Powered by Team Mondor
Page 3 of 4 FirstFirst 1234 LastLast
Results 21 to 30 of 38

Thread: Cam tuning info and guide

  1. #21
    Supramania Regular
    Adjuster's Avatar
    Join Date
    Apr 2005
    Location
    Meridian, Idaho, United States
    Posts
    1,166

    Default Re: Cam tuning info and guide

    The 5200rpm drop off is due more to the small turbo hot side, than the manifold design from what I've seen.

    Going up to the larger, bolt on T4 60-1 trim with a P trim (I think) hot side, it spooled up fine to red line, with no drop in power on the stock engine.

    However, when I added the longer stroke, and displacement of the stroker 3.24L engine, the larger turbo started to act like a stock CT-26 again. (With the power loss as the rpm exceeded about 5500rpm.)

    To keep spool similar to what I had, but still flow more both in and out, the larger T70 I have now should fit the bill. (Also went to a tubular exhaust manifold that will flow much better than the log style stocker.) The hot side AR is quite tight, so spool on this P trim hot side will be good, but since the AR is still larger than what I figure the bolt on T4 was, it should flow more. (And if it does not, I can get one that does flow more.)

    I just want to figure out the VE on my engine so the Translator Pro VE calc can be customized for my engine. (And I can get the most out of the stuff I have. No more changes to this car for awhile is the plan.)

  2. #22
    Banned

    Join Date
    Jan 2006
    Location
    Alachua, FL
    Posts
    4,271

    Default Re: Cam tuning info and guide

    Here's an example:


    from:
    http://www.supramania.com/forums/sho...9&postcount=18

    Tubular T4 mani, T70 turbo. You can see the tq curve come crashing down.

    That's just one example... I'll be taking my own data from my own engine, to see where I need to change the intake/exhaust/cams, but it gives me something to ponder

  3. #23
    Still in pieces...

    Join Date
    Jan 2008
    Location
    Port Coquitlam, BC
    Posts
    16

    Default Re: Cam tuning info and guide

    Quote Originally Posted by Doward
    Take this for my own 7M @ 5000rpm, 14.7psi, 97% VE =
    ((191*5000))/(3456) * 2.0 * 0.97 = ~536cfm of air.

    Now let's say we do this your way. I'm putting just under 6.0L of air into a 3.0L motor. So 197% VE.
    ((191*5000))/(3456) * 2.0 * 1.97 = ~1089cfm of air.
    There's an error in those calculations.
    When you did the calculations "My way", you didn't divide the RPM by two (because air is only ingested on every second stroke). When you do this, the cfm you calculate becomes 1089/2 = 544.5 CFM which is within 1.5% of your answer. We can call it a "quick and dirty ballpark figure".

    I do understand the mechanics behind what I'm doing, because I happen to be an engineer too. I'm an electronics engineer, but the math ends up being very similar, and I'm EXTREMELY familiar with harmonics (ie Forrier analysis).

    We can argue semantics all day long, but we both land close enough to the target that the difference can be neglected anyway. I've spent hundreds of hours tuning, and one thing I can attest to is that calculations only get you 95% of the way there. I've seen two completely identical engines that end up with different tunes because the nuances of the engine lend a variable to any equation you use. This is why we dyno tune instead of ONLY mathematically tuning our cars.

    I had one customer come in with a custom engine in his 97 Z28 Camaro who happened to be an engineer as well. He pre-calculated all of his airflow numbers, and came up with a base-tune from which to work from. He was remarkably accurate, but was off a little in a couple of places. The dyno fixed that up right quick!

    As you know, there are no hard and fast rules because there are SOOOO many variables to work from here. You're taking a few more than I am into account. I'm just saying from my experience, a few of the variables can be neglected which drastically simplifies the process and gets you close enough that the fine-tuning can be done where it needs to be. Engines are complicated beasts with things from the quality of a cast to the sharpness and diameter of a grinding stone introducing a number of variables.

