How to VCT tuning

[veeefour]

MAF sensors measure mass. The MAF reads a higher value on a low DA day than it does on a higher DA day.
Baro sensors, like MAP sensors, measure pressure.
Obviously in both cases you have temperature sensors.
Volume is a static given volume, like manifold, cylinder, or MAF tube(a function of the transfer).
Density is calculated by the ECU. Yes air density changes, the ECU does a damn good job keeping track of it or fueling would be all over the place, baro sensor or not.

FYI humidity has a very minimal effect on air density until like 130f*-140*f(55-60*C)(328-333*K), at which point you have other things robbing you of power to worry about. Kinda why they didn't even bother putting in a compensation table for it. So much for all your experience/wasted time.

Attachment 100785

No, MAF measures flow only never mass(actually measures volume). Take one apart you will understand. That heated element responds to temp changes, air can be dense cold or hot...

Humidity has an effect on density, especially on "blade style" MAF sensor. Temp has even grater effect on it.

You are spending too much time on reading patents online, you need some solder and grease on your hands.

"Volume is a static given volume"? - some type of English I'm not familiar with.

"Density is calculated by the ECU" - of course as mentioned, model is very good as long you keep it stock. Simple CAI and your model is already gone as there's no baro sensor.

[blackbolt22]

No, MAF measures flow only never mass(actually measures volume). Take one apart you will understand. That heated element responds to temp changes, air can be dense cold or hot...

Humidity has an effect on density, especially on "blade style" MAF sensor. Temp has even grater effect on it.

Volume is only one of the components. Density is the other. The sensor itself is most certainly impacted by air density. Mass = Volume x Density. As such, it's not a Volumetric Air Flow Meter, it's a Mass Air Flow Meter.

But if are going to tweak the cams and look for 1-2lb flow change then you should stop tuning those cars and try other profession.

I could not agree more. 1-2lbs isn't enough to show any definitive gains especially when you can do identical 'pulls' (or so you believe) and see that much in variance.

[superman07]

Can I get that link?

Can of worms is right.

I think it was actually Otto Vs CMCV/Atkinson, and I was looking for tuning improvements for fuel economy in most of those old discussions.
What do you mean by effective, whats the goal? Fuel mileage Late IVC. Power earlier IVC for more effective compression. I posted a link to a spreadsheet in one of these thread that tracked all four IVO, EVC, EVO, and IVC in a Bi-doughnut graph and showed how different angles effected compression and power stroke length.

IMRC/CMCV what ever you want to call them, only effect distribution of fuel ratio in the cylinder, so while the average AFR my be your 14.08 to 1, where the spark plug is should be richer, and further from the spark plug leaner, making the flame front change its speed in a predictable way as it travels. Usually beneficial for combustion stability with very low cylinder filling conditions. Regardless once the manifold pressure or VCT allows cylinder fills with a more dense charge, stability is just a side effect and CMCV become a restriction.
Great for reducing emissions and improving fuel economy as you can run at lower air and fuel mass in the cylinder that are still stable. You don't gain part throttle torque by using Atkinson like VCT strategy.

[murfie]

mass per time(MAF) divided by revolutions per time(RPM) gives you mass per revolution. Then using the static volume of a cylinder and half the number of cylinders you can get mass per cylinder(density) AKA air load. I'm not sure where in that your MAF measures a volume, with out knowing RPM or taking a static time frame from it.

static.PNG

MAF temp compensation table is less than 1% +/- in nearly all but extreme temperatures. Even then 2-3% at most.
There isn't a humidity compensation table as it would be an even smaller correction.
MAF sensors are very accurate, given a good transfer and placement in laminar air flow, which comes down to tube design. Outside of those two things, and dirt or physical damage, there is nothing about a MAF that you can say makes it inaccurate. Your trust in your calibration should be equivalent to how much you trust your MAF sensor. MAF goes up means more air in the cylinders, which usually means more power.

[murfie]

Can I get that link?

https://forum.hptuners.com/showthrea...-II-Cam-Angles

Post #3.

[veeefour]

mass per time(MAF) divided by revolutions per time(RPM) gives you mass per revolution. Then using the static volume of a cylinder and half the number of cylinders you can get mass per cylinder(density) AKA air load. I'm not sure where in that your MAF measures a volume, with out knowing RPM or taking a static time frame from it.

MAF temp compensation table is less than 1% +/- in nearly all but extreme temperatures. Even then 2-3% at most.

Do we agree to agree or to disagree? Like I said looking for 2lb is "thoopid" and if you are making 200hp that's your 1%...
I see a lot of people here posting: "look stupid human i made a cam tweak and gained 2lb on MAF, not I shall teach you how to tune your VCT" LMAO
I made like million dyno pulls with cams, cobra jets, blowers, turbos...when I see 20lb on maf I think something's up but I chose to ignore 2-4lb "fluctuations" completely.

You can ask Denso about "volume":

https://www.denso-am.eu/products/aut...how-they-work/

[engineermike]

Any guess as to why the gt500 wouldn?t take advantage of Atkinson timing? The gt350 does but it looks to me like the gt500 does not.

[murfie]

Not enough room for the supercharger package and flap actuators, those things are quite large. Then on top of that I think it would get tricky with the SC bypass sizing and control for when they are closed vs when they are open.
IMO either HPT is show BS numbers for the GT500, or ford spent all of about 5 minutes optimizing VCT on the engine.

