VPC acts as a FCD - HOW?

[87witmoreboost]

How does the VPC eliminate fuel cut? I assume it *raises* it, or else that would be quite dangerous. I know it uses a voltage MAP sensor and coverts it to a frequency signal similar to the stock AFM, but wouldn't that frequency signal still trip fuel cut at the 1400Hz (or whatever it is)? There must be a good definitive answer to this because if it truly eliminates FCO, it must tickle the ECU somewhere else in order to change fuel map so that operating under that 1400Hz at higher than stock boost levels results in proper fuel addition.

Along with this, how does the car properly map fuel after the stock FCO, where the map ends? I know that the FCON extends the stock map, so is this required to run past stock FCO when using the VPC?

I have done a lot of searching to try to answer this, but of course, "VPC" is one letter short of giving the best search results...

CALLING ALL VPC KNOW-IT-ALL's!

 

[drjonez]

VPC has a built in FCD.

I'm pretty sure I posted info on how the FCD works....

 

[87witmoreboost]

VPC has a built in FCD.

I'm pretty sure I posted info on how the FCD works....

I know the FCD tells the ECU to only see the max frequency before FCO for all volume flow at and over stock FCO frequency. The car continues to flow more air but the ECU doesn't add fuel accordingly.

Does this apply for the VPC as well? I assume that without FCON, the car will not know how to add fuel after stock FCO, but please enlighten me if I am wrong.

 

[drjonez]

I know the FCD tells the ECU to only see the max frequency before FCO for all volume flow at and over stock FCO frequency. The car continues to flow more air but the ECU doesn't add fuel accordingly.

No, the FCD doesn't do that.

Does this apply for the VPC as well? I assume that without FCON, the car will not know how to add fuel after stock FCO, but please enlighten me if I am wrong.

Turns out I'm a moron.....the FCD is not incorporated into the VPC.

 

[87witmoreboost]

No, the FCD doesn't do that.

Please explain as many threads have told me what I stated.

Turns out I'm a moron.....the FCD is not incorporated into the VPC.

I have read all over the place that the VPC does eliminate FCO. Are you sure?

 

[87witmoreboost]

Taken from HKS's site.

The HKS VPC is designed to physically and electronically replace OE air metering devices which present a significant restriction to the intake system and offer no adjustment or reprogramming options to take advantage of dramatically higher air flow or larger fuel injectors. The VPC converts both air flow meter and air mass sensor systems to what is referred to as speed density systems by utilizing a 16 bit central processing unit reading its own intake air temperature sensor and absolute pressure transducer (B-MAP sensor) signals. This unique conversion feature not only allows the VPC to replace the factory air flow metering device, but also eliminates the need for a fuel cut defencer. Another benefit of the VPC is the ability to create custom programs to take advantage of larger fuel injectors and new air flow characteristics, which may include larger turbos. In some specific instances, the VPC may be used in addition to the PFC F-Con and larger injectors for the ultimate in HKS plug-in fuel system technology.


So, anyone know how it does it?

 

[87witmoreboost]

Response to PM to a former VPC user:

Mark,

Now, for my old setup (MAFT Pro now), I used to run the FCON/VPC combo, but that made the car run extremely rich (safe, but rich). That was also with the HKS 550 cc injectors. Both computers had the HKS 550 chip in them as well. After a few years, I switched to a VPC/S-AFC II combo so I would have some more room for adjustment and that actually worked very well. I used the VPC for initial tune and then the S-AFC II for the fine tuning on the dyno.

That setup pretty much handled all the WOT tuning I needed and let the stock ECU handle low/mid throttle tuning.

Now with that said, my FCON had the FCD along with it and I never had a problem. When I went to just the VPC and S-AFC II, I still wasn't hitting fuel cut even with boost pressure up to 25 psi. This leads me to believe that the VPC does eliminate fuel cut. I didn't build it and I don't understand all of what it does, but that was my experience.

As for the chip, I would just stick with the HKS chip for the VPC with your size injectors, if that is what you are asking. You can pop open the VPC case and it will have the ID on the chip and you can than call HKS to verify you have the one you need.

 

[Reign_Maker]

The one thing I loved about the VPC was the simplicity in tuning... I had the VPC and SAFC-II... I used the SAFC to clean up the VPC's signal, but never really touched the knobs until I was over 5500rpm... The VPC took care of 95% of the tune... Idle was super smooth too... I ran boost up to 24psi, and never experienced fuel cut... My problem was I ran out of fuel... I WISH that HKS has a larger chip... 550cc chips may have cut it 10 years ago, but I'd love for them to make a 750cc or higher chip for the VPC...

 

[87witmoreboost]

I WISH that HKS has a larger chip... 550cc chips may have cut it 10 years ago, but I'd love for them to make a 750cc or higher chip for the VPC...

I bet with some larger injectors and FPR adjustments you could make the VPC work. This of course eliminates a default setting the VPC offers for easy base tuning.

I am officially going VPC (stock injector chip) with SAFC. I have a Neo and it is out being repaired at Apexi for the karman problem. I could then use it but am considering just going with SAFCII and grabbing the $100 price difference for something else fun.

