1G SUPER Knock!

[holland]

Hey everyone, I tried to post this in the "tech" forum under engine managment but it wouldnt let me.

So here's the skinny.... my car has 1000 miles on a new motor, its been running fine at 7psi... i turned it up to 14psi... still running great but after about a week of that I developed a boost leak in my BOV gasket. I needed to replace my 1G BOV anyways so I bought a new Greddy, got the new flange welded up and its ready to rock.

I started up the car, drove it down the road and it ran great at 12 psi. Today I took the car back out and drove it about 50 miles on the freeway and I noticed everytime I'd get close to 5k rpms it would stutter real bad and loose lots of power. It didnt feel like a boost leak, it felt more like the fuel was cutting out.

So tonight I plug in my laptop and run DSMLink and low and behold I'm getting knock like a crazy man! 15 degrees of knock at 4000 rpm, AF = 11.2 and the boost is at about 4psi... wtf, how the hell could I be getting THAT much knock at this low of a boost.

The motor is all new, the knock sensor is new... I'm stumped!

Here's the link file for all you fellow Linkerz

 

[98evoIIIpwr]

Can you give us some examples of what setup you are running. That might help in decipering what your problems are. Log looks kinda crazy.

Do you have any 3rd gear pulls?

 

[98evoIIIpwr]

Are you using a WB 02 or are you using the link to guesstimate your A/F ratios? Considering you have a MAF-T you might be way off.

 

[holland]

Here's my list of mods:

Walbro 225, AEM Fuel Rail, Aeromotive FPR, 850cc injectors, 3" GM MAF w/ Translator, front mount Intercooler, cold air intake, Turbonetics T04E 50 trim, Bullseye housing, 2.5" exhaust, DSMLink, Greddy Profec B Boost controller, Mits Blow Off Valve, Greddy Temperature gauge for exhaust manifold, Greddy Boost Gauge, Greddy Turbo Timer, ACT 2600 clutch, Fidanza Flywheel, Magnecore Wires, NGK plugs.

No, I'm not running a WBO2 unfortunatly but the car was running great w/ no knock for the past month w/ the old BOV... that was before the BOV developed its leaky gasket.

I dont have any 3rd gear pulls but they look the same as the log I posted. After I realized I was getting soooo much knock I just decided to park the car before I blew up this motor too...

 

[holland]

Oh, one slightly important bit of info I forgot to ad is.... whenever I'm just at cruizing speed or accelerating, the check engine light comes on, but as soon as I let off the gas it goes off.

I tried checking the codes in Link but nothing ever shows up. Link says theres no error codes but the light keeps coming on.

 

[elfroggo]

I don't know about the other things, but having the CEL flash is due to knock. It's a feature of DSMLink

 

[olmytsi]

Exactly, dsmlink flashes the light if more than 5 degrees of knock is seen. Yo can change it under ecu>dash.

I recommend you make sure your maft is set for 450s, zero out the fuel sliders leaving the global and deadtime alone and relogging. Also, make sure your knock sensor is not loose. Lastly, do NOT rely on the dsmlink estimated a/f rato.

 

[Dark_Horse]

My advice is to remove the GMAFT unless you have a WB O2 and/or a 3.5 or 5 bar MAP sensor. Without calibrating the MAFT either with a WB, MAP sensor or on the dyno, your airflow readings can be way off.
There is a huge thread on DSMlink about how to properly run a 3" MAF/Translator.

 

[holland]

Thanx for the advice guys, I've already done my homework on the MAFT and had it all calibrated and tuned good. Like I said, the car was running great before the BOV seal went bad.

Here's a question though, does anyone know if the translator itself needs power to keep its memory? I had it unplugged for about a week while I was having a new intake pipe welded up. Does anyone think it could have lost its settings by unplugging it?

 

[olmytsi]

My translator has knobs so whether it looses its memory or not, the settings will always be where i have them set. But i have version 1.3 so i dunno how the new ones are.

 

[holland]

My translator has knobs so whether it looses its memory or not, the settings will always be where i have them set. But i have version 1.3 so i dunno how the new ones are.

I dont know what version mine is but it has knobs also... hmmm... well, all I can do is re-calibrate the translator and see if that fixes anything.

If anyone has any other ideas please post em!

 

[olmytsi]

What exactly did you do when calibrating the maft? You're supposed to do it in dsmlink, not with the translator.
I see that your airflow sliders are all at 0 except the 150hz (which is all the way down) so you definitely did not calibrate it properly.

 

[holland]

What exactly did you do when calibrating the maft? You're supposed to do it in dsmlink, not with the translator.
I see that your airflow sliders are all at 0 except the 150hz (which is all the way down) so you definitely did not calibrate it properly.

