Exhaust to Intake flow ratios??????
06-19-2007, 07:56 PM
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Exhaust to Intake flow ratios?????? O.k. I tried to do a search and it's on the fritz so I'm just going to ask.
I'm looking at putting a set of heads on a 99 FRC and I see all kinds of different flow ratios between heads. From 84% on the Trick Flow down to 68% on some of the ET heads (the 11.5 degree 215's).
So for an engine that will see street driving and road racing, what's better? A higher number or a lower number? What do LSx's like. I'm guessing that the higher numbers are better for forced and nitrous since you are trying to fit 10lbs of **** in a 2 lb bag. But for N/A what type of numbers are you looking for?
The car has CAI, Melrose LT's, LS6 intake and I'm thinking of doing a F13 when I do the heads.
I'm looking at putting a set of heads on a 99 FRC and I see all kinds of different flow ratios between heads. From 84% on the Trick Flow down to 68% on some of the ET heads (the 11.5 degree 215's).
So for an engine that will see street driving and road racing, what's better? A higher number or a lower number? What do LSx's like. I'm guessing that the higher numbers are better for forced and nitrous since you are trying to fit 10lbs of **** in a 2 lb bag. But for N/A what type of numbers are you looking for?
The car has CAI, Melrose LT's, LS6 intake and I'm thinking of doing a F13 when I do the heads.
06-19-2007, 09:55 PM
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Ive never heard of head flow looked at in this manner. I've been taught that flow under the curve is what to look for. No one cares that a head flows 400cfm at .700" if it only gets 95cfm at .300"
Right now Trick Flow heads are making the most power on stock cubes. Go look into them and look in the dyno section for more info on this stuff.
Right now Trick Flow heads are making the most power on stock cubes. Go look into them and look in the dyno section for more info on this stuff.
06-19-2007, 10:58 PM
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Ideally the greater the ratio, the better the set of heads. This is misleading though because you have to take all the aspects into account. Flow numbers throughout the lift range, whether you are using an intake or exhaust biased cam, what size the runners are, among tons of other aspects. You have to take them all into account to determine what head is right for you. Exhaust to intake ratio is just another tool amongst many that should help you determine what set of heads is right for you.
06-20-2007, 11:50 AM
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Since you are wanting this to be a street driven motor, you should look for the best low to mid lift flowing heads. If you plan on keeping this motor around 7500 rpm most of the time, I would say look at your .500" + lift number's. But you still need to have some preaty good mid lift flow number's. Also remember when you are compairing flow number's to different heads, try to look for the bore size that they were tested on is the same and that the exhaust is flow tested with or without a pipe (also make sure the pipe diameter is the same size). The last peice of the puzzle is finding a independant company who has flow tested the different heads on the same flow bench. That should give you the best apples to apples compairison. Whatever brand of heads that you buy MAKE SURE THAT YOU HAVE A CUSTOM CAM made just for your intended use.
