Z Greek Posted November 5, 2012 Share Posted November 5, 2012 I built a budget flow bench a couple of months ago. I have spent the time since I built it refining, and calibrating. I built it per a design from a book by David Vizard, and had a calibration plate machined out of lexan per a design by a friend of Vizard's, Dr. Helgesen. I say all this because although this bench was built on a budget, it is pretty accurate, especially if one is just comparing before and after, or one head to another. Initially I was having trouble getting repeatability, and traced the problem to varying line voltage in my shop. I have since run a separate, designated 20 amp circuit using over-sized wire to minimize voltage drop to my air source (two 6 hp shop vac's!) So I finally have the bench working well enough to achieve repeatable results. I also pieced together a fixture for opening the valve incrementally. I have a P90, and also a P79 in completely stock, unmolested condition. I flowed the P90 first, doing the intake first, and then the exhaust. While flowing the intake, I had an N36 manifold bolted to it. The exhaust was left open at the port. I realize not having a stub exhaust pipe bolted to the head affects flow, but I did the P90, and the P79 the same, so I think any error should equalize between the two tests. Most everyone I talk to, or read about praises the superiority of the P90 exhaust port, and how "evil" the P79 port is with the liners. Well gents, look at the results below. Not only did the stock P79 flow as well as the P90, it was virtually identical. I did not flow the P79 intake yet, but since the P79 and P90 are identical on the intake side, I do not expect any surprises. P79 VS P90 flow characteristics Home-built floating depression flow bench. Calibrated with Helgesen Plate. P90 Intake P90 Exhaust P79 Exhaust Valve open increment Inches of H2O CFM Inches of H20 CFM Inches of H2O CFM 0.05 44 30 18.2 18 18 20 0.1 40.7 60 16.9 50 16.8 40 0.15 37 105 15.8 71 15.8 70 0.2 32.2 148 15 86 15 85 0.25 30 180 14.5 94 14.5 95 0.3 28.5 200 14.3 97 14.3 98 0.35 31 165 14.2 100 14.2 100 0.4 31 165 14.2 100 14 105 0.45 30.8 170 14.2 100 14 105 0.5 30.2 175 14.2 100 14 105 0.55 30 180 14.2 100 14 105 0.6 29.5 185 14.2 100 13.9 108 Quote Link to comment Share on other sites More sharing options...
Z Greek Posted November 5, 2012 Author Share Posted November 5, 2012 Well that did not work, hang tight! Quote Link to comment Share on other sites More sharing options...
Z Greek Posted November 5, 2012 Author Share Posted November 5, 2012 Well I thought I had some fun stuff to share, but the site will not allow me to attach an excel spreadsheet, and if I try typing the data in manually, it bunches it all up. The long and short of it, the stock P79 flows just as good as the P90 (on my budget flow bench). The big difference, you can change the P90 port. Short of cleaning up the transition from the seat to the liner on P79, you are pretty much stuck the way it is. I have a P79 on my Chumpcar endurance racer that I spent a ton of time on. I am getting ready to take it out of the car and will flow it when I tear the engine down. It will be interesting whether I went forwards or backwards! The Chump L28 made 178 to the wheels on a dynojet 24 last summer. The engine now has 45 hours of racing on it. I am going to try to get it on the dyno one more time before I tear it apart to see how 45 hours of pretty intense use affected it. Quote Link to comment Share on other sites More sharing options...
loy Posted November 5, 2012 Share Posted November 5, 2012 Put in google docs and put a link. Quote Link to comment Share on other sites More sharing options...
Z Greek Posted November 5, 2012 Author Share Posted November 5, 2012 https://docs.google.com/open?id=0BzPD5idjMQ5BYlFLOHNpUEw4WWM Per loy's suggestion above, here is a link to the flow data on the P79 vs P90 I did today My 14 year-old did this for me, hopefully it works! Quote Link to comment Share on other sites More sharing options...
beermanpete Posted November 5, 2012 Share Posted November 5, 2012 https://docs.google.com/open?id=0BzPD5idjMQ5BYlFLOHNpUEw4WWM Per loy's suggestion above, here is a link to the flow data on the P79 vs P90 I did today My 14 year-old did this for me, hopefully it works! It requires permission to see the file. Perhaps you can change a setting to make it public? Quote Link to comment Share on other sites More sharing options...
