STILL getting knock. How???

[AlphaAssault]

Mods:
s16g @ ~13.5psi
Denso 150lph fuel pump
fuel pump rewire

TMO logger:
20-30 knock
.80v CO2 sensor
9-10 timing advance

Im getting knock above 3000 RPMs, despite the fuel mods. 13.5 psi isnt that high for a s16g, and Im still getting considerable knock. How is it possible with a rewired 150lph to be running lean at 3K RPMs? help?

 

[LiquidX]

What octane fuel are you running?

 

[AlphaAssault]

93 octane.

 

[Ceddy]

.80 volts is pretty lean, want it around .90 volts.

Whens the last time the fuel filter was changed?

 

[AlphaAssault]

.80 volts is pretty lean, want it around .90 volts.

Whens the last time the fuel filter was changed?

Four months ago.

 

[the_mork]

20-30 counts sounds more like phantom knock. You have a couple of options for diagnosis, you can either fill up with some 110 octane and see if the knock persists or you can build a det can so that you can listen for knock events on your own. Basically if you still knock on race gas or your det can doesn't show real knock then you need to determine why you are getting phantom knock. It could be something banging around like a bracket or your exhaust or you could need a new ecu or knock sensor.

 

[AlphaAssault]

20-30 counts sounds more like phantom knock. You have a couple of options for diagnosis, you can either fill up with some 110 octane and see if the knock persists or you can build a det can so that you can listen for knock events on your own. Basically if you still knock on race gas or your det can doesn't show real knock then you need to determine why you are getting phantom knock. It could be something banging around like a bracket or your exhaust or you could need a new ecu or knock sensor.

but Im still running lean. the fact that the O2 sensor is reporting only .8V is pretty good evidence for the knock being real.

What about timing? its the only thing I could think of that I havnt really messed with. could a dying CAS be the cause; or maybe one that isnt adjusted properly?

 

[jeffo]

How are you reading that 9-10* timing? The only way to accurately check the timing is as per the VFAQ with a timing light. The 1G maps are already rather aggressive, so running more than the stock 5* BTDC will cause knock issues.
Also, since you don't know all the mods of the previous owner, its possible that they used higher compression pistons for a rebuild. Many guys opt for the 2G 8.5:1 pistons, which will also cause knock issues under boost if not accounted for.
Do you have any ideas why your O2 volts is so lean? Is the MAS hacked? Does the car have an AFPR? You don't have an AFC leaning things out? Is the ECU stock?
PK usually happens when the car isn't in boost. My guess is that you have real knock, not PK.

 

[AlphaAssault]

How are you reading that 9-10* timing? The only way to accurately check the timing is as per the VFAQ with a timing light. The 1G maps are already rather aggressive, so running more than the stock 5* BTDC will cause knock issues.
Also, since you don't know all the mods of the previous owner, its possible that they used higher compression pistons for a rebuild. Many guys opt for the 2G 8.5:1 pistons, which will also cause knock issues under boost if not accounted for.
Do you have any ideas why your O2 volts is so lean? Is the MAS hacked? Does the car have an AFPR? You don't have an AFC leaning things out? Is the ECU stock?
PK usually happens when the car isn't in boost. My guess is that you have real knock, not PK.

I agree, I think the knock is real. Since I wrote that description, i have pretty much figured out on my own what mods have been done. I have been checking timing with my laptop and TMO software. It seems to work well; though i have no other way than the logger to tell, so timing *could* be off. That timing reading was during the WOT pull, not at idle; though i took a timing reading at idle, and it was at about 8*-9*. I have no idea why I am running so lean; the engine is getting enough fuel to drown a horse. At least, it has the *potential* to drown a horse, obviously the fuel isnt getting to the engine for some reason. to answer your other questions:
1) I dont know which pistons are in it. is there a way to tell?
2)The lower honeycomb of the MAS has been removed.
3)No AFPR, No AFC.
4) Stock ECU with a sticker suggesting it has been repaired once in its lifetime.

 

[Calan]

Unfortunately, you can't really tell much by the O2 sensor voltage. Theoretically you could shoot for .85v, .9v, etc... but in reality there really isn't much correlation between a steady-state voltage on a narrowband O2 sensor and a certain AFR in the cylinders. There is just too much variation. As an example, my front O2 cycles normally and keeps my closed-loop AFR at 14.7... but during open loop it may go to a steady .75, while my WB reads 10.5:1.

One thing I would check for is exhaust leaks around the EM and turbo-to-EM flange. A very small exhaust leak can affect the O2 sensor quite a bit.

