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Exclusive interview: Alain Raposo
ETi caught up with the Renault-Nissan Alliance director of engineering, to discuss Infiniti’s groundbreaking new Variable Compression-Turbo engine
Variable compression technology was thought impossible until now. How does it feel to have cracked it?
To be the first is a proud moment. I don’t know if all other OEMs will follow but I think there’s a good future for this technology. Variable compression technology has been a dream for the last 80 years for the entire powertrain community because it’s the best way to achieve the right efficiency and high performance. Until now engine technology has been such that we’ve always had to move between efficiency and power. Now, with infiniti’s Variable Compression-Turbo (VC-T), we can have both.
How long has it taken you to develop VC-T?
Roughly 10 years for research, 2-3 years for advanced engineering, and 3-4 years for the actual project. So, more or less, 20 years.
What drove you to keep chipping away at VC-T for so long when so many other OEMs discarded it in favor of developing alternative powertrain technologies?
CAFE was a major driver. Fuel economy constraints are becoming more and more stringent around the world – even in countries such as Brazil. No one could have expected Brazil to implement this kind of regulation, even 10 years ago. And with other countries such as Mexico also introducing similar constraints, it left us wondering how much money we could put into an engine when the cost of every 1 gram of CO2 is increasing. This VCT engine can replace a V6 naturally aspirated 3.5-liter engine. It offers the same performance and similar fuel economy (27%), weight reduction, etc… This kind of improvement is very difficult to do from one generation to the next. But it’s now necessary in order to comply with CAFE.
Will you license this technology out to other OEMs?
Well, I’ve not yet spoken to the management board about this, so this is just what I think: We should at least enjoy the benefits of this technology first. So, we’ll maybe keep this in-house for the first 1-2 years. That’s the usual way for any new technology developed by an OEM. But after that? Sure, it could be open for license. Why not?
Why opt specifically for the 8:1 to 14:1 compression ratio?
It’s common sense, really. If you look at sporty engines such as those by AMG the compression rate is 8:1. With highly efficient engines its between 13:1 and 14:1. So, having a range of 8:1 to 14:1 means we get the best of both worlds.
What was the hardest development challenge to overcome?
Tuning was probably the most complex area. With one engine you might have a compression rate of 10:1 or 12:1 and one map. But with VC-T, and the variable 8:1 to 14:1 range, you have plenty of tuning possibilities, meaning you’re effectively mapping 10 engines.
With VC-T being so pioneering, were you even able to benchmark it?
No, there was no benchmark for this kind of engine. However, we were at least able to compare it against the most efficient engines within the same power range and the highest power engines. Normally, we don’t compete with AMG engines because it’s really a sport engine, but with VC-T we did look at that.
Is VC-T the savior of the IC engine?
I think that by 2020 80% of production engines will be powered by conventional IC technology. Not only that but IC engines will continue to improve. VC-T is just one example of what can be expected from future IC engine technology. The future is bright, but we should be mindful of electrification because it can support even better IC engine efficiency. I don’t think VC-T will remove electrification from the picture completely, either.
November 9, 2016
9 November 2016