HAI Experiment

[R.I.D.E.]

The wife ran regular in her Murano, which recommended premium. Not a trace of spark knock in 32 K miles. She averaged 22 MPG cpmbined on regular. Never tried Premium long enough to see if there was an improvement in mileage. EPA highway was 24, I think city was 19 (new ratings). Old ratings were 20 and 25.

Mercedes warned against using regular fuel, and had specific recommendations against using full power if you had to use regular in an emergency. That is a supercharged engine that was designed specifically for Premium.

Cast iron heads retain heat which would normally be dissipated much more rapidly with an aluminum head. Engine knock was a product of poor fuel distribution combined with cast iron induced hot spots as well as poor combustion chamber design.

When oxygen sensors were introduced by Nissan in the 1981 280Z using the early Bosch type flap resistor AF meters, they could raise compression ratios. Later with the introduction of knock sensors fuel quality did not cause engine knock with ignition timing retarded to the point of elimination of knock based on the knock sensor imput.

Bottom line is most modern engines are designed to use regular fuel. My 06 Corolla manual stated clearly that the engine was designed to run properly on regular. Premium provided no benefit as far as economy or performance.

In high performance engines with combustion chambers designed specificially around the combustion characteristics of premium fuel, where the owners manual specifically requires premium (like the Benz), then you should use only premium.

[GasSavers_NovaResource]

Originally Posted by R.I.D.E.

The wife ran regular in her Murano, which recommended premium. Not a trace of spark knock in 32 K miles. She averaged 22 MPG cpmbined on regular. Never tried Premium long enough to see if there was an improvement in mileage. EPA highway was 24, I think city was 19 (new ratings). Old ratings were 20 and 25.

Mercedes warned against using regular fuel, and had specific recommendations against using full power if you had to use regular in an emergency. That is a supercharged engine that was designed specifically for Premium.

Yes, you can run an engine designed for premium on regular fuel but the computer will cut power by retarding the ignition timing. However, loss of power and economy will occur.

Originally Posted by Jetta90GL

I guess a quick test would be to remove the knock sensor from the block to see if the power loss disappears. After all it is basically a microphone listening through the engine block material, if it cant hear, it won't retard timing.

Power loss will not disappear because the engine will be pinging reducing the power.

Originally Posted by Jetta90GL

A non-intercooled turbo engine IS a HAI, and could run with out detonation back before knock sensors where even used.

No, it was a cold air intake but the turbo heated the air. This is why boost on a non-intercooled engine is limited. Intercoolers were added to allow greater boost? Why? Because turbos heated the air and cooler intake was needed to prevent detonation. Again, hot intake air should be avoided. That's why intercoolers were added.

Originally Posted by Jetta90GL

My Turbo Coupe had a switch for regular or premium gasoline. From what I've read the premium setting caused more advanced timing and a few more PSI of boost. Premium fuel is only needed if the engine is tuned for it.

Correct.

Originally Posted by Jetta90GL

If you believe the HAI is causing ping and retarding timing, you could test the HAI detonation theory by using high octane compared to regular octane with the HAI and a comparison with out the HAI.

Higher octane would help but why would you want to spend more money on premium fuel when regular fuel with a normal intake works fine. Higher octane fuel is a band-aid fix for a WAI. Any money you save with higher mileage would be wasted on higher priced premium fuel.

Bottom line: a WAI is not a mileage improver. And it can damage your engine.
Proof:
http://www.metrompg.com/posts/wai-test.htm
http://www.gassavers.org/showthread.php?t=38
http://www.gassavers.org/showthread.php?t=396

[Jetta90GL]

I think your missing it all. The premium is a test, to see if there really is ping with HAI, not a solution. I can't waste my time explaining much more.

[GasSavers_NovaResource]

Originally Posted by Jetta90GL

I think your missing it all. The premium is a test, to see if there really is ping with HAI, not a solution. I can't waste my time explaining much more.

I think you are missing it. The object is to save money. Spending extra for premium fuel is not saving money.