Difference 3.0 vs. 3.0 Euro

[Jadams1]

Mine was a non O2 sensor setup (built in early 1980)

I'll have to get a mirror to see it.

[1980SC]

Mine was a non O2 sensor setup (built in early 1980)

Yes, we both have non-O2 930/09 engines.

The Bosch # should be clearly visible on a small metal plate attached to the front of the F.D. (the side you see when looking into the engine bay). If that metal plate is gone, then don't worry about it. I don't think the number is stamped anywhere else.

Rob

[mperkins]

Gentlemen,
i may be chiming in a bit late here - but there may some helpful additionals here..

Actually, there are several small but significant differences between the Euro and U.S. 3.0l engines. Starting with
the transmission, 2nd gear is shorter/numerically taller (i.e. better
acceleration) that was used on only the 1978 vintage SC.

The USA 'SCs from 78-79 had 95mm pistons and a
8.5:1 compression ratio and 39 & 34mm intake and exhaust ports. They also had a smog pump in california
along with a restrictive catalyst exhauast.
The CIS system is also less agressive in that the fuel distributor is
smog-friendly (I believe it offers less potential volume) where as the Euro unit is idential to that of the MBZ 450SEL and 911Turbo fuel distributor and can be set to run a little meaner =i.e. rich. The USA cars are inherently lean on the top-end, particularly on post-1980 vintages. Finally, the USA car has not only a less-agressive advance curve in the ignition distributor, but it also has a vacum-retard unit whereas the Euro has only vacum advance.

In 1980 the USA cars received an increase in the compression ratio to 9.3:1 and retained the 95mm pistons. They also introduced a Llamda/Oxygen sensor for the catalytic-converter which enabled Porsche to do away with the smog
pump. However, in the interest of smog compliance and maintaining an acceptable Corporate Average Fuel Economy -as
the required by our Federal Goverernment (or pay bigass penalties) Porsche elected to REDUCE the port size to 35mm intake and 34mm exhaust.
The horsepower was rated the same at 180hp.

The Euro motor enjoyed 98mm pistons with a 9.8:1 compression ratio, more aggressive fuel and ignition distributors,
larger intake runners, and a more aggressive 2nd gear. They were also a tad lighter since they didn't have to
meet the USA safety requirements. Most of the
grey-market imported cars skimped by on paper but did not have the proper safety cross-member bars in
the doors, in addition to the USA's nasty 5mph bumpers.

Otherwise, there is no difference...

Maurice Perkins
1980 SC Coupe

[mikequig]

Maurice,

You put some great info up in your post.
I'm feeling as though the group has put this puzzle together and we will all know the full differences between the 204HP Euro and the USA 3.0. However, you mentioned that The Euro motor enjoyed 98mm pistons at some point in it's life. That would of necessity have increased the displacement and I'm not finding it in BA's chart of the P'car motors. Can you check that out and clarify for us?

Thanks, Mike

[1980SC]

No 98mm pistons. That would result in 3.2L.

[beamonk]

I have a 930/10 motor w/ SSI and tranny in my 76. It doesn't feel as peaky as the 74 2.7 that was in it, but it will fly on top end. It pulls hard to 7k and feels very robust. It's normal cruising speed is 80 mph. It has the large intake runners. I highly recommend it although I would like a 3.6!
John Brasfield

[mperkins]

mikequig and 1980SC,

My mistake. The Euro pistons are the same size as the USA
pistons at 95mm. The difference that makes the euro 9.8:1 is the dome-size of the piston. You are also correct that using 98mm pistons would result in a 3.2 litre displacement.

However, as I may have indicated, that would be preferrable over the the Carrera 3.2 because the increase in diplacement on the Carreras was a result of the +4mm increase in the connecting rod.

So, while a SC has 95mm pistons and 70.4mm rods the Carrera has 95mm pistons and 74.4mm rods - which are just a hair beyond the reliability threshold of the SCs. Many Carreras end up with oval shaped con-rods (crank side). Plus, they also have a smaller-sized wrist-pins, which is also not good.

So, remember "SC" stands for Super Carrera!

best,
Maurice Perkins
1980 SC Coupe

[Tacoma911]

I have a '81 911 ROW with the 930/10 engine that was imported from Germany to the US in about 1986. I understand that the ROW version for '81 had a smog pump (not currently on-board but can be mounted for emission testing inspections) with no O2 sensor/computer. The exhaust system is the common cross over headers into the cat into the 1 in - 1 out muffler.

I have a couple of questions for forum members who were actively involved with early 80's ROW 911's before the cars were gray market imported into the States:

Is this exhaust that I described above the stock ROW exhaust system that was delivered in Europe? Or at the 1986 time of entry into the States, was part of the federalization process to remove the stock ROW exhaust and replace with the corss-over cat system? If it was replaced in 1986, was what the configuration of the ROW exhaust system?

Looking at the exhaust studs now, it appears that its been many years since they have touched - probably either at the 81 manufacture date or the '86 federalization. I've seen worse but these are not in great shape either.

This question may have been covered in previous messages but my archive search did not get me the definative answer I am looking for in regard to the orginal '81 ROW exhaust system.

