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View Full Version : Help: Weird AFR Curve *image*



Monk
12-13-2007, 09:53 AM
Car is a B5 A4 nDBW 1.8TqM (AEB).

Had my ride dynoed several months ago. The AFR curve on top is from my 1st session. The curve curiously starts to spike at around 4.5T RPM. We stopped the run at a little past 5T RPM since AFR has already gone up to 13.5 & seems to be leaning-out more.

We decided to replace the stock fuel pump with a Walbro 255LPH unit. Result . ..I am now running pig-rich midrange as evident in the bottom AFR curve. I'm losing plenty of midrange torque because of this (check graph on the left). What concerns me is the 'shape' of the curve, w/c remains the same & only shifted downwards after the Walbro install. There is still this abrupt spike after 4.5T RPM.

I've contacted ATP, and they feel that it could be either the FPR or MAF sensor (both are stock in my car). Of course, it could also be their tuning.

The car still pulls well though, but it does bog-down once in a blue moon when it gets flooded with fuel @ WOT. Would appreciate any inputs on why my AFR is spiking around 4.5T RPM & how can I solve my overly rich midrange.

note: 19.5PSI w/ a MBC on both runs.

http://i261.photobucket.com/albums/ii68/tejaro12/GTRSAFR.jpg

pmoss
12-13-2007, 10:45 AM
An adjustable fpr and a brand new Maf element would'nt be a bad idea but your main problem is the tuning. Mica sucks based on first hand experience. Search Mica for more of the same.

Monk
12-13-2007, 11:17 AM
Yes, I am aware of the reviews on the Mika tune. There's a shop here who's willing to do a dyno based custom tune. But I want to take the simpler route first. As you've said, an adjustable FPR & a new MAF element would be a good start.

t1demont1
12-14-2007, 03:41 AM
Id get rid of that mika tune, too many stories of blown motors from those tunes

ILoveT
12-14-2007, 10:22 AM
But I want to take the simpler route first.

There might not be a second route if you keep that tune.

pmoss
12-14-2007, 10:26 AM
What about the classifieds for a used chip for a t28 or gt28rs - that may be better then what you have and not too expensive.

maxspeed
12-14-2007, 11:24 AM
guys the reason, the mika tune sucks is because it runs lean as fuck on the stock fuel pump.

he has OBVIOUSLY taken car of that problem, so STFU about the mika tune, its obviously not plug and play like they say, it dosent have agressive timing or anything like that.... it just runs lean on the stock fuel pump (REALLY LEAN). and thats why so many people pop there motors with it

to the OP:
try an adjustable fuel pressure regulator to bring that shit back a drop. 11.5's perfect, if you can keep it above 10.8 - 10.9 and below 12.5 you should be golden, do you have an onboard wideband, or are you paying for dyno runs? also dont worry about the shape of the a/f curve, where it settles to is perfect, the adj FPR should keep you from getting that rich

Don Supreme
12-14-2007, 01:42 PM
Stop everything and get another tune.

End of story.

mike-2ptzero
12-14-2007, 03:51 PM
guys the reason, the mika tune sucks is because it runs lean as fuck on the stock fuel pump.

he has OBVIOUSLY taken car of that problem, so STFU about the mika tune, its obviously not plug and play like they say, it dosent have agressive timing or anything like that.... it just runs lean on the stock fuel pump (REALLY LEAN). and thats why so many people pop there motors with it

to the OP:
try an adjustable fuel pressure regulator to bring that shit back a drop. 11.5's perfect, if you can keep it above 10.8 - 10.9 and below 12.5 you should be golden, do you have an onboard wideband, or are you paying for dyno runs? also dont worry about the shape of the a/f curve, where it settles to is perfect, the adj FPR should keep you from getting that rich

That still isn't going to fix his issue of it getting leaner as the rpms get higher after the AFR has dipped down to its richest point. Problem could be the maf he is running or the fact that the fuel map and adv timing maps aren't all that thought out when the tuner did the chip.

