In Depth Guide To Turboing Your NA Compression vg30de Motor (300zx):
In this guide I'll be talking about these key points:
-Engine health, and tests to do to make sure your engine is up to the task
-Can the Na motor really hold boost?
-Basic parts needed for a stock TT setup on your (10:5:1 compression motor)
-Power goals and parts recommendations to reach those goals
Before we get started, we need to check a few things to make sure that the motor you plan on boosting is healthy enough to withstand the increased power levels. Some easy things you can check before getting started with boosting your motor are oil pressure, spark plugs, and a compression test.
-Oil Pressure: (easily seen on the 300zx gauge cluster) at idle optimal oil pressure reading on the stock gauge is at the first tic or rather right around 30psi, under acceleration the oil pressure should rise to near or above the second tic or 60psi. If this holds true then your oil pump is functioning within the proper spectrum. If your oil pressure is low in both these scenarios i would recommend purchasing a aftermarket oil pressure gauge and testing this once again. The stock gauge for oil pressure has been known to be finicky and its possible your gauge is acting up. If your gauge reads low, DO NOT assume its acting up and boost your motor anyways. Your motor may be running just fine in Na form but with turbos you will need healthy oil pressure to keep everything lubricated and functioning properly. Even with a properly functioning gauge it isnt a bad idea to purchase a aftermarket gauge to ensure precise readings. If your oil pressure is low even after installing an aftermarket gauge, replacing your oil pump will need to be added to your budget. Na oil pumps will work just fine, but if you are replacing your oil pump you might as well get a tt oil pump. The tt pump will supply increased oil pressure since it was made for a turbo setup. Another thing to add is that the TT oil pump is cheaper then the Na one by around 15-20 bucks so why not.
-Check Your Spark Plugs: Spark plug condition can tell you a lot about an engines health and function, so it is imperative that you see just how healthy your motor truly is. Checking the spark plugs is an easy thing to do and goes hand in hand with the next topic of a compression check. Alright lets check our plugs. Pop your hood and grab these few tools: A set of pliers, Flat head screw driver, 12mm wrench or 12mm socket with a socket wrench, two 6" 5/8 extensions ( a 3' and a 6' will also work), and lastly a 16mm or a 5/8 spark plug socket will work as well. I like to start off by taking the balance tube off. There are two 12mm acorn nuts on the passenger side, one 12mm acorn nut and two 12mm bolts on the drivers side. You will also need to disconnect the vacuum hoses (use pliers gently to get them to twist then twist and pull them off), as well as disconnecting the S shaped hose that goes from the balance tube to the IACV ( depending on if you have replaced this before will depend on if you will use pliers to remove the spring hose clamp or use the screw driver to loosen the t-bolt clamp). There will be 3 o-rings under the balance tube make sure not to lose those. now un-plug each coil pack, remove the two 12mm bolts that secure each coil pack and lift the coil packs out. Next use your 16mm or 5/8 spark plug socket wrench attached to the two 5/8 extensions and remove each spark plug. Remember to place the spark plugs down in a way that you know which cylinder they were in, an easy way to keep track is to write 1, 3, 5 (passenger side of engine for LHD cars)) on the left side of a piece of paper and 2, 4, 6 (Drivers side of the engine for LHD cars)on the right side of the paper, then place the spark plugs on the paper according to the proper cyl number. Below are the most common readings for spark plugs, which can hint at the health of each individual cylinder.
What Spark Plug Readings Mean:
-Oil fouled plugs will have oil on them obviously. This can mean one of a few things, either oil is leaking from the valve covers down to the spark plugs, valve stem seals in the head are old, worn out and leaking, or oil is "blowing by" the piston rings and being burned in the combustion chamber.
-Fuel fouled plugs will smell like fuel. This can be contributed to one of two things. Either the fuel injector is out of spec and is pouring excess fuel into the cylinder, or the o rings for the fuel injector are worn out and allowing fuel to enter the cylinder by means of seeping past the fuel injector.
-Heat fouled plugs also known as Leaning out and can be identified as a completely white electrode tip, is contributed to the cylinder not receiving proper fuel (aka the fuel injector is out of spec), or to the fact that the spark plug being used isnt a "cool" enough plug for engine.
-Ngk plugs are rated on a heat scale the lower the heat rating the less efficient the burn. If you are using a heat range 5 plug and your electrode tip is white from a lean condition, and your fuel injector is working within spec and receiving proper fuel pressure, step up to a heat range 6 or 7 plug)
-Carbon Deposits On Your Plugs can also be contributed to a "rich" condition meaning the cylinder is receiving too much fuel.
