They are using C4B tunes/Calibrations from the Holden GTS. These are MAFLESS Calibrations from GM. They run with O2 sensors and tune the VE table using LTFTs to zero in on the correct VE value at each load site. Very time consuming.
Robert they don't have to "loosen" with Edit - they change the calibration, VIN and look ups . These Guys are way ahead of us in manipulating the PCM (way over my head as I'm a NonTechie):yesnod:

Don't get me wrong....I'll be keeping my MAF. ;)


[Modified by binksZ06, 10:03 AM 3/1/2004]

 

wonder what kind of fuel they get down under? makes a difference how a motor runs!
:skep:

 

What I would like to know is how they are getting good manifold vacuum with low LSA cams.
Speed Density does not work worth a poopie without manifold proper vacuum.

In tuning my TPI big block I played hell getting the vacuum high enough to keep the engine out of the load portions of the fuel map.

 

The only time low Vac is occurs is at idle - not a problem with computer tuning (engine management) and standard trans. I don't know on an Auto tranny???

 

Mine is an automatic.

The TC is always loading the engine up a bit, so it lowers vacuum, as the engine is loaded, so yes it is worse on a automatic car.

The main benifit of the mass air system is that is another absolute that the ECM can use to determine proper control. I'm just confused why the australians are singing the praises of low LSA cams with speed density tuning.
Its counter-intuitive.

 

Sorry I was kidding about the air filtration it can be gritty in Australia from what I have seen I assumed there was a single unit that fit over the system i had a similar situation with a bank of webbers--but they sure look good when you raise the hood and see those venturi's sticking up--

 

Decent manifold vacuum is more a function of the relationship between when intake opens and when the exhaust closes and the resulting overlap. LSA is a product of this relationship and only in a offhand way relates to the amount manifold vacuum you will get.

Often idle quality can be improved by retardinging the cam a few degrees which does not change the LSA but puts the point at which the intake valve opens a few degrees later.


[Modified by SFVetteman, 6:50 PM 3/1/2004]

 

The idle qualities of some of the cars I have seen here is better than many of the smaller cam'd cars with wider LSAs back in the states. You can have a tighter LSA with a bigger lobe and have a better idle than a cam with a wider LSA provided that your Valve events are selected better than just using LSA as your target.

 

:iagree:
J-Rod - Many of the smaller cams would idle better with more intensive tuning ....with a MAF. I'm not knocking our tuners, or their methods, many of us want a little bit of lope/rumble. :yesnod:

I believe the most knowledgeable Tuner on MAFLESS around here (over on LS1Tech) is NoGo. He's investigated it thoroughly and tried it. He's not a Fan. FWIW.

 

The valve event thing is exactly what folks are trying to do by using wider LSAs. There is alot of "voodoo" involved in cam selection. You have to test dozens of grinds in your exact combination to find the best match scientifically.

Maybe the australians will teach us something by trying the untried.

 

I think most people get caugth up on LSA since it is more involved when you move off the 114-117 range. Some may think that if 112 is this much harder then 106-108 must be 10x as hard. Truth is 106-108 is probably not going to be any harder for tuning. The issue may simply be that it isn't 114-117 anymore and lower is lower.

 

A 106 is alot more difficult to tune. :yesnod: :yesnod:

 

One of the things they did here was build a a gear set to adjust cam timing, and a two piece timing cover. They ordered 30 cams from comp of various lobe size and LSA. They they played with advancing them and retarding them to come up with numbers. I saw the stack of cams on the floor. They did there testing on a Stutska water brake dyno with a data collection system, while also capturing all the engine data via OBDII.

They showed me one of there test scenarios. They recently tested headers and H/C cam packages. They did 147 dyno pulls testing all the various combos.

I can say from what I have seen these guys are fairly thorough in their testing methodology. Again, I drove a car with a 232/232 108 and it drove wonderfully.

 

232/232/108--that would be nice

 

There ain't no such thing as a free lunch, and there is no way to repeal the laws of physics.

When you get into really big durations, you almost have no choice but to go to a more narrow LSA.

What is a "wonderful" idle to some is a nightmare to others, especially in traffic. If these are race-only cams, then yeah baby. But for the street, I'm not buying.

 

No, you don't have too. Go look at a Pro Stock camshaft where you have far more duration, and might see a 117-120 LSA.

Maybe I'm not making my point about idle quite clear enough. UIf I need to capture video to make it clearer, I will. What I mean by a great idle is that the car idled at 875-900. There was a slight lope, but nothing obnoxious. I drove the car around on public streets and on the freeway and had far fewer issues with it than I have had on the street in the U.S. with smaller cams with more broad LSAs.

