Updating Fuel System

blk92suprat

J Zizzle
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#1
This will be a branched thread off of my Methanol thread. http://www.supramania.com/forum/threads/methanol-injection.247767/

Quick backround:
7mgte
61mm turbo
hks vpc 550 chip
safc2
550cc injectors
walbro 255
adj. fpr base pressure 32 psi with vacuum.

Here is my dilemma leading me to think I may need bigger injectors and fuel pump.

Running 17 psi with meth/water with ambient temps of 80-90F I have to pull around 16-20% fuel with safc for 10.8-11.2 afr
Running 21 psi with water/meth with ambient temps 70F I have to pull 12-18% fuel with safc for 10.8-11.2 afr
Running 21 psi with water/meth with ambient temps 60F I have to pull 2-4% fuel with safc for 10.8-11.2 afr.

Going with this trend as ambient temps fall further into fall and winter, I wont have anymore fuel to add.

Here are my questions.

1. Why isnt the vpc making the necessary adjustments in relation to ambient temps?

2. Will 750cc injectors be ok with vpc with 550 chip. Based on research I can tune with safc and trim 25% and tune from there. I'm not sure how it will run on low throttle as I dont think safc can trim in low throttle.

3. upgrading walbro 255 to walbro 450. Is this a direct swap? Is this pump bigger in dimension? direct plug n play?

I appreciate all your input my fellow Supramania enthusiasts.
 
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JDMMA70

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#2
I had the same issue with my VPC, but it appears to have learned and ironed out the issues.

For question 1:
Is your IAT and MAP sensor working?

For question 2:
Yes you can run 750cc injectors with the 550 chip. Provided you adjusting the GAIN -16% (I believe this is the maximum the VPC can do) is sufficient.

For question 3:
The pump is physically bigger but I believe it fits.
 

blk92suprat

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#3
How can I verify if the IAT and MAP sensors are functioning properly?

Even if I have to manually tune safc for summer and winter tunes, does the leaning afr's with colder ambient temps (and inability to add additional fuel with safc) imply my injectors are running out of breath?
 

JDMMA70

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#4
The IAT is a basic thermocouple as far as I am aware and should be easy to test with a ohm meter and some cold water.

The Map sensor diagnostics can be found here on page 3. https://1jzmerc.com/files/hks-faq/hks-vpc-manual-installation.pdf

My understanding with the VPC is that the IAT should compensate for the change in air intake temperatures. Your injectors might be but it doesnt seem right. When is the last time you had them serviced and tested?
 

blk92suprat

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#5
Injectors were purchased probably 10 years ago. Had them out 8 months ago and put in new orings and grommets. Walbro fuel pump must be around 10 years too.

Time for replacements?
 

JDMMA70

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#6
If you have the opportunity have the injectors flow tested, as far as the pump is concerned, if youre holding good fuel pressure I wouldnt mess with it. As far as not being able to add more fuel, I find that a bit odd considering if everything is working, if you were to max out the SAFC and the Gain on the VPC your A/F would be in the 9s or well below it cold or hot.
 

blk92suprat

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#7
I have ordered a new vpc temp probe as well as ecu coolant probe. Lets see if this solves the issue.
The methanol may have damaged the vpc temp probe. Ill swap this one first and see what happens. If that is the issue I will have to change the location.
 

blk92suprat

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#9
Update:

I noticed coolant leak at the small bypass hose from water housing to block. Pulled the cps and water housing off. While I had these parts out, I replaced the hose, water housing gasket, thermostat, thermostat gasket and ecu coolant sensor. Still waiting on coolant gauge sender and plug as if broke upon removal. Also waiting for cps cover and gasket as it looked somewhat poor in one section.

I will see if the coolant ecu sensor solves the issue.
I have a spare vpc temp probe that I will swap after if problem persists.
 

blk92suprat

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#10
Well I got everything replaced but battery is now dead after sitting. I have a slow drain that I can't seem to locate. Charging it up over night and we'll see what happens tomorrow.
 
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