Question about H.P. on a 1.9l

[Ray Morley]

1970 11R** 1077 75 x 61 8.2 63@6000 58@4000 1-Solex(2)
11SR** 9.2 67@6000 62@5000 1-Solex(2)
19S 1897 93 x 69.8 9.0 102@5200 115@3100 2-Solex
1971 11S 1077 75 x 61 7.6 56@5800 55@4400 1-Solex(2)
19S 1897 93 x 69.8 7.6 90@5200 111@3400 2-Solex
72-74 19S 1897 93 x 69.8 7.6 90@5200 111@3400 2-Solex

If you refer to the above chart:

1970 19S 102 HP

1971 19S 90 HP

Why does the exact same engine with the same numbers have a 12 HP difference?

[tonykim]

the 1970 engine had higher compession. It also had a different cam but I don't know if that made much of a difference.

[P-M0unt]

Isn't it because of emissions requirements beginning in 1971? I think I read that somewhere . . .

[timemachine]

Opel lowered the compression ratio to 7.6/1 on the 1.9 to conform to U.S. emission standards and to allow the car to run on lower octane fuel without throwing a fit. It's kind of, but not totally, a separate discussion from the lead/no lead transition happening at the same time. European cars did not suffer the same fate, but it's a matter of parts to restore the original spec. (and much more, as the senior contributors on this site have already stated far better than I can.)

[baz]

i think if you search out rallybobs posts on this subject you will find that 90 bhp is very optimistic i think if i remember right he said they gave more like 67 bhp

[GTJIM]

Opel had to keep meeting stricter and stricter emission laws in the USA - especially in California.
To do this the pistons were changed at the beginning of the 1971 Model year - the new pistons had a "D" shaped dish in them to lower compression ratio to under 7.6:1 ... the old ones are flat topped and rated at 9.0:1 (actually nearer to 8.5:1). There was also a new, hydraulic cam introduced about the same time plus a differently curved distributor and re-calibrated Slowex carb ..... no wonder the motors only made 67 HP!

The best thing to do is use flat topped pistons to restore the CR and shoot for a true 9:1 compression ratio. Oh .... and bin the Slowex carb!

[opelwasp]

Originally Posted by GTJIM Slowex carb!

I love it!

[RallyBob]

Originally Posted by Ray Morley 1970 19S 102 HP 1971 19S 90 HP Why does the exact same engine with the same numbers have a 12 HP difference?

Numerous reasons why.

First of all, in 1971 the ever-tightening (US-only) emissions standards meant that the engine specifications changed. Previously, all the 1.9's had flat-top pistons rated at 9:1 compression, solid lifter cams, and an aggressive ignition timing curve with as much as 55-58 degrees total timing when the vacuum advance was figured in. In order to lessen smog, the US versions of the 1.9 had lower compression pistons fitted from 1971 on. These were rated at 7.6:1 compression. The same year, the camshaft was changed from a solid lifter cam to a hydraulic lifter cam, with approximately 9 degrees less exhaust duration, and 4 degrees less intake duration. EGR was also eventually phased in, and by 1975, the 1.9 engines had Bosch L-Jetronic fuel injection. California versions of the 1975 Opels even came fitted with a catalytic converter. By 1975 the total ignition timing was reduced to 30 degrees, again in the interest of reducing emissions.

To make matters more confusing, between 1970 and 1971, the US auto manufacturers changed the way they rated HP numbers in automobiles. So the gross hp rating system was put aside and the newer method of rating them via SAE net HP ratings began.

Then one more wrench in the works was never realized by most people. German cars were rated from the factory in PS, or metric horsepower. It is slightly different than SAE standards. One ps is equal to about .9863 SAE hp.

So how does this affect us? Well, here's what a 1970 Opel CIH engine would be rated at, using the various forms of HP rating systems.

102 hp gross
90 PS
88.76 SAE net

Note that these are all flywheel hp ratings. HP measured at the rear wheels tends to be 14 to 17% lower than the flywheel SAE rating.

In 1971, the engines were rated at 78 hp. Europe never got these low compression smog engines, so there was no rating for them over there. By 1973 the rating had dropped to 75 SAE hp, presumably due to the emergence of the EGR system. In 1975, the rating was raised to 80 SAE net, thanks to the better flowing EFI intake manifold and the 'Sprint' exhaust manifold.

One thing that has always struck me as odd is that the 1971-1973 GT and Manta were rated at the same HP. Very strange considering the Manta has a 1 7/8" exhaust pipe diameter, and the GT has a 1 5/8" pipe diameter!

Bob

[Manta Rallier]

Originally Posted by RallyBob Numerous reasons why. One thing that has always struck me as odd is that the 1971-1973 GT and Manta were rated at the same HP. Very strange considering the Manta has a 1 7/8" exhaust pipe diameter, and the GT has a 1 5/8" pipe diameter! Bob

Possibilities:
a) Both engine checked on the same factory engineering test stand with a standard test stand exhaust
b) It would be bad marketing to show the GT with less HP.

I favor b).....

Regards,
Mark B.

[Tru-Craft]

Originally Posted by RallyBob Previously, all the 1.9's had flat-top pistons rated at 9:1 compression, solid lifter cams, and an aggressive ignition timing curve with as much as 55-58 degrees total timing when the vacuum advance was figured in. Bob

55-58 degrees?
Bob, how could they have that much advance?
My distributor is set to max at 36 degrees!?
Lyle

[RallyBob]

Originally Posted by Tru-Craft 55-58 degrees? Bob, how could they have that much advance? My distributor is set to max at 36 degrees!? Lyle

Remember, the vacuum advance will not be added to the total number at full load and rpms, it's for part-throttle response. That, and when these cars were new you could buy 98 octane leaded fuel from your local gas pumps for 25 cents per gallon.

[GTJIM]

Here we have one gas station that still sells leaded 104 Octane Racing gas - BUT they will only fill the fuel cell on a trailered race car or a trailered Jet Boat. They are situated beside the river and the race track which is there too. Oh! ... and there is no Road Tax on racing gas !!

"Really - that 55 gal. drum IS the fuel tank for the Jet Boat ... and I am paying CASH!"

[Ray Morley]

This topic is very interesting and I was totally unaware of all of the factors that were involved with the emission requirments.

My 70 Rallye Kadett is an original U.S. market car with the 1.9 litre engine. I have been adding lead additive to every tank of gas.

From what I have been reading...........I should continue to do this.......correct?