I plan to go to a local shop soon for a dyno pass or 3,
Being i do not own a WB02 yet i want to tune using theirs.
My question is using PE F/A ratio vs. rpm what conversion do i use for making moves ? For instance say my car is overly rich at
4000 rpm 11:1,do i change that part of table by the amount in % i am from 13:1? so current value=7.8 would new value be 9.2?

Can anyone help me on where to buy a WB ? ive searched and cannot find much info other than building your own,and after seeing the parts list i am very ,very intimidated.

Thanks for any help.

 

Anyone? Anything?

 

PE. is Power Enrichment, putting a 10 in there would increase you AFR 10%. Meaning an exiting 14:1 with no PE, with the addition of 10% would be 12.6..

Rainbow electronics makes little kits of electrical things you can assemble, might look them up and try a simple kit or two to get the hang of things. The DIY-WB was designed for the average guy to assemble. It's well worth at least trying, to do. If in doubt don't get the sensor till you get a WB to pass the assembly test.

 

If you don't want to build your own WB, then perhaps 'Lambdaboy' could be an interesting alternative (No, I don't have one myself). It's considerably less expensive than other poducts I have seen.
http://www.lambdaboy.com/main.html#PRODUCT
A more sophisticated and expensive alternative:
http://www.mwignitions.com/uego.htm

 

Thanks guys,Will look a little further into building my own
but after that parts list and seeing how many guys say they cant get theirs to work just a little scared.

As far as the PE adjustment ,does the PE vs. coolant temp have no affect on open loop full throttle? ive seen some say it does
but recall glenn saying it does not?

Thanks againg for any help.

 

Let me answer your question with another question. What do you (or the "others") think the "PE %Change Air/Fuel vs RPM" table does?

If you doubt me, make changes to either table and monitor your injector Pulse Width. Then tell us what the result from playing with each table does.

 

As for calculating the New AF ratio you will get when you add fuel via the "PE %Change AF vs RPM", most guys believe the following formula is the correct one: (in all cases %change should be expressed as a proper decimal like 10% = .1 or 100% = 1)

New AF Ratio = 14.7 - (14.7 x %Change)

This formula is incorrect be cause if you add 100% fuel, you should have a New AF ratio of 7.35:1. If you plug 100% into the above formula, you end up with an AF ratio of 0, which is impossible. Conversely, if you LEAN the %Change with -100%, the above formula will yield an AF Ratio of 29.4:1 when the correct answer is "infinity" since leaning by -100% results in no fuel.

The proper calculation is the following:

New AF Ratio = 14.7/(1+%change).

Now if you plug in 100% added fuel, you get the proper 7.35:1 ratio and if you lean it by -100%, you get "14.7/0" which is "infinity" or "0 divide error". Because you got no fuel.

But ALL of this is all theoretical as it ONLY works IF you are running a proper 14.7:1 at 128/128 perfect. If you aren't, then it is highly unlikely that you will see the calculated New AF Ratio when you hook up a WB O2 sensor to it.

This is why proper tuning of the Part Throttle VE tables is emphasized so much. Then when you add fuel via the PE table you will probably get an actual AF ratio that is close to your calculated AF Ratio.

This is also why taking your car to a chasis dyno, hooking up a WB O2 sensor and then playing with the "PE %Change AF vs RPM" table to get max HP is not recommended. You've now tuned you eprom to get max HP, but only at that ambient air temp AND elevation. Change the elevation, you will use a different "cell" in the VE table because your Kpa is different. And if you took a "short cut" by only tuning via the "PE %Change AF vs RPM" table, it is highly unlikely that can use the same %Change.

This is why you MUST tune as much of the part throttle VE tables as possible. Then when you add 12% to get 13.1:1, you will get 13.1:1 at ALL elevation levels - not just the elevation that you "tuned" at the chasis dyno.

 

Well thank you,
Please do not feel so doubted!! I never meant any disbelief by saying that. Ive been tuning a little while now and getting much better by the week but some areas i have yet to see (like use of a WB) and am still learning and plan to continue....
Ive been using plug cuts and performance data and feel ive done pretty well to this point ,is my VE table perfect yet? NO
but there are still many areas of the VE table that are hard to get data on living in PA. hills everywhere.
Do i plan to make it perfect? YOU bet.
Moral of the story - Dont always just answer a question because you feel slighted, answer because you want to help.

Thanks again.

 

Glenn,

I take it your statement is true for all ECM's(ie7747), correct?