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Discussion Starter #1
As some of you know, I have been recently experiencing major power loss with my S/C Fronty (please refer to my threads)
Today, I took a ride with a Nissan Master tech, and analyzed my truck in "real time" on a test drive. Here is the conclusion.....the power loss was directly due to the knock sensor relocation. The knock sensor was picking up noise from the supercharger, it was working correctly because it was seriously retarding my timing. I disconnected the relocated KS and the truck ran well, but not to my satisfaction. They took my truck into the shop and physically advanced the timing.........with the KS disconnected, and the timing advanced........the truck runs great. With the KS disconnected, it is NOT bypassing the S/C, or putting the truck into "fail safe mode", from what I've experienced it seems to be more of an urban myth. So....if I had to do it again, this is the route I would have gone, screw the relocated KS, I wasted $160 doing the mod. If you have a S/C installed on your truck, I highly recommend to forget about the KS relocation mod, run premium fuel, and advance your timing. The tech did say, that in 20 years he's never seen someone do this, and gave me an A for creativity. :)
 

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Ok, so I can understand that the KS could pick up noise off the supercharger.

So what were your timing settings before and after? I think 10 is normal 12 is max and 8 is min.

With an unhooked or failed KS you put the truck into fail safe where the ECU will not advance the timing based on knock. So what you did was just physically advance the timing.

What I do not understand is why the truck looses boost with a failed KS? Once a good KS is hooked up boost is back.

Failsafe is not an urban legend it's in the Factory Service Manual. But what I don't get is when oringal timing and a good SC you get boost. Original timing and bad KS you loose boost. Bump up the timing and your boost is back?

So what this would mean is that you could physically advance the timing on the engine and a good KS could monitor it. Maybe for us non SC guys this is good and the relocation would make it that much better.
 

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Discussion Starter #3
Ok, so I can understand that the KS could pick up noise of the supercharger.

So what were your timing settings before and after? I think 10 is normal 12 is max and 8 is min.

With an unhooked or failed KS you put the truck into fail safe where the ECU will not advance the timing based on knock. So what you did was just physically advance the timing yourself.

What I do not understand is why the truck looses boost with a failed KS? Once a good KS is hooked up boost is back.

So what this would mean is that you could physcially adanvce the timing on the engine and a good KS could monitor it. Maybe for us non SC guys this is good and the relocation would make it that much better.
YES! The KS can pick up the noise from the S/C, anywhere on the intake manifold, including my re-location. I have taken the KS monitoring system out of the equation, and have manually advanced the timing, to what degree I'm not sure, the dealer handled it, so if it changes, I can return there and they can fix it. It doesn't loose boost with a failed KS, and I think the information about the bypass valve on the S/C floating out there, is a$$ backwards. 9 O'clock = closed, 12 O'clock open, that's how I see it. I have physically seen the bypass valve, due to changing the S/C several times and this configuration is the most logical. The only job of the KS is, if it detects knocks or pings, adjust the timing accordingly, otherwise it doesn't do squat, and if you are using good fuel, pings or knocks are not going to be a problem, I've already noticed an improvement in gas mileage, going from 1mpg to 10mph, LOL! This is my theory, and I'm sticking to it, I have witnessed the improvements first hand, and an absent KS is better than a good one that you can't get to work right.
 

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This is from the Factory Service Manual. The ECM will advacne the timing when you have a good KS. When the KS detects ping then the ECM will adjust timing as needed.

KS does serve a purpose. Maybe for the SC guys the KS on SC doesn't work as good as thought.

I am curious to see if your ECM is throwing the KS code. Could you check with a code puller somehow?
 

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Discussion Starter #5
This is from the Factory Service Manual. The ECM will advacne the timing when you have a good KS. When the KS detects ping then the ECM will adjust timing as needed.

KS does serve a purpose. Maybe for the SC guys the KS on SC doesn't work as good as thought.

I am curious to see if your ECM is throwing the KS code. Could you check with a code puller somehow?
My timing is advanced manually, my knock sensor is out of the loop and not connected, I run premium fuel always, my truck is running strong, accelerating great, I am throwing a KS code, I'm not throwing a service engine light, and I've had it with the knock sensor. My advice for what it's worth after my experience, for the S/C guys, FORGET about the knock sensor, go to the dealer, or not, and advance the timing on your truck manually. For $99, I would have saved myself a ton of aggravation over the past 2 and a half weeks.
 

