Cosworth get used to XF boost reduction.

Bruce Wood, director of Cosworth's CART Champ Car program, was on hand for the opening of CART Spring Preview testing at Mazda Raceway at Laguna Seca on Saturday. Wood discussed changes made to the Ford-Cosworth XF over the winter as the turbocharged powerplant heads into its third and final season.

Q:
So, what are the modifications you've had to make to the cosworth XF for its final season of CART racing?

Bruce Wood:
Of the three major areas that we focused on this off-season, combustion was the main area we looked at. When the engine was first designed, it was designed for 40 inches of boost - about 10 above atmospheric. So, this season, we're down to 34 inches ...and we've lost about 60 percent of that boost pressure. That's an enormous amount. The design of the combustion chamber ... the profiles and the volumes ... were very much designed around the boost, so therefore, there's quite a difference between 34 and 40 inches of boost. When we made the change from 40 to 37 inches of boost for last year, we chose to live with the compromise in terms of the combustion chamber shape. However, this year it would have been too big a compromise, so we ended up doing a lot of work there.

We also did a lot of work on engine speed. That's one of the things last year where we felt in our qualifying performance on the road courses was not where we wanted it to be. We ended up qualifying very well on the speedways, but not so well on the road courses. Engine speed can play a big part on the road course, especially if you can run the engine fast enough that you can miss out a gear shift. Although gear shifts these days are still very, very fast, they still do take a finite amount of time. If you can miss out a gear shift, there's something to be gained there. In the slowest corners, if you have a higher maximum rev, then the engine won't run so slowly in the slowest corners. It's very difficult to make the engine run very slowly and pick up very cleanly, so the less revs you can drop in a corner, the better. So, we felt we wanted to bring our revs up to improve our qualifying performances. With the new qualifying rules (two additional points available, announced by CART today), it will be especially important to improve our qualifying situation. We looked at the revs for qualifying, specifically about 500 rpms, and in race trim we've looked at about 200 rpm.

The third area we looked at quite a bit was in the area of breathing. We looked at the port profiles and the cam profiles in particular, and we managed to get some performance out of that. So those are the three major areas we concentrated on.

Q:
Can you describe the horsepower you've lost due to the boost reduction?

BW:
The first step, from 40 to 37, was probably worth 75 horsepower, and the next step (from 37 to 34) was probably another 65 horsepower. Of that, we've clawed back with some gains. At the end of last season, we clawed back about 50 of that. This season, we've only clawed back maybe 15 of the 65, and I'd hope there's probably another 10 to 15 more we'll get back before the end of the season. I'd say we'll be lucky to get back half of what we lost this year, but you get to the point of diminishing returns.

Q:
Is there one specific area you want to work on this year during the season?

BW:
We're actually going to concentrate on the smaller things, if you like. In the past, we've always had another season's engine to be looking at, so if we wanted to make some big architectural changes ... in the past changes the angle, or the bore sizes, etc., etc. Those were major investments in both of time and money. So, in past years we've had to pay attention to those things because they do take time and money, and we're started looking at them early in the season. This year, knowing it's the last year for this engine ... a turbocharged engine ... we don't have that distraction, so we can start going back and looking at things that have slipped through the net, so to speak ... simple things like oil testing. In past years, we've found horsepower through working with oils, but we haven't really looked at those things as much because we've had bigger fish to fry. Now, this year, we're going to turn to the smaller things, the detail things. Now, we're going to look at a bunch of things that will bring us four or five horsepower, where in the past, we've been looking only at things that can bring us 10 or more horsepower.

Q:
With the turbo area going away after 2002, does that change honda's and toyota's approach as well?

BW:
I think it will, actually. We all know that at the end of the year, the engines will be done, come what may. So, they don't need to look to the future with these engines, either. Toyota will definitely be focusing on their 3.5 liter motor, so that may re-direct some of their resources, possibly at the expense of their CART engine. Honda, I guess, won't have that program to worry about so I'd expect they'll put 100 percent behind their CART program. So, we're all in the same boat, save for Toyota, who has to be working on their 3.5.

Q:
What do you see as the strengths and weaknesses of the ford-cosworth xf heading into its final season?

BW:
Strengths start with the fact that it's always been a powerful engine ... and hopefully will remain the most powerful. Fuel economy was a real strength last year, but that will be less of an issue this year. But reliability is the key thing. (NOTE: XF failure rate during races last year was four percent, lowest of the three manufacturers) If I actually had to pick any one thing over all the others, it would be reliability. If your engine is 50 less horsepower than anyone else's, but it always finishes, that's probably better than having 50 extra horsepower and failing even once in a season. Reliability is an enormous issue for us, and the last few years we've focused on it very strongly. So, even though we've put the engine speed up this winter, we do it very cautiously. We say it may be 200 extra revs in race trim, but until we come to the first race we may decide to come back a bit on that, just for the reliability point of view. So far, we've had a lot of success with the engines we've run in testing, but we'd like to get more miles on this spec of engine before we get to Mexico. Weakness, according to others, has been our driveability. But, it's kind of like Italian cars ...people say they always rust, and they did 20 years ago, but then they fixed that problem 19 years ago. The public has a very long memory. There's no question we had an issue with driveability if you go back to 1998, 1998, or even maybe 2000. But over the winter going into 2001 we made a big step forward by working with Kenny (Brack) and Max (Papis) when they were at Team Rahal, and we came a long, long way there. So, our driveability made a big jump forward at that point, and with less boost, it's become even less of an issue. People may think we're down to the other two, but I don't think there's much there, and our runs here this weekend so far make it appear that there's not much there.

Q:
From an engineering standpoint, are you sad to see the turbo era end, and what are the challenges of the new rules cart will announce?

BW:
I think the challenges are very similar between the turbo and a normally-aspirated motor, to be honest. I guess the challenge is always to make the most power, with the best economy, and the best driveability, no matter what the package is. It's a shame to see the turbo go, because we believe over the years we've developed the best boost control of anybody's. We put an enormous amount of work into that, so it's a shame to see that disappear. CART's going to have a normally-aspirated, rev-limited engine next year, and much has been made of the fact that that's less technically challenging. But I guess I firmly believe, and we've said all along, that the technical challenge, and the cost, is completely driven by the level of competition. If it's just one manufacturer involved next year, it won't be very technically challenging. But if there's two manufacturers, or three, or four, or five ... and they all want to win ...it will be just as technically challenging to make that engine work. If everyone is out there, we'll all engineer it just to edge of failure, just the way it is now, and that's the thing that makes it interesting for an engineer. It's a challenge to engineer something to the edge of failure, so that it will do its job, but no more. So, the fact that it's normally-aspirated, and rev-limited, doesn't make it less of a challenge, if there's competition.