Ask a tuner...

[TruStinger]

lets say I have a car that operates at 58psi. I add 2 walbros to it that run all the time and keep the psi regulated at 58psi. Should I have to retune my ECM? And if not could my DOFC get messed up causing backfires?

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[P3Auto]

Originally Posted by TruStinger

lets say I have a car that operates at 58psi. I add 2 walbros to it that run all the time and keep the psi regulated at 58psi. Should I have to retune my ECM? And if not could my DOFC get messed up causing backfires?

Hmm way more information needed.

What was the original fuel pressure?

Please tell me what DOFC stands for?

Backfires can be caused by all sorts of fun stuff. What kind of EFI are we dealing with? Does it have a MAF or MAP or both?

[TruStinger]

58psi both stock and currently. DFCO(misspelled it earlier), deceleration fuel cut off. Im told it cuts fuel when you let off the gas so it doesnt dump a bunch of fuel causing a rich condition. This is on an LS1, running an OL SD tune.

[AKSubieDubie]

I can see that. I remember reading on a thread about the same theory. I played with it a bunch and didn't really see any difference in learned knock values.

I think I'll be zero-ing them out when I finally build a set of equal length headers, as my current tune seems to be spot on with timing. Been ripping around with the 30r maxxed out for about 20k miles! (motor has 24k on it since rebuild)

Just something to think about.

Thanks!

Originally Posted by P3Auto

Ok are you ready for this?

The reason that I at least feel Subaru runs slightly more advanced timing on the back pistons is because of the position of the knock sensor. The engineers wanted slight knock to be heard the best. By advancing the cyls closest to the knock sensor it will hear and detect knock where it might miss slight knock from a front piston.

Ever wonder why the back pistons seem to be the winner for piston damage...If we look at an 05 STI tune we will find the front cyl timing is retarded as much as -3 degrees at certain rpms while the rear cyls are not retarding timing at all.This may not seem like a lot of timing difference but even slight knock can turn severe quickly. In other words 20 degrees may not knock at all, where as 21 degrees may start to knock. Iit might take 3-8 degrees of timing reduction to quiet the knock started by the 1 degree of advance.

This is why many Subarus I have had to tune had "flat spots" around 5000RPM or so. The car was detecting knock but having a knee jerk reaction pulling timing out to stop it. By reducing timing a little in the hot spots the end result is more power and timing since the ECU won't be having to pull gross amounts to stop the knock event.

Sorry got off on a bit of a rant.

To summarzie, I see no reason to mess with the per cyl timing compensation tables. I'm sure there is some optimization that could be done but it would require special equipment to monitor each cyl for temp, pressure, etc.

[P3Auto]

Originally Posted by TruStinger

58psi both stock and currently. DFCO(misspelled it earlier), deceleration fuel cut off. Im told it cuts fuel when you let off the gas so it doesnt dump a bunch of fuel causing a rich condition. This is on an LS1, running an OL SD tune.

I don't see any reason why changing the pumps would make a difference to that DFCO system. The pressure is the same so it would have changed nothing other than adding more flow when needed. I would have to research how the DFCO system works exactly. I'm sure I could figure it all out with time and the car. Have you tried other forums? I would be interested in seeing your car sometime, if you don't get it worked out stop by some day.

[TruStinger]

Having some people over to help me with it, youre welcome to stop by. I need to install my tuning software on my laptop tonight.

[P3Auto]

Originally Posted by AKSubieDubie

I can see that. I remember reading on a thread about the same theory. I played with it a bunch and didn't really see any difference in learned knock values.

I think I'll be zero-ing them out when I finally build a set of equal length headers, as my current tune seems to be spot on with timing. Been ripping around with the 30r maxxed out for about 20k miles! (motor has 24k on it since rebuild)

Just something to think about.

Thanks!

I would not zero them out, if you coming within 1-3 degrees of knock you should be adjusting your timing for that load/rpm range. Even forged pistons can break with knock or at least rip up your rod bearings. I don't think this theory about exhaust making a difference makes an sense. More or less spark timing within a few degrees all happens with the exhaust and intake valves shut. Regardless I doubt any real gains are here plus on your car were talking about 1-3 degrees between just 5200-6400 rpm. Tiny window...

[P3Auto]

Originally Posted by TruStinger

Having some people over to help me with it, youre welcome to stop by. I need to install my tuning software on my laptop tonight.

I have to much work at my shop right now to hang out with you guys, I wish I could though. Always got a kick out of turboed domestics.

[P3Auto]

Always keep an eye on your DAM/IAM..Anyone who has and AP2 can see it on demand, otherwise you need a tactrix cable and a free program called "learningview.exe".

STIs should be a 1.0 for best and never below a .5
Early 2.0l WRXs should be a 16 and never below an 8
2.5l WRXs are the same as the STIs 1 for best and never below .5

If you ever do find your not at the max you problably have very poor fuel, a tuning issue, boost leaks, manifold leaks, blocked intercooler, and a few more items.

I just got a car dropped off last night that has an IAM/DAM of 0 and its a WRX, bad bad hope the internals are still ok.