Thanks

Bill Thompson

[Jadams1]

"I have a couple of questions for forum members who were actively involved with early 80's ROW 911's before the cars were gray market imported into the States:

Is this exhaust that I described above the stock ROW exhaust system that was delivered in Europe? Or at the 1986 time of entry into the States, was part of the federalization process to remove the stock ROW exhaust and replace with the corss-over cat system? If it was replaced in 1986, was what the configuration of the ROW exhaust system? "

I have the exhaust system you described except mine has a pre-muffler and not a CAT. I removed the air pump and associated piping.

[911nut]

[QUOTE]Originally posted by mperkins
The CIS system is also less agressive in that the fuel distributor is smog-friendly (I believe it offers less potential volume) where as the Euro unit is idential to that of the MBZ 450SEL and 911Turbo fuel distributor and can be set to run a little meaner =i.e. rich.

CIS fuel distributors vary according to calibration requirements but I don't think you'd notice the difference if you put a Euro fuel distributor on a U.S. motor, even a Lambda CIS distributor (if the O2 sensor was disconnected and the mixture is set richer).


In 1980 the USA cars received an increase in the compression ratio to 9.3:1 and retained the 95mm pistons. They also introduced a Llamda/Oxygen sensor for the catalytic-converter which enabled Porsche to do away with the smog
pump.

Actually, the lambda sensor allowed the use of a 3-way catalytic converter. The lambda system continously varies the fuel pressure in the fuel distributor which keeps the air/fuel ratio at 14.7/1. A cat won't function properly at any other air/fuel ratio. This air/fuel ratio is good for economy but you get more torque at a 12.5/1 air/fuel ratio.

However, in the interest of smog compliance and maintaining an acceptable Corporate Average Fuel Economy -as
the required by our Federal Goverernment (or pay bigass penalties) Porsche elected to REDUCE the port size to 35mm intake and 34mm exhaust.

Reducing the intake runner diameter increases air velocity at low rpm, which enhances low speed driveability. It has no effect on emissions or economy.

The horsepower was rated the same at 180hp.

Who really knows what the HP figures actually are? Porsche (as well as all manufacturers) are notorious for understating HP figures. I'd be willing to bet that the US motor is more like 190 HP and the Euro motor is 200-210 HP.

[island911]

Originally posted by mikequig
Ok, I have done some research on the 3 engines that I have access to and here are the findings:

. . .

Footnote: The ultimate "cheater motor" would presumably be to marry the biggers port to the large runners and Euro P/C's. The dyno would tell, but then why did Porsche abandon the larger ports after 78-9?

-Mike

Great thread, guys.

As to "why did Porsche abandon the larger ports" I'll bet it was about Mixing!

It is easy to model an engine as an "air-pump" where bigger valves would make for a more efficient air pump.
However, it far too simple to say bigger valves give more performance when it comes to combustion.

Smaller diameter ports -> Higher intake velocities -> better mixing.
=> Porsche found the "sweet spot" between mixing and flow, in ~1979. (for the 3.0)

An engine with better mixing on the intake and compression stroke, will deliver a more uniform and complete power stroke.

If the engine does not have good mixing of air & fuel, it will have more problems of detonation (esp when matched to higher compression pistons) unless higher octane rated fuels are used.
. . .Or you can run them extra rich, or pull back the timing. . .or some other inefficeint solution used back in the "bad ol' days" of constantly fouling sparkplugs.

[island911]

Originally posted by Tacoma911
I have a '81 911 ROW with the 930/10 engine that was imported from Germany to the US . . ..
. . .
Is this exhaust that I described above (cross-over type) the stock ROW exhaust system that was delivered in Europe?

Bill,
FWIW, I have a big Porsche factory poster of a cut-away 1981 euro SC. It calls out the 204 HP, and the cross-over type exhaust and pre-muffler are clearly visible.
I believe the "cross-over / euro pre-muffler" was the only exhaust type used on the 204HP production SC's.

[Jadams1]

Anybody know what beginning engine serial number in 1980 got the higher compression pistons?

My engine serial number is *6300427* and it's a type 930/09

What serial number started the 930/10 engines?

[Tacoma911]

I wish that the 81 ROW engine was one of the motors that Bruce Anderson did dyno tests on with different combinations of the exhaust systems, cams, etc. while maintaining the CIS system and published the curves. But in an Excellance column a while back as part of a discussion about the ID sizing of the SSI exhaust system, I think he stated that he personally hadn't run a SC 3 liter on a dyno with SSI's..
I am sure that the cat vs premuffler costs me a couple of horsepower at least. Sure would be interesting to have some real idea of what SSI's and a aftermarket muffler (Dansk?).
Thanks for the info.

[Johan.s]

I've tried to read up on the difference between between 1981 930/10 9.8:1 pistons and 1978 930/03 8.5:1 pistons but can't find any information if these are interchangeable?

Can I put 930/10 9.8:1 pistons in my 1978 3.0 SC?

I was looking at Wossner pistons and they have different pistons for the 1980-82 3.0 SC 204hp engine compared to other 3.0 SC. Besides different compression ratio for the two pistons sets the only difference seems to be the wrist pin which made me think these might not be interchangeable.

[Flat6pac]

The wrist pin, both are 22 mm.
The pistons are interchangable but measure clearance because the setup on the cams has a mm difference.
Bruce

[Johan.s]

Thanks! Yep, I plan on getting a suitable cam for the setup.