which engine is best
Senior Member
Joined: 11-19-2010
Posts: 620
From: Springfield, Oregon
Before buying my 2LT with the 2.4, I rented a 1LT with the 2.2. I would classify the 2.2 as 'adequate' while the 2.4 is 'sporty'. I usually put regular grade gas in my HHR, but I do notice a wee bit more oomph when I am able to fill it up with mid-grade or above.
Senior Member
Joined: 01-02-2012
Posts: 334
From: Livermore, CA
Shouldn't be any more oomph. The computer hasn't changed anything
Deceased
Joined: 06-30-2010
Posts: 25,739
From: Kannapolis NC
Yup, more "oomph" with premium is a common misconception perpetuated by the gas companies. What really happens is that when running the "required" octane, the ECM is able to keep the ignition timing advanced to where it should be instead of retarding it to avoid detonation with lower octanes.
You get a perkier feel because the engine is developing its full rated power instead of having the timing backed off when the knock sensor detects detonation. The knock sensor will detect detonation and initiate the corrective logarithms long before you'll ever hear the classic "pinging". If you're hearing detonation in a modern engine, you're doing damage to it.
You get a perkier feel because the engine is developing its full rated power instead of having the timing backed off when the knock sensor detects detonation. The knock sensor will detect detonation and initiate the corrective logarithms long before you'll ever hear the classic "pinging". If you're hearing detonation in a modern engine, you're doing damage to it.
Senior Member
Joined: 11-19-2010
Posts: 620
From: Springfield, Oregon
Yup, more "oomph" with premium is a common misconception perpetuated by the gas companies. What really happens is that when running the "required" octane, the ECM is able to keep the ignition timing advanced to where it should be instead of retarding it to avoid detonation with lower octanes.
You get a perkier feel because the engine is developing its full rated power instead of having the timing backed off when the knock sensor detects detonation. The knock sensor will detect detonation and initiate the corrective logarithms long before you'll ever hear the classic "pinging". If you're hearing detonation in a modern engine, you're doing damage to it.
You get a perkier feel because the engine is developing its full rated power instead of having the timing backed off when the knock sensor detects detonation. The knock sensor will detect detonation and initiate the corrective logarithms long before you'll ever hear the classic "pinging". If you're hearing detonation in a modern engine, you're doing damage to it.
Deceased
Joined: 06-30-2010
Posts: 25,739
From: Kannapolis NC
The 2.4 can compensate for lower octane, and unless you beat the bejingles out of it under load, it'll run fine on Regular or Mid-Grade.
The L-61/LAP/LE8 2.2 has a compression ratio of 10.0:1, while the the LE5/LE9 2.4 has a compression ratio of 10.4:1. So the 2.4 is a slightly higher compression engine.
And yes you are correct, the 2.2 doesn't really gain anything from running a higher octane, except for the different additive packages used in Premium gasoline which may or may not remove deposits from the valves etc.
The L-61/LAP/LE8 2.2 has a compression ratio of 10.0:1, while the the LE5/LE9 2.4 has a compression ratio of 10.4:1. So the 2.4 is a slightly higher compression engine.
And yes you are correct, the 2.2 doesn't really gain anything from running a higher octane, except for the different additive packages used in Premium gasoline which may or may not remove deposits from the valves etc.
Senior Member
Joined: 04-07-2008
Posts: 1,051
From: Wisconsin
Not exactly correct when talking about the 2.4 and other "premium optional" engines. The computer will adjust accordingly for the detected octane. 100% correct for engines that require a specific octane rating (87 for most engines, 91/92 for high performance engines). The notion that an engine rated for 87 octane will perform better with 91/92 octane is a very old myth. More so with computer controlled ignition systems.
You get a perkier feel because the engine is developing its full rated power instead of having the timing backed off when the knock sensor detects detonation. The knock sensor will detect detonation and initiate the corrective logarithms long before you'll ever hear the classic "pinging". If you're hearing detonation in a modern engine, you're doing damage to it.
Exactly. The 2.4 is a "premium optional" engine giving the best performance when running premium, but will run fine with regular, though not at its peak performance and mileage. I personally don't notice much difference at "street" speeds comparing, but a lot of difference at highway speeds during acceleration.
You get a perkier feel because the engine is developing its full rated power instead of having the timing backed off when the knock sensor detects detonation. The knock sensor will detect detonation and initiate the corrective logarithms long before you'll ever hear the classic "pinging". If you're hearing detonation in a modern engine, you're doing damage to it.
Senior Member
Joined: 02-19-2012
Posts: 1,015
From: Northern California
What I am saying is that since the 2.4 has tables for both grades, it is not technically backing timing off, but switching to tables optimized for the gas grade. It works just like a larger model of the 2.2 if you put low grade in it, since it is aiming for that (based on initial AFR readings) and won't need to pull timing from the lower table unless you get really crappy gas.
Deceased
Joined: 06-30-2010
Posts: 25,739
From: Kannapolis NC
An interesting point Breadfan, I'm not really sure if the E-37 ECM and later variations use a set group of tables in regards to ignition timing, or if they use more of a "floating" algorithm to adjust timing based on real time knock sensor feedback.
