PocketLogger Log Question

[le0net]

Hi!

Sorry for a long post, i have a rebuild 1990 Tsi AWD with 50trim turbo, 3" MAFT+ translator, rewired 250 pump, AFP regulator (40 on idle, almost 50 when reving) 660cc injectors, SAFC, no adjustements done since logger shows between 90-115% on all fuel trims. Stock intake, FMIC, EVO3 exhaust, EVO2 O2 housing, New 02 sensor, 2,5" to 3" downpipe, no CAT, 3" all the way. Boost about 13PSI

Just confused about knock level at high rpm, and o2 sensor changing that much on lower RPM.

Could someone have a tips on what to log more, or should i add fuel att higher rev or what, boostleak?

A few rows from logging below...

Top knock was 41 at one point and high rpm.

RPM Knock O2
2719.0 0.0 0.24
2781.0 0.0 0.43
2781.0 0.0 0.67
2813.0 0.0 0.82
2844.0 0.0 0.8
2844.0 0.0 0.63
2844.0 0.0 0.45
2906.0 0.0 0.37
2938.0 0.0 0.37
2938.0 0.0 0.59
2938.0 0.0 0.78
3063.0 0.0 0.8
3094.0 0.0 0.75
3063.0 0.0 0.53
3125.0 0.0 0.29
3188.0 0.0 0.22
3156.0 0.0 0.69
3094.0 0.0 0.92
3031.0 0.0 0.94
1656.0 0.0 0.12
1750.0 0.0 0.1
1906.0 0.0 0.1
1844.0 0.0 0.1
1813.0 0.0 0.16
1906.0 0.0 0.29
1906.0 0.0 0.39
1938.0 0.0 0.55
2000.0 0.0 0.69
4031.0 0.0 0.82
4063.0 0.0 0.86
4031.0 0.0 0.9
4063.0 0.0 0.9
4344.0 1.0 0.9
4313.0 1.0 0.9
4469.0 8.0 0.9
4500.0 12.0 0.9
4719.0 12.0 0.9
5594.0 15.0 0.94
5781.0 15.0 0.92
5688.0 15.0 0.94
5938.0 15.0 0.92
5969.0 22.0 0.94

 

[le0net]

Need to check my AFPR settings for that, will do a pull tomorrow with log on:
RPM
O2
Knock and timing

Should i include something else?

 

[turboboy4]

If you have anyway to look at fuel trims, you can look at short and long term fuel trims. This will tell you what the computer is having to do.

 

[Gstclipse69]

The o2 sensor is going to bounce all around in closed loop applications. On a 1g base fuel pressure should be ~37 with the vaccum line unattached. Do a wot pull in third gear from 2500 to over 6k. When your in open loop (wot) then the o2 sensor should stay the same around .92 or so. Then you can look at your timing and o2s and that will tell you whether to add fuel or not.

 

[le0net]

Getting my car tomorrow, had the stock exhaust replaced to a 3" all the way,
Had some logs from a couple of weeks ago, and i see that the knocking starts just above 4000 and continues until timing retards enough, just wondering if i should add some fuel with the SAFCII before making a WOT log, dont like the knocking.

RPM Knock Timing O2
3563 0 30 0.78
3688 0 30 0.76
3813 0 30 0.73
3969 1 28 0.76
4031 7 26 0.8
4250 15 23 0.8
4500 27 19 0.78
4594 26 19 0.78
4875 26 20 0.78
4969 26 20 0.8
5063 25 21 0.8
5031 25 37 0.76
5188 7 43 0.76
5156 0 45 0.61
5063 0 45 0.55

Any tips on how much (%) to add, just start with 5 or more?

Long term fuel shows 114% low, 100% mid, 100% high the latest.

Leif

 

[kenamond]

Depending on your model of car, the base fuel pressure will be different. US cars have different ECUs for auto vs. manual trannys. Autos run 390cc injectors at 43-ish psi while manual tranny cars run 450cc injectors at 37ish psi. Also, the JDM cars run 550cc injectors at some other fuel pressure (I'm not too clear on the details on the cyclone ECUs). I'd do a search, knowing what kind of car you have, and get the base fuel pressure set correctly for your ECU. You have to remove the vaccuum line from the AFPR in order to set base fuel pressure; search for setting base fuel pressure.

If you know what injectors came stock on your car and you know what injectors you upgraded to, you can calculate a set of fuel trims for the AFC to start with. Again, you can search for this as well.

