I have a very thorough street tune on my UTEC and didn't expect too much trouble from having JWT S2 cams installed. I aslo got valve springs and an HR oil pump (VQ35DE engine). I figured that the AFR would have to be adjusted to handle the increased air flow, and a little timing might need to be pulled.

Was I wrong! First thing, I set up the laptop and had my wife call out knocks for me while I logged some light pulls around the industrial park. At 40-60% load, 2000-4000 rpms, there were a lot of knocks- like one every 2-3 seconds. I have my UTEC set to run factory ECU timing below 3000 rpms, and I was getting a lot of knocks there also.

I pulled some timing and enriched a couple spots where the AFR was getting into 15:1, and set out again. Same thing. Knocks galore. I set the timing from 2000-3000 rpm to 17 degrees, then like 25 degrees above 3000 rpms in the light load ranges and then had a brain fart. The tuner display came up instead of the UTEC display, and I couldn't figure out how to change it back. It was late and I was out of options, so I drove home- for 3.5 hours on the interstate. I don't know if I caused a lot of damage, but the car seemed to be running OK for the trip. It was 105 degrees in Phoenix, which didn't help.

I am wondering how to tell if my knock sensor is over-active, or if I am really getting a lot of detonation even with the timing retarded. Also, has anyone else had a similar experience? BTW, I remembered how to get the UTEC display back later on last night. I will have log some runs on my days off to see how bad I was detonating at cruising speed.

 

The best way is listen for yourself, while you're at it calibrate the UTEC knock thresholds.

http://uprev.com/documentation/Knock...n%20Device.pdf

I'm guessing your stiffer valve springs and bigger lift is making more noise and your thresholds need to be adjusted...hopefully.

 

If you can put in some 100+ octane gas (unleaded if u have cats) and then tune the knock threshold table, I think you will find that djamps is correct - new valvetrain noise, not knock...

 

I was hoping it was a noisier drivetrain but my mechanic friend said it would be a constant knock if that was the case. Should I be able to hear it, even with a big single exhaust? The car is so loud it's hard to hear the engine bay noises. I'll try the 100 octane and adjust the knock sensitivity. Will the car sputter or hesitate if its knocking? I can feel the computer pull timing, but no hesitation otherwise.

 

there sbould be zero need to adjust the utec calibrations for aftermarket cams or springs - I never touched knock sensitivity on my utec why I ran it

are you sure your cams were installed correctly in time? if they are off, you're going to have an impossible time tuning it

 

Depends on if they were already calibrated or not. They are supposed to be...if you never changed them from default I doubt the knock detection is doing much for you.

 

To tell if it is real knock as long as it's below 5000rpm. First is the ECU pulling timing? Look at the Stock ECU timing and you will know if the ECU see any knock. If not then it is false knock and reduce your knock sensitivity. It could be utec that is pulling timing and not the ECU and that is why you feel it.

 

I let the utec do knock exactly as the stock ecu did knock without any additional changes. I never ran into issues but have not used the utec now in a year

my guess is something else is going on

 

default Utec Knock setting is to sensitive IMO especailly above 4000+rpm.

 

On my particular motor and it's setup, I never once had knock counts with several different tunes by 2 different tuners, as a stock internal motor with bolt ons (December 2005) to the motor build (2007 till last year) on pump gas. Sensitive knock is a good thing IMHO, I saw no reason to alter it, and I know Jermaine from TXS also suggested just leaving those settings be as well (he tuned my car 2 times)

 

Yes, his advice is to leave it alone but there is definitely false knock at stock level at least on my car. I was chasing knock around 2700rpm-3000rpm and for the life of me I couldn’t remove it even after pulling timing and adding fuel. I reduced the sensitivity and made adjustment on the Open Loop crossover point and it went away. Stock ECU wasn’t pulling timing so I know it wasn’t real knock. This is why I asked to OP if the stock ECU is pulling timing at the knock area, if not then I suggest reducing the knock setting.


OP,
Do you knock just before you hit Open Loop and just before Utec takes over? What is your MAP Min. Value for mapping and what is your Open Loop Map Threshold? There is a delay on the Open Loop threshold so sometimes you want to hit the crossover a little sooner before you hit your MAP Min. Value.

Edit:
I think Your NA so never mind about MAP value question.

 

The mapping kicks in at 40% I think. The UTEC takes over fuel at 3000 and timing at 3000 also (until now). I found that the ECU was more aggressive with timing at those rpms than me, and it varied a lot. Plus I was getting a little knock going uphill at light load and decided to just let the ecu handle everything at cruising speeds. I thought the variable valve timing was doing it's thing too, so I didn't want to mess with it.

