Knock - Only when +5 Boost is present??

[DSMWillyb]

I need some insight from some fellow tuners!!! Anything that could help is MUCH appreciated!! Thanks...

Modifications:

GM MAF (3.5")/ DSM MAF Translator/ 780cc injectors/ Walbro 255/ SteveTek Fuel lines/ AFPR/ 3" Exhaust/ FMIC/ 1G BOV - And a whole lot more that isn't relevant...

Settings:

MAFT - #8 on injectors (750cc) - all others are set a 0
AFPR - 37psi

Symptoms/story:

After installing the MAFT/MAF I datalogged and recieved 43 counts of knock. I also realized that my stock (450cc) injectors were maxing out on their duty cycle. With that realization I ordered some 780cc injectors from Extreme PSi. I also ordered a FP guage at this time... Once the injectors were installed I logged again - Same results, full knock - but only when in boost - greater than 5psi. My fuel pressure was down (~32psi @ idle) so I then ordered a AFPR (fullthrottlespeed). Once the AFPR was installed and was set (~38psi @ idle) I again logged, and the same results occured. I have since replaced the Plugs (NGK BRP6ES) and the Knock sensor - still no luck....

I cannot think of anything else that would cause 'actual' knock (detonation)... But also by listening I here nothing that would cause the knock sensor to be set off (especially only when Boost is present)...

I am stumped!!! Has anyone esle had these symptoms??

Thanks Again

 

[kpt4321]

First, you won't be able to hear knock, so don't worry about it. The 4G63 doesn't really have audiable knock, it's normal.

Are you sure the car is tuned right? Have you datalogged it? Before you do anything else, you have to make sure it's tuned right.

 

[Ludachris]

Originally posted by kpt4321
Are you sure the car is tuned right? Have you datalogged it? Before you do anything else, you have to make sure it's tuned right.

Kyle, isn't that what he's trying to do by asking this question?

Will, I know what you're saying about trying to listen for things that may be causing false knock... but really, it's probably not going to be anything that you can hear - except maybe some lifter tick. I've noticed when I'm low on oil, the lifters are a little more noisy, and I tend to see knock more often and lower in the rpm's. But other than that, you probably won't be able to hear anything. I myself am trying to pinpoint a knock problem. I've changed out the knock sensor, O2 sensor, will be replacing my motor mounts, un-doing a welded exhaust hanger I have, and if none of that works, then maybe I'll just throw in my larger injectors and forget trying to solve the false knock.

 

[kpt4321]

If it's tuned so that is knocks badly, then I think it would be obvious that it's not tuned right....?

 

[Ludachris]

Originally posted by kpt4321
If it's tuned so that is knocks badly, then I think it would be obvious that it's not tuned right....?

I'm just giving you shit man - I believe he's thinking that the false knock is responsible for throwing his tuning off... but yeah, it would be helpful to know what tuning tool is being used and what the settings are so that we can see if there's an obvious setting which could be causing the problem.

 

[kpt4321]

Ok, cool. Sorry.

Back on topic: we don't even know if the knock is fake. We need to know about your tuning.

 

[Rogue_Ant]

What is your base timing set to? With that large of injectors, you may need to set is a couple of degrees lower then stock..



Rogue

 

[DSMWillyb]

Sorry for the confusion - here's some more information:

Things I have checked/replaced:
1. Spark plugs (NGK BRP6's and 7's)
2. Knock Sensor
3. Timing

Basically I am getting knock whenever I get into boost. But I don't understand why (see below)

Fuel trim settings:
Low - 86%
Mid - 82%
High - 90%

02 volt - .91 -.93 @ WOT

I do realize that these are not 'tuned' correctly at all... But I wanted to stay on the safe side (rich) until I get this knock problem figured out...

Thanks. Will.

 

[kpt4321]

Ok, now we are getting somewhere!

What kind of knock sums are we talking about? What manifold pressure, and what rpm?

What year car?


Edit: It's a 91, cool.

I bet you money it's because of the stock fuel and timing maps in the "turbo is spooling" area. Let me know what you are seeing for knock, rpm, boost, etc, and I will check it out.

 

[dsm1kenobe]

Set your base timing lower and see what happens. 2* btdc works well for me.

Are your lifters ticking? Do a motor or atf flush and while you're at it, use mccc to clean those lifters and carbon buildup.

Good luck!

 

[DSMWillyb]

Here's a log using MMCD:

Note: Fuel trims differ from previous posts...

Boost: Max 15psi (14B) the knock begins at ~5psi

RPM INJP KNCK O2R TPS INJD TIMA FTRL FTRM FTRH MAFS

2750 6.91 0 .93 63 16 29 107 89 99 396Hz
2906 7.67 7 .93 63 18 28 107 89 99 478
3281 9.21 43 .91 63 25 11 107 89 99 635
3500 9.72 43 .91 63 28 10 107 89 99 679
3718 9.72 42 .91 61 30 11 107 89 99 723
3937 10.5 42 .93 61 34 11 107 89 99 774
4125 12.3 41 .93 60 42 10 107 89 99 874
4375 13.0 40 .93 60 48 10 107 89 99 937
4500 13.5 40 .95 60 51 11 107 89 99 1018
4718 14.3 40 .93 60 56 10 107 89 99 1063
4687 1.27 26 .07 9.7 4.6 10 107 89 99 163


My lifters make very little noise (and yes I do know what lifter tick sounds like)... I have thought about doing the MCCC and seeing if that helps, but I have a hunch it isn't the problem...

 

[Rogue_Ant]

What is base-timing?



Rogue

 

[DSMWillyb]

Timing is @ 5 degrees...

 

[nine5raptor]

You need to get your TPS problem figured out for one...

 

[AL92]

Umm.no way you were maxing out 450 injectors on a 14b.I noticed also I had very high duty cyles on my car with the maft and 3 inch maf and 14 b set to the recommended settings for the injector size.I think as they say on translator boards that is just a rough guidline and very rich likely.
Your trims show its taking out lots of fuel.Your wot looks ok though.
So maybe you have rich knock.Not a chance you need those size injectors with a 14b .Maybe my new 50 trim.

Anyway yeah my car has some weird knock too.I plan on replacing lifters.Mine only tick when car is cold and then shut up and when the car is a bit down on oil.Found the new ones for like 130 US so get some when I do the new cams I plan on getting.

Some other ideas for knock that no one seems to mention..harmonic balancer pulley..hear its common for them to fall apart.Also I have banging happening from the driveshaft support bushing things.They are really fubar so thinking that might be my knock problem.Other thing to try would be to run some race gas or maybe like 1 gallon toluene or xylene to like 3 gallons fuel and that would give you very high octane.If you still have knock then likely its false knock.

I will be replacing my knock sensor shortly.I was also wondering if not putting it in as much might help a bit.Might desensitze it slightly.

Anyway I would lean out the base and try to get the trims higher.
You have way more injector than you need there.

I have a weird problem too.I can't seem to get my o2 to read past .83 no matter how rich I try to make things.I have toyota supra tt pump,
fic 650 injectors and afpr set to factory 38psi line off.I did change exhaust and the shop removed my grounding strap and some are saying that could cause the weird low o2.My 02 sensor is new ngk universal type.Possibly it was wired up wrong or something be changing it shortly after I see if new ground strap has fixed the problem.

I also heard the o2 might not read high enough when you run too rich but your car seems to hit the low .90s.Do you still have the ground strap on your car on the exhaust..??

 

[nine5raptor]

It's fairly easy to max out 450's on a 14b.

One good point you brought to put some race gas in it and see what happens. This will give an idea of whether the knock is mechanical or fuel related.