Cruze XFS -- Guiltless Performance

[dwightlooi]

This is a Hypothetical Vehicle which combines most of the Cruze Eco's modifications to a revised power train. The goal is to achieve superior fuel economy to the standard LT / LTZ models, while offering improved performance and retaining the automatic transmission (a quintessential feature to most US consumers). From a performance stand point, this is no Cobalt SS. Rather, it is in the same class as an Acura TSX. The XFS -- standing for Xtra Fuel-economy Sport -- is positioned above the LTZ and comes with all the LTZ's amenities at a $1000 premium over the LTZ.

The XFS uses the Cruze ECO as a starting point. Here's what we keep and what we change:-

• Center Head Rest Delete => XFS retain Head Rests
  
• Center Arm Rest Delete => XFS retain Arm Rests
  
• Thinner Sheet Metal
  
• Reduced Weld Seams
  
• Torsion Beam Axle replaces Z-Link Rear Suspension => XFS keeps Z-Link rear
  
• Unequal Length Half-Shafts replaces Balanced Half-shafts => XFS retains Balanced Half-shafts
  
• Automatic front grille shutters
  
• Full underbody tray
  
• Reduced Tow rating
  
• Lightweight 17" Forged Aluminum Wheels
  
• Low Rolling Resistance Tires (Goodyear Assurance Fuelmax; 215/55 HR17) => XFS switches to Goodyear Eagle GT; 215/55 VR17
  
• 6-speed Manual Transmission (3.83 Final Drive) => XFS switches to 6-speed Automatic Transmission (6T40 w/ 2.89 Final Drive)
  
• 1.4L Turbo Engine => XFS switched to 2.0L Miller Cycle Direct Injection Turbo Engine
  

The 2.0L Engine here is basically a Miller Cycle version of the 2.0T in the Regal. Miller Cycle is basically Atkinson Cycle with Forced Induction. Like an Atkinson cycle engine, a Miller Cycle engine closes the intake valves late into the compression stroke such that the first 25~30% of the compression stroke is nullified. This has the effect of reducing the effective displacement and compression by about 25~30%. More importantly, it makes the power stroke longer than the (effective) compression stroke which improves the amount of energy extracted from each drop of fuel burned. Any engine can be made into an Atkinson or Miller Cycle engine by replacing the Intake Camshaft with one which has a significantly extended opening duration. Doing so however, also reduce output by about 25~30%.

Engine Type: Inline-4; Aluminum Block and Heads (LNE)

Valve Train: DOHC-16v w/ Intake and Exhaust VVT

Fuel Injection: Common Rail Direct Gasoline Injection

Bore x Stroke: 86 x 86 mm

Displacement: 1998 cc (Geometric); 1499 cc (Effective)

Compression Ratio: 13.0:1 (Geometric); 9.8:1 (Effective)

Aspiration: Honeywell-Garrett MGT2052D Dual Scroll Turbocharger @ 11.8 psi

Aftercooler: Air-to-Air

Power Output: 200 bhp @ 6000 rpm

Torque Output: 177 lb-ft @ 1900~5900 rpm

Redline / Rev Limit: 6000 rpm / 6350 rpm

Fuel Requirement: 87 Octane Unleaded / E85 Ethanol

Transmission Type: GM Hydramatic 6T40 6-speed Automatic

Final Drive Ratio: 2.89:1

Gear Ratio (Max Speed in Gear)

• 4.58 (34 mph)
  
• 2.96 (53 mph)
  
• 1.91 (82 mph)
  
• 1.45 (108 mph)
  
• 1.00 (157 mph)
  
• 0.75 (211 mph)
  

RPM @ 60 mph: 1800 rpm

RPM @ 80 mph: 2400 rpm

Fuel Economy (EPA): 26 mpg (City) / 40 mpg (Hwy)

0-60 mph (Est): 7.8 sec

Edited February 5, 2011 by dwightlooi

[Z-06]

As usual nice analysis. Will the manual transmission assist in increasing fuel economy in this setup?