[superman07]

Not enough room for the supercharger package and flap actuators, those things are quite large. Then on top of that I think it would get tricky with the SC bypass sizing and control for when they are closed vs when they are open.
IMO either HPT is show BS numbers for the GT500, or ford spent all of about 5 minutes optimizing VCT on the engine.

Which numbers do you question Murfie?

From what I could tell the Cams for the gt500 were similar to the gt350 and Ford performance cams with a bit more duration, maybe due to the improved head design. The angles specified in the mapped points / distance were obviously different than the OEM 350, but they rhymed with what Whipple used in its calibration for the 5.0 and 5.2.

third party guys are getting a lot more power from the gt500, but many are going to e-85 and improving timing. Obviously no-one shares their cam angles.

The fuel economy drive table has the same values for rpm across all loads, the fuel economy table seems to be a bit more granular. Perhaps in FED the car goes to higher load so quickly it doesn't matter?

[veeefour]

I've tried to tune IMRC with turbo, more than once - boost doesn't like those kind of flaps,chokes and pops randomly.

[engineermike]

I?ll just throw this out there but I don?t think IMRC/CMCV has much to do with Atkinson anyway.

But looking at cam timing the stock 2018 5.0 in the cruise region (0.3-0.35 load, 1500-2000 rpm) is around ivo 40 and evc 45. This is true whether using IMRC closed or open Mapped Points. The GT350 is similar. However, the GT500 is more like ivo 30 and evc 20. Why on earth wouldn?t they take advantage of Atkinson at light cruise loads? Part of me thinks staying closer to 0/0 reduces cam response time when transitioning to full load. Another part thinks the cams move so fast that this wouldn?t matter.

[engineermike]

FWIW the Ford 7.3 gas appears to use Atkinson cam timing but doesn?t look like it has imrc/cmcv.

[murfie]

Maybe in not understanding, did you just say an in block cam, pushed rod engine, that doesn't have TI-VCT, has Atkinson like cam timing?

What are the specs on that engines stock cam?

[veeefour]

the GT500 is more like ivo 30 and evc 20

I just made a custom tune with those angles and a mix of SD and torque model in my TT and the results are surprising to say the least.

[murfie]

Which numbers do you question Murfie?

From what I could tell the Cams for the gt500 were similar to the gt350 and Ford performance cams with a bit more duration, maybe due to the improved head design. The angles specified in the mapped points / distance were obviously different than the OEM 350, but they rhymed with what Whipple used in its calibration for the 5.0 and 5.2.

third party guys are getting a lot more power from the gt500, but many are going to e-85 and improving timing. Obviously no-one shares their cam angles.

The fuel economy drive table has the same values for rpm across all loads, the fuel economy table seems to be a bit more granular. Perhaps in FED the car goes to higher load so quickly it doesn't matter?

Maybe its just the file i'm looking at. It was the first one Eric posted.
It only uses fuel economy mode, drivability and OP have the same enable loads.
The enable for fuel economy doesnt look like they did any altitude testing at all.
OP and drivability look exactly the same 5 to -5 ivo, 15 to 25 EVC, the cams move in the general direction you would expect, but not refined at all for max power. Practically not using VCT at all once it sees any boost.
The fuel economy table looks like it was started, but above 4000 RPM was not touched. like they were just trying to get the car to drive around and rev a little.

Anyone got a stock read of a 2020 GT500 they want to share, not the one Eric posted?

[engineermike]

Maybe in not understanding, did you just say an in block cam, pushed rod engine, that doesn't have TI-VCT, has Atkinson like cam timing?

What are the specs on that engines stock cam?

The 7.3 has VCT, just not TIVCT. In the cruise region it appears to retard ?the? cam 40+ deg. The mustang does the same, but to both cams, if I?m understanding the Mapped Points and distances correctly. Retarding both intake and exhaust timing results in Atkinson cycle, right? Of course it doesn?t have quite the flexibility of TIVCT but looks like it can get most of the benefit at light loads. Heck, it looks like the 7.3 more effectively uses Atkinson than the GT500.

I don?t have the specs on the 7.3 gas stock cam.

[engineermike]

Something else interesting about the gt500 is the entire drivability distance table above 2500 rpm lands you exactly at OP cam timing regardless of load.

[superman07]

Could it be that they wanted the car to always be heavily weighted to 1 or 2 mapped points under load? Their strategy has much less blending than my original whipple. I will have to rethink it a bit but I ended up using the whipple mapped points, but simplifying the distance tables so they were more like the gt500. This improved part throttle acceleration, I also disabled mapped points that were intermittently blending, but not really in an area the cams will see. I didn’t want to have to fix the SD data for all 15 odd points.

The issue I see know is that my car stays in Fuel economy Into higher load, barely hits FED, then right to OP. Setting the load tables doesn’t seem to actually change much. I may need to adjust how quickly I am polling though, now that I think about it.

[engineermike]

I did notice that the gt500 basically just travels between two mapped points at wot. All in all it’s a much simpler cam timing algorithm than the base GT but also doesn’t take much advantage of Atkinson.

Also interesting on the gt500 is that the 2020 fuel mileage is much worse than the 2013-14 even though the engine is smaller, compression is higher, and has tivct.

[veeefour]

Also interesting on the gt500 is that the 2020 fuel mileage is much worse than the 2013-14 even though the engine is smaller, compression is higher, and has tivct.

Because it has a belt driven forced induction system - i bet is has like 80-100hp of parasitic losses.

This car should be equipped with a pair of turbos, superchargers are obsolete...and slow.