Turbo Kit Questions
 

I have a few questions regarding turbocharging a 3800.
1. The stock sensor just uses a gromet to insert into the air box, so can the stock IAT sensor be reused by drilling into the charge pipe before the throttle body? Wouldn't that get pushed out under boost?
2. I know the MAP sensor needs to be replaced on the NA L36 to a 2 bar, but can the stock MAF be reused?
3. Regarding spark plugs, what is recommended as far as heat range and gap? Would a -4 heat range and a smaller gap from stock be beneficial?

1. The IAT shouldn't pop out at all. Mine hasn't with the Novi Supercharger. But yes, I just drilled a hole that matched stock, and swapped the gromet + sensor over to the pipe.

2. Stock MAF is good for a good deal of air. I don't know how long until you'd max it out, but you should be fine on the stock MAF.

3. I would start with Autolite 104s, and see how the car responds. I wouldn't go too cold at first.

I know the e 3 are a little cooler but not much. I have a supercharge setup on my 5.3 mod motor in my cougar. yes I said 5.3 it has the same bottom 5 bolt main but stock bottom stock setup with mild boost evert thing should be fine. it will give you time to save to build a engine and have a trans built at the same time while learning the set up. not knowing miles on engine and trans

In regards to the MAF, I don't plan on running any more than 10psi for now on the street.

As for the spark plugs, how exactly is effective heat range and gap determined? I believe I read that going to cold will foul the plugs, but that's the extent of my spark plug knowledge. How do you determine what gap is best for a certain setup?

Here's a good read: https://www.enginebuildermag.com/201...ug-heat-range/

I'd second a 104 or similar to start. 4 heat ranges colder (like a TR8) is way too cold for a street car.

As far as determining each:
-heat range depends on type of plug, how much power it's making, and use of the car. Go too cold (especially on a copper plug) and it wont self clean well and you'll be pulling plugs much earlier than normal. On the flip side you dont want too hot as it can cause a hot spot/ pre ignition or at the worst case you melt the plugs.

From what I've seen, most 3800 people err to cold. They pick up something 3 or 4 colder than stock for their basic bolt on street car and then end up with issues. You have to keep in mind with a street car that its going to be at idle or very low speeds 99% of the time. This requires much less heat extraction than a drag car that idles / is at WOT closer to 50/50. You can get away with a much colder plug doing that. Type of plug matters too as a huge copper tip runs much colder than a a fine iridium wire for a given heat range.

If you're buying an off the shelf turbo kit, they should come with it. If not, just pick up some 104s, run them a bit, and see how they look.

-gap, IMO you want the biggest gap you can get away with without getting blowout. The more boost / power, the harder it can be to ignite so you have to tighten the gap to keep it from missing under load. It's another trial /error thing, but I usually err on the tight side initially so I know 100% itll fire and then open it up a bit after the car is tuned in and I'm putting in my second set of plugs. I dont like risking too much gap initially in case the misses aren't frequent enough for you to catch them (ie it doesnt totally fall on its face) because then you could be playing with WOT tuning not realizing its reading leaner than it really is. Each plug chance I bump them up .005 until I cross the threshold, then I'll pull them and bump them back down.

Im putting my own kit together, and wanted to learn more about how to "tune" spark plugs to my build. I'll definitely try out the Autolite 104s. I've been running NGK TR55s at a gap of .055-.060 How much should I drop in gap to start off with?

I do think the 104 heat range is a good starting point for a street car, especially if you'll have the boost down. Once you get up to the 500 or 600 whp you've been talking about, you'll likely be forced to drop one more level, especially if you start tracking it and have extended duration pulls.

One thing to keep in mind with copper plugs (which the 103s, 104s, etc are) is that even with proper heat range, they still wont last long. It's pretty old school tech, so changing plugs every few oil changes is not uncommon. The 3800s do seem to really like them though. Just keep in mind there are platinum/iridium options too thatll last longer. Downside is they're more expensive, so if you get the wrong range, you could be throwing a lot more money away.

There is a lot of good info out there about how to cut open and read plugs, but it's more geared towards drag racing. A street car will see so little WOT time that it's not really relevant.


As far as gap, I'd probably split the middle to start. Stock is usually .060 or so and getting down to .025 or .030 will light almost anything. So I'd probably shoot for 0.040-.045" to start (especially if you're starting on lower boost) and work from there.

Got it, thanks. I know copper plugs do need to be changed way more often, and I'm fine with that. It's easy enough, except for maybe cylinder 1, which is very cramped with shorter dog bones.
A side note related to cylinder 1: I've been having a bit of a problem with the wire backing off the plug, and obviously causing a misfiring cylinder. I don't have the metal shield and spring thing on my wires. I suspect the problem is my exhaust, which is literally just the downpipe chopped before the cat, and causing lots of harmonic vibration at idle and cruise.

Sounds like a garbage plug wire to me. The clip that grabs the top of the plug has lost tension somehow. No way the exhaust is loud enough to vibrate a good plug wire off, there are some absurdly loud cars out there (thinking some of these fender dumped LS swap) that have no issue with stock wires staying on.