Also, pull your plugs and read them. See if they show signs of knock, and whether you are really running lean or rich.

As for the knock being real or not...try taking the car almost to redline in second or third gear without getting into boost, and see if you still have the same amount of knock at the same points in the RPM range.

 

[AlphaAssault]

Unfortunately, you can't really tell much by the O2 sensor voltage. Theoretically you could shoot for .85v, .9v, etc... but in reality there really isn't much correlation between a steady-state voltage on a narrowband O2 sensor and a certain AFR in the cylinders. There is just too much variation. As an example, my front O2 cycles normally and and keeps my closed-loop AFR at 14.7... but during open loop it may go to a steady .75, while my WB reads 10.5:1.

One thing I would check for is exhaust leaks around the EM and turbo-to-EM flange. A very small exhaust leak can affect the O2 sensor quite a bit.

Also, pull your plugs and read them. See if they show signs of knock, and whether you are really running lean or rich.

As for the knock being real or not...try taking the car almost to redline in second or third gear without getting into boost, and see if you still have the same amount of knock at the same points in the RPM range.

Lots of good information here. I know how to read my plugs for richness or leanness, how do I read them for knocking?

 

[Calan]

Lots of good information here. I know how to read my plugs for richness or leanness, how do I read them for knocking?

Look for very small pitting around the insulators. If it's bad enough and has been going on for a while, you could even have cracked insulators or melted electrodes...although at that point I think you would have seen other symptoms.

Something else to check is your ignition. Misfires at WOT will show up as running lean. I fought this myself a few months ago; turned out to be a flaky ignition coil no matter how much I wanted to believe it was fuel related.

 

[AlphaAssault]

Look for very small pitting around the insulators. If it's bad enough and has been going on for a while, you could even have cracked insulators or melted electrodes...although at that point I think you would have seen other symptoms.

Something else to check is your ignition. Misfires at WOT will show up as running lean. Fought this myself a few months ago; turned out to be a bad ignition coil no matter how much I wanted to believe it was fuel related.

What are some things to look for with a bad ignition coil?

 

[Calan]

What are some things to look for with a bad ignition coil?

Lean readings at WOT

Just find someone with an extra set and swap them out. Really simple to do and one more thing eliminated if it doesn't improve. Throw in a new set of NGK BPR6ES plugs gapped at .028" and some new NGK plug wires while you're at it.

 

[jeffo]

I have been checking timing with my laptop and TMO software. It seems to work well; though i have no other way than the logger to tell, so timing *could* be off. That timing reading was during the WOT pull, not at idle; though i took a timing reading at idle, and it was at about 8*-9*

As I said, the ONLY way to check timing is with a timing light, as per the VFAQ instructions:
Base Timing Adjustment
The ECU *assumes* that you have set the base timing to 5* BTDC with a timing light, so it reports timing based on that. If the timing is actually at 10* BTDC, the ECU still logs the same exact timing values, but you get lots of knock.
Also, if reason you are only seeing 9-10* timing at WOT is because the ECU is pulling ~1* for every 3 knocksum. The car would be MUCH faster if you would put the timing back to 5* and lower the boost.
Please borrow a timing light and check your timing.

 

[AlphaAssault]

no exhaust leak that I could find. Pulled the plugs and looked at them, they indicate that the timing is too advanced (entire ground strap is light gray; no timing band like there should be). was going to mess with the timing again today, but had to fix an electrical problem that cropped up. More updates as they come.

 

[AlphaAssault]

UPDATE: I adjusted the timing some, retarded it, and turned the boost down to stock (10-11psi). did a WOT pull to redline. NO KNOCK!!! well, almost no knock: got 1 count right around 3800RPMs, then none. timing didnt drop to below 17*, and the O2 sensor read pretty steady between .76-.78 volts. I think i might have FINALLY solved the problem. I think Im going to retard the timing just a bit more, then up the boost some, and see how those logs look. but before i do that, do these numbers look alright???

 

[PieEyedPiper]

Just curious, was the car faster like that? With the timing advance and less boost?

 

[Calan]

UPDATE: I adjusted the timing some, retarded it, and turned the boost down to stock (10-11psi). did a WOT pull to redline. NO KNOCK!!! well, almost no knock: got 1 count right around 3800RPMs, then none. timing didnt drop to below 17*, and the O2 sensor read pretty steady between .76-.78 volts. I think i might have FINALLY solved the problem. I think Im going to retard the timing just a bit more, then up the boost some, and see how those logs look. but before i do that, do these numbers look alright???

