Building an LN3 from spare parts plus a Supercharger

[2seater]

I am going to have one of my spare Memcals modified by Ryan, even though I am sort of winding down on this or similar projects, and it is still handy to have to allow easy plug in of a laptop. For the short term, I wiped and burned the other possibly sacrificial Memcal so I could at least drive the car. I loaded the updated program with a little more "pump shot" and it may be marginally better, but it isn't cured. Good enough for now so I can put a few miles on it.

 

I am not sure the almost stall idle thing during warmup is the IAC's problem. If you have heard the intake through an open cone filter, you can certainly hear the IAC as it opens up to keep the engine from stalling, and this one is very audible. 

[Ronnie]

15 minutes ago, 2seater said:

it is still handy to have to allow easy plug in of a laptop

Are you able to make changes in the laptop that take effect in real time so you can drive it connected to the laptop to see what effect it has before burning a chip?

[2seater]

1 hour ago, Ronnie said:

Are you able to make changes in the laptop that take effect in real time so you can drive it connected to the laptop to see what effect it has before burning a chip?

Yes, I can. It is called an emulator from Moates. I have never dedicated the time to really get analytical but at this point I just need to get where it is drivable and that needs a starting point. Right now my option to do the computer connection is limited or I could do that sitting still.

[2seater]

I guess I am at a juncture where I need a favor from anyone willing to do a test. I just went through the IAC, which was already pretty clean but swabbed the passage with a few Qtips and sprayed the pintle and shaft with carb cleaner plus pushed the pintle inwards a little. I did the IAC reset, key on 10 sec and then off five seconds before starting and that all worked as it should. I also pulled the MAF which looked clean and reinstalled. I then started the car and went through the ECM data. Everything looks normal and readings respond to throttle input but this is where I need input. I was looking at ED08, spark advance which was sitting at 20 degrees at warm idle, drop into gear and it jumps up to 27, all normal. I then started blipping the throttle to various degrees and noticed the timing dropped off before recovering, sometimes as low as ZERO degrees. This corresponded pretty well with the bogging although even though our system diagnostics are very useful, there is a little lag time as the input flows through the ECM, BCM and to the display. This seems very wrong to me, but of course I have nothing to compare it to now🙄

 

I have been in contact with Ryan at GM Tuners and he mentioned he hasn't had any issues with off idle bog requiring any significant changes to the throttle response. He did agree it is possible it may need more pump shot due to the much larger throttle body, but by and large, this is a new issue to him.

 

One other maybe not even related but idle vacuum appears to have dropped by one to two inches of Hg vacuum. That would seem to indicate a vacuum leak or the IAC is opening further to compensate for something?

[Ronnie]

Here are some numbers for comparison

 

ED08:

Cold engine idling in park - 24-25

Cold engine idling drive - steady at 28

 

Warm engine idling in park - steady 20

Warm engine idling in drive - steady 26

 

Warm engine idling FAST in park - steady 33

(Guessing 1500-2000 rpm, Can't watch tach and ED08 at same time)

 

Blipping warm engine in park - bouncing between 28-37 - occasionally hit 43-44 for a split second and fell back

(Didn't notice a drop when hitting the throttle)

 

Engine torqued up tight with foot brake in drive - steady 45

 

Could the knock sensor be causing your problem?

 

 

 

[2seater]

Interesting question regarding knock. I will look at that but I will say I have watched knock counts quite a bit due to the s/c addition but not really at idle. I will look into that👍
 

Your numbers look very normal that’s what prompted my concern. 

[2seater]

I was intrigued so I went out and gave it a try. Key on and engine off, ED17 is at zero. Start engine, reenter diagnostics and ED17 is at 161 knock counts, pretty much in the ballpark of what I have been seeing as startup noise, 155-170 counts. Stab the throttle repeatedly and after a bit of warmup, got the big bog and internal cough, but no response on the knock sensor, so it doesn't appear that is the cause. I did see that huge timing drop repeat itself, so that wasn't a fluke. Prior to starting the engine while I was in diagnostics initially, I tried advancing the throttle as slowly as I could to watch the TPS reading. It does increase without an apparent dropout but it isn't really smooth. I have done this many times in the past and you can usually get a smooth progression, both forward and back, but this throttle feels almost sticky. I heard an engineer call the cause of that as "stiction", a sort of resistance to start moving, but if moved more rapidly it feels smooth. In any case, while the TPS looks sort of normal, the numbers have little jumps in the progression, like .42 to .48 then .56 and on and on. Replacing the TPS will be a chore probably requiring removal of the throttle body as it points directly at the t'stat housing.

