WOT=instant knock!

[Darklord]

I'm getting heavy knock retard readings whenever I go to WOT whether from a dead stop or at a roll. It only does this for the first couple frames and then the knk falls off. I've tried different chips but nothing seems to help this problem. At the track, with pure race gas the problem seems to diminish somewhat so this leads me to believe it isn't false knock. But on the street with 93 in the tank and only 15-16 psi boost this is a major issue. Could a bad ESC module or knock sensor be causing this? What else could I check that might help?

 

[Quick6'n'-K.C.]

how much knock are you getting?

got good oil pressure?

checked for wiped cam lobe?

just for giggles, loop the compressor housing vacuum hose to the wastegate and you will get 11 or 12 psi

go out and floor it and see what you get-

if you get knock, then i would think that your fuel pressure regulator/ pump is bad and not compensating fast enough for the boost!

do you have direct scan?

 

[Darklord]

Let's see.
How much knock?
30 degrees. I know, it's frightening but the car's been like this for years and the motor is amazingly still together. Makes me wonder if it is "real" knock.
The oil pressure seems about right for a high mileage GN with a original motor. Car just turned 185,000 miles.
Haven't checked for a wiped cam lobe. Are there any other signs of this I could look for? The car runs/idles excellent with the exception of the knk retard issue.
The fuel pump/fp regulator should be fine since it did this before and after they were installed. The fuel filter has been changed and the pump is hotwired. Also running Red's volt booster.
No directscan just an OTC 4000.

 

[Quick6'n'-K.C.]

take the wastegate rod off to get zero boost.

now go out and floor it, if you get knock, then its either false knock, or a internal problem-

have you ever had the bearings replaced in it?

 

[Darklord]

Haven't tested it in sometime but if I remember correctly lowering my boost to around 12 psi usually helps lower if not completely eliminate the knk. I'll try it again with the rod disconnected and see how it goes. The bearings are factory original and looked to be in good shape the last time I checked. A couple years ago, I was pulling my hair out trying to diagnose this problem but finally just gave up out of frustration.

 

[Darklord]

Okay, I'm pretty sure this is real knk after testing it with the rod detatched. The car hit about 5 lbs of boost and no knock. It really seems as if the fuel system cannot keep up with the higher boost and this results in a boost spike when I go WOT. What I don't understand is why the fuel system would do this. I'm running Red's XP pump hotwired with the Casper kit, Red's volt booster and a Kirban adjustable regulator with billet top. Also tried a variety of chips and different MAF sensors with the same results. Is there anything else I should be looking for?

 

[Russ Merritt]

Ported heads should have nothing less than 50# injectors. I had the same problem last year with 55s on my set up. Anytime I went WOT it would have crazy knock and it was real as I blew 2 HGs. It only happened on the initial whack of the throttle, once it was done it would run 19# no knock on pump gas. Just getting through it was brutal. I went from 21 degrees on my ME chip to 18 and put 83# injectors in and it's all better.

 

[Darklord]

Actually, the car had this problem with the stock heads too. The 36# blue tops are probably not optimal with ported heads and higher boost at the track but I don't see why they would cause a problem with 16 psi boost on the street.

 

[Russ Merritt]

So maybe one of em is wasted. Why chince on the fuel system anyway? You know what you gotta do.

 

[TurboDave]

Originally posted by Darklord
Actually, the car had this problem with the stock heads too. The 36# blue tops are probably not optimal with ported heads and higher boost at the track but I don't see why they would cause a problem with 16 psi boost on the street.

With enough throttle, and boost, 36# injectors wouldn't even keep up with what was needed on my setup (always have run the TE44)

I can't imagine any situation, other than cruise, where they could keep up with ported heads

My MSD50's and TE44 is a perfect combination for my completely stock engine/heads. But neither would suffice very well with ported heads.

Since the volt boost isn't helping any, I'd bet money if you took it off, you'd find the ONLY thing you would loose is more gadgetry waiting to break and cause problems.

 

[Eric Stage I]

You spoke of a boost spike. Even a small spike of 1 or 2 psi when you first floor it can cause things like this. You may want to play around with the wastegate tension and bleeder (if you have one) to try and eliminate the spike. If you adjust the rod to have less tension (make it longer), then use the bleeder to adjust the boost back up, sometimes that will help the spike. If you are using the factory solenoid, the boost ramp speed can be altered.

Another option, since you have high flowing heads, the PE fuel in the 3200rpm area may need to be bumped up. Also, maybe you need less timing.

Just some thoughts...

Regards,
Eric

 

[ULYCYC]

Are you using your OTC4000 in "road test mode" If not it locks some of the computer parameters for easy sampling and will not get the proper timing adjustments during a climb to WOT. I blew a head gasket this way before I became real smart

 

[Darklord]

Thanks for the replies.
Actually Eric, "boost spike" was a typo. What I mean't to say was knock spike since it shoots up to around 20-30 degrees of knk retard and then settles down.
ULYCYC, I am definitely in road test mode on the OTC. I made the same mistake when I first bought the scan tool some time back but fortunately didn't blow anything. I don't think it will read degrees of knk when not in road mode.
TurboDave are you saying 50#s aren't even enough to supply fuel to a TE44/ported head combo? I would've thought the MSD 50s would've been my next fuel upgrade. Aren't they sufficient to supply fuel for a 10 sec. ride much less my 11 sec. car? I realize the blue tops are at best barely keeping up but they don't seem to be leaning out enough in 3rd gear to cause concern. At least with street boost.
This problem goes back to even the stock turbo/blue top combo so possibly it is injector related although the blue tops were almost new at the time.

 

[TurboDave]

Originally posted by Darklord
TurboDave are you saying 50#s aren't even enough to supply fuel to a TE44/ported head combo? I would've thought the MSD 50s would've been my next fuel upgrade. Aren't they sufficient to supply fuel for a 10 sec. ride much less my 11 sec. car? I realize the blue tops are at best barely keeping up but they don't seem to be leaning out enough in 3rd gear to cause concern. At least with street boost.
This problem goes back to even the stock turbo/blue top combo so possibly it is injector related although the blue tops were almost new at the time.

Well, draw your own conclusions from my setup. My block, all internals, and heads, intake, everything are factory stock.
I run 25# of boost at the track,
and I'm able to send these MSD50's up in to the upper 80's duty cycle.
I'm quite convinced if I were running ported heads that they'd be well used up!