Z Greek Posted November 5, 2012 Author Share Posted November 5, 2012 Here are some pictures of the bench, manometer, calibration plate, valve opener, etc. Quote Link to comment Share on other sites More sharing options...
Z Greek Posted November 5, 2012 Author Share Posted November 5, 2012 Here are some pictures of the bench, manometer, calibration plate, valve opener, etc. https://docs.google.com/open?id=0BzPD5idjMQ5BYlFLOHNpUEw4WWM I put my 14 year old back on the task. Try this?! Quote Link to comment Share on other sites More sharing options...
beermanpete Posted November 5, 2012 Share Posted November 5, 2012 https://docs.google.com/open?id=0BzPD5idjMQ5BYlFLOHNpUEw4WWM I put my 14 year old back on the task. Try this?! That worked. Quote Link to comment Share on other sites More sharing options...
TimZ Posted November 5, 2012 Share Posted November 5, 2012 That worked. That works for me too. So are the flow numbers corrected to some standard pressure, like 25" H2O? Quote Link to comment Share on other sites More sharing options...
Z Greek Posted November 5, 2012 Author Share Posted November 5, 2012 That worked. Good to hear beerman, I am so technically lame! Glad I have a smart kid! Quote Link to comment Share on other sites More sharing options...
Z Greek Posted November 5, 2012 Author Share Posted November 5, 2012 That works for me too. So are the flow numbers corrected to some standard pressure, like 25" H2O? The bench is a "floating depression bench" That being said, the Helgesen plate I used to calibrate is supposed to simulate flow at 28 inches of WC. The machine shop I had make the plate also made one for a fellow who had it flowed on a Superflow 600, and maximum error was 4 cfm. Close enough for me. The plate is shown in the pictures I attached. The holes (orifices) are 160 CFM, 80 CFM, 40 CFM, 20 CFM, 10 CFM, and 5 CFM. Covering and uncovering the orifices in order, you can create a spreadsheet converting inches of water column, to CFM in 5 CFM increments. While I was fighting voltage fluctuations, I repeated this process many, many times. It is now repeatable, and as I said earlier, it is at the very least good for comparisons between heads, and "before and after," work. Quote Link to comment Share on other sites More sharing options...
Z Greek Posted November 5, 2012 Author Share Posted November 5, 2012 One other note of mention, I did not use a bore simulator. The opening on my bench is approximately 3.5 inches. I am going to make bore simulators for 87 and 89mm, but it will have to wait. Right now, I feel the comparison between the two heads is valid, although the cfm numbers may not be dead on due to lack of a bore simulator. Fun stuff though! I am anxious to start from scratch on the stock P79 for my endurance racer, and see if I can improve on the 178 rwhp I made with the head I ported by the seat of my pants! This flow bench is for my own port development, and my own amusement, just thought I would share the data I have collected. Quote Link to comment Share on other sites More sharing options...
TimZ Posted November 5, 2012 Share Posted November 5, 2012 The bench is a "floating depression bench" That being said, the Helgesen plate I used to calibrate is supposed to simulate flow at 28 inches of WC. The machine shop I had make the plate also made one for a fellow who had it flowed on a Superflow 600, and maximum error was 4 cfm. Close enough for me. The plate is shown in the pictures I attached. The holes (orifices) are 160 CFM, 80 CFM, 40 CFM, 20 CFM, 10 CFM, and 5 CFM. Covering and uncovering the orifices in order, you can create a spreadsheet converting inches of water column, to CFM in 5 CFM increments. While I was fighting voltage fluctuations, I repeated this process many, many times. It is now repeatable, and as I said earlier, it is at the very least good for comparisons between heads, and "before and after," work. I was just trying to understand what I was looking at, and how to interpret the columns showing the pressure for each measurement. Your answer above implies that the CFM numbers are already corrected to 28", and the pressure readings are not relevant - is that correct? Quote Link to comment Share on other sites More sharing options...
