Help with A/F Ratios ???

[Wells]

I have a lm-1 wideband and dsmlink ..

I had it pretty well perfectly set from 4500 (when my turbo hits full boost) to 7500 at 11.7 A/F ratio ..


The next night I went out, the temp was a little warmer, and started to tune when I had to take away more fuel to get it back to 11.7 ... It was a little rich.


I got it back to 11.7 most of the way, then all of a sudden it dropped back down to 11.0, which is rich ... So I decided to ask before I took away even more fuel to get it back to 11.7.


Why is the a/f ratio getting more rich all of a sudden? The wideband is maybe a month old, and seems to be working correctly.

Any ideas?

 

[Staytuned]

Boost leak? that will make tuning hard as it richens up the more you leak.

 

[Wells]

Where do I get the coupling for the boost leak tester .. I have a 4" inlet on my turbo .. I think I can get the rest at home depot or lowes.


http://www.vfaq.com/mods/ICtester.html

 

[daren_p]

Are you tuning to 11.7 to 1 on pump, if so what octane? Don't you think your abit on the lean side with that air/fuel? If your looking for max power, you usually get it from running abit richer and adding more timing.

 

[Wells]

91 octane ... I was told that 11.6-11.8 was optimal, but what should I be aiming for?

 

[daren_p]

On 91 octane that is on the lean side, I would shoot for around 11 to 1, no more then 11.5 to 1 max. Like I said these cars make more power with timing so you may find that 10.5 to 1 with more timing will make more power. You have to play around abit to see what you car likes. Personally I run ~11 to 1 but run Ultra 94 fuel as well.

 

[Staytuned]

Where do I get the coupling for the boost leak tester .. I have a 4" inlet on my turbo .. I think I can get the rest at home depot or lowes.


http://www.vfaq.com/mods/ICtester.html

If you have a GT series turbo you don't want to pressure test on the compressor housing, it will go right through the oil seals into your oil return line. You want test off the lower IC pipe if you can.

And Darren you make power off pump gas with airflow (boost) and moderate timing. I set my boost, then my AF ratio (11.5:1) and then go tweak the timing sliders till I see knock or I lower the timing till knock goes away. I see on my setup 11.8:1 is the knock threshold for pump, I drop it down to 11.5 and it's gone. All with 15-16* of timing at redline.

 

[daren_p]

^Yes most of the time boost is what will net you the most power out of the 3 but I was just refering to timing & fuel.

 

[Staytuned]

Your right if your saying more power comes from timing as apposed to lowering AF ratios. You make more power with a degree of timing than lowering the AF ratio a few points for sure.

 

[DSM_NOOBIE]

You pretty much answered your own question. As the weather changes temperature wise your A/F ratio will also change repectively. The hotter it get outside the richer the mixture will be (air density is less). The cooler it is out the leaner the mixture will be (air density is greater more oxygen molecules = leaner conditions). So to answer your question trying to keep a target A/F ratio at 11.7 is going to be tough unless u can implement a device to compensate for the temperature variations. A nice fuel management system will allow you to do this but i assume you have some type of eeprom chip with your saved values burnt on?

 

[MMM]

Log your coolant temps. The ECU plays with timing when your hit certain temps. I think it is: pulls one deg. of timing when coolant temp is 200 or up, and 2 degs of timing when cooland temp is 230 or up. Log knock, air temp, and throttle pos. too and throw your log up.

 

[Wells]

I made a boost leak tester and pumped the crap out of it, but my boost guage wasn't going up ..

So all that was going down into my oil return line? Did I just hurt something by doing that?


I'll go get another coupling and try it on my intercooler piping.


The coolant temp was between 203-206 the whole time. I'm using dsmlink to tune.


I realize that when the temperature changes that it will change your tune a bit, but droping .7 to 1 full point? The temperature change wasn't really that big, maybe 10 degrees. It goes from 98 degrees outside to 55 in an hour in the midwest .. So are my a/f ratios going to be way off when it gets really hot?

 

[MMM]

Like I said, a change in .1 deg of temp 199* to 200* will pull timing (okay don't get too technical, i don't know if the ecu is THAT accurate) but you get my point. Pulling timing will change your A/F. Also, to see if you are leaking down your oil drain, pressurize your pipping and take out your dipstick/oil fill cap on valve cover (one at a time) and put your ear next to the hole. You will hear air rushing out if you have a leak to your oil system.

Is the pipe holding pressure, but just not making the gauge move? Or are you dropping pressure like crazy??

 

[DSM_NOOBIE]

yes believe it or not it will drop your A/F ratio by how much? i dont know...but a 10 degree temp variation is good enough. also you said night and day temp change from 98 to 55 degrees....then yes it will definitly drop a point or even more. those temperature changes are drastic in my opinion. your best bet is to have two setting, night and day.

