MAFT/S-AFC Tuning advise

[Chicken Patty]

Hi guys, I have a question about the MAFT tuning with an S-AFC.

To my understanding you can just setup the necessary adjustments on the MAFT but leave your Idle/Mid/WOT trims at default and tune with the S-AFC like if the MAFT was not even there. However, I did that and the car had a considerable loss in performance. I set the AFC to +/- 0 and gave it a base tune with the MAFT. Now the car is still running rich up top and it feels soooo much faster. I still yet to fine tune with AFC. Anybody can explain why the difference by adjusting the MAFT?

Another question. If you are already taking away let's say -10% with the MAFT and you have a slightly lean spot in the powerband, you can actually go on the positive side with the afc to fine tune correct? With just a straight AFC this is not typical because you are causing the ECU to register more than what is really going in to the motor, but if you are already reducing the signal with the MAFT, going positive on the AFC shouldn't be an issue correct? Thanks in advance for any advise guys.

 

[rstchris]

It is easy to kill things while tuning without a wideband and hard to even get it close. If there is a noticable change in performance then big changes are being made to the stock tune and hard to tell when and where you need more fuel or less fuel. If you can't buy one then atleast try to borrow one from a friend for a day. To answer the question, YES you can add fuel with the afc but try to keep it to a minimal for wot.

 

[Chicken Patty]

It is easy to kill things while tuning without a wideband and hard to even get it close. If there is a noticable change in performance then big changes are being made to the stock tune and hard to tell when and where you need more fuel or less fuel. If you can't buy one then atleast try to borrow one from a friend for a day. To answer the question, YES you can add fuel with the afc but try to keep it to a minimal for wot.

I do have a wideband. I am also saving up for a data logger. But I do have a wideband and at no moment the car has been really lean. Just that when adjusting with the MAFT from between 3-4k it is like 12.4-12.5, i rather it be about 11.8-12.0 since it's fairly low and power has just started to come in, then 11.6-11.8 the rest of the way up. with the MAFT it is about 12.4-12.5 down low during spool up, and then runs under 11's up top after about 5.5k. So was just wondering if it was ok to add a bit with the SAFC downlow to even it out with the top of the power band.

 

[rstchris]

You should fatten it up in the 35-55 area cause thats where you will make the most boost (assuming it bleeds off) and keep timing low til the fuel part is tuned. Datalogging is the best way to get trims in check. I try to run +-10% then wot on pump about 12.0 for the first few psi. 7psi and up I would run 11.5. Some others like to run richer then that. You can make more power by adding a bit more fuel and timing as opposed to less fuel and less timing as long as you stay away from the 10.9 or richer area as you may feel like the car is towing jetskis. Your best bet might be to get the translator as close to "stock" as possible and make minor changes with the afc. To answer te question, yes you can add with afc but try not to add up top as you may reach the load cap.

 

[Chicken Patty]

You should fatten it up in the 35-55 area cause thats where you will make the most boost (assuming it bleeds off) and keep timing low til the fuel part is tuned. Datalogging is the best way to get trims in check. I try to run +-10% then wot on pump about 12.0 for the first few psi. 7psi and up I would run 11.5. Some others like to run richer then that. You can make more power by adding a bit more fuel and timing as opposed to less fuel and less timing as long as you stay away from the 10.9 or richer area as you may feel like the car is towing jetskis. Your best bet might be to get the translator as close to "stock" as possible and make minor changes with the afc. To answer te question, yes you can add with afc but try not to add up top as you may reach the load cap.

I'm going to just give it a baseline tune for now so that the a/f is not all over the chart. When I get a data logger I'll try again leaving the MAFT on zero all across and just tuning with the s-afc as I did when I had the stock MAF. Then I can monitor what is going on. For now It's fine, I'll just put the finishing touches for now until I get the rest of my fuel system on and buy a data logger.

 

[JayRolla]

U need to set up the maft for just the injectors. If u get the injectors setup on the maft then u should be close. Like stated tune afr at wot too 10.9-11.5 at leanest if running pum gas. I was able to run more boost at 11.1 than 11.5 so I used to run rich.

 

[dsmfa9nutter]

Set the injector size on the maf-t and fine tune with the afc.

 

[Chicken Patty]

Guys, I'm looking for a data logger, any recommendations?

 

[dsmfa9nutter]

Standard palm and mmcd combo works fine for most.

 

[Chicken Patty]

Standard palm and mmcd combo works fine for most.

Thanks for your response.

however, the pocket logger seems to be discontinued. Only chance would be to get one used. Unless there is another place to get them.