Once I started driving with the new cams, I was having the most knocks at 40-60% load at 2300-2800 rpm. I will be tuning tomorrow and getting a better idea of what the problem areas are. The other day I was under a lot of pressure to get the car drivable and didn't have much time to really look at it. Sounds like athenG's description. I will be interested to do some logging at 70-90% and see what's going on up there. Despite adjusting my MAF voltage setting, the car has yet to show 100% load. I'm hoping that all the airflow mods will kick it up there.

Thanks for all the input- this is where forums can really be a value to the community

 

My car is screwed. I have had to pull the timing to lower settings than OEM, reduce the fuel at higher rpms, add fuel near idle, and I am still getting a lot of knocks. I did some calibration of the knock sensor, which may have helped some. In the morning, I did a few logs and it seemed like I was getting somewhere. I went out in the evening, and it was knocking like crazy again.

I thought with cams I would gain power, not lose it.
I don't have any idea what to do at this point. Even Jack Daniels isn't much comfort. Knocks are across the rev range and in all of the load ranges. I can't even run in certain rpms on cruise control without getting knocks. I think I can even feel them sometimes, but not all that often. So I still don't know if it's just noise or a real problem. It's likely a combination of both. The worst part is, I don't have a shop within 150 miles that I can take it to. I was doing so well tuning up until this cam debacle, too.

 

Again how do you know the cans are in time?

 

If you aren't able to determine real and harmful detonation, from noise, or other factors you really need to get that car on a dyno, in the hands of a pro. I don't mean that in a condescending way, so hopefully you won't take it that way.

Just because one car needs no adjustment to knock sens, doesn't mean that another car or setup won't. Either way, a good tuner or a proper dyno, and diag tools can determine this for you, and optimize your tune.

 

You are 100% correct, Sharif. Since I don't really know when it's detonating and when it isn't, I am fighting a losing battle. I just looked up the knock sensor location in the manual, and it appears that it should not have been removed for the install. I was wondering if it wasn't torqued to spec, but now I've ruled that out.

The only knowledge I have of the cams being installed correctly is the shop's assurance that they checked it repeatedly and spun the motor several times to make sure it was aligned right. I don't have any way to verify it. I am thinking it might be best to tow the car back to the shop and see if they can get UMS to try and tune it. I imagine a shop of that caliber would be able to tell if everything is in order.

Two other possibilities: One is the HR oil pump. Could that influence the variable timing since it is a hydraulic setup? The other is my Y pipe. I have been waiting for the Motordyne pipe to come in, but for now I have the OEM pipe. It is a huge bottleneck in my exhaust, which is otherwise pretty open. Any chance the backpressure and turbulence between the test pipes and the Y pipe could be causing these kind of problems? Just taking a shot in the dark.

 

First, you don't have an HR pump, you have a revup pump (different pieces, but people may get confused). They basically either work or they don't as they are purely mechanical. Assuming you used a new one from Nissan and oil pressure looks good on your gauge, it should be fine. Anything is possible, but I've never seen/heard of one go bad yet. The Y pipe will not have any signficant effect that I can think of. It may or may not limit peak power, but it won't affect knock readings

 

Does the car run properly in any condition? If it runs rough at all times, your cams may be out of time, assuming it ran properly before the cam install. The oil pump and exhaust shouldn't influence your tune at all really, you shouldn't be seeing really any knock at such low load/rpms, especially since you have gone so retarded on your ign. timing.

 

Thanks for those clarifications on the pump and Y pipe. I also adjusted the tune a little bit at 60% load because the timing was more advanced there than at other loads. That hepled. I reduced the knock sensitivity a little bit at higher rpms, also.

I went out this morning and got race gas. The gas didn't seem to have any effect on the knock count. I did notice that I get a string of knocks under moderate acceleration and when decelerating. Coincidentally or not, that is when the engine makes a lot of noise (the good kind). Just criusing or lightly accelerating, I just get an occasional random knock that I can't attribute to anything.

The car feels and sounds fine. I think if a mechanic get into my car knowing nothing about it's condition, he would not suspect a problem. There is no check engine light, either. If the cams were out of time, I suspect it would throw a cam position or crank position code, right?

 

If you're getting continuous knock detected on decel then it's obviously a false alarm. I would adjust the thresholds until the decel knock is gone, that might take care of the rest.