e-man

What should the O2 senser read at WOT? Also when you advance or retard the timing does it have any affect on total timing or does the ECM just use whats on the chip? If you could adjust total timing what RPM should it be at and how much is to much? Just enough before knock right.

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89 350 TPI,comp cam,edelbrock intake base,SLP headers,highflo cats,flomaster cat back,accel 300+ ign,ported plenum and runners,ported maf,auto w/shiftkit,cold air induction,AFPR,Ed wright chip,3.23 posie best ET 14.01@98mph without cam

[This message has been edited by e-man (edited February 22, 2001).]

theformula

850mv at WOT. But the best way to tune is by ear, and spark plug readings. There is no magic number. That is the BEST way to tune your own car.

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91 Formula
305 TPI 5speed
1LE/G92/WS6

Paxton SN92 polished kit, SLP airfoil, ported/polished plenum, March pulleys, Crane AFPR(43psi),Crane Gold 1.6rrs,MSD coil,MSD6AL,MSD boost-master,Holley 9mm wires,Ac delco R43ts plugs,custom chip,Ford SVO 24# injectors,Bosch O2sensor, Bosch in-line pump(w/stock pump), SLP 1 5/8" headers,SLP catback,short shifter,3:73s w/Auburn posi,170* t-stat,JET 195* fan switch, Macewen white face gauges, Autometer gauges, Zoom hi-performance clutch.

Grim Reaper

Only a Wide Band O2 sensor has the accuracy to rely on it for an accurate AF ratio. They are very expensive.

The stock O2 sensor is strictly a "switching" device around .450 mV. As you get further away from .450 mVs, it inaccuracy gets greater and greater, and its validity becomes less and less.

Lastly, one guy might find their best results at MUCH different O2 reading than another car with identical mods. This is how people discovered that the O2 sensor was not to be relied upon.

This is the bain of all us eprom burners. I can develop a very accurate VE (Volumetric Efficency) table all the way up to 100 kpa (max load). But Power Enrichment kicks in (commonly called WOT), you loose all your scan tool readings. You then have to rely on other means like the plug cuts, and listening for sounds (like detonation as you want to be as lean as possible, NOT RICH).

The ultimate "tuning tool" is your e.t. You can use a G-Tech or better yet, a good accelerometer to quantify various accleration points to do some tweaking of spark and fuel when in PE. But ultimately, e.t. and trap speeds is the last word.

The problem is, many guys are looking for (and relying on) a "technical solution" and completely forget the good old fashion methods. In this respect, guys who never had to work on a good old fashion carb never learn these techniques. In this respect I dislike EFI.

That is why I think EVERYONE should own a motorcycle for awhile. You only have carbs and have to rely on the "old fashion" methods and you learn to drive defensively. Too much reliance on scan tools these days. They have their place, but they are not the "end all to be all".

The ODB

I agree,
the accelerometer is the proper way to tune.

my camaro ran it's best at only .250mv in 3rd gear (not a wideband). Most people would say that's way too lean, but it loved it. Running that lean did make me have to pull the total timing back to 35 degrees, but the end result was more power.

ODB

Grim Reaper

Good point ODB. You really have to play with the AF ratio and spark @ WOT. Let the engine tell you what it wants and don't get hung up on numbers.

Dale Groah (an engine builder in Virgina) who does dirt track racing, was telling me that they are running 2 bbl iron head 350s(class restriction) and found max power at 32*. Oh yeah, making very high HP too. 500ish I think. I'll have to ask Dale again to confirm.

But you MUST play with AF and spark together. Don't get hung up on 36-38* if it doesn't want it. You'll just end up making it too rich and loose power.

mirage2991

yea I agree...my little experience on tuning showed me that more initial timing made my car run really well down low, but on top it was a dog, and I was loosing 1 to 2 mph...so now I run low timing (initial) which makes the car less responsive but the top end is so much better....so go with what the car wants

The ODB

mirage,
There are easy ways around that trade off. You are running a carb right?

Glenn, yeah those race engines are higher compression and very efficient. The optimal total timing has a lot to do with the fuel type and burn speeds for the given compression.