Snowman;
Thanks for posting this. It's an interesting analysis and I've got a similar (abiet simplier) program that I sometimes play with (Dyno Shop V2.5.7M). I've found it useful to help to understand the trade-off's of different factors like cam timing and stuff like that. The problem that I have with both the program that I have as well as the results that you got is pretty simple.
It doesn't coorelate with reality.
I don't know about other engine configurations (such as Detroit V8's), but in the case of the 911, the results don't match the output of the physical engines that we have in front of us. Unless you can input the specifics for a 2.2T and get out a very close approximation of the dyno readings of a real T, it doesn't mean much. If my memory of stats is correct, we should be able to run a "T-Test" (no pun intended
) comparing the results and get confirmation of the validity of the model. Just eyeballing the numbers, it's not a terribly good fit.
.................Porsche Published....... Dyno2000V3.08
Torque:...........130@4200 RPM..........181@4500
HP...................125@5800 RPM..........182@7000 RPM
So no matter what the computer says, it's wrong.
Why? A few things jumped out at me, some would suggest that your analysis should over estimate the power and others suggest that you would have underestimated it.
* You've listed induction flow at 800 CFM. Where did this come from?
* You have both runs using the T camshaft. If I put a T camshaft into a real S, I would expect the performance to be at the level of a T, and even a little bit worse at low rev's.
* You've spec'd the valve lift at 0.050 inches (1.27 mm) when Porsche cams are spec'd at .1 mm (0.0039 inches). So I would expect that you have in fact understated the valve lift.
* Looking at your lift quoted (11.43 mm) it looks like you may have adjusted since the quoted lift for the T camshaft is 9.8298 mm (.387 inches).
* The head who's flow you are quoting (30 mm ports) is in fact the head from a 2.4TK which used CIS injection. It is not the head from a 2.2T which used 32 mm intake ports.
At the end of the day, I don't believe that those differences account for the difference in output between your model and realilty.
Quote:
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Say what you will, these are the facts.
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Yes it's a fact that your computer model output those numbers. No, those numbers are not the facts of a 911 engine. For those you need to look at real examples and right now they do not match your model very well. Once you get it to replicate a 2.2T accurately, you should be able to put in the spec's for a 2.0T and still have the results match real engine outputs. If it's good, it will also accurately predict the stock outputs of a 2.0 Normal and a the E's and S's too.
As such I don't believe that Dyno2000 V3.08 is an accurate predictor of a 911's engine performance.