Tag Archives: volumetric efficiency. 1 D cycle simulation

Chrysler 426 Hemi in depth dyno test and analysis using modern empirical and simulation techniques

It was on the 23rd of February when four Hemi-powered Mopars swept the Daytona 500 and finished finishing first, second third and fourth. This single event took the racing world by storm and ultimately led NASCAR to impose stricter production rules on Chrysler. But just how much power did those ‘King Kong’ Hemis make by todays standards?To go further we would like to introduce to you the concept of a 1 dimensional fluid dynamics engine performance prediction code. They’re not a new concept and quite a few exist. It’s important NOT to take the dyno figures (even engine dynos) automatically as gospel without question: even methodically calibrated dynos show variance and several OEMs use this to their advantage (notice we didn’t even touch upon the minefield of after market dynos and chassis dynojets). Usually dynos are still very valuable when evaluating changes against an established baseline. The same level of healthy cautiousness should be used when reviewing the simulation data where the results are highly dependent on the assumptions and the code itself employs certain assumptions in its theory. This level of healthy pragmatism combined with an empirical database of what is realistic and what falls outside what is plausible will allow us to really get a good feel and understanding of the engine. We correlate the 1 D code model, fastidiously going over every engine system on a component by component basis. It’s a relatively easy task to get the simulation model to match a fixed set of dyno data. What is more useful is to see if the model can track changes in cam profiles/timing, exhaust system and intake geometry and still predict faithfully. Continue reading

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