Basically, it looks like your base fuel pressure is too high, but I can't tell until I know what ECU your car has. Also, I can't tell if those logs are at full throttle (in open loop) or part throttle (closed loop), and you can't make any sense of the O2v unless it's full throttle.

So if you can get your base fuel pressure set *correctly*, set up your AFC trims based on the crude calculation (using new and stock injectors), then you could start doing full-throttle pulls and looking at the O2v and knock to fine-tune the tune.

 

[le0net]

Thanks for these tips, i didn’t know that the base pressure had that much to do with it, really appreciate it.

Seems my 90 Talon should have 37-38 psi base pressure, original 450cc injectors. I have 660cc injectors now, with the MAF-T configured for that. My fuel pressure with the vacuum hose in is over 40, so i need to take it down much.

I did find different answers on what pressure to run with my 660cc injectors, but I’ll take it from you that the stock base pressure should be ok.

Since the maf-t should compensate for the bigger injectors I might not need to add that much from the safc.

I will start with this and log a few WOT:s

 

[kenamond]

Thanks for these tips, i didn't know that the base pressure had that much to do with it, really appreciate it.

Seems my 90 Talon should have 37-38 psi base pressure, original 450cc injectors. I have 660cc injectors now, with the MAF-T configured for that. My fuel pressure with the vacuum hose in is over 40, so i need to take it down much.

I did find different answers on what pressure to run with my 660cc injectors, but I'll take it from you that the stock base pressure should be ok.

Since the maf-t should compensate for the bigger injectors I might not need to add that much from the safc.

I will start with this and log a few WOT:s

Make sure you set the base fuel pressure with the vaccuum line removed. At idle, you have vaccuum in that line, and that shifts the fuel pressure down by that much vaccuum. Disconnecting that vaccuum line at idle will remove the vaccuum offset so that you know what the base fuel pressure is. Only then can you properly adjust it.

And if you search, you'll most likely be able to find a good set of trims for running 660s on a motor that has an ECU for 450s. That equation won't work if you're not running the stock base fuel pressure, though. After you get the fuel pressure set up correctly and have the calculated trims set up correctly, then you can start doing full-throttle pulls and fine-tuning.

There is no law saying that you have to run the stock base fuel pressure, but it just adds another variable into the mix when tuning. I recommend that you stick with the stock pressure just to make this first tune easier.

 

[le0net]

Got the car back now, the new exhaust looks awesome, and doesnt sound too much.
Adjusted the base fuel pressure with the vacuum line disconnected to 37psi.
Cant the MAFT compensate for the bigger injectors? I read in the pocketlogger forums that if the fuel trims is between 80-120% it should be ok. Mine is low 119%, mid 103%, low 101%.

If not i have to search for the trims.

Tested a full WOT on 3rd gear from 2500 and to redline, below the looong log...
Boost went up to 18-19psi with the new system, dont understand where the knock comes from...

RPM Knock Timing O2 TPS
2969 0 35 0.53 24
3000 0 35 0.69 24
3000 0 35 0.67 24
3000 0 35 0.73 24
3000 0 35 0.63 24
3031 0 35 0.22 24
3031 0 35 0.51 24
3031 0 35 0.76 24
3031 0 35 0.65 24
3063 0 35 0.49 24
3063 0 35 0.31 24
3063 0 35 0.76 24
3094 0 35 0.69 24
3094 0 35 0.55 24
3094 0 35 0.18 24
3125 0 35 0.78 24
3125 0 35 0.75 27
3156 0 33 0.82 66
3188 0 32 0.57 100
3219 0 31 0.76 100
3250 0 31 0.75 100
3281 0 31 0.67 100
3344 0 31 0.55 100
3469 0 30 0.12 100
3500 0 30 0.04 100
3594 0 29 0.02 100
3625 3 27 0.02 100
3719 2 26 0.02 100
3781 2 26 0.61 100
3875 12 23 0.78 100
3938 12 23 0.78 100
4031 11 23 0.8 100
4156 11 23 0.8 100
4313 24 20 0.8 100
4438 30 16 0.8 100
4406 30 16 0.8 100
4500 30 16 0.82 100
4625 29 13 0.82 100
4750 36 12 0.84 100
4875 36 12 0.84 100
4969 35 11 0.86 100
4969 35 11 0.86 100
5219 35 12 0.84 100
5188 34 14 0.84 100
5250 35 14 0.86 100
5500 35 12 0.84 100
5625 34 14 0.84 100
5656 34 14 0.84 100
5813 34 14 0.84 100
5813 34 15 0.84 100
5938 33 14 0.84 100
5938 33 14 0.84 100
5875 33 14 0.84 100
6125 40 12 0.84 100
6094 40 11 0.84 100
6313 39 12 0.84 100
6156 39 11 0.84 100
6344 39 11 0.84 100
6375 39 10 0.84 100
6344 39 10 0.84 100
6469 38 8 0.84 100
6656 38 9 0.84 100
6594 39 9 0.84 100
6625 39 9 0.84 100
6750 39 9 0.84 100
6906 38 8 0.84 100
6688 38 9 0.84 100
6844 38 8 0.84 100
6906 38 8 0.84 100
6969 37 8 0.84 100
6906 37 9 0.84 100
7125 37 9 0.84 100
7063 37 9 0.84 100
7094 37 10 0.84 100
7281 36 10 0.84 100
7250 36 11 0.84 27
6875 32 34 0.82 11
7031 15 40 0.8 11
6563 0 45 0.75 11
5938 0 45 0.73 11
5500 0 45 0.61 27
5375 0 43 0.02 43

