Forgot your password?
F14CRAZY, February 19, 2006 in Buick Reatta
"The only racing that ever mattered, is on the streets"
I agree with Ryan 100% that you shouldn't use the LN3 MAF sensor, the construction is completely different, as can be seen, although my testing indicates the calibration is essentially identical to the LN3. The location of the O-ring being different will cause a vacuum leak as well as the sensor wires not being inside a symetrical opening. What are the two rows of numbers on the L67 MAF sensor? I don't suspect the MAF at this time, it appears to be the correct type, unless it is bad. I think you are working with a 1990 engine and ECM and this one will go into closed loop operation at 130* F, observed many times. Your fuel pressure reading still seems funky? Unless that regulator is damped somehow, the pressure should snap up and down when you blip the throttle. It will slowly change with a slow change in throttle, but I would think the pressure should actually do down at a constant engine speed of say 2000 rpm vs idle, since the engine vacuum at essentially no load should be higher. The only caveat is the s/c itself and the comment that it picks up the vacuum signal from below the blower. I think I remember you said the boost bypass is blocked in the closed position. Maybe there is a slight boost pressure, or a reduction in vacuum from the blower spinning? Tee a vacuum gauge into that line to see what it is seeing? Actually, just disconnect the vacuum from the regulator and plug the line. The fuel pressure should now be at a fixed value of around 3 bar, 43.5 psi, if the regulator is calibrated the same as the LN3, and it should not vary with engine rpm or whatever you do with the throttle. If it changes, something odd is going on. If it drops when you mash the throttle, fuel delivery is inadequate, for whatever reason. The higher fuel pressure should gradually move the BLM lower since the pressure and fuel delivery will be higher than normal. The O2 must be connected and up to temperature for this adjustment process to work and it will take a little while.
The TV (throttle valve) cable controls the shift point on these transaxles. The modulator controls line pressure and shift firmness. They are apparently a little different than most mechanical transmissions in that the two functions are pretty much divorced from each other. On most systems the two items interact more with each other. With the cable disconnected I would expect the trans. to upshift earlier than normal. In theory it shouldn't do any harm, at least short term, but the s/c engine produces a lot more torque and early shift points will tend to place more strain on the system, and load the engine more than normal. Best bet would be to get it connected and adjusted properly. For your testing in park/neutral, it won't matter.
For the record, I run Autolite 103 plugs gapped @ .048" with the stock Magnavox ignition. This is a cold plug, two ranges below stock. A 104 would be better choice, one range colder than stock as a good starting point. Just my opinion, but platinum plugs don't perform well in a boosted engine, especially Bosch, but there are a lot of different opinions on this.
I swore that someone suggested swapping the MAFs. But at any rate, I'll get the part number later and switch back.
As I said, the pressure does briefly blip up when I blip the throttle, but drops down almost immiditely (spelling?) for the engine bogs out.
I'll get a pressure reading with the regulator vacuum disconnected.
I do have platnium plugs. Should I swap them out?
<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">I got a reply from Ryan...
<span style="font-weight: bold">Philip, if your fuel pressure is dropping off with higher RPM's or more boost present, the fuel system is not adequate for the job. Can I assume you are using the stock L67 fuel rail and pressure regulator along with the injectors?</span></div></div>
He programmed your chip without knowing what injectors you're using? That could be a problem!
<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body"><span style="font-weight: bold">
Don't set the plug gap at 0.025". That is far too small. A plug gap setting of 0.050" is what I would use.</span></div></div>
I hear this *all* the time! It's amazing what people assume without testing. If you're getting a misfire, this will often clear it up on a DIS system. I never set supercharged engines larger than .045", usually .025-.035".
He knew of the injectors I was going to use. I said so in the form I filled out for the memcal program. He's just checking to be sure I'm still using them and didn't go ahead and use the LN3 injectors.
I am using a Delco coil pack
If it is ok with Philip, I think too it would be a good idea to continue the discussion here so the bulk of the Reatta community can use it as a reference...
Yes, I knew what injectors philip was using when I did the chip but the reason why I asked again was because he was talking about swapping parts back on from the LN3. I just wanted to make sure.
I would like to take a moment and explain what I have done with Philip's programming. I have tried a unique idea in which I have attempted to marry as much of the L67 programming as I could with the LN3 computer system. I am confident we can get the LN3 computer to work with the supercharger, although I am sure it is going to take some trail and error until we get it working right. For this application, I suggest that Philip use the L67 throttle body and MAF sensor since that is what the chip I did for him is programmed for.
As far as INT (Integrator) and BLM (Block Learn) counts are concerned, here is how that factors into the fuel equation...
Integrator is short term fuel trim. The median value is 128. The computer will adjust this value rapidly in order to satisfy stoich fuel ratio (14.7:1). Any number higher than 128 tells us that the computer is having to add fuel to the base fuel map in the programming in order to get the A/F ratio rich enough to meet the 14.7:1 stoich value. Any number lower than 128 tells us the computer is having to remove fuel from the base fuel map in order to lean out the A/F ratio to meet the 14.7:1 stoich value. These same numbers apply to the BLM counts.