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I wonder what will happen to the SC guys that tow? If they are already running premium and are towing a 5k trailer, will they get knocking? and since the KS has been removed, will the motor know to retard the timing or will it just let the motor self-destruct?
 

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from what i read on the forums and on the internet about the vg33er is that it is very heavily knock sensor dependent so i don't see why, if relocating failed (i do understand why u would want to relocate) why not just just place it back in the stock location. especially since running premium i noticed it is about 3 to 4 dollars more each fill up . like for me i fill up every 6 days. so by the end of the month i wasted a tank full of gas money. and this is just for the s/c guys right? cuz i about the relocate to my vg33e
 

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Discussion Starter #8
from what i read on the forums and on the internet about the vg33er is that it is very heavily knock sensor dependent so i don't see why, if relocating failed (i do understand why u would want to relocate) why not just just place it back in the stock location. especially since running premium i noticed it is about 3 to 4 dollars more each fill up . like for me i fill up every 6 days. so by the end of the month i wasted a tank full of gas money. and this is just for the s/c guys right? cuz i about the relocate to my vg33e
From everything I've heard, with my own ears, the VG33ER is a bomb proof platform. To replace it in the stock location is $1000.00. Part cost $135.00. I will report back when I get a better idea of gas mileage, but running around today, I saw a solid 16mpg, with performance. I pull a motorcycle trailer with my truck, probably in the neighborhood of 2200lbs loaded, we shall see if my engine implodes. I've had it with this truck anyway, I'm working a deal for a 2010 Tundra TRD. :nana:
 

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Well I guess I wasted my time if I listen to GothamEMS. I just got done relocating my KS today just how he says do it. I do believe my KS relocate is an improvement from what it was doing. It feels much stronger. I don't know who to listen to on this post but I do agree with joefrontier2 too. If its not throwing a code then it seems to be doing something right. I am not a mechanic at all. So with that being said I have no idea what is the best thing to do. My gas mileage seems to be the same as it was before the relocate. I only drove about 50 miles but it still drank a quarter of a tank. (yea that's not good) And 45 of that is highway at 60 mph. I wish I knew then what I knew now I would have met the prev. owner and laughed and pointed at him and kept my 1995 Nissan extended cab 2.4 4x4.

I guess my question to joefrontier2 is, Is there another location that you can think of that the KS can be located at. I know you don't have a supercharger but is the rear of the S/C the best place. I had it on the side at first but then moved it due to others placing theirs there. Would it mount somewhere under the S/C or would it be better to make a bracket to bolt it to that would get it away from the S/C where it wouldn't pick the noise from it. In my opinion if it picks up noise from the S/C and retards the timing then it should be throwing a code. Mine does not. No KS codes. No code is a good code.
 

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Discussion Starter #10 (Edited)
Well I guess I wasted my time if I listen to GothamEMS. I just got done relocating my KS today just how he says do it. I do believe my KS relocate is an improvement from what it was doing. It feels much stronger. I don't know who to listen to on this post but I do agree with joefrontier2 too. If its not throwing a code then it seems to be doing something right. I am not a mechanic at all. So with that being said I have no idea what is the best thing to do. My gas mileage seems to be the same as it was before the relocate. I only drove about 50 miles but it still drank a quarter of a tank. (yea that's not good) And 45 of that is highway at 60 mph. I wish I knew then what I knew now I would have met the prev. owner and laughed and pointed at him and kept my 1995 Nissan extended cab 2.4 4x4.
Listen, I just posted "my" experience with the knock sensor relocation on a supercharged truck. I feel as though my "how to" could help others, as others have helped me, BUT it didn't work out for me. My truck wasnt throwing a code, or a light, and the timing was screwed from the KS relocation, as a matter of fact it retarted the crap out if the timing at about 1500-1800rpms. Listen to who you want, and do what is besgt for you, that is another lessen I learned through all of this.
I am very, very curious, how this knock sensor relocation mod worked with other supercharged owners, so if you own a S/C, and did the KS relocation, please share your experience so we can get a better idea of what is going on with these things....for me, with the timing advance......waste of time and money, so it is throwing a code, big deal, no SEL to annoy me on the dash, and I won't have a problem with an inspection, I can live with that, I'm already seeing fuel mileage improvement with the timing adjustment.
 

