The Red Baron seemed to be stuck at 115 MPH during the 2015 and 2016 race seasons, regardless of fueling and boost changes. We suspected choke conditions at the exhaust ports. We modified the timing of the exhaust valve opening and closing events by designing a custom camshaft that would allow for greater air flow, and therefore power, particularly at high RPM. The discussion below compares the OEM camshaft to the custom, more aggressive, racing camshaft.
Thank you to Faith at webcamshafts.com for the great work!
Looking at the OEM cam profile first: As the valve is lifted, the air flow transitions from “very low” flow to the “medium” air flow range which has steadily increasing air flow as the valve lifts further. The “high” flow range is the most productive and important region of air flow. Flow bench testing showed that the OEM exhaust valve achieved peak flow at 0.250″ lift.
Looking at the custom “racing” cam profile: By lifting the valves faster, lifting them further, and holding them open longer, the Morini engine breathes better, particularly at high RPM which is essential for land speed racing. Compared to the OEM spec, The Red Baron exhaust modification looks modest by the numbers. These numbers are approximations, keeping our “speed secrets”
- Increased exhaust duration by 7 degrees (seat to seat)
- Increased exhaust valve lift by 0.015″
- Reduced valve overlap by 15 degrees (seat to seat)
While these numbers would be interpreted as modest bumps in performance, the graphs show a more dramatic change (below).
The exhaust valve is opened earlier and is opened farther which provides major gains in air flow during the first half of the exhaust stroke. There is a small loss in air flow during the second half of the exhaust stroke because the valve is closing earlier. This was done to minimize valve overlap, thereby minimizing boost pressure loss. An important note is that the slope of the valve opening and closing is relatively similar between the OEM and racing camshafts. This means that the valve stem is not stressed significantly more from “slamming” open and closed more quickly.
The result: The Red Baron immediately jumped in top speed from 115 mph to 120+ mph, coupled with larger exhaust valves (read here).
P.S. The ultimate red-line of the engine hasn’t changed much, still around 8,000 RPM. We had hoped the new camshaft might increase the redline, but no. The air and fuel still has to navigate a crazy maze of 90-degree turns into and out of the combustion chamber that limits its overall ability to process the air, fuel, and exhaust.