In the interim anyway (until I do the LT1 PCM swap)...

$EE LT4 timing map with $DA3 AE vs Delta TPS and AE vs Delta MAP. I also tuned my VE's to get 126-130 everywhere. It also runs better now with only a 30 lb on #2 instead of #1 and #2. I tried the other $DA3 AE tables as well, but these two in conjunction with the remaining factory AUJP AE tables works the best under all conditions.

Except for an ever-so-slightly rough idle and smell (in gear), the car now runs perfectly. In park, it idles perfectly with about 16 inHg vacuum (13-14 in gear). Throttle response is absolutely beautiful and the acceleration is like nothing it's ever been before.

I've found that if I deviate at all from this configuration, I can actually feel the decrease in driveability/performance. So I guess I'm going to stop here with the tuning.

I get no knock counts, so given the performance and the no-knock, it seems like I have the optimum timing curve for this engine.

This will tide me over until I'm able to do the PCM swap.

 

Good to hear you have found a somewhat....happy medium. Let's just hope the PCM conversion goes as well also.

 

Whatever floats your boat. Mix n match injectors should never be "right".

 

It's a band-aid for now. Like I said, I want to get to the dual O2, SEFI, LT1 PCM so I can tune this thing the way GM did.

If there was some mechanical and/or electrical malfunction causing the idle problem, there's no way it would run this good everywhere else. This thing smoothly spins up to 6000+ rpm without even a flutter; and I can stab the throttle at any speed and not get any pops through the intake or even as much as a hesitation.

 

Sure sounds like a good tune, but I'd be concerned as well about having to run different rate injectors to get there. Maybe that's my problem as well, I'm running all SVO 30#'s....

I've got an LT1 PCM as well that I've wondered about using. Can't decide whether I want to do it with the SuperRam or the brand-new-installed-but-never-run LT1 intake I have sitting in the garage (or the other complete LT1 I have either). One of these days I'm going to have to research what all has to be done harness wise to see if I really want to go that route...... (I also understand there can be some issues with the Sportsman II heads I'm using)

 

Already did that. You have mail.

 

I dont care if you have 8 different size injectors. You have it running the way your want at any given condition. Great job and Congratulations !

But an artist is never done with his work

 

wasn't there something in the LT1 bin that had the VE or something else turned up higher to richen up some of the cylinders?

glad to hear you finally have that miss fixed

 

Yup. GM richened the front two cylinders by 17-20% over the rear two. All I did was do a brute-force duplication of that by putting a 20% bigger injector on #2. Each cylinder received a slightly different fuel trim, which I want to be able to do once I get the LT1 PCM in.

 

And I really appreciate your doing that, too! THANKS!!!

 

One thing you might consider, is using a scope with a WB and looking at the individual cylinder AFRs, to see if you're actually matching AFRs from cylinder to cylinder, or if you're covering symptoms of something else.

 

Scope with a Wide Band to see individual AFRs? Not sure I understand.... could you elaborate a little...

As far as potentially masking something else? I guess I'm at a loss as to what could cause such a problem at idle, but allow the car to run perfectly everywhere else? Vacuum leaks, I know... but I gaurantee there are no vacuum leaks on this car.

 

If you hook a scope to the actual sensor's output, you can see the individual WB readings per cylinder, instead of just looking at the average. With an individual cylinder trim, then you can play with getting all the AFRs as equal as possible.

 

Is this back to the split BLM issue? You may want to look at the other tables also. I was getting a lean spike when I gave it some gas. I solved it by upping the pumpshot 5% on the DA3 table like SAUJP and then working on the AE Vs delta tps. I was especially concerned about the split BLM issue as I went to a converted intake. I modified my TB and drilled a air hole for the IAC to get most of the air going through the IAC port. The MiniRam does not have this provision because the TB opening is wide open. I also took my PVC and routed it to just below the crankcase breather so it is in front of the intake as opposed to sitting on one side. My passenger side bank is not lean anymore like before -ie no glowing headers. I also had a idle problem since then. Look at the O2 rich/lean constants at idle. I lowered them .1 and also get this set my min CL temp to almost stock.

