How The Viper Engine Got Its Horsepower

The New Ramchargers: We Talk Viper Engines From 1992 to 2014 and Beyond

Chrysler has always had an odd relationship with its motorsports involvement, never as officially hands-off as GM, nor as “Destroy All Enemies No Matter the Cost” as Ford. Even in the heyday of powerful pentastars, during the development of the 426 Hemi, there was a relatively small number of engineers working on racing projects. Many of the famous Ramchargers spent their own time and money to get cars out to the track for testing and grassroots marketing.

Judging by the Chrysler engineers we met at Summit Motorsports Park during Power Tour 2014, the spirit of the independent Ramcharger is still alive and well. There were several Dodge (sometimes SRT) Vipers on Power Tour, and three of them were straight from Detroit, with current or former Viper engineers behind the wheel. We (well, me for sure, but I think the rest of HRM too) really like the Viper. We like its history of being a big American brute of a car and declaring with a V10 roar that Corvettes are for sissies, and we like its current refinement into a modern muscle car that we’d gladly make our daily driver. Talking about the Viper with some of the men who made it happen was pretty neat, and we sensed some of the same passion and competitiveness that we admire in the original Ramchargers in the current crop. These guys take the Viper personally. They are irritated that Dodge isn’t out in the fray with Camaro and Mustang, and they seem pretty excited about the upcoming Hellcat Challenger. “I wanted to bring the Hellcat down for this,” said Viper Powertrain Engineer, Dick Winkles. “I think we should have had it here.” This last bit was said with just the slightest hint of frustration, as if the powers that be had rejected his suggestion. Winkles did manage to snag a 2014 Viper for the day though, and he made some pretty solid 11-second passes on a track that was a bit slick from dragstrip newbies rolling through the waterboxes on street tires. When he had a chance, we sat down and talked Viper engines. The 2014 V10 is rated at 640 hp. That’s a big number from a smog-legal naturally aspirated production engine, even if it does have two extra cylinders. How did the Viper engineers get from the original 400 horses to more than 600, and what does the future hold for performance engines?

Editor-in-Chief David Kennedy, probably asking for the keys, judging by Winkles’ expression.

Gen 1 ’92-’95

400 hp

460 tq

The Viper engine has been disparagingly called a “truck” motor, due to the V10 configuration which seems at first glance to be similar to that of the Dodge truck line, and the initial prototype being an iron block didn’t help its reputation, but Viper engineers hate to hear that. “It’s an aluminum block based loosely off the small-block Chrysler V8,” says Winkles. “It’s not the truck engine. If you went through it, we shared, like, one part. A bolt or something. It was much more like the A-engine.” Think fuel-injected and fancied up 340.

How did Chrysler develop an aluminum engine? Well, at the time, Chrysler owned Lamborghini, remember that? The big bull was under the ram from 1987 to 1994. Winkles was over in Italy during the initial design of the Viper prototype, working on Lambo V10 engines, so when the decision was made to go with an aluminum 10-cylinder in the Viper, he was put on the engine team. “I came back from Italy and heard, you’re on the Viper now. We had some design help from Lamborghini, to convert iron to aluminum. You can’t just cast the same block. Aluminum requires different strengthening ribs, has different cooling characteristics. Lambo designed the water jackets, they had a lot of experience with multi-cylinder aluminum engines.”

Gen 2 ’96-’02

450 hp

490 tq

The Gen 1 engine was a very solid piece of machinery, perhaps more solid than necessary. The V10 weighed something like 700 pounds. Winkles says the first place they went for more horsepower in the second generation was scraping some metal off that big ol’ motor.

“In Gen 1 we overdesigned everything. It had to be bulletproof. I can’t blame people for thinking it’s the truck engine. It certainly looks like one. The Gen 2 objective was to lose weight. The heads are much more sculptured, I can’t remember exactly, but I think we took 60 or 80 pounds out of the engine.

Our target was 450 hp. We changed cam profiles, it has more aggressive ramps, but no real change to duration and overlap. The main changes were in the exhaust. We had a lot of noise restrictions, and we knew that if we went out the rear of the car, that helps with sound, so no side exits.”

Note: Staff Editor Brandan thinks a Viper with rear exhaust is not a Viper. Just so you know in case you’re planning on buying him one for Christmas.

Winkles with the ’14, Herb Helbig with the ’09, and Greg French with the ’03


Gen 3 ’03-’06

500 hp

525 tq

Bigger is better, so the Viper engine grew a bit in ’03. Something else important happened at the same time. Wanna guess? Well, if you’d always wondered why the Viper wasn’t a Hemi powered machine, it’s because it predates the return of the Hemi engine. In ’03, Dodge introduced the Gen III Hemi, but by then the Viper was pretty well established—and designed around—the decamer of the V10. Despite that, Winkles says the Viper did pull some parts from its new Hemi brethren, and it bumped up the horses to half a thou.

