I'm currently in the process of street tuning my car and I've managed to get my AF curve pretty flat at around 13.0-13.6 across the board.

The outside temperature right now is about 20 degrees.

My question is,

Will I have to re-tune my car when the summer comes around due to the higher outside temperatures?

The air will be hotter so it would be less dense, causing the car to run richer theoretically, but I'm wondering if the MAF will compensate for the change in temp.

So if the MAF compensates and the signal is still being changed the same way by my VAFC II, I would think the tune would remain the same.

Am I on the right track here?

 

if you tuned properly, the IAT sensor/MAF signal should change with the temperature and therefore compensate accordingly. If you are using maps, then you will have a problem

 

What do you mean exactly when you say "If you are using maps?"

I'm doing a WOT run in 3rd gear and recording the AFR then adjusting the settings on my VAFC and repeating the process until a good AFR is achieved.



This is a picture of one of my runs from 1200rpm to 4000rpm. I added alot of fuel at 4000rpm so I could see where I was on the graph. Does this look ok to you?

 

You'll be fine. I did the opposite, tuned my car in 40 degree weather and my AFR is around 12.8-13.2, still the same at 18 degree ambient temperature. I still need to adjust the acceleration maps on my e-Manage because it goes too rich when I stomp it.

By "maps" Knight means that you're using a MAP sensor (absolute pressure) to monitor the engine load and thus make fuel adjustments according to those. MAP sensor only goes off of the pressure in the intake manifold as opposed to mass airflow, so it is harder to tune for temperature changes (probably requires some kind of air temp/water temp adjustment map)

 

Oh I see, thanks for clearing that up. So do you think that a 13.5 AFR across the board is good?

I do have some peaks that go as high as 13.8, but I'm going to make sure I try and get closer to 13.2 for the 4000 to 6600rpm range. You think I'll be safe with that?

 

13.5 AFR is what the stock ECU normally is tuned for on stock exhaust (headers/catback throw that way off though), I honestly would tune it a wee bit richer around 13.0 AFR and maybe dip it to like 12.8 towards redline.

I can run more timing so I'm running 12.8 to keep the combustion temps cool and keep the knock down. You really aren't gaining any power by trying to go as lean as possible without Armageddon happening, there's an optimum range for VQs to make power.

Since you've got the AFC and wideband+logger I'd say try a 13 flat AFR and see how you like it.

 

Thanks, I'll rich it out a little bit. Its kind of difficult because I have no way of knowing what RPM corresponds to what AFR on the graph and I can't simply scale it linearly because I'm not at like 4100rpm for as long as I'm at 2100rpm.

All of my corrections on my VAFC are less than +- 5% btw.

 

What wideband are you using? Do you have LC1 or LM1? Just curious because if you have one made by Innovate motorsports you may be able to get an RPM converter so you can plot out your rpm vs. AFR on the laptop.

 

I'm using an Innovate LC-1.

Where can I find this RPM converter? What is it called?

I was going to use a video camera to record my tach and use that to relate to the graph LOL

 

Innovate has a few accessories that can work with the LM-1 Wideband, (LMA-2) to pick up the RPM signal and log it. However I can't find anything for the LC-1, so you'd probably have to look into buying an LMA-3 "AuxBox" which is a 5 channel datalogger than can pick up a tach signal.

 

That sure is lean....N/A LBT(lean best torque) 13.3; RBT(rich best torque) 11.5; but the sweet spot for most N/A motors is 12.5 and my WOT target area is 12.2 during the initial stumping of the accelerator and leaning out to 12.8 @ redline!
Be careful buddy one misfire @ high rpm and 13.5 AFR will destroy your engine for sure.....

 

I richened my mixture today just to be safe.

I actually used a video camera to record the rpm from my VAFC and the afr from my laptop and then I went home and went through the video frame by frame to make myself a graph of AFR and Time.

I've managed to get it around 13.1-13.4 from 1200 to 3000rpm with it gradually going more towards 12.9-13.0 as it gets closer to redline.

I was reading some thread on here a while back where people were talking about running 13.5-13.8 to redline!

 

Haha, there are people with 4.5 gens that have tuned for 14.1 at WOT

 

One more thing,

Is it normal for the AFR to jump around by like .3. Like my graph is really jagged and I know it's not because of my AFC because the spikes occur 2 or three times per 100rpm.

They are nothing major but I'm wondering if the dyno sheets I always see use some sort of smoothing.

When I set smoothing to like 2 sec, the graph looks much cleaner.

And I can't even remember how many other web sites and forums say to tune your AFR to 14.7 at WOT!

People hear that 14.7 is optimal for cruising so they go around spreading misinformation. If I didn't check the org, I would have toasted my motor for sure.

/rant

 

Most dyno sheets on the .Org at least have a smoothing factor set to 5 to eliminate those spikes and show you a smooth curve. And yes, my datalogger does this too, the AFR will jump maybe +/- 0.2 AFR across the entire RPM range. No worries here.

14.x AFR will gain you less than nothing. You'll have less power, hesitation, shat driveability, etc. ESPECIALLY with an AFC unit because when you lean out your AFR on a V/SAFC it actually adds some timing so you have high combustion temps + timing = knocking Good thing VQ35 heads have superior design for knock suppression. That keeps a lot of idiots out of trouble

And yes most people are tune-retarded so misinformation is evident.