[ezcheese15]

Ok, for those of you on the se-r mailing list, you already know the story. But here it is again, with an update:

Last weekend I installed a Hotshot Header on my spec V. So I took it to a dyno on Thursday to see my gains. What happened was shocking. I dyno'd 145.9 HP and 154.9 lb-ft of torque. That is with a JWT pop, VRS exhaust, Hotshot Header, and removed balance shafts.

The really bad thing was that the dyno place layed that graph on top of my last dyno run. My last dyno run was with a JWT pop and VRS exhaust. On that run, I put down 148.2 HP and 158.1 lb-ft. So with the removed balance shafts and header, I LOST HP and torque. Something is definatly wrong.

I think something has been getting worse and worse since I've had the car. My original dyno run when stock was 143.3 HP and 155.6 lb-ft of torque. So my initial gains from intake and exhaust weren't that big, but I didn't think it was too bad. But now, with the current mods, it's obvious something is wrong.

My theory was that the fuel pressure regulator was bad. So today I went to check the fuel pressure. So my first question is, does anybody know how in the hell to disconnect the fuel line from the fuel rail? It has some type of weird clip that, according to the service manual, requires some special dealer tool to remove. Well, I hate dealer tools, so is there any other way to get it off?

Because I couldn't get the fuel line off to check the pressure, I decided I would try a different method. My brother also owns a spec V, so I swapped fuel pump assemblies with him. That includes the pump, fuel filter, and fuel pressure regulator. I was praying that my car would feel much quicker, thinking this would be the problem. Well, it didn't make a difference. And it didn't make my brother's car feel any slower either So now I don't know what to do.

I'm looking for suggestions on what else to try. Some things to note are the following:

Since about March I have been experiencing problems when starting. The car cranks excessivly when starting some times. Almost as if the fuel line is not pressurized. I do not know if swapping the fuel pump assembly changes this, as it has only been swapped for about 2 hours. I will find out later this week.

I have also been trying to install an RPM switch to change the opening time of the intake runners. This switch was not in my car last time I dyno'd, but it was this time. The way I have it hooked up is it is spliced into the main power, ground, and crank pos sensor wires going into the ECU. The VIAS wire between the ECU and the VIAS solenoid is cut, and the switch wire from the RPM switch is connected to the VIAS wire on the solenoid side.

The O2 sensor has been relocated to after the secondary cat. I have no MIL codes.

Also, a glasspack was added between the downstream O2 sensor (now located after the secondary cat) and the muffler to make the car quieter. The glasspack is straight through.

Those are the absolute ONLY things I can think of that have changed on my car. If anybody has *any* suggestions at all of what to try next, please let me know.

 

[cortrim1]

knock sensor

torry see if you can get a dealership to use the tecII to look for knock sensor activity. I would say with all of the things you have done have created more noise and vibration for the knock sensor to pick up. If you find that the knock sensor is ok then I am stumped but I can let you know if I have the same problem. I am going to the dyno next saturday I have the same mods as you except the balance shaft removal I will let you know how it goes also I will have two other spec v there to compare numbers against.


mike

 

[cortrim1]

pocket logger

torry if you have access to a pocket logger you can find out about your timing and if your knock sensor is causing the problem. If your knock sensor is causing a problem your timing advance will most likey be a negstive number a t high rpms or not advanced very much.

 

[BlackoutSpecV]

with my limited Nissan knowledge I'm thinking Knock Sensor. Best bet is to try to get it hooked up to an engine dignostic computer. Please post a reply when you findout your problem, i'm curious to see what it is.

 

[ezcheese15]

Re: pocket logger

torry if you have access to a pocket logger you can find out about your timing and if your knock sensor is causing the problem. If your knock sensor is causing a problem your timing advance will most likey be a negstive number a t high rpms or not advanced very much.

I don't have a scan tool of my own, so I will have to find somebody with one. I do have one theory right now though that has nothing to do with the knock sensor. It has to do with the ECU and the RPM switch I installed. I will try my theory first, then if that doesn't work I will try to source a scan tool to check my timing under load.

 

[cortrim1]

pocket logger

I am going to the dyno on saturday and I will have 4 spec v with me I am going to use the pocket logger on all of the cars so I can monitor the rpm related to the timing advance so I will let you know how it works.

 

[BlackoutSpecV]

saw this in looking for something else on b15 site...

http://www.b15sentra.net/forums/showthread.php?threadid=31136

relates to this topic

 

[ezcheese15]

Ok, so here’s the latest update:



First of all, my car is now working properly. I haven’t dyno’d it again yet, but you can really feel a huge difference. Here’s what it was:



It was a combination of two problems. The first one deals with the RPM switch that I installed. Let me explain the switch. It has a red wire for power, black for ground, white for RPM signal, and then two switch wires; one grey and one yellow.



The switch has dip switch settings to select the RPM that you want it to activate. The yellow wire is normally dead, and at the given RPM, it supplies 12 V of power. The grey wire works opposite, where it normally supplies 12 V, then goes dead at the given RPM. This is so you can use either wire, to turn whatever on or off at the RPM. Well, the intake runners on the QR switch when power is cut to them. So I used the grey wire. Well, turns out, the runners were switch backwards. So the secondaries were open at low end, then closed up top. Double bad. So I figured the directions were printed wrong, so I switched the grey wire and yellow wire. When I tested it again, the runners did not switch at all. When I measured the voltage, it turned out the yellow wire supplied 12 V below the given RPM, and 9 V above it. So it turned out to be useless. I disconnected the switch and wired the intake runners back up like they were stock, switching at 5k rpm.



