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

J Zizzle
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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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blk92suprat

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#13
Sorry for the delay, I have been so busy these days Supra was on the back burner for weeks.

So after I replaced the coolant bypass hose and ecu coolant probe the problem continued.
I then with new hks temp sensor, plugged my iat port and drilled and tapped a few inches further from methanol nozzle. Was 2 inches apart and now is 8 inches apart. And now idle a/f is back to normal.
So I am confident the vpc iat was shot due to the meth nozzle being too close.

Then I went to burp the coolant system since I had the water housing off when replacing hoses. After 45 minutes idle temps fluctuate 94-102c up and down and I have continuous bubbles at the rad opening.
I have a bhg. The last time I drove was about 4-6 weeks ago when I had the weird A/f issue problem. It didn't seem to be a slow progressive leak but rather a sudden onset.

I ran a compression test and got 165-175 psi which is excellent. Rings and valves seem to be fine based on these results. Leak is definitely at the coolant jackets portion of head gasket.

I used an endoscope to view piston tops and cylinders 3,4,5 look clean which is probably due to the coolant cleaning while burning.

I replaced the OEM gasket at 85k with a felpro gasket. Now about 10 years later at 105k it has given up. Most of it's time was 14 psi on 61mm. Just recently was it bumped to 21psi on meth.

Im not sure if I will go with MLS or try the Ajusa gasket. Ajusa is composite center with metal on outsides.
I still plan to boost 21psi with meth.

I won't be removing the engine, just standard gasket swap in engine bay.
 
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JDMMA70

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#14
Did you try a leak down test? If the HG is blown it will push the compressed air through the cooling system and you'll visually be able to see the bubbles from it.

I see two possible options.

1. Use a a AJUSA or OEM Toyota gasket. I had an AJUSA on my engine when I bought my car from the original owners and was impressed with its construction,

2. Borrow or buy a lapping plate. Verify the block deck is true, remove the dowels, and lap the block. This will take about a day or two. Then use a MLS gasket of your choice. This can easily be done with the engine in the bay.
 

blk92suprat

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#15
I didn't perform a leak down test. However the bubbles at the rad cap while idling tells me what I need to know.

I was just happy to see the compression numbers as good as they were.

I have a 2 foot straight edge accurate to .002. Also going to try the 3m bristle, the white one which is soft to remove old gasket material without causing any type of valleys in cast iron.

We'll see what flatness we have with feeler gauges.

I have the Ajusa, just arrived.

Looks very good quality. Specs state acceptable flatness of .005.
I'm not sure what type of metal the Ajusa is, anyone know?

Curious if you ran elevated boost on your Ajusa?

This gasket is supposed to be the middle ground between composite and MLS.
Wonder if it will hold the elevated cylinder pressures longer then felpro with arps.
 

need new tires

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#21
You realize that removing load signal to adjust fuel pulse with by lowering the load table is adding timing by lowering where the load is on the timing map. You need either a new chip for the vpc or (preferably) a proper emu.
 

blk92suprat

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#22
You realize that removing load signal to adjust fuel pulse with by lowering the load table is adding timing by lowering where the load is on the timing map. You need either a new chip for the vpc or (preferably) a proper emu.
I'm not sure what you mean by removing load signal.