The BLM is long-term or stored fuel trim. Most GM cars have a 16 BLM cells, or memory points where the learned fuel trims can be stored. The cells are divided up by RPM and LV8 (load). BLM learning is not always enabled. Even if the system is in Closed Loop, there are still additional parameters/requirements that must be met in order for BLM cell learning to take place. These parameters are different from vehicle to vehicle.
In any case, if your INT counts are hovering around say the 160's, you should notice the BLM counts slowly moving towards that level. As they do, the INT's should come back down. Once the INT comes back down to 128, the BLM's will stablize and the ECM may decide to store that new BLM value to the approprite memory cell for future use (lookup).
Also in these computers there is a function known as PE (power enrichment). On stock LN3 programming, the ECM is instructed to enter "PE mode" around 50-60% throttle, depending on the RPM level. On stock L67 programming, PE mode is entered at about 40-50% since boost can build on these engines with relatively low throttle openings. Nevertheless, when PE mode is active, the INT and BLM counts will freeze, no BLM cell learning will be enabled, and the O2 sensor signal will be ignored (the computer will not attempt to make any adjustments to the fuel trims during PE). That is why we need to know what the O2 voltage or exhaust A/F ratio is doing when in PE mode. A wide-band O2 sensor is far more accurate in this area, but the factory narrow-band O2 sensor does give us a ballpark idea of what the fuel mixture is. However, if misfires are occuring, this will allow raw oxygen to enter the exhaust system which will throw O2 sensor readings off.
There are a couple of things Philip and I need to figure out with his car. We have already determined the fuel pressure isn't rising to spec of the L67 engine. Once he gets the fuel pump replaced (I would advise changing the fuel filter at the same time if it hasn't recently been done), we can proceed with further diagnosis. There is nothing more difficult than trying to "tune-around" a mechanical or electrical issue that exists; especially on a project like this.
Thank you Ryan.
I just came in for dinner, but I'm working on the fuel pump right now. I've got the tank down and harness disconnected. The tank straps and fuel lines look to be in good condition.
The tank was over half full, so I connected a longer hose under the hood where the fuel lines connect to the rail and applied power to the oh-so-mysterious green connector under the hood by Teves. I pumped the tank dry (pump wont be used again anyway). A lot easier this way than having to work with a heavy, dangerous tank.
When I get it running pretty darn close to decent, I could probably take a day and come down and see you, Ryan, so you can do the finer tuning.
Hey, I got the new fuel pump put in! Took a few hours but wasn't that bad. As Ryan suggested, I used one prescribed for an '89 Turbo 3.8L Firebird.
I did some fuel rail testing. At warm idle, I'm reading 38 PSI. I disconnected the vacuum line for the fuel pressure regulator, and the pressure stayed the same. When the throttle is blipped from idle (and it bogs) I very briefly read about 50 psi. I recorded the same thing happening, both with the vacuum line connected and disconnected. At WOT, I read 42 PSI. At this point, I can slowly get up to 4600+ rpm, just have to get there slowly.
New warm idle ECM readings today with the new pump...
ED01, TPS: .48
coolant temp: about 180 F
ED06, injector pulse width: 4.4-4.6
ED07, osygen sensor voltage: 0.10-0.73 (quickly, randomly changing)
ED08, spark advance: 18 degrees
ED16, ESC knock retard: 0 degrees
ED17, OLDPA3 knock sensor activity: 109
ED18, oxygen sensor cross counts: 2-12
ED19, fuel integrator: 121-127
ED20, BLM: 123-124
ED21, air flow: 6.7-6.9
ED23, MAT: 16 degrees C
ED98, ignition cycle counter: 0
From what I know and the looks of it, the integrator and BLM are about normal, right? In a few minutes I'll have the ECm readings when bogging out
I got these readings, with the motor bogging out, by generously stepping on the throttle (maybe halfway?) quickly and recording the readings. I did it once for every sensor reading. I'd let the throttle get up to about 1500 rpm with it bogging (it very slowly comes up, but still runs bad).
ED07, oxygen sensor: still all over the place
ED17, OLDPA3 knock sensor activity: 186
ED18, oxygen sensor cross counts: 3-6
ED20, BLM: 130-133
You guys want any different readings?
I haven't driven the car yet. In fact, the rear wheels are still off (had to kinda remove the sway bar to get the tank in/out). I still have to work on that tranny cable before taking it for a spin.
Ryan: at this point, do you suppose at this point I could make a day trip with the car to you so you can really see what's going on and tune it? Are you more or less readily available? It's running good enough to drive at the speed limit and from the ECM data, isn't running acutely bad. The internet is cool, but as you know and we know, it's hard to tune a car a few hundred miles away.
so the new fuel pump didn't help?
It did not help. It doesn't run any better.
However, do note, that fuel pressure is now right where it should be. It's 38 PSI at idle, which Ryan said it ideal. I used to be around 30.
