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Discussion Starter #1 (Edited)
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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RAWRscareh
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could have saved SOOOO much space by just sticky'ing the link to your website lol.
good guide tho, i'm doing some of it
 

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HI chimmike

I had a look at u web site, its looking pretty good m8. One question, what make Strut Brace have you got on you car, is it custom made??

Cheers :cheers:
 

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your page says you've gotten a turbo hooked up to the 1.8 sentra

i would appreciate any and all details i just got an 04 sentra
traded in a 1.8 turbo vw i couldn't afford
and im missing that extra 75 hp
 

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Are any of you using a Unichip piggy back ECU, I have a 2004 South African 1.8 QG18 Almera sedan and have fitted one with very good results. Not sure if the Almera ECU is the same as in the US Sentra but it is one of the new Hitachi units. The Unichip can adjust the fuel & timing as well as drive an extra set of injectors if you want to fit a Turbo, you can also drive a shift light. We have fitted it to a 350Z as well and have easily been able to find more power when running a straight through exhaust. When adjusting timing on the 350Z the VVT angle also changed a bit due to the ECU being fooled into thinking the TDC point had moved but it had very little affect. Its an excellent mod, & when I sell my car I can just remove it & fit it to my new vehicle, my fuel consumption has been improved by running slightly leaner on part throttle and my full load power figures are much better being optimised at about 13:1 fuel ratio.
 

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Not sure about what it costs in the US, it’s pretty cheap here but in the US its probably about $500, you would have to find out from the distributors, their contact details are as follows

Unichip of North America
[email protected]
866.643.7400 Toll Free
503.640.7465
8am – 5pm Pacific
503.214.6444 FAX

The product is made here in South Africa so I took my car to the company that designs & manufactures it (Dastek). I have the Unichip Version D (latest version specially made for the Nissan ECU's). They also modified my ECU to remove the rev limiter, as I will be doing some NA modifications (Porting, high compression pistons & steel rods). At the moment the Unichip itself controls the rev limit.

They spliced into my wiring harness to fit it, if I want to remove it I just plug a bridging connector to the connector that goes into the Unichip and the car basically goes back to standard. I know that in Austalia & the UK most of the cars using the Unichip are fitted with a "Plug & Play" adaptor which doesn't require any splicing, its like a small harness with male & female connectors on either side and the Unichip connector already wired in. The one side connects to the ECU & the other side connects to the harness. I don't know if its available for the Nissan ECU's yet.

If you are going Turbo there is an optional Boost Controller that works with the Unichip, you could probably get it as a Kit, there is also a water spray controller if you really want to go large.

I’m a NA fan so haven’t done much work on turbo cars but for a modified road car the Unichip is as good as anything out there. Remember the mapping will have to be by someone who actually knows what he is doing. You can leave the settings totally standard and only adjust fuel & timing where it needs changes, for example when on full boost or when Nitrous is being injected.

The mapping software is pretty simple as its still DOS based but it all seems to function well and is easy to understand. I do my own mapping as I have the use of a Dastek load dyno which makes my life really easy as the load sites are pre-programed into the Dyno software.

I will be replacing my Unichip hopefully in the not to distant future with a new version that also controls the VVT maps, the current version can control V-TEC but doesn’t control Variable timing yet... can't wait.
 

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Discussion Starter #9
unfortunately the unichip is not available here in the US.......the SAFC is just as good basically.

however, my customer in the UK is using a unichip on the turbo kit I sold him :)
 

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will the hotshot header fit on an 05? I was under the impression it was the same engine 2000-05 but on hotshot web site it says its made for 2000-03.
 

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Hey, Chimmike, have you done a quarter mile run on your car? if so, what kinda time do you get?

I have one of these and i never knew it had such potential. Keep up the good work.
 

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Discussion Starter #15
no recent 1/4 mile trip with the clutch and flywheel yet, but it's a 14 second car, easily.
 