Do you have a link to the MMCD one? Not sure I've heard of that before.

 

[Ceddy]

MMCD is for 1Gs.

For software most 2Gs are using EvoScan($25), its for Evos but works for us also.
(Logs Knock, Injector DC, etc, that a OBD2 logger won't)

For a cable the VAG 409.1 cables can be had on ebay for ~$20.


If you want something prepackaged, with correct drivers, cable, software, etc. -> DSMChips.com | DSM ECU Chips Enchanced by Keydiver

 

[Chicken Patty]

MMCD is for 1Gs.

For software most 2Gs are using EvoScan($25), its for Evos but works for us also.
(Logs Knock, Injector DC, etc, that a OBD2 logger won't)

For a cable the VAG 409.1 cables can be had on ebay for ~$20.


If you want something prepackaged, with correct drivers, cable, software, etc. -> DSMChips.com | DSM ECU Chips Enchanced by Keydiver

That package sounds like a winner to me. I can get a hold of a laptop with no issues. $50 sounds really good. I'm going to order this as soon as I deposit my check tomorrow. Thanks a lot for the links/help guys. I'll report back when I have an update.

 

[kyouichiGST]

is this ONLY a logging tool or can I adjust fuel trim with it as well?

 

[Rengar18]

Evoscan is just a logging tool.

 

[Chicken Patty]

Hey guys,

I finally got my EVOSCAN. Now I have just one question. I heard knock sum is not viewable on loggers for us 2G owners? Is this true? Mine displays 1 count of knock all across the band, but maybe it's just a false reading or something?

I will post some logs another day, laptop died after a few pulls so I wasn't able to do much. At least I found out I was pushing my injectors over their limit and I backed down the boost. at 17psi my A/F was fine but my duty cycle peaked at 93.87%. so I brought boost back down to 14.5-15.5 psi and the peak duty cycle for about 300 RPM's was 90.11% for those 300 RPM's only, before or after that part of the power band it was under 90% the whole time, that should be fine right?

 

[jeffo]

What year ECU are you running? The knock address is different, depending which ECU you are logging. You set the address to 3E to log a 1995/96 ECU, and 26 for 1997+ ECU's.

 

[Chicken Patty]

What year ECU are you running? The knock address is different, depending which ECU you are logging. You set the address to 3E to log a 1995/96 ECU, and 26 for 1997+ ECU's.

I'm on a 97 ECU. I remember now reading somewhere about this value that you had to change. I'll give that a shot tomorrow Thanks for the info.


However, now I got one question, this has really been bugging me about the car.

If I do a pull or two, my a/f is fine. between 11.6-11.8 in 3rd gear. However, after two pulls or so my a/f starts to rich out a lot. It starts to go under 11's. What can this be? I've let the car cool down for five or ten minutes and still the same. I get in it the next day and do a pull and it's fine. Any suggestions?

 

[bboyalan]

If I do a pull or two, my a/f is fine. between 11.6-11.8 in 3rd gear. However, after two pulls or so my a/f starts to rich out a lot. It starts to go under 11's. What can this be? I've let the car cool down for five or ten minutes and still the same. I get in it the next day and do a pull and it's fine. Any suggestions?

That can be attributed to boost leaks that make themselves apparent under hot conditions [repeated pulls]. This could be anything from intake to injector seals. How can this be a cause you ask? Fuel is injected based on MAF/load, so if that metered air is escaping... you will have more fuel than air [richer]. It is basically the same reasoning behind open-loop BOV's on stock draw-thru configuration.

You should be okay at those IDC's so long as you do not encounter any crazy overboost.

 

[Chicken Patty]

That can be attributed to boost leaks that make themselves apparent under hot conditions [repeated pulls]. This could be anything from intake to injector seals. How can this be a cause you ask? Fuel is injected based on MAF/load, so if that metered air is escaping... you will have more fuel than air [richer]. It is basically the same reasoning behind open-loop BOV's on stock draw-thru configuration.

You should be okay at those IDC's so long as you do not encounter any crazy overboost.

Thanks for the response. Yeah I have yet to boost leak test the car recently. I have been trying to do it but have not gotten around to it. Before I keep breaking my head over this I'll give that a shot and see how it goes. I'll post back with my results when I get around to it.

 

[Chicken Patty]

Alright guys.

I put in my Siemen Deka 750cc Injectors yesterday and I started to dial in the car. I had my MAFT originally set at 650cc for compensation. With this in order to more or less dial in my A/F Ratio to about 11.1-11.5 I had to pull about 30% fuel. However at that point, The car would fall on it's face after about 6500RPM and it started breaking up. When I checked the logger it had timing jump up to 38 degrees.

