What is Wrong With GM’s 3.0L SIDI?
GM's latest V6 was supposed to be about MPG's, it isn't.
August 14, 2009
By: Nick Saporito
Back in December 2008 a lot was going on with General Motors. During that time GM was not prepping for the holidays or basking in new-product glory, they were flying to Washington DC for Congressional Hearings over potential bailout packages. There were few days that you could turn on the news and NOT see General Motors in the headlines. The company was running out of capital and was on the “brink of bankruptcy.” In the midst of all of business drama surrounding GM, they announced an all-new product that looked extremely promising: the 2010 Chevrolet Equinox. So far it has turned out that it really is a stellar crossover and sales correlate with that sentiment. However the Equinox announcement in December also brought another new item: the all-new 3.0L SIDI High-Feature V6.
The entire “High-Feature” V6 lineup of engines at GM started back in October 2002, that is when GM formally announced them. This was GM’s first serious attempt at a global V6 engine family that was to be extremely competitive due to its overhead-cam setup, variable valve timing and numerous other high-tech engine mechanicals. GM’s original press release states that the High-Features can be as small as a 2.8L (which we already have) and can go as large as 4.0L. Obviously the most well-known HFV6 is the 3.6L that has become the mainstream V6 for many, many GM products globally in the past few years.
One can make the argument that the 3.6L HFV6 has been a great engine. For the first few years of its life it was configured with port-injection, but it was overall a solid V6 that was well-respected in the industry. Then 2007 came along and GM nearly reinvented the 3.6L HFV6 by adding direct injection. The good ‘ole 3.6L was now called the 3.6L SIDI. That elevated the power levels to 304 HP, upped the fuel economy a couple of MPG’s and reduced the carbon emissions emitted from it. That engine has spread to numerous applications; mostly replacing the old port injected 3.6L as much as possible.
We then come to the new 3.0L SIDI. As an insider, I have been hearing about this engine for the last three years off and on. To be honest, I was rather excited about its prospects as I knew it was going to come out of the door with direct injection and was supposed to have very decent power ratings. The entire reasoning behind this engine was to boost fuel economy without sacrificing power output. After seeing GM’s wonderful execution of the 3.6L SIDI, it only made sense to assume the 3.0L would be just as marvelous. Apparently I missed a memo somewhere.
I first became suspicious of the 3.0L SIDI when GM blundered on the 2010 Buick LaCrosse fuel economy figures. As of lately they have been good about underestimating fuel economy versus EPA numbers. They were saying 17/27 MPG for the LaCrosse 3.0L. Well, official testing at EPA resulted in the car being rated at 17/26 MPG. Granted, that is one mile-per gallon, but still, it got me thinking. Eventually I brushed it off and thought, “Well it is a heavy car, so maybe it’s just that.”
Not long after that I do some looking into the new LaCrosse just for my own curiosity. Upon looking I discover that the LaCrosse 3.6L SIDI, which has .6-liters more displacement and 25 more horsepower, gets BETTER fuel economy than the ALL-NEW 3.0L SIDI! What?!?! Fast-forward to today and I start digging into every product that currently utilizes the latest High-Feature V6. The more digging I did today, the more confused I became as to what is wrong with this engine? What is its direction or purpose? I’m most certainly not seeing it. Check out the below statistics for why.
2010 LaCrosse CXL FWD
Curb weight: 4,018 lbs.
3.0L SIDI: 255 hp @ 6900 rpm, 217 lb-ft @ 6900 rpm
EPA rating: 17/26 MPG
3.6L SIDI: 280 hp @ 6300 rpm, 259 lb-ft @ 4800 rpm
EPA rating: 17/27 MPG
There are two issues with the LaCrosse. The most-obvious is that the up level, more powerful engine gets BETTER fuel economy than the base 3.0L SIDI. What is the incentive to purchase a 3.0L SIDI here? I would assume that both the 3.0L and 3.6L cost very similar to build. The second issue is that the LaCrosse is a few MPG’s behind its competition from Lexus and Lincoln.
2010 Cadillac CTS Sedan/Wagon RWD
Curb weight: 3,845 lbs. (sedan)
3.0L SIDI: 270 hp @ 7000 rpm, 223 lb-ft @ 5700 rpm
EPA rating: 18/27
3.6L SIDI: 304 hp @ 6400 rpm, 273 lb-ft @ 5200 rpm
EPA rating: 18/27 (note these are NEW, updated ratings for 2010 MY from EPA)
The issue here is yet again quite obvious. The 3.0L and 3.6L both make the same fuel economy numbers. What purpose is the 3.0L SIDI playing in this application? To be fair, the 3.0L SIDI replaced the port injected 3.6L as the base CTS engine. It gained 15 hp and one MPG (for highway) over the old engine.
2010 Cadillac SRX 3.0 FWD
Curb weight: 4,224 lbs.
3.0L SIDI: 265 hp @ 6950 rpm, 223 lb-ft @ 5100 rpm
EPA rating: 18/25
The SRX is the one application of the 3.0L SIDI that seems plausible. The 18/25 figure is very competitive for the segment (matches the Lexus RX, defeats the Lincoln MKX).
2010 Chevrolet Equinox FWD
Curb weight: 3,944 lbs.
3.0L SIDI: 264 hp @ 6950 rpm, 222 lb-ft @ 5100 rpm
EPA rating: 17/25
My main beef with the Equinox application is that it is not competitive in terms of fuel economy. The Toyota Rav4 with the 3.5L gets 19/27 in front-wheel drive form. I also can’t quite understand why the Equinox/Terrain loses a MPG in the city to the SRX when they weigh less and are rated for lower power output.
A reoccurring theme with all of the applications of the all-new 3.0L SIDI V6 is that its big brother, the 3.6L SIDI is much better. The 3.6L obviously has more power, but in most applications it gets the same or better fuel economy than its new sibling. The entire point of the 3.0L (at least, my impression of the point) was to push fuel economy higher. So far it has done that in one application: the 2010 base CTS. Unfortunately another BIG issue with the 3.0L SIDI is that in all applications it does not make its maximum power output until near the redline (or at it), meaning it is a fairly weak mill until the higher revs.
With all of that said, I am seriously asking the question: What is wrong with the 3.0L SIDI V6? Why isn’t it achieving better fuel economy numbers? My guess is that it cannot handle the weight of some of the applications it is currently in, but then why does the CTS 3.6L make the same numbers as its 3.0L? It is the lightest car the 3.0L is currently in. So far I am not impressed with this 3.0L SIDI High-Feature.