 

[95FlamingTalon]

I realize that when the temperature changes that it will change your tune a bit, but droping .7 to 1 full point? The temperature change wasn't really that big, maybe 10 degrees. It goes from 98 degrees outside to 55 in an hour in the midwest .. So are my a/f ratios going to be way off when it gets really hot?

Your a/f ratio shouldn't change that much with a 10 degree difference in weather. I couldn't find a mod list in your profile. If you don't have a fuel pressure regulator, that's most likely the main reason for your problem. It will be impossible to get your a/f ratio to stick if you have an fpr overrun or boost leaks. If you could give some more info on your setup or post a log, it would be easier to help.
I would consider having a winter and summer setting for the temperature changes, but you shouldn't have to adjust it daily.

 

[Wells]

Ok .. Here's the mod list .. (I'm just copying and pasting, so some of it won't matter for my problem).

*6-bolt
*GT35 Turbo
*Apex'i front mount intercooler
*Greddy intercooler piping
*Greddy Type-S bov
*South Florida Performance exhaust manifold
*Eagle Rods
*Ross 8:5:1 pistons
*Head work\valve job\ Crower Springs and Retainers
*HKS Camshafts 272/272
*HKS External Wastegate
*ACT 2600 clutch
*Dejon Intake
*1st gen intake manifold
*72lb/hr Holley injectors about 740 cc
*B&M CommandFlo Fuel Pressure Regulator
*B&M Fuel Pressure Gauge Set
*Supra Fuel Pump rewired
*DsmLink V2
*Greddy Turbo Timer
*Greddy Profec B Spec II boost controller
*Apex'i downpipe
*Apex'i N1 exhaust



I rolled down the street and borrowed a neighbors compressor ... I hit 20 psi on my boost gauge, and listened for leaks ... The is a really good hissing sound coming from the back side of my intake manifold, or my tb .. I can't really tell and can't feel where the air is coming out ..

On my valve cover, the little oil filter on the left side got knocked off, and there is a lot of air coming out of the head .. I don't know if that's normal or not, but it seems like I have a boost leak coming some where from the intake manifold or tb ...


The other problem could be that I don't have a afrp, just the b&m ...

I did the boost leak test on the first pipe that came out of the turbo, since it doesn't work on the turbo itself.

 

[daren_p]

Like I said, a change in .1 deg of temp 199* to 200* will pull timing (okay don't get too technical, i don't know if the ecu is THAT accurate) but you get my point. Pulling timing will change your A/F. Also, to see if you are leaking down your oil drain, pressurize your pipping and take out your dipstick/oil fill cap on valve cover (one at a time) and put your ear next to the hole. You will hear air rushing out if you have a leak to your oil system.

Is the pipe holding pressure, but just not making the gauge move? Or are you dropping pressure like crazy??

Pulling timing will change your air/fuel ratio, care to explain that . Your talking about operating temp and not intake temps. The ecu will pull 1 deg of timing from 206 up & 2 deg from something like 230 up. It will also pull 1 deg of timing with inlet temps higher then 84 deg. With that being said I still have no idea why you think that when timing is pulled it will change your air/fuel ratio. As for a 10 deg difference in inlet temps, no that shouldn't chage your air/fuel ratio by that much. I have logged anywhere from 50 to 100 deg inlet temps and my air/fuel ratio probably didn't change more then .5, if that.

You need a compressor to do a proper boost leak test a hand type pump just doesn't have enough volume no matter how fast you pump to pressureize the system.

OK the first thing that jumps out is the B&M fpr modifier, ditch this thing it is useless. It just alows you to adjust the stock FPR but you still have the problem of over running the stock fpr return. The supra pump flows more then a 255 so an over run condition will defently be a problem for you, get a real FPR.

As for the boost leak, the leak you hear from your TB is most likely the BISS or shaft seals. To see if its the shaft seals rotate the throttle plate while doing a boost leak test, if the pitch changes you need to replace those seals. The leak through the valve cover could be several things, first thing I would check is the PCV valve, make sure its holding pressure properly. If it needs to be replaced make sure you get an OEM unit as the jobber ones don't hold pressure worth a crap.

Also get a spray bottle with some soapy water and basically spray down all pipes, vacuum hoses, injectors, etc in the engine compartment. The leaks have to be fairly substancial to hear them, if you go over everything with the soapy water you will be surprised how many other leaks you can find.

 

[Wells]

It must be the shaft seals then, because when I pull on the throttle plate the sound almost stops ..

When I put my finger over the hole for the biss screw, I can feel air pressure .. so it's leaking a little bit from there, too.

I'm not sure if the pcv valve is what it's called or not, but the tube under where the filter was is shooting out a lot of air ..

