Had my new SE SC not quite a week yet, pretty cool little truck. But I don't have a handle on the supercharger yet. Questions:

1. Does SC spin all the time or only on demand?
2. Is there a bypass?
3. When bypass & when SC? Vacuum demand? RPM?
4. Can I improve gas mileage?
5. Free-breather air cleaner/exhaust a good idea?
6. Any good tech articles out there?

Thanks!

- Tim

It is very simple:

The SC only kicks in when you press the gas petal to the floor due to a waste gate on the SC triggered by petal postion. This is why I did not buy one, it is crap. I waiting for an after market system that will take full advantage of a SC. I mean 5-7lbs boost only at wide open throtal??? Every other SC vehical I have ever seen uses the SC all the time and has a timed blow off valve for the shifts so you dont tear up the tranny.

The stupid thing is when I e-mailed Nissan their reson for this setup was to save gas and wear on the tranny. Ok lets think about this, in order to get the extra power from the SC you have to floor the truck..hmmm...

1-Wide open throtle=more gas (so much for millege)
2-Wide open thortle=Hard Down Shift with a boost
of 40 HP at the same time (so much for tranny
wear)

I love Nissan but they did not do their homework on their setup. I have a few friends with after market SC's on thier trucks (not Xterras) that run with the proper set up and have had no problems with their trucks...

When an after market SC does come out the truck will need an A.F.C. in it to get the air/fuel mix right.

Flowers have "petals".
Trucks have "pedals".

There isn't a real way to get better gas mileage with the SC. I guess if you just babied it you would get maybe better.

AN intake and exhaust will certainly help it breathe easier at the cost of your economy. We have an SC forum on our site that has some info in it even though most of it seems to be centered around intakes and exhausts since those are the most likely and cheap mods. There are also some smaller pulleys out there that bring your boost level up to about 10psi.

Xterra type-r I seem to have boost at different pedal levels and not when I mat it. My boost gauge shows me this. I think you are thinking of tubos that have blow off valves for shifting. SCs are different. They are alswys on and there is less lag. They also tend to be more reliable. I am sure too that the 40 HP isn't an instant on thing, it is gradual across the power band.

I think Nissan did do thier work. They went to Eaton, they boosed the injectors and strengthened things inside as well. Try to get 40HP another way right now and not spend the $1,500 that you would for the option from Nissan.

I know some have "answered" but here's specifics

The SC is always spinning, always compressing air (no clutch on the SC pulley or drive pulley). This is the main reason for poor fuel economy.

There is a bypass valve on the SC, it sees it's vacuum signal from a computer contoled solenoid.

Bypass is closed as engine vacuum drops. Typically it takes +/- 50% throttle to get any boost.

Don't we all wish The best way to improve mileage is to putt-putt, as the parasitic drag to run the blower all of the time will never allow the engine to reach fuel consumption rates of the NA engines. A combination boost/vacuum gauge is effective in showing when you are in boost (poor fuel mileage) and high vacuum (good fuel mileage)

Better for power, not necessarily better on fuel consumption, as the blower draws enough intake vacuum that a less restrictive intake will not help fuel mileage.

Haven't found any yet, however I have figured out how to bypass the computer solenoid - to the loss of some fuel economy though, but a slight gain in boost level and performance.

Actually, the SC doesn't have much drag when it's on bypass. Since it's not a positive displacement unit, it doesn't compress the air as it goes through the unit. It's nothing more than a fan really. It creates pressure by simply cramming air into the intake manifold. Most of the drag comes from pushing against the pressure in the manifold, the actual "work" it does, not from mechanical drag. I'll bet you could spin the lobes by hand with little effort. When it's running on bypass, it's like a fan running in a vacuum and not having to push against anything, therefore not sucking more than a negligible amount of power.

Brent

XterraType-R...what the hell are you ? Man is that some bullshit info!!! If you don't own it and don't know...shut up!!! The SC definately gives boost under mild acceleration (NOT FLOORED) hence the humming under the hood and being pressed back into the seat!

Actually, he's right. The supercharger only operates at full throttle according to a few things I've read. That noise is just the drive belt and the pulley, so of course you hear it all the time. It's always spinning.