Thanks again

[Ronnie]

2 hours ago, 2seater said:

but it isn't really smooth. I have done this many times in the past and you can usually get a smooth progression, both forward and back, but this throttle feels almost sticky. I heard an engineer call the cause of that as "stiction", a sort of resistance to start moving, but if moved more rapidly it feels smooth.

Is the throttle plate sticking or dragging in the throttle bore? Do you feel the sticking when you move the throttle from under the hood without moving the throttle cable? Check to make sure the sticking you are feeling isn't the TV cable going to the transmission sticking or in a bind for some reason. Anyway, I doubt that sticking is causing the bogging unless it is screwing up the TPS someway.

[2seater]

I appreciate all input. Ryan got back to me and stated the timing should never drop below the minimum in the timing table unless knocking or overheating. Minimum in this case would be 9.4deg way high on the load scale. It definitely drops well below that.

Secondly, with more patience I was able to get the TPS to advance by .02v increments from idle .42 to over one volt, so it seems the TPS doesn’t have an obvious drop out. There is no knocking recorded while running. I even installed a different MAF sensor and result is the same. This issue appears to have existed without recognizing it through two ECM’s and three Proms? Something is right in front of me and I can’t see it. The other timing possibility is the ICM, which is the Delco style with cheap new coils, same as was on the previous engine?

[Ronnie]

14 minutes ago, 2seater said:

The other timing possibility is the ICM, which is the Delco style with cheap new coils, same as was on the previous engine?

I would do a swap if you have replacements. Easy thing to do to try to eliminate the problem. Lots of CPS problems going around lately too. Just saying... 🙂 

[DAVES89]

I have an extra tested ICM and coils if you need them...

[2seater]

22 minutes ago, DAVES89 said:

I have an extra tested ICM and coils if you need them...

Thanks. I have a takeoff Magnavox as a spare and will try that first. I am just looking for something that seems to make a difference, even if it's bad.

[2seater]

44 minutes ago, Ronnie said:

I would do a swap if you have replacements. Easy thing to do to try to eliminate the problem. Lots of CPS problems going around lately too. Just saying... 🙂 

I don't know quite what to think right now. The CPS is the new large style that is nonadjustable, but never say never I guess.

[2seater]

I am sending a Memcal to Ryan for modification with the socket so I can more easily monitor what is going on directly. In the mean time, the last thing I tried this afternoon was installing a Memcal modified by Ryan eleven years ago, labeled turbo 1.1. I had checked and the injector constant is correct for the 30# injectors currently installed so I figured I had little to lose by trying the idle and off idle behavior while sitting in park. It has more spark advance in the lower and mid range areas of the spark table, which the engine seemed to like. There were a couple small bobbles but most of the time, the engine would zing right up, along with increased timing. The two bobbles were not severe and did correspond to a timing drop to 17 and 13 degrees from the normal 20 at warm idle. I watched the knock counter and it showed zero knock counts no matter how hard I stabbed the throttle. In short, it seems this is at least part of the answer is contained in timing tables without yet knowing what is causing the unexpected drop. Time will tell but for now I intend to spend several weeks at my cottage and this will have less priority for a while.

 

[DAVES89]

Any progress on the mem cal for your supercharger?

[2seater]

Dave reminded me I haven’t posted lately but I am still on my extended stay at my cottage and the car is at home. One item did get resolved and Padgett will probably recognize it. Ryan wasn’t able to solder a new socket into a Memcal as was done previously but we now have this workaround that anyone can do if desired. It is an adapter from Moates that connects a stock Memcal on one side to a socket for a standard 256k chip or a plug from a computer for tuning purposes. In this case I have a ZIF socket for ease of use but that isn’t required. The whole assembly plugs into ECM where the Memcal goes.

