Need some help with VPC and Wideband

[andymac40330]

Ok so I finally get everything hooked up, double checked and replaced my 3rd never start wal-mart battery. I calibrated my LC-1 and got ready to start my first tuning adventure. When I started the car it was running around 12.xx at idle and felt and sounded good. As it warmed up it slowly became more rich down to around 10.xx when I shut if off. While it was running really rich, i attempted to click the vpc idle knob slowly more towards lean. I eventually got it all the way to full lean and it wasn't moving the afr much if any. I am running 660 injectors on the 550 chip but I should still be able to lean it out right?

Also in the install guide I was using, (its on the yahoo vpc groups page, I don't think it will link unless your a member), it stated that on some vpc harnesses it will have a gray instead of blue wire. I had to hardwire this in due to lack of funding and when I got ready to install it, it had BOTH blue and gray. In the instructions that I was reading on the yahoo group page it said it will have either but both do the same thing. I installed the blue one and taped the gray to a brown (which was also mentioned but not explained as to how/if you install it). If you have any information on these other two mysterious wires that would be great. My car has been down for about a year and a half and it would be a blessing to get it up and running again this week, since all of the install work is finished.

 

[toofast82]

While it was running really rich, i attempted to click the vpc idle knob slowly more towards lean. I eventually got it all the way to full lean and it wasn't moving the afr much if any. I am running 660 injectors on the 550 chip but I should still be able to lean it out right?

I've never tuned with the VPC, but 650cc are roughly 16% larger than 550s, so naturally its gonna run rich all the way around. Now if the VPC has enough adjustment to compensate this is what I don't know because i've never used one

 

[andymac40330]

Yea, I knew it would be a little on the rich side when I first started it but I figured i would be able to lean it out. On the manual I found online it looks like all the way to lean would be roughly 16%. How long should it take to make the change, like from the time I click the vpc until the wideband gauge will show the effect?

I just didn't know why it was doing pretty good when I first started it and then it slowly degraded to almost full rich? I'm also hoping I got all the wiring right, I don't want to have to spend another night with a hat light soldering and shrink wrapping.

 

[pboglio]

Your using a 20% larger injector then the chip calls out for and the VPC can only lean the A/F at idle about 14%. This is your problem. The GCC can adjust the VPC another +16% and -12%.

 

[andymac40330]

So should I put the vpc to full lean and then just continue on with the gcc for my tuning as long as the wideband readings look ok? Should I adjust the gain knob to lean as well or will that need to be set while driving and looking at the trims? Also do you have any info on that wiring question?

 

[andymac40330]

I just tried it again with the vpc on full lean and the gcc leaning out little by little. It started back at 12.xx again and with the gcc I was able to lean it out to almost 14.7 but then it slowly started to go rich again until it went full rich. I think I have something wired in wrong or something. It acts like the changes I make are working for about 3 min. and then it just pegs rich and runs like garbage.

 

[andymac40330]

Well while searching the world wide intrawebs, I came across a site showing the hardwire install on a supra and they seem to lean more towards using the gray wire for airflow sensor input and leaving the blue out. This is where I may be confused, because I have the blue wired in for airflow and the gray out (as per the 1g install guide). This is really confusing me.

 

[pboglio]

A walbro 255 with an adjustable FPR. What is your fuel pressure at idle/vacuum. Might try to turn down your fuel pressure and richen the WOT curve backup to compensate.
I can check the dip-switch settings inside the VPC since other makes have those switches set at different positions. On the weekend I'll take a look at the harness and take a few pics. You do have the intake temperature sensor wired in right?

 

[andymac40330]

My base fuel pressure sets at 43.5 lbs. at idle with the hose removed. When we first installed it, my dad was adjusting it under the hood while I was in the car and it started around 35 psi at idle and as he started to turn up the pressure to stock it ran worse and worse. I just assumed that I would be able to tune for the larger injectors with the fuel pressure stock.

 

[pboglio]

Here is the VPC internal dip switch settings:

 

[pboglio]

For the visually challenged

 

[andymac40330]

That's how mine looks on the inside. I'll have to fix the oil leak on the turbo and then drive it around and try to play with it while driving. It won't hurt it to drive it with it untuned while I'm setting it up will it? I won't get into boost or anything, just try to get my gain knob ball parked so I can move onto the gcc to fine tune everything.

 

[andymac40330]

I still haven't got it quite figured out yet. I was able to pull some trouble codes off today. I think they were a p0100, p0125, and p0130. I don't know if those would be caused by the vpc or not allowing the vpc to work but if anybody has any more suggestions that would be great. As soon as this rain subsides I'll be checking the IAC and TPS hopefully.