I had the Neo installed and the car would jump to high frequencies for no reason at high boost, causing fuel cut when it shouldn't have been there. Turns out it was a software issue for the early Neo's.

 

[crisp]

Just catching up on this discussion...

I'm running all manner of HKS stuff, including the ORIGINAL EVC, VPC, PFC-FCON, GCC, SBC, AND the FCD STILL! I don't know if the FCD is now "redundant" or "unnecessary", but it's still wired in. H3 trim hybrid in the CT-26 pushing about 16psi, and very clean all the way from idle through peak. Running the 550cc chip in VPC with 550cc injectors from HKS.

I love my setup... and am wondering just where the limits are with a stock exhaust manifold and a real efficient tune. I'm considering the SP61 trim at the moment...

VPC = FCD can be eliminated? I don't know... but mine's still connected.::shrug::

-crisp

 

[87witmoreboost]

Just catching up on this discussion...

I'm running all manner of HKS stuff, including the ORIGINAL EVC, VPC, PFC-FCON, GCC, SBC, AND the FCD STILL! I don't know if the FCD is now "redundant" or "unnecessary", but it's still wired in. H3 trim hybrid in the CT-26 pushing about 16psi, and very clean all the way from idle through peak. Running the 550cc chip in VPC with 550cc injectors from HKS.

I love my setup... and am wondering just where the limits are with a stock exhaust manifold and a real efficient tune. I'm considering the SP61 trim at the moment...

VPC = FCD can be eliminated? I don't know... but mine's still connected.::shrug::

-crisp

Your setup is my dream. Lucky for me, I usually get what I want because I can be persistent. I have the EVC2 and VPC waiting in my room for the car to come out of storage. I am trying to find a EVC1 so that I have the manual control on the front of the unit. I will likely wait for a good one on ebay and then sell my EVC2. I will also keep my eyes out for a SBC - there is one on there now I am throwing a bid on.

I also just bought an EAC-T from a member last week. I'm really excited since it's so rare. It'll run my Tokico Illuminas. I can see it there in your picture.

I also run the old HKS 4 button turbo timer. All I need now is a GCC, but I am waiting for a good one to run through eBay for the right price and I may be able to convince myself to go GCC over the SAFCII.

If all goes as planned, my dash should look like yours in a few months.

 

[crisp]

^^^ 87witmore...

I don't come across too many who even KNOW what the SBC is anymore! You'll want to be sure to get the TRIG button with that unit! I mounted mine up in the far left corner by the windshield, where my left hand (usually just below there, on the steering wheel) can deftly POP it in a quick, subtle motion and PEAK my boost to a max level for that pre-determined timer duration. Great theater when you are in the car with someone!:naughty:

I actually got mine BRAND NEW IN BOX... direct from an inside connection at HKS! It was MISPLACED in their racks, and someone dug it out for me just a couple years ago, complete with button!


...oh, yeah... btw, I have the COMPLETE HKS SUSPENSION package with the controller... AND an actual HKS BUILT A/T tranny, that I swapped out and need to slip back in some day! (Includes an Art Carr converter, too! YES!)


Good luck with your scores!


-crisp

 

[Bondango]

Please bare with me as i try to explain how i have understood the magic box to work....


The VPC ROM holds a lookup table referenced via RPM and Boost which is accessed by the VPC and sent to the stock ecu

The data in each cell of the table is a Karman Frequency value ....Just like the fuel map on a MAFTpro or MAPECU.

Hence the VPC merely mimics the stock AFM.

The Complete table values are either increased or decreased depending on the VPC Gain setting (the complete table can be increased by 10% or decreased by 10% depending on the Gain setting)

Individual data cell values maybe increased/decreased by the VPC depending on AIT value before being output to the stock ECU

Individual data cell values may be increased/decreased Depending on the TPS opening/closing rate. This is controlled via the reponse knob on the VPC and is used to eliminate Throttle Tip in/out problems

The look up table runs to 26psi (max voltage 5V from VPC pressure sensor)

Theory behind fuel cut:-
the KF Data held in the VPC rom, is scaled for the injectors in such away that the ECU never see's a frequency above fuel cut right up to the max table value at 26psi
Or, from 20-26psi the values are all the same i.e. a value just under stock fuel cut.
With out actually logging the data, or seeing what is in the ROM then its purely theory.

Marty 'Random as ever' Bondango.

 

[crisp]

Please bare with me as i try to explain how i have understood the magic box to work....


The VPC ROM holds a lookup table referenced via RPM and Boost which is accessed by the VPC and sent to the stock ecu

The data in each cell of the table is a Karman Frequency value ....Just like the fuel map on a MAFTpro or MAPECU.

Hence the VPC merely mimics the stock AFM.

