Engine Management Options?

[Stubby~CC]

I am totally clueless is this area, so I thought I'd see what you all knew.
I did a search and found info on elementalvoid's alpine system, but it wasn't much help. Plus they're gone anyway.

My knock sensor is broken so the ecu won't put enough fuel in my engine. So I'm not getting very good power. Better than a non-sc, but not that great. Especially at higher rpms where it seems to cop out. Did the bypass, bad idea. Got knocking like crazy and overheated, so that's out. Replacing the knock sensor is pricey and pita option, but might fix the problem.

I'm not really convinced the stock ecu is up to the task of properly tuning the engine, especially with the smaller pulley on the sc. I figure if I'm gonna spend the time and money, maybe I could find a better way.

What piggy back or stand alone options are available if any? What kind of price ranges would I be looking at? How hard is the install? Would I need to find a shop to tune it? Am I even thinking about this right?

All these questions and whatever other info you may have would be appreciated. Thanks In Advance! :)

[Nissanclay]

I haven't been able to find any piggy back systems. I know they have stuff for the 2nd gen frontiers. I to would like to find some type of system.

[tmorgan4]

There are tons of options that can be adapted to the VG33 with a little thought and ingenuity. Most basic SAFC units just "modify" your MAF output before it hits the ECU.

I'm VERY surprised to hear of severe knocking with the bypass installed, though. That's not a good sign by itself.

I've got a friend selling a water-meth injection setup. It helps cool the intake charge and could possibly help with some of the effects you're having.

EDIT: I completely forgot about modifying the stock ECU to make it 'tunable'. Have you ever looked into a system called Nistune? They do some amazing stuff with a factory ECU. It replaces the OEM ROM with one that enables real time tuning all from the factory ECU. I'm curious if they've tested it on the VG33.

[Packman5280]

even with a stand alone, you would need a working knock sensor i would imagine.

[tmorgan4]

Most complete standalone setups are made so that they don't require much. You can always ADD a knock sensor but a lot of people prefer a good tune over relying on a knock sensor to keep you're engine from committing suicide.

[Ryan Gee]

Sell the pully...

That sounds wacked... wonder if you maf is messed up. Knocked til overheating can't be a good thing.

Have you changed out any of the O2 sensors in the past?

Hmm, how good is your fuel pressure, or have you ever replaced the fuel filter?

[ChefTyler]

Are you running premium fuel, if not and you're getting knock that will help matters. If you are getting bad knock with the bypass then you have issues besides a bad knock sensor.

[Stubby~CC]

Yep, running premimum fuel, 91. Fuel filter was changed maybe 10k ago. Is there a way to check fuel pressure? My fuel gauge sometimes acts weird, so that is suspect.

Can't sell the pulley because we bent the stock one getting it off. I guess I could buy a new 2.5, but not high on my wish list. My understanding was the 2.4 could be run without any problems, not true?

The truck was throwing a cel when I bought it. I got all over the dealer based on the lemon law and they ended up paying empire nissan to install a new ecu, several wiring harnesses, and 4 new o2 sensors. That should all still be good as I've only put 30k on it.

How can I check if the maf is bad? The only code I'm throwing is the one for the knock sensor.

I'm curious what other things could cause knocking? As it is I'm not getting any knock, but it's not running right either. I think a new knock sensor is going to have to be done. If there's another problem, I'd really like to fix that too.

[Allen Cox]

If your MAF is reading incorrectly, it could cause a lean condition, but typically that will throw a code for the O2 sensors reading incorrectly. It's kind of a PIA to diag because of the faulty codes. The O2 sensors are actually reading correctly at that point, but the MAF is the culprit.

Only having a knock sensor code though, your ECU is keeping the bypass valve open, only allowing minimal boost. That, in and of itself can mask other issues. A bypassed S/C can make noise as well, similar to knocking, but not quite as pronounced.

When you performed the bypass, did your boost kick back in? Just insuring a good bypass. If you're bypassed, then the code won't come back. But you're still getting a code?

Maybe back your timing off a bit and see what that does for you. If you're boosting more, I'd be backing the timing off about 2° anyways, from stock. Since I'm advanced for altitude by 2°, then that would back me off a total of 4°. That will help with combustion temps as well, without having to go through the trouble of injecting washer fluid or water/meth. Both of those work, and work really good, but it's a lot of trouble to keep another bottle full of stuff on top of gasoline. Used more on high boost turbo cars.

