, which came suddenly and without warning, making the SA difficult to steer when cornering or in maneuvering situations". Up to 3000 rpm the engine was suffering and below the performance of “normal” GTA, but when switched to supercharging, it proved to be a beast of enormous power, capable of downgrading concurrency cars. At the time, in the absence of the "wastegate" valve, the compressors were difficult to manage, and the SA, otherwise identical to its GTA sister but with a good 70 HP less, was unable to exploit the braking power of the engine, and in any case showed poor stability in sudden braking. What was certainly not lacking, beyond 3000 rpm, was the enormous torque, which pushed the 780 kg of the SA with incredible ease in every gear ratio at lightning-fast accelerations. Another innovative element that appeared on the GTA SA was the transistor ignition, the true progenitor of future systems, which since 1968 replaced the classic Marelli S119 distributor. But the real Achilles' heel remained the easy overheating in conditions of medium and low speeds. Excessive heat dissipated better at higher speeds, aided by a good cooling system, but in circuits at low speeds and not very high rpm, engine overheating was the order of the day. Another problem consisted in the frightening consumption of petrol, which reached 32 liters per 100 kilometers in running regime, and penalized the SA in long races, forcing it to stop frequently for refueling. The torque that the SA developed sometimes caused easy rear slippage even in longer gears, and the more frequent use of the brakes in endurance races (given the poor performance of the engine braking effect), exposed the entire braking system to fading. But the real mystery in which the history of the Giulia GTA SA remains shrouded begins with its technical content, never completely revealed (or the data have been lost), so much so that over time two schools of thought have developed, which see the SA with different eyes. The majority of Italian authors, describing the engine of the SA, cite the bore and stroke values as 86x67.5 mm, consonant with the search for a super square engine, which perfectly corresponded to the research of a brilliant engineer such as Chiti was undoubtedly. Given the period of development of the SA engine which coincides with the absence of the 1300 engine, with which the SA would theoretically share the stroke of the piston, the crankshaft, the bearings, the connecting rods, and other mechanical components, some seek in the experimental engine developed for the F2 (86x68.5 mm), the base from which all the specific mechanical components have been transplanted. The cylinder head could only be the classic "double ignition", slightly adapted to the purpose; otherwise, the bulk of the changes concerned the base, where the oil pump that powered the compressors was housed. The shortened stroke and the larger bore were the logical way to reduce the speed of the stressed piston, and many are inclined to believe that this was the solution adopted, given that even the specialized magazines of the time highlighted this innovative technical side. But given that the compression ratio was significantly lowered (8.5: 1) and that it was not possible to adopt the classic pistons of the GTA, this opens the bore chapter, which really contains several unknowns. On an engine destined to run continuously even for the entire time of long race events, thinning the shell of the barrels to a thickness much lower than usual, with subsequent weakening of the housing of the same (significantly enlarged holes) meant exposing the base (the whole thruster) to a critical weakening, absolutely not able to perform the task of duration under a regime of high stress. Since they all agree that in the case of the GTA SA engines, only the separate barrels were always used, and that the single barrel (perhaps more robust and rigid) only appeared on the GT Am, the presence of detailed descriptions and many Precise data cited for an unlikely solution certainly remains a mystery. Perhaps, we must take into consideration the presence of two different variants of the same engine, already at the time. In favor of this thesis, the different origin (Portello and Settimo Milanese, with respective markings) of the various surviving engines can also be found. However, it seems that all the engines recently examined (and here we are at the second school of thought) are based on the classic geometry of the GTA, i.e. 78x82 mm, and this data speaks in favor of those who have long argued that the engine block was the traditional 10532.01.010.99 processed for GTA. Given the presence of the same values on the classic racing GTA, it is to be assumed that particular pistons were adopted, considering the lowering of the compression, which only approached the declared 10.5: 1 with the boost factor. In this case, things were simpler, and the use of the 10532.01.053.99 cylinder head, the sodium-cooled valves, and the rest of the GTA kit was logical and easy. The mystery of the number of engines assembled, however, has never been solved. No one can say with absolute certainty how many engines and how many cars have been assembled in the SA version. Opinions are fairly in agreement on the hypothesis that no more than twelve engines were produced for competitive use, while for the number of cars the estimate does not exceed ten GTAs in SA setup. Data that can be found regarding certain chassis numbers list the following cars, present in races between 1967 and 1970: AR 613015, AR 613016, AR 613056, AR 613069, AR 613470, AR 613929, AR 613919. Later 1969, almost all the GTA SAs were converted to the classic aspirated 1600 or 1300 version, with atmospheric pressure carburetors and the last certain appearance of a GTA SA dates back to March 8, 1970, when the GTA SA (AR 613069) driven by Christine Beckers finished second overall in the uphill race in Condroz. Shortly thereafter it was converted to an experimental version with the 1300 engine, but this changes little. GTA SA was already in the legend ...
These two posts and further, paint a picture of the rare GTA-SA engine, how it came about, what were issues, how it was developed and why it was abandoned. The idea of a short stroke version with 86.0 x 67.5 mm instead of the 78.0 x 82.0 is interesting but proof of such engines in photo's is lacking. And technically, a shortstroke would weaken the integrity of the engineblock, if I read correctly?

Ciao, Olaf
 

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Also I have some doubts that the turbines of GTA-SA were sourced from the airplane as I have a copy (sorry for the small resolution) of AR drawing of the turbine. The date on the drawing is 26.10.1964
View attachment 1695413
In the aeronautical department of Alfa Romeo (Avia) in Pomigliano d'Arco it was perfectly possible to design and produce the turbo unit necessary for the needs of GTA SA, and it would then be the most logical way, given the certain rivalry with the Turin manufacturer (suffice is to remember with what "enthusiasm" Fiat observed the collaboration of Carlo Abarth with the Alfa Romeo company). Your document is an important indication in this sense. However, on the other hand, newspapers of the time and even Zeccoli in his interview with Tabucchi, spoke explicitly of the FIAT origin of the supercharging unit. Some magazines even identified the turbines as “cabin blowers” taken from the FIAT G91Y. What you posted puts (at least in my case) a little doubt on those statements. I was able to see the blueprint of the turbine in question but there was no indicated origin (or I didn't do the case). In any case, a precious piece to compose the GTA SA mosaic.
 

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Moving posts now
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