The Complete table values are either increased or decreased depending on the VPC Gain setting (the complete table can be increased by 10% or decreased by 10% depending on the Gain setting)

Individual data cell values maybe increased/decreased by the VPC depending on AIT value before being output to the stock ECU

Individual data cell values may be increased/decreased Depending on the TPS opening/closing rate. This is controlled via the reponse knob on the VPC and is used to eliminate Throttle Tip in/out problems

The look up table runs to 26psi (max voltage 5V from VPC pressure sensor)

Theory behind fuel cut:-
the KF Data held in the VPC rom, is scaled for the injectors in such away that the ECU never see's a frequency above fuel cut right up to the max table value at 26psi
Or, from 20-26psi the values are all the same i.e. a value just under stock fuel cut.
With out actually logging the data, or seeing what is in the ROM then its purely theory.

Marty 'Random as ever' Bondango.

So it would seem the FCD IS redundant with the VPC? (Wonder how I ever missed that... and have NO issues with BOTH still running?)

Any thoughts on my situation?

BTW, highly appreciate the insights from all posts in here...


-crisp

 

[HKS_TRD]

Hi everyone

I used to run a VPC myself however I used it in tandem with a Mines ECU which had no fuel cut. I have however, sold my VPC to a friend who runs it on a stock ECU and his car leans out before it hits fuel cut.

I remember speaking to someone who used to run a VPC years ago and IIRC he said that if you crank the gain enough it will hit fuel cut at high boost, he used to run 2 bar, his name was Alan Jordan IIRC.

My guess is the VPC delays fuel cut purely based on the software and output signals it delivers, so in a sense does the same thing as a fuel cut defender. Another point to consider, is that the VPC dummies the air intake signal to the stock ECU, I forget if it dummied a hot or cold inltet temp signal and hence locked the ecu into a relaxed or aggressive timing map, and also this parameter may have implications on where the fuel cut is

Also, I managed to run 720s with my VPC, with the HKS cams too, which required some devious tuning with the S-AFC. Reg Reimer can program a chip to work with 720s, but to be honest, I would not go that way, as when you pull the Kv signals back so much it ruins the timing curve of the stock ECU. Far better to find something which modifies the ECU injector signals a la Greddy e-Manage to achieve a tune for 720s, or go standalone.

 

[Bondango]

So it would seem the FCD IS redundant with the VPC? (Wonder how I ever missed that... and have NO issues with BOTH still running?)

Any thoughts on my situation?

BTW, highly appreciate the insights from all posts in here...


-crisp

I used to run a VPC with 680cc injectors, used the gain to remove as much fuel as possible fuel before tuning with an safc. ITC trying to control timing, and ran 23-25psi with no fuel cut.
Have always advised against using an FCD in conjunction with the VPC as you dont know what effect this is having on the VPC signal.


As said above, Reg is the only person i know who was able to custom VPC roms using the techtom, he would know what data is held in rom and more importantly were. I know its old technology, but with the right info and tools, flashing a custom rom based on injector size shouldnt be a big problem.

 

[crisp]

Dude, another great insight. I still have OOOOLD HKS literature on stuff, but lots of what comes up in here goes so much deeper.

...btw, hks_trd, I just noticed... your username descriptor seems to mean "healing by death"...:: alky ::


-crisp

 

[87witmoreboost]

Awesome stuff. Great thread.

Bondango, it makes sense what you say, but I don't understand how it can tell my ECU how to pulse the injectors for boosts beyond stock FCO without lack of fuel. I would think that at, say, 18psi, the car needs correlating fuel. Since the VPC sends out a Karman Frequency, it would need a frequency that tells the ECU to add that much fuel. In a nut shell, the ECU still lies between the VPC and injectors, so how would it give the right input to allow a safe output (not lean).

If the VPC was between the ECU and injectors, it would make more sense...

 

[Bondango]

Awesome stuff. Great thread.

Bondango, it makes sense what you say, but I don't understand how it can tell my ECU how to pulse the injectors for boosts beyond stock FCO without lack of fuel. I would think that at, say, 18psi, the car needs correlating fuel. Since the VPC sends out a Karman Frequency, it would need a frequency that tells the ECU to add that much fuel. In a nut shell, the ECU still lies between the VPC and injectors, so how would it give the right input to allow a safe output (not lean).

If the VPC was between the ECU and injectors, it would make more sense...

The VPC merely reproduces an AFM signal, the stock ECU controls the injectors like it normally would. The difference being the stock ecu will never see a Signal from the VPC above fuel cut (apart from reasons mentioned above)
Depending on the ROM fitted, the signal is scaled to the injectors (i.e. reduce the stock signal by 20% removes 20% fuel raises fuel cut 20%)

As fuel cut is removed its up to the Tuner to make sure the car isnt running lean at X amount of boost.

 

[HKS_TRD]

I think what he was getting at was how will the VPC allow you to achieve larger injector pulsewidths than when you run a FCD.

Sure the fuel cut off point is no longer at the same boost level (though fuel cut is apparently really set at a certain injector duty) but the amount of fuel the system will be able to deliver for a given injector size is still ultimately governed by the ECU, the VPC cant change this.

To note: the FCON alters the injector signals to achieve injector duties greater than what the stock ECU will generate