Knock Retard

[TurboTdr3.8]

but when we take the vac off on his, the pressure jumps to 47. It was set at 43 using my gauge originally.

TT chip says to set at 43lbs with vac hose off . If you think the snap on gauge is correct then use it and check again .

At 43lbs of fuel pressure and 10lbs of boost it should read 53lbs of FP .

My FP goes down in about 30 minutes of setting on my car . So you should be ok , like VtheGNMan says his does similar , plus try the higher octane see what happens then .

 

[Pronto]

Recall works on wot only. Like Kim suggests, reset the fp with the Snapon gauge.

 

[Pliskin1]

Some fuel pumps have a relief valve and the pressure drops fast when the pump isnt on. Mine bleeds off quick like you are expierencing, no worries.

Someone will correct this too but it seems my scanmaster only stores readings at wot or real close. There is probably a set voltage where it stores it at.
One cool thing too with it, is if you stored KR on the recall, hit both buttons and it ll tell you at what mph it happened at.

I was chasing some intermitten KR like you were a while back. I got some 110 octane unleaded race fuel and added 1 gallon to 3\4 tank of gas to up the overall octane up a couple points. Then it went away.
What are O2s when you are having KR?
Do you have the stock MAF?

It would be nice if this was something as simple as "bad gas". This latest tank of gas was from a Shell station - all others have been from Sunoco. Both stations are newer, with new tanks installed, and I go with the 93 octane (highest I can find here in NJ). 10% Ethanol.

My 02s have been OK, although I did not see them today when I had the knock retard. (I put them in my previous posts but didn't refer back: First time was 8xx, and second was at 745.

Stock MAF.

@turbot - I get it with the fuel pressure draining slowly, and even though VtheGNman has similar issues to mine, still seems strange. I'm no mechanic, but always thought fuel rails should hold pressure for... hours? even when off? But unless someone comments to the contrary, I'll forgo that being related to the issues I'm experiencing now.

Will have to see if I can get my hands on some race fuel. Its not readily available in my area to my knowledge. But I suppose for a quick test to throw a gallon in and see if it solves the problem, that'll be enlightening.

 

[Pliskin1]

Recall works on wot only. Like Kim suggests, reset the fp with the Snapon gauge.

Will do. Seems like the most logical place to start.

 

[VtheGNMan]

We have 1 gas station that has 110, has to be pumped into cans. Its by the local race track and sells it to all the racers. Try calling around and seeing if someone like that may carry it.
Seems like all the normal stations only have 91 oct around here. Could your station have switched and you didnt realize you were getting only 91?
I dont mean that as any insult, its just those were the kind of KR numbers I was getting on 91.

I also upgraded my stock maf to a new gen one with the translator and it ran even better yet. The are super easy to install too. Literally just plug connectors in. Then if you need an adjustment, you just turn the dial inside the translator and viola, correction made

 

[Pronto]

You can make up some homebrew to raise the octane. I ran it for a year with a 100 octane chip. For testing purposes it would be fine. Better than adding leaded race fuel. http://www.gnttype.org/techarea/misc/octanebooster.html

 

[VtheGNMan]

Actually the 110 is unleaded race fuel. Too bad its close to $5 1\2 a gallon. But it did the trick, it let me know my octane was causing the KR. Hopefully OP can find some and try out too.

 

[Pliskin1]

Thanks Guys.

Reset the FP using the Snap On Gauge. Holding steady at 43 off vac, and 38/39 on. (although it was high at first). THought about putting the stock FPR back on just to see if there were any differences, but I guess if I'm holding at 43 and 38/39, not point in doing that?

Took various runs/pulls, and still recording knock, although nothing as high as the double digits I was seeing previously. Interestingly, on 2 separate occasions, I was recording about 5-6* of knock retard while at 8-11# of boost. But under WOT with 16# of boost (I know, probably not the best idea), the readings were 2.3 and 1.8 respectively. Holding it steady does not result in the knock increasing. Is there any reason why the knock would be worse at 8# vs 16#? Or maybe its just coincidence.

