VPC and Cams

[Peter 92TSI]

Hey guys, first one to take advantage of the new forum. :D

Anway, recently I picked up a HKS VPC for really cheap with a 550CC chip luckily, and am really looking to finally ditch the automatic cams that I still have in my car. My powerband ends at 6000 rpm. :(

My only concern so far, is with using cams with the VPC. As people always say, since the cams create a low vaccum, the VPC decides to dump a lot of fuel, which causes stalling.

From talking to a few people, the AFC can be used to compensate for it, but where is the best place to tap it? RRE suggest in the MAP sensor signal, while everyone else suggest doing it in the VPC harness.

Right now I am looking at the Webcams, but seem to be undecide on what grind to get. Anyone have an suggestions? I am looking for a "decent" idle, but nice top end power. A lot of people I have talked to suggest a larger intake cam, than exhaust cam, but most vendors ell the opposite...

Thanks. All suggestions appreciated.
Peter

[Rdy2race]

I have a customer that we just installed a set of Web Cams street grind. The car sports a VPC, 550's and old school AFC. With the older one that is only one table and only +/- 30% would allow it to Idle but idle high. I said lets try the NEW S-AFC with 2 tables of control and +/- 50% it would give me more range to play with and allow a low table to control idle. Well we installed it and the car idled better but not as good as I would have liked. I looked deeper in to the combo and not at the computers but how the car was runnign as a whole. I saw that the BISSS was a bit off for my likeing and with Pocket Logger I was able to see that the ISC was not working the way I wanted. I HAD TO FIND OUT WHY!!. So we pressed on some more. The customer also had just bought the new Greddy Boost gauge that is a electric gauge so it has a mini computer that gets a signal from a MAP sensor. I ran 2 new taps on the back of the manifold for the VPC map sensor and the Boost gauge map sensor. With this done the hose to the VPC map sensor was no more then 6" long ( IF THAT!! ) and the boost gauge the same. Not 1 T tap on the whole car. The car now idles like this

750-760-750-760-750-760........and so on

never wants to stall starts right up and starts clean. No hard starts.

Now as for the way the AFC is worked in. I do not wire it like the way named above ( and the way the PDF from APEXi says to do it with a VPC ( on there web site ) The reason is that the VPC's fuel cure is not the best in the world. this is why a AFC is needed. By just faking out the VPC signal it was worthless ( IMHO ) B/C the VPC has fail safes built in to it. This is why the GCC isn't a popular mod amoung most.

if the AFC is BEFORE the VPC the VPC has the final word. this is not why you got a AFC, With a VPC/GCC combo you will see it works like this.

VPC gets input.
it feeds that to the GCC
you make corrections to the curve and the code goes back to the VPC liek a little voice saying in a weak little voice < think of pippen >
"More, can I have more please Sir????"
the VPC is left with the power of doing what it was told to or not. If this change to "to much" for the VPC or goes agenst the grain of the VPC's code then it won't do it.

SO!!! How to advoid this?? F THE VPC AND IT WACK THINKING!!! heheheh

Wire in the AFc as normial in to the POST VPC harness feeding the ECU an karman signal. The VPS is wired in to this and now the AFC has the final word!!! HA HA HA!!! <evil grin>

The AFC doesn't care if you take out 50% fuel across the board and blow the car up. The VPC will also take away to much fuel if asked but not as much as the AFC, with a VPC it takes some time to kill the car. it will be lean and enough to cause damage but not as fast as if you had a AFC to lean the sucker out more. With this said this shows that the VPC has fail safes in it's program to help advoid this. I didn't spend over $1000 in fuel computers to have fail safes put on me. If I want to blow it up thats my choise right =-) :cool:

So the AFC is wired in as normial and this will read just like there is no VPC B/C in the ECU's mind the MAS is still there, it's getting a MAS signal so whats the difference?? Right. The AFC is set to Karman and the rest of the setting are as normial. it's works like normial..

With the car set like this and WEB cams I have 40% fuel taken out at 1K RPM's on the low table and high so that the correction won't effect the setting of the idle table and your not in a high throtal % around 1K RPM and if you are then you need a driving school =-)

So this should help. It's a lot of fun to play with it and see what it does but remember that when this is installed and urunning the first thing to do is reset the idel so that your ISC is int he middle and that your not masking a problem with the AFC settings.

The joys of it all :D
BM-

[dsm4eva]

I'm running a VPC with HKS 264s with NO AFC on my street car. It idles like a champ. I've played with the timing, I think the exhaust is advanced/retarded 1 tooth, I'd have to pull the cover to be for sure (I did 60 runs @ the track to nail down the ideal timing with 94 octane pump gas while adjusting the timing). Anyway, with a solid motor, no intake leaks and the shortest possible hose lengths feeding the pressure sender, you can get away with the VPC with cams, even high duration cams.

[Rdy2race]

The proble with Idle and A VPC has never been with HKS cams and HKS's VOPC. The Web cams ( street grind ) have a MUCH larger intake cam lowering the vac. to the point the VPC thinks that the car is starting to get TPS input and adds fuel . The 264/264 combo will not have a huge effect on this but with the web cams comign in at 272 intake and 256 ehxt the large intake cam drops it so much that the VPC doesn't know what to do with this low vac B/C even with 272/272 HKS combo the car idles OK Because of the combo of the cams where a grind in web's cams larger the the " street Grind" is even bigger on the intake side. the HKS cams are geared to SICK top end where the WEB's are more of a mid track and top end cam. maybe not as big od a top end as the 272/272 HKS cams are but more down low means that you get to the gains on top faster then if thre were only huge gains on top.