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Ok if mine starts acting up and my gas mileage stays bad and I go to my local nissan dealership. What do i tell the tech that I want done? My timing jumped up some? How much? And you say manually. Explain that. Thanks, I'm all ears here, I just want whats the best for my truck and my gas mileage. Also my truck has 118,000 miles on it too.
 

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I do not know where a better place to place the KS on a SC would be. On top the motor is the best place but it's a long ways to get there.

fifty9singlecab - I'd say wait to do this till we get some SC guys in here. I am just curious to know what others say.
 

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Hi All,

Well, with me being the new kid on the block (I've had my S/C for a week), I don't know what to do now. My truck passed emissions no problem. Drove it home from where I bought it (200 miles away), no problems and good power but it did suck gas as bad as my Chevy 350 V8! The next day I started get the 'spoons in a blender' rattle REAL BAD and got a KS code with my OBDII scanner.

I started scouring the forums for a fix and heard from most that it is probably a bad KS sensor and so I was considering doing the KS relocate/replacement.

Now, I notice that the BAV valve is suddenly sitting a 12 o'clock like it should and not bypassing (down on the stop). I still get some rattling but not as bad as before.....but how long before it returns? What is going on here! I love this truck but I am already getting despair and am worried I am going to have to spend a fortune on this... I bought it to just drive not fix all the time...

Help! :)

Tim
 

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Knock sensor relocation

I have a 2003 S/C. I have now replaced my knock sensor twice. The first time was at 29500 and the second at 46500. I have a mechanic who thought he didn't quite believe that the relocation was the right thing to do. He replaced both of mine to the stock location.(He is NOT a Nissan mechanic) He charges me $250 per replacement. The other cost is a sensor at $115. I am not sure what I will do next time(hopefully no next time!). I know when the sensor is out, the truck definitely runs poorly with lower mpg.'s. I am now averaging 17.5mpg's with a good sensor and was only getting about 16mpg.'s with the bad ones. I am anxiously waiting to see what the forum brings about in answers.
 

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Thanks joefrontier2, I am going to wait. I haven't got anything to loose. But alot to gain. I have a daily driver 59 Single Cab VW Truck that makes me happy in the spring, summer and fall. If it had heat the winter would also be great.
 

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Discussion Starter #16 (Edited)
Hi All,

Well, with me being the new kid on the block (I've had my S/C for a week), I don't know what to do now. My truck passed emissions no problem. Drove it home from where I bought it (200 miles away), no problems and good power but it did suck gas as bad as my Chevy 350 V8! The next day I started get the 'spoons in a blender' rattle REAL BAD and got a KS code with my OBDII scanner.

I started scouring the forums for a fix and heard from most that it is probably a bad KS sensor and so I was considering doing the KS relocate/replacement.

Now, I notice that the BAV valve is suddenly sitting a 12 o'clock like it should and not bypassing (down on the stop). I still get some rattling but not as bad as before.....but how long before it returns? What is going on here! I love this truck but I am already getting despair and am worried I am going to have to spend a fortune on this... I bought it to just drive not fix all the time...

Help! :)

Tim
The whole 12 O'clock position of the bypass valve equals closed, strikes me as backwards as well. I've replaced my supercharger several times, long story, and when you actually see the butterfly bypass valve in the 9 O'clock position, it is closed. So I firmly believe after inspecting the supercharger, several times, off the truck, 9 O'clock looks closed and 12 O'clock looks pretty open. The air comes into the throttle body, into the S/C, and with the valve at 9 O'clock, it's diverted to the roots, when the valve is at 12 O'clock, the roots are bypassed, passing air into the lower intake manifold. Everyone who has a S/C and a bad knock sensor, needs to visit their local dealer and have the truck analyzed in real time, while driving, with a Nissan tech who can see in, real time, what the hell is going on with the timing of these trucks, bottom line. I just went through this BS today after my truck running like crap for 2 weeks, becoming worse as time went by.