Feels i need to start with checking boost leaks, change to colder sparks?!

Any tips?!

 

[kenamond]

You're leaning out. Your O2v should be around 0.98v. You need to richen it up everywhere it's lean. I'm not an SAFC expert, so you really need to do your homework on this and find out more about it before you destroy your motor. Find out what trims you should use for 660s for your stock ECU and fuel pressure. Set the SAFC to that and go from there. You want no knock or maybe 1 or 2 counts, and you don't want to run too lean. If you keep running your car with the current tune, you can damage the engine.

The high boost may be boost creep. The larger exhaust is probably the reason. Search on boost creep for an explanation, how to diagnose it, and how to deal with it.

If you do have creep and you decide that you just want to run 18psi, you probably want cooler plugs (NGK BPR7ES). I assume you have a stock 14b turbocharger, so you might want to also search and find out if 19psi is too high for the 14b on a stock side-mount intercooler.

Fixing boost leaks is something you should have already done before you started trying to tune with the SAFC. Boost leaks throw off your air-fuel ratio, so your tune will be off when you fix the boost leaks and you'll have to re-tune. You really need to read about these things and teach yourself before you dive into it, or you're just going to break something.

And you need to update your profile so folks know what your setup is.

So start searching and learning before you break something.

 

[le0net]

Learning is the point with this I also har a EGT and that stays below 1200F, i will start to search.

I have a Bullseye 50 trim turbo, but a stock BOV so that could be an issue also.

Thanks for all the tips.

L

 

[le0net]

Anyone else with a 1990 DSM who seen this? I read it from pocketlogger forums.

"O2 Values
There are really no 'good' values for o2s at WOT because they differ between cars and sensors. .9 and above is generally considered pretty save. For some unknown reason, '90s seem to read .1v lower. I've run as low as .7x on pump gas on my 90. I would not recomend this without other instrumentation like an EGT."

That would mean that my 02 value is 0.94V, but still i need to richen the fuel.

I will start with the boost leak test and then add fuel from SAFC.

Thanks.

 

[le0net]

Hi again...

Read a bit about boost creep, and thats definetly the case here. When i made the above pull the boost first went to 15, and the slowly went up to 16, 17 18 almost 20 before i let off the gaspedal.

Strange thing is that when i had the stock o2 and exhaust the boost never went above 10psi, (had knocking with that setup also) .
After change to EVO3 o2 housing and 3" system all the way i get the boost creep, shouldt it be easier for the boost to get out with a bigger system? (I have a 50 trim turbo.)

I have tried to find someone with the similar setup, but cant find anyone, but i think i might start with checking that the WG arm actually moves, i should be able to do that by using a aircompressor to the WG?

 

[le0net]

Hi All!

Finally had some time to use the SAFC and get rid of the knocking, looks a lot better now.
Needed to add around 40% on HI-Trim to get rid of all knocking, but i will start to lean it out to get the performance.
Also im not sure if i had any boost creep, boost goes up to 18psi and doesnt go over that, but seems my BOV is leaking (stock) since i feel that the engine looses power when i come up to high RPM. Any recommendation on what BOV to get that holds up to 20 psi and is big enough for my turbo?

2nd and 3rd gear pull logs below, any comments would be much appreciated.