This is from: NISSAN

Xterra’s supercharger is designed to operate under “boost” conditions (6 to 7 psi) under wide open throttle conditions (WOT) – which during typical driving is only five to ten percent of the time. Fuel pump flow rate has been increased and fuel injectors have been enlarged by 80 percent for supercharged models to handle the extra fuel needs under boost.

During normal driving, a bypass valve (a solenoid operated vacuum valve controlled by the Xterra’s electronic control module) diverts the excess air back into the supercharger inlet where it is recirculated, with the engine operating like a naturally aspirated Xterra V6. This helps maintain good overall fuel economy with power on demand.

That is "max" boost under WOT. The SC gives less boost under less aggresive acceleration. My Mom and several friends have non-SC 02's and one 03 all of which I have driven often. They have do not have the same torque feel (push in the small of your back) when accelerating 1/2 or 3/4 throttle. The boost is spread out across the rpm's with max boost only under WOT. If boost came on only under WOT then it would feel like a shot of NOS!!!! Trust me...you can feel the boost under less than WOT conditions. GO DRIVE ONE! Then come back and say..."err-ahh....SORRY"!!!

Can you post some proof? It sounds like you're making shit up in spite of the fact that I just posted something from Nissan to the contrary. And please explain this scientific method you used to compare an SC and a non SC at part throttle. Did you set up a ruler on the floor to measure exactly where 1/4 and 1/2 throttle are on both trucks? No, I didn't think so.

BTW, I have driven an SC, and if I had it to do over again I still wouldn't get one.

Here's why: Frontier Test

What is strange is just how urgently the supercharged Nissan leaps off the line with nothing more than a tap of the gas pedal, belying the mediocre drag-strip numbers. It turns out that an overly aggressive throttle linkage disproportionately opens the throttle plate when the pedal is depressed. Pure mechanical trickery, but the supercharged Frontier now easily merges into 80-mph freeway traffic.

Actually Brent you shouldhave consulted yourself before posting this.

It is a compressor, not a blower (A blower is only positive displacement). Look at the rotors (screw type)= compressor, (rotor type)= blower.

Yes you can turn it easily with your hand, but if you had a hand crank that was geared to allow you spin the SC up to compressor speed you would feel the drag of the compressing air. If you want even remove it and the manifold from the engine, and do it on the bench, it will still require force. It works the same with a turbo...you can spin it by hand...

I wasn't speaking of mechanical drag, but the force required to compress the air.

But don't take my word for it! If you get a chance to drive an SC with a boost/vacuum gauge you will see "0" vacuum at or about 1/2 throttle, whereas it takes full throttle on an NA engine to meet the same low vacuum. Cruising at 70 in an NA X should pull about 15" Hg, same in the SC is 0" Hg.

Poorer fuel consumption due to less intake vacuum, less intake vacuum due to higher engine load, higher engine load due to blower.

It does produce boost at less than full throttle. if you have a boost/vacuum gauge you can see this.

If you read that quote from Nissan, it is speaking of full boost at full throttle. And even at full throttle the boost level is not consistent - WOT at 2500 rpm only gets 5 psi.

As I stated in an earlier post, my boost gauge reads boost at throttle positions other thatn WOT. The article/literature you cited says that the boost of 6-7 psi (which is the peak) is reached at WOT which in reality isn't all the time. However even when I am not mashing the pedal to the floor but accelerating strongly (let's say 3/4 throttle) I still see boost on my guage at around 3-4psi. I guess I am full of shit...

OK, maybe I got my terms mixed up, it is positive displacement, but I was right about it's design. The SC on the Xterra does not compress the air on its own, it should not offer much resistance. At most it deals with the air drag as it rotates through it at lower RPM, but it's not having to fight pressure on the outlet side to get more air in until the bypass valve closes.

Brent

ILUVMYX......Who's your daddy? I got your scientific test right here. :p Take your ruler and measure how far you can stick it!!! BIG THANKS to Pacopico & AG Bullet, I knew some SC owners would wake up and get my back. Its not that hard to tell when the truck is getting extra push because of "part throttle" boost! Thank-you guys!!!

