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Tech Area => General Buick Tech => Topic started by: larrym on March 20 2015, 01:26:57 PM

Title: Low boost knock
Post by: larrym on March 20 2015, 01:26:57 PM
Been helping a buddy with his car, its running great WOT and putting around. But at part throttle he sees retard on the scan master that starts low and climbs if he maintains that speed.


Its a smaller BB turbo that spools insanely quick and it seems to be on boost with any load, this shows by the half empty ALKY tank after trying to tune this out.
 He says it starts as soon as it begins making boost 1-2 PSI and AF reads around 12.0 on the wide band he has a screw type boost controller and stock type waste gate.
TT chip 42lb injectors, EGR deleted, Razors Kit,


We have played with the gain knob on the ALKY, tried a different MAF with a translator no change, fuel pump is new same with filter, all sensors are set and double checked.


We are going to try a known good ignition module to see if that clears it up.


Are there any other things we should look at?


Its the old motor out of my car and its kinda tired but does not knock at WOT, I told him to just drive it with the throttle mashed  :rock:  its around town that makes it a pain....
Title: Re: Low boost knock
Post by: good2win22 on March 20 2015, 02:50:07 PM
Can you put up a log?  I would be interested in seeing what the timing is doing right before the knock
Title: Low boost knock
Post by: larrym on March 20 2015, 02:52:59 PM
No power logger ....
Title: Low boost knock
Post by: larrym on March 20 2015, 02:54:04 PM
We did pull timing in 1-2 to try and eliminate it  did not do much.
Title: Re: Low boost knock
Post by: earlbrown on March 20 2015, 04:55:51 PM
Flat spot with the TPS?
Title: Low boost knock
Post by: larrym on March 20 2015, 05:48:26 PM
Cool something else to try I have an extra we throw at it thanks Earl!
Title: Re: Low boost knock
Post by: Scoobum on March 20 2015, 06:01:37 PM
Put your PL on his car and make a log.
Title: Low boost knock
Post by: larrym on March 20 2015, 06:10:50 PM
Mine does not exist either.... I  have autoXray that will capture data but not timing.
Title: Low boost knock
Post by: Steve Wood on March 20 2015, 07:51:32 PM
What are the o2s during this?
Title: Low boost knock
Post by: larrym on March 20 2015, 08:02:43 PM
On the wide band they are about 12.0 did you want the narrow band readings?
Title: Low boost knock
Post by: Steve Wood on March 20 2015, 09:58:10 PM
That's OK.... I wondered if it was rich... But it looks pretty lean
Title: Low boost knock
Post by: larrym on March 20 2015, 11:07:14 PM
That's where it starts if he replicates the issue on a long hill and brings in some boost the ALKY starts to spray and you can see the WB start to drop into the 10s and the knock retard continues to climb until you let off or mat it. I don't hear any detonation.
Title: Low boost knock
Post by: Steve Wood on March 20 2015, 11:29:52 PM
If it's very far into the tens, you can get so called rich detonation which can trigger the knock sensor.  Is PE being commanded by the Ecm?
Title: Low boost knock
Post by: larrym on March 20 2015, 11:45:34 PM
It's strange it will start just as it starts to build boost that's when the AF is around 12 if he tips in more bring on boost up to say 6 to 10 psi it continues to show retard and the AF drops as the ALKY comes in. Everything seems to be working like it should it is a challenge. I guess it could be engine noise this motor has been abused valve train is new cam lifters chain.
Title: Re: Low boost knock
Post by: Steve Wood on March 21 2015, 10:50:58 AM
Does it seem to be prevalent at a given rpm range or does it occur anywhere in the band?
Title: Low boost knock
Post by: larrym on March 21 2015, 12:02:25 PM
It's there in the lower rpms much like the boost it will disappear when you wind it up.
Title: Low boost knock
Post by: larrym on March 21 2015, 12:07:17 PM
When he inspected the motor 1 rod had excessive side clearance
I told him not to look just bring me back the pieces when it was done.
Title: Re: Low boost knock
Post by: Steve Wood on March 21 2015, 01:15:12 PM
I have seen that with valve train noise more than once....I suspect you are correct, the ecm is hearing a noise within the frequency range that it considers to be detonation and is pulling timing.
Title: Re: Low boost knock
Post by: 278CIKILLER on March 21 2015, 02:27:28 PM
I have a real nice well built motor for sale if need be , This is a drop in and go.
Title: Low boost knock
Post by: larrym on March 21 2015, 02:45:13 PM
His motor is at the machinist thanks for the offer. I just installed mine and told him he could run my old one till his is ready.
The motor he had in the car lasted 95 miles.... This one has been beat to death bored .030 crank is .010 under on the mains .030 on the rods owes me nothing and is responsible for my addiction and my 11:43 pass

It's spun to 6000 rpm many times but it just kept going.
Figured My buddy "no lift McLoud" could try and finish it I couldn't !
Title: Re: Low boost knock
Post by: Scoobum on March 22 2015, 08:05:33 AM
Is the knock sensor torqued correctly? Yeah I know, I'm looking for an easy answer. :)
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