Optimizing Intake Runner Length for a 1.6L 4 Cylinder Engine

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SUMMARY

This discussion focuses on optimizing intake runner length for a 1.6L 4-cylinder engine equipped with four 36mm carburetors. Key insights indicate that shorter intake runners enhance low RPM power, making them ideal for a zippy daily driver rather than a drag racing application. The relationship between runner length and power band is emphasized, with longer runners favoring higher RPM performance. The importance of side draught carburetors is highlighted, as they utilize short intake manifolds to maximize low-end power.

PREREQUISITES
  • Understanding of intake manifold design principles
  • Knowledge of carburetor tuning and performance
  • Familiarity with engine RPM power bands
  • Basic principles of airflow dynamics in automotive engines
NEXT STEPS
  • Research optimal intake runner lengths for various RPM ranges
  • Explore the effects of carburetor size on engine performance
  • Learn about side draught carburetor advantages and applications
  • Investigate tuning techniques for maximizing low-end torque
USEFUL FOR

Automotive engineers, performance tuners, and enthusiasts looking to enhance the drivability and power characteristics of 1.6L 4-cylinder engines with carburetor setups.

heli-mech
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I'm currently adapting a rack of four 36mm carbs to a 1.6L (97.64 ci) 4 cylinder engine. I'm trying to figure out how to calculate the proper intake runner length to use. This is to be a zippy daily driver, not an 1/8th mile drag car. I've found information on "independent Throttle Bodies" length calculations for fuel injected systems, but this involves a plenum and does not seem relevant. Any help would be much appreciated.:smile:
 
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I can't help with any formulae. As a general rule, however, your power band is partially governed by the runner length. Longer means your band is in a higher rpm range.
 
As far as I know the whole secret of side draught carbs are in the fact that they have very short intake manifolds producing power from a very low rpm. range. part of the m3 power is the 6 individual throttle bodies mounted directly on to the engine. Suggest you make the runners as short as possible.
 

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