 

What I was planning to do was use EGT's to tune. I was going to get one of those infrared non-contact thermometers to measure the EGT and tune accordingly to get uniformity.

 

I have my rich/lean constant set at .350 V. That seems to have worked the best. Though, I haven't really messed with it in a while. I might try upping it a little to see what happens now that I've done some other things to the tune. Thing is, if it smells rich now, it's probably going to smell even richer if I increase the constant.

 

Look at the EE table for AFR VS Temp Vs MAP. Note that these ratios are leaner than the SAUJP tables. I used the AFR calcuator to determine the desired AFR based on the 2 tables. You will have to play with the combination to get a leaner desired mix of the 2. This appeared to help quite a bit for me with the gas smell.

BTW. The split BLM issue is a well known issue that is more of a mechanical problem.

 

The only AFR tables I see in the $EE code are for open loop (at least in Tunercat). Is that the one you're talking about?

 

I don't have the table here but it should be labeled as described. I then used the AFR calculator to convert to the desired AFR based on the AFR vs. Coolant Temp and AFR vs. MAP in $8d which are the Open Loop tables I believe you are talking about. If you look at the bin I sent you a while and do a diff on it you should be able to see that.

 

That doesn't isolate timing from the equation.
WOuld be worth trying, but I'd do everything I could to have a second way of verifing what you do see.

I'm wondering if the issue isn't as much as some oddity with self EGR'ing with that manifold. With all the *turbulence* in a plenum, and the way they all seem to have an issue, it would seem, that the manifold is the culprit.

 

Before going to the LT1 intake I went to the LT1 boards to see what they were doing. The split BLM issue comes up quite a bit. The thirdgen site deals mainly with the TPI's and older OBDI bin definitions. No one says a thing about split BLM's. Why not? I believe it's because the definitions only have 1 O2 sensor so they don't have a way to tell without recording both sides of the exhaust at the same time. Split BLM's started popping up after GM went to an O2 sensor on each side. Most guys think that the split BLM issue is because of the runner length or the TB with twin blades. LT1's with split BLM's mainly appear to have the passenger side lean and the drivers side rich. It is common with aftermarket TB's and the LS1 boards have reported this. The fix is mechanical. The fix is to drill a IAC hole in the TB where the IAC air is fed to get most if not all of the idle air through this port. The minor adjustments are to adjust the blades to equal out the BLM's. The older TPI and aftermarket TB's do not even have a drilled IAC hole but the LT1 TB's do. With the MiniRam you don't have the IAC port that goes to each individual runner so the problem may be enhanced further still. I still think that you can fix most of your problem by trying the IAC hole in the TB and maybe a combination of adding a tube in the back that ends up in the middle of the intake to help equal out the airflow to each port. Anything that breathes air -PVC, ect. not a vacuum port should be moved to the TB or IAC port. The second portion to this is split BLM's can be adjusted by adjusting the TB blades but you need a O2 in each side to do this. Most guys report the IAC drilled out to get virtually 100% air through the port fixes the problem. I am sure that going to a LT1 pcm will prove me right or wrong.

 

69, that's interesting. I'm having to read and re-read what you've been saying, but I think I'm finally starting to understand.

So let's see, if the #1 and #2 cylinders are getting the majority of the idle air distribution, then if I were to plumb the incoming idle air flow into the sides of the manifold, that might help even out the air distribution.

 

I don't mean to harp on this subject but I think it is worth while to check out. You should be able to run the SAUJP WBO2 hac with a sensor on each side. You can try to match the voltages by adjusting the TB blades. Or you can do a tune and get the idle BLM's to 128 then switch the O2 sensor side and see what the BLM's look like. Most of the LT1 guys shoot for a IAC count of about 30-40 max at idle to achieve a balanced BLM some even go as low as 10 or so. I suggested a dual O2 setup as part of a SAUJP enhancement to Z69 and JP but it is not on the radar scope with what they want to do -at least for now. The split issue comes down to a leak or large cam, TB, etc. In theory with a 8d setup the side unbalance should be mainly at idle and then clear up as you open up the TB. If you are off througout the RPM range it should point to an exhaust leak or something like that. There is lots of info on z28.com. Just do a search for Split BLM's.