What do you mean by "I adjusted the timing some"? Did you put a timing light on it and set it to 5* as JeffO suggested (twice)? You really need to set the base timing to 5* BTDC, and leave it there. If you are just fooling around with it, you're probably hurting your overall performance and fuel economy more than you are helping it.

Not to sound negative, but you may not have solved anything. You could still have an ignition problem. As the boost goes up and cylinder pressures increase, more is demanded of the ignition in order to jump the gap under those higher pressures. At only 10-11 psi, you may be back down in the range of cylinder pressure that the ignition doesn't have a problem dealing with...which is ok if that's all you plan on running.

It could also be a similar issue with fuel supply. At the low airflow; no problems. But as soon as fuel demand goes up, your problem may rear it's ugly head again.

Then again, your ignition and fuel system may be fine. Just throwing out some things to keep in the back of your mind.

 

[diambo4life]

All that tuning using a narrow-band O2 sensor is useless. There is no excuse not to get a wideband. It's the single most important device for tuning your car.

 

[AlphaAssault]

All that tuning using a narrow-band O2 sensor is useless. There is no excuse not to get a wideband. It's the single most important device for tuning your car.

I never really needed one until now. the mods done to this thing were on it when i bought it. ive just been trying to get it running like it should. Now that you mention it, this might be next on my list of things to get.

What do you mean by "I adjusted the timing some"? Did you put a timing light on it and set it to 5* as JeffO suggested (twice)? You really need to set the base timing to 5* BTDC, and leave it there. If you are just fooling around with it, you're probably hurting your overall performance and fuel economy more than you are helping it.

Not to sound negative, but you may not have solved anything. You could still have an ignition problem. As the boost goes up and cylinder pressures increase, more is demanded of the ignition in order to jump the gap under those higher pressures. At only 10-11 psi, you may be back down in the range of cylinder pressure that the ignition doesn't have a problem dealing with...which is ok if that's all you plan on running.

It could also be a similar issue with fuel supply. At the low airflow; no problems. But as soon as fuel demand goes up, your problem may rear it's ugly head again.

Then again, your ignition and fuel system may be fine. Just throwing out some things to keep in the back of your mind.

I adjusted it the first time just to see if anything changed (which it did). since then, Ive timed it properly (to my credit, i was close with the first adjustment). Now, my first log after timing it correctly, i upped the boost to about 15psi. NO knock, but I DO get fuel cut now. People described it as hitting a brick wall; but for me its more like an intense bucking. The logger, however, shows that the injectors just STOP, hence: fuel cut. SO, out of the frying pan and into the fire. the fuel is there, so how do I keep the fuel cut at bay?

 

[steve]

the fuel is there, so how do I keep the fuel cut at bay?

First step is a pressure test to make sure the the airflow your MAF is reading is actually getting to the engine. Since you have the lower honeycombs removed you should already be showing the ECU less air than the stock MAF would.

Next step is some bigger injectors and something to tune with or get a EPROM ECU and disable fuel cut.

What size injectors do you currently have and what does the IDCs look like. If they are stock you have to be getting close to maxing them out.

 

[AlphaAssault]

First step is a pressure test to make sure the the airflow your MAF is reading is actually getting to the engine. Since you have the lower honeycombs removed you should already be showing the ECU less air than the stock MAF would.

Next step is some bigger injectors and something to tune with or get a EPROM ECU and disable fuel cut.

What size injectors do you currently have and what does the IDCs look like. If they are stock you have to be getting close to maxing them out.

My injectors are stock, but from a 2nd gen. How do you calculate IDCs? My logger (TMO laptop) only does Pulse Width as far as injectors are concerned; though I believe the formula requires pulse width and RPMs? also, Ive got a '90, i should already have an EPROM, though I have never checked. How do i disable fuel cut if I have an EPROM?

sorry for all the stupid questions, Ive never had to mess with the 'tuning' aspect of my car, only the 'maintenance' aspect

 

[steve]

How do you calculate IDCs?

You need to know two things, the injector pulse width and the RPM.
available time (ms) = (1/((RPM/2)/60))*1000
IDC (%) = (injector pulse width/available time)*100

IDC (%) = injector pulse width / (1/(RPM/1200))

You need the EPROM ECU to be able to change the software. DSMLink or a premade chip will have it disabled. If you want to do it yourself the location is listed on the DSM-ECU yahoo group archives.

 

[jeffo]

also, Ive got a '90, i should already have an EPROM, though I have never checked.

There is no truth to what some people say about 1990 cars all being EPROM-type ECU. I have a whole box full of non-EPROM 1990 ECU's to prove it. You really need to open it, and while you're in there make sure the caps have been replaced!