I just wanted to have some input from the guys that have already done some logging of A/F before and after installing some sort of piggyback or standalone EMS (IntX, EMU or other).

I have seen that most of you target the mid-12s as best A/F ratio for N/A trim. However some of the guys in here are also saying that one could go as far as 13.2 or even 13.5 under WOT (I'm talking about open loop here only) and still have an engine that will last a while.

According to my logs on some runs (1st-2nd, 3rd and 4th gear pulls), my 4port aims between 1:11 and 1:12 in the open loop map, so I'm guessing there are a couple of ponies somewhere in there. My main question is: do the graphs seem like there is indeed some decent power to be found tuning the A/F ? The next most obvious question is: will the EMU (lower cost) be able to locate and bring to the surface these additional HP ? (by having the AutoAFR feature aim at i.e. 1:12,5)

 

Per the racing folks at 7stock (Speedsource Racing) that run the ST and GT cars, the Renesis in NA for makes max power at about 0.92 - 0.93 lambda or (13.5 - 13.6 AFR). Mind you that is the 6port engine, but I doubt it would be that different.

I think my last dyno tune with the xceptor was in the 13.3-13.4 range, thats were I got the most power.

 

Damn. My log files seem to be filled with 0,70s and 0,80s at 100% ThrtlPct, so I guess I'm running a little rich
If as you say low 0,90s is the best target A/F, then we are talking about almost 20% variance in A/F ratio, which will lead to an equally dramatic increase in torque/HP output. Well, maybe not 20%, but even a 10% increase at WOT will mean about 15-18HP more....
Damn....

Edit: forgot to mention that I'm also loggin CatTemps of about 930 Celcius at WOT, which equals to 1700 Fahreneit....too hot maybe ? How can that be though ?

 

the EGT temps recorded are going to be off by about 100-200 degrees F (they are to high) due to the inaccuracy of the o2 sensor for this measurement....So you can back your temps down a bit and your in the normal operating range i believe.

what are you going to try to tune with?

 

I've done quite a lot of dyno & on road testing to see where max power/best acceleration is . What I have found is that you get a bit of extra power by leaning it out ( less than 10 hp ) to around 13:1 but it seems to make very little difference either side of that . Anywhere in the 12.5-13.5 range seems about the same.
My biggest gain came from spark timing changes but that could be more to do with the crappy fuel we have here.

 

Well, my weapon of choice would be either the EMU or the CZ (latest version). A friend of mine has both sitting on his bench, so he will probably let me have a go at both of them. I would really prefer the EMU with the o2 plug-in, so that I may use the TargetAFR feature.

In all my logs (2nd, 3rd and 4th gear pulls) while at 100% throttle, the lambda readings fall between the 1:11,5 and 1:12,5 range, but most importantly read way too rich (closer to 1:11,5) when I go above 5K rpm. Hence the continuous drop in torque/HP output above this mark.

The easy solution would be to aim for 1:12,5, which appears to be a safe and decent-power-producing AFR, but this can happen only with the EMU....unfortunatelly I have no experience fiddling with timing, so I really can't tell anything about this...

 

Here is a chart showing the diff in acceleration in 3rd gear vs AFRs . However the other change not shown is the timing which gave most of the gain. I have proved this not only on the dyno but with some controlled acceleration testing .

 

Start with the Canzoomer. The EMU target AFR function is not working yet so you won't be able to use it. If your N/A and not planning on going FI anytime soon, then the EMU is overkill.

 

So Brettus you have aimed for 12,5-13 AFRs ? I would like to know what EGTs you are seeing, because frankly I would feel very uncomfortable with going above the 1:12,5 mark (roughly a 10% difference from my current AFRs) taking into account that I am already seeing >900 Celcius at the catalyst...

And tdiddy, no I don't plan on going down the FI route, probably never will...but in any case my friend will indeed first lend me the CZ, and I'll take it from there....problem is I won't have control over the timing....

 

No cat

All the info I see coming from the States suggests that stock timing is fine for their gas .
Our gas is not so good (according to local tuners ) so timing becomes an issue .

 

Why would you not have control over timing? I am pretty sure you can adjust timing with a CZ.

 

Your best is to get on a chassis dyno and find out what the engine likes. Egts/afrs are going to vary from car to car, even with the same mods..

 

Not exactly the reason why, but I have already scheduled a dyno next week, just to make sure what HP I'm putting down, and at what A/F ratios. I'll be checking my EGTs as well, so I will have a solid base to build upon....

I'll be posting the results next week, so I'll take it from there...

Anyone else with an N/A tune ? What cat temps are you seeing ?

 

[QUOTE=The Ace]So Brettus you have aimed for 12,5-13 AFRs ? I would like to know what EGTs you are seeing, because frankly I would feel very uncomfortable with going above the 1:12,5 mark (roughly a 10% difference from my current AFRs) taking into account that I am already seeing >900 Celcius at the catalyst...
[QUOTE]


I'm seeing 970 deg C at end of 3rd gear WOT run

Edit : vs 962 deg C without the piggyback tune .

 

Sounds good....higher than what I'm seeing, so I'm guessing there's room for some leaning out of the A/F....