The S/C we have in our trucks are Eaton M62, here is a link, look at the bypass valve located on this page, this is exactly what our bypass valve looks like, it is in the 12 O'clock position in the picture, and is open.CAD


Here is a pic of two superchargers, the one on the left looks like an Eaton, the one on the right looks like a Whipple. Notice the bypass butterfly valve located at the rear of the charger on both units, they are closed. In relation to our configurations, closed is with the valve lever at 9 O'clock.
http://www.vmptuning.com/GT500/TVS/tvsbottom.jpg

Here is another pic of an M62, look at the position of the bypass valve, and the extension of the BVA arm, closed, 9 O'clock. This is the exact supercharger on the 2001 - 2004 Nissan Frontier
http://www.explorerforum.com/forums/attachment.php?attachmentid=51167&stc=1&d=1224029298

This should clear up any doubts reguarding the bypass valve, please view, it is an Eaton blower:
YouTube - Eaton Gen6 blower

So in closing, I believe that there may be some misinformation regarding knock sensor relocation mods on a S/C Frontier, and am just sharing my experience so that others may save a lot of time and money.
 

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Ok now if you are wrong, not at all saying that you are but if so looking at this M62 cutaway picture it appears to me that a better place for the relocate would be in the middle just because it appears that it will get less noise there being away from the valve and clicking noises. Just a thought. What do the rest of you think?
 

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Discussion Starter #18 (Edited)
Ok now if you are wrong, not at all saying that you are but if so looking at this M62 cutaway picture it appears to me that a better place for the relocate would be in the middle just because it appears that it will get less noise there being away from the valve and clicking noises. Just a thought. What do the rest of you think?
Bottom line, the rear bolt is the farthest point from any moving part that would be responsible for any significant noise in the supercharger. The roots would make far more noise than the bypass valve, just look at the distance from the rear of the roots, where the needle bearings are in the housing, and the rear mounting hole I chose for the relocation, there is alot of real estate there. And it works on the same principal as the KS relocation mod, any noise is going to sucessfully travel through metal to metal contact thoughout the intake. Give it a try and post your results....I would be curious, but I won't do it with my truck.
 

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Hey GothamEMS,

I just checked out your Youtube video and that's it! That's the same rattling that I get on my SC, but mine I think quite a bit worse.... it sounds real loose.

In your opinion, do you really think that it is not the SC itself? I think that you said that before but now I am just totally confused as to what to do or what road to take. Although I am starting to think that it might cost less to fix if it WAS the SC...

Argggh!
Tim
 

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Discussion Starter #20
Hey GothamEMS,

I just checked out your Youtube video and that's it! That's the same rattling that I get on my SC, but mine I think quite a bit worse.... it sounds real loose.

In your opinion, do you really think that it is not the SC itself? I think that you said that before but now I am just totally confused as to what to do or what road to take. Although I am starting to think that it might cost less to fix if it WAS the SC...

Argggh!
Tim
The S/C in the video is a rebuilt one. The bearings were screwed originally and I had to replace it. The video was taken so the company I purchased the rebuilt one from could see there was something wrong with the one they sent me. They sent me another one because the warranty was 3 years unlimited mileage, and it's much better. Here is the misconception regarding "bypass mode", "fail safe mode" or any other mode they're calling it now a days....at idle, you are not producing boost, the bypass valve is open, and the air is being recirculated in the intake. When you recirculate the air in the intake you will hear this rattling noise, turbulance, with variations to a degree from truck to truck regarding noise volume. When you accelerate the bypass valve closes, producing your boost, and no air recirculation. You may just have a bad couple which will cause play in the S/C. The only way to see if the coupler is gone, is pull off the belt, if there is play when you move the pulley side to side, you may have to replace it (coupler), $35 part on eBay, easy fix. The coupler is a plastic small hockey puck looking thing that connects your drive shaft from the pulley to the root gears. Because they are plastic and in an oil filled chamber they tend to break down, and the holes which connect the drive shaft to the gears become elongated, egg shaped, causing play.
 
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