BTW a stock fuel pump and stock maf is not going to cut it when running a GTrs.

andyrew
12-14-2007, 06:05 PM
Any way you can modify that tune?? If you can, do it. Also adjustable FPR will help, but definately not solve the problem.

This problem has to be fixed with a modified tune. I normally run stand alones or piggy back systems, so Im not sure if theres a way to modify this...

Possibly talk with Revo and tell them whats up with there tune and that it should be 11-12.5 flat across the board under full throttle in any situation. Especially with an O2 sensor... Maybe ask them if theres a way they could modify your tune for a fee?

Hope that helps

xr4tic
12-14-2007, 06:35 PM
what size injectors are you running?

a simple fuel pump swap should not result in a totally different fuel curve.

If the stock fuel pump was bad, they would still follow the same curve for a while, then the stock would lean out. In this case, they are not even close, they're 3 points off.

What is your long term fuel trim? It's possible you are running lean during part throttle cruising, so the fuel trims add fuel, then when you go WOT, it uses that fuel trim, and it's way too rich.

Monk
12-14-2007, 07:42 PM
to the OP:
try an adjustable fuel pressure regulator to bring that shit back a drop. 11.5's perfect, if you can keep it above 10.8 - 10.9 and below 12.5 you should be golden, do you have an onboard wideband, or are you paying for dyno runs? also dont worry about the shape of the a/f curve, where it settles to is perfect, the adj FPR should keep you from getting that rich

Wouldn't an AFPR simply shift the curve upwards or downwards? So even if I get the midrange to settle in the 12's, I'd still be spiking towards the 13.5s near redline (back to square one). Yes, I'm happy with where it settles now (11.5), but I'm losing HP & TQ on the way there (refer to image for dip in TQ) . ..I use the Innovate XD-16 kit to monitor my AFR.

Monk
12-14-2007, 07:48 PM
BTW a stock fuel pump and stock maf is not going to cut it when running a GTrs.

What upgraded MAF element would you suggest? I'm just using stock on a 3'' housing at the moment.

mike-2ptzero
12-14-2007, 08:00 PM
Wouldn't an AFPR simply shift the curve upwards or downwards? So even if I get the midrange to settle in the 12's, I'd still be spiking towards the 13.5s near redline (back to square one). Yes, I'm happy with where it settles now (11.5), but I'm losing HP & TQ on the way there (refer to image for dip in TQ) . ..I use the Innovate XD-16 kit to monitor my AFR.


Correct, even if you were to set the AFPR so that it dips down to 10:1 you will still end up in the 13:1. You really do need a new tune or do more logs with the vag-com to see what the issue might be.

As for the maf, if you are using a 3" housing then your fine since the sensor should never max out.

Monk
12-14-2007, 08:03 PM
Any way you can modify that tune?? If you can, do it.

If my memory serves me well, nDBW B5 EPROMs are none-flashable. So I would have to get off-the-shelf stuff or have a tuner use an emulator while on the Dyno, then have the gathered data burned onto a blank chip. I am just trying to make sure that the AFR 'spike' is not being caused by a simple hardware problem before I take the custom-tune route. By the way, I already have a 'socket' soldered onto the EPROM slot to facilitate chip switching.

Monk
12-14-2007, 08:39 PM
what size injectors are you running?

a simple fuel pump swap should not result in a totally different fuel curve.

If the stock fuel pump was bad, they would still follow the same curve for a while, then the stock would lean out. In this case, they are not even close, they're 3 points off.

What is your long term fuel trim? It's possible you are running lean during part throttle cruising, so the fuel trims add fuel, then when you go WOT, it uses that fuel trim, and it's way too rich.