OK, let's try again. Another source... CLICK

The Eaton supercharger operates only under wide-open throttle conditions (WOT), providing 6 to 7 psi of boost. Fuel pump flow rate has been increased and fuel injectors have been enlarged by 80 percent for SC models to handle the extra fuel needs under boost.

Somehow that's exactly the proof I was expecting.

ILUVMYX....you look to a Canadian for proof? Get over it!!! YOU ARE WRONG!!! Ag Bullet's gauge shows boost at 3/4 throttle! How much more proof do you need? HOW ABOUT THIS...2003 Dealer Only Product Guide, page 13: "key benefits of the SC include immediate throttle response...across the complete engine operating range. The SC provides additional boost at all engine speeds." Maybe you should spend your time more wisely, say shouldn't you be checking your tire pressure or something? Oh shit I forgot, you drove one once...you're a friggin' SC expert!!!

Read it again. Where exactly does it mention throttle position? Immediate throttle response... complete operating range... all engine speeds... they're talking about the advantages of a supercharger over a turbo. Please, try again to post the part about throttle position. Good luck.

I have said all I need to say on this. The rest of my feelings are summed up in my sig file. Feel free to fly your ass here drive my truck and watch my boost gauge at different throttle positions...

As for the throttle position, what does immediate throttle response to you mean? To me (and maybe I am wrong here) it means that when you step on it that boost is beginning to be generated. At lower throttle positions (let's just say half way for the sake of this "argument") it is dumped or recirculated. After that, the bypass opens or does whatever it is it does and the boost begins to be used. On my gauge, the truck is no longer in a vacuum and the psi's begin to show on the SC side. It really is hard to dicern without a guage if you are going at it slow and steady. There is a whine but in the stock set up it is kind of muted until WOT. With an intake you can hear the SC turning (whining) at lower speeds/throttle positions. Go test drive one again with the windows down and the radio off and tell the salesman to shut up and listen. You will also notice a pep that by doing the same thing in a NA truck won't be there.

If none of this will convince you I say to heck with it beleive what you want the rest of us have tried to help...

I don't care what they say - I own one, and at least one owner has reported real world results via a boost guage - I didn't see your linked article backing up their statement with any kind of imperical measurements either, but rather the parroting of Nissan sales literature (and we know just how knowledgeable those marketing types can be - experts in every field, those guys!)

And after driving around an NA X for several weeks, and after having owned an SC X for several weeks - I can emphatically state you are full of it and should try driving one for more than 20 miles. You do not have to mash the petal to the floor to tell that there is an immediate and positive benifit to the SC.

Actually, I don't know why I am bothering responding to you - you have already stated your mind is closed, and I have already voted with my hard earned $$$ and bought the SC.

Oh that's right, someone new to the site might read this thread and think you know what you are talking about :rolleyes:

You are wrong. Immediate throttle response is mentioned because it's an advantage compared to turbocharged engines. It means the boost is instant the second you floor it. A turbo does not provide immediate throttle response--it requires time to "wind up" before it starts giving boost. There is no "wind up" with a supercharger because it is mechanically driven from the engine as opposed to exhaust gas driven in the case of a turbo. Also, a turbo is rather worthless at lower RPMs whereas a supercharger, again, because it's mechanically driven works across all engine RPMs.

Just because your boost gauge is giving you a reading doesn't mean the engine is seeing that boost. The supercharger may be generating pressure, but the bypass isn't sending that pressure to the engine. It only tells you that there is boost. It doesn't say where the pressure is going. The only way to know for sure is to have a way to monitor the bypass to see where the boost is going.

I bet you have a tornado in your X too don't you....

Okay ILUV, how about this. I am friends with Jeb (Ag Bullet), and have seen his truck run many times. I have witnessed the boost gauge. It is hooked into the vacuum system on the engine. If you don't know how that works, the engine vacuum is generated in the intake manifold, INBETWEEN the SC and the engine block. The gauge monitors EXACTLY what the engine "sees", to use your terminology.

Hey Jeb, this guy reminds me of another one over on TUNFS. You think they're related?

Coming from a guy who has a 3" lift, lockers, engine swap, revolvers, skid plates, and a "4x4 conversion" planned for his 2WD truck... well, it just doesn't bother me much. So how is that "4x4 conversion" going?