  4. #24
    Banned

    Join Date
    Jan 2006
    Location
    Alachua, FL
    Posts
    4,271

    Default Re: Cam tuning info and guide

    Quote Originally Posted by D-Dayve
    There's an error in those calculations.
    When you did the calculations "My way", you didn't divide the RPM by two (because air is only ingested on every second stroke). When you do this, the cfm you calculate becomes 1089/2 = 544.5 CFM which is within 1.5% of your answer. We can call it a "quick and dirty ballpark figure".
    Um... yes I did. Divide cubic inches * rpm by 1728 to convert to cubic feet. I multiply the 1728 x 2 (making 3456) because of the 4 stroke setup. Instead of multiplying by .5 in the numerator, I multiply the denominator by 2.

    Why did you divide by 2 yet again, to get close?

  5. #25
    475rwhp459torq an climbin
    QWIKSTRIKE's Avatar
    Join Date
    Apr 2005
    Location
    Some where out there
    Posts
    1,172

    Default Re: Cam tuning info and guide

    Very interesting thread here.....I have the 272 cams from BC and I ended up advancing the intake 2 degrees only to get the most power, and any other way caused a power loss. Any way I have at least a 3 litre or slightly larger intake in combination with these cams. soooo......whats my possible VE on my .040 over bored motor.

  6. #26
    Banned

    Join Date
    Jan 2006
    Location
    Alachua, FL
    Posts
    4,271

    Default Re: Cam tuning info and guide

    You can roughly figure VE from your dyno graph.

  7. #27
    Supramania Regular
    bowsercake's Avatar
    Join Date
    Aug 2005
    Location
    Irvine, Ca
    Posts
    828

    Default Re: Cam tuning info and guide

    I believe the stock engine pulls 18 vacuum at idle. With my cams adjusted I am pulling close to 30. Should my goal me to get it to 18? However, it would also seem that different cams would pull a different amount of vacuum when tuned.

  8. #28
    Junior Member

    Join Date
    May 2007
    Location
    BHG
    Posts
    185

    Default Re: Cam tuning info and guide

    I have the BC264 cams & for daily driving have them set at +2 I & 0 E.
    This setting has good power to around 5000rpm.
    For dyno runs I change it to 0 I & -2 E for maximum power around 6000.
    From experience I have found that advancing your intake will usually kill your top end.

  9. #29
    "The Boss"
    IHI-RHC7's Avatar
    Join Date
    Apr 2005
    Location
    Oregon
    Posts
    1,310

    Default Re: Cam tuning info and guide

    Sorry to bring an old thread alive from the dead, but I can't seem to figure out why anyone hasn't bothered to correct one major nuance in both sides of this argument.
    Quote Originally Posted by D-Dayve
    100% VE means a 3.0L engine uses 3.0L of air over a complete cycle (2 revolutions). If you run boost, you can get say 4.0L of air into a 3.0L engine, meaning you have a VE of 133.3%. That's the way it is, plain and simple. If you don't agree with me, fine, but if you do a little research (wikipedia says: "Volumetric efficiencies above 100% can be reached by using forced induction such as supercharging or turbocharging"), and that's how I and all the tuners I've known have always understood VE. If you don't agree with me, that's fine, but it is what it is, and I can't explain it better than that.
    And
    Quote Originally Posted by DOWARD
    Now let's say we do this your way. I'm putting just under 6.0L of air into a 3.0L motor. So 197% VE. ((191*5000))/(3456) * 2.0 * 1.97 = ~1089cfm of air.

