How much weather effect fueling?

[BARRACUDA1968]

I have an SD2 chip and decided to take some time today to do some tuning.

I made a couple pulls about a month ago in 80 degree weather and my chip was pulling 10.2% of fuel out at around 4700 rpm spraying at 6. I haven't messed with the car much since then so I decided to do some tuning today. It's about 60 degree's right now. I made a couple runs this morning and now the chip is adding 15% fuel.

I'm racing next weekend at an 1/8th miles track so I wanted to be prepared.

Can 20 degrees of temp cause this much of a change or do I need to look for a problem?

 

[BARRACUDA1968]

Here's the log file.

BeataV8 if you're on take a look.

 

[BEATAV8]

That's way too much change for just the weather. I'll take a look.

 

[BEATAV8]

It looks to be working OK. Something must've changed to lean it out between then and now? -10.2% is the maximum it can pull out, so it was running even richer than that before. For it to be running +15% now is a tremendous change towards the lean. I would suspect first that the alky flow rate reduced, if confident that it did not, then start checking fuel pressure and fuel filter, stuff like that.

for a 20 degree ambient change, on my car I would expect to see maybe ~1% fueling change, tops.

 

[BARRACUDA1968]

Thank you. If you look at all my posts recently you'll find the logs I made at Bo's house a month ago. I'm wondering about alkyl pump.

 

[SCOOBY DOO]

I'm up here in Canada. The cool/dry air makes a huge difference. What was the humidity level at 80 degrees and 60 degrees.

 

[BARRACUDA1968]

This is the last log yesterday #25 and the portbyron log was a month ago. I increased fueling by 10% high boost to compensate for the lean condition on log 25. It's not adding as much fuel as before but I still have the major dip starting at 4600 rpm like before. I planed to get that fixed in the VE tables until I saw the first log in this thread. It went lean all of the sudden.

I'll check fuel pressure this week, using a Red's XP pump. Fuel filter is almost new but will throw a new one on for good measure.

I did just check my fuel line at the regulator and I put about a 1/2 turn on it. No sign of a leak there and it was holding pressure so probably not the cause.

I have a spare pump from Julio on the shelf. 2 years ago I decided to keep a spare so I bought a new one. It lasted 3 weeks and started to leak so I sent it back and put the old pump back on. Got the new one back from Julio and it wouldn't even turn on so I pulled it again and put the old one back on. My car has been down so many times in the last year or so I never got back to the new pump. Julio has some way for me to get it fired up but I've never tried it. I almost don't trust that new pump now. I better see if I can get it fired up and try it out.

 

[BEATAV8]

Looking at the 2 runs side by side at the same engine speed and vehicle speed, you weren't quite as far off or different as you thought you were. Less than 10% delta, and the one on the right has a little smidge of extra boost that you can see it eeking out there on the big end. Adding the fuel was the right thing to do, you'll get it much closer when you start working on the VE.

 

[BEATAV8]

When you get into the VE table you can make the AFR look like a table top without using any closed loop correction.

this one here needed just a little less VE around 5400 and below. You can see it step up right there.

 

[Mr.Spool]

I'm wondering about alkyl pump.

I have found having fp gauges on the rail and for the meth to be a major asset,guessing if the fuel is going to be there leads to very expensive problems

 

[BARRACUDA1968]

Thanks for the help so far. How do you post those snap shots? I'd like to post one in comparison after I added 10% fuel. That's the last log in this thread. I'd like to see a comparison between quick run 25 and quick run sunday.

I have not touched to VE tables yet, that was my plan for Sunday until I thought I saw a lot of variance in the correction. 10% seems like a lot.

I'd like to have pressure gauges for everything but I don't want gauges on the hood and I don't like a cluttered interior. That's one major reason I went with an SD2. A little more insurance if something goes wrong and some correction when needed.

I had a turbo seal leaking oil for a while until I caught it. It's fixed now but I'm wondering if the oil in the downpipe may have an effect on the 02 sensor? Should I get a new one?

I'm going to run it 1/8th miles this weekend if my fuel pressure checks out. I'm going to test that tomorrow night and if all good I'll swap in the new alky pump and make a log.

I had one other thought today and I forgot to check it before I left work. I can't look at logs at home. When does my volt booster come in on the pull and do you see that having an effect on my tune? I'm assuming it spins the alky pump quicker? Julio told me to unhook it and others told me to leave it hooked up. It is now hooked up. Just a thought to consider.

 

[we4Mateo]

Good call on the oil on the O2. Worth a look. The volt booster does exactly what it's intended and designed to do but you will definitely need to factor that into your tune. Both fuel pumps, alky and gas, will run harder when the booster hits and deliver more volume.

 

[BARRACUDA1968]

I own a car dealership and we hardly if ever replace 02 sensors. They seem pretty durable. Generally an 02 code is the cause of another issue but mine did get coated in oil. Definitely worth a look.

 

[SCOOBY DOO]

02 sensors are cheap. CC's are a dead giveaway for a failing/dead 02 sensor. BLM's suddenly going out of whack is another sign.

 

[BEATAV8]

You can open as many instances of PLC as you want. Handy for comparing. These screen dumps are just "print screen" pasted into ms paint.
the volt booster is kicking in when expected.
before 10% and after 10%:

 

[BEATAV8]

Fuel pressure transducer would be a good way to get your fuel pressure data without all the clutter of a gauge. Julio sells a good one for a little over $100. Maybe $130? Something like that.