AutoblogGreen Q&A: Joel Maguire talks about the GMC Denali XT

Click the Denali XT for a high res gallery

Joel Maguire of General Motors sat down to chat with AutoblogGreen at the Chicago Auto Show following the introduction of the GMC Denali XT concept. The Denali is a four-door unibody pickup truck based on the company's Zeta rear wheel drive platform.

ABG: So, Joel, what is your role at GM?

Joel Maguire: I am the global innovation manager for hybrids. I work in the Advance Engineering Organization in Power Train. I'm not doing current production stuff. I am doing what is next. I work closely with the group that is doing the production stuff. So, I was involved in the Denali XT and had a lot of help from other folks along with some people in Troy who are doing the production stuff.

ABG: When did the Denali XT program start and when did you make the decision to use the type of powertrain that went in there?

Read the answer to this and more questions about why the current hybrids are not flex-fuel capable after the jump.

JM: Well, the base building blocks, I think we had in our hands for some time. You can see them reflected in the Sierra right now. But, in earnest, this got going in the spring time frame of last year , we were trying to scope this out. I think there were some ideas and concepts of what the vehicle would represent and we were contacted by the vehicle integrators. In this case, it was a team at Holden in Australia.

ABG: Are you using the same two-mode transmission that is in the GMT900 [GM's full-size pickup and SUV platform] hybrid?

JM: In this case, it is the same transmission and we are using some other building blocks that are in GM's technology basket. Using small V-8 small-block technology with active fuel management, energy storage based on what we might find in the Tahoe or Sierra. But those were all very carefully rebalanced for this particular vehicle. It has better aerodynamics, better rolling resistance, lower mass. So, we did not need the same type of displacement that you might find in a Sierra. We rebalanced it to make sure that we can take advantage of the active fuel management where only half the cylinders are active.

ABG: One of the things that is obviously unique about the Denali compared to the production applications that have been announced so far is the flex-fuel capability. Can you talk a little bit about why we have not seen that on any of the current production or the already announced hybrid programs?

JM: Well, I guess, the best way I can give you an answer from a gearhead perspective is that I think we are trying to make an initial statement and be all about fuel economy with a no compromises type of a vehicle. I think that is what you see in the Tahoe and the Sierra when they had been introduced. As we reached a little bit further into the future here, with something like the Denali XT, I think we have other things to balance. In this case, certainly one of the technologies that are in our technology basket is E85, and as I was discussing with Scott, he made a point that the E85 has a lower energy content. Because that hurts your volumetric efficiency, if we had rolled out that technology with, let us say the Sierra or the Tahoe, their volumetric fuel economy wouldn't have been as substantial and, frankly, we wanted to make that statement with this first vehicle that we came out with.

As we looked a little bit further on, we could take advantage of some of the inherent efficiencies of the hybrid system, whether it is stop-start characteristics or active fuel management broadening the range that it can operate, or some mild or electric operation. Those types of technologies brought up the base of efficiency. So, you will lose a little bit of fuel economy, volumetric fuel economy due to the E85, but then you gained because of the hybridization so that on the net balance, the customer would enjoy some increased fuel economy for the concept like the Denali XT when it is run on E85.

ABG: This powertrain combination obviously managed to achieve a significantly greater overall improvement efficiency than the production GMT900 hybrids so far, 50 percent overall.

JM: Yes, there was modeling that we did with the crew from GMR and we are showing some numbers in the 50 percent category and it is chiefly because it is more aerodynamic, much lower to the ground, it has active ride height and tire rolling resistance was more optimized. So, a lot of vehicle technologies that fundamentally improve the efficiency characteristic, those type of technologies can leverage with the base engine technology that was able to be brought down in displacement, down to a 4.9L and then, of course, we always have the active fuel management and because we are using the hybrid powertrain, we are able to broaden that range.

ABG: Use the active fuel management more aggressively?

JM: Be much more aggressive because we have the extra electric power to broaden that range and smooth up their operations so that they can be used more effectively in a wider application.

ABG: Aside from the fuel economy concerns with ethanol, are there any other technical challenges that might have precluded, at least so far, using flex-fuel capability with ethanol, for example, blending the electric combustion power and modeling the torque of the engine based on the different fuel.

JM: That is a really good question. Now, part of the answer that comes back is that we are very accurate. We have to have very accurate engine models within the two-mode. We have a very intricate optimization system that is always looking at battery state of charge, engine characteristics, and always looking for the optimum range whether you are on a fixed gear or in an EVT range in the transmission that tries decide where it should be.

There is a very accurate model that exists in there and we would use the same type of model. They will be looking for, realizing that I am using the E85, I am going to have a different type of horsepower and torque characteristic and would be feeding that in. I'm giving you a kind of roundabout answer to say that we would use the same tools that we have got in the base Sierra or Tahoe, we just chose not to implement that in the first implementation. So, I think you'll find that the base tools are exactly the same and were compatible with the E85 type of technology.

ABG: Are we likely to see this powertrain combination showing up in production GM vehicles in the next few years?

JM: I come from the Advanced arena, so I can't speak to that accurately. What I can tell you is that the building blocks that we see in this Sierra are found in the Denali XT. Those building blocks that we are going into production with are the same ones we find in the Denali. And, because of that, I think that it could have production opportunities.

ABG: What sort of mileage you would expect from a vehicle like this? What kind of range would we expect to see?

JM: I think we are trying to be a little bit obtuse about that, because it is a concept vehicle, the press release came out and said that compared to small pick-up truck we are looking at a 50 percent increase in fuel economy and I guess look up webpages and search the small pick up trucks and see what kind of fuel economy those are also getting.

ABG: What are you defining as small pick up trucks that you are using as a comparison? Would that be something like the Colorado and Canyon, or something more like the Holden pick-ups?

JM: Well, I think, we're probably looking at Canyon or its competitors [Note: The current GMC Canyon Crew Cab with a 3.7L five cylinder has an EPA combined rating of 18mpg. Compared to that, a 50 percent bump would put the Denali XT at 27mpg].

ABG: What about the vehicle itself, this four-door unibody pick-up truck configuration. Do you think that is something that we are going to see in the U.S. market? Obviously Australia has had that for a long time. Is that something we will likely to see here in the coming years?

JM: I think the best answer to that is some of the wording that was in the press kit about the probe that GMC is using to try and understand how this would be received. I think if we couple that with the fact that this is a unibody structure and we have some experience with it at Holden and I think there are areas where if it did come and was generally accepted, it is something that we could look at very seriously.

ABG: And, it certainly seems like something that would not be that hard to do if you felt the market was there since you have already federalized the G8 and other applications.

JM: I think that is a very natural conclusion come to.

ABG: Is there anything else you want to add about the Denali?

JM: I think probably one point I would like to leave you with, Sam, to me the base Sierra and the Denali is about balance. When you look at the hybrid, it is hard to separate the efficiencies that are accomplished on the vehicle versus what is going on in the powertrain. I think that the best answer for a lot of these things are that it is all about the very careful balance of internal combustion technologies, hybrid technologies, and vehicle technologies that are integrated together. And I think that is what's making both of these things very satisfying vehicles.

ABG: Well, thank you very much.