MyE28.com

Well for those of you who have been following my TCD adventures here is an update.

Todd sent me an LM-1 to use so I could tune my car a little better than what I been tuning it.

Last week on the dyno I was initially running super fat. So fat in fact that my car should not have been running at all according to Todd. I'm talking AFR around 8.8:1. So I adjusted the AFM a few clicks (6 to be exact) clockwise. Still really fat but better. Around 9.7-10.3:1. So we disconnected the FMU. Better but still not good. Still in the low 10's. Idle was around 14.4- 15.0. Perfect.

The guy at the dyno suggested we lean it out some more at idle due to the fact that we were getting the reading after the cat. Once we got it lean we could not get it rich again. We were seeing 14.7-15.0: 1 AFR's even with the FMU reconnected and adjusted for extra fuel, and the AFM adjusted back down to our starting point where we were super rich before.

I called it off and determined that they must have had a problem with their wideband.

Today while using the LM-1 I am having the same results.AFR's staying 14.5-15.0:1 at any rpm or throttle position. (including WO under boost above 4000 rpm) I have the 255 lph fuel pump. I took it out of the tank to make sure I hadn't screwed it up somehow. It's fine.

I even disconnected the O2 and set the AFR to 14.7. No discernable difference.

So now I am going to make certain the FMU hose is not just plugged and not raising the fuel pressure. I think I'll take that restrictor out that it says to put in there next and see if there's a difference.

Todd sent me a boost gauge to use to see what boost I am making but I am missing one of the fittings to make it work and they don't sell anything that small at the local "home mega super don't really have what you need" stores. So I am still in the dark about that.

Just thought I'd put it out there for the more experienced folks who may see the problem more easily than I do.

OK, sounds like you're starting where I did.

There's something about the FMU that you need to realize and may not know. There's two adjustments on it. The small knob on the side adjusts the rise under boost. The screw on the top adjusts rise at atmospheric (0 psi). If you just disconnected the signal line to the FMU, it's seeing atomospheric and raising the fuel pressure slightly, sort of like disconnecting the signal line to the FPR, only more so. In order to get the FMU out of the loop, you need to disconnect the signal line and re-route the fuel so that's it completely out of the picture.

I don't think you need to, however.

In my case, I had to dial the FMU to its lowest possible setting on both counts (top and side), and tighten the AFM a bit before I got out of the realm of the atrociously fat (8-9:1 under boost). I'm currently at 11.5:1 or so, my AFM needs to go tighter still, that'll happen in the next couple weeks. I also went from 8psi to a solid 10psi when I got the mixture closer to correct.

Hope this helps. You're in for a hell of a ride once you get it straight if you were impressed before. 8)

Jeremy

Mine is set up the exact same way. All the way out on the bleeder valve and no gain at atmospheric. And it feels mad rich under boost. Especially up high. I might try an M30 AFM. The M20 AFM seems to open too much regardless of spring tension and the big hole I've drilled in the flapper door. Still, better too much gas than not enough.

Have you done a free air calibration of your LM1? Let the unit reset itself back to baseline.

RDAvena wrote:Have you done a free air calibration of your LM1? Let the unit reset itself back to baseline.

Yes, I did that prior to installing the sensor today. I am just getting the feeling that I am not getting any enrichment from the FMU.

Jeremy, those are fine suggestions. I will be playing with it all evening most likely so I'll try to keep ya'll posted.

O.K. without the restrictor I am seeing 10:1 AFR's. I am going to put the restrictor back in and see where that puts me. I can then determine whether to adjust the bleed off screw or the main pressure adjustment screw.

I'll again keep you posted.

I had AFRs all over the map. One day they were fat, the next lean and it drove me crazy. I burned up lots of phone time with Todd and others trying to solve the mystery and never really came up with anything solid as to why it was acting psycho. This went on for the better part of a season.

I can't remember why, but I dug into the harness and wouldn't you know that was the crux of the problem. Old age and having done the in/out thing a few times must have taken their toll. 2 of the AFM wires were in tough shape as well as 3 injector plug pigtails. Fixed the AFM wires and replaced the pigtails and life has been good.

GregATL wrote:O.K. without the restrictor I am seeing 10:1 AFR's. I am going to put the restrictor back in and see where that puts me. I can then determine whether to adjust the bleed off screw or the main pressure adjustment screw.

I'll again keep you posted.

I couldn't even get close without the restrictor, you'll need it if you have the same FMU setup I do. We're running the same setup exactly at the moment I think (30lbs injectors for you?), so the tuning solutions should be similar.