[hyperv6]

Now there is a question nobody has asked.

I guess you have not driven on the Fuel Max tires yet. There is little differance in traction to most normal tires but the gain in MPG is similar to the high mileage rocks some uses. I have seen the testing results here in Akron and the are amazing tires.

Edited February 5, 2011 by hyperv6

[PurdueGuy]

performance model with an auto... bah. I could see offering both.

[hyperv6]

•Center Head Rest Delete => XFS retain Head Rests How much does it really weigh and this will make this a 4 passneger car in the eyes of the Gov. So eliminate the belts in the center too.

•Center Arm Rest Delete => XFS retain Arm Rests Again Really how much weight here?

•Thinner Sheet Metal This is insane as the metal is already so thin hail damage in many area is already an issue. You make it thinner the cars will all be dented up in a matter of one year. The only way you can do this is to use one of the new metals they are working on already for lighter but stronger sheetmetal. They are working on cheaperlighter steels now than the present Boron steel.

•Reduced Weld Seams Ok so you want to take strenght away from a already desgined chassis. How will this hurt the car in the long run in rattles and stiffness. Also will it take away the 5 star crash rating?

•Torsion Beam Axle replaces Z-Link Rear Suspension => XFS keeps Z-Link rear This is not an issue as the Eco rear handles really well.

•Unequal Length Half-Shafts replaces Balanced Half-shafts => XFS retains Balanced Half-shafts In a low power application this is fine. I would not want it in anything more than 200 HP.

•Automatic front grille shutters I seen no issue here as long as the repair cost is not crazy.

•Full underbody tray I expect to see more of this on regular cars anyway.

•Reduced Tow rating Not many people tow with little underpowered cars anyway.

•Lightweight 17" Forged Aluminum Wheels Again these will be more and more common on all future cars.

•Low Rolling Resistance Tires (Goodyear Assurance Fuelmax; 215/55 HR17) => XFS switches to Goodyear Eagle GT; 215/55 VR17 The Fuel Max Tires If you have not triesd them are very good tires and not like any other low rolling resistance tire. If anything work with Goodyear on a low Rolling resistance performance Eagle. I think the are already working on one.

•6-speed Manual Transmission (3.83 Final Drive) => XFS switches to 6-speed Automatic Transmission (6T40 w/ 2.89 Final Drive) Ok

•1.4L Turbo Engine => XFS switched to 2.0L Miller Cycle Direct Injection Turbo Engine How much more will this cost GM and will it be used in any other cars?

The future cars will see some of these idea applied anyways. Things like the grill and underpan will be on the regular cars. Why not just add them to the normal cars and improve the MPG on all cars not just one model.

Edited February 5, 2011 by hyperv6

[regfootball]

I wanted to comment on the Fuelmax tires. I drove the Eco and was expecting that I would be slipping and sliding all over (snowy roads) and it did not seem much if at all different than a normal all season for wet traction. If anything having driven an LTZ earlier I actually thought the Fuelmax may have been a little better in the wet.

Normally extremely low resistance tires are terrible in all other facets and are narrow. On the Cruze these tires are wide and beefy and the sidewall is pretty stiff, too. The handling is really good.

I would be curious to know what the replacement cost and treadwear is. Aside from that, not actually driving in torrential rains or deep fluffy snow with them or on black ice my initial impression is to give them an endorsement.

A huge gripe I have on the Eco is the reduced fuel capacity. Aside from the armrest and 3rd headrest. But yeah, on a hypermile car where you want to brag about how far you can go on one tank, it's sort of a kick in the ass to have a smaller fuel tank.

Of course anything over 200 miles outdoes my bladder anyways.

I think if GM gets serious about an Eco type cruze automatic, they will need speed a lot of time refining the gears and such in the current 6 speed or look really hard at a CVT.

I think a lot of what Dwight is trying to do here is get the engine so that they can regear the 6 speed and make it more efficient than it is now. And in the process get more power out of it so its not working like a hamster in a wheel so much. Whatever they can do in this regard I am all for.