    So which is it?
    I believe that you both know that it is completely impossible for a 3 liter engine to ingest any more than 3 liters of air every 2 rotations. It is not a variable displacement engine, and displacement is just this: the volume of air the engine ingests ever two crankshaft revolutions. So why use an argument that isn't backed by physics, and mucks up the point that is being made?
    (also, this is why we piston heads get pissed off when rotary guys claim that they have 1.3 L engines. The 13b ingests 1.3 liters every crankshaft rotation, so in order to put into the same category as, say a 7m, it's displacement is actually 2.6 L)

    We don't turn up our boost volume, we turn up our pressure. In fact pressure is not even all that useful, because heat plays a vary important role in determining density. MrWOT touched on that briefly. But again, density is only a proxy to what it is that the engine actually cares about. And what does the engine care about?

    Mass. Plain and simple, any engine runs on the stoichiometric combustion of a certain mass of air(actually, oxygen, but we won't get into that) mixed with a certain mass of fuel. So what we really need to figure out is the mass flow rate of the engine. CFM is nice, but what are turbos rated in? lbs/min. Injectors in US standards? lbs/min.

    Now I know, a pound isn't mass, it's force, but we're americans, and we pretend like it is mass. 1kg=2.2 lbs down here on earth's surface, and really everything should be done in kg/min, or kg/s but as long as you don't plan on tuning your can on mount everest, or mars, lbs/min is a suitable measurement.

    So. you take Doward's equations to the next level, and find that the mass flow rate is the true measure of volumetric efficiency. 1lb/min = 14.472 cfm, so you can see that his engine, according to his calculations, at 97% VE (100% IC efficiency, 100% adiabatic compressor efficiency, etc...) 536cfm = 37.04 lbs/min. If his VE were 100%, he would be ingesting 38.2lbs/min.

    Why does any of this matter? because at 14.7 psi gauge, (29.4 psi abs) it is completely impossible for any 3 L engine to ingest more than 38.2 lbs/min at 5000 RPM unless there is a harmonic, inertial overfilling of the cylinders in addition to the operating boost pressure.

    We also care about this because it means that Doward should be running a turbo that is on its peak efficiency island when it is pushing 38-40 lbs/min of air. He should also be running cams that efficiently allow 38-40 lbs/min of air to pass through the valves when they are opening and closing almost 42 times per second. (all six cyls combined, of course)

    Also, each valve is opening and closing 42 times per second. That means that the first harmonic mode, or the natural frequency of the engine at 5000 rpm is 42 Hz. This is the frequency that his intake runners and plenum should be tuned to. So a "mass packet" of air should reflect off of the back side of a closed valve, move through the runner, expand in the plenum and reflect off of the plenum wall, compress back into the runner and pick up velocity, and finally, arrive back at the valve to find it open, and not closed. All of this must happen 42 times per second at 5000 rpm in Doward's engine in order for his manifold to be tuned to the engine. All of this depends on the velocity of the air, the cross section of the port and runner, the length of the runner, and the volume of the plenum, to name just a few of the variables we're talking about here.

    So the manifold controls how long it takes for the pressure wave/"mass packet" of air to get back to the valve 42 times every second. Guess what controls whether it finds an open valve or a closed valve? You guessed it, the cams. You can have a perfectly tuned intake setup, but if your cams aren't both sized right, and timed right to provide an open door when the wave returns, you won't be at peak efficiency. Physics gets you far enough to pick out the right equipment and get a base tune, and the Dyno is where the magic happens. You may not have a picture perfect setup, but any setup can be maximized to provide the best overall operating conditions, and that is where D-Dayves first comments in this thread originate from.

    Again, sorry to bring a dead thread back to life over a little thing, but as you said, Doward, misinformation is bad...

    -Jake
    "I've got a machined head, It's better than the rest!", Read this

  10. #30
    475rwhp459torq an climbin
    QWIKSTRIKE's Avatar
    Join Date
    Apr 2005
    Location
    Some where out there
    Posts
    1,172

    Default Re: Cam tuning info and guide

    Quote Originally Posted by IHI-RHC7 View Post
    Sorry to bring an old thread alive from the dead, but I can't seem to figure out why anyone hasn't bothered to correct one major nuance in both sides of this argument.

