[IndrojitSircar]

I have a question for all the fiat gurus here - What is the difference between the standard 7 Port cylinder head and the S1 Head ? What are the other differences in the two engines ?

[DHABHAR.BEHRAM]

Dear Mr.Indrojit Sircar - you have at last asked the ultimate question that can be asked on this thread. I think everyone knows that I was the project engineer for the S1 project when it was started in 1989. The name of he engineering document was RDS/90/PP1 (Release Delete Schedule of the year 1990, number 1). The engine was made under consultancy from an Austrian firm for which one car was sent to Austria. The car came back to me in early 1990. Its registration number was MAM9507.

There are a lot of differences between the standard cylinder head and the S1 cylinder head. The intake and exhaust ports have been reconfigured for additional swirl. The casting is different to accommodate the additional material required due to design shift of the kinematic positioning of the valve train operating mechanism. This is because the rocker ratio is reduced and the train is strengthened. You will observe that the rockers of the S1 are different. The valve stem diameter is reduced by 1 mm. The valve train can be used only with the S1 camshaft, which has bigger diameter bushes supporting it in the cylinder block. The cooling system performance is enhanced by repositioning the coolant jackets in the cylinder head. The design protects both Solex and Mikuni carburettors but optimal power is obtained with Mikuni only, due to twin throttle availability. Therefore, the water pump pulley diameter of the S1 engine is different. The intake manifold supports a charge heating port. The exhaust system has been reconfigured to allow the additional swirl to be effective. The cooling system has been upgraded to reduce inertia. The alternator mounting bracket has been redesigned to eliminate the second harmonic frequency vibrations. The flywheel inertia is reworked, therefore the S1 delivers the desired performance parameters only if mated to the NISSAN F4W56A transmission, although the old transmission is protected in the design. The design was processed with positive crankcase ventilation system and evaporative emission control system but were these were not included in the initial lot of cars as they became mandatory only in 1996 when pre Euro1" norms became effective.

There are only 2 locations where all this data is stored, one is RDS/90/PP1, the other is inside my head. I have mentioned only the essential few to you for your information.

I AM A PRODUCT DEVELOPMENT / VEHICLE TEST ENGINEER. I HAVE THE BEST JOB IN THE WORLD. .

Best regards,

Behram Dhabhar

PS - I see many people wasting money trying to "convert" regular engines to S1. It should not be attempted because it cannot be done.

[funkykar]

Originally Posted by DHABHAR.BEHRAM

[b][u]. I think everyone knows that I was the project engineer for the S1 project when it was started in 1989.

I AM A PRODUCT DEVELOPMENT / VEHICLE TEST ENGINEER. I HAVE THE BEST JOB IN THE WORLD. .

Best regards,

Behram Dhabhar

You are the ULTIMATE Fiat Guru for us Sir. Without you providing this information, I wonder how on EARTH we could have got such valuable information.

I am a happy and PROUD S1 owner!!

[IndrojitSircar]

Dear Behram Dhabhar Sir,

Thank you so much for giving me this info. I never knew that you were the product Engineer for the S1. IT was indeed the best job in the world .
Now i would like to know another thing and that is can the exhaust manifold of the standard 7 port engine be changed with a S1 exhaust manifold? We would of course have to change the rest of the exhaust system as well. What are the positives and negatives of this ?

[samsag12]

Dhabhar sir thanks a ton for sharing the priceless information with us. Didn't knew the technical changes made by the company in the S1 model until now. From now on I respect my S1 even more.
@ Funkykar: Karthik bhai do add me to the list of the proud S1 owners.

[DHABHAR.BEHRAM]

Dear Karthik and Samsag - thank you for your wonderful comments. I appreciate.

Dear Mr.Indrojit Sircar - the boundary dimensions of the S1 and the standard cylinder head are the same, so the S1 manifold will physically fit a standard 7 port cylinder head. However, the regular heat shield will not fit, you may modify by local rework. If you have a water jacket heating pot manifold with a Solex installation, please note that its connection stud height is slightly less in S1 so you may have to add a shim otherwise the engine will catch uncontrolled air and not work properly. This was done to control production variability in Z axis. This dimension is very minor, most people do not realise its importance and when the car does not work properly, they do all sorts of nonsesical things and bugger up the engine, so please be careful. You will have to use all S1 parts from the exhaust manifold to pipe packing, upto the tailpipe. The S1 muffler's internal construction is completely different from that of the normal car. The part number of the normal car's muffler was PAB12453. I don't remember the exact part number of the S1 muffler, it will be PAB46XXX. It is very difficult to get the parts these days, especially the manifold and the front pipe. The engine power will increase by around 1 BHP. The torque will be marginally better. The sound will be very sweet, reminding you of the glorious Italian days of yore! It is music to my ears but there are very few people like us to appreciate it.

