So the I got the autotap for my car. I decided to go out for a spin and do some full throttle runs.

First the intake air charge went up about 12 degree above ambeint. After idling in place I got the temps up to 81, but once you start moving it quickly dropped. The temp outside was about 45 degrees and I saw intake temps about 57 will drive at hiway speeds.

During a run from about 20 mph to about 85 I noticed at high RPM the Air/fuel ratio droped to about 11.4 from 14.2.

I realize the stock O2 sensor isn't the best probably but it's reading lean at about 4000 RPM @62mph, 90% throttle position, so you would probably start going even more lean unless the stock injectors are holding back. Full boost.

 

I have absolutely no idea what that means, but thanks for the info .

 

You mean 20 mph correct?

 

hehe I just corrected that 2 seconds before you posted that ^^^^^

 

Looks like pretty good info...at least we know the i/c does it job....

 

you guys have a stock wideband o2? Most cars have a short band and measure from .000-1.000

can you post the log so i can see it?

 

Werd. Let's see the log... I didn't know the stock O2 was wideband either!! I thought I remembered the Redline guys sayin it was NB!

 

Thanks Zinner for taking the plunge...I hope you don't mind getting a lot of questions, I know there's a million things I want to know, but will try to wait until I get one and try not to bug you if I can help it.

I, like stuffy236, would like to see the 02 readings on that 20-85 run. Would like to see Injector Pulse Widths and Ignition Timing Advance also. That is if you have it...I wouldn't want you to go out of your way and beat on your car just so a guy you never met wanted to know.

I see that autotap reads Knock Retard also, so if you have that from your run, can you post it also?

A million questions running through my head and I appologize if I am bugging you.

 

Well last night was the first night I had the autotap so I didn't get a lot of great data, some good data mixed in with a lot of regular driving.

The autotap does monitor knock retard however it has always registered 0.

I can read ingnition advance timing so I would assume when the advance is low that it is being retarded

Also I run 93 octane so it's possible on a cool night like the time I was testing there was 0 knock.

I definetly want to get a good 0-100 mph run on the car. I need someone to help me do that so I will have to wait till this weekend most likely. Also I was capturing a ton of stupid data during my runs so I can also only assume that my data points aren't as frequent because of the amount of data being pulled.

From now on I plan to grab:
Vehicle Speed
Engine Speed
Intake Air Temp
MAF
Manifold Air Pressure
Calculated Air Flow
Injection Pulse Width
Ignition Advance timing
O2 reading
Knock Retard

Any other suggestions. I tried to do fuel pressure but it's not avalible.

 

Zinner,

the information looks great and i see that where it should be under WOT around 11.4 to 11.8 A/F depending on timing and knock and of course octane of fuel... but the best thing to do is to get more readings then one on one specific run...

Example when i do tuning on cars i dont look only at the software but on a wideband dyno jet dyno...then compare the numbers and see the difference.

Now if you are under WOT and and no knock and no timing is being pulled out then your motor is in good conditions but if you notice knock and timing and your 11.4 A/F leaning out there is something wrong!

I know when i did my first ATI Procharger on a 2.2 ecotec motor the ECM handled the boost pretty good and air/fuel dropped with the added boost...so keep the data coming and i agree with YAJ what data you have is fine i dont need you running around punching your car to get data...

Thanks for the post!

Great information to know!

 

just to see if KR works, do a run during the hottest part of the day on 87 octane and see if you get any. You might not since it has a IC, but you never know.

 

stuffy236,

He is correct depending on how hard you are running the car and fuel detonation (bad) you might pull out 2degrees of timing? but i hear the roots IC is a very good design so to get it to Detonate might be tuff unless you are running more boost then the 12psi?

But again if you are in 110 AZ temps i am sure the timing will be pulled out as the temp is so damn high

 

Yeah even while idling in place I could only get intake temps up to 80 degrees on a 45 degree day. Once I started moving the temp dropped in about 60 seconds to like 53.

 

Nice!

 

having a few * of kr is bad, not good, but it wont destroy your engine. Hell at one point had 7* of KR on my GP . I just want to make sure the SS PCM actually picks up KR which would be a lot easier than guessing with the timing numbers

 

Presumably you should see some retard. If you don't see any at all on a hot day w/ a hot engine & 87 octane, then I can't see why Chevy would have insisted on the 91 rating. But yeah, I'd love to see as well!

 

11.4 is pretty lean in my book. Zinner, you said the timing seem to be holding back.
What kind of numbers were you seeing through the run?
Whats the total advance?
Thanks

 

please please please just post the scan. It would stop you from having to answer a LOT of questions and we could disect it better than you giving us little bits of info.

and i agree that 11.4 is awefully lean

 

That's just typos, right guys? You know that 14.2 is leaner than 11.4,... Lower = richer.

11.4 isn't lean at all. In fact it's on the rich side. Pretty normal for a stock tune at WOT. On a stock tune at WOT (which is open loop, remember - lookup tables only, no O2 feedback), you generally see a curve start around 13:1 or so and drop to 10-11:1 or so at high RPM.

Going from 14ish to 11ish during a WOT run doesn't seem abnormal to me at all....

 

doh! I just read redrockets post and didnt even think for myself. You are correct the lower on a wideband is richer while lower on a shortband is leaner.

Even if he's running rich, he can get more HP out of leaning it out (to an extent) although different engine like different ratios so you never know without testing.

 

Actually the numbers he was quoting were A/F ratio, not sensor voltage. Doesn't matter what type of sensor was used, lower A/F = richer.

That's true though. Generally stock open-loop WOT tables are richer than they need to be for safety margin. It definitely doesn't need to be 11:1. So yeah, if you were to tweak that slightly to something closer to stoich, you could make a bit more power. That's true of just about any stock car - a good tune to lean it out just a touch will get you a few more ponies. Definitely wanna be careful on a blown engine though.

 

Sorry guys, I misread the post also.

 

yeah i was going to say 11.4 air/fuel is not lean at all if you want to see lean here is a dyno run where injectors fail as the HP starts going up around 300RWHP and leaned out to 15.1 air/fuel on a 383ci stroked SBC with a D-1 Procharge making 11PSI if boost. That is not good news i can say 11.2-11.9 air/fuel is where i run my cars depending on boost and timing...

*GRAPH REMOVED, cause it's large and annoying*

 

holy huge pic! could you resize that or give a link instead?

and that A/F ratio is UGLY! You want it to be as flat as possible. Looks like that car needs some more tuning.

 

I got my cobalt ss/sc to register knock retard. It registered a max of 1.4 degrees of knock retard on my autotap today. Also got some other blips at .7 degrees and less.

The engine was basically just idling when it happen at 782 RPM , car wasn't even warmed up yet. The air intake temp was 77f.

Then I got .4 degrees when I was going about 62 @2500 RPM. I am not even sure if these make any sense to me, since they don't seem to be happening under heavy acceleration. But I figured I would share to see if anyone else has any thoughts.