I tried searching, but couldn't find any specific answers to my question.

I made several WOT runs today in 3rd gear on the highway from 60mph to 100mph, maybe a little over. My AFR was around 12 at 4k, 11.2 at 5k, and 9.9 at just about red line. The car felt "slow" going from 60 to 100, but maybe that's because I'm used to it already. I want more power, lol, but who doesn't. So, am I running too rich? Thanks.

 

The purpose of the extra richness is to cool the piston crowns, exhaust valves, and the catalytic convertors in extended summer [hot] operation.

Some people do extended high rpm wot runs vs just simple quarter mile.

TIME IN THE 5000-redline rpm ranges is the key here!

The 10.0 AF might be leaving 5% [<10%] of possible power on the table [vs 11.8 -12.2 AF]. Depends on how much reserve safety you wish to maintain?

 

^^ Cool. Thanks.

 

I don't like the fact that you're running a 12:1 afr at the boost threshold. You should be running no leaner than, say, 11:1 especially between 3k and 4k where boost builds and hits fully..........12k is getting dangerous.

basically, it looks like you need a tune.

 

^^I'm actually supercharged and I did get tuned. At 3k-3500 I only see about 1.5 lbs of boost, which surprises me. I thought I would have more at that point. I don't even get a lb until 2500-3k, and at 2000 I'm exactly at 0. The bov doesn't close until about 3k-3500 when it sees enough boost. I appreciate the concern, though.

 

well, it was a crappy tune, whoever did it. I'd run richer than 12:1 at 4krpm under boost, no matter how much boost.

Also, 9.9:1 is WAY too rich....anywhere in the powerband it doesn't matter, that's entirely too rich. That's plug-fouling, coating-the-pistons-in-carbon-rich.

 

ic

 

Here is Andy's AFR plot from the tuning session. This was done post cat as at the time his pre cat wideband was non functional. This is done using a Motec wideband.

What Andy is experiencing is an inherent problem with the use of a unit that only modifies the mass airflow signal. Such units are highly susceptible to the ECUs air temperature/density compensation. A 2% increase by the ECU multiplied by the increases fuel pressure by the Vortech booster pump equals a lot more than 2% increase in fuel under boost conditions.

As for 12:1 AFR being too lean I will explain a little about ignition timing and fuel mixtures. Richer than 12.8:1 there is no increase in power to be made from the fuel alone. Increasingly richer mixtures do indeed begin to cool the cylinder walls and beyond 9:1 you will start to lose power. All you need is enough fuel for the amount of ignition advance that you are running. Since this is a vortech kit with a split second box there is no ability to advance the timing more than stock. 12:1 AFR is totally sufficient for the stock timing at those RPMs with this amount of boost.

 

"How rich is to rich?"
when you take a dump and wipe with 100 dollar bills!
( I look around, everyone stops talking and start staring at me! Im embarassed and start walking backwards akwardly like peter from family guy!)

 

Opera is to damn rich.

 

To answer the question, how rich it too rich ... when your exhaust tips start glowing, that is too rich. When your car coughs or stumbles, that is too rich. When you let off the gas and the car stalls, that is too rich.

You certainly don't want to run 10:1 AFR for any extended period of time as the cooling effect on the cylinder walls also dilutes the oil on the cylinder walls and hence increases piston ring friction.

With the volume of air that is being consumed at 5000+ rpm and the amount of cam overlap with the stock cams, most fuel flyies through the cylinder and down the pipe. The length of time is also measured in a handful of seconds and not minutes.

Just as a FYI - the Subaru STi runs 14.7:1 at full boost as do many other OEM turbo cars ... it's all in the timing.

 

Oh, and if you can afford my tuning time - you're too rich

 

You can say that again lol!

Btw, thanks for clarifying Giles.

 

ANDY: Why did you say you were seeing 9.9 AFR? It looks like you are at or above 11:1. Confused.

 

Because I was. This plot was from the dyno using his motec wideband sensor. The 9.9 I saw was on my Zeitronix and it was consistent. Every time I hit 6200 rpm I would see 9.9. But, now that I understand how the SS box works and modifies the MAF sensor, it makes sense. It was pretty cold last night, about 58 degrees, and if the MAF was trying to compensate then it makes sense why I was running so rich.

The best way to find out is to switch to a Greddy EU, so that you have control over the timing and not have to rely on the MAF. I will be going this route shortly. The only reason I didn't was because I was going to put in other stuff at the same such such as 3.12, injectors, pump, etc. I didn't want to have to pay for another tune with the Greddy. Might as well do everything at once. I also wanted to see how the stock vortech kit feels like and get used to driving a boosted car, even though it is an s/c and feels like a v8, it's still much different than stock.

 

I wouldnt want anything richer than 10.8 a/f on my car. Nothing leaner than 12:1-depending on where in the powerband its happeneing. Get a tune.

 

FYI - according to the dyno data, ambient air intake temps were 90F when we dyno'ed your car.

 

Reallly? It was that warm in there? So that's a 32 degree difference in temp from when I made my runs. No wonder the MAF was on crack

 

Dyno and street are very different beasts. Different sensors, different locations, different air temps ... lots of different conditions environmental or otherwise.

 

O yeah, and I think I got carbon monoxide poisoning lol