In the translator I set the injector size to 450s and zero'd out the idle, mid & wot knobs. I put my airflow in link like that because that was the only way I could get my LTFT-Lo and my STFT to be happy.

The car has been tuned like this for the past month and has been running and idleing good.

I just popped the lid on my translator and the knobs are still setup the sameway, I'm lost on trying to figure out why this knock has started to happen.

 

[olmytsi]

Add fuel in dsmlink and relog.

 

[holland]

Add fuel in dsmlink and relog.

Ok, I did some retuning of my airflow tables and the idle seems to be right on the money.

The first run file is right after the idle tune, it goes through 3 gears as much as I could. I got the car doing barely 40mph.

The last log file I changed my global fuel settings to 47% instead of 57% hopeing to add fuel through the whole rpm range. As you can see from the log, my knock issues stayed the same.

Whats really weird is how this whole knock thing started happening. I drove to my grandparents house which is 30 miles outside of town. I started my trip and the car ran fine up until about 5500 rpm, it would sputter. Then the check engine light would come on in that rpm range. As I drove it back home the sputter would start happening sooner in the rpm range, at about 4000, then so on and so on as I drove it home.

Now I cant get past 2500 rpm without getting some crazy knock. I'm not sure what would cause the car to slowly increase its knock.

 

[olmytsi]

Again, check the knock sensor in the back of the motor to see if it is loose or going bad. I don't know what exactly is causing the knock but it's really high so something is definitely going on.

ps: do a compression test too just to see what state the motor is in.

 

[90blacktsiawd]

Have you done another boost leak test since you replaced the bov seal? It could possibly be rich knock. If you had a leak and it's conitued to get worse over this time period that could explain why the stuttering happens sooner and sooner.

 

[holland]

Have you done another boost leak test since you replaced the bov seal? It could possibly be rich knock. If you had a leak and it's conitued to get worse over this time period that could explain why the stuttering happens sooner and sooner.

I need to do another boost leak test, but after I installed the new BOV and seal it ran and held boost good. But I definitly need to do a boost leak test again just to make sure there are no leaks.

But what is rich knock? I've never heard of that before

 

[90blacktsiawd]

Rich knock is when your dumping an excessive ammount of fuel into the combustion chamber which causes pre ignition of the fuel. I've had the same thing happen before and it sounds like the same symptoms that your having with the stuttering.

 

[1990talon]

I had a bunch of knock when I had a boost leak. I split my intercooler open. I could be that a boost leak occured and progressivly got worse. I belive rich knock is when way too much fuel is being put in the cylinder and when it compresses it combusts before the spark due to too much fuel?

 

[1990talon]

Rich knock is when your dumping an excessive ammount of fuel into the combustion chamber which causes pre ignition of the fuel. I've had the same thing happen before and it sounds like the same symptoms that your having with the stuttering.

Beat me to it.

 

[holland]

oh ok, I see.... that actually explains alot. I've been adding more fuel thinking it was a lack of fuel that was causing the knock. The car started to spray fuel out the tail pipe last night I ended up adding so much.

so theoritically I still have a boost leak then and when I fix it, it should then fix the rich knock effect I'm getting? Is the only thing that can cause rich knock a really bad rich tune or a boost leak?

 

[90blacktsiawd]

Theres no garuantee that you still have a boost leak, but it's a very good practice to do a leak test after you do anything with the intake track.

If that is the case then fixing your leak SHOULD take care of it. But at the same time you've been messing around with the fuel and dumping even more in.

I can't give you a definitive yes or no about your last question. The only things i can think of off the top of my head would be an excessively rich tune or boost after the mas for causes of rich knock.

I'm going with what my past experiences are in this situation.

What happens with a boost leak after the mas is that the mas is counting all this air coming into the car. When there's a leak after the mas your loosing air thats already been counted and fuel has been supplied for. Lose enough of that counted air and you start to run really rich really fast.

 

[90blacktsiawd]

I might have missed it but i don't see wether or not you have your mas in a draw through or blow through setup.

Another thing, have you checked to make sure your plugs are gapped properly and are still in good condition? What about the wires?

 

[holland]

I might have missed it but i don't see wether or not you have your mas in a draw through or blow through setup.

Another thing, have you checked to make sure your plugs are gapped properly and are still in good condition? What about the wires?

I have the mas setup as a blow through. There's only two places after the mas that could be leaking, the silicone and the TB gasket. Both of which I took off when I had the new bov flange welded on. Time to borrow my friends air compressor again!

The wires should be good, they were before but then again that doesnt mean anything! haha. I definitly need to check the plugs, I could have fouled them out from the previous boost leak.

The boost leak I had before was so bad the car wouldnt hold any boost. In fact, when I did the leak test I had to turn the compressor engine on and let it run just to keep constant pressure in the intake system.

Thanx for all the helpful advice. Time to do another boost leak test and change out my plugs!