Optimal A/F Ratio Followup

[andymoraitis]

For those of you who jumped in on my last thread about tuning for an optimal A/F ratio, thank you for your help and guidance in teaching me the basics of fuel tuning and also helping me to understand the nature of octane relative to detonation. In any event, I have a follow up for all of you:

I received both of my chips today and after running some Seafoam through the vac line on the BOV to clear up my carbon deposits from running so rich, I have the following findings to report.

Chip 1: 11:1 A/F with 16 degrees timing. Whoa! What a difference from the 9.5:1 A/F chip I was running before. I started boosting at 18psi and slowly worked my way up until I triggered knock. This occurred at 21-22 psi. The boost was backed down to 20 psi and no knock was observed in ambient air temps of 50 degrees on a heatsoaked intercooler. Yes! For the first time I was able to run lean enough to actually heat soak my stock SMIC!

Chip 2: 10.5:1 A/F and more timing advance. I let the car cool down completely and installed this chip. Knock was triggered at 19 psi on this chip despite the fact that it's made to run more on the rich end. I'm not sure why, but it could be the additional timing causing this to occur.

After the Seafoam blowout, the car did not produce anymore black clouds under hard acceleration with either chip and I no longer encounter low RPM rich backfires like I used to. The stock SMIC will be the next piece to go and will be upgraded in the next month or so with a DejonTool unit that will more than support the Big 16G. In the interim, I will likely remove my stock SMIC and clean it since it hasn't been done and probably has oil in it from blowby (I now have a vent line that doesn't go back to the intake).

FYI, knock sum at each boost level was only 5 counts and since I don't have a logger hooked up, I can't tell what happened to timing, but I can say that the leaner A/F's have made a huge difference in the way the car pulls. I was actually able to use the word "sick" in a healthy way! My inclination is to keep the 11:1/16 degree chip since it allowed me more boost, but your opinions are more than welcome.

Thanks guys!

Andy

 

[CanadianTSi]

Glad to hear.

I'm amazed you can run 20psi on the stock SMIC with no knock. how long does it take to heatsoak 1 or 2 pulls?

 

[andymoraitis]

At the moment it, it heatsoaks in 2 pulls. I really need to upgrade to a better unit and then I think I'll be good at 20psi on pump until it become ungodly hot outside. FYI, the maximum knock count I get is 5 even when heatsoaked, so I don't think it pulls too much timing.

Hey, there's a new question for you guys. Approximately how much timing would be pulled with 5 counts of knock? Max timing now is set to 16 degrees.

Thanks again!

Andy

 

[CanadianTSi]

I'm pretty sure it's 1 degree.

 

[andymoraitis]

Thanks again for getting back to me so quickly. I think I'll clean this sucker out this weekend and then take a trip to DejonTool and go with the bigger unit. What I'm most pleased with is the fact that the car doesn't labor at all and really moves the tach up to 7000 and beyond with much less effort than it did before. It definitely feels like a 12 second car now. I'll track it next week and let all of you know the results.

Thanks for the help!

Andy

 

[andymoraitis]

I'm pretty sure it's 1 degree.

I happened to check with Jeff at DSM Chips on this one and he informed me that a good range to shoot for is 1-3. At 7 counts of knock, the car will hold timing advance and past that it will start to pull timing so at 5, nothing was really happening on the negative side.

I did clean out the intercooler (I can't believe how tiny that thing is) and plenty of oil came out when I flushed it with gas. Repeated 20psi runs in ambient air temps of 40 degrees produced no more than 3 counts in 3rd and 4th gear. Nevertheless, that thing needs to go since it's holding me back from running 21-22 psi with no knock.

Cheers!

Andy

 

[CanadianTSi]

I happened to check with Jeff at DSM Chips on this one and he informed me that a good range to shoot for is 1-3. At 7 counts of knock, the car will hold timing advance and past that it will start to pull timing so at 5, nothing was really happening on the negative side.

I did clean out the intercooler (I can't believe how tiny that thing is) and plenty of oil came out when I flushed it with gas. Repeated 20psi runs in ambient air temps of 40 degrees produced no more than 3 counts in 3rd and 4th gear. Nevertheless, that thing needs to go since it's holding me back from running 21-22 psi with no knock.

Cheers!

Andy

I see from your other posts that your thinking about a SMIC, I would Highly suggest a FMIC for you and your setup. It seems like you like to be able to get the most out of your setup, a FMIC will do this for you. Also if you ever upgrade Turbo's down the line you won't have to upgrade your Intercooler.

 

[andymoraitis]

I can understand where you're coming from and I certainly appreciate it. Looking at the whole picture though, I have no plans to go past the 16G series either now or in the future. I know that an FMIC is a do it once and forget about it type of mod, but I've been assured by Dave Johnson at DejonTool that their Super SMIC is very well matched for my setup and goals (eventually running 12.6 on pump gas). I also prefer the sleeper look and have received some excellent feedback from tuners who use this on their Evo III 16G's without issue.

Nevertheless, I really appreciate the input!