RC 550cc's . ..As for the curve, it is possible that the readings were affected by say 'a fouled-up 02 sensor' or other factors during the first run. But midrange HP & TQ were greatly affected on the 2nd session, so fuel-flooding is present. It says 9.9 on the graph, but I'm actually off-the-charts at this point . ..I'm bouncing around 13's to 15's during part-throttle cruising (have to double check though).

xr4tic
12-14-2007, 10:14 PM
RC 550cc's . ..As for the curve, it is possible that the readings were affected by say 'a fouled-up 02 sensor' or other factors during the first run. But midrange HP & TQ were greatly affected on the 2nd session, so fuel-flooding is present. It says 9.9 on the graph, but I'm actually off-the-charts at this point . ..I'm bouncing around 13's to 15's during part-throttle cruising (have to double check though).

Part Throttle cruising AFs are misleading, they will bounce around, but the ECU is automatically compensating to achieve stoich. You need to hook up a VAG-COM to see your fuel trim values.

The O2 sensor is ignored during WOT, but the fuel trims are still used, so if your part throttle map is off, youre WOT AF will suffer as well (been there, done that)

xr4tic
12-14-2007, 10:17 PM
As for the maf, if you are using a 3" housing then your fine since the sensor should never max out.

Funny, I maxed my stock MAF element in a 3" housing at ~325 crank HP (2.0 at 18psi)

I wish that wasn't the case, but it's definately easy to max out a nonDBW MAF in 3" housing.

Don Supreme
12-15-2007, 08:45 AM
Tuner can change the scaling guys.

stretch1.8
12-16-2007, 11:52 AM
I'm having the same issue with my 1999.5 A4 1.8QTM. My car is in the 14 - 15 to 1 AFR on partial throttle. On WOT the AFR continues to clime from thirteen and doesn't show any sign of stopping. My car also shuts off while coming to stops every now and then, my check engine light is always on now and the car shuts down every time I go on boost.

I think this is absolutely ridicules. It's obvious that the Mika tune isn't effective, and most importantly, unsafe.

Have you tried returning your ECU to be reflashed with your original settings and receiving a full refund. It's obvious that we are both risking our motors by using the Mika tune. It's marketed as a complete solution to your tuning needs for the GTRS kit, and it absolutely doesn't do that. I would expect to get this kind of result if I tried to run the GTRS with my stock tune, not a tune that I purchased specifically for the GTRS kit. I didn't get my car dyno tuned to avoid situations like this.

The purchase of this tune is a form of contract between the vendor and customer. The product not performing to its advertised specs is a breach of contract. We can't let the vendor of the hook by looking for work arounds for their products inadequate performance.

mike-2ptzero
12-16-2007, 04:13 PM
Funny, I maxed my stock MAF element in a 3" housing at ~325 crank HP (2.0 at 18psi)

I wish that wasn't the case, but it's definately easy to max out a nonDBW MAF in 3" housing.

Well just be glad you were a ndbw, on the dbw when you max out the maf the ecu closes the throttle. That was the exact problem I had right before going to the stand alone, maxxed out the stock sensor in a 3.5" housing making about 577chp.

stretch1.8
12-16-2007, 06:23 PM
I don't even see how the MAF could be maxing out already. It's cutting out without even getting a chance to pull hard, something like 3500 or 4000 RPM.

What kind of stand alone are you using? I'd prefer to get my ECU chipped with a generic tune that works. Is there anyone out there that provides a reliable tune that actually works?

This is starting to get very frustrating

317ssayzarc
12-16-2007, 06:30 PM
a tapp tune could solve all your problems... you will need 630cc injectors and a 90mm ford maf... your car will run as good as stock [up]

stretch1.8
12-16-2007, 06:59 PM
Thnx for the advice.

Do you know of anyone that runs the TAP tune?

317ssayzarc
12-16-2007, 07:50 PM
i have it for my bt build... forcefed engineering just did a 3076r audi with it... search tapp or eurodyne on vwvortex and you will get lots of info [up]

Monk
12-16-2007, 11:50 PM
Have you tried returning your ECU to be reflashed with your original settings and receiving a full refund. It's obvious that we are both risking our motors by using the Mika tune.

