Reading plugs to tune WOT

I have been making WOT throttle runs then immediately driving back to my house to pull a spark plug.

Q1: Will 5 minutes of neighborhood driving change the color of a plug enough to not know whether I'm too hot or too rich?

Q2: Anyone else pull the plugs and use that as the final say in tuning?

I have been watching the Scanmaster, making Datamaster logs at the same time to get a better feel for what is going on. I use all these collectively and make my tuning changes with as much info as possible, but it seems to me the plugs are more accurate - they have a front row view of the combustion chamber :).

Ryan

My plugs are still bright white, and I have +16% in the PEvsRPM tables. What is the deal?

Supposedly the only way you can use the plugs to see mixture on a fuel injected car is to shut the engine off before you let off of the gas.
If you drive it at all at part throttle the plugs should clean up.

Ok, let me say this...

I have gone from subtracting 2% in the PEvsRPM table to adding 50% noticing NO difference. That is not a typo.

It seems like my car is either:

a) Not going into PE mode. The BLMs DO lock to 128 (I am running the BLM locker program).

b) The injectors are maxed and just can't put out enough fuel (doubtful. I should be under 350rwhp).

c) Fuel pump - I'm running a brand new racetronix kit

d) Mechanical problem - car runs PERFECT during part throttle (BLMs are dialed in), and it idles nicely.

e) The cam I put it is not what it is advertised

I'm just thinking out loud here...

Any ideas?
Ryan

Hmm...
Don't know what to tell you. When you added all that fuel did the car feel like a slug?
And what do you mean you noticed no difference? Just from your butt-o-meter or are you trying to watch O2 voltage or something.

Again, the only way to correctly set up your wot pe fueling is with a wideband and on a dyno. If that is not available to you, then I suggest you get it to a track and watch mph as you tune. Mph is your best indication of horsepower. So that will work fairly well too.

Originally posted by Dan K
Hmm...
Don't know what to tell you. When you added all that fuel did the car feel like a slug?
And what do you mean you noticed no difference? Just from your butt-o-meter or are you trying to watch O2 voltage or something.

Again, the only way to correctly set up your wot pe fueling is with a wideband and on a dyno. If that is not available to you, then I suggest you get it to a track and watch mph as you tune. Mph is your best indication of horsepower. So that will work fairly well too.

Purely buttmeter. However, the O2s went from low 900s to 940s (10% PEvsRPM - 50% PEvsRPM).

It just doesn't seem like the car is adding the fuel I'm telling it to. With that much fuel I would figure the car would be a turd up high and the plugs would be BLACK (They were black with the stock tune).

Right now the car pulls about like stock up to 6k, then it feels like ts out of its power after 6k. I know the only way to know what is actually going on is to put it on a wideband O2. However, if its not adding any fuel right now, I need to figure out why it won't put more fuel in before I waste money on the dyno to find I have mechanical problems.

Edit: I may throw a FP gauge on and watch it...

Ryan

Wideband is the way to go, although you can get close by reading the plugs. You have to shut it off at the rpm you want to read it at and coast to wherever you are going to pull the plugs.

The blms will only lock at 128 if the pcm didn't have to add fuel to get the afr right, from what I see. Don't know if the blm locker overrides this or not.

Good luck, Mike

Originally posted by 96-speed
Ok, let me say this...

I have gone from subtracting 2% in the PEvsRPM table to adding 50% noticing NO difference. That is not a typo.

It seems like my car is either:

a) Not going into PE mode. The BLMs DO lock to 128 (I am running the BLM locker program).

b) The injectors are maxed and just can't put out enough fuel (doubtful. I should be under 350rwhp).

c) Fuel pump - I'm running a brand new racetronix kit

d) Mechanical problem - car runs PERFECT during part throttle (BLMs are dialed in), and it idles nicely.

e) The cam I put it is not what it is advertised

I'm just thinking out loud here...