[dwightlooi]

•1.4L Turbo Engine => XFS switched to 2.0L Miller Cycle Direct Injection Turbo Engine How much more will this cost GM and will it be used in any other cars?

The future cars will see some of these idea applied anyways. Things like the grill and underpan will be on the regular cars. Why not just add them to the normal cars and improve the MPG on all cars not just one model.

A 2.0 liter engine does not cost more than a 1.4 liter. The only adder here is the aluminum block and the Direct Injection fuel system. How much? Probably about $500 in retail price worth. Remember, the engine is less powerful and more efficient, but no more or less costly than what went into the HHR or Cobalt SS. Such an engine is probably a good "Eco" engine for the Malibu or Regal. It'll perform better than the 2.4L DI engine while also turning in better fuel economy; it's not a rocket ship power plant, but it'll do alright.

[hyperv6]

I wanted to comment on the Fuelmax tires. I drove the Eco and was expecting that I would be slipping and sliding all over (snowy roads) and it did not seem much if at all different than a normal all season for wet traction. If anything having driven an LTZ earlier I actually thought the Fuelmax may have been a little better in the wet.

Normally extremely low resistance tires are terrible in all other facets and are narrow. On the Cruze these tires are wide and beefy and the sidewall is pretty stiff, too. The handling is really good.

I would be curious to know what the replacement cost and treadwear is. Aside from that, not actually driving in torrential rains or deep fluffy snow with them or on black ice my initial impression is to give them an endorsement.

A huge gripe I have on the Eco is the reduced fuel capacity. Aside from the armrest and 3rd headrest. But yeah, on a hypermile car where you want to brag about how far you can go on one tank, it's sort of a kick in the ass to have a smaller fuel tank.

Of course anything over 200 miles outdoes my bladder anyways.

I think if GM gets serious about an Eco type cruze automatic, they will need speed a lot of time refining the gears and such in the current 6 speed or look really hard at a CVT.

I think a lot of what Dwight is trying to do here is get the engine so that they can regear the 6 speed and make it more efficient than it is now. And in the process get more power out of it so its not working like a hamster in a wheel so much. Whatever they can do in this regard I am all for.

The design and compounding of the Fuel Max is amazing. I really is a game changed in the tire market. Goodyear has advanced compounds in the last 6-7 years like no other company. They are still working more into the future with some pretty cool thing yet to come. After some hard times the CEO Keegan invested in new technology and it is really showing in their new model tires.

We even had a chance for a Goodyear promo to put normal tires and the Fuel Max tires on a pair of Soap Box Derby cars. Being involved with the Derby cars rolling resistance is everything. They paired up a local driver vs Nascars Greg Biffle. The local driver with the Fuel Max tires one by several car lenghts. They then did a test on the proving grounds here in Akron to show how well they handled and gripped vs normal tires under different conditions.

They are not the rock hard tires of the past like the Michelin and others have made.

[dwightlooi]

As usual nice analysis. Will the manual transmission assist in increasing fuel economy in this setup?

Not by much. If you turn back the clock to the 1980s, manual cars tend to have somewhat better fuel economy than automatics. That is due to three primary reasons; two of which are no longer valid and the third has been mitigated.

• Manuals had more ratios
  
• Manuals had a wider ratio spread
  
• Torque converter introduces slippage losses
  

Today's 6-speed, 7-speed and 8-speed automatics have equal or more ratios than a manual. Today's automatics also have a wider ratio spread than a manual (6.0 ~ 7.5:1 vs 5.2 ~ 6.0:1). That leaves the torque converter.

The torque converter is a hydraulic pump and turbine coupling. It serves to allow slippage and also provide some degree of torque multiplication. Think of it as two propellers in a tank of water facing each other; one turns and pushes water against the other in turn causing it to turn. This is necessary for the automatic to not stall the engine at idle and enable smooth slam shifting between gears (which is what an automatic does). However, like all pressure based systems a torque converter is only efficient when there is a speed difference between the input and output impellers. At cruise, both are turning at basically the same speed. When you open up the throttle, the input impeller needs to get to a certain speed differential before energy is passed on to the output impeller. Momentarily there is always a "lag" during which energy is wasted. Herein lies the basic reason automatics are less efficient.