Since I'm based abroad, it would be impractical & risky to have my ECU shipped back & forth from ATP's HQ. Plus, the pre-facelift B5's like mine have non-flashable ECU's, w/c is why I had ATP send the actual EPROM chip (I have a socket soldered-on, so chip switching is fairly easy). I haven't tried plugging back my Superchips KO3 software to run the GTRS, coz I'm not having as many problems as you're experiencing. Moreover, we partially solved my lean mixture in the high RPMS @ WOT by switching to a Walbro. The car still pulls well. It's only in track conditions that you miss the midrange TQ that was present when the car was running lean w/ the stock pump.

stretch1.8
12-19-2007, 09:01 PM
I switched back to my stock MAF housing and the car is now running a little ritch, but much better than before. It doesn't cut out under boost anymore and it hasn't cut off yet. ,,,,can't get on the car yet. I have a faulty boost line. I'll let you know how it runs once I can boost it.

Monk, what were your 1/4 mile times before you switched to the Walboro and what are you times after the switch?

mike-2ptzero
12-20-2007, 05:56 AM
I don't even see how the MAF could be maxing out already. It's cutting out without even getting a chance to pull hard, something like 3500 or 4000 RPM.

What kind of stand alone are you using? I'd prefer to get my ECU chipped with a generic tune that works. Is there anyone out there that provides a reliable tune that actually works?

This is starting to get very frustrating

Have you logged your maf readings with a vagcom?



I am running a 034 EFI stand alone.

Monk
12-20-2007, 11:04 PM
I switched back to my stock MAF housing and the car is now running a little ritch, but much better than before.

Good to hear.


Monk, what were your 1/4 mile times before you switched to the Walboro and what are you times after the switch?

I have not done timed quarters yet. When I said 'track conditions', I was referring to circuit tracks. The car used to feel livelier powering out of corners before the fuel pump swap. Unfortunately, I don't have timed laps before the Walbro install, so there's no basis for comparison. I also have a horrendous handling car at the moment due to an oversized rear swaybar paired with a stock front. My tail steps out with the least provocation (but this is another topic altogether). Anyway, glad to hear that you're beginning to sort things out with regards to your ride.

mike-2ptzero
12-21-2007, 04:31 AM
Good to hear.



I have not done timed quarters yet. When I said 'track conditions', I was referring to circuit tracks. The car used to feel livelier powering out of corners before the fuel pump swap. Unfortunately, I don't have timed laps before the Walbro install, so there's no basis for comparison. I also have a horrendous handling car at the moment due to an oversized rear swaybar paired with a stock front. My tail steps out with the least provocation (but this is another topic altogether). Anyway, glad to hear that you're beginning to sort things out with regards to your ride.



Yeah because your car was running dangerously on the lean side and I bet the EGT's were much higher then they would be at this point. Now you just need to get a tune that allows you to hit 11.5:1 and hold it till redline or even if it dips to 11.0:1 and settles up a little higher at 12:1 by redline.

stretch1.8
12-22-2007, 02:25 PM
Thanks guys. Your adivce really helped. I'm not quite out of the woods yet though.

Does anyoe know how much boost I can run with the GTRS on my stock mount intercooler? I have the front mount but just don't feel like spending any more time in a cold garage right now. I think I'll wait until March or April to instal it.

Stiffen up your front end and you regain your all wheel drive advantage

Monk
12-26-2007, 04:07 AM
Does anyoe know how much boost I can run with the GTRS on my stock mount intercooler? I have the front mount but just don't feel like spending any more time in a cold garage right now. I think I'll wait until March or April to instal it.

We usually experience scorching tropical weather where I live, so I tend to stay on the conservative side when it comes to boost. I set my MBC to around 18.5PSI for the GTRS. Are you still running the N75 solenoid?



Stiffen up your front end and you regain your all wheel drive advantage

32MM H&R front swaybar is on its way. Current handling is acceptable up to aggressive canyon carving, but it's really a handful at the circuit.