T_K

iTrader: (5)

I might be convinced that burn time is an overall better parameter than degrees, at least under open loop and WOT, where certain conditions are known.

djamps

iTrader: (1)

It's actually not that bad. I've got my timing where I want it within +/- 1 degree depending on weather/temps. But I did have to disable knock control on my race map to get it there.

T_K

iTrader: (5)

Is the cam timing table in camshaft degrees or crankshaft degrees?

djamps

iTrader: (1)

Pretty sure it's actual camshaft advance.

str8dum1

iTrader: (11)

it is cam shaft degrees.

T_K

iTrader: (5)

OK, after looking at this picture of a DE VTC, and the original info available about the modified Nismo units that can do 55 degrees vs. 40 degrees on the DE. Something isn't quite matching up. The unit above can only articulate 20 degrees.

Are the values in the cam timing table, half the actual cam advance?

T_K

iTrader: (5)

Ran the numbers through an engine dyno software, and the numbers for the stock intake cam advance are pretty spot on. Granted it is just simulation, but it's nice to be able to see the effects of advancing/retarding cams and how it moves the power curve. The numbers in the cam timing tables are double the actual camshaft degrees of advance.

For HR cars, IVT is damn near spot on from the factory. Wasn't able to generate any values in simulation that resulted in a better curve in the mid range.

EVT has very little effect on the power curve below 4000RPM, and also, messing with EVT values 3000rpm and below, might mess with cold start. For reasons unknown, the stock EVT doesn't retard further than 8 degrees(of cam) after 6000RPM. All literature and later simulation indicated that exhaust cam should run more retard above 6000RPM.

Stock tables are on the left, and modified tables are on the right. If anyone wants to try them out at a local track and see if trap speeds change at all. My local track is only a 1/8th so trap gains wouldn't be that noticeable. My car still has stock intakes and cats, but the simulations assume there's no intake restrictions.

djamps

iTrader: (1)

For what it's worth, additional IVT in the upper RPMs (>4krpm) helps with boost. No idea about EVT since I have a lowly non-rev DE.

tcode

iTrader: (7)

I found why had inconsistent AFR numbers. My ATI blower leaking lots of self containing oil into the intake and fouling MAF sensor. Sometimes more, sometimes less.

Got rebuild kit from http://www.superchargerrebuild.com/, do a complete rebuild with a friend of mine and everything went well except it leaks now even more . Original ATI output shaft seal isn't available at the market and this replacement one which is part of the rebuild kit isn't good enough. Especially if shaft is "eaten" at the part where seal "rides" on it, like mine. I'm in a process of repairing of the shaft and redesign of the shaft seal. But that's a completely different story .

T_K

iTrader: (5)

I just ran the non-revup through Dyno2000.

So, want to take a guess at why more IVT helps at higher RPM?

Nissan might have zero'd out the intake cam too soon. The full load, 6000rpm IVT cell should be "20", or actual 10 degrees of cam advance. It shouldn't retard any more than that for max power. You can mess with the gradients as you scale RPM down until you reach the cells that are already fully advanced. Pretty much from 4000rpm the value in the cell should be "20".

Nissan installed the stock intake cam so that the intake valve opens at 6 degrees ATDC and the exhaust cam closes at 8 degrees ATDC, so there's only 2 degrees of valve overlap at stock cam timing.

Every test I've done to generate max power, the two most sensitive parameters are intake valve open(IVO) and exhaust valve close(EVC). For any OEM VQ cam(duration, lift, operating range aren't that different), IVO wants to be at ~5 degrees BTDC, and with EVO timed so that theres around 20-30 degrees of overlap for peak power. For a non-revup, that places EVO around 15-25 degrees ATDC, but since it's a fixed at 8 degrees ATDC, you get about 12 degrees of overlap.

Not sure how it affects boosted cars, but getting the cam timing right increases VE, and in turn cylinder filling, so I don't see why it wouldn't also apply.

I should probably start a new cam timing thread, but those always seem to die with little or no interest.

balaguru

iTrader: (2)

Nice job, man. Please test your ideas on a chassis dyno or street dyno. Street dyno costs nothing but your time.