Jeremy

Yeah, you may want to check the continuity of those AFM harness splices we made. Wiggle them too...

Maybe we fudged one up...

O.K. after extensive testing here's what I know. It is swamped by what I don't know but it is still all I know.

I am certain of a couple of things. The AFM seems to be adjusted properly. The FMU does not appear to be working correctly.

If I am not mistaken the FMU should increase fuel pressure as boost pressure rises. Instead, the FMU does nothing until the engine is @ WOT around 4250 rpm then it goes full rich.

AFR's would stay between 14.3 and 15.0:1 all the way beyond 4000 rpm and then Wham, suddenly they are 10.1:1. We saw high 9's as well. the 11's 12's and 13's were essentially skipped in their entirety.

This is exactly what we saw on the dyno a week ago. When we were shutting down due to high AFR's we never went above 4000 rpm for fear of detonation. If we had kept going we would have most likely seen them drop suddenly. I am willing to bet on it.

It does this with or without the the restrictor in the boost line. It also makes no difference where the bleed screw on the FMU is at. ( I should state I only turned it in 2 full turns at it's most closed point). I have adjusted the FMU to open easier trying to bring the point of enrichment down in the rpm range. All it did was go richer when it opened, which happened to be at the same RPM as before.

I guess what it boils down to is this;

what would cause the FMU to act like a switch instead of having some linearity? A bad diaphragm? A really out of whack adjustment from the factory?

Which brings me to another question. What is the baseline setting for the FMU? I am referring to the onset screw, not the needle valve. And how do you set it back to that setting. I don't just mean "how do you turn a screw". I am referring to the factory adjustment of the screw. Can I do it by disconnecting the sensing hose and then setting the backpressure to a certain pressure? Yes I have a gauge there already.

While scrutinizing things I noticed that the jam nut on the "on set" screw was not even tight. Could it have just been really badly out of whack? I feel like I am going in circles here.

And just to help confirm my results NaNa535 was there watching the AFR's while I was driving. He would call them out frequently as the car was accelerating so I could determine at what point the FMU was kicking in. It was always between 4100-4400 rpm.

So experts, enlighten me please.

Pop the cover off the AFM. If the tracks go all the way across the "readable area", you need to tighten it down. If the AFM pegs, the Motronic defaults to some default duty cycle and goes very very rich. Don't worry too much about getting it close to stoich with the Motronic O2 unplugged. As long as it's still bringing it back to stoich with it plugged in, you're ok.

Also, the needle valve on the FMU should be turned counter-clockwise, all the way out, if you're having issues with it going rich as the boost goes up. The top screw only adjusts fuel pressure at atmospheric, so if the mixture is good as it comes on boost (again, you need the boost gauge to know for sure), that setting is fine.

The FMU cannot be tuned to come on at point in the rev range, it's all based on boost pressure. Have you hooked up the boost gauge yet? Knowing what the boost is doing will help here.

You need a working boost gauge.

This may help as well if you haven't seen it:

http://www.cartech.net/fmu2020instruc.htm

Jeremy

I hear what you're saying about the boost gauge. I am lacking a compression fitting for a 1/8" hose. Could not find one locally today. Will try again tomorrow.

Jeremy, I am certain that I am seeing boost well before 3500 rpm. You can feel it coming on and the car certainly pulls harder down there than before. Even without a gauge to verify it there is boost there.

My confusion stems from the "light switch" like way that the AFR's go rich. They go from stoich to 10:1. Do not pass 13:1, do not stop at 12:1, go directly to 10:1. I am not seeing the "rising rate"(rr) in rrfpr. It is realistically on/off.

Concerning the AFM, I set it tight until the computer could no longer compensate and bring it back to stoich. Then I loosened it 2 clicks. This was with the O2 sensor connected. It brings it to stoich now at idle. 1 click tighter and it has a very hard time staying at stoich. 2 clicks tighter and it can't.

I do appreciate your help Jeremy. I am a little frustrated and it is probably coming across in my post.

Greg, Go through this methodically... make sure the center "boost onset" screw in the center of the cap is backed out fully, needle valve is backed out fully and has the check valve installed in its vent tube, restrictor is in place in the signal line and the fuel lines are not reversed at the FMU.
You should also be able to blow into the signal line and feel air exiting the needle valve vent. You should not be able to blow air into the needle valve vent.

Yeah I have blown through the lines. Everything checked out as it should. I am 100% certain the fuel lines are installed correctly.

I will back the onset screw out completely and see if that helps or changes anything.