So that solved one problem, but I knew that wasn’t it. It still didn’t feel that much better (torque felt better, but HP just wasn’t there). So I tried what Kojima and a few others had mentioned to me…removing the knock sensor and tieing it away from the block. So I unbolted the knock sensor, ziptied it to the firewall, then grounded it to the block. Sure enough, that was the answer! The car now feels incredibly quick compared to before. I am guessing a 15-20 HP increase at the ground.



So now I’m a happy camper. However, I still am going to wait on re-dynoing it. I want to wait until I can replace the faulty RPM switch, and actually have my intake runners switch at an earlier RPM (guessing between 3500 and 4000 would be the best). That way I can actually tune the runners on the dyno J



So just to clarify, the knock sensor was too sensitive, picking up vibrations from the headers I assume (only new part), and retarding the timing a lot. I didn’t plug in a scan tool to actually read how much it was retarded, but I know that unscrewing the knock sensor sure did help!



So thanks to everybody who helped me figure this out, especially Mike.

 

[BlackoutSpecV]

so is the knock sensor even in the motor, or is it all the way out and just grounded? I swear this weekend i'm going to get up under the car and in the engine bay and learn about this bad boy hands on.

(he says knowing the work-week from hell means he may sleep all weekend)

 

[BlackoutSpecV]

okay re phrase (sorry guys its late)

Was the knock sensor in the motor (if so where; block, head...)?

Now you have it just ziptied to something and the wire or sensor is grounded....

guess what i'm asking is, is the knock sensor physicaly out now, or did you just ground the wire to the knock sensor.

man, its so much easier when you know ever square inch of a motor... i miss working on hondas all day... but god i love driving to my air conditioned office in my air conditioned SE-R

 

[ezcheese15]

The knock sensor is located on the back of the block, underneath the intake manifold. It is bolted to the block. I unbolted it from the block, ziptied it to the firewall. Then grounded it by wrapping a wire around the knock sensor itself, and running the wire to the block.

 

[cortrim1]

knock sensor

okay re phrase (sorry guys its late)

Was the knock sensor in the motor (if so where; block, head...)?

Now you have it just ziptied to something and the wire or sensor is grounded....

guess what i'm asking is, is the knock sensor physicaly out now, or did you just ground the wire to the knock sensor.

man, its so much easier when you know ever square inch of a motor... i miss working on hondas all day... but god i love driving to my air conditioned office in my air conditioned SE-R

when you find it please take a pic and send it to me. I think I found the knock sensor but I could be wrong.

[email protected]

 

[BlackoutSpecV]

cortrim1

I will check tonight when i get home from work, and i'll e-mail you the pics.

--- Scott

 

[cortrim1]

I found it

I found the knock sensor I was in the right place but looking at the wrong sensor. If you jack up your car and get directly under the oil pan you will see it on the back of the block it looks like a donut and has a 12mm bolt in the center with a wire harness comming off at a angle. I will have to drive the car more to see if it made a difference also I will use a pocket logger to check the timing, since I have my timing numbers from this weekend when I was on the dyno.

 

[BlackoutSpecV]

Did'nt find it...

cortrim1,

Glad to hear you found it, i was'nt so lucky. Although thanks to your description i think i will check again tonight.

 

[cortrim1]

knock sensor

it took me a while to find it as well but just remember its round and made of a rubber material with a metal insert and a bolt through the center. You may have to loosen the bolts on the vias
solenoid to get it out I did. The bolt does not have enough clearence unless you loosen the bracket thats in front of it.

 

[BORNGEARHEAD]

[So just to clarify, the knock sensor was too sensitive, picking up vibrations from the headers I assume (only new part), and retarding the timing a lot. I didn’t plug in a scan tool to actually read how much it was retarded, but I know that unscrewing the knock sensor sure did help!]


To me it's obvious. The knock sensor is picking up the vibration from the engine because you took out the balance shafts. Maybe? Maybe?

I'm not quite sure why the header would cause vibration or knock.

 

[ezcheese15]

[So just to clarify, the knock sensor was too sensitive, picking up vibrations from the headers I assume (only new part), and retarding the timing a lot. I didn’t plug in a scan tool to actually read how much it was retarded, but I know that unscrewing the knock sensor sure did help!]


To me it's obvious. The knock sensor is picking up the vibration from the engine because you took out the balance shafts. Maybe? Maybe?

I'm not quite sure why the header would cause vibration or knock.

But...I had dyno'd it with the balance shafts removed and did not loose any HP. Not until the addition of the header.

 

[cortrim1]

knock sensor

according to mike kojima the knock sensor is too sensitive and even simple mods can cause the timing to be retarded up to 8deg.
I think I had this problem with my car and I will check it with a pocket logger to see if the timing is different with knock sensor grounded. I have my base line timing numbers so this will not be hard to tell if their is a difference. I can tell you that the car pulls harder to redline with the knock sensor grounded according to my butt dyno.

thanx to torry and trav for the info on the knock sensor

 

[ezcheese15]

Yeah, mine is without a doubt faster. I haven't dyno'd it since I took out the knock sensor, but I would bet I gained 20+ HP from removing it.