Best regards,

Behram Dhabhar

[Fiat&Me]

Originally Posted by DHABHAR.BEHRAM

PS - I see many people wasting money trying to "convert" regular engines to S1. It should not be attempted because it cannot be done.

Sea of info on FIAT cars. The most amazing is that "technology retention to minute details in brain for almost 20years+". In fact Read Only Memories (ROMs) also give data retention guarantee upto 20 years. Behram Sirs brain is better than ROM chip.

Sir, without proper technical knowledge about engine I was also thinking to upgrade my 1987 Padmini engine to S1 Engine (thinking changing head and other small parts) for 02 reasons,

1.Being the latest engine from PAL that was delivered till 1999 and therefore spares will be available at least by 2020
2.Good torque-power and FE performance

But your post has opened my eyes and now I'l not do ant R&D on my car. Still I have one doubt in my mind, Can I replace complete engine of my car (without gearbox/transmission) with S1 engine? Is "peti-pack" S1 engine available in Mumbai? If yes what will be the approx. cost?

[adheesh]

Originally Posted by nvkale2

1.Being the latest engine from PAL that was delivered till 1999 and therefore spares will be available at least by 2020

Thats the whole irony ! S1 engine parts are more scarce than normal Padmini engine parts since they were produced for a relatively shorter period of time ranging from 94 till 97. At this point we cannot be assured of parts 10 months down the lane, 10 years sounds like eternity !!

You can change the engine and transmission, plus you will need to change the final drive to 3.9 too in a regular Padmini, however sourcing these is a big question mark.

Regards,
Adheesh Parelkar

[gururaj r]

My Premier Padmini 1992 requires clutch servicing, timing chain (front end) oil seal replacement etc. I request anyone to suggest a good place to leave my car for carrying this out. I reside at Andheri East, Mumbai

[IndrojitSircar]

Originally Posted by DHABHAR.BEHRAM

Dear Mr.Indrojit Sircar - the boundary dimensions of the S1 and the standard cylinder head are the same, so the S1 manifold will physically fit a standard 7 port cylinder head. However, the regular heat shield will not fit, you may modify by local rework. If you have a water jacket heating pot manifold with a Solex installation, please note that its connection stud height is slightly less in S1 so you may have to add a shim otherwise the engine will catch uncontrolled air and not work properly. This was done to control production variability in Z axis. This dimension is very minor, most people do not realise its importance and when the car does not work properly, they do all sorts of nonsesical things and bugger up the engine, so please be careful. You will have to use all S1 parts from the exhaust manifold to pipe packing, upto the tailpipe. The S1 muffler's internal construction is completely different from that of the normal car. The part number of the normal car's muffler was PAB12453. I don't remember the exact part number of the S1 muffler, it will be PAB46XXX. It is very difficult to get the parts these days, especially the manifold and the front pipe. The engine power will increase by around 1 BHP. The torque will be marginally better. The sound will be very sweet, reminding you of the glorious Italian days of yore! It is music to my ears but there are very few people like us to appreciate it.

Best regards,

Behram Dhabhar

Thank you so much for the details once again. Have dropped you a PM and an email. Kindly go through it.

[kavesh55]

Originally Posted by DHABHAR.BEHRAM

[b][u]

There are only 2 locations where all this data is stored, one is RDS/90/PP1, the other is inside my head. I have mentioned only the essential few to you for your information.


PS - I see many people wasting money trying to "convert" regular engines to S1. It should not be attempted because it cannot be done.

Thats why I looked high and low to get a S1 when the resources were available.

[samsag12]

Experts do comment on this. The ignition timing of a Padmini is 10deg BTDC and the ignition timing of a PP S1 is 0deg or TDC. Is the information correct or is there any deviation in the readings.

[adheesh]

Originally Posted by samsag12

Experts do comment on this. The ignition timing of a Padmini is 10deg BTDC and the ignition timing of a PP S1 is 0deg or TDC. Is the information correct or is there any deviation in the readings.

>The static ignition timing of Padmini with Lucas Distributors is 10 degrees BTDC ie. the center mark of the three marks together

>The static ignition timing of Padmini S1 is 7 degrees BTDC

>The static ignition timing of cars with Magneti Marelli distributors according to the company is TDC.

Regards,
Adheesh Parelkar

[samsag12]

Thanks a lot Adheesh for the correct readings. Really appreciate that. I plan to get the timing of my car checked so what tools are needed for this work. Hopefully an old electrician (he worked on our fiats for the past 24 yrs) would be having the said tool. I think i just need to tell him the correct reading. What do you say.

[DHABHAR.BEHRAM]

Dear Adheesh - in your post no 808 above, please add "with vacuum advance connected", otherwise there will be a 2 degree error and power will not come. I think I have given all information on types of pulleys fitted on Padmini / Fiat 1100 cars. Please repost it so that full clarity is obtained.

Best regards,

Behram Dhabhar