 

No problem making the code for a second NB in 8D.
Somebody needs to come up with the hardware to make it work first. A 7730 only has one amp for a NB AFAIK.

Got a pic of the hole your refering to drilling Eric?
Or a better description?

 

OK here is the info. I believe the newer PCM's are bank fired so the split is because each side is being controlled separately. The site that I believe started it all is this one:
http://para.noid.org/~lj/PCM%20Tutor...litBLMinfo.htm

I have a 52MM TB that looked identical to the pics in the above post. I did not do the pipe fix I actually used JB weld to seal up the sides along with a newer TB gasget to seal it up. The newer TPI units have the air holes in each of the ports like the LT1 intakes do. I have verified this by examining my 2 TPI units one from a newer Vette and one from a older Camaro. Since Mike has a MiniRam he may need to do something fancy like use a pipe that goes into the plenum say half the length or something like that which may force the IAC air to equal out to the ports. The MiniRam dumps directly into the plenum and has no port holes in the individual runners. LT1 TB's already have a hole drilled. I don't know if the newer TPI TB's had a hole but the older ones did not. Again I have verified this. The LT1 TB's have a IAC bleed hole and the older TPI's do not. Here are some pics of the mod:

http://www.hashmarks.com/techtips/throttle_body_mod.htm

I need to keep looking for a particular post but it goes something like this. You want to drill a hole so that the blades are fully closed so that the IAC port has all the idle air through it. Most guys start with a .125 hole and slowly go from there. The idea is to have the blades fully closed or very close and IAC counts to around 30-40. I just drilled a .156 hole in mine and I happened to get lucky. Note I have a 327 and I am idling at 725 with a flat tappet cam. Most of the guys with a 350 plus seem to be from .1875 to around .25 for their final count.

An interesting sidebar from this. I am using much more of my VE table from this mod than before with no other changes. Before I was down to about 25-30kpa min. Now my MAP values get down to 8-10kPa. My VE tables in the lower end needed a lot of tweaking as I was running real rich in the 20kPa tables -I never had any data until the mod. My idle MAP value also dropped about 5-8kPa from before. Before my passenger side 3and 5 header tubes were glowing now they don't at all. This started when I put my LT1 intake on. At that time I also switched O2 sides -from passenger to the driver side. The glowing header tubes got me going on the mod to fix the problem. I also have a airfoil blade and opened up the upper portion of the blade so that I have no crankcase breather restrictions which also keeps it from sucking oil and to make sure I have full crankcase breathing. The last mod was to relocate the PVC breather to the TB port right below the Crankcase breather although it probably would be better to use the port in the intake below the TB which again is the IAC port but I am pressed for space there.

 

You know, the more I think about this, the more I'm getting anxious to try it. I'm going to take my TB off and see what options I have. I may just experiment with different ideas and see what works (if any).

Man, it would be AWESOME if this solves the problem and I end up not having to do the LT1 PCM conversion. It would be cool nonetheless, but what a PITA to have to do all of that to combat a stupid idle problem like this.

 

I've always wondered if you could put restricters in each runners IAC port.......

