October 1998
(with later updates)
I didn't expect the response to the article Power
of a Plus 8 that it has received. It has been fun answering the many
questions and these have made me investigate even deeper and use wider
sources to make the article more accurate since its original publication.
It was also this deeper investigation that spawned the article entitled
Made in the U.S.A. when I tried to reconcile the anomalies of some
of the performance characteristics reported to me of U.S. Plus 8's.
Many of the responses have also noted that to define "power" simply as a horsepower function does not give an accurate idea of the performance of the car. One reader wrote me that "an ocean liner can create thousands of horsepower but still has lousy acceleration". So true!
Many factors go into a full consideration of a car's performance. Suspension, aerodynamics, transmission performance, torque, steering, weight, and the braking system all play important roles along with the raw horsepower. However, some standard is necessary to continue this analysis and after a short straw poll, the power-to-weight ratio seems to be the popular consensus for a power performance yardstick.
The power-to-weight calculation used here is a measurement obtained by dividing the maximum net horsepower of the car by its weight and multiplying by 2000 to obtain the amount of horsepower per ton.
The data used has been sourced from the Morgan Car Company but More often from various auto magazine tests, data form Morgan racers, literature specific to Plus 8's and the research done by Rover V8 experts familiar with Morgan variations. I have found that the figures of the Company are less exact than those of other sources. It is not uncommon in the auto industry to find manufacturer power claims at odds with the dynamometer evidence of other testers. This is most likely a result of the acceptance of Rover figures as verbatim.
On the other hand, differing configurations of the same engine will produce differing outputs and the Morgan configuration of the Rover V8 is more likely to hold more power depending on the exhaust system used for the Plus 8 being examined. For example, a Vitesse engine with cast manifolds and a single exhaust pipe producing 190 bhp, will produce more power with larger bore tubular manifolds and twin exhausts. The ECU of the injection system can be adjusted for the improved airflow up to 25% with the early flapper EFIs and automatically with the later cars up to 11%.
THE PLUS 8N.B. I list only years where a change occurred).
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| 1973-74 | 143 | 1884 | 152.0 |
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155 | 1884 | 164.4 |
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157 | 1884 | 166.7 |
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205 | 1884 | 217.6 |
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192 | 1912 | 200.8 |
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190 | 1956 | 194.7 |
| 1988 | 172 | 1956 | 175.8 |
| 1989 | 164 | 1956 | 167.7 |
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(see note below) |
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| 2000-2004 (UK) | 183 | 2072 | 177.74 |
| 2000-2004 (USA) US Models are heavier |
183 | 2250 (from 3 US dealers) |
162.67 |
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Note On the 4.6 Morgan will regularly create a configuration that lowers the output of the engine and abandons the healthy parametres of the engine. The 4.6 Plus 8s have a hybrid system required when it was found that the 4.6 fueling system "could not fit under a Morgan bonnet", though I doubt that was the true reason as the GEMS fit without a bonnet issue when needed for the USA. For the 4.6, the earlier 3.9 hotwire system was used instead and the 3.9 eprom (chip) with 3.9 fueling solutions was retained rather substituting a chip designed for the significantly greater capacity of the 4.6. This explains the much lower-than-standard LR bhp that the Company indicates for this model. Re-chipping properly releases the true performance of this car and resolves the heating issues caused by the way too thin fueling solutions..which are even too thin for the 3.9s. It is absolutely remarkable the difference between a Morgan stock Hotwire 3.9 and even more so with the 4.6, when a twin exhaust and a proper fuel map is used. Other car data has been sourced from the auto magazines and the manufacturers involved. (I have provided this to give the reader a wider perspective and appreciation of the Plus 8 performance.) |
| N.B. The post 1971 figures do not apply to U.S. models.. See Made in the U.S.A. |
As can be seen, the ratio changes often and significantly. For example, the 1984 injected Plus 8 is a whopping 42.5% more powerful than the least powerful of the breed built from mid 1973 through most of 1976.
The figures for today's Plus 8 do not show the full picture.
Had this Plus 8 remained as light and as "slim" as the original, it's extra
torque would have made it speedier than most of this great line of cars.
However, more cockpit comfort for the more "amply furbished" client, concessions
to structural reinforcement and stylish looking larger wheels have considerably
increased the weight, the girth, the length and the drag of a car that
started off with the aerodynamic competence of a cathedral. This being
said, it is heart warming to see how the models rank even with the best
of today's sport cars.
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Note that on a power-to-weight analysis, ALL models of the Plus 8 comfortably exceed the new wave of roadsters. The 4/4 and Plus 4 also hold their own within this class and are very competitive price wise.
The Plus 8's can also hold their heads up when viewed with the more powerful examples of the main line traditional sports car field with +8s over the years producing anywhere from 71% to 101% of the big Porsche's power.
There will undoubtedly be cries that the wrong crtiteria was used here. I reiterate that its use was an arbitrary though consensus decision.. I have already happily admitted that factors other than power and weight strongly influence a sports car's performance though this measurement is definitively a more effective one than most. Lastly, let's not forget intrinsics. The Morgan Plus 8 comes fully loaded with these...always has.