[2seater]

Back home again and just for kicks, I tried the car this morning with one of the old Memcals that had been done by Ryan back when we were tuning for the turbocharger, eleven years ago IIRC🙄 Surprisingly, it fired right up even though it had been sitting since July 14th, untouched. No battery disconnect and no maintainer in place. I don't know why I don't seem to have the battery drain issues that sometimes are reported? Actually, aside from the battery question, I knew it would run as I had tried it as a substitute when the previous Memcal went bad. This time was different though, I went for a short drive. The engine is definitely happier with increased ignition timing at slower speeds and idle. Not super snappy but no bog or sag either. Moderate throttle, even seeing a couple of pounds of boost on occasion, showed zero knock counts. A good place to start when I get to tuning in earnest. I always wonder if the knock sensor is listening, even when I am pretty sure it is, judging by the counts I see on start up. It left me no doubt when I booted it fairly hard from about 40mph and with 4-5psi showing, the knock sensor jumped by 2000 counts, so I am pretty sure it is working😖

 

I noticed a whine coming from somewhere when I was returning home and that turned out to be under the hood. I was mainly concerned about the used supercharger but it turned out to be the alternator. It was a sort of bonus that it came with the donor engine, and even better that it was 140amp, but it will need a rebuild. Along with the noise, the output dropped a little, so time to swap my 120amp back into the car. The original will need to be re-clocked 180deg but that's no issue.

[Ronnie]

Looks like you are headed in the right direction on getting the proper chip for your SC engine.

[2seater]

Not really a tuning update but I tried an empirical test by using the original timing table for a S/C engine, the one that blubbers and is slow to wake up, and added 10 degrees of timing across the board. That change alone almost cured the cold start and low speed issue, not completely, but much better. This pretty much confirms that the timing table is where I need to concentrate. It now has probably too much at idle, showing 36 degrees at warm idle in gear, but it doesn't seem to mind for the time being. Drivability is very good. The S/C simply feels like the engine is larger, all the time. To quantify as best I can, it feels like a 300+" six vs 231". The stock rating for the '95 S/C engine is 225hp, 275tq, and I think this is probably a good ballpark figure, with maybe a little more when it can be pushed harder. This engine is slightly larger, four whole cubic inches🙄, the heads have been massaged some to flow more than stock, the compression ratio is a half point higher at 9:1 and it has the more aggressive '88 cam. The exhaust is 2.25" vs the S/C engine 2.5", but it does have a higher flowing cat and a straight through muffler. I don't know if my smooth merged flow rear exhaust manifold is a plus or a minus, but I am going to say it's a plus😎. I am warming up to this combination more and more, not for ultimate hp, but just the immediacy of the package. The turbocharger can be pushed higher and harder, but that's not what this car is about. I will say the S/C is probably harder on the transaxle because it is there, immediately. The turbocharger being a bit slower to spool is a bit softer on parts. 

 

One other observation, mostly from the distant past but maybe a little applicable here. Way back before the turn of the century, my initial forays into improving performance involved a hi-po chip, among other things. I believe it was Ed Wright at Superchips that did my first one. There were two or three levels of performance available, and the best was supposed to be using 91octane and a cooler thermostat. Of course, that is what I wanted but the first thing I noticed running premium fuel was the loss of crispness to the throttle. The engine ran great, but it no longer jumped as soon as the throttle was applied, no little screech to the tires. I sent the chip back and asked for more timing to be added, which he did. This helped so I sent it back a second time and asked for more yet. It finally got its snappiness back and I was happy. Overall, it maybe improved the performance slightly but looking back at it now, it indicates to me that it isn't a terribly efficient combustion chamber design which generally wants more ignition lead for best output. I would bet the Series II with the heart shaped chamber needs less timing with reduced negative load from starting ignition early?

[Ronnie]

59 minutes ago, 2seater said:

I am warming up to this combination more and more, not for ultimate hp, but just the immediacy of the package. The turbocharger can be pushed higher and harder, but that's not what this car is about. I will say the S/C is probably harder on the transaxle because it is there, immediately. The turbocharger being a bit slower to spool is a bit softer on parts. 

After you get the chip dialed in, you will have the engine I've always wanted in my Reatta.