 

Mike a little more info and history here that may help you since you are running an older car -maybe you will see something. When I first went to a TPI I was not running a VSS. I had idle stall problems especially when coming to a stop. I then did the IAC blade adjustment where I set the blades to idle at 700RPM in gear. If the car stalled I just opened the blades some more and readjusted the TPS sensor back to .6 until I stopped stalling. This solved stalling problem I had until I put a VSS in and also started my own tuning. I put a VSS in and started burning chips. I did not have any problems but I kept the blade adjustment technique. Fast forward to my LT1 setup which is when I also put on my AFR's and 1.6RR's on the same cam along with the LT1 intake. At first I got an occasional stall when I put it in gear when the car was cold and the glowing headers. That is when I did the TB mod because of the headers glowing. I actually ended up with a much worse stall problem that was mainly when the car was cold. The first observation from the mod was that the VE tables dropped from the 60's to 50's at the idle areas and the MAP as stated before dropped about 5-8kPa. As I started my WBO2 tuning I ran into more stalling but only when the car was cold. I starting adding cold temp RPM's. Next I set O2 R/L constants at idle down .1 again this helped and I never touched these before. Next I adjusted my Open loop commanded tables to mimick more of the EE tables which is actually much leaner than a TPI setup. The next step was to up the closed loop temp from 20 degrees C that SAUJP has to 45 so the car runs open loop until it is warm. After setting my R/L O2 constants my VE table went back up to the 60's like before. In short the entire combination solved my problem. Hope this helps.

 

Scott the intake runners have very small holes about .03 in my estimation. My guess is that the IAC bleed hole was sized by GM so that a TB could be used on all cars. As far as I know it was added when GM came out with the LT1 which would make them size it to a 4.3liter V8 that would idle at about 600RPM. The stock TB bleed hole in the LT1's was about .08 as measured on the one I have.

I think a second O2 sensor that you can just do a datalog in mV to compare both sides of the motor to see if you have a exhaust leak or something would be sufficient. A bit to easily switch sides would also be cool but not necessary.

 

Well, I took the throttle body off the other day... It's an SLP version of a stock throttle body- basically they took an OEM and bored it out to 52 mm.


The MiniRam and throttlebody are not set up to do a modification like you're describing. I'd have to really sit down and think about how to accomplish it.

 

Mike since the MiniRam does not have any IAC ports in the intake runners you are in a situation of just trying to balance the cylinders more like a LS1 setup anyway. If you look at the pics on www.lt1intake.com you can see what I am talking about. What I would try and it should be quick and easy is to get a pipe and press it in. Make the length go to the middle of the intake so that the IAC air is coming right from the middle of the intake. Like the pic before in the link before the pipe is cut. Then try a .125 dia hole in the TB adjust your blades and TPS. They should be cracked a bit for that size. I had the same situation and did not use a pipe I JBwelded the triangle area instead of using a pipe. You should be able to tell if it does anything for you when you datalog. Remember the split BLM issue is not going to be the same but it is a tool to indicate a problem with either side for the guys that have 2 injector drivers. The best we can hope for is to try to find problems at idle.

 

Anybody know if the BBK throttle bodies, in particular the 58mm model number 1539 for the 89-92 year cars, should be modified like this?

I'm seeing some symptoms of the split BLM issue using my super ram. I'm assuming from looking at that intake that it does npt have the runner ports either.....

 

In one word YES! Look on the LT1 sites. These are some of the bigger offenders. The original TPI TB's have no IAC bleed hole either.

 

So, if you're familiar with a SuperRam, how far would you extend the pipe into the "pizza box"?

 

One thing I'd be concerned aobut is a long pipe cantalevered off the throttle body. It'll start vibrating and eventually break itself loose over time. LAst thing I want is piece of pipe bouncing around in my intake. Maybe for a test it'd be ok, but I'd want something more reliable for long term use.

 

That's a very valid point, I think I'll pass on the long tube idea. Pr maybe a rubber hose? Still, I'd hate for the clamp to ever work loose, either. I think I'll just eliminate the long pipe idea, was just trying to direct more air either to the center (or the right side since I seem to be richer on the right than the left.

 

The only thing I was thinking about as an alternative...

The MiniRam has four vacuum ports- two on each side, between the #4 and #6 runners as well as between #3 and #5 runners. If I could somehow reroute the IAC air along the outside of the manifold through some hoses, I could plumb the IAC air into one port per side. Or simply have the idle air come from multpile sources, that is, the throttle blades, the IAC itself, and the side ports. With air being drawn from all of these sources, maybe the distribution will improve??