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[le0net]

Just a thought,

Since my timing is "high" (around 20, should be around 15?) at WOT and high RPM, i can safely increase boost?

 

[95CarbonEclipse]

It's looking a lot better, but don't log a 2nd to 3rd gear pull. You need to log in 3rd gear from about 2500 RPM all the way to redline. Your knock count went down significantly. Your WOT O2's are looking better, but I think the consensus on this site is that they do need to be around a .91-.94v. Your knock count will let you know when you get it high enough. I'm sure Kenamond will chime in on this and you should definitely take his advice as he is much more expierianced in reading logs then I am.

I woudln't add more boost right now as you're still running a tad bit lean it looks like. You can see that your timing is even higher then 20, but it's getting pulled (most likely because of knock).

Definitley check for boost leaks if you haven't already done so. BTW... I'm jealous of your knock sensor and the excellent s/sec rate you're getting.

 

[leecavturbo]

good results
i like the format of the log and the graph
very easy to read like that!
more ppl should do this

 

[le0net]

Yes, looks a lot better, and feels safer now

just wondering if the settings looks ok ,
HI-throttle, around +40% from 3000rpm all the way to 7000rpm,
i read that the SAFC II maxes out at 50%.
Lo-throttle is around +20-30% all the way, is there a way to adjust the lo-throttle correctly since it doesnt knock nor show any o2 values, is it just to get the fuel trims to be at 100%?

Shuld i change the throttle points, its low 30% and hi 70% now.

I will make a 3rd gear pull asap and post the log from that.

Leif

 

[turboAWDfanatic]

I didn't read every post all the way through, so forgive me if I'm reiterating something someone already said.

About boost creep. There is a fallacy that having a bigger or "ported" O2 housing will help eliminate boost creep. Often, a "ported" stock O2 housing is only ported in the main exhaust portion of it, rather than the side route where exhaust goes through the flapper and recircs back in. This will INCREASE boost creep in the same way that having a bigger down pipe, big exhaust, and removing the cat will do. Even aftermarket O2 housings with bigger wastegate routing will ALSO have bigger exhaust routing from the turbo. For a modified O2 housing to reduce boost creep, it should have a heavily ported wastegate route, with minimal porting done to the main section (IMHO). Yeah...this gives you more of a restrictive exhaust system, but if you want free flowing exhaust and no creep, get an external wastegate.

To help eliminate creep, do the following (depending on turbo setup):
- port WG area of turbo exhaust housing
- port flapper hole and install bigger flapper *if needed*
- make sure flapper can open 90*
- get an O2 housing w/ really big WG recirculation tube
- do a WG dump setup on your O2 housing if you want. I personally wouldn't.
- Put your cat in if you've removed it. Or get a bigger *REAL* cat. The whole cat elimination thing on street cars is crap and it increases boost creep

NOTE: this is an abbreviated list that doesn't go into detail. Do a search to look up how to do all of this properly in case my descriptions don't make sense on their own

OR, you can go with SOADweskey's advice for eliminating creep. Have enough fuel and tuning for 25+ PSI and forget about it!!!

 

[kenamond]

I don't have a lot of time to type, but I'll see what I can do. Looks like you've made a bunch of progress.

Creep is more common in a larger exhaust, because there's less backpressure in the exhaust which makes less backpressure upwind of the turbine (the turbine has a PR just like a compressor). But the difference upwind and downwind now smaller (if the downwind pressure drops by 10psi, the upwind pressure will drop by more than 10psi), and that pressure difference is what is pushing exhaust through the WG. The turbine is still operating as efficiently as before, but the WG flows less air now. You have to either make it flow better (whole bunch of options there), add an exhaust restriction (undo the performance gain you just added), or upgrade to support the boost it creeps to.

As for the increased timing, I think this is due to the AFC lying to the ECU about airflow. AFC does this to fool the ECU into pulsing the larger injectors for a shorter period of time (to compensate for larger injectors), but that airflow is also used by the ECU for the timing. So when you tell the ECU that you have 40% lower Hz signal from the MAF, the ECU ends up thinking you're on a different point in the timing map and need more timing advance. That's one reason AFC isn't the best option running 650s; the lie gets so bad that you might start knocking from the aggressive timing that comes as a side-effect of the lie.

I'd read your plugs right after a 3rd gear pull if you can. You want a tan-orange haze on the tips.