[Brando5185]

Originally Posted by P3Auto

Always keep an eye on your DAM/IAM..Anyone who has and AP2 can see it on demand, otherwise you need a tactrix cable and a free program called "learningview.exe".

STIs should be a 1.0 for best and never below a .5
Early 2.0l WRXs should be a 16 and never below an 8
2.5l WRXs are the same as the STIs 1 for best and never below .5

If you ever do find your not at the max you problably have very poor fuel, a tuning issue, boost leaks, manifold leaks, blocked intercooler, and a few more items.

I just got a car dropped off last night that has an IAM/DAM of 0 and its a WRX, bad bad hope the internals are still ok.

My AP2 is permanently mounted on the dash and shows DAM 95% of the time lol. Only time it dropped to .9 was at a rallycross bouncing of rev limiter. Gave it right back the next run and hasn't dropped from 1.0 since. Even on 90 octane. Car must have a good tune or something on it.

[P3Auto]

Or a nice safe one. Even so always check it if things sound different or feel different, it can be a nice quick indicator of engine happiness.

[Brando5185]

Yeah a very safe one.... for now. I always listen to the car. My wife gets mad b/c I tell her to be quiet alot if I think I hear something strange lol.

Is there more we can do to get quicker spool? The FMIC took away some of my rpm's.. :-(

[KW900]

Using EFI Live?

Originally Posted by TruStinger

Having some people over to help me with it, youre welcome to stop by. I need to install my tuning software on my laptop tonight.

[TruStinger]

Originally Posted by KW900

Using EFI Live?

HP tuners.

[P3Auto]

Originally Posted by Brando5185

Yeah a very safe one.... for now. I always listen to the car. My wife gets mad b/c I tell her to be quiet alot if I think I hear something strange lol.

Is there more we can do to get quicker spool? The FMIC took away some of my rpm's.. :-(

Yes and no.

We can do a boost leak check to be sure all the joints are sealed, its quite common from FMICs to have little boost leaks when you first install them. If you do have any leaks that will help.

We can put a few little tweaks on the AVCS portion of the tune. I have some maps that my buddy did on a dyno with a DOM3 and an 05 STI. The 20g will be close. This will give you a little more power prior to spool and help a little.

We could also get fancy with timing and fuel prior to spool to kick the turbo a bit but its kind of a balancing act and the returns are not that great.

The reality is you added a lot of pipe that has to charge with air now. You could also consider inverting the intake so the FMIC pipes come in the front of the engine. This shortens them a bit but you would have to sacrifice A/C and move the alternator I believe.

I also have an off the line anti-lag / launch control hack that will give you about 10-15PSI standing still.

By the way we can add a few degrees of timing with that FMIC over what you had and still be in the safe zone. You have not realized the gains of the FMIC until you retune a little especially in Alaska. I doubt the oversized TMIC was really doing that bad but now your ready to flow more air and still keep it cool.

[Brando5185]

The lag isn't anything I can't deal with. Car is still a kick in the rear once she spools. I think a little more should put it just where I want it.

[hebert.mike]

I realize I should definitely wait to get a tune until after I change injectors/fuel pump and turbo, but I'm wondering what are typical gains I'll see with it? I have all catless pipes and stock headers and turbo on my 03 WRX

[P3Auto]

Originally Posted by hebert.mike

I realize I should definitely wait to get a tune until after I change injectors/fuel pump and turbo, but I'm wondering what are typical gains I'll see with it? I have all catless pipes and stock headers and turbo on my 03 WRX

More info needed. What do you have now? What will you be adding? Over a stock tune the gains are quite large and you will feel a big difference even without a turbo upgrade.

[hebert.mike]

1.75" invidia uppipe, 2" bellmouth Invidia downpipe, 3" catback exhaust, and giant TMIC everything else is stock. I'm going to take my injecters out and remove the restrictor cap off which pushes the flow on those to 880cc? That's what I've heard anyway.

[Brando5185]

Originally Posted by hebert.mike

1.75" invidia uppipe, 3?" bellmouth Invidia downpipe, 3.15" catback exhaust, and giant TMIC everything else is stock. I'm going to take my injecters out and remove the restrictor cap off which pushes the flow on those to 880cc? That's what I've heard anyway.

Is your downpipe really only 2 inch? Seems strange.

[Marlons101]

thats gotta be a typo..cmon invidia does not make 2in bellmouth dwnpipes

[Brando5185]

lol was just making sure. I don't know invidias so I wanted to ask him first.

[KW900]

Would recommend sending yours in to Witch Hunter and getting a matched set if you are going that route.

Originally Posted by hebert.mike

1.75" invidia uppipe, 2" bellmouth Invidia downpipe, 3" catback exhaust, and giant TMIC everything else is stock. I'm going to take my injecters out and remove the restrictor cap off which pushes the flow on those to 880cc? That's what I've heard anyway.

[Brando5185]

If you order from Deashworks you can send your stock ones in for a core return. It isnt much for WRX injectors though. I think...

[hebert.mike]

Yeah, my bad on the 2", where is dashworks or witch hunter? I'm trying to save money where I can lol