can't run rich,knock probs

[V8SpankR]

For some reason I've can't eliminate knock since I put in 550 injectors. I was pushin' my stock ones at 17psi and running 'em near 100% duty cycle but at the strip I could do full runs with zero knock but with the 550s no matter how rich I push 'em (above 6k I have my AFC set near +30%) I get knock and my 02 volts are always at about .88-.86 and I'm pushin' the duty cycle on the 550s just over 90%.

Could they be dirty,I did buy them used off of Westlund's car?

My initial runs at the strip were great at the same 17psi I was running on the stock 450s but in the last two Bandi vivists I've dropped a few tenths and can't get the knock down and this is with 105 octane too.

[DlandryTSI]

Do any of the plugs look lean? Do you have a fuel pressure guage you can hook up and make sure your fuel pressure is good?

What fuel mods have you done?

--Dave

[V8SpankR]

Hmmm,I didn't think to check my fuel pressure or I should just buy a guage.

I already had the fuel pump upgrade and re-wire plus the 550s since late May.

Could my fuel pressure have changed from stock;isn't stock fuel pressure fine?

[DlandryTSI]

Which fuel pump did you use? Any time you put a larger pump it the fuel pressure will change. However it is possible that maybe your f/p regulator has failed. Have you tried putting the old injectors back in to see if the problem goes away?

--Dave

[V8SpankR]

I sold the old ones. :(

If it is the regulator should I just pony up the money and buy a nice one?
How do you check if the regulator is bad?

[DlandryTSI]

Put a fuel pressure guage inline. Then take the boost line off the fuel pressure regulator. Take another one and apply pressure to it with the pump on. Each pound of boost is 1 pound of additional fuel pressure.

--Dave

[v413nc3]

You're running the exact same boost levels as you were with the 450's right? I would check to make sure your base fuel pressure isn't wacky, and then like dave suggested make sure it's referencing boost properly.

[V8SpankR]

I am running the exact same 17psi I ran on the 450s. What is stock fuel pressure? 36psi?

[hoffman]

40 i believe. i know it 43psi on 2gs.

[Mirage]

Now, if I'm reading this right, you're probably pushing close to 50% more fuel between the physical injector size and the AFC settings, correct? When you installed the injectors, did you mess with anything else (i.e. hacked the MAF a little more, wiring harness, connectors, fuel pressure)? I was close to the same situation that you were in (with exception to an HKS aircan, severly hacked MAF, ND 660 injectors) I found out that the MAF was screwing up the karman count. I put in a less hacked MAF with no other changes (besides leaning out the AFC) and all of my knock problems went away. This may be a longshot as I was in a different situation. IMO, lean the sucker out to where it's close to zeroed out (BTW: what turbo, and how hacked of a maf do you have?). There have been instances where knock has been created by being too rich (i've been a guenea pig in that dept.) The low O2 voltages just may be a side effect of having a loose ground or two somewhere. What do your EGT's look like during WOT? Cruising @75? Idling? Fuel trims? Are you belching black smoke? Just throwing out a few points to ponder and check.

[dougs90gsx]

I was also going to throw out the running rich causes knock and low o2's... just a thought

[V8SpankR]

I'm running an 18g at 17psi and my MAF just has the lower honeycomb out and the screw backed flush

Unfortunatly I don't have an EGT guage but I've been monitoring things with my logger. My fuel trims at the high point don't seem to want to go any higher than 81% but my mid is at 100% and the low is 102%.

I'll also check some ground pints and make sure other things are in order.

[Van]

Originally posted by V8SpankR
but with the 550s no matter how rich I push 'em (above 6k I have my AFC set near +30%) I get knock and my 02 volts are always at about .88-.86 and I'm pushin' the duty cycle on the 550s just over 90%.

You are so rich it's disgusting to even read this. You're washing oil off the cylinder walls with fucking fuel by now dammit!

You added 22% MORE fuel per injector pulse. Go back to ALL of your old s-afc settings and lean every single one out at least 10% and start there. No matter what from that point on, DO NOT GO RICHER! Trust me. I'll bet cash that when you get her right every single point goes to 15% leaner than you were except for idle (the Lo 1k rpm setting.)

Repeat after me, O2 volts are dependent on what temperature that sensor is at and how old the sensor is so I should ignore them for now.



Originally posted by V8SpankR
I'm running an 18g at 17psi
Unfortunatly I don't have an EGT guage but I've been monitoring things with my logger. My fuel trims at the high point don't seem to want to go any higher than 81% but my mid is at 100% and the low is 102%.

I'll also check some ground pints and make sure other things are in order.

EGT's suck and are dependent on more than one factor, don't waste your money, spend your dough on a fuel pressure gauge instead and the logger is fine.
81% fuel trims mean that she is so rich that even with the ecu pulling 19% of the pulse width back, it still can't get it into an acceptable range! Mid and Lo are good for now, but the 3k to 7k Lo settings on your s-afc are WAY too rich just like your Hi settings are. You've added a whole 'nother layer of carbon to your exhaust system by now. ;)

It's only your s-afc settings. That 18G turbo will NEVER, ever max out 550's, especially on race fuel and more especially at high altitude.

Go back to your old s-afc settings and pull out 10% across the board, except your idle and start going down slowly from there buddy.

[V8SpankR]

Thanks Vern,I feel kinda dumb after successfully running the 450s for a while even if I was pushin' 'em a bit hard.

I've leaned things down a bit but haven't had a chance to really log yet so I'll post some results soon.

Actually my low settings are only richened up from 3000rpm and lower while above that they are pretty much at 0%.

[DlandryTSI]

The thing you need to do is start the tuning process over.

450/550 = 81
81 - 100 = 19% Larger than factory.

So in theory to get stock boost levels running correctly you would need to set the s-afc to -19% all the way. So start there at low boost and start working your way up. That would be the easiest way IMO.

--Dave

PS: Someone correct me if I'm wrong since I'm in da 2g world now :D

[Van]

Originally posted by DlandryTSI

450/550 = 81
81 - 100 = 19% Larger than factory.

So in theory to get stock boost levels running correctly you would need to set the s-afc to -19% all the way.

The % larger formula is 550/450 = 1.22. That's 100% with an additional 22% larger.
If you think about it like that it makes more sense this way Dave. It took me abit too. ;)
100 bigger than the original 450. So 100/450 is 22% as well and 450 + 22% of 450 is 549.

I've never had it work out exactly like the math, but the math gets you fairly close. I just always start a bit richer to be on the safe side, from that point just remember to go leaner though. I just always figured that it didn't work out exactly like the math because of the Karmen Hz variable and the fact that the ECU takes your % and then translates that again into a pulse width. So there is two reasons perhaps why.

[V8SpankR]

Yeah,I'm starting over and tuning from 12psi.

[DlandryTSI]

I always hated math :p

--Dave