So then I tried the MAFT at 750cc for compensation and with the afc on zero and the a/f below 11.1 I did a pull at about 20-21 psi which was the same boost as above and the same thing happened. If I drop the boost to about 18-19psi the car looses power up top, but finishes the pull. Up the boost a psi or so more and it breaks up. Please note what is happening is NOT fuel cut, I know the difference between the two.

here is my log for when the car broke up and I had to let off. Reason why I was not logging knock is because the reading has to be wrong. Getting like over 30 counts of knock, however in previous pulls where it says 30 counts of knock my timing would be at about 17-19 degress. If it was really knocking that much shouldn't the timing start to drop??? I know the sensor can pick up knock due to vibrations like bad axles and dumptubes and stuff. My car does have a slight vibration even when driving regularly.

So if you guys can take a look at the log and give me some feedback I'd really appreciate it.

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[bboyalan]

Thanks for posting the datalog for reference; I always do the same. You were only hitting peak 20* during WOT. TIMA jumped back to 38* when you were letting off the throttle.

Can you elaborate more on this "breaking up" symptom? Perhaps it is spark blowout because you mentioned being able to complete a pull after backing down on the boost. It also looks a little rich at 0.96-0.98v NBO2. Even on pump, ~0.94 should be easily attainable with little to no detonation.

 

[Chicken Patty]

Thanks for posting the datalog for reference; I always do the same. You were only hitting peak 20* during WOT. TIMA jumped back to 38* when you were letting off the throttle.

Can you elaborate more on this "breaking up" symptom? Perhaps it is spark blowout because you mentioned being able to complete a pull after backing down on the boost. It also looks a little rich at 0.96-0.98v NBO2. Even on pump, ~0.94 should be easily attainable.

Thanks for the quick reply, I figured the log would really help.

yesterday when I was dialing in the car at first I had left it a bit richer than now, at the same boost level. I had at the time the MAFT set at 650cc for compensation. The car was pulling fine at this boost. This "SHOULD" rule out spark blowout. I have brand new BR7ES plugs gapped at .028.

However, today I tried to dial it in a bit more since it was rich and as I pulled a bit more fuel the car after 6200~ RPM's would fall on its face, you can tell it lost power all the way to redline. As I leaned it out a bit more the next pull when it got to about 6500-6800 it just broke up and started to buckle in and out and I let off. That's when the logger hit 38º of timing. After that I tried the MAFT set to 750cc hoping that I had to pull away less fuel with the AFC and hopefully keep my timing lower. However with the AFC at zero the result is above.

My guess is, I might have to try the MAFT set at maybe 680-700cc for compensation and then dial it in via AFC then. If that does not work then looks like the problem is a bit more complicated.

 

[bboyalan]

Haha NP =] and it always helps for diagnosing and learning too.

Those plugs should be good, so we should be able to rule out blowout like you said.

I just caught glimpse of your knock situation. Have you inspected your sensor for looseness or goo? Constant counts that high will definitely throw off the ECU's calculations. While it is supposed to progressively advance timing, it will also try to retard+leave it alone to save the engine.

//edit// BTW, what are your Tru-Boost's settings? Specifically, what is the spring rate at?

 

[Chicken Patty]

Haha NP =] and it always helps for diagnosing and learning too.

Those plugs should be good, so we should be able to rule out blowout like you said.

I just caught glimpse of your knock situation. Have you inspected your sensor for looseness or goo? Constant counts that high will definitely throw off the ECU's calculations. While it is supposed to progressively advance timing, it will also try to retard+leave it alone to save the engine.

//edit// BTW, what are your Tru-Boost's settings? Specifically, what is the spring rate at?

No I have not inspected the knock sensor yet as this just came to my attention yesterday night.

My TRU Boost is at I believe 55% for 21psi or so.

Spring rate is set to 10psi since I have a 1 bar spring.

 

[Chicken Patty]

Ok, I dialed in the car again today without the car breaking up or what not. Tried the MAFT to compesate on 680cc's and it runs great. Boost is about 20-21psi timing peaks at 21 at about 6-6.5k, then maintains and drops off a degree or so at 7.3-7.5k.

I do however keep getting the knock counts. about 7 downlow from 4k-5k, then goes to zero then back up to 15, then drops and at redline comes back up to like 12. It's inconsistent and just seems wrong to me. Any input guys?

I lent my Flash Drive to a friend. I'll try to get it back as soon as possible and I'll log a run for you guys so that you can see exactly what is going on.