PMC raceengines Posted November 5, 2012 Share Posted November 5, 2012 The exhaust port in both heads , are ok with mild mods and just blending , its the inlet that needs work , and the 44mm intake will make 300 hp with a stock valve , its only small gains with a bigger valve with a big bore with a small bore the 44 mm is spot on , working the seat and short turn and some blending is all you need in your setup , Quote Link to comment Share on other sites More sharing options...
Z Greek Posted November 5, 2012 Author Share Posted November 5, 2012 The exhaust port in both heads , are ok with mild mods and just blending , its the inlet that needs work , and the 44mm intake will make 300 hp with a stock valve , its only small gains with a bigger valve with a big bore with a small bore the 44 mm is spot on , working the seat and short turn and some blending is all you need in your setup , Thanks Peter, I am just trying to be a bit more "scientific" on my porting job this time, lol. I am really anxious to see if I can get more flow using this approach rather than the seat of the pants, approach on the last "budget endurance engine," you helped me with. The race for our home track in Spokane was just announced for 2013, and the Guiness World record folks will be there. It will be a 36 hour enduro on July 5-7! It will be the longest closed course race in the world! Ultimate power is not really what I need to compete, in this one, just durability! But as you and I have discussed, horsepower is a drug, and once you find a little, you want more! Quote Link to comment Share on other sites More sharing options...
Z Greek Posted November 5, 2012 Author Share Posted November 5, 2012 I was just trying to understand what I was looking at, and how to interpret the columns showing the pressure for each measurement. Your answer above implies that the CFM numbers are already corrected to 28", and the pressure readings are not relevant - is that correct? According to Vizard, both numbers are relevent, but for comparison sake, the CFM numbers are what you can use to compare to other benches, etc. You would have to read Vizard's books for a good explanation, but here it is in a nutshell. Vizard prefers the floating depression bench for much of his testing. If you think about it, the cylinder sees wild swings in pressure differential. The highest it sees is when both valves are off seat, and the piston is virtually parked at tdc. This is because of the exhaust exiting stage left at close to the speed of sound, and pulling in the intake charge as it leaves. For this reason, testing low lift at very high water column numbers is more realistic. This is all according to Vizard, but it sounds very logical, and he has been chasing airflow and horsepower for 50 years! Again, this is all for fun, and purely for my own learning and benefit. I am a hobbyist, not a professional engine builder like Peter at PMC, he is the true authority! I posted it because I thought some of you might find it interesting. After I get the head off of my Chumpcar engine, I'll flow it for reference and post if you guys want, but please take it in context. I am just a 50 year old who found a new passion after 35 years of playing with cars, racing and horsepower! Quote Link to comment Share on other sites More sharing options...
Ben's Z Posted November 5, 2012 Share Posted November 5, 2012 Kick ass stuff Andy! My cam and rockers are on their way back from the west coast. Going to finish the long block soon, be expecting my call. Quote Link to comment Share on other sites More sharing options...
Z Greek Posted November 5, 2012 Author Share Posted November 5, 2012 Kick ass stuff Andy! My cam and rockers are on their way back from the west coast. Going to finish the long block soon, be expecting my call. Glad to hear you are making progress Ben! Did you go with a stock grind on the cam? Call anytime, you know I love talking about this stuff! Quote Link to comment Share on other sites More sharing options...
Gollum Posted November 6, 2012 Share Posted November 6, 2012 I'm always glad to see more data to support my serious unimpressed opinion of the P90 > P79 debate, especially as it applies to turbo application. I've been telling people for years just to turbo the extremely affordable flat top + P79 combo that can be found nearly for free everywhere, but yet people seem to want to hold on to some stigma that the L28ET longblock is just that much "better".... Thank you for your efforts and the data. Quote Link to comment Share on other sites More sharing options...
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