Here are some points to ponder from the cam thread

Due to runner length the current lack of cost effective shorter runner intakes, the LS1 is limited to a 4800rpm torque peak.... thus 6200-6400rpm HP peak (due to the wave of the incoming intake aircharge as it bonces between the closed intake valve & open air plenum). When I do a cam for a setup like this, I go for max cylinder pressure under 6200rpm.
The area most cam companies error on is the exhaust. This causes problems with these limited intake designs. The exhaust VE's are the most important on these setups.
Simply put, on an N/A motor the intake aircharge is not assisted. (leaving wave dynamics of the aircharge out for a moment).
After the combustion stroke there is tremendous pressure in the cylinder. As soon as the exhaust valve cracks open it flows a LOT of air. It's basically boosted out of the cylinder if you want to look at it like this. Having the exhaust valve open too early not only costs heat (power); velocity through the exhaust runners, it also empties the cylinder before the intake valve is open enough to take advantage of the pressure differential. (in a limited overlap/smogable camshaft this is especially true) This causes exhaust reversion is one of the key factors in surging problems. By the airflow reversing course it is loosing a lot of it's inertia. Typically this is overcome before peak torque however. So only low-speed issues are present. At the track these motors are always above 4500rpm so this does not affect track times too much. Stilll....there is significant power lost by allowing reversion. So it makes sense to open the exhaust valve a little later increase the overlap a bit. By adding advance into the camshaft this makes the problem even worse as now you're opening the exhaust a few more degrees earlier..... shortening the effectiveness of the intake unless you have significant overlap flow to over come this. Simply put, advancing a cam makes it more exhaust bias relative to TDC. Retarding a cam makes it more intake bias relative to TDC.

No, ther eis no free lunchj. But you'd be suprised at what happens when you design a cam around good valve events rather than a target LSA. If you pick a lobe, and proper valve events, you may end up with what folks will conder an impossible LSA. But guess what it runs better, idles better, and makes more power than the "de facto" LSA cams.

You're right you can't ignore physics. If you read up on wave dynamics you'll see that the problem we face is people ignoring the laws of physics. If you start playing nice with them, I think folks will make more power.

 

The cam grinds you describe may or may not be effective, but your explanation is gibberish.

Having the exhaust valve opening too early is not the problem, it's when it closes too late. Then both the intake and the exhaust valve are open simultaneously, and the intake charge runs right though the combustion chamber and out the exhaust. This is why big cams result in a choppy idle, lots of surge, and a stinky exhaust.

Even though you got the valve events backwards, your description of reversion is accurate. Low-speed issues are present, but at the track these motors are always above 4500 RPMs, so track times are not affected. Actually, the increased overlap actually helps cylinder scavenging at higher RPMs, as the inertia of the exhaust flow creates a negative pressure wave that helps pull the intake charge into the cylinder.

I repeat, if you're talking about a race-only cam, AND you have an intake that can flow big numbers at higher RPMs, then the big durations have their place. But NOT for the street.

 

No, you don't have too. Go look at a Pro Stock camshaft where you have far more duration, and might see a 117-120 LSA.

J-Rod - Could you point me to some info on the Pro Stock cams. I guess they run Huge, Asymmetrical lobes? What kind of overlap are we talking?? I'd like to read/educate myself a little.

Also, ...where is the VE spreadsheet? I thought it was in the Cam thread but I can't find it. Thank You!!! :D

 

If the exhaust valve open while you are still on thepower stroke yes it will cause a problem. Also in an NA engine there is not really as much of an issue with your intake charge running out the exhaust since the only thing pulling the intake charge while exhaust valve is open is the suction effect of the piston pushing the exhaust gasses out of the chamber. Most of the intake charge is loaded into the cylinder when the piston is moving down during the intake stroke.

On a boosted engine where you have +pressure anytime the intake valve is open then that is a different story.

 

Ramp Rates:
I'm not sure if this is what you are eluding to, but I would like to add its not just valve events either. Its also ramp rates. Cams with more agressive lobes (like Comp Cams XE-R lobes), approaching solids, will have less overlap, thus idle much better. So, its lobe design as well. If you compare a solid, aggressive and standard cam, you'll see for example a 106LSA, but the overlaps will all be very different. If we could get rid of the open and close phase prior to the 0.050" numbers, we would probably have some really fast setups with 18+" vacuum. Think about what electronically opening the valves on the fly will do for us. This will be better than a solid cam. No "advertised" cam area any longer. Hmm.


[Modified by 427CPE, 7:15 PM 3/2/2004]