Growing up doesn't have to suck

[iamdub]

Do post your process. I believe I'll be needing that after seeing what my junk is reading.

You know I will!

 

[iamdub]

Not really testing the fuel at all. I just know that when I buy 89 and it is supposed to have no more than 10% ethanol and the Tech 2 shows that my truck has calculated it to be 25% - 35%, either the truck is reading wrong or the gas stations are really ripping people off. Not super scientific, I know, but that is the truth none the less.

Ah. Yeah, you don't need to test when that's going on. Fuels are strictly regulated so selling one with such a high alcohol content would be quite the offense. Never mind potentially damaging to non-Ethanol capable vehicles.

 

[gooffeyguy]

I don't see how it couldn't be the same. There's only one source of fuel in my Tahoe- the 26 gallon tank. The fuel is pressurized and piped through a 3/8" hose then leaked out of eight different points. Nowhere between the tank and those eight points is anything else introduced.

I sample at the rail because, in the tank, there's older fuel from a possibly different batch with a possibly different alcohol content than what's coming out of the pump at the most recent refueling. It mixes in the tank and is pumped to the fuel rail to be injected. Testing at the rail tells me what alcohol content the engine is getting with the old and new fuels mixed. I don't do it to know what is coming out of the pump. I already know that's not actually 85% Ethanol. I do it to know what my actual net alcohol content is to compare to my always-erroneous, as-calculated-by-the-PCM content is.

My post was being a little sarcastic.

Although I'd think a return less fuel system would/could have different grade fuel in the line at the engine than what's at the tank. Kind of like a garden hose that's on at the spigot but has a valve at the end and has been lying out in the sun. You go to get a drink and open that valve the first quart of water is going to be warm and not cold.

The first few minutes of driving after a fill up is still using the old fuel that's in the line and rails

 

[iamdub]

Kind of interesting when I look up the Denso 234 4668 that O'Reilly's shows a picture of it, and if you zoom in, it is the P-B664... I don't put a great deal of faith in what sellers post for pictures but it is curious just the same. Also, get your tinfoil hat ready... 4668 is kind of like B664, but BACKWARDS!!!... lol

LOL

I can see the clickbait headlines now: "This genius from northeast Florida is disrupting a million dollar industry with one weird revelation"

 

[iamdub]

My post was being a little sarcastic.

Although I'd think a return less fuel system would/could have different grade fuel in the line at the engine than what's at the tank. Kind of like a garden hose that's on at the spigot but has a valve at the end and has been lying out in the sun. You go to get a drink and open that valve the first quart of water is going to be warm and not cold.

The first few minutes of driving after a fill up is still using the old fuel that's in the line and rails

I kinda thought you were trolling me- it takes one to know one. But, I see what you're saying. I don't pull a sample while I still have that yellow nozzle stuck in the quarter panel. The sample I get from the rail is exactly the same as what's in the tank for the following reasons:

The E85 station is 22 miles away from home and I sample at home. That, alone, is burning more than a gallon of fuel which is more volume than the rails and all of the fuel lines combined.

I drive rather spiritedly so the fuel in the tank is actively mixed.

Also due to my driving style, the injectors see a lot of higher duty cycles so the "older" fuel in the rails is long burned up before I get back home.

I often don't sample until I'm nearly ready for the next refueling, so the current "blend" has had way more time and opportunities than necessary to mix and end up at the rails.


You've seen my posts and, more specifically, the ones in this thread. I'm way too anaŀ, scientific and OCD to be lackadaisical about this.

 

[gooffeyguy]

I see what you're saying. But I don't pull a sample while I still have that yellow nozzle stuck in the quarter panel. The sample I get from the rail is exactly the same as what's in the tank for the following reasons:

The E85 station is 22 miles away from home and I sample at home.

I drive rather spiritedly so the fuel in the tank is actively mixed.

Also due to my driving style, the injectors see a lot of higher duty cycles so the "older" fuel in the rails is long burned up before I get back home

I often don't sample until I'm nearly ready for the next refueling, so the current "blend" has had way more time and opportunities than necessary to mix and end up at the rails


You've seen my posts and, more specifically, the ones in this thread. I'm way too anaŀ, scientific and OCD to be lackadaisical about this.

No need to explain. The part about getting a sample was where I was joking and being sarcastic. I take my samples from the Schrader valve on the fuel rail also.

Just thinking a sensor at the fuel rail would give the engine a more accurate and quicker % to adjust it's tune to.

 

[iamdub]

No need to explain. The part about getting a sample was where I was joking and being sarcastic. I take my samples from the Schrader valve on the fuel rail also.

Just thinking a sensor at the fuel rail would give the engine a more accurate and quicker % to adjust it's tune to.

It's all good. The whimsical communication is lost being just text on a screen.

To still nerd out on the details: The system begins an alcohol content learning cycle after it detects a refueling event which I think is an addition of about three gallons. It continues the relearning for (I think) seven miles, barring interruptions. Between all of this, it's already getting the latest blend straight from the tank and once it has determined the alco %, it adjusts accordingly and has no reason to sample and adjust very frequently. No second-by-second update is needed. It's not like I'm refueling in the staging lanes. I'm sure it periodically samples and adjusts to account for degradation. IIRC, in any GM PCM since the 90s, time since it saw a refueling might be a factor for the spark tables so it can adjust for the reduced octane grading of aged fuel. Although, this may not apply to the LS era since they seem to rely so heavily on quick response to knock detection.

 

[iamdub]

Looked at my O2 sensors yesterday.

This is one of the 234-4668 sensors I ordered in 2020 for the front/upstream. I did crack it loose and turn it to see if there were any other numbers:




...And the rear/downstream. Probably original. I'm just using these as hole plugs since I have them deleted from the tune:








Interesting that it says "ACDelco" on it. A really brief search to see what the part number "12609457" cross-references to for Denso shows 234-4256.

 

[89Suburban]

Love watching a master at his craft you rock

 

[iamdub]

Slipped my light and phone up above the tank to see what the fuel supply QD situation looked like:




The alcohol sensor looks like this:




To not make any permanent modifications to the fuel system in case I need to revert, I'm thinking of making two adapter hoses out of Nylon or PTFE (whatever the factory "plastic" fuel line is made of). One will have a female QD on each end and the other will have a female QD and male QD. I'll mount the sensor in a reasonably accessible but safe location as close as possible to the "splice". The hoses will be in a loop formation with the sensor in the middle. Pretty much the exact idea that the kits use with the AN fittings locating the whole shebang alongside the left bank fuel rail. Or, if it'll be easier and just as clean, I might put the sensor near the firewall, splicing into the rail inlet. The wiring would be way easier and shorter with this option. I'll have to go pop the hood and stare for a while.