Does this mean the car can run regular fuel fine? without any damage later on.......Just curious and I know the question has probably been answered a million times but reading the specifications really confused me.



Specifications
© 2007 General Motors Corporation
PRINTED IN U.S.A. 01/31/08
www.gmpowertrain.com
GM Powertrain
Type: Ecotec 2.4L I4 VVT
Displacement: 146 cid (2393 cc)
Engine Orientation: Longitudinal/Transverse
Compression Ratio: 10.4:1
Valve Configuration: Dual overhead camshafts
Assembly Site: Spring Hill, TN
Valve Lifters: Hydraulic roller finger follower
Firing Order: 1 - 3 - 4 - 2
Bore x Stroke: 88 x 98 mm
Bore Center: 95.48 mm
Bore Area: 243 cm2
Fuel System: Sequential fuel injection
Fuel Type: Regular unleaded
Horsepower:
173 hp (129 kW) @ 5800 rpm (preliminary)
Torque:
167 lb-ft (226 Nm) @ 4500 rpm (preliminary)
Actual power levels may vary depending on OEM calibration
and application.
Fuel Shutoff: OEM defined
Shipping Weight: 273 lb (124 Kg)
Materials:
Block: Cast Aluminum
Cylinder head: Cast Aluminum
Intake manifold: Composite
Exhaust manifold: High Silicon Molybdenum,
Cast Nodular Iron
Main bearing caps: Aluminum Bedplate
Crankshaft: Cast Nodular Iron
Camshaft: Cast Nodular Iron
Connecting rods: Forged Steel


Source:

http://prod.gm.gmgssm.com/experience...400_Marine.pdf

 

premium fuel is recommended, it can run on regular but you may experience knocking.

 

why does it say: Fuel Type: Regular unleaded

and this is directly from GM based on this engine.

 

IIRC, the 2.4L that is used in the Malibu and the G6 is a detuned version of ours so that it can run on regular unleaded (and as such, it doesn't get as much hp), but the Cobalt's 2.4L requires premium fuel or it will detune the engine to prevent knock and provide less power, but you may still get knock at higher RPMs.

 

GM says regular is OK but my 2.4 knocks like a bitch at low rpm/high load if I run regular. It should be pulling back timing to accomodate for the lower octane but you will give up power and efficiency.

92 in the tank, no knock at any rpm / load, bit better mileage to boot - I'll keep running high test thank you very much

 

ur owners manual will say premium is recommended, says right in my book

 

You can use 87 octane. It is recommended to use 91 octane.

What happens is that the car has two timing maps. One is a high octane map and one is a low octane map. If you put 87 octane in the car then when you start the car it will run off the high octane map. Then as the car experiences knock it will pull timing to somewhere in between the high and low octane maps. After a certain amount of knock has occured the car will switch to the low octane map and run off of it until you turn off the car and start it back up again.

Knock is never good. Even a small amount of knock can cause damage over time. That doesn't mean that car is going to all of a sudden blow up because you ran 87 octane in it, but you never know. Not to mention, why pay more money to get the 2.4L motor if you aren't going to spend the extra $4 per fill up to use premium and be able to use the extra HP that you paid for?

 

If your car is just a 2.4l with no modifications, running unleaded is fine. Unless youre tuned and have performance parts like a SC or turbo, there is no need for 93 or 91. But maybe occasionally fill it up with 91.

 

For the extra what $5 per tank?? Is it really worth it not too...

 

Recommended /= required....but I would recommend it also

It's not going to blow up but.....

Exactly

 

What r out pistons made of ?

 

Sure, you can run regular. If you want your motor to sound like **** lol. I tried a tank of 88 i think it was.. I wont be doing that again

 

What does a knock feel like? Is it like a rough idle? ie. shaking during a stop at a red light or what?

 

The bottom line is that yes, the car will run fine on 89 or 87 fuel.

You will probably experience some power loss from knock (ignition) retard.

Your fuel economy will suffer somewhat. How much? Who knows? But the decrease will be more pronounced in hot summer weather, especially if you use the air conditioning.

That said, GM "recommends" 91 octane for the 2.4 engine. Lower octane fuel reduces the tolerance to combustion related problems. If you use 87 octane fuel, and experience a fuel related mechanical problem, you "may" have a greater problem getting GM to cover it under warranty. As I said, , , who knows?

 

I would like to know this too.
Can it be heard?
It is only on ignition or also running???

Thank you,

 

Touche! The truth.

Knock is a commonly used term to describe "preignition". It will sound like a noticeable loud rattle from the engine for a second or so, until the ignition retard kicks in, and eliminates it. (Think of a tin can full of marbles rattling around in it.)

It usually happens when you put the engine under a sudden increased load, i.e. climbing a hill, or pulling out on the highway to pass a slower vehicle. Trust me, when you hear it, you will know it!

This is a very simplified explanation. There are all sorts of other preignition problems, that "do not" have an audible warning. Those kind of problems are very expensive to repair and usually involve replacing pistons and boring/honing the cylinder bores.

 

Recommended but not required

Pretty self-explanatory, IMO.

 

All gasolines are not the same. If you run larger fuel injectors on your 2.4L, you will need to use premium. Honestly, injectors aside. Premium fuel is better any day for even a Go-Kart. I run Shell V-Power religiously. One time I used regular Citgo gas and my car actually bitched at me. Not only that, I'm getting 3 mpg city more than what the EPA says. I once had a pretty sweet Mustang that I always put regular in. I wish I would have used premium in that car in retrospect. The extra few dollars spent on premium in the long run will preserve the life of your engine. I'm just a little above stock on my 2.4L. I haven't upgraded injectors yet. I don't have to run the premium. Run the premium. Chevron is good, too. Once you have gone 100,000 miles, remove your valve cover and you will be surprised at what you see. Your cams, gears, and valves/valve springs will be as shiny as the day it was manufactured. Yank a valve out of there and I will bet that you will have next to zero carbon deposits. Also this goes without saying. Change your oil on time. If your like me, you clean your Cobalt's engine with a Q-tip. 0 sludge-0 carbon = one happy Ecotec.

 

Running larger injectors has nothing to do with having to run premium, it is all about the tune. The only reason for going to larger injectors is if you go SC or turbo, and then you tune for more power using more timing so you need to use higher octane.

The only way you get better gas mileage using premium is if the car is tuned for premium. In the 2.4L you might get slightly better gas mileage because of the increased timing with premium. In a regualr cobalt that is not tuned for premium it will make no difference at all, in fact you can get worse gas mileage because the fuel doesn't burn as efficiently.

 

what excatly is knocking??

 

Yeah it's Wikipedia, but this sums it up nicely:

Knocking (also called knock, detonation, spark knock or pinging) in spark-ignition internal combustion engines occurs when combustion of the air/fuel mixture in the cylinder starts off correctly in response to ignition by the spark plug, but one or more pockets of air/fuel mixture explode outside the envelope of the normal combustion front. The fuel-air charge is meant to be ignited by the spark plug only, and at a precise time in the piston's stroke cycle. The peak of the combustion process no longer occurs at the optimum moment for the four-stroke cycle. The shock wave creates the characteristic metallic "pinging" sound, and cylinder pressure increases dramatically. Effects of engine knocking range from inconsequential to completely destructive.

 

The 2.4 has a knock sensor. I would occasionally run 87 in my 2.4 and NEVER ever had knocking, detonation, whatever you want to call it. Premium is just recommended, not required. To be honest I hardly noticed any power difference when running premium. You will be fine either way. All in all if your really worried put the expensive **** in. its like 2-3 bucks a tank extra.