Advice for new Atomic 4, gas, owners

[SloopJonB]

Originally Posted by hellosailor

Folks have been taught to think "high test" will make their engines run better. Ignoring the new ones with detonation sensors, that's been fooling the masses for over 50 years.

Using low test to run a high compression engine? Sure, that's one way to do it. Or you can start with building a stronger engine. Many ways to skin that cat. The faster the "boom", the faster the pistons can move, and velocity buys more power than just increasing the mass. That's why aluminum baseball bats hit further than wood.

Two problems with that;

1. Detonation sensors work by dialing back timing advance - that really DOES steal power.

In addition to decades of hot rodding, I am also speaking from very recent experience with my wife's supercharged Jag. Obviously it requires high octane, as specified in the owners manual but it didn't specify an octane. Since 92 is the best available in the States, I figured 91 would be O/K here.

It was demonstrating some less that stellar performance - exactly like too little timing advance - it was "lazy" on hard acceleration. I tried some 94 octane that Chevron sells here and problem solved. The computer was dialing back the timing to compensate for the inadequate octane. So much for "stealing power". I expect the car would barely run on low test.

2. You can't BUILD an engine that can withstand detonation - even diesels don't actually detonate. They are fired by compression heat but the fuel is introduced so it burns, not explodes. You'd need solid pistons and engine blocks to even come close to being strong enough. Ask any race engine builder - they routinely run 14 to 1 and 15 to 1 cr's and have to use 115 octane race gas.

You have to use the octane your engine requires. Most cars require only low test and anything higher is just a waste of money but if the engine needs it you HAVE TO use higher octane gas.

[emoney]

An echo to Sloop's comment above; today's high performance vehicles don't have timing "systems" they have timing "computers". It's a good thing in overall performance, and something such as octane levels in fuel makes a big difference.

As to the age old, "Atomic 4" issue, I've got a diesel now, and quite frankly, while I've had no issues "yet", I'd much prefer to be working on a gasoline motor, as opposed to this one simply because I'm more familiar with them. And having operated or been exposed to gas powered boats or 40 years, it's all about being "smart" when it comes to any of the systems. You can drown, electrocute yourself, impale yourself, explode, catch some form of plague, etc. etc. etc. Not to lessen the need for operating a blower, but it's wisdom that saves more lives than fuel type.

[SloopJonB]

Originally Posted by emoney

As to the age old, "Atomic 4" issue, I've got a diesel now, and quite frankly, while I've had no issues "yet", I'd much prefer to be working on a gasoline motor, as opposed to this one simply because I'm more familiar with them.

It actually goes deeper than familiarity. Shade tree - or should I say dockside? - mechanics are unlikely to have the knowledge, skills and tools to work on high pressure fuel pumps or injectors. They are far too precise to respond to amateur efforts. In contrast, working on an A4 is a lot like the old saying about Chevy's - "All you need is a 9/16ths wrench and a hammer".