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Noob Turbo L-16 from Hell


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For a light turbo engine to 14 PSI boost....

 

Gap the top ring 0.005" X the bore in inches. 3.27" X 0.005" = 0.016"

Gap the 2nd ring 0.005" X the bore in inches. 3.27" X 0.0055" = 0.017"

 

 

If unsure and not running much boost control, ignition retard and cooling make it 0.017" and 0.020". Wider is safer than too small but excessive gap will loose you some power.

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Car is misfiring under load like after 2k rpm. Able to drive with little throttle until I get up to half way the motor can't handle it and start misfiring and sputtering. Fine when I rev it all the way up in neutral or disengaged.

 

According to my boost gauge, my carb isn't seeing boost.

 

Checked timing and fuel, both good.

Checked spark plugs and they looked black/burned.

Brand new iridium .035 gap

 

I'm thinking since my carb isn't sealing with any boost, my special (boost activated 2psi) power valve is not activated and enriching fuel to my secondary

 

Black is too rich. If no boost don't decrease your plug gap.

 

How is a turbo going to blow the spark out when the cylinder is sealed at about 1/4 the way up from BDC??? Both valves are closed and the cylinder sealed tight??? and you are on the compression stroke??? Widen the gap if the MSG is a capacitive discharge... the spark is too short a duration so make it jump farther to expose more spark to the gas and air. Try 0.040"+

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Not how that works, Mike. I agree, he needs to get it on boost before closing up the gap, but you do close the gap up on most turbo engines due to the chamber pressures being higher.

 

Turbos don't "blow the spark out", as is commonly stated, that's just hillbilly talk like you say above. They essentially act like higher compression, which is what we want anyway or we'd not be bothering to boost it...the higher the combustion pressure chamber at the time the spark is timed to ignite it, the more voltage is required to jump the gap. Also, bigger bang, more fun, all the good shit.

 

So an 8:1 compression N/A engine may easily jump a 0.040" gap with Coil A, but that same 8:1 compression engine with 14lbs of boost will mean knocking the gap down to 0.035 or even 0.030" to get it to jump the gap with Coil A. An 8:1 compression engine with 14lbs of boost runs approximately the same combustion chamber pressures as a 14:1 compression engine. In the end, you can either close up the gap, or get a higher voltage.

 

"Energy", as advertised heavily, really doesn't matter, when it comes to actually jumping the gap. All about voltage and voltage risetime, when it comes to getting across the gap. Capacitive discharge systems work by dumping more energy into the primary side of the coil, which results in a higher *voltage* on the secondary...and they have a really decent risetime to boot, which only adds to their ability to light off a dense, wet, air-fuel mixture. They get more energy into the primary by discharging a higher voltage at a lower current-usually about 200 volts. The advantage is you can get the same wattage into the coil primary in a shorter time. At higher RPM, where the amount of time you have to charge the coil is rapidly going away, this is a big deal. (energy in joules = watts / seconds, so same wattage in shorter time = more energy)

 

To determine the voltage required to jump the spark gap, the formula is:

 

V = 3*p*d + 1.3(sqrt(d))

 

V is voltage in kilovolts

P is pressure in atmospheres

D is gap length in mm.

 

As P goes up, D has to go down-and it has to go down faster than P goes, due to being involved in both terms. So, let's get a few numbers to throw in there:

 

for an 8.5:1 compression engine, running 5PSI of boost, you would see approximately 170PSI prior to combustion. That's 11.5 atmospheres.

The spark gap would likely still be able to run at 0.035", a common factory plug gap. Works out to be 0.88mm or so.

 

V = 3*11.5*0.88 + 1.3(sqrt(0.88))

 

V = 30.36 + 1.219

 

V= 31,579 Volts. Still well within most factory ignition coils.

 

But what if we open the gap to 0.040"?

 

V now equals 35,899 volts. Still shouldn't be an issue for most direct fire or coil-on-plug setups, but at this level a distributor can start throwing misfires and crossfiring. Time to start watching the inside of the dizzy cap and your plug wires. Below about 42kv, most distributors I've ever touched are fine-the bigger the cap diameter, the higher the voltage can go before they start playing up.

 

Which brings up the next point-when you run a distributor, you've already got a disadvantage on voltage, because you have to jump TWO gaps-and the first gap can be pretty dang big! When's the last time you checked your rotor-to-cap gap distance? You've got to add that gap (which changes with ignition timing, and it usually goes opposite the way we'd like it to!) to the spark plug gap to get the total distance you need to jump. On engines with optical triggers that can be adjusted, you can make big gains by moving the trigger inside the housing, and then rotating the distributor housing independantly, so you can keep your trigger where you need it, but you can get the rotor to line up closer to the correct terminal when at maximum advance. Points setups tend to be *really* picky on this, depending on if they're leading or trailing points, machined into the shaft or press fit, etc...but optical triggers are pretty easy to dial in this way.

 

Also, ditch the iridium plugs. They're crap in turbo L-series engines, the fine wires get glowing and you wind up with preigntion, which you're already going to have issues with. Go with NGK coppers or single-platinums, and for the turbo L, NGK BPR7ES would be the ideal starting point. If the parts monkeys can't find that one, tell them you want NGK 3785 or 2023, those are the "stock number" for those plugs. If you just have to have a platinum plug, BR7EVX.

 

Just change your 12 bucks worth of plugs every 15000 miles when you change your plug wires, and you won't have issues. Sure beats putting 80 bucks worth of plugs in every time you want to change the gap...which can be pretty difficult with the fine-wire electrode plugs.

 

Also, use NGK plugs. So much easier to read plugs with NGK's and the L-series just runs better with NGK's over other brands-how the fuck the engine can tell a difference, I will never understand...but it fucking does.

