HKS VPC

Quote:
I think the GCC is the problem, not the VPC. Everyone I've heard of running the VPC/GCC has had some problems with it.

John



The GCC is the problem. I experimented with both the GCC and an afc.

With the AFC you can correct any fuel issues...with the GCC you were out of luck.

 

i had a vpc/afc w/ keydiver chip and could never get the car to run well. I had 660cc injectors and with the vpc 550 chip and a kediver chip for the other 110cc i had to lean the idle out to 30% on the afc and to see 14 afr and no matter how rich i made it upto it would go lean. I changed nothing but pulling all that stuff out and adding a dsmlink and the car ran like a champ.....no idleing problems or wierd afr.
just my 2 cents

 

[4orced4door]

I've had two VPC setups, one with a GCC and one with an SAFC and both ran fine. No idling problems, but the one with the SAFC was a little hard to tune with, although that car had problems other than the VPC/SAFC. I think part of the problem people have is running VPC chips that don't match their injectors. Re-compensating with an SAFC or one of Jeff's chips just doesn't work as well as having the right VPC chip to begin with.

I think for a mild setup the VPC works well. You pick up a lot of horsepower on the butt dyno, and free up space under the hood by losing the MAS. I was happy with mine, just ready for something bigger and better.

 

[grocery_getter]

There are also some problem with the VPC harness because they are so old now. Some of the solder joint will crack and will make your VPC looses its barometer calibration.

 

[BadVr4]

vpc/afc with keydiver chip setup is a nice setup. I only upgraded to aem cause i finally got the money, I had dsm link for 2 months, and got rid of it, hate it and at the time i had to use a gm maft which is even more of a piece of sh*t. some ppl like the link, personally i would never use one ever again

 

[1gnasty]

just because u dont know how to used it don mean is bad

 

[atc250r]

Quote:
There are also some problem with the VPC harness because they are so old now. Some of the solder joint will crack and will make your VPC looses its barometer calibration.



Excellent point. When I put my VPC in I hardwired it and had Jeff make an ECU chip that locked all the values that would normally be done by the resistors in the VPC-ECU harness.

I wouldn't let the VPC do all the compensating with its chip because that has the same effect on your timing as pulling out a bunch of fuel with an SAFC. I have a Keydiver chip in my ECU that is compensating for a VPC with a 550 chip in it and 720cc injectors. It's pretty close but since its a speed density set up, anything that causes the vacuum to change (i.e. big cams) will throw off your tune. I had been pulling about 35% at idle with my 264's then when I went to 280's I needed to pull almost 50%. As I got off idle and into the 2000 rpm and up range, it quickly returned to a reasonable level on the SAFC. I've gone back to a 264 intake and 272 exhaust set up and the SAFC setting at 1000 rpm (idle) is back where it was before.

I looked pretty seriously into running the VPC with DSMlink but the problem is that at the end of the day you are still very limited by the VPC's MAP sensor since it maxes out around 25-27psi. If you want to run much more boost than that you need to just start adding fuel based solely on RPM's and throttle position. That probably works fine in a race car that is always going to be run on race fuel and high boost levels but doing that on a car that sees pump gas and lower boost makes it a pain in the ass.

John

 

The VPC as a tuning tool was/is well ahead of it's time. It works better on some cars than others, but is still good. As mentioned most of the problems people complain about with the VPC have little to do with the actual unit. HKS never designed a chip over 550 cc's,and the GCC is limited in it's adjustment range, but that can be compensated by using the SAFC.

I ordered my VPC with a 550 chip from directly from HKS and had both 550's and 720's on the car along with a GCC at various times. It was only until I put HKS 272 degree cams in the car did it start hunting at idle. After pulling the chip I realized that the chip was for the stock 450 cc injectors. For 3+ years the car ran and idled well with the wrong chip and bigger injectors and a unmolested factory ECU. The only reason I switched to my current AEM set up was because I didn't want another piggyback in my glove box, I got a great price on it and as Nate said, if the MAF is gone it's hard to go back to using MAF based system.

There are quite a few cars that made big HP numbers and set records using the VPC, and their are still Supra's making over 1000 HP using them.

Daryl

 

[BadVr4]

Quote:
Quote:
There are also some problem with the VPC harness because they are so old now. Some of the solder joint will crack and will make your VPC looses its barometer calibration.



Excellent point. When I put my VPC in I hardwired it and had Jeff make an ECU chip that locked all the values that would normally be done by the resistors in the VPC-ECU harness.

I wouldn't let the VPC do all the compensating with its chip because that has the same effect on your timing as pulling out a bunch of fuel with an SAFC. I have a Keydiver chip in my ECU that is compensating for a VPC with a 550 chip in it and 720cc injectors. It's pretty close but since its a speed density set up, anything that causes the vacuum to change (i.e. big cams) will throw off your tune. I had been pulling about 35% at idle with my 264's then when I went to 280's I needed to pull almost 50%. As I got off idle and into the 2000 rpm and up range, it quickly returned to a reasonable level on the SAFC. I've gone back to a 264 intake and 272 exhaust set up and the SAFC setting at 1000 rpm (idle) is back where it was before.

I looked pretty seriously into running the VPC with DSMlink but the problem is that at the end of the day you are still very limited by the VPC's MAP sensor since it maxes out around 25-27psi. If you want to run much more boost than that you need to just start adding fuel based solely on RPM's and throttle position. That probably works fine in a race car that is always going to be run on race fuel and high boost levels but doing that on a car that sees pump gas and lower boost makes it a pain in the ass.

John



good luck running 280's with a vpc, you must be changing your plugs everytime you start the car. Also, you can run more boost than 27psi with the vpc, they max out in the low 30 psi range

 

[atc250r]

I ran a single set of NGK 8's for the last year without fouling them once. The cams are only a problem if you can't pull enough fuel. With the keydiver chip that isn't a problem. As for the limit of the stock sensor, you're the first person I've had say it was more than 27psi.

John