 

[andymac40330]

Ok so here's what I've found so far. The trouble codes are actually p135, p120, and p100. I checked the tps with my logger and its at 0 no matter what, it won't move. Could this be causing the condition and if so is it hard to replace a tps? Thanks alot for all your help so far.

 

[pboglio]

I think we talked before about this. TPS is used by the ECU for providing accel/decel fuel enrichment/decrement if my memory serves. The VPC needs this to work badly, as the VPC always did have a problem in this area even with a properly functioning TPS. This and a very good vacuum signal from the intake manifold are critical to getting the VPC to run properly.

The TPS is easy to replace if you can get the lower screw loosened, but it can be done without pulling the throttlebody. I've personally never seen one fail but just merely adjusting it has a pretty good affect on throttle response.

From my logs, the VPC only clamps intake air temp at 69*F I think or something thereabouts and airflow per rev when that value hits something like 2.4 g/rev. Otherwise your TPS should be reporting normally to the ECU/ECM even with the VPC in the loop.

 

[andymac40330]

So do you think its needs to be replaced or just adjusted? It isn't giving a reading at all with the car on no matter what you do to it. In my mind (which is probably wrong) if the vpc is adjusting fuel for the rpm/tps readings and the tps readings are non existant, then as the air increases the fuel will remain the same and cause that condition I'm having where it goes full lean when the throttle is even touched a little. Does any of this sound right? I'm still new to tuning and trying to figure out how everything works.

 

[pboglio]

The car will always lean out when you hit the throttle initially, that's what the TPS helps with, fuel accel enrichment, same goes when you chop the throttle as well. The TPS also is a backup in case the MAF fails and it uses rpm, MDP sensor, and TPS for load sensing to sort of simulate a rough speed density system in that event. This is why you can still limp home if the MAF is unplugged. The service manual goes into detail on this point.

Without the TPS, you are removing one VERY big part of the VPC's load sensing capability, which also uses the MAP sensor, tach/rpm signal, and internal Volumetric efficiency tables as well to simulate a "fake" MAF signal back to the ECU/ECM. So in a sense, forget about fuel accel enrichment at initial throttle application, that is the least of your worries. The VPC really needs that TPS to sense engine load. Without it all it knows is rpms and boost, but the TPS still provides a sense of what the volumetric efficiency of the motor is, or the 3rd crucial variable. For example, my motor at 5000 rpms on 20 psi of boost and 40% throttle doesn't produce the same airflow as when I'm at 100% throttle, so the TPS signal is still very important to load sensing.

This could be your problem. I'd follow the service manual to check the TPS and replace it with a working one if necessary. I bet the majority of your leaning out problems go away after this.

 

[andymac40330]

Alright then man, thanks so much for your help thus far. If it doesn't work you'll probably hear back from me .

 

[andymac40330]

Alright guys, I just got done replacing the tps and still nothing. The tps reads 0 as well as the air flow reads 0. I don't know what to do, this is really frustrating me. Nothing changed as far as how the car reacted to throttle. If anybody has any more suggestions, i'd be more than willing to try about anything right now.

 

[b00stedAWD]

Is your VPC hardwired or are you using a harness? First off, disconnect all piggyback system to see if your tps is in working order. If it works then you know it's somewhere on the harness. Also, If you're using a GCC with VPC then you shouldn't have to solder any wires since it's a PnP unit.

 

[andymac40330]

Ok, sorry to bring back an old thread, but with the same problem existing I was looking into possible causes of the tps reading being off and it appears that a bad ecu could be causing this? Would this also cause the other problems I'm having of seeing no airflow and the vpc not working correctly, or is that merely coincidental?

 

[b00stedAWD]

Hope this helps. Yellow wire and White wire are spliced with a wire coming off the vpc to ecu. That wire is grey which is airflow signal. You still need to provide more information for others to help you.

http://www.flickr.com/photos/39333613@N02/4116915398/

http://www.flickr.com/photos/39333613@N02/4116144185/

 

[andymac40330]

Ok, thanks for that info. Do you have any idea what the yellow and white wire are going to? Also, if the grey is in fact airflow, what is the blue used for (I was told the gray OR blue could be airflow, and with gray hooked up and no adjustments it idled like crap, which could be right with the chip setup 110cc's short of what injectors I'm running). Anyway, if you have any questions about my setup or anything that would help you better diagnose this, just ask and I'll do my best to answer it for you.

 

[b00stedAWD]

Yellow and white wire is input and output wire for airflow on my fuel controller (HKS AFR). I didn't use blue wire. Are you using HKS supplied harness or is your VPC hardwired to factory harness?

 

[andymac40330]

Its hardwired to the factory harness. I found a guide to hard wire one up to a 1g and I just matched it up to a 2g pinout, but I've heard conflicting stories as to which wires to use as the airflow output.