Try looking at the STFT+LTFT trims (add them) at various loads (cruise at little throttle, then floor it a bit more, and the LTFT value will (may) change to a different value. The LTFT Lo and Hi probably show up in your logger just as "LTFT" but you will be looking at one or the other. These are the % of fuel the ECU thinks it needs to correct based on closed loop mode (where it's trying to keep the O2v flipping above/below stoich). The STFT is what it's adjusting constantly to get stoich AFR during closed-loop (low load). If conditions are right, it goes into learn mode and transfers the STFT+LTFT into the LTFT (overwrites the previous value) and sets STFT back to zero. But once it gets things dialed in, your STFT will be pretty small and the LTFT won't change much. Look at those to get an idea of how far off your low-to-mid load AFC settings are. As I recall, you can't use the LTFT trim values as-is for corrections to the AFC settings, because the AFC is altering a Hz signal, not the actual load (air mass per rev in a cylinder), and the Hz percent is different than the load percent, and the load percent is what the LTFT tells you. But I vaguely recall that this is different between 1g and 2g. Anyway, you can look at the LTFT and see if the ECU has noticed that you're running consistently lean (positive LTFT+STFT) or consistently rich (negative LTFT+STFT). And remember that there are actually two LTFT values, but the logger only shows you the active one. If you watch the LTFT as you rev the engine in neutral (slowly), you'll probably see it switch between two values (but if they happen to be the same, you wouldn't notice).

And removing a cat decreases backpressure in the exhaust, which decreases backpressure in the exhaust manifold (by even more), which means the pistons don't have to push as hard during the exhaust stroke (exhaust stroke subtracts torque that other power-stroking-pistons are generating), so decreasing the work it has to do increases overall torque) and intake air enters a combustion chamber with a lower pressure (get more air/fuel in the cylinders and less remnant exhaust) which adds torque. The car will flow more air at the same level of boost (higher VE). Turbo race cars have as short of an exhaust as they can get away with without catching the car on fire or poisoning the driver.

Okay, that was a bit more than I expected to type, but oh well.

Gotta go.

 

[le0net]

Thanks for very valuable info, there is one thing i dont understand.
Im adding fuel with the SAFC, does that give a lower Hz value?

I have to add 40% more fuel for the engine to stop knocking, and regarding the boost creep, i think my supporting mods should be able to handle more than 20PSI, dont you think?

50-trim turbo, big FMIC, EVO3 exhaust manifold, EVO3 o2 housing, 2,5">3" Downpipe, 3" downpipe back. Walbro 255 rewired pump, AFP regulator. 660cc Injectors.

Have a ACT 2600 clutch to handle the torque.

Leif

 

[kenamond]

The AFC intercepts the Hz signal from the MAF and changes it. In your case, you're lowering it by 40% to fool the ECU into thinking less air is flowing through the motor (so that it pulses the larger injectors for a shorter period of time). If you just put in the 660s with no AFC, you'd run pig rich, because the ECU would think you still had 450s (or 390s if you have an A/T). But dropping the Hz by 40% doesn't mean dropping the airflow by 40%. The Hz values are converted by the ECU into airspeed. Then the barometric pressure sensor and intake air temperature sensor (also in the MAF) feed the ECU information so that it can compute the density of the incoming air. The speed of the air and density of the air gives the mass airflow (usually lb/min) flowing through the motor. But the point is that 40% lower Hz doesn't mean 40% slower airspeed; the translation is more complicated - and I don't know what it is. So my point about STFT+LTFT is that if you see +10% in your STFT+LTFT, that means the ECU is having to add 10% more fuel to get a stoich AFR in closed-loop operation (not full throttle, mind you). That doesn't mean that you should change the AFC by 10%. It just means that you have to richen it up some and then watch the STFT and LTFT to see what effect the change had.

I should have mentioned before that I'm not an AFC expert. I've learned all of this stuff, thought too much about it, and am giving you the basics. I recommend that you search for AFC tuning threads to learn more details about how it all works and what techniques folks use to tune without a wideband.

Also, you'll eventually learn that the fuel delivery (injector size and fuel pump flowrate) is dependent on more than boost. Although you're probably fine with 660s and Wally255 for 20psi, in general, boost is not the same as airflow which means boost can't tell you how much fuel you need or vice versa. If you have SMIM with ECU-controlled-variable-length runners, cams, extrude-honed head, open DP, tubular mani, huge TB, 10" charge pipes, and an air/liquid-nitrogen intercooler, you'll flow more air and need more fuel at 20psi than a car with stock versions of those parts, and 650s may not be enough. That's volumetric efficiency.