“The desire was 500 horse. We increased the displacement (from 488 to 505 ci) with a larger bore and longer stroke. It shares a common rod and piston design with the Hemi. In ‘04 we went to a powdered-metal rod. We changed the ports. The big difference in the Gen 3 engine was how good the ports were.”

What was it they learned about porting that they hadn’t known in 1992?

“Airflow science evolved. In the early days you couldn’t cast or machine the way you wanted. CNC was so expensive. You were limited by the foundry. We started using CFD (Computational Fluid Dynamics) programs that allow you to optimize the design to reduce losses. The combustion chamber was improved, the runners on the intake manifold were shortened for more rpm. We went back to a side exhaust, which had crossover pipes to tune out sounds and keep back pressure. The downside was heat in the cabin. We called that crossover ‘The ring of fire.’ We were experimenting with active noise cancellation, but the speakers weren’t durable enough at the time.”

Retired Viper Chief Engineer Herb Helbig did the long haul in this ’09 coupe.

Gen 4 ‘08-’10

600 hp

560 tq

The Gen 4 Viper engine is really an impressive use of modern engine technology. “I bought a Gen 4 Viper myself,” Winkles said, and we noticed that several of the other engineers were also rocking the ’08, ’09, and ’10 snakes. It’s always very telling to look at what the factory guys are driving…although, the father of the 426 Hemi, Bill Weertman drove a six-cylinder wagon, so there are always exceptions.

Back to the Viper. The car was in trouble. The emissions rules made it nearly impossible to make horsepower in the old school way, by simply making lobes and cylinders bigger. “CARB came to us and basically said ‘Thou Shalt Not Continue to Build This Car,’ and we didn’t know what to do.” Winkles recalls. “The main problem was OBD requirements, mainly misfire detection readings. With a large overlap cam, that causes difficulty with misfire detection. With a big engine and a lot of cylinders, it’s really hard to detect a misfire, and so the readings were not meeting regulations. We had to reduce dilution in the cylinder at light load, and that’s caused by overlap. If we went to a fixed camshaft that would meet the requirements, we’d lose 100 hp, and we could not have the Viper come out with less horsepower than previous years.

We looked at high energy ignition, reed valves in the manifold, none of that would work. While we were testing we found that exhaust lobe position affected misfire at low speed combustion. Mechadyne had come to us in the past about its cam-in-cam tech. That’s a cam which is a shaft inside a tube so you can independently time either intake or exhaust. It’s not a new idea, it goes back to the ’30s, but Mechadyne had a modern patent. It’s a very complex change, so we hadn’t done anything with it until we ran into the CARB problems.

Originally we wanted to do VVT (Variable Valve Timing) on both intake and exhaust. We had problems with the dual phaser so we decided to go with fixed intake and varied exhaust. Varying the intake might have gained some more low end power, but the Viper isn’t exactly down on torque.

Making it work was a huge undertaking, we were the first production car to use cam-in-cam. Others had VVT with dual overhead cams, but not cam-in-cam. One side benefit was the exhaust note control allowed by the VVT, it cooled the passenger compartment down.”

So was the cam what made the 100-horse jump?

“No, no, that is not what made the extra hp, the big difference, the big bump was cylinder heads, we went to a CNC port. The airflow improvement from Gen 3 to Gen 4 was about 60 of the 100 hp we made. The intake was another bump. We went to 8.4 L (510 ci), and commonized the piston with the Hemi, a cast piston. Cast pistons actually make more hp.”

They do? Why?

“You can make a more complex shape with a cast piston, with a multi-part mold, but a forged piston can be more durable, and has a performance reputation.”

Not a truck engine.

Gen 5 ’12-Present

640 hp

600 tq

Perhaps because of the performance reputation of forging, the Gen 5 Viper went back to a forged piston. No 100-horsepower jumps this time, Winkles says the latest V10 is an exercise in refinement.

“When we went back to a forged piston, we looked at a lot of piston options and they would all be a 20 hp loss or more. We ended up choosing Mahle and only lost 3-4 hp which we made up in other improvements. The intake is now plastic, which is 12 pounds lighter, and has better thermal characteristics. We evened out the intake runners, and got about 12 hp. We picked up 10-12 from a cam change, 5 from a high-flow cat. It’s all little improvements.”

What will we see in the future?

“I feel the Viper engine is at the zenith of a naturally aspirated cam-in-block two-valve engine. There aren’t any large stones unturned. You could make over 800 hp if you didn’t have to pass emissions, but we do. Emissions will force the downsizing of engines, so that will mean more power adders in the future.”

So there you go. The snake trail to 640 hp.

We saw Winkles run an 11.79 on street tires.