in the tables (PE % change to Fuel/Air ratio vs. coolant temp or rpm) and (Open loop change to Fuel/Air ratio vs. coolant temp or rpm)? Which table would be best to modify to add more fuel at WOT? My O2 is running around 790-810mv and the tips on the plugs are pretty white which would verify the lean condition. I got a 255pump so my pressure is ok and I'm running 24lb injectors which should be enough. Also, what exactly is PE? Is this the same as WOT? BTW, this is $8d code! Thanks for any advice!



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David Tuschhoff
1991 RS Camaro M5
A SuperRammed, TPIS,
Ross, AFR, Scat, Crane,
CompCams induced 355!
My f-body page!

 

PE means power enrichment. Those are the tables to concentrate for "extra fuel and spark" in WOT mode. BUT, make sure that your VE tables are good first. If you are not near INT values of 128 (when your BLM is locked at 128), then concentrate on those first. No point in adding more fuel if you are overly rich. And if you are too lean, you should fix that too.

You can control when you go into PE mode by the table that defines at what %TPS you must be at, depending on the engines RPM. Also, PE can occur if your engine is very hot. This is the "PE at minimum coolant temperature" in the "Constants Table". This is primarily for "hot restart".

As for the 02 mVs, forget it. The stock 02 sensor is not accurate enough.

 

How can the BLM or the INT be anything other than 128? The computer doesn't read off the O2 and make corrections at WOT or open loop.

Not accurate enough for what? I agree that the stock O2 isn't dead on but it's a damn good reference, right. Basically my O2 was around 810mv, which told me it was running fairly lean. Pulled a plug and sure enough, white tip verfied this.



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David Tuschhoff
1991 RS Camaro M5
A SuperRammed, TPIS,
Ross, AFR, Scat, Crane,
CompCams induced 355!
My f-body page!

 

When you are in part throttle, your BLM/INT are not at 128/128 UNLESS they are bang on (which is rare). The BLM (stock) can vary from 108 to 160. The INT can vary even wider. I have seen it hit as low as 80. At 108/80, you'll trigger SES code 45.

By locking the BLM to 128, you can actually see the difference from "optimal" 128 with the INT. This is how when you are "tuning" the eprom, you can determine what adjustments to make to the VE tables.

At WOT, the ecm relies solely on the tables and if they are NOT at 128/128 at part throttle, they are off at WOT. A scan tool will always read 128/128 @ WOT; but this does not mean they are "optimal", it means it is relying on the tables, whether they are accurate or inaccurate. It is ONLY at part throttle that you can see the difference and use this to guage the changes needed to your VE tables.

As for the O2 sensor, it was never designed to work accurately at those levels. It was designed to work as a "switching device" around .450 mV. The further the O2 sensor reading is from .450 mV, the less accurate it is. The only O2 sensor that is designed to be accurate at high mV readings is a Wide Band O2 sensor.

Do a search on some of the older posts on the PROM Board on "O2 Sensor" and you can read up on it. There is a lot of good info on that subject and it will enlighten you on the entire subject.

[This message has been edited by Glenn91L98GTA (edited February 12, 2001).]

 

I never said they were. But at WOT and open loop they are.

I have already tuned my part throttle and now I'm trying to tune WOT. I made some adjustments to the PE tables last night and was getting better results. O2 was around 850mv.

I realize this. This is why we check our plugs and scan the computer to see how the engine is running at WOT. With this information I am trying to adjust accordingly which in my case, I am trying to add more fuel.

So, if your blowing black smoke out the tailpipe and the O2 is reading 1000+mvs, it's not reading correctly? Yes the Wide Band is the best way to go for accuracy, but I still believe the stock O2 is at least good enough for a reference.

I will, but you can't tell me it isn't a good tuning aid, right!


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David Tuschhoff
1991 RS Camaro M5
A SuperRammed, TPIS,
Ross, AFR, Scat, Crane,
CompCams induced 355!
My f-body page!

 

David,

The standard O2 is a switching device only ... rich or lean. You are attempting to use is as a device for determining how rich or how lean. It is not accurate enough to use for that purpose. Take a look at a response graph for the standard O2 sensor and then you will see what Glenn and I are talking about. The main problem is that our cars have no real way for use to digitally determine how rich or how lean. However, we do have O2 volts and we therefore are EXTREMELY tempted to use O2 volts to guage how rich or how lean. It is even difficult for me. However, you must keep it in your mind that the O2 sensor will not give you an indication as to how rich or how lean. Grumpy had the best example of this when he did a side by side comparison where his stock O2 sensor was reporting a rediculously low value even though his wideband O2 was showing a 12.x AFR. Again - take a look a standard O2 response graph and then this will all make sense. I had a hard time understanding this one until I saw a response graph of the stock O2.