Any ideas?
Ryan

Ryan: You need to know the injector pulse widths to further analyse this situatiuon. If it's over 80-85% you are maxing out your injectors. If it's under, then you need more pulse width. The best way to get this if you maxed out PE v rpm v. load is to go back to 0% in the PE table and "lie" about the motor size. Give it another 150ci or so to be sure the change is in the right direction. This should cause the ECM to command longer pulse widths at WOT. You can also add fuel in the PE v temp v load table, at least for testing purposes. In general, it's best to reserve this table for making changes related to operating temp (ie treat it like a choke), but it can be used for long term tuning as well. Makes changes only in the normal operating range and keep in mind not to beat on it when it excessive hot or not yet fully warmed up.

You also need to check your fuel pressure and see that is isn't dropping under WOT. If it is, you need more pump or have a defective regulator.

Rich Krause

Rich: I have watched the FP and it is good all the way up. I don't have the datamaster log with me, but I'm pretty sure my injector DCs were above 85% (maybe by 1-2%).

I will have better info tomorrow when I can look over them again.

I will also try what you suggested.

Thanks for the replies guys.
Ryan

Originally posted by 96-speed
Rich: I have watched the FP and it is good all the way up. I don't have the datamaster log with me, but I'm pretty sure my injector DCs were above 85% (maybe by 1-2%).

I will have better info tomorrow when I can look over them again.

I will also try what you suggested.

Thanks for the replies guys.
Ryan

I have seen injectors operate erratically at >80-85% duty cycle. If you aren't seeing a richer AF ratio with the programming changes you are making, this is a possibility. You could try raising the FP (if you have an adjustable AFPR) and backing off on the fueling in the PCM.

Rich Krause

Originally posted by rskrause
I have seen injectors operate erratically at >80-85% duty cycle. If you aren't seeing a richer AF ratio with the programming changes you are making, this is a possibility. You could try raising the FP (if you have an adjustable AFPR) and backing off on the fueling in the PCM.

Rich Krause

i agree with rick i would look at it on datamaster and look at the duty cycles and see how high they are.

but can you tell me how to lock the blms im using tuner cat.

The only bad thing about datamaster and it's injector duty cycle calculation is that I've heard it's not quite accurate.
Don't know whether or not that is actually true though.
Maybe Rufus could help?

I've seen some duty cycle numbers come out of DataMaster that don't seem to make any sense at all.... 120% on a bolt-on motor???? Any time I have seen this in someone's data, I have suggested that they ask TTS to explain it, but so far no one has done that. The guy at TTS seems more than willing to talk about things.....

When I set my PEvsRPM table ridiculously high (50% at 6k) I saw 110% DCs.

My guess is that what the pcm computes the inj DC to be is simply that: a computation. How much fuel is actually being supplied is only detecable by a wideband O2 sensor.

Makes sense to me, but I could be a little off.

Ryan

Originally posted by 96-speed
When I set my PEvsRPM table ridiculously high (50% at 6k) I saw 110% DCs.

My guess is that what the pcm computes the inj DC to be is simply that: a computation. How much fuel is actually being supplied is only detecable by a wideband O2 sensor.

Makes sense to me, but I could be a little off.

Ryan

Ryan: obviously, the injectors can't be open more than 100% of the time. But if the PCM is commanding a >100% duty cycle, there's a problem. You can't even tell if the injectors are appropriately sized, because most injectors will not operate reliably at >80-85% duty cycle. This is not just "urban legend". I have seen it, many times. You need to get the duty cycle down to the 80% range and see if it's rich or lean. If it's rich, back off the PE v. load v. rpm. If lean you can either raise the fuel pressure or go to larger injectors.

Rich Krause

Originally posted by rskrause
Ryan: obviously, the injectors can't be open more than 100% of the time. But if the PCM is commanding a >100% duty cycle, there's a problem. You can't even tell if the injectors are appropriately sized, because most injectors will not operate reliably at >80-85% duty cycle. This is not just "urban legend". I have seen it, many times. You need to get the duty cycle down to the 80% range and see if it's rich or lean. If it's rich, back off the PE v. load v. rpm. If lean you can either raise the fuel pressure or go to larger injectors.

Rich Krause

Hey Rich. I sent you an email last night that had some baseline times/mph and some info. Did you receive it?

Ryan

Originally posted by 96-speed
Hey Rich. I sent you an email last night that had some baseline times/mph and some info. Did you receive it?

Ryan

I'll look for it again, but I don't recall seeing it. Can you re-send?

Rich Krause

Sent..thanks.