This plate is like a plenum spacer. Its purpose is to evenly distribute airflow to all cylinders through the intake manifold and not to add volume to the upper plenum like all previous spacers that do nothing. This piece is 1/8" thick. It uses all the stock fastening hardware. It simply bolts on with nothing more to modify.
Thisplate was designedon a 2000 CFM airflow generator measuring the actual airflow at the valve opening. Something like this plate or upper plenums can NOT be designed on a flow bench. They must be designed duplicating what is actually happening inside the manifold under boost. This is exactly whatwasdone and that is why this plate works so good.
After market plenums like the Kenny Bell, Precision and Acufab do not distribute airflow evenly either.That is why RJC hasdeveloped a plate for each of these plenums.RJC could not use the stock power plate as they flow differently than the stock plenum.
RJChas found that although the Hemco plenum is better than stock it does not distribute the air even either. There is no way you can distribute the flow evenly with a square hole, period.You can not correct the Hemco plenums. They have too small of open area to manipulate the incoming air. The Hemco reduces the high/low cylinder airflow differential but actually makes the middle two cylinders the leanest. These middle two have shared head bolts, this is not the most ideal situation to say the least.
The number 1 and 2 qualifiers in the TSM class at the 2002 GS Nats. were both running RJC A. D. Power Plates. Now most of the cars in the TSM series race are running one.
Plenum flow charts comparison each cylinder to average of all cylinders for that plenum.
Stock plenum with AD Power Plate-S
1 -5% 2 -2%
3 +5% 4 +4%
5 -5% 6 +2%
Flow Range; 10%
Stock Plenum
1 -40% 2 -81%
3 +24% 4 -33%
5 +68% 6 +63%
Flow Range; 149%
Kenny Bell Plenum with AD Power Plate-K
1 +5% 2 -5%
3 +1% 4 0%
5 -1% 6 +1%
Flow Range; 10%
Kenny Bell 70mm Plenum
1 -44% 2 -52%
3 +32% 4 -8%
5 +30% 6 +40%
Flow Range; 96%
Precision 70mm Plenum
1 -56% 2 -59%
3 +36% 4 -2%
5 +27% 6 +36%
Flow Range; 95%
Precision Plenum with AD Power Plate-P
1 -3% 2 +2%
3 -3% 4 +2%
5 +2% 6 -2%
Flow Range; 5%
Hemco 70mm Plenum
1 -20% 2 -21%
3 +21% 4 -13%
5 -10% 6 +14%
Flow Range; 42%
Hemco Style plate (Just for kicks)
1 -35% 2 -29%
3 +23% 4 +24%
5 -2% 6 +19%
Flow Range; 59%
