BOOST!
Everyone loves boost!One common myth I constantly battle is that customers believe that they do not need to increase cylinder head performance because the turbos take care of the extra flow...
THAT IS BULLSHIT!
Flashback to last year where we talked about testing heads at a higher depression, where the port in question would decrease CFM when you increased depression.In a lot of cases, boost will DECREASE cylinder head performance!
How does that relate to boost?Boost by definition is a greater differential in pressure between the cylinder and intake tract. So instead of increasing cylinder depression to increase air flow, you are increasing intake pressure to do the exact same thing!So when you have an unstable port that crashes going from a measly 28 inches to 40 inches of depression, imagine how much harder it will crash when you add 15psi of boost OR 400+ inches of water!
Perfect example is John's VL747 that runs a single cam RB30, where we were able to increase his power by 30rwkw AND a broader torque curve with just cylinder head modifications!
So when you're building a boosted motor, make sure your intake tract is up to scratch!
THAT IS BULLSHIT!
Flashback to last year where we talked about testing heads at a higher depression, where the port in question would decrease CFM when you increased depression.In a lot of cases, boost will DECREASE cylinder head performance!
How does that relate to boost?Boost by definition is a greater differential in pressure between the cylinder and intake tract. So instead of increasing cylinder depression to increase air flow, you are increasing intake pressure to do the exact same thing!So when you have an unstable port that crashes going from a measly 28 inches to 40 inches of depression, imagine how much harder it will crash when you add 15psi of boost OR 400+ inches of water!
Perfect example is John's VL747 that runs a single cam RB30, where we were able to increase his power by 30rwkw AND a broader torque curve with just cylinder head modifications!
So when you're building a boosted motor, make sure your intake tract is up to scratch!
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Mad Manifold Mondays
You would be surprised how many people come to me looking to upgrade their cylinder heads because they think it is a restriction.One of the first things I ask before upgrading a pair of cylinder heads is "What manifold are you running?"I have seen "race" super victor manifolds that have been "polished", yet it kills 10% of the systems performance.Our racing single planes are more like 1-2% loss, so in a 300cfm application, thats 25cfm, thats 50hp (in an 8cyl application) for a fraction of the price of porting a set of cylinder heads!So before spending big $$$ on cylinder heads, ask us about your manifold first!
Pressure Differential
You want to know the difference between these 2 ports?Absolutely nothing.It is the same port, only flowed at different test pressures.Why do we do this?It tells us how stable a port is. We all learn and advertise about flow figures at 28 inches of water, all our calculations are done at 28 inches of water, so logically we test at 28 inches.But does a cylinder create only 28" of depression?No. Much, much more.(Note: Yes, carburettor manifolds typically operate at 1-1.5" of depression, but that's a different kettle 'o fish)In order for us to try and understand how a port will behave at higher depression, we simply crank up the pressure differential.So at 1.00" lift, at 40 inches of depression, this port flows 438cfm. But we need to be able to compare that to a test at 28 inches, so we calculate it to be equal to 365cfm at 28 inches of depression (factor of 1.20).Why the difference?With the bigger pressure differential, the port has to work harder in order to keep up. If you have an unstable port, it will crumble under the pressure (pun intended)It's one thing to make a port flow at 28" and make it look appealing to your customer, its another thing to then make that performance show on the track
Telltale Signs
The cylinder head is a very detailed window into how an engine is operating, from tuning to mechanical operations.We recently pulled down a set of our LS1 heads for a customer after a season of racing. What we enjoyed seeing is the intake port being absolutely spotless! This tells us that the intake system has been properly tuned for its intended cubic capacity and RPM.No reversion, which means this cylinder head has correctly tuned velocities and correctly tuned runner lengths.
When you want custom tailored cylinder heads, think Precision Porting
Edge Orifice Plates
Want to know how I keep my testing accurate and consistent? These beauties!Known as "Edge Orifice Plates", they are accurately machined orifices (holes, if you wish) that have a known discharge coefficient (a known amount of airflow for a given cross sectional area) that let me accurately calibrate my flowbench.Like an engine and chassis dyno, the flowbench must be regularly calibrated in order to maintain accurate and consistent testing.When you're aiming for the top, you need your RnD to be consistent, otherwise you're only lying to yourself and your customer.And at the end of the day, the track will tell you if you're doing your job properly