Tim

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• Program your own PROMs!. Read my article to get started!
• Research and Experiment before asking questions.
• This is not a chip store. Go to the classifieds if you want someone to sell you a chip or give you a BIN.

TRAXION's 1990 IROC-Z
Best Time = 12.244 @ 112.51mph (1.778 60' / 7.819@88.32mph in the 1/8)
All Natural. No Force. No Drugs. Stock Bottom End. Stock Body Panels.
Gunning for NA 11's with bigger cam, bigger stall, and bigger exhaust.
-=ICON Motorsports=-
Moderator: PROM board at thirdgen.org

 

The oem sensor will tell you exactly when you cross from 14.7:1 going rich or lean, PERIOD.

Obviously black smoke and 1000mv is rich but HOW rich?? 7.5, 8.0. 8.1?.

Once tuned you can record what YOUR car runs best at, and use that for a GENERAL REFERENCE. Other then that expect to be be parts needlessly.

I played the O2 voltage game.
Don't always work.
They are temp sensitive, backpressure sensitive, and some detergent packages can alter the way they work.

 

The big thing with the standard O2 is to not trust it as gospel. You've got the right idea about checking the plugs. That's the real window into the cylinder to see what's happening. What these guys are pushing is the fact that at WOT, O2 sensor volts do not correspond to a definite A/F ratio.

 

Ok, so how are you guys tuning your WOT?



------------------
David Tuschhoff
1991 RS Camaro M5
A SuperRammed, TPIS,
Ross, AFR, Scat, Crane,
CompCams induced 355!
My f-body page!

 

Like everybody else that has a scan tool (regardless if they don't "trust" the stock O2 sensor), I use the O2 reading to get a relative comparison. Of course, 1/4-mile trap speed (or running on a dyno) is the best way to look for max power. The stock O2 sensor isn't a switch in the strictest of definitions since its output can be graphed to compare AFR and millivolts. Granted, the curve is very biased to giving accurate readings around 14.7:1, but it is still possible to tell if a change made it run richer or leaner. On this note, from what I've seen/read/heard from a lot of other people, 850 mV is a little lean as your plug reading verified...

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Greg Westphal
'87 IROC 305TPI/A4

 

READ YOUR PLUGS! thats the best way to tune for wot, BY FAR (fine tune with some device to measure acceleration improvement, what ever it is)

It takes some practice reading plugs to even know what you are looking at.. ive been looking at mine for months.. when i first started out I was under the mistaken assumption that the plug porcelain was supposed to have a real discernable color to it
WRONG
thats usually a bad sign if you can pick off a color right off the bat without looking real close... your "white" plugs could be bang on
in my combination and in my experience my car runs its best with plugs that have hardly any coloring at all. Pump gas is not plug reading friendly. today i did some plug reads and im pretty confident my tune is very close.. you can only see but the FAINTEST (like hold it up to a really bright light and look real close) beige coloring on the nose. Any richer than this and performance drops in my application. Always keep an eye out for edge rounding of the center electrode, overheating, and specs showing detonation before even concerning yourself with the color. Using this technique did more for me than the stock o2 ever has, showed me things id never have thought of, like adjusting my plug heat range, and the fact that i was infact far too rich on the top end despite the stock o2 saying otherwise, and knocking the corners off the center electrode, too much timing.. all bad stuff

I looked at what my o2 was doing the other day WOT just for the hell of it and it showed high .6's and low .7's all the way up

if i were you id just put down the scantool and rely on more traditional methods for this facet of engine tuning. They are far more effective, believe it or not.

 

You gotta get BLM's around 128 before you start to do other PROM changes and engine tuning. If not, the GM ECU logic will never be cooperative. Yeah, youcan mask things by being overly rich, which is what will happen with plug cuts, but the can tool is your friend. Plug cuts at WOT are useless for 99.9% of your driving, as most people can figure out for themselves.

 

By time vs distance

I made a little in car timer from $50 worth of RS bits.

Used a stop watch and ran off of the VSS input. It ignored the first 3 tire rotations, and then counted 100 revolutions and stopped the watch, so I had my own in car 600' drag strip.