In short the idle prob was never with HKS products ( this is also why the HKS SQBOV is vented B/C if you use one part of HKS set up that they expect that you using all there stuff, so a vented BOV on a DSM is fine with a VPC. ( get the thinking? ) Web cams are the one ones that idle like crap with a VPC all alone, i can not speak for crowler cams as I have not yet seen a set personally on a VPC car.

BM-

[dsm4eva]

My Dad's car with the HKS 272 and my friend's car with the 272 both idle like crap. My Dad's is more likely due to the fact he's not running an AFC/GCC and he has adjustable cam gears and we've done some modification to the timing. My friend's is more of a mystery, its a slightly tired engine, but other than that, it should not idle as bad as it is.

Personally, I've reviewed both HKS, Web, and Crower profiles, and I wouldn't buy either HKS or Web. HKS cause they're too expensive, not as much lift, etc etc. Web due to the fact that they have a VERY shallow ramp angle, which I REALLY don't like, oh that and the semi-recent quality issues that sprung up.

[Rdy2race]

do you know or any body have spec's on the new crowler cams? What grinds are offered?
From what I am hearing they are even more agressive then the WEB's I don't think that the ramp angle should be that bad if the combo has heavy springs in it.

What don't you like about the ramp angle on the Web cams? I always like to hear others info =-)

As for the quility thing this to my knowlage has been taken care of but you should always be checking the cams before and after install since the head is not "new" you want to know if there is any damage to the cams before the whole motors suffers a blow =-)

I have heard a lot of hype about the crowler cams but no rock solid info on it.

Like the normal cam specs and if they have been dyno tested V's any other cams. And I have always asked to see a car with a HKS combo put on a dyno and then swapped out to Web cams to see the 2 cams on one car would show a lot about the cams an the reaction to the combo. it showsa more here then any place. Numbers are great but figures that are in the real world can always be different :cool:

[dsm4eva]

Empirical evidence is hard to dispute, this is true.

Kevin Kwiatkowski (The fast FWD AT guy) has a custom Crower grind. We discussed our mutual dislike of the Web's ramp angle at length. As you know, the Bernoulli principle is our best friend to expedite gas in and out of the combustion chamber. Basically, as the valve opens velocities are very high since the gas pressure is higher on one side of the valve or the other. A shallow ramp angle decreases the gas velocity, decreases effective open duration by several degrees (this is the biggest penalty), and you also stand a better chance of floating valves at well.. very high RPMs, due to the hysterisis of the system from accelerating a mass very quickly vs. giving it an acceleration several cam degrees earlier. The Crowers seem to have the best figures all the way around, and should I need a new set (and I do, probably next season), I will most likely invest in a custom grind Crower setup.

I had the Crower site bookmarked sometime ago, but deleted it. They list the basic stats on the website. I have not been privvy to the full extent of the data I would like to know before I personally make a purchase... yet. :)

[4G63Rydah]

I've searched around and I've found some links to the specs sheets for some of the cams:

Crower Cams (http://www.crower.com/mitsu.shtml)
Web Cams Street Grind (http://www.roadraceengineering.com/eclipsetech/webcams-546-547specsheet.jpg)
Web Cam Website (http://www.webcaminc.com/mitsubishi.html)

I couldn't find a link to any sites with specs on the HKS cams but we all pretty much know the basics....

Intake is 10.3mm lift or .406" for both 264 and 272 degrees
Exhaust is 9.8mm lift or .386" for both 264 and 272 degrees

[Peter 92TSI]

Cool thanks guys. A lot of great info.

The only reason I am leaning towards the webcams myself at the moment is the price. :) Call me cheap, but people I have talked seem pretty happy with them thus far.

The only concern I have is after seeing a few people, have the lobes on their webcams flatten and round off over time. Not nice. :( Some people speculate, that you really need to break in the cams, but letting the car idle for a while, with regular dino oil, and not syntheic. Is there any truth to that?

But speaking about the Crower Cams, on the website all the durations they list seem awfully short? Am I missing something?

Peter

[Peter 92TSI]

Alright, well now that I selected both of my parts, I need a bit of advice on the installation.

For the VPC, I know how to install the unit itself, but are there any vaccum lines that I need to remove off of the throttle body or anywhere?

And for the Webcams, I have heard that people zip tie the cam gears to the timing belt, to pervent the timing belt from jumping any, and then they simply remove the cams. Do I need to readjust the tension on the timing belt after I install the new cams again?

Thanks
Peter

[dsm4eva]

I would take the time and reroute the vacuum lines that attach to the plenum (or tap a new port into the plenum), such that the VPC has a dedicated port. I ran into some odd idle issues when the VPC was sharing the same port as the FPR. Other than that, there is literally nothing else you need to worry about on the vacuum side of the equation, as for the t-belt however, I would take the extra 30-45 mins to take the t-belt cover off and make sure the tension is set correctly. I'd personally hate to have my engine jump time cause I thought it would be ok, just call me nervous. Oh, and don't forget to cut those zip ties off...