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Building an LN3 from spare parts plus a Supercharger


2seater
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14 minutes ago, DAVES89 said:

sorry, no picture...

I fixed it😖

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Looks like you are very close to putting into the car. I'm anxious to hear how this engine compares to your turbo.

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2Seater, the plug wires go over the top of the supercharger.

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Thanks Jon. I made my own custom set which can go under or over. There is actually a lot more room for the rear plug wires under the S/C front drive than the N/A. I’ll know more about what works best when I get to running the wiring harness for the engine

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I have had company for the last week but I am actually getting ready to bring the car home from storage and maybe get started on the swap. One of the things I wanted to sort out prior to dropping the engine was installation of the front engine harness which snakes through the front brackets and accessories. It connects the ICM, cam sensor, crank sensor and it plugs in at the right rear of the engine. My donor engine which gave up the supercharger did have this harness in place but it appeared to be damaged after stripping the crusty loom from it. The photo below shows what I mean although as it turns out, only one item is actual damage. The green wire at upper left is indeed damage from unknown cause. The dead end black wire next to it goes nowhere. I imagined there was something missing that connected to it but this is not so. This wire connects to cavity “k” at the ICM which is not actually used so there is nothing wrong with it. The other two items toward the right side are spliced wires that were covered with deteriorating tape, one white and one red set. Again it was assumed to be damage but it is in fact correct as built. This harness has very minor color differences from the LN3 but is otherwise perfectly usable, repairs aside. I ordered a replacement from Jim Finn and while installing new outer loom on the replacement I found a pair of wires that had a section of insulation about 3/8” long missing. The pair of wires were actually stuck together and touching where bare of insulation in a common loom to the cam sensor. I don’t know if this is very common but issues were noted on both harnesses I took apart which seems to be a trend??

 

1BCB4072-9E17-4DBA-B005-D4690D37EC3B.jpeg

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After you run the engine control wires you will find it pretty tight under the supercharger, the wires can interfere with spark plug wires firing correctly.

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24 minutes ago, jon L said:

After you run the engine control wires you will find it pretty tight under the supercharger, the wires can interfere with spark plug wires firing correctly.

A valid point, thanks. I think I have heard the reverse can be the true as well, induced voltage in sensor wires from spark plug cables

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I purchased a spare front engine harness from Jim Finn and I have mentioned it before but I finally got it threaded through the front of the engine yesterday and I did need to take the large accessory bracket off the front of the engine to do so. I also installed a new dipstick tube and stick, also from Jim, so it is pretty much ready to drop in place now. 

 

In the mean time, an observation: I copied the supercharged timing table into a chip for use in turbocharged form. Everything else on the chip is exactly the same as I had been using in turbo form. I never got around to optimizing it as I should have so before I swapped engines, I thought I would see how it performs with a stock timing table designed for a boosted engine, albeit a supercharged rather than turbocharged one. This was just for observational purposes but I quickly found it is clearly not correct for an old school turbocharged engine. The low speed performance was so soggy it feels like two cylinders are asleep. It wakes up a little bit when the manifold pressure gauge swings into positive territory, but there is definitely a difference in the needs of the two different engine styles. I know the S/C engines generally have good bottom end response vs an old school single turbocharger which needs to spool up, but this timing change cut the legs out from under the turbo response. I guess it is time to stop procrastinating and get the engine swap on my dance card.

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Just to confirm the timing table hypothesis, I burned another chip with the exact same information except I substituted a table from a 12 year old tune from GMTuners, one of the seven or eight files he sent me way back when. The engine is happy again although still a bit soft down low. The low end softness seems to be typical of premium fuel performance in an N/A engine tuned for regular 87 octane. I have noted that before. There is a note to self here: the engine will not start with only half of the chip pins inserted into the socket😖 The low end soft launch is probably a good thing to ease the strain on the trans. when it can least handle it.

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2 hours ago, 2seater said:

There is a note to self here: the engine will not start with only half of the chip pins inserted into the socket

haha I think all Reatta owners should try to remember that.

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I have a rebuilt trans in the Red if you want to try it...

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