    And

    I believe that you both know that it is completely impossible for a 3 liter engine to ingest any more than 3 liters of air every 2 rotations. It is not a variable displacement engine, and displacement is just this: the volume of air the engine ingests ever two crankshaft revolutions. So why use an argument that isn't backed by physics, and mucks up the point that is being made?
    (also, this is why we piston heads get pissed off when rotary guys claim that they have 1.3 L engines. The 13b ingests 1.3 liters every crankshaft rotation, so in order to put into the same category as, say a 7m, it's displacement is actually 2.6 L)

    We don't turn up our boost volume, we turn up our pressure. In fact pressure is not even all that useful, because heat plays a vary important role in determining density. MrWOT touched on that briefly. But again, density is only a proxy to what it is that the engine actually cares about. And what does the engine care about?

    Mass. Plain and simple, any engine runs on the stoichiometric combustion of a certain mass of air(actually, oxygen, but we won't get into that) mixed with a certain mass of fuel. So what we really need to figure out is the mass flow rate of the engine. CFM is nice, but what are turbos rated in? lbs/min. Injectors in US standards? lbs/min.

    Now I know, a pound isn't mass, it's force, but we're americans, and we pretend like it is mass. 1kg=2.2 lbs down here on earth's surface, and really everything should be done in kg/min, or kg/s but as long as you don't plan on tuning your can on mount everest, or mars, lbs/min is a suitable measurement.

    So. you take Doward's equations to the next level, and find that the mass flow rate is the true measure of volumetric efficiency. 1lb/min = 14.472 cfm, so you can see that his engine, according to his calculations, at 97% VE (100% IC efficiency, 100% adiabatic compressor efficiency, etc...) 536cfm = 37.04 lbs/min. If his VE were 100%, he would be ingesting 38.2lbs/min.

    Why does any of this matter? because at 14.7 psi gauge, (29.4 psi abs) it is completely impossible for any 3 L engine to ingest more than 38.2 lbs/min at 5000 RPM unless there is a harmonic, inertial overfilling of the cylinders in addition to the operating boost pressure.

    We also care about this because it means that Doward should be running a turbo that is on its peak efficiency island when it is pushing 38-40 lbs/min of air. He should also be running cams that efficiently allow 38-40 lbs/min of air to pass through the valves when they are opening and closing almost 42 times per second. (all six cyls combined, of course)

    Also, each valve is opening and closing 42 times per second. That means that the first harmonic mode, or the natural frequency of the engine at 5000 rpm is 42 Hz. This is the frequency that his intake runners and plenum should be tuned to. So a "mass packet" of air should reflect off of the back side of a closed valve, move through the runner, expand in the plenum and reflect off of the plenum wall, compress back into the runner and pick up velocity, and finally, arrive back at the valve to find it open, and not closed. All of this must happen 42 times per second at 5000 rpm in Doward's engine in order for his manifold to be tuned to the engine. All of this depends on the velocity of the air, the cross section of the port and runner, the length of the runner, and the volume of the plenum, to name just a few of the variables we're talking about here.

    So the manifold controls how long it takes for the pressure wave/"mass packet" of air to get back to the valve 42 times every second. Guess what controls whether it finds an open valve or a closed valve? You guessed it, the cams. You can have a perfectly tuned intake setup, but if your cams aren't both sized right, and timed right to provide an open door when the wave returns, you won't be at peak efficiency. Physics gets you far enough to pick out the right equipment and get a base tune, and the Dyno is where the magic happens. You may not have a picture perfect setup, but any setup can be maximized to provide the best overall operating conditions, and that is where D-Dayves first comments in this thread originate from.

    Again, sorry to bring a dead thread back to life over a little thing, but as you said, Doward, misinformation is bad...

    -Jake
    I like this analogy Jake, great explanation for a lay man like me. I have at least a 3.0-3.1litre intake and a set of BC275 cams and a .060 over bored block with 9:1 pistons along with a gt4067r. What rpm do you think this setup should peak at?

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •