Big Slice of Reality Pie., 2056 D-jet Dyno run Options

[Olympic 914]

Just got back from having the teener run on a Dyno.

Good and not as good as I expected.

Was hoping for at least 100 Hp, didn't make it.

This run was on a Mustang Dyno, allegedly a Dynojet Dyno reads from 12~15% higher.

First the good.

Runs were extremely consistent. the three runs printed pretty much right on top of each other.

Torque was way up there above 95 tq from 3000 to 4500. with no real dips.

HP numbers were very consistent with a nice smooth line from 2000 to over 4500

Now the bad

Max HP was only read at 88 Hp and max torque was 100.

If I add the 12-15% it comes to 100 Hp. But it is what it is.

Build is

2056 D-jet, Heads by HAM RS+, 8.6 comp. Raby 9590 cam, SS HEs with Triad muffler. I Have adjusted the MPS to what seems to run best for this car.

This car runs great and I just wanted to know what it was putting out, Not really planning to try to tune it for more power. Reliability is the key. and I am so far happy with that.

Dyno sheet added (Date/time is wrong, 5/06/21 8:35am)

[GregAmy]

Don't forget that the standard for manufacturer dyno numbers changed in 1972. All the 2Ls prior to 1975 were rated at Gross (the old rating carried over), but Porsche had to go to the new Net rating for the '75 and '76 because of the re-rating for emissions. I believ there was also a compression ratio decrease?

For what we're doing today, Id' suggest stock ratings for the 2Ls should be compared to pre-75 numbers.

[Tom_T]

Don't forget that the standard for manufacturer dyno numbers changed in 1972. All the 2Ls prior to 1975 were rated at Gross (the old rating carried over), but Porsche had to go to the new Net rating for the '75 and '76 because of the re-rating for emissions. I believ there was also a compression ratio decrease?

For what we're doing today, Id' suggest stock ratings for the 2Ls should be compared to pre-75 numbers.

Greg - you're confusing the SAE & DIN gross to net spec switch for 1973 MY, with the 1975 MY GC 2.0L engine switch that was emissions control based. BTW - that gross to net switch was an auto industry wide change.

PS - the other emissions control cause spec shift for the USA was in the 1968 MY when they required the air injection into the exhaust manifolds to control emissions by "after-burning" in the manifold(s)/pipes

No - the change was for the 73 MY, which was why the 1.7L carryover (non-California cars) was slightly lower than 72 1.7L 914/4s - so my comments above about 70-72 1.7L vs 75-76 2.0L performance would also extend to 73 1.7 cars NOT from California with it's lower HP & TQ.

And NO - the 75-76 GC 2.0L is a completely different engine & performance in terms of their emissions control mandated detuning. That is the big difference that you're seeing for the 75 MY specs.

Also - since the change from Gross to Net & DIN to SAE specs was for the 1973 MY when the 2.0L flat-4 was introduced to replace the slow selling 70-72 914-6 - the Gross DIN & SAE specs for a 73-74 GA 2.0L motor is actually much closer to the prior 914-6's 110 HP (detuned from the 1969 911T's 120 HP for same motor), and the TQ would be better on the 73-74 GA 2L-4 motor, than for the -6 (it was already more torquey at lower rpm than the -6).

Granted that the 911 based 2.0L flat-6 has far more upside potential, as show by 64-69 911 models with up to 270 HP IIRC on street tuned versions - but the GA 2.0L /4's are far more streetable than the -6's, because you can get more torque pull at low rpm in 2nd & 3rd gear around town.

That was my butt-dyno impression on the 2 1970 914-6s that I test drove back in 1975 before getting my 73 2L - and neither of the -6's passed my factory 914 trained mechanic Hans' PPI anyway, so non-contenders for my & my budget back then a year out of college!

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Tom
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