HKS VPC tuning guide?

[1stGenRocks]

well i bought a new car to replace my smashed one.
mod list is
my 20 over rebuild with stock style pistons and rods
Big 16G
Buscher street FMIC kit
HKS VPC
Apexi SAFC2
rewired supra pump
B&M AFPR
gus modded bov
11psi of boost until i get my mbc back from a friend who borrowed it

it runs ok right now but every once in awhile it surges, mostly at part throttle right on the edge of boost. theres also some hesitation if you floor the gas quickly. if you go wot slowly its fine. any help is good but im mostly looking for directions on what the different knobs do and how to tune it right.

BTW where should i hook the side nipple on a gus modded bov? or is it better to swap on a normal one? right now it flutters but that might just be from being vented and only running 11 psi of boost.

 

[1fastlaser]

well what are you vpc settings...normally response likes to be around 2-3 o clock and gain anywhere from 2-5 o clock.....gain is the whole rpm range so it does effect idle
Whats your afc settings
if your on stock injectors,i would run things alittle rich

I am also running a stock bov with that little mod.Is the blow off valve crushed at all,if it is thats probably why its surging,crushed with that mod sucks.Check to make sure the set screw is still in the spot its supose to be at.

 

[1stGenRocks]

oh sorry i forgot.

I also have 550 injectors.

my safc2 settings are
low throttle 30 high 80

low throttle trims are -20 at 1000 and 1600 from there up its at +5
Ill have to go check the high throttle settings but they are almost all in the positive range.

I know this isn't right for 550's but I'm worried about changing it until i get my logger working. the screwy thing is that it isnt really bad at wot its just part throttle that sucks. The NE poitns are at weird spots too but i can change those.

the VPC is completly zeroed out, all the knobs are pointing straight up. the last guy told him to leave it that way and tune with the safc.

the BOV isnt visably crushed but i think im going to swap on my regular one anyway.

 

[1fastlaser]

Ok well this is what i want you to do.

On your afc riching up the 1000 and 1600 rpm.I would put 1000 at -12 percent,and 1600 definatly at -5-6 that will fix the hesitation problem...also put the reponse off the vpc at 2 o clock and put the gain at 3 o clock...just write down where you had them and if you dont like them change them back...ive been playing around with vpcs and the vpc/afc setup for a good 5 years now.When you got your 1600 leaned out that much,my car would hesitate real bad when trying to go.So put those settings in,and turn the boost up to 18-20 and go tear someone a new ass.

 

[1stGenRocks]

k i borrowed a logger and other then some phantom knock i think im doing ok. ill try and figure out how to export some logs later.

right now my settings are
RPM, Low, Hi
1000, -12, -20
1600, -6, -20
2200, -20, -20
2800, -23, -23
3400, -20, -28
4000, -21, -29
4600, -20, -30
5200, -21, -32
5800, -22, -34
6400, -23, -34
7000, -23, -34
7600, -23, -34

with it set like this and driven for awhile my fuel trims shift to
FTRL 97.6
FTRM 100
FTRH 96.8

i did set the response and gain knobs like you suggested and its better. still not quite perfect but im getting there. most of the part throttle bucking is gone (i think it was from being way too rich) and now the only time it acts up is right before the bov releases so im just going to swap it tommorow.

 

[1fastlaser]

i would riching it up with those 550s in your afc high settings. -34 compinsation is what you would run for 650/680cc injectors and a stock ecu.I would go maybe 10 percent lean thats about it until you get on a wideband,especially if you crank the boost up.

part throttle vpc cars are weird,especially with the stocker bov.

 

[1stGenRocks]

k. how much boost do you think i can run with this setup? what all do you think could be causing my phantom knock. im pretty sure its not real knock since i cant feel it and it happens at different times. it jumps to 43 right away and drops the timing. i put on a new knock sensor when i swapped the motor. installed it with a little bit on silicone on the threads like ive always heard recomended. a friend of mine mentioned the knock board on the ecu, is there any way to test this?

and back to the first topic does anybody have a explanation of how each vpc dial affects the car?