Andy

 

[90 GSX]

Sorry to bring this back from the dead but I'm going through this same issue right now. I was wondering what kind of gas you used when you tested the chips? I am running 91 octane and have very similar mods to yours. The chip I just got from Jeff this week is tuned for an approximation of 2g timing tables (I'm a 1g with 2g pistons) which should net me 16-19* max advance at WOT and it's tuned for a 10.5:1 A/F ratio. I am putting on an aeromotive afpr at the same time as the chip along with a 2g mas which the chip is also tuned for. What do you think about this combination? I'll know the results this weekend but do you think that A/F ratio will work out okay with 91 octane to keep the knock down a little bit.

 

[andymoraitis]

Wow, this really is back from the dead. As far as the fuel I was using, it was 93 octane for all of my test runs, but my setup has changed significantly since then. I now have a 2.3 with a 50 trim and a larger SMIC. I'm running 25 psi on 93 at 43 psi base fuel pressure and I see 2 counts of knock in third gear on 93 with an 11.5:1 A/F and a max timing advance of 12 degrees.

As far as your setup, switching to 2G timing maps with the increased compression is a sound idea. What you'll find is that our motors become less sensitive to A/F once a leaner ratio has been achieved. Around 11-11.5: 1 is fine on pump and the gains by leaning out more are minimal and may bring on the onset of knock. You won't see a huge difference with 10.5:1 on 91, but I don't think that going to 11:1 would have hurt.

I'm pretty sure you'll have a good tuning setup and I look forward to hearing how it works out for you. Keep me posted,

Andy

 

[elfroggo]

I guess your plans changed eh? Haha

I can understand where you're coming from and I certainly appreciate it. Looking at the whole picture though, I have no plans to go past the 16G series either now or in the future.

 

[andymoraitis]

Funny you mention that since I didn't read through the whole post again. But yes, they certainly did. If I had rebuilt the motor into a stock 2.0, there would probably be an EVO III on the manifold. As it stands, I'm really glad there's a 50 trim and a 2.3 under the hood. It's just way too fun to describe compared to what I had.

 

[44pirate]

A GT35R is just itching to go in there!

 

[andymoraitis]

Hmmm, don't have that kind of cash of the clutch to handle it. I'll see how the 50 does and then maybe step up to a 60-1...and keep the damn sidemount just for fun.

 

[90 GSX]

Do you daily drive that car? I've been thinking about getting my block machined for a 4g64 crank and going with an hx35 in the future. How does it drive, smooth, stockish???

When I tune my trans-am which is also boosted by a supercharger, I aimed for 26* max advance and 12.2:1 A/F ratio and it runs like a beast. I admit I was surprised when Jeff O told me that the stock A/F ratio is less than 10:1 and that my car would probably like 10.5:1 We'll see how it goes.

If I change the fuel pressure will the a/f ratio change or will the computer try to compensate by adjusting the IDC??

 

[Kevin Jewer]

The computer has no idea what the fuel pressure is, it assumes it is stock. In closed loop it will attempt to tuen out any changes of course, but in open loop FP will affect AFR accordingly.

I've found that AFR changes don't affect power or knock all that much, if you are within reason. Most of my experience in this is with race gas though, since on pump gas I found 11:1 to be optimal many years ago and don't vary much from that these days. But on race gas anything between 11:1 and 13:1 seems to make almost identical power, within one or two mph at the track. It has some effect on knock for sure, and is usually the reason I had spark plugs come apart and take out my motor. Timing on the other hand has a much more profound effect on both knock and power. Taking out one degree of timing where your knock starts can have more effect than going from say 11.5:1 to 10:1. Veyr effective for controlling knock. Also note that the stock ECU decays the knock retard value very slowly, so a little knock at 5500 rpm for example can ruin an entire gear's pull. You can often take out the timing at only that rpm, and the timing retard that was present after it will not appear.

 

[90 GSX]

The computer has no idea what the fuel pressure is, it assumes it is stock. In closed loop it will attempt to tuen out any changes of course, but in open loop FP will affect AFR accordingly.

I've found that AFR changes don't affect power or knock all that much, if you are within reason. Most of my experience in this is with race gas though, since on pump gas I found 11:1 to be optimal many years ago and don't vary much from that these days. But on race gas anything between 11:1 and 13:1 seems to make almost identical power, within one or two mph at the track. It has some effect on knock for sure, and is usually the reason I had spark plugs come apart and take out my motor. Timing on the other hand has a much more profound effect on both knock and power. Taking out one degree of timing where your knock starts can have more effect than going from say 11.5:1 to 10:1. Veyr effective for controlling knock. Also note that the stock ECU decays the knock retard value very slowly, so a little knock at 5500 rpm for example can ruin an entire gear's pull. You can often take out the timing at only that rpm, and the timing retard that was present after it will not appear.

Wise words... I forgot that the ECU goes into open loop at wot. I could use my wideband to fine tune the a/f ratio, nice.

For those who come across this post in the future, please read 95GSXRacer's words carefully because that it essentially what knock is all about. From my tuning experience, I have found that when knock is detected the computer will retard much more timing than is needed to compensate for the knock and the decay rate is usually very slow and generally dissipates only after a shift into the next gear. I had a situation on my trans am when I first started tuning where I had a knock spike of 7* at around 3800 rpm but when I increased the decay rate the knock disappeared by mid 4000's. I took out 2* in that region and smoothed the curve out a bit and got rid of the that huge 7* retard which absolutely killed the power.