T_K

iTrader: (5)

They aren't "my ideas". There's nothing inherently new about cam timing and valve events. I already have a thread running in the HR section with the modified tables. At least one user has reported back with the gains being "plausible" based on AFR change in the region where the tables were modified.

I've also compared the predicted values with someone who had actually dyno tuned their cam timing. The timings were spot on. They were running a few degrees more intake advance than I had come up with, so I plugged in their values, lo-and-behold, the numbers were bigger in simulation as well. The misprediction was due to the increment size of 5 degrees I was using. Dynamic systems are represented with mathematical models all the time, and that's all this is.

I'm only posting results to go against the idea that Nissan got it right for the performance enthusiast. If you look at the FSM or cam card and see how the stock cams are degreed, it goes against conventional cam timing wisdom.

Cam tuning here is like a black art that no one talks about, and if someone does know something, they sure as hell aren't sharing. Dyno time is expensive, and to just punch in values into the cam table to find the best values by brute force, while effective, isn't exactly elegant or efficient.

I'm not asking you to run the values, but aren't you even the least bit curious?

T_K

iTrader: (5)

Here's an IVT table of non-revup, and the changes that should theoretically be made.

Epstein

iTrader: (5)

Since you already have your software setup, and maybe just for completeness (since you've already addressed HR and DE), can you run a revup setup through the simulation? Screen captures provided by someone else here: https://my350z.com/forum/8018677-post6.html

I've been doing some before/after logging recently for MAFS tube, 75mm TB, and HFC upgrades. People judging gains by AFR leaning out are doing it wrong. Again. There are plenty of loggable performance parameters to track real gains. BFS tracks torque almost exactly. Injector duty cycle tracks horsepower except if your AFR is changing, which is why you can also look at MAFS voltage (and do a VLOOKUP if you want to be super accurate). Anyways, I have some good logs for my current setup. It should have pretty low restrictions on both ends of the motor. I would be glad to run a map that you've modified and post some results. 7500rpm rev limit, please.

T_K

iTrader: (5)

Keep in mind that this in no way guarantees that it will make power, and that while it's been stated that playing with the valve timing is "safe" as far as clearances go on a stock motor, everything is at your own risk. Just in case that wasn't already implied.

Here's where the changes "should" be. Try not to mess with anything below 4000rpm. If the transition is a bit abrupt for comfort, always go down the table to smooth it out. I'm not sure exactly what the break point is, but messing with the table below ~4000 leads to very strange cold start behavior.

djamps

iTrader: (1)

I'll post my IVT map when I get a chance to fire up the old laptop but it's pretty much inline with T_K's findings. Took a dyno to get it dialed in and now instead of the 6k dropoff in power it now peaks around 7k like I've got aftermarket cams. Went from 114 to a 120mph quarter mile overnight.

balaguru

iTrader: (2)

I was talking about dyno numbers on the street from speed, gps and/or accelerometer data. It's essentially free. I have to plead ignorance on tuning cam timing. Not that far along on my tune. Still working on fuel and timing for my application. Perhaps simulation etc works better on engines but I'm a naturally skeptical guy and the systems I deal with have many more unknowns. I take nearly all of the stuff on here and in magazines with a grain of salt. Every once in a while grassroots motorsports will do some fair testing. Randomized controlled testing is the gold standard as far as I'm concerned.

My system is probably overly complicated but I generate SAE corrected hp/tq curves from UpRev data. Only finished the code recently. Will start playing with it soon.

T_K

iTrader: (5)

The software is pretty simple and is only really good for comparing cam timings, as that's the only change from run to run. The variable most obviously missing is rod length, as that would probably have the largest impact on actual timings. Otherwise, it produces a decent baseline for where to start.

XChacalX

iTrader: (7)

I beg to differ,
on a solid tune when I get a very stable AFR back to back then When I put the new CAM data, the AFR went leaner, meaning it was flowing more air into the engine by the CAMS allowing more air to be sucked up into the engine.

More air but equal fuel as before equal leaner condition.

the power might not be very big but it can defiantly make more power.
this how we tune cams on the street then confirm on the dyno.
not just with seeing AFR change ... MAF voltage and everything as you mentioned.

balaguru

iTrader: (2)

Why not just calculate HP on the street instead of measuring all these surrogates?