 

I'm obviously no expert on this, but that sounds reasonable enough. Not sure how you'd go about routing the IAC air out of the TB though. If that could be easily done, another vacuum port could always be added to my SuperRam on each side for equlaized distribution.....

 

That's the kicker...

 

Solid gasket over the whole into the plenum and drill and tap a nipple/spout out the bottom?

 

The hardware won't support it.
Note that a NB only needs one wire.
So which way is the (small) current flowing?
Which end of the sensor wire is grounded?
2 wb's or make up a ckt to use a second NB.


For the external IAC.
I believe the turbo buick's use an remote mount IAC.
The big port on the rt side of the TB is for filtered air to the valve cover. You could use that as your source. Then just pick a vac port to let the air into the plenum via the remote iac.


Vern, I looked at my BBK 58mm TB. Yes it has the problem. It has two slots that allow the IAC air into the plenum. But I don't think the SR has any plumbing to direct the air to each port. It just dumps into the front of the plenum.

 

Not sure if this helps you at all, but:

Individual cylinder fuel trims for my Camaro


Individual cylinder fuel trims for a 95 Impala SS


Hardware wise, the only differences between these two engines are the heads, cam and exhaust (and a few things in front of the TB that I'd argue don't matter). EVERYTHING else is the same.

Here is a more graphical view of the difference that I just slapped together:

Camaro idle:

Camaro off-idle:


Impala SS idle:

Impala SS off-idle:


It at least helped me visualize the differences better. I think the lesson that I get is that it doesn't take much of a change to require different idle trims. The off-idle trims aren't as drastic, which makes sense.

 

Find yourself a 2.8L IAC housing, and chop off the one side, so you basically have a nice remote IAC housing. Bolt that to a thick plate (thick enough to drill and tap for your choice of NPT fittings, and use as a remote IAC block. I'm using one for a stack injection system I'm putting together. If you want, I can snap a couple of pics.

If there is enough room, Vern, you might even be able to put this thing under the plenum on the superram (esp if there is no egr valve installed), heck you might even be able to adapt it to the egr port itself, as they also route through the manifold and run to each port.

 

A few pics might help some of us find a 2.8 IAC thingy.

 

Scott -
That's how I remembered it being as well, but haven't had it off in a while to be able to say for sure. So I wonder how drilling through the back of the TB is going to have any benefit? But I sure have the symptom of split BLM's. Right now I'm doing all my tuning for the drivers side of the motor (the leaner side).

kevm14 -
Those numbers are very interesting, food for thought. That's the primary reason I've been casually thinking of someday going to an LT1 - the SFI aspect. Already got a couple of manifolds and an ECM in the garage, but no harness (the expensive part LOL), Oh well, that's probably years down the road anyway...

jwscab -
Pictures would be very nice to see on this...


I've also wonder about the EGR. Having never cut a manifold open, I have no idea where the EGR or PCV inputs go with respect to the individual cylinders. I'd like to think they both go to all of them, but am afraid to count on it without verifying it.

Thanks for all the info and ideas!!!

 

PICS... PICS.... PICS.....

 

I have both of those masks...

It's what convinced me that I have a distrubtion problem and not a mechanical/electrical one.

 

OK, one of three pics. I cut one end off of the part, you can see the kinda rough edge on the one side. Kind of dark, so I apologize.

 

two, the upper left edge in the picture is where I cut off the extra piece.

 

last pic. these parts are on the throttle body of 2.8L v-6 engines, which are extremely common in junkyards. I beleive they are on the bottom side, but its been awhile since I looked, they might be mounted on the side. One thing that is not obvious in the photo, the inlet nipple kind of points down on the flange, so in order to mount the thing flat, you need something like 3/4" plate to mount it to, to allow for a nice hose transistion. The nipple is the inlet, the funky looking hole is the outlet, but it really doesn't matter when you're fabbing stuff, its not directional really. Just a 'needle' and seat really.