Question, is there a positive stop when backing out the onset screw? I know not to turn it in too far just like any pressure regulator. On many of the pressure regulators I've used in the past (hydraulic and air) the screw will back all the way out of the unit.

The paperwork for the FMU says to set the atmospheric pressure of the unit to 40-55 psi. I am gathering that with the onset screw backed out all the way this is not a criteria I should be concerned with.

Yes, the screw will come out but you need to keep it installed and the lock nut in place to seal the chamber. The FMU is similar in design to a waste gate but with the signal pressure pushing on the opposite side of the diaphragm.
Don't be afraid to take it apart if you want to look inside. There's a central port from which fuel from the stock FPR enters. The fuel flows past the sealing plate and out to a channel connected to the outlet port. If the fuel lines are reversed the pressure in the system can force the seal open due to the greater surface area that the outlet channel provides until boost pressure is great enough to allow the FMU to clamp down. This could account for little fuel pressure rise initially and then a sudden jump.
You can plumb an inexpensive fuel pressure gauge into the system with enough hose to fix the gauge under a windshield wiper (to keep it outside the cockpit) to monitor what the pressure is doing.
For the boost gauge, you can attach a hose barb to most and run a standard vacuum line instead of the compression fitting.

FWIW, I think the compression fitting is the same as some used in cheap-o oil pressure gauges with nylon tubing....

Sweeney wrote: For the boost gauge, you can attach a hose barb to most and run a standard vacuum line instead of the compression fitting.

Damn, I have been looking at the trees again. So simple. My bad.

Unless the FMU has "IN" stamped on the outlet side it is connected properly.

I have a pressure gauge connected to a tee on the inlet side of the FMU. Is there a pressure in this location that I should set the FMU to with the signal line disconnected?

BEGIs' paperwork states that it should be between 40-55 psi here under those conditions. What do our cars prefer?

Alot of questions I know.

O.K. starting fresh today.

I installed the boost gauge. Connected it to where the vacuum line for the interior temp control goes and zip tied it in place.

Zip tied boost gauge to windshild wiper. At idle I have a very steady 14" of vacuum. Haven't had the chance to drive it yet but will soon as I have an errand to run.

Also in regards to adjusting the FMU. Since Sweeney suggested it back the onset screw off completely I did that. Then I disconnected the signal line and started the car. Completely backed off it read 9 psi at the gauge. I tightened the onset screw (several turns) until the pressure just crept up from 9 to almost 10 psi at the gauge. That is about as backed off as I can fathom it needs to be.

So here is where it stands currently;

AFM is adjusted correctly. If my adjustment method mentioned earlier is wrong please let me know what the correct procedure is.

LM-1 is calibrated and installed.

Boost gauge is installed and working with vacuum. I believe it will show boost when I get to drive the car.

FMU is backed off to the point where it is just capable of changing the static fuel pressure with the signal line disconnected. Static pressure in front of FMU is 9 psi. Adjustment is < 10 psi. Restrictor is installed in signal line and bleed off valve is fully open. (counterclockwise)

Aside from a fuel pressure gauge sticking out tthe hood what else should I be using to monitoring data?

Thanks for all the help so far.

GregATL wrote:Also in regards to adjusting the FMU. Since Sweeney suggested it back the onset screw off completely I did that. Then I disconnected the signal line and started the car. Completely backed off it read 9 psi at the gauge. I tightened the onset screw (several turns) until the pressure just crept up from 9 to almost 10 psi at the gauge. That is about as backed off as I can fathom it needs to be.

Which gauge? I'm hoping this is some form of typo, it doens't make much sense to me. Where is you fuel pressure gauge connected to the system?

My "top screw" is backed out until it has no chance of touching the diaphragm inside. Yes, the needle valve on the side has a positive stop, it will not completely unscrew and fall out on you.

Jeremy

Greg, the fuel pressure gauge should be in the fuel line entering the fuel rail so you know what pressure the injectors are receiving.
With the signal line removed the FMU will increase pressure as there is no vacuum in the chamber acting on the diaphragm.
Does your FMU have the 1/8 inch or 1/4 inch NPT fittings?

Sweeney wrote:Greg, the fuel pressure gauge should be in the fuel line entering the fuel rail so you know what pressure the injectors are receiving.
With the signal line removed the FMU will increase pressure as there is no vacuum in the chamber acting on the diaphragm.
Does your FMU have the 1/8 inch or 1/4 inch NPT fittings?