A 2.4 pulley should be working good for you with a bypass. I'd double check your ohms on the resistors, insure they're on the correct wires and after that, that you're not getting the code any more.

Otherwise, an SAFC-II is supposed to be a pretty good controller, with multiple programs for power and stock (for emissions purposes). Mac Autosports (on Parker Road) sells them and tunes them. They have an all wheel drive dyno and specialize in modified vehicles.

[DamnHippie]

I did the resistor for the knock sensor, there's no question that it was the right value. Also, I did insist on a couple rounds of before/after testing to see that the knock sensor code would come and go as the resistor was added/removed. Martin reported a bunch more power with the resistor in, and that's the first time he ever got knock (more evidence that the resistor was right). The overheating came after a couple miles of climbing a 10-12% grade (the switchbacks on Overland road just above Jamestown).

I think checking the timing is the next logical step, I dunno why that didn't occur to me before. (I guess I'm just so used to computers taking care of timing these days.) I suppose it's time I finally got around to buying a new timing light.

[Allen Cox]

Ah! Since Ian put the resistors in, I have zero doubt that it's correct. You're all set there.

I would then suspect the timing.

The overheating thing is almost another issue I think. It might be time to pull that radiator out, backwash the fins of both the radiator and the A/C condenser. Doing it in the truck won't get the same results for the radiator, but the A/C condenser will need to be done in the rig.

So the knocking and the overheating might have occurred at the same time, but might have been separate issues. Hopefully!

[DamnHippie]

Overheating is consistant with severe sustained knock. There's no delicate way to say it (and I've said it to him already) -- he should have stopped way earlier with that much knock rather than driving all the way to the top of the hill. (I was in front, and doing my usual race up the hill thing, but I would've eventually noticed he wasn't back there and turned around.)

With severe knock you're still burning the same amount of fuel per engine rev, but because the burning is happening at the wrong time, much less of the burning is turning into work, which means instead it all turns into heat that has to be dissipated.

We disconnected the bypass resistor, btw, until we get things figured out. We were actually just talking on the phone a few minutes ago about the concept of wiring the bypass to a switch in the cab. It would pretty much give you an on/off control for boost. You could leave it off for better mileage on low-octane fuel or put premium in and turn it on for wheeling.

[Stubby~CC]

LOL, it still took like 2 minutes for you to figure out I wasn't behind you anyway. I feel bad for my truck for what I did to it. But I apologized to it and we've put it behind us. I don't think any long term damage was done.

I haven't had any overheating issues other than that one time, so I'm pretty sure it was a cause and effect kind of thing. It cooled right back off at idle on the side of the road and hasn't overheated since.

Researched the SAFC-II. That is exactly what I was thinking of. With the part and dyno tuning it looks like it would be $500-600 or maybe more. Definantly not cheap or easy. Plus, it requires a working knock sensor. I don't think I'm going to go that route any time soon.

When you mentioned the timing, it was kind of a duh moment for me. Should have thought of that. I've come to the conclusion that the original owner was trying to build the truck into a street racer, which it so isn't. Besides all the messed up wiring and junk previously mentioned (the new harness is what finally fixed the cel). The truck had goodyear f1's on it, which is a dumbass tire choice for a truck. I wouldn't be surprised if we find the timing had been advanced beyond the stock setup, making the problem worse.

The computer can do some adjusting of the timing right? Does it have a range it can work with off of the physical setting? How do the two relate? Enlighten me please.

[Ryan Gee]

Allen here, on Ryan's 'puter.

The computer does have a range, but it is based solely on the base timing. So get the engine warm and then check it at idle, lights off and no loads (no A/C, no stereo, etc.). Check the sticker under your hood and it should match your timing marks. If not, then subtract 2° off the sticker timing and adjust it that way.

Do me a favor and double check the flow arrow on your fuel filter. Just a piece of mind on that one. Putting it in the wrong way can make it plug up faster, that's all.

Also, double check your radiator and condenser to insure proper flow through there. The heat should be able to be dissipated easily, especially with the S/C engine, as it's equipped with the larger radiator.

[Stubby~CC]

Okay, so we finally found time to check the timing. It was dead on, so we set it back a couple degrees. Didn't seem to make any kind of difference. Fuel filter is fine.

Knocking is happening under two conditions; under heavy load, and at high rpms. I was looking in the fsm and it seems these are two of the conditions under which the supercharger bypass valve should be open. I kinda suspect the scb is not opening when it should be. How can I check it to be sure?