Battery instantly dead

[billt460]

I am not sure the compression has changed much since we are still using 87 octane gas. But with EFI and electronic ignition the engine starts with minimal cranking.

Compression is much higher now. My 2018 Toyota Camry with the 2.5 L 4-cylinder is rated at 13 : 1 Compression Ratio. My 2015 5.7 HEMI V-8 is rated at 10.5 : 1. Both can be safely run on 87 Octane Regular.

In the early 70's I believe they mandated a maximum compression of only 8.5 : 1. The difference is today the engines can detune themselves by reducing the timing electronically by computer, to adjust for lower octane fuel. Back in the 70's they couldn't. Use the wrong fuel and the engine would knock like hell, or else detonate, and knock holes in your pistons. That happened with a lot of High performance V-8's back then.

Today the Skyactive engine achieves the world's highest compression ratio for a regular gasoline mass production automobile engine of 14.0 : 1.

Also the Toyota AKS 4-Cylinder is a Atkinson Cycle Engine, that has the ability to hold the intake valve open as the piston rises on the compression stroke. Thereby lowering the compression when the engine is at low RPM, and under a severe load.

highest compression ratio for 1971 car engines - Google Search

www.google.com

 

[Donald]

Compression is much higher now. My 2018 Toyota Camry with the 2.5 L 4-cylinder is rated at 13 : 1 Compression Ratio. My 2015 5.7 HEMI V-8 is rated at 10.5 : 1. Both can be safely run on 87 Octane Regular.

In the early 70's I believe they mandated a maximum compression of only 8.5 : 1. The difference is today the engines can detune themselves by reducing the timing electronically by computer, to adjust for lower octane fuel. Back in the 70's they couldn't. Use the wrong fuel and the engine would knock like hell, or else detonate, and knock holes in your pistons. That happened with a lot of High performance V-8's back then.

Today the Skyactive engine achieves the world's highest compression ratio for a regular gasoline mass production automobile engine of 14.0 : 1.

Also the Toyota AKS 4-Cylinder is a Atkinson Cycle Engine, that has the ability to hold the intake valve open as the piston rises on the compression stroke. Thereby lowering the compression when the engine is at low RPM, and under a severe load.

highest compression ratio for 1971 car engines - Google Search

www.google.com

I am old enough to have owned two 1960s Mustangs and there was no mandating of compression ratio. The 1965 Mustang had around 9:1 and I rebuilt the engine with pop-up pistons that raised it to around 10:1.

Obviously if you ran 87 octane in a high compression engine it would knock so then either switch to premium gas or adjust the timing.

 

[billt460]

I am old enough to have owned two 1960s Mustangs and there was no mandating of compression ratio.

In the 60's no. There was no such mandate. Compression was only limited by the ability of the leaded Premium fuel back then to resist knock. The mandate started in the 1971 model year by GM. (Read the link I provided).

 

[pcoxe]

Side terminal batteries are subject to sudden death due to the lead strap from the side terminal to the top of the battery breaking internally. I had that happen on a battery with both top and side terminals. I connected the ground terminal to the unused top post with a short adapter and got several more years out of the battery.

 

[eljefino]

Mercedes tends to monitor the voltage. You used to be able to display the voltage on the dash through some sequence. You usually get some warning when the voltage drops below 11 volts and it says convenience items disabled like the radio.

I hypothesize my Silverado monitors voltage while cranking. If it gives a slow crank after being parked all week it runs a higher voltage, like 15.1 or so, to play catch-up.

As to OPs question, absolutely. My dad's Fairmont went eight years on its (very good) OE Motorcraft battery then went kaput. Gear reduction starters only need around 125 amps to work, so if you have a 650 CCA battery you can be down a lot (and on a steep part of the dying-curve) before you know.

 

[atikovi]

Modern starter motors also draw more power.

Have you seen a modern starter motor? Some are no bigger than a wiper motor.

 

[billt460]

Have you seen a modern starter motor? Some are no bigger than a wiper motor.

They still can draw between 250 and 350 amps at startup. The actual motors can be more compact, because they have gear reduction systems built into them.

 

[andyd]

My '16 Camry came with an Interstate that died 2yrs ago. Went to start in the morning, nothing. Jumped it, ran my errands. Guessed I 'd left something on. Next day same thing. Bought a new size 24 MAXX. Wife's '16 still has original Yuasa? Probably should replace it just 'cuz.