Cam tuning info and guide

Adjuster

Supramania Contributor
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.)
 

Doward

Banned
Jan 11, 2006
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Here's an example:
p919037_1.jpg


from:
http://www.supramania.com/forums/showpost.php?p=438899&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 ;)
 

D-Dayve

Still in pieces...
Doward said:
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.
 

Doward

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Jan 11, 2006
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D-Dayve said:
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?
 

QWIKSTRIKE

475rwhp459torq an climbin
Apr 3, 2005
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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.
 

bowsercake

New Member
Aug 24, 2005
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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.
 

BLACKCAT

New Member
May 24, 2007
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BHG
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.
 

IHI-RHC7

"The Boss"
Apr 1, 2005
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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.
D-Dayve said:
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
DOWARD said:
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
 

QWIKSTRIKE

475rwhp459torq an climbin
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IHI-RHC7;1007306 said:
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?
 

IHI-RHC7

"The Boss"
Apr 1, 2005
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I'd have to know your runner length, average cross sectional area, and the distance to the back face of the plenum to even come close to guessing! I know those cams should have a sweet spot in the 5500-7500 range, but it all depends on the flow capabilities of your header, the hot side of your turbo, downpipe choice, etc... on top of the intake side of things. :icon_razz
-Jake
 

Doward

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Jan 11, 2006
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Jake, it's just mathematical manipulation. 6.0L of air @ 14.7 absolute psi = 3.0L of air @ 29.4 absolute psi. Gas laws in action, baby!

I do see where you'd correct me though - it's my own fault, really. I really hate trying to dumb things down, and generally I do it without explaining the calculations - good job on straightening that out, though ;) The fact that a 3.0L motor physically WILL NOT ingest more than 3.0L of air in a complete cycle, is exactly why you do not exceed 100% efficiency without proper intake harmonics.

The problem stems from (as I mentioned a moment ago) you can look at any particular mass of air as 2x the volume @ 1/2 the pressure (letting you think that you have more volume of air coming in, ala D-Dayve's post) The gas mass will remain the same.

Is it mathematically valid? Sure. If is correct, according to physics? You bet. Is it what is actually happening - NO. It's a mathematical manipulation of the actual events at hand.

The reason I have such a problem of this manipulation, is that you completely ignore the fact that the density of the incoming air/fuel charge is increased, and so the speed of the flame front is changed. This GREATLY effects MTBT, and is the #1 reason I dislike 95% of piggyback systems used on the 7M!

Jake, would you like to add anything else? I always love a good discussion!
 

IHI-RHC7

"The Boss"
Apr 1, 2005
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Good point!
But I do think that the density is taken into account on the basis that the mass incoming per cycle is always squeezed into .5 L for each cylinder. Thus if the mass flow rate increases (read freq for a karman sensor), the TCCS is going to know that the density has changed.

This works as long as everything is stock, which is why when you *trick* the TCCS to avoid fuel cut, you increase the timing and run the very real risk of detonating. I'm not sure if MAFT- pro addresses this for the supra yet, but I know for GN and DSM applications, you can not only monitor, but adjust timing advance to correct for airflow corrections. Messy, but effective if you know what you're doing.

I get what you're saying about mathematical manipulations and such, but to say that the turbo is pushing 6 liters of air into a 7m is a tad bit on the uhm... not right side of things for my liking. ;) A roots SC, sure, it doesn't make pressure, it moves air. In fact it could be adjusted to move exactly 6 liters of air into a 7m every cycle. And as you said, the result is 3 liters of air at 2 atm. But you and I know that turbos are much cooler and sexier and don't work like that.

Is there a better place to continue this discussion? I'm trying to keep it on cam timing, but there is just so much more meat to chew on the topic of extracting power while not extracting connecting rods from the side of your block...
 

JCFsupraman

New Member
May 12, 2005
132
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Cold North
A cams question - thanks in advance for your reply in layman's english.

I had the stock cams replaced with TODA 256's. Since they came used from Gord Duax they didn't come with a degree card. I found someone that knows about this kind of stuff and he worked on my car and dynoed a couple nights ago at DC Racing on a rear wheel roller dyno. 408.6 HP / 390.9 Torq. We were hoping for over 500. I have a stock bottom end and alot of mods that people in the know have told me should get me 450 hp +.

I dynoed in MI with Emanage blue and E01 with a Greddy TD-6 20g and put down 332.4 hp / 344.1 Torq on a wheels off dynapack in Royal Oak Oct. 24/06.

Two years later with Eman & E01 out for a Maft Pro and it did 363.5/353.9 on a rear wheel roller dyno at Victory Racing Oct.27/08 with a boost leak in the IC and a crack in the TD06 on the hot side so we replaced it with a GT4088 and patched the hole and street tuned it at EZ Autobody in Ruthven and the car pulled like a bat outta hell. It felt like a 450 hp + beast. But it was November and fairly cool out.

Since then due to a lil low end lag we put in a new GT35R and the TODA cams and ran 408.6/390.9. I was under the impression that the cams should add HP since Javi in Puerto Rico who put TODA 264's in his MK3 turbo added 57 hp and Zazzn with his 272 BC cams added over 80. The 40 increase in my case could be solely attributed to the boost leak being plugged since the hole was the size of a quarter.

Mind you the TODA cams are not yet degreed and are just TDC. I did notice the they moved the power band up 400 rpm from 5400 to 5800 for HP. A couple guys commented that with a stock bottom end and a bunch of bolt ons I should be happy with 408 hp. Well when some guys have put down over 600 and 700 with stock bottom ends why should I be happy with 400.

Would replacing the Maft Pro with an AEM EMS help?
What about a FFIM and FMIC?
Or would 720 injectors be the way to go?
Or should I build the bottom end?
I can't see degreeing the cams 4 degrees advanced on exhaust and 2 degrees retarded on intake as Javi did adding that much. Gord said to degree them to 114-115... which is Greek to me.

Well what do you think?
 

supramn21

New Member
May 2, 2010
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idaho
I have an pre 88.8 7mgte. Fully ported/polished, 5 angle valve grind, new o/s 1mm precision valves, BC Stage 2 cams, springs, and retainers; professionally installed and shimmed; drift motion 60-1 turbo with .70 ar, tubular ex. mani, 50mm wastegate, hks ssqv, full intercooler kit, aeromotive afpr kit, walbro 255, aem wideband, etc etc etc.... my issue is the cam timing. just got fidanza adj cam gears. dont have a cam degree wheel, wuz just going to leave them in stock position at TDC of #1 for reference once valve covers were back on. Which direction do i rotate the cam wheel to advance (clockwise or ccw?) ive read various things and everybodies runs different with sacrifice of power at some point in the rpm band. even just a baseline adv/ret to get the damn thing to idle semi good, not cook thru fuel like a helicopter, and have overall decent power band is all im looking for. not gonna take this to the track, just a weekend driver sorta play toy is it. anything helps. thanks.
 

BLACKCAT

New Member
May 24, 2007
185
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BHG
I have the BC stage 1 cams, same adjustable gears & found installing the cams at +3 exhaust & leaving the intake at 0 to be a good setting, but every engine is slightly different.
To advance the cams you rotate them in a clockwise direction.
Dont forget to reset your ignition timing if you alter the exhaust cam setting.
 

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