Tall Injectors = Automatic Transmission

[afx]

Was reading in this book last night that tall Hillborn injectors stacks signified the car was running an automatic transmission.  The book didn't explain why - anyone have any insight?

Edited November 8, 2017 by afx

[High octane]

I've heard that also, but forgot what the reasoning is behind it.

[Ace-Garageguy]

Long stacks tend to make more torque at lower RPM. A torque-converter, the first element in most automatic transmissions, multiplies torque, so you don't need as many revs to launch the car. You want to optimize torque lower in the RPM band.

Automatic transmission cars, especially in the days before lotsa custom-tailored high-stall-speed torque-converters (lotta folks call 'em "stall-converters" for some unknown reason) and automatic launch-control black-boxes, could benefit by having more torque at lower RPM.

Manual gearbox cars could be held at engine torque-peak, and launched with the aid of slight clutch slipping. Auto-box cars get held against the trans with the brakes engaged...mash the gas and let off the brakes simultaneously to launch. Subtle but significant difference in technique, and where in the RPM band you needed the torque to peak.

This short video explains why and how a torque-converter multiples torque, and why you can launch at lower RPMs...where you tailor the engine torque-peak with longer injector stacks.

Edited November 8, 2017 by Ace-Garageguy

[Ace-Garageguy]

More on the black-art intricacies of auto boxes and stall-speeds...

http://bankspower.com/techarticles/show/9-Understanding-Torque-Converters

http://www.badasscars.com/index.cfm/page/ptype=product/product_id=78/prd78.htm

Edited November 8, 2017 by Ace-Garageguy

[R. Thorne]

Same reasoning for longer primary and collectors on the exhaust.  Longer for lower rpm torque and shorter for high rpm power.

[High octane]

More on the black-art intricacies of auto boxes and stall-speeds...

http://bankspower.com/techarticles/show/9-Understanding-Torque-Converters

http://www.badasscars.com/index.cfm/page/ptype=product/product_id=78/prd78.htm

Very interesting Bill, and thanks!