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The L20B points and EI use a larger diameter cap than the earlier L16/18. I'd like to see how a good EI compares to an MSG for stock, and mild application.  I don't think the Turbo from Hell is going near 14 PSI and 5-8 PSI is more possible and likely.  

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The turbo from hell might not go there-but I'm sure other members may want to push 14, 18, 20 PSI...a stock L20B bottom end with 100K miles on the clock is still perfectly happy at 260HP or so. A good rule of thumb for the L-series engines is 66HP per piston for the stock bottom end, then you want to start looking at forged pistons. You can go higher-I've done L20B's at 280HP and they were fine-but that was on fuel that was MUCH higher octane than needed to run. (Engine would have been fine on 105, but owner ran 116 for safety)

 

The 5-8 psi boost you mention is why I did the math for that amount-for most street turbos, 7PSI is a good baseline, and 14PSI is pretty much the best dollars-per-horsepower for an unopened stock L-series. Beyond that point you get diminishing gains unless you start upgrading ancillary equipment.

 

If you run into a problem with spark, go to the VG30E coil from an early 300ZX-it's a direct swap but it's HOT HOT HOT. the MSD really isn't a big gain over the nissan stuff, except for having timing retard. That's the real reason to run one, timing retard and rev limiter. Starting in the mid-80's, the nissan exposed core coil was a mean little beastie..Don't forget you've got a metal zipper in your pants when you're leaning on the fender fiddling with the coil wire...

 

Is the L20B cap the same diameter as the big L28ET cap? I've got both the L6 Ei dizzy and the L28ET dizzy here to test manifold fitment with, I figure if it'll clear the L28ET cap, it should be fine for any 510/610/710 out there.

 

Unless it's absolutely nesscesary, I always try to avoid distributors and carbs with turbo setups, but they *can* work...and with some carbs you don't even need to re-jet, you jet up for normal N/A operation, then run a modulator ring in the inlet to get appropriate enrichment for boost. I'm not sure if it works for all carbs, but that's the way you do it on Solex/Mikuni/Dellorto/Weber carbs.

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  • 1 month later...

Please no negative energy, gotta take a break from this forum sometimes.

 

Subscribe TO MY CHANNEL GUYS THANKS and i'm not that ugly when my hair is combed :rofl:

 

Btw this thing rips holy hell! Feels so good, and i'm not even going full throttle in most of the video except when I turn the corner after the scion. External wastegate is SOOOOO awesome :devil: .

 

 

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You are asking for it at 14afr even at 5 lbs. Try to get it in at least low 12 afr. High 11 would be perfect. Also a 2 pt afr swing isn't good, even carbs shouldn't do that. You either still have a leak somewhere or you need a bigger main jet. Your transition to boost from vacuum sounds good though!

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Please no negative energy, gotta take a break from this forum sometimes.

 

Subscribe TO MY CHANNEL GUYS THANKS and i'm not that ugly when my hair is combed :rofl:

 

Btw this thing rips holy hell! Feels so good, and i'm not even going full throttle in most of the video except when I turn the corner after the scion. External wastegate is SOOOOO awesome :devil: .

 

 

https://www.youtube.com/watch?v=YTctYNcqSpo&t=50s

I love it dude, lol, keep pushing forward and now that you made this work, improve on it by making upgrades as you go :thumbup:

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The true test will be longevity, but it looks like after a bit of tuning you'll get it dialed in. Also, is the wide band sensor mounted 3 inches from atmosphere? I'm assuming that's just temporary.

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Please no negative energy, gotta take a break from this forum sometimes.

 

Subscribe TO MY CHANNEL GUYS THANKS and i'm not that ugly when my hair is combed :rofl:

 

Btw this thing rips holy hell! Feels so good, and i'm not even going full throttle in most of the video except when I turn the corner after the scion. External wastegate is SOOOOO awesome :devil: .

 

I smiled throughout the whole video lol.

Good job!!

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I love it dude, lol, keep pushing forward and now that you made this work, improve on it by making upgrades as you go  :thumbup:

 

No, This kid is a great example of perseverance, I have new found hope on millennials....keep at it, kid :thumbup:

 

Thanks :thumbup: ! And yeah there was times I was not as excited as I first was, but little by little  it's finally running!

Holy Blair Witch Project!!! Hold that fucking camera still.

 

 

So glad you got back to us on this. Figured you blew it up the first night and left.

 Driving stick one handed, go figure hehehehe

 

I smiled throughout the whole video lol.

Good job!!

Thanks, good to hear you feel my excitement :thumbup:

 

The true test will be longevity, but it looks like after a bit of tuning you'll get it dialed in. Also, is the wide band sensor mounted 3 inches from atmosphere? I'm assuming that's just temporary.

Everything temporary for now!! Once I'm done rebuilding this L-20b on the side imma blow this L-16 with 10 psi see how long it lasts

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You are asking for it at 14afr even at 5 lbs. Try to get it in at least low 12 afr. High 11 would be perfect. Also a 2 pt afr swing isn't good, even carbs shouldn't do that. You either still have a leak somewhere or you need a bigger main jet. Your transition to boost from vacuum sounds good though!

My set up is not finished yet hehe just my starting point for now.

 

I don't have my boost referenced power valve on yet which helps alot. I'm getting it all dialed in very soon, tuning and cleaning up my set up. Boost leaks on the carb hat and vacuum lines n :crying:

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My set up is not finished yet hehe just my starting point for now.

 

I don't have my boost referenced power valve on yet which helps alot. I'm getting it all dialed in very soon, tuning and cleaning up my set up. Boost leaks on the carb hat and vacuum lines n :crying:

 

Awesome man. Boost is addicting, you'll be at 15lbs in no time haha. 

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