 

[turboAWDfanatic]

Try looking at the STFT+LTFT trims

The fuel trims are different between 1g and 2g. Here's a quote from the Definitive Piggyback Tuning Guide:

1g: 1g's have 4 fuel trims. The low trim is for idle and low rpm cruise conditions. The middle trim is for medium cruse rpm's (1500-2500ish) and the high fuel trim is for 2500+ rpm. The O2 trim is constantly changing with the O2 sensor, and it is what will cause the Long term fuel trims to change.

The approximate airflow ranges for the three trims are:

Low: 0-125 Hz
Mid: 100-175Hz
Hi: 175+ Hz

2g: 2g's only have 2 fuel trims, a long term fuel trim (LTFT) and a short term fuel trim (STFT). The STFT varies with the O2 sensor, an the LTFT goes for every rpm range. Since the STFT directly effects the LTFT, then you can just add the two together, and tune from there. For example, if the LTFT is +20%, and the STFT is -5%, you are at approximately +15%.

And removing a cat decreases backpressure in the exhaust, which decreases backpressure in the exhaust manifold (by even more), which means the pistons don't have to push as hard during the exhaust stroke (exhaust stroke subtracts torque that other power-stroking-pistons are generating), so decreasing the work it has to do increases overall torque) and intake air enters a combustion chamber with a lower pressure (get more air/fuel in the cylinders and less remnant exhaust) which adds torque. The car will flow more air at the same level of boost (higher VE). Turbo race cars have as short of an exhaust as they can get away with without catching the car on fire or poisoning the driver.

True, but my point is that the gains from removing the cat are minimal compared to the fact that it shoots your emissions to hell and is a big factor in causing boost creep. Removing the cat is a no brainer in a RACE car, but for the street I just recommend getting a high flow cat so you can avoid creep and pass emissions.

Thanks for very valuable info, there is one thing i dont understand.
Im adding fuel with the SAFC, does that give a lower Hz value?

No. Kenamond posted some great info, but I think he thought you were pulling air (/fuel) out with your AFC. The way I understand it, as you go negative, the ECU thinks there's less air, and you end up with more aggressive timing (more advance). If you add air (/fuel), the ECU thinks there's more airflow and you get less aggressive timing. Here's another quote from the tuning guide:

By leaning out the SAFC (big injectors, more fuel pressure, race gas) you decrease the amount of airflow that the ECU sees, and therefore you usually will get a bit more timing advance for power. This all assumes you have no knock, and also keep in mind that more timing advance will have an engine a higher propensity to knock.

I have heard of 1g guys with 660 cc/min injectors getting timing advanced as much as 28+ degrees at WOT, because you hve to pull the SAFC correction factors down a lot due to the fact that 660's are 47% bigger than the stock 450's.

I have to add 40% more fuel for the engine to stop knocking, and regarding the boost creep, i think my supporting mods should be able to handle more than 20PSI, dont you think?

I'm finding it odd that you have to add +40% with 660's! Typically with 660's people have to pull around 25-30% out so that the car doesn't run mad rich. Here's where the whole timing thing comes in. A lot of people say not to go above 550's if all you have is the AFC b/c you'll get way too agressive timing by subtracting a lot of air w/ the AFC. You combat this by either getting timing control (modified chip, DSMLink, AEM), or you can throw in a 2g MAF. With a 2g MAF, you have to enrich the mixture on the AFC to compensate. Then you have to lean it out for the 660's. With both the 2g MAF and 660's together it puts the airflow that the ECU sees closer to what's really going through the engine.

BUT, all that doesn't really apply since you're *adding* air/fuel with the AFC. This is where I have to stop b/c I'm not a tuning guru yet, and I don't understand why you would have to add that much air/fuel with the AFC when you have 660's and a Walbro 255 while boosting less than 20psi. Keep digging around. Read through the definitive piggyback tuning guide I posted above. There's more tuning guides in the tech section. It's good that you're not getting any knock now , but you'll definitely get more power and better reliability once you're fine tuned and have timing exactly where you want it.

 

[le0net]

Could the reason be that i have a 3" GM MAF in blowtrough mode and a MAF-T instead of the stock MAF?

L

 

[95CarbonEclipse]

Wow.. this is a great thread, as I'm a complete tuning newb (I don't even own an AFC or any other way of changing A/F ratio's) all I own is a logger right now. Keep the information gates flowing!!

Thanks!