New 2.5T Predictions

[dwightlooi]

This prediction for the Ecotec 2.5T is based on the new 2.5 liter engine announced for the Malibu. This represents a viable direction GM may take with regards to providing V6 equivalent power from a 4-cylinder. The focus is on attaining a power level similar to the high output versions of the 2.0T (LNF), while rendering maximum torque at the lowest possible rpm, maximizing fuel economy and retaining 87 octane compatibility. The solution combines increased compression and displacement with lower boost levels. The new 2.5 liter block is especially suited for this recipe because it has a 88mm bore along with a 96mm bore spacing. The resulting 8mm wall thickness is not particularly suited for high boost applications. On the other hand, the longish 101mm stroke along with increased displacement is ideal for torque production and fuel economy. For additional refinement and durability, the maximum engine speed is limited to 5350 rpm which produces identical piston speeds compared to the 2.0T at its 6350 rpm limit (Approximately 3550 ft/min).

This engine is mated to the 6T70 6-speed automatic. A tall 2.77:1 axle ratio and 6.05:1 ratio spread ensures reduced fuel consumption. The engine's torque rating of 270lb-ft is also particularly well matched to the transmission's 280 lb-ft rating.

Ecotec 2.5T

• 2.5 liter DOHC-16v Inline-4 w/ Intake & Exhaust VVT
  
• Turbocharged and Intercooled; Honeywell-Garrett MGT2052 Turbocharger @ 10.3 psi
  
• 88 mm (bore) x 101 mm (stroke); Bore Centers 96 mm
  
• Displacement 2457 cc; Effective Compression 10.3 : 1
  
• Direct Gasoline Injection
  
• Dual Balance Shafts
  
• 250 bhp @ 5000 rpm
  
• 270 lb-ft @ 1600 ~ 4600 rpm
  
• Redline @ 5000 rpm / Rev limit @ 5350 rpm
  
• 87 Octane Required
  
• Applications: Buick LaCrosse; 2013 Chevrolet Malibu; 2012 Chevrolet Cruze SS; Chevrolet Traverse; 2013 Cadillac ATS 2.5T
  
• Transmission: Hydramatic 6T70 (MH2) -- 6-speed Automatic w/ 2.77:1 axle ratio
  

Gear Ratio Maximum Speed in Gear

• 1st 4.484 (28mph @ 5350 rpm)
  
• 2nd 2.872 (45mph @ 5350 rpm)
  
• 3rd 1.842 (69mph @ 5350 rpm)
  
• 4th 1.414 (90mph @ 5350 rpm)
  
• 5th 1.000 (128mph @ 5350 rpm)
  
• 6th 0.742 (172mph @ 5350 rpm) *
  
• Rev 2.882
  

* Governed to 130 mph

Cruising RPM

• 2020 rpm @ 65 mph
  
• 2486 rpm @ 80 mph
  

Est. Fuel Economy

• 18 mpg (City) / 26 mpg (Hwy) - Traverse
  
• 22 mpg (City) / 32 mpg (Hwy) – Malibu LTZ
  
• 23 mpg (City) / 32 mpg (Hwy) – Cruze SS
  

[hyperv6]

Who's to say that the Turbo will be 2.5?

I think I will wait for the rest of the story from GM.

Edited April 22, 2011 by hyperv6

[ZL-1]

Who's to say that the Turbo will be 2.5?

I think I will wait for the rest of the story from GM.

I think the turbo will remain at 2.0L (or 2.2L max), but I too await the rest of the story from GM.

[ocnblu]

I'd like to see something like this in the Equinox/Terrain as an option.

[hyperv6]

Who's to say that the Turbo will be 2.5?

I think I will wait for the rest of the story from GM.

I think the turbo will remain at 2.0L (or 2.2L max), but I too await the rest of the story from GM.

GM anounced the new changes would be used on a whole family of updated Eco engines. The 2.5 is just one of the basic models they will use. I too expect a smaller engine to be the Turbo model of models.

Here is one engine that was still born a couple years ago but it gives you an idea of what GM was looking to do with the LNF. This was the considered at one point but just never made it to production with the issues at GM.

Note this info is not some proposal I came up with.

It will be interesting to see what direction they will choose.

Edited April 23, 2011 by hyperv6

[ocnblu]

VERY interesting... it was going to go into a Holden Torana and the Pontiac G6!

[G. David Felt]

In all my years being around cars and trucks, I still do not see why we have to sacrifice Torque for HP. There are too many great engines that have both. I do like what I see with the proposed engine info that was posted, but I do not see a 2.5LT happening if they can get the same HP & Torque with a 2.0L since Stupid Europe tax's you on the size of your engine.

[ZL-1]

In all my years being around cars and trucks, I still do not see why we have to sacrifice Torque for HP. There are too many great engines that have both. I do like what I see with the proposed engine info that was posted, but I do not see a 2.5LT happening if they can get the same HP & Torque with a 2.0L since Stupid Europe tax's you on the size of your engine.

Most of the time it has nothing to do with Stupid Europe but with cylinder wall thickness and resistance, i.e. longer term engine durability.

[dwightlooi]

In all my years being around cars and trucks, I still do not see why we have to sacrifice Torque for HP. There are too many great engines that have both. I do like what I see with the proposed engine info that was posted, but I do not see a 2.5LT happening if they can get the same HP & Torque with a 2.0L since Stupid Europe tax's you on the size of your engine.

Most of the time it has nothing to do with Stupid Europe but with cylinder wall thickness and resistance, i.e. longer term engine durability.

Because... a 2.5 running lower boost and higher compression may actually post better MPG numbers than a 2.0 using lower compression and higher boost. This is because thermal efficiency and brake specific fuel consumption gets better when compression ratio gets higher. While cruising on the freeway (or during the EPA highway test cycle) the engine will generally be in a vacuum or some very low boost condition (1~3 psi). The larger displacement engine makes more power off boost than a lower displacement engine, this means that you can put taller gearing on it and still have enough to maintain cruising speed without a downshift -- this further saves fuel by reducing the cruising rpm and the associated frictional losses. Finally, the engine will also be more responsive and linear because it takes less time to get to 10 psi vs 18 psi (which was what the LNF ran), especially when compounded by the larger displacement motor having more exhaust volume with which to run the turbine.