FP is rising 1:1 with boost, so I guess that's good.

Went to Island Dragway (here in NJ) with the intent of buying some race gas. Didn't have time to stay there until they opened (3 hours after I got there), but talked to a racer who says they do sell the Sunoco 104 Octane (unleaded) right outta the pump. But alas, had prior engagements and had to leave.

I also found a place about 20 miles from me that sells 5 gallon containers of Sunoco 260GT. Supposedly he has it in stock, available for purchase at about $9 a gallon. Phuck it - if he has it on Monday morning when I head over there, I'll buy it.

VtheGN - No disrespect taken. I welcome all suggestions, and who knows, maybe I did get some bad gas or put the mid grade in while not paying attention. I was low on fuel today (little less than a quarter), so I went and put Sunoco 93 in, about 8 gallons. Figure I'll leave some room for the race gas if I can find it.

I mentioned in an earlier post that I need a new belt pulley tensioner. You can absolutely hear it rattle around, although its intermittent. But definitely there. Is there any chance that when I'm putting a load on the engine, the noise coming from the bearings/tensioner is being detected as knock?

 

[dynoman]

YES...look up the thread " Billet Tensioner " page # 9 post #178 in the "Parts for Sale" section, and there is a video of a motor during a run. Watch how the tensioner jumps around.

 

[Pliskin1]

WOW! That thing was chattering like mad. I have no idea if mine is like that, but coincidentally, I just started to notice the sound after I had this work done. That may be something I need to look into replacing sooner rather than later. Thanks Sam.

Mike

 

[RmvBfrFlght]

I mentioned in an earlier post that I need a new belt pulley tensioner. You can absolutely hear it rattle around, although its intermittent. But definitely there. Is there any chance that when I'm putting a load on the engine, the noise coming from the bearings/tensioner is being detected as knock?

Yes, the ESC system will pick up bearing noise as knock. One of the methods the knock filter uses to detect knock is to 'listen' for a change in the sound of the engine. That is a change in the frequency of the engine noise. One thing you can do is to pull the plugs and check them in good light with an eye-loupe:

http://www.dynamicefi.com/SparkPlug.php

If they are free of specks, then the knock is false.

RemoveBeforeFlight

 

[Pliskin1]

Haven't forgotten about your guys and the info provided to date. Being self employed, my schedule can go from swamped to bored. Been on the swamped side recently, and traveling on business the next 5 days.

Anyway, picked up 5 gallons of Sunoco 260GT. Its 100 octane. Couldn't find the 104. So my plan is to put a couple gallons of that in my tank (mixed with the 93 that's in there now), and see if that helps. Also want/need to replace the belt tensioner. I've been reading on the forums here but still not quite sure what I need to replace. Is it the whole unit or just the pulley? I know I can apparently just replace the bearings as well (which seems the cheapest option), but I don't mind spending a few $ to replace the pulley.

I also see the prices are all over the board on these things -$35 at one place, $110 at another, $70 at that place... Any insight on what exactly I should replace, and a "fair" price for it?

 

[87-WE2]

Stock tensioner assemblies are pretty well non-existent anymore. If you do find one, you'd probably pay north of $200. I replaced the pulley on my tensioner with one from o'reilly parts. It works, but I don't like the new pulley. It doesn't have the lip on the edge to keep the belt from traveling. Another option is to find a new bearing to stick in your stock pulley. Earl brown did a write up on replacing the bearing in the pulley, but he did a couple of steps that I'd leave out!!!


Sent from my iPhone using Tapatalk

 

[SHADOWII]

I was referring to the return fuel line from the regulator. If you squeeze it off w/a pair of vice-grips, the fuel pressure would be maintained w/the key to on. This is not needed w/your f/p problem solved.