won't stop knockin'

[Boostymofo]

I have the boost set at 9 PSI and on some days i get a little knock (less than 3deg) and on other days i dont (on the same tank of gas).

I know that not having enough octane can cause it. It seems to also knock more on humid days. How should i go about correcting this? (everything is stock except for turbo)

My O2's at WOT are not consistant, ranging anywhere from 720-860, could that be my problem?

 

[scottyb]

Only 9psi on a stock GN? (86 or 87 I assume.)
I'm not a guru here, but here are some ideas in no particular order:
Bad injector
Inconsistant fuel delivery(pump, filter, FPR).
Dirty/oily IC, TB, intake in general. - needs "spring cleaning".
Bad fuel.
Leaky turbo bearings.
Air leak after MAF causing lean condition/incorrect air flow readings. - or lazy MAF


others.....

 

[Boostymofo]

Its an '87

With inconsistant O2 at WOT, does that mean the fuel is also being inconsistantly distributed?

I installed a brand new K&n a few months ago, and just recently had the intercooler cleaned.

i was planning on replacing the pump but figured that if i was knocking with O2s as high as 820 it wouldn't help?? Am I just confused??

 

[d0n_3d]

Originally posted by Boostymofo

I know that not having enough octane can cause it. It seems to also knock more on humid days. How should i go about correcting this? (everything is stock except for turbo)

are you saying that you have an upgraded turbo and nothing else??? uhhhhhhh there's your problem...you need to have upgraded injectors and fuel pump to run an aftermarket turbo along with an adjustable fuel pressure regulator...

 

[scottyb]

I was thinking turbo too, but you should be able run better boost than 9, I think. What are your MAF readings at WOT? You definately need to upgrade the fuel system. If you can't do injectors right away, at least run an aggressive injector cleaner thru, replace the pump, filter, and FPR at a minimum. You may also have a lazy O2 causing the inconsistant readings.

 

[striker_29]

Yeah an aftermarket turbo, on a stock fuel setup is not good. Stock chip too? A flaky or incorrectly set cam sensor can cause knock problems like you describe as well. Good luck.

 

[Boostymofo]

just took it for a quick spin...
O2's were at 835 (isn't this rich??)
AF was 130
knock 1.2 degrees

It does as far as i know have the stock chip (the original owner said it was all stock)

d0n_3d,
Are you saying the turbo is bringing to much air into the engine for the amount of fuel being supplied?
I thought the TE-44 flowed the same as a stocker until ~20+PSI?

Thanks for the replies

 

[scottyb]

Originally posted by Boostymofo
O2's were at 835 (isn't this rich??)
AF was 130

Something doesn't add up here. One of these is lying (or both), right?

 

[Cleaner13]

If I was taking a guess (and Im no guru)

I would check these things in this order

MAF yours should of read 255 or around there, thats probably why your getting such a rich mixture cause your only flowing half the air according to the sensor, and yes I did hear you can knock with a rich mixture

O2 sensor, this I would just replace its about $30 so you might as well do it anyway, this way its not messed up later down the road and you eliminated one thing in doing so

and for god sake get a fuel pump and hotwire, adj fpr, and the injectors, or if he has the stock turbo or you do maybe it would be better to just change it back to stock for now while you wait for the other things if you cant get them on time.

get a chip burned for you too
here is a guy that does it on the boards, hes a great guy and he does the cheapest chips that I know of

Name Gary Mitchell "Black Car"

e-mail turbogn@nc.rr.com

I would assume he could burn a custom chip for use with your turbo as well

also 1.2 degrees is not that bad anything under 6 tends to be ok, if you really are knocking that bad or that often, do what I did today

take the knock sensor out, clean off the threads, cover them with teflon tape, rescrew it back in but looser then when you pulled it out.

what mph does the knock happen at?
for whatever reason my knock happens at the same MPH all the time
32MPH or 42MPH
Im guessing its on the shift points

hope some of this helps

Carl

 

[blackbuick87]

He will not come close to 255 at 9psi!

You need to start at the beginning:
Why was it set at 9psi in the first place? stock is 13-15
Does it have a fuel pump upgrade at least, preferable a hotwire also?
What turbo does it have? Get some info off the turbo housing and someone should be able to identify it.

This car is all out of whack and needs to be returned to stock. Once it is running good in stock form then you can start checking other things

 

[Boostymofo]

Cleaner13,
the knock is usually occuring at the top of 2nd gear (before the shift)

blackbuick87 ,
I think the leaky exhaust is the cause of the low PSI (Its terrible - I plan on replacing it with an ATR unit once i get some more cash). Fuel pump is factory (i know, i know). The turbo is a TE-44 with 7k miles on it.

I'll replace the O2 sensor tomorrow, hopefully that will solve it...
Then i guess i'll try installing a Walbro 340 once i get some time (i'm sooo not looking forward to dropping the tank)

But if im getting knock when its rich, 835 O2s, wouldn't a new pump/injectors (more fuel) cause more knock??

 

[TurboDave]

Originally posted by blackbuick87
He will not come close to 255 at 9psi!

You need to start at the beginning:
Why was it set at 9psi in the first place? stock is 13-15
Does it have a fuel pump upgrade at least, preferable a hotwire also?
What turbo does it have? Get some info off the turbo housing and someone should be able to identify it.

This car is all out of whack and needs to be returned to stock. Once it is running good in stock form then you can start checking other things

That's what I was wondering. Since the lowest boost available for the stock wastegate was 12, I would suspect a faulty boost gauge or something along those lines. You should not be able to make boost that low, even on a stock unit. The base spring is 12#.

 

[d0n_3d]

boosty:

seriously upgrade your fuel system for your turbo otherwise you will have so many more problems later on down the road...you may even begin to blow headgaskets or worse...

the te-44 does not flow the same as the stocker until 20 psi...it flows more air regardless of what psi it is at....i personally feel the te-44 pulls just as hard on 15 lbs of boost as a stocker does at 20 lbs...trust me you need more fuel

you can get away with stock injectors up to 10 psi on the te-44...after that i started leaning out big time and knocked (this was before i upgraded to the 50's)...but i at LEAST had a 307 hotwired fuel pump and accufab adj. fuel pressure regulator and the pressure was set WAY HIGH to max out the stock injectors...

 

[BoostedBug]

Re: Re: won't stop knockin'

Originally posted by d0n_3d
are you saying that you have an upgraded turbo and nothing else??? uhhhhhhh there's your problem...you need to have upgraded injectors and fuel pump to run an aftermarket turbo along with an adjustable fuel pressure regulator...

I can run my car at 17 lbs of boost on my stock injectors with 0 knock on pump 93 octane gas.


I do have a good fuel pump,regulator and my car is tuned correctly. I also use the 92 thrasher.


Good Luck