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I just thought I would give a heads up as to what I’ve been up to down here in sunny South Africa. As it turns out there are two types of QG18 engines here in SA, one is a UK spec Hatchback with NVTC (Nissan Variable Valve Timing) & an SA spec sedan with no NVTC, for info the current Australian Pulsar N16’s have NVTC as well as Fly By Wire Throttle. For a small country the aftermarket car scene is pretty big, not comparable to the US but not bad. The Nissan’s that rule the roost down here are the old SR20DE powered 200Sti’s (similar to the N14 Pulsar SSS) and SR20DET powered S14 200SX Coupes (Silvia’s). There is little or no interest in the Almera N16/B15 generation of cars, there are loads of them around but they have about nil street credentials as all the rental companies use them & most of them are QG16DE’s anyway. For the price its 118hp doesn’t really compare to the slightly more expensive options available here such as the Toyota RunX 1.8 Rsi (195hp), 206 2.0 Gti180 (180hp), Renault Clio 2.0 Sport (177hp) and Ford Focus 2.0 ST170 (170hp).

To try & keep up I have re-profiled the cams in my QG18DE Almera sedan. The profile is pretty mild and works well from low revs all the way to red line even though my engine doesn’t have NVTC. The profile is similer to a Schrick 250 profile but has a slightly smaller base circle. It was developed on a non NVTC engine so a much wilder cam can be run in a NVTC engine so there will generally be more gains. So far I haven’t had any wear issues on the cams, they were just reground & we found there was no reason to nitride them, as the hardening was deep enough.

The power measured on my standard 04 Almera was 61wkw (82whp) at 6100rpm. With custom branches (headers), a wet panel filter (locally made similar to K&N) & 57mm (2.25") mandrel bent exhaust & a Unichip piggy back ecu that went to 69wkw (92.8whp) at the same revs. Then with a mildly flowed head & re-profiled cams it went to 79wkw(106whp) @ 6500rpm. The figures may seem low but it was tested at high altitude as Johannesburg is almost 1830m (6,000 ft) above sea level & on average we have at least an 18% loss of power compared to figures achieved at the coast so theoretically the car should produce 93wkw (125whp) or almost 130kw (175hp) at the flywheel when tested at the coast. This is comparable to a standard SR20DE powered Sentra Sti which makes on average 73wkw at altitude & 86wkw at the coast (its rated at 105kw at the flywheel). So far my set-up has cost me about 1500US$, damn.

Obviously the cams weren't the only gain as the head was flowed as well but the car doesn't have a CAI, which would increase power further, but in general there could possibly be a gain of more than 10whp with a decent cam for the US cars if JWT do produce them. My engine currently has a very good torque curve pulling strongly from 3000rpm all the way to redline, my ECU is modified & currently I have the piggyback ECU controlling the rev limit still set at 6500rpm. If & when I get brave I’ll let it rev a bit more as the power is still climbing at max revs, from the power curve it could peak at about 7000 which could be worth about 5kw (7hp).

Possible future modifications include a custom centrifugal supercharger with an Intercooler that’s why I haven’t fitted a CAI yet; I don’t mind turbo’s but due to our hot, dry & thin air turbo’s spin a lot faster than at the coast to get to the same boost so reliability may be an issue, the best part about forced induction is there is very little power loss compared to the coast so boosted cars rule up here. Are any of you living in high altitude area’s & if so how has your reliability been with a Turbo. I know I need FI, I need to get into the 14’0s, my car is currently scratching to get into the 16’s. BTW as a comparison I went to the track this weekend & at this altitude the quarter mile for a standard Golf 5 GTI was 15.5s, a 350Z on street rubber was 15.0s, two BMW M3 CSL’s ran 14.4’s & 3 Vortech supercharged Z’s ran 14.0s, a 550hp GTR34 ran 12.8s & a Noble M12 ran 12.2s. A bit of boost goes a long way.
 

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Discussion Starter #17
sounds good race. You might want to try porting the intake manifold or having it extrude honed, as that will help. Remember though that you will need the unichip retuned to add additional fuel to compensate for the larger amount of airflow let in the engine.

a header should help you as well.
 

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Service Manual

chimmike said:
QG18DE Naturally Aspirated Tuning:

Hey , good day,

I am deotrish & I have a 1999 Primera with a QG18 engine.

Do you know where I can find a service manual for my car?
 

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Discussion Starter #19
I don't know of any sources for a Primera FSM. try www.phatg20.net and see if they have an Almera one for the n16 Almera...which shares engines with us.
 

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i was wondering if i was to remove my stock springs and i cut them would that work. i work with metal so i would be able to cut it. its just a question!!! give me sum feed back.
 
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