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[Wells]

How do I replace the seals?
What should I do about the biss screw?
Is it normal for air to come out of the pcv valve? If that's what it's called, and what do I replace?



I really appreciate you guys taking the time to help me, and I'm sorry about all of the questions .. but I don't really have anyone else to ask.

 

[daren_p]

No that thing you have circled is the crank case vent & air shouldn't leak out of this (this could just be the pcv valve or the valves, turbo seals etc), the pcv valve is on the back of the valve cover on the passenger side, there will be a hose connecting it to the intake mani. You will need to take it off to check it, just make sure you don't torque it down alot when installing it, as the valve cover is pretty fragile. It is common for these to need to be replaced so I would start there. TB shaft seals are a very common boost leak source, here is the vfaq on how to change them, if you don't know about it, check out www.vfaq.com it will have answers to alot of your install questions.

http://www.ca.dsm.org/faq/tb-shaftseals.html
http://www.plymouthlaser.com/tbor.htm

Since your taking the TB alll apart do it right the first time & get the proper seals:

http://machv.com/throtbodseal.html

I just didn't mine this past spring, not that difficult just make sure you note everything down to get it put back together correctly. Mine were leaking with only 40K on them, now they seal perfect.

For the BISS screw it is more then likely the BISS oring that is leaking, you can pick these up from Mitsu or most DSM vendors. If your missing the rubber cap, get one of those as well, with the cap missing the oring tends to dry up & leak faster.

 

[MMM]

Pulling timing will change your air/fuel ratio, care to explain that . Your talking about operating temp and not intake temps. The ecu will pull 1 deg of timing from 206 up & 2 deg from something like 230 up. It will also pull 1 deg of timing with inlet temps higher then 84 deg. With that being said I still have no idea why you think that when timing is pulled it will change your air/fuel ratio.

Idk if he will experiace the same think with a wideband, but on my stock O2 and emanage on my nissan, you see changes in airfuel when timing is changed. I know its probably not changing the ACTUAL A/F thats going into the head, but the logger see's changes in O2 signal (due to a/f being ignited at a more/less optimal time) and reports that as a change in A/F. I don't really know if thats what he's experiancing ### I haven't seen his logs.

 

[MMM]

Refer to this log that a user posted (DSMLINK logger). Watch how the timing and A/F follow eachother. Not saying I am right, or I am the best tuner out there, but I was experiancing similar curves on my previous car and I always a assumed A/F was affected by timing. (or vice versa but I don't see how A/F could affect timing).

 

[Wells]

Here's a run ....

So the crank case vent should be pushing out a lot of air?

I'll check the pcv valve here in a minute, it's so damn hot outside.

 

[daren_p]

Here's a run ....

So the crank case vent should be pushing out a lot of air?

I'll check the pcv valve here in a minute, it's so damn hot outside.

Someone correct me if Im wrong, but no I don't think any air should be coming from your crank case vent during a boost leak test. If you've never replaced the pcv valve you should probably pick one up anyways, their under $10 from the dealer. You should be able to blow through them one direction but shouldn't the other way. Its best to hook them up to an air supply and run what ever pressure to them that you boost to see if they hold, but not everyone can do this. Also as another note, its not the best idea to have a breather filter on the crank case vent. Its best to have it hooked up like factory to the intake. If you want to keep the blow by out of your intake hook the crank case vent to a catch can then from the catch can to the intake, just make sure its a sealed catch can as a vent here will throw off your air/fuel ratio as well (just not sure as to how much), it will also change your g/rev.

See here for crank case/catch can:

http://www.dsmtuners.com/forums/showthread.php?t=233251

 

[daren_p]

Okay I took a quick look at your logs, & it looks like you have some work to do. First of all what do your LTFT lo & mid look like? I don't recall but what are your global and deadtime set to? You are removing WAY to much fuel and timing. What boost was this log with, looks like about 16 psi? Your airflow is very low, @ 18 psi I'm seeing the same amount of airflow with my evoIII compared to your GT35 & I still have the stock cams in right now. If I were you Id start over, zero out the timing and fuel sliders. Next log your MId & Low trims and get them around zero with your global and deadtime settings (the users guide has a starting reference for different injectors). Once this is done you can start removing fuel, you don't want your fuel sliders anywears close to were you have them now (if your trims are properly inline). If you go to the DSMLink boards, there is a sticky under support thats called downloads, there is a link to a PDF in there that will help you with your fuel/timing sliders. For example if your trims are inline to get an 11 to 1 air/fuel the most you want to remove is 15% (this is in the very upper rpms, lower rpms you don't remove as much), if I recall some of your sliders were like -30. With the current tune I would think the car will be running pretty crappy.