chimmike

QG18DE Naturally Aspirated Tuning:

Keep in mind, while upgrading your QG18DE powered car with naturally aspirated parts, the power gains will not be substantial, and it will cost a significant amount to get some decent power in naturallly aspirated form. For the stock QG18DE, the best bang for the buck is turbo. You'll soon learn this.

Let's start off with some general rules:

1)Horsepower costs money. The question begs, how fast do you want to go?
2)Any 2000-2004 QG18DE powered Sentra in the US uses the same aftermarket parts. Differences are in the exhaust where there will need to be a flange welded on to the main cat in order to bolt on a cat-back exhaust. This is not a big deal.
3)Do not be fooled by imitation products, or no-name off-brand companies that claim the same power and performance gains as reputable brands
4)Any e-bay auction or company that sells a product for less than $100 and claims 20hp increase is bogus. I.e. the ebay "performance chip" which claims to gain 20hp. It is nothing more than a $0.25 resistor that won't do anything. Basically, they claim it will fool the ECU into thinking more air is going into the engine, and it will dump more fuel in. The idea alone is bogus. Here's why; If the ECU were to be fooled (and it IS NOT ) into dumping more fuel in the cylinder, it would cause the car to bog, run rich, slower, and eat gas. Why? Because there really isn't any more air entering the engine than before!
5)When performing a modification, be prepared. If you've never done it before, have someone with you who has. If you are nervous, scared, don't know what to do, or other, pay someone to install the part!
6)Don't be a ricer. Washer nozzles are not a mod. Underbody neons are not a mod. Hideous coat hanger wings are not mods. FWD cars do not need downforce! I don't care how you try to justify it...that's fact. No wing is specifically made for the QG18DE powered car to provide beneficial aerodynamic effect.
7)The QG18DE is not a street monster. It wasn't meant to be. It's an economical, clean, otherwise weak and slow engine. We're trying to change that!
8)There is no way to physically adjust ignition timing on the QG18DE. It is direct igniton, and the timing is continuously variable.
9)No, you don't need iridium spark plugs. They're good, but not $11-13 a plug good. The stock NGK platinums are excellent. ALSO, please stay away from using bosch platinum plugs! They're horrible in nissans, as many will tell you. Stick with NGK or denso. Also, check your owner's manual for the proper spark plug and gap.
10)No, you can not use a VAFC or VTEC controller on VTC or CVTC. VTC and CVTC are both variable and are a totally different system than VTEC. VTC/CVTC is there from idle to redline maintaining the proper cam timing for solid linear power throughout the powerband, instead of having a changeover point at a set rpm like VTEC. Be happy you have VTC/CVTC, it's a good system!



Modifications
OK, now that we've covered some basic rules, here are the basic NA modifications:

Cold Air Intake
Header
Exhaust
Crankshaft Pulley
Apex'i SAFC or other piggyback air/fuel controller
Sun Auto Hyper Voltage System (NOT ground wires!)
Energy Suspension Motor Mount Inserts

Now, Let's start with the Cold Air Intake.

Basically the whole purpose is to bring in more air of a cooler and therefore more dense fashion (as cooler air is more dense than warmer air. Density refers to the amount of oxygen in a certain volume of air)

Expect a CAI to gain anywhere from 3whp to 7whp. It will sound like more, but it isn't. Also, unless you plan on driving through 2' deep puddles of water, you don't need to worry about sucking any into your engine.

Moving on to the Header

Currently, the only header available that I'm aware of for the QG18DE is made by Hotshot Performance and is of a 4-2-1 design. This means, as it leaves the head, it goes from 4 runners (4 cylinders=4 runners) into 2 runners, to a collector. This maximizes power throughout the powerband, and really opens up the top end from stock. Expect upwards of 10whp from this. Generally the best way to go is: CAI, Header, exhaust.

Speaking of Exhaust, why don't we?

The best all around exhaust setup for the QG18DE is a mandrel bent 2" setup, with a big resonator (if you have a header, you'll want this, I promise you). If you plan on running nitrous oxide (Please refrain from saying NOS all the time, it'll make you sound better) I'd suggest a 2.25" cat-back (catalytic converter-back) exhaust. This will help the top end flow when on the juice. Don't expect too much power from exhaust; maybe 3-5whp, mainly gained from taking off the crap stock muffler.

Now we move to the Crankshaft Pulley

The Crankshaft pulley (made by Unorthodox Racing ) will help free up maybe 3whp by lightening the rotating mass of the crankshaft. Don't worry, the QG18DE crankshaft is internally balanced, so messing with the crankshaft pulley is safe. Main gains are not from underdriving, but weight loss. You can really tell the gain while using the air conditioning. The car will not bog down as much. This is not a mod an amateur with little experience should try by himself. Take my word on this one. Also, the belt sizes you'll need can be found on their website, just click the link.

Let's perfect the air/fuel mix with the Apex'i SAFC

This is what is referred to as a piggyback ECU. Basically, it manipulates the signal between the Mass Air Flow sensor and the ECU, allowing you to fine tune the air/fuel mixture. This HAS to be tuned on a dynamometer (dyno) with a wideband o2 setup. Otherwise, you're playing with fire. Expect gains anywhere from 3-5whp or more peak, but solid gains throughout the powerband, if tuned correctly.

Now on to the Sun Auto Hyper Voltage System

This basically bolts on to the positive and negative terminals of the battery and helps maintain constant voltage throughout the car. Expect a few whp from this. Good for those who have maxed out most possibilities and already have most NA mods.

And finally the Energy Suspension Motor Mount Inserts

These are made for the 2000-2001 sentra SE (with SR20) but they will work very easily and pop right in. They can be had for less than $50 from Powertech Imports (click any of the links on the website to get to his website and e-mail him). Basically, the stiffen the front and rear mounts to prevent movement, transferring power to the ground better. There is a tiny bit of vibration in the car at idle, but so little you'll forget it's there after 5 minutes. It's a great modification for the buck.

After this, you run into head work and things like that, that aren't considered bolt-on modifications.

Unfortunately, there are no aftermarket camshafts available at this time.


If you would like to see anything added, please PM me

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2003 Redline 350z Enthusiast 6MT Turbonetics Powered