Turn-One chose GM High-Tech...
Turn-One chose GM High-Tech Performance to debut its new LT1 pump pulley. To this writer's knowledge, Turn One has the only aftermarket pulley for the LT1's stock accessory drive. The 6061 aluminum, CNC-machined, and hard-anodized pulley is a sweet looking part. On the scale it weighed a 1/2-pound less than the stock steel part.
For most people, the first time they pay any attention to the power-steering pump is when it either boils over or starts making a horrible howling noise, and this is often during the middle of an autocross or open-track day. LS1 powered F-bodies are notorious for burning up pumps. GM recognized this problem and started installing an oil-to-water power-steering cooler on the '98 SS and WS6 F-bodies, and also providing it as an option on all LS1-powered F-bodies. By 2000, the cooler was standard equipment on all LS1 F-bodies. While the cooler is a reasonable fix for most street and mild track use, it only treats the symptom.
Sports cars are almost never driven to their potential. Most people want the image without any of the sacrifices of a race car. Because of this, most will never experience the precise steering that is possible when pump volumes are not over boosted.
If you have ever driven a domestic car from the '70s, you probably remember being able to parallel park with one finger on the wheel. While Grandma probably saw this as a sign of quality, it can cost half a horsepower at low rpm and as much as 3 hp at 5,000 rpm. Over the past 20 years automakers started paying more attention to steering effort versus driver feedback, but they still have to compromise for parking-lot maneuvers. Stock pumps have relatively high flow rates at low rpm to allow for those low-effort maneuvers. Unfortunately, this extra flow manifests itself as a disconnected feel on the highway and boiled fluid at the autocross or road course.
Turn One, the largest supplier of steering pumps and gears to Nextel Cup, has the solution: Blueprinted, reduced-flow, 40-series power-steering pumps for all '93-02 F-bodies and '84-and-later Corvettes. Turn One claims its pump will reduce or eliminate power-steering overheating and may improve steering feedback.
Turn One's pumps and steering gears were under the hood of four Winston and Nextel Cup champs in the last five years, so I figured I was in pretty good hands, but I still wanted to do some testing. Follow along as I test Turn One's pump at the autocross with some help from Auto Meter.
Unlike the LS1's pump, the...
Unlike the LS1's pump, the LT1 has a detached reservoir that allows it to run cooler than the LS1 F-bodies. Except for the pulley, the Turn One pump looks like a stock part that could have come off the shelf from the local parts house. Don't be fooled, Turn One starts with brand-new pumps, and the internals are extensively reworked. While Turn One asked us not to photograph its process, I can assure you it is not just changing springs or drilling bigger holes.
Pumps purchased from Turn...
Pumps purchased from Turn One with a pulley come assembled. If you buy just the pump or pulley you will need to get your hands on a power-steering pump pulley puller or you will have to get awfully creative to get it off the pump.
I recruited Glenn Estelle...
I recruited Glenn Estelle and his '92 LT1 Camaro as a test bed for the Turn One pump testing. Glenn's car is a daily driver that he autocrosses on a regular basis. Since Glenn had about a dozen autocrosses in his car before the pump change, I figured he would notice if the pump changed the steering effort and feedback.
Jeff Roethlisberger, the owner...
Jeff Roethlisberger, the owner of Turn One, took time out from building steering gears for Nextel Cup cars to explain the inner workings of his company's pumps and steering gears. Jeff spent 16 years at Saginaw Gear, GM's steering division, as a ride and handling engineer before striking out on his own and starting Turn One. Jeff also managed to bring his father on to help out after he retired as the Chief Engineer of steering systems at Saginaw steering division. Between Jeff and his father, there is about 50 years of power-steering experience.
Not only does Turn One use...
Not only does Turn One use its pump dyno to verify the quality of every pump, it shows a Turn One pump will free up about half a horsepower. While not a huge gain, it is a side benefit of the improved feel and lower fluid temps.
To determine PS fluid temps,...
To determine PS fluid temps, I tapped into the return line coming from the steering gear. Ideally, I would have tapped into the output of the pump, but the high pressure complicated the plumbing. I conned my friend Paul Ruggles into fabricating a small T-block, which allowed plumbing an Auto Meter oil temp gauge probe directly inline with the fluid path. Paul drilled the block's bore diameter oversize such that flow was not impeded by the sender probe.
Since Jeff had so many years...
Since Jeff had so many years of experience as a test driver, I wanted his thoughts on what he looked for in a well sorted out steering system. This is what he had to say: "When I evaluate steering performance I look for two things: The first is on-center feel. This is evaluated by small steering inputs, such as highway lane changes. The steering should feel crisp and precise, giving the driver a very 'connected to the road feeling.' The second is high-speed connectivity. As the vehicle generates lateral acceleration, the steering wheel torque should increase proportionally. This tells the driver the front wheels are turning. Most street-car steering is over boosted during this type of maneuver, leaving the driver with very little directional sense."After autocrossing with the Turn One pump, Glenn found the change to steering input to match Jeff's definition of a well sorted out steering system. He also found he could actually feel the difference camber and caster changes were making at the autocross. As predicted, Glenn found increased steering effort required in low-speed parking lot maneuvers, but he felt the tradeoff was worth it for the improved steering response.
At the autocross, Glenn documented...
At the autocross, Glenn documented the peak temperatures at the end of each run. Throwing out the highest and lowest temps from the day, the average temperature with the stock pump was about 175 F. The following week, with almost identical weather, the average temps were down a solid 10 degrees to 165 F. At 275 F, the seals in the power-steering system begin to deteriorate; while the LT1's OEM pump never got this hot, it proved the Turn One pump could reduce temps on an already-cool-running setup. In city and highway driving situations, Glenn consistently observed anywhere from 5- to 10- degree lower temperatures than the OEM pump. While our testing methods could have been more scientific, I feel the across-the-board temperature drops with the Turn One pump validate Turn One's claims.
Pump Chart From Turn One's Jeff Roethlisberger:
This graph represents pump flow (y axis) vs. pump rpm (x axis) of a stock production pump and a Turn One pump. Analyzing the solid line graph of the stock pump at approximately 900 rpm, the pump achieves flow control mode, which means the pump will deliver one constant flow to the steering box/rack at any rpm above 900. The 2.6-gpm flow control value is used here as an example. Depending on application, the actual flow control may vary.
Following the dashed line of the stock pump at 5,000 rpm, the pump delivery is 15 gpm. This is the total volume at 5,000 rpm, with 2.6 gpm being delivered to the box/rack. The other 12.4 gpm is being recirculated internal of the pump. This excess flow is what creates high fluid temperatures and robs horsepower.Analyzing the Turn One pump graph, it achieves 2.6-gpm flow control at 1,300 rpm. At 5,000 rpm, it's pumping a total of 10 gpm, recirculating only 7.4 gpm. That's 5 gpm less, resulting in lower fluid temperatures and less parasitic horsepower consumption.You may ask why the production pump is designed this way. The reason is to have more than adequate flow at low engine rpm. So, due to production variation, higher-than-average steering effort wouldn't be experienced during low-speed maneuvers.
ConclusionBased on the results of this testing, I think it pays to take a break from the constant search for the seat-of-the-pants improvement, and focus on the seat-of-the-palms. Based on Glenn's and my own driving experience with Turn One products, the full benefit of suspension mods and alignment changes will never be fully realized on most stock power-steering systems. A Turn One pump might be the best bang-for-the-buck suspension mod you can make.
|40-Series Steering Pump||Turn One||$225.00 |
|LT1 P/S Pump Pulley||Turn One||$65.00 |
|Autometer Oil Temp Gauge||4356||$144.95 |