-Compression Checking Your Motor: This is a pretty easy test to do, I recommend doing this test right after taking the spark plugs out. Ideally you want your motor to be warmed up before doing this test. (Removing your spark plugs is detailed above). First you want to make sure that you arent going to be injecting fuel into the cylinders while you do this test, so make sure to disconnect the fuel injector plugs and pull out the fuse in the fuse box beside the battery that controls the fuel pump. Screw in the compression tester to where the spark plug would usually go then have a friend turn turn the key to the start position in the car for about 2-3 seconds. you want to pay attention to the first compression reading you see ( it will jump up to lets say 70 after the first rotation of the motor then rise to its final compression number). That first compression number and the final compression number are the most important. Do this for each individual cylinder and write down the L( Low/first compression number) and the H (High/last or final compression number) on a sheet of paper beside the cyl number ( once again the 1, 3, 5 pass side/ left side of the paper, and 2, 4, 6 driver/ right side of the paper)
Ideal/Healthy Compression numbers: A "perfect" compression ratio in any given cylinder is 180 or slightly higher(for an Na motor). But since most of us dont have a zero mileage motor, you really want to see above 160. Also you want to make sure that each cylinder is within 10psi compression difference. Here is an example. cly 1: 164, cyl 2: 157, cyl 3: 160, cyl 4: 159, cyl 5: 163, cyl 6: 161. The highest compression is 164 and the lowest in that example is 157, putting them within the 10psi difference range. If lets say cylinder 3 had 135 psi then it would be way out of spec and would need to be addressed before boost. if your compression ratio is within a 10ish psi range but lower on the spectrum around 140-150psi it can still be ok for boost but it is toward the lower end of the scale. If you are below 135psi i would recommend a rebuild or buying a new motor before boosting it.
Why did you tell us to remember the first compression number and the highest/ final number?
Simply because the "low" number and the "high" number can tell you more about your motor then you think. Normally you want the first compression stroke or the "low" number to be around 50% of the "high" number. Example: low number (75) high number (150). the low number can tell us a lot about the inner workings of our motor. if the low number is approximately 50% of our high number then our valves are sealing properly. IF however the first number is significantly lower then the "high" number (example low number: 40, high number: 137) then that signifies that our valves are not sealing properly in which case rebuilding your heads or buying new heads/ head will need to happen.
Last Test Before Moving On:
Wet test: What this means is adding a tiny bit of oil to the cylinder (in through the spark plug opening, less then a water bottle cap), and then retesting compression. adding a little bit of oil can tell us if the piston rings are worn or not. each cyl with a wet test will put out slightly higher compression. however if you have a cylinder thats low on compression that jumps up quite a bit in compression due to the wet test, that can mean that the piston rings are worn. Example: low number 70, high number 140, wet number: 210. a normal wet number increase is around 20-30psi.
Can The Na (10:5:1 Compression) Motor Really Hold Boost?
Why yes it can. It can hold a lot more power then most people think. Ill be going through a little bit of history here, and providing examples, and information to show you guys just how capable our vg30de motors are.
In the late 90's and early 2000's there were a few individuals that did turbo their na compression motors. Back then it was a well known "fact" that the na motors would "blow up at 350whp", or that the "na wrist pins would shatter at 7psi." but that simply is not the case. The reason people thought this was in part due to a few different reasons. The biggest reasons came down to fuel and tuning. lets start with fuel. The quality of fuel in the late 90's early 2000's was sub par to what we have now. A lesser quality fuel is more susceptible to detonation in a high compression forced induction scenario. What this means is that the fuel will start to combust before the compression stroke is finished within a cylinder aka "pre-detonation." Pre-detonation (also known as det) means that the explosion that is supposed to happen at the top of the compression stroke to force the piston down, happens before the piston reaches the top. This increased pressure is essentially forcing the piston back the opposite way then its supposed to go, which can cause massive amounts of heat, and can melt or crack pistons. The next subject is tuning. Most people who boosted their na motors back then tuned the motor exactly how they would a tt motor. The issue with this is that the na compression ratio is 10:5:1, where the tt compression ratio is 8:5:1. this is a HUGE compression difference. The best way to explain how big of a difference this is is by explaining how much more power is made with that na compression over the tt compression at the same psi level. A stock Twin turbo setup on a 8:5:1 comp motor at 12psi usually makes 320-330whp. The same stock turbo setup on a 10:5:1 comp motor at 12psi will make 400whp. Thats nearly an 80hp difference at the same psi level. What this all means is that if you tune a na compression 10:5:1 motor at 12psi like you would a tt 8:5:1 comp motor you would immediately run lean (meaning not enough fuel and increased heat and pre-detonation). That lack of fuel, that lean condition and that pre-detonation destroys motors( BOOM). Fast forward to 2016 our fuel quality and ability to tune high compression forced induction setups has improved by leaps and bounds. The z32 community now has more then a hundred stock internal na compression motors now boosted making anywhere from 300-783whp. We have dozens and dozens of 400-500whp stock internal na compression motors that have been making that power for 3-4 years thus far and still running strong.
A Few Dyno Graphs of Stock Internal Na Compression Motors w/ Forced Induction: