Autoblog Q&A: Erich Heuschele from SRT answers why the Caliber SRT-4 is FWD
Posted Nov 29th 2007 5:01PM by Sam Abuelsamid
While the new Dodge Caliber SRT-4 was in the Autoblog Garage, I had a chat with Erich Heushele and Kathy Graham from Chrysler. Erich is the Vehicle Development Supervisor at Chrysler's in-house tuning group and Kathy is a communications rep for the team. We talked about some of the mechanical changes involved in transforming a Caliber into an SRT-4, including why it doesn't have all-wheel-drive.
Autoblog: I just have a few questions about some of the things that your team did on the SRT-4 that differ from the standard Caliber. What sort of suspension and brake changes were made? Also, why is there no all-wheel-drive?
Erich Heuschele: Sure, well I will try to see what I can give you. We dropped the front end 28-mm and the rear 22-mm. We actually have shorter dampers on the car so it has more jounce travel. We didn't just lower the car. We actually got back some of the jounce travel we lost. It has 210-pound per inch springs in the front, 240 in the rear. That's pretty stiff, and on car like the Caliber and the Patriot, they like stiff springs. The base Caliber is more like a 160 pounds per inch and the old SRT-4 Neon was 175 in the front and 125 in the back. We've got 19 by 7 ½ inch cast wheels, 225/45-19 tires. The Goodyear Eagle RS-A or the F1. The RS-A is actually a really kick *** RSA, it's nearly as capable as the F1 tire.
EH: We did extensive tuning on those things. So you are not really giving up much performance with the four-season tire. The brake system is using the 5.7L Charger cop car calipers. It is actually the export 300C 5.7L pads and the cop car brake pads will go on. You could buy those from Mopar. Those are a little more track capable.
And then the rear brake is essentially a Sebring rear disc set up. We've got a unique master cylinder. It's quite large, and we have got pretty damn stiff calipers and I think a pretty good pedal feel out of that thing. I think especially for a slider (floating calipers), I think that is the benchmark brake system.
AB: Yeah the pedal feels a lot firmer than the standard Caliber that I drove before.
EH: Yes, that is totally a different animal. It has got a much bigger master cylinder to push the fluid volume because we've got twin pistons on the front. We have a unique ABS tuning, unique ESP tuning for the vehicle, but suspension wise we maintain the Caliber R/T 24-mm front sway bar. We bump the rear sway bar from a 15 to an 18 mm.
AB: The SRT-4 only has front-wheel drive versus the all-wheel drive that is available on the R/T. What was the reasoning there?
EH: Well, the all-wheel R/T system is really a reactive system that isn't capable of putting anywhere near the torque that we would want to put on the back of the SRT-4. (This statement got a little jumbled in the transcription process.)
So, we would have had to develop a whole new system, which was quite prohibitive and the feeling was that if we had started from scratch with an all-wheel drive performance system in order to compete with the Evo and the WRX STI, we couldn't offer the vehicle at the kind of price point that we wanted to offer.
AB: The R/T all-wheel drive, is that a viscous coupled or electronic clutch?
EH: They have a clutch, but a clutch off the PTU but it doesn't have the torque capacity in the lower gears that we want. And we wanted to be able to run torque capacity especially at time when it is low MU-type system, where okay, if you put a lot of torque to it on the front wheels and it spins up and then we send some torque to back and then as soon as you have traction you're front-wheel drive again. We didn't want to do something like that. We want to run 60 or 70% of the torques to the back tires.
AB: Right, that makes sense.
EH: A real performance system.
AB: You said you did some specific tuning on the stability control for this vehicle for the tires and suspension and the other changes. Were there any other hardware changes that were done on SRT-4?
EH: Let's see. Well, you know we have got a unique full 3-inch exhaust system. I mean if you want to get started in the engine stuff. But, chassis wise we've got, yes, it is definitely a completely unique ABS/ESP tune for the vehicle. And we pushed the limits quite a ways out there compared to a base car. In other words, if you drive through the slalom smoothly, as fast as the car will go, we were 68 ½ mph through the slalom. You will not get ESP intervention.
AB: Yeah, I noticed it seemed to be pretty hard to get it to kick in and I just tried a couple of maneuvers on the road, just a couple of lane change type of maneuvers and it didn't seem to kick in. When I did get it to kick in on a slippery road, it was much smoother than some of the other systems that I have tried on other vehicles recently.
EH: Well, thanks. We do a lot of development work on it and SRTs, I think, generally performance drivers don't like the ESP controlling what they are doing so we try and push it out as far as we can and still catch the car.
Kathy Graham: And that is what I was going to say, Sam, is for that SRT customer, it's a unique customer from the base Caliber. They are looking for different things when they drive the car than the average driver and as Eric said better than I can but that's why we do those things with SRT.
AB: I just have one last question about the engine. You are not using direct fuel injection on there are you?
EH: No, it's not a direct injection. It is multi-port.
AB: Are there any plans in the future if you can talk about it to go to a DI system on there?
EH: We can't talk that. Kathy is shaking her head.
KG: We'd have to kill you Sam!
AB: That's what I figured the answer would be, but I had to ask anyway.
KG: We always are looking at different things. But until we announce something, we cannot talk about it. We look at all technologies all the time and would evaluate it based on what makes sense for the vehicle, for the customer and for the business case.
AB: Sure, I understand that.
AB: Well thanks for answering the other questions.[/align]