I know the fuel pressure gauge needs to be in front of the fuel rail for absolute readings. "I" put one right in front of the FMU so I could use it to adjust the "atmospheric" pressure reading of the FMU without interference from the stock fuel pressure regulator. This way I have an accurate way to know exactly where the FMU is adjusted to. It was certainly necessary when determining where having the onset screw backed out fully was.

My FMU has the 1/8" fuel connections.

Before we proceed any further. Please don't get insulted but do ya'll take me for a complete idiot. I very much am appreciating the help but we're just going in circles here.

Perhaps the way I write isn't the way ya'll think but Jeremy, come on, isn't it just plain obvious that the bleed off screw doesn't back out all the way. It very defintely has a positive stop. The onset screw, as I discovered will back completely out. That is why it took several turns to bring the screw back into contact with the disc in the regulator. As soon as it touched the disc the pressure went up. I allowed it to go up less than 1 psi from the static setting. So it is barely in contact.

I said before;

FMU is backed off to the point where it is just capable of changing the static fuel pressure with the signal line disconnected. Static pressure in front of FMU is ~ 9 psi. Adjustment is < 10 psi. These readings are with the signal line disconnected.

Restrictor is installed in signal line and bleed off valve is fully open. (counterclockwise)

Now that I am certain the FMU is backed off fully I can move my fuel gauge to the inlet side of the fuel rail.

O.K. I hope no one is offended now. Back to the topic at hand.

Based on the adjustments I defined in my last post here is what I was able to discern on my test drive.

I start building boost @ 2000 rpm on the gauge.

By 2500 rpm I have 5 lbs of boost.

By 3000 rpm I am making 7 lbs. It stays @ 7 lbs till over 6000 rpm.

AFR's stay at stoich (14.3-15.1) untill over 4000 rpm. Now however instead of dropping to low 10's immediately they drop to low 11's high 10's and then make their way down to low 10's high 9's by 5500 rpm.

The boost gauge and the FMU recieve their signal from the same place also just in case anyone is wondering.

I did 8 pulls to establish some consistency with the numbers.

Thanks again for the help.

The recommended atmospheric fuel pressure IS with the stock FPR inline, all signal lines in place and with the engine running.

I'm so damn offended.... wait a minute, no, I'm just hungry.

I called BEGI and spoke with the man himself. That was a bit of a surprise.

His instructions were to set the atmospheric pressure rise of the FMU about 10 psi higher than the stock FPR. Install the restrictor (which I have done). Open the bypass valve all the way, and then, if things were still amiss, to remove the check valve to see if it is a restriction on the bypass circuit.

If none of those work then he suggested it was most likely the valve disc inside the FMU was damaged. I have not opened it up yet.

He said that if it still didn't work he would send me a new valve disc to try.

So I am planning on moving the pressure gauge, setting the FMU's atmospheric pressure to 54 psi and then testing out the AFR's again.

What kind of restrictor are you guys using? I got my BEGi 2025 used, and it didn't come with one.

turbodan wrote:What kind of restrictor are you guys using? I got my BEGi 2025 used, and it didn't come with one.

It is a tiny little plastic insert that goes in the signal line. You can get one from BEGI. I know they're cheap too.

Where can I go to BEGI and order one?

On another note, I would set the fuel pressure at atmostpheric at around 50psi. 54 seems a little high.

EDIT last post:

Just bought one from bell engineering. $3.00 a piece. Not too shabby

I just stuck a vacuum mender in my signal line to test on my way to mickey d's. It does make a difference. The inner diameter of the mender was about 1mm. I don't know what the BEGi restrictor is like, but this peice of plastic seems to have worked pretty well. A noticeable kick in thee pants.

I don't take you for an idiot. Ask Todd and Sweeney about the stupid questions I've asked them from time to time. Actually, don't, hopefully they've forgotten most of them.

I couldn't understand how you were seeing 9-10psi on the fuel pressure gauge, thank you for explaining that. Makes sense to me now.

As for the comment on the needle valve, I just wanted to make sure all bases were covered. Don't take it as calling you an idiot, take it as not making any assumptions about your knowledge. As I alluded to above, I've missed or misunderstood some basic stuff with regards to this whole turbo experience from time to time, so I just wanted to make sure there weren't any holes in your own knowledge.

That said, I'm officially out of ideas and wild assed guesses, but I wish you luck and hope you get it sorted soon.

Jeremy

Yeah, for a temporary solution, I fabricated a tiny rod with a 1/16" hole drilled in it. That turns out to be a 1.5mm diameter.

I don't know what the BEGI restrictor is either, but if it's smaller than that, I should be getting alot more power once the real restrictor comes in because I'm running a little bit rich on initial boost (up to 70psi fuel pressure)