Is the fuel regulator faulty?
It is time to check the basics again.
17 degrees advance sounds quite low but may be remapped for premium fuel (mine runs about 23 degrees at idle and hits 40 degrees on a blip, I would expect you to see at least 35 degrees advance by 2000 rpm with light load since no boost is involved.
You do not seem to be getting knock retard (OLDPA3 often increments on startup but should not be changing at idle).
Again, if you rub your finger inside the tailpipe, does is come away black ?
Remote possibility: clogged catalytic converter, will act like a potato in the exhaust pipe. Might try a brief run-up with the headpipe disconnected since you have it in the air and see if it still bogs.
Just for S&G if you still have your original PROM, might try that. Without load in the garage you should not get into any boost anyway and would be a good test.
I have a '90 Lesabre memcal which runs a Reatta LN3 perfectly fine, so I'll try that.
The less knock retard the better, right?
No abnormal amount of carbon/blackness in the tailpipe
The cat was replaced last year. But would a clogged cat still let the motor run at steady high RPMs or WOT fine?
Should the fuel pressure go up with RPM? Ryan said that 38 PSI should be idle, and then rise about 1 PSI for about every pound of boost. At WOT, I'm still reading about 40. Could the regulator be bad?
Could the MAF be bad? The one I'm using is not known to be good, though the yard said the motor ran fine in the Bonneville it came out of 33 days before I bought it
First of all, Philip can no longer run a stock Reatta or any other stock LN3 mem-cal (chip) in his car because he is using the larger L67 injectors. If he tries using a LN3 chip, he will flood out his engine.
It sounds like your fuel pressure readings have improved with the new pump, however, I am troubled by the fact the fuel pressure isn't changing when you unplug the fuel pressure regulator. With the engine running at idle, with the vacuum line plugged in, your fuel pressure should be 35-38psi; as you indicated you had. However, that pressure should have jumped to approx 42-45psi when you unplugged the regulator. Was there vacuum present at this vacuum line at idle? If not, there must be a vacuum leak somewhere. As far as fuel pressure under boost is concerned, again; I don't have specific specs but I am pretty sure it should be above 50psi at about 10psi of boost.
Philip, you INT and BLM counts look MUCH BETTER than they were. However, since the bogging problem hasn't changed whatsoever (even though the INT and BLM counts have improved) tells me we MIGHT be dealing with a mechanical issue here. Checking for a clogged catalytic converter is a VERY GOOD idea as well. As the guy said earlier, unbolt your exhaust system from the manifold and see if the bog still exists. But I am not ready to rule out a computer tuning issue just yet. The O2's shouldn't move around under "WOT" but since you are getting a bog, or misfire, this is probably the cause of the irratic readings.
As far as bringing the car to me, that shouldn't be a problem. Contact me via email and we will discuss time and date.
There for sure was vacuum when I unplugged the regulator. I felt and heard it. I'll check around for leaks again, but I can say that there's at least something there.
I'll get an oxygen sensor reading at WOT.
I bought plugs and wires which I'm going to do for good luck. I'll recheck the TPS. I bought the AC Delco equivelent of the 104s that 2seater mentioned.
I wonder since you are using the LN3 heads and with the rear exhaust manifold issue the motor is choking on its own exhaust?...
Without a load the peak fuel flow and LN3 exhaust pipes are not going to make a difference. What I hear is that the engine bogs just on free revving.
Really wonder if there is an advance curve issue.
Today I picked up some new LN3 plug wires and AC Delco R42LTS plugs, the equivelent of the Autolite 104s (Advance didn't have enough).
I pulled my current Autolites out, and I don't know how, but I they were gapped at 0.060 up to 0.065, pretty far off from the 0.048 that 2seater suggests and that I used.
Got them in and fired it up. No noticible change. Blast, I thought I was on to something. I did recheck that the plug wires were connected right.
At operating temperature I ran it up to WOT and held it for a few seconds to get the oxygen sensor reading (it's around 0.67). Not sure what RPMs were but it was above 4k rpm. I got out to check the engine (returned to idle) and found that the exhaust headers were glowing brightly . I shut the system down. I don't think that's a very good thing.
Where to now?
Is that a sign of a clogged cat? Haven't got to trying it with it disconnected yet
I think with the SCer the exhaust manifold restriction is backing up the exhaust with the added cat restriction even with an operational cat it is still a restriction. I think it is a restricted exhaust.
1) LN3 rear exhaust manifold restriction
2) cat+LN3 rear exhaust manifold restriction
at least cut the cat off
<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body"> the exhaust headers were glowing brightly </div></div>
Would that be a sign of greatly retarded timing?
"the exhaust headers were glowing brightly" - usually means waaay lean though suppose a really retarded spark could result in fulel burning in the exhause pipe. What does the inside of the tail pipe look like - whill be almost white if way lean, grey if normal and black if too rich.
You need to be a member in order to leave a comment
Sign up for a new account in our community. It's easy!
Already have an account? Sign in here.