 

[1fastlaser]

well first off make the afc high settings around -10-+5 that should take all the knock out,because im sure your running lean with it that leaned out with 550s.3500-8000 high setting should be -5-+5 anywhere around there

set the gain knock to 2-3 oclock and the response around the same

the first knob "response" is ofcourse for when you first initially hit the gas.

second knob "gain" is for the whole rpm range,from idle to where you shift or redline

third knob "idle" is your idle lean rich setting

fourth knob "opt out"thats not used and it only used for when you have a hks gcc hooked up to the vpc so leave that at 12 o clock

 

[1fastlaser]

you could run around 18-20 psi on pump gas

race gas 22-24ish....i had a 2g piston 6 boltvpc big 16g setup on 550s and thats exactly what i would run and the car was going low 12s trapping around 112 113.If i put time into really getting on a wideband it would have been alot better

 

[1stGenRocks]

oh another thing i noticed. the base fuel pressure (vac hose off) is set to about 44psi. should i lower this so i dont have to compensate so much on the afc and screw my timing? i know that with it higher i can theoreticly get more horsepower since i can get more fuel but everything has a downside.

about the 5-10% at wot thing. do you think i need to run it that rich? the dsm excel spreadsheet with the injector compensation stuff said 550's with 44 psi of fuel pressure should be about 24% to get back to stock a/f. i did richen the highs up a bit and it doesnt seem any faster or to have any less knock. i have driven cars that are actually knocking and this doesnt feel like that so i thinks its something rattling.

 

[1fastlaser]

Well are you on a 2g mas or a 1g.

I know from tuning my friends car on a wideband with 550s on a 14b,no front mount, stock fuel pressure regulator with a 190,on 20psi with the 2g mas we had it positive 5-8 on the high settings tuned to 11.2-11.6 a/f....now in your case with a front mount,big 16g on 20psi,but with the 1g mas it will probably be around the same,maybe maybe not....but better rich then lean.

i would also set your fuel pressure at 43psi since that is what those injectors are rated 550 at so 44psi is ok.I mean your low settings you could have -5 to -15 for the lows while driving to compinsate for the 550s.Im just going on basic stuff here,every cars different,but from the cars i messed with with basically the same stuff thats what we tuned around.Also check your timing and make sure its 5 degrees,and your running some bpr or br7es plugs gapped around .28

 

[1stGenRocks]

im on a vpc.
i think i found my knock problem. after i got it tuned a little better it was still knocking at random times. i swapped in another ecu and now its much better. now i just have to replace the intercooler pipe coupler that split and get new hoses for the mbc so it stops popping off.

 

[1fastlaser]

im on a vpc.
i think i found my knock problem. after i got it tuned a little better it was still knocking at random times. i swapped in another ecu and now its much better. now i just have to replace the intercooler pipe coupler that split and get new hoses for the mbc so it stops popping off.

thats right i forgot what this post was about for a second...yeah the ecu problem is a definate thing,had the same problem with that also,random knock,got a 91 eprom off a friend and the car ran 200% better

go get some t bolt clamps from www.extremepsi.com and some couplers,that should fix that problem right up...there right in langhorne....i dont know where your located from there

 

[1stGenRocks]

yea i have the tbolt clamps laying on my desk. gotta buy a new coupler but for today its time to break out the ductape it will probably still leak but it cant be as bad as having a huge hole. i need to drive this car everyday so.....

are the real silicone couplers that much better? everybody around here swears by napa tractor trailer radiator hose. its reinforced but its not silicone.

EDIT>>> i checked the extremepsi site and their couplers are only 3 inches long. the one i popped is freakin 5 inches long. anybody know where i can get silicone that long? im going to email extremepsi and see if they make them there and can leave one long for me.

 

[1fastlaser]

well if your blowing them off you need to flair the end of the pipe or get a bead of weld put around the end of the pipes...or you can even build a nice little ledge of jb weld....so the couplers stay on...there not better nore worse...that radiator hose works good

 

[jamsta227]

well you said you have been messing with the vpc for a while. im just wondering if you have a picture of a harness for one. it looks like someone had modded this harness and im trying to clean it up and not sure if he had it wired right. it had electrical tape all over it and wires sticking into one another. so i dont think its right. also are you good with the gcc addon? any info will greatly be appreciated. thanks.