However, in today's context, this is also greatly mitigated with the introduction of the converter lock-up clutch. Basically, unless the car is at very low speeds or there is a big amount of power flowing through the transmission, the torque converter is locked up and there is no hydraulic action. This is how an automatic operates at freeway cruising speeds and mild throttle openings meaning there is no converter losses, period. The converter only unlocks when the diver accelerates hard or when creeping around in 1st.

So... of the three sources of automatic inefficiency, two are gone and one is half gone, leaving today's automatics similarly efficient to manuals. The PREDOMINANT reason the Eco is more efficient than the LT/LTZ models is that it has a much taller effective gear ratios (combination of the gear ratios and final drive). This allows the Eco's engine turns at abuot 500 rpms slower than the automatic at 75 mph. This is gives it 42 mpg on the freeway. But the taller final drive also means that the Eco took 9.8 secs to reach 60 mph whereas the automatic only needed 8.9 secs.

If we simply re-gear the 6A to a similarly tall gearing, it'll be around 27/40 mpg -- even without the lightening, special tires and aerodynamic tweaks. But, it'll also take another second to reach 60 mph so its not a free lunch.

Edited February 6, 2011 by dwightlooi

[RjION]

Cruze XFS is a great idea for those that want the option. Having a 180-190hp option is also a great idea.

[NOS2006]

I feel like GM would put too much money and time into this with limited payback. Seems like it's not really that much of an asset given the current variety we've got in the Cruze.

[daves87rs]

I like it...

[loki]

i like it, but i'm guessing only the torque would be different in this motor vs a DI 1.4L pushed alittle more? using the same hp/in^3 as the lnf the 1.4L should have ~180hp if DI is added

in your specs you say the effective displacement for the 2.0L is 1.5L, would this be better than just using a 1.5L? just off the top of my head i'm guessing barely yes, just for rotating mass for torque, but that's only the first thing that came to mind. (other than the not needing a new engine)

[§carlet §wordfish]

The goal seems similar to the Golf GTD, though I think the diesel is what makes it work in that case.

[dwightlooi]

i like it, but i'm guessing only the torque would be different in this motor vs a DI 1.4L pushed alittle more? using the same hp/in^3 as the lnf the 1.4L should have ~180hp if DI is added

in your specs you say the effective displacement for the 2.0L is 1.5L, would this be better than just using a 1.5L? just off the top of my head i'm guessing barely yes, just for rotating mass for torque, but that's only the first thing that came to mind. (other than the not needing a new engine)

The 1.4T will be about ~150 hp / ~162 lb-ft if you go to DI and but keep 87 Octane as the recommended fuel grade.

An Atkinson / Miller with an effective displacment of 1.5 liters is more efficient than a 1.5 liter. 10%, maybe 15% better. That is why cars like the Prius use an Atkinson Cycle engine. The Prius's 1.8 has a geometric compression of 13:1 but an effective compression of 9.5:1 -- that is a geometric displacement of 1.8 liters and an effective displacement of 1.3 liters. This 2ZR-FXE 1.8 liter Atkinson Cycle power plant makes 98hp vs 140hp of the Otto Cycle version of the engine (2ZR-FE).

[hyperv6]

I feel like GM would put too much money and time into this with limited payback. Seems like it's not really that much of an asset given the current variety we've got in the Cruze.

X2

We already have too many models and too many variations of these models. I agree the money spent would do more good on the cars we have vs another limited model.

Lord knows GM is already going to have to apply many of these ideas to present models along with new developing technology that would apply to all cars. I would rather see GM invest in the new grades on modern steels that are going to be stronger, lighter and they hope cheaper than present Boron Steel etc.

Just making it thinner and removing a head rest will not help anyone 5 years from now.

But then again I am look at this big picture wise.