possible detonation from previous owners N2O

ive had my car for a few weeks now. the guy i bought it from is pretty reliable and straight up, bought my old car from him as well. anyways he had a Nitrous works plate system on the car with a 125 shot, and that was pretty much it. had a WOT switch and arming switch that he hit when the car was about 3,500k id say. so he didnt have window switch or FPSS and he sprayed at w/e bottle pressure (no heater or gauge or anything). anyways to the point, ive been noticing a small knock when i accelerate. i usually have to give it a little more than normal acceleration but not much more. it sounds like marbles or something, kinda quiet, but definitly noticeable and it seems to be only happen/ be much more evident, when the car is cold. it has a 160 stat and TB bypass so it runs very cold in chicagoland weather. i was wondering if maybe anyone had any ideas or thoughts about as to what this is. could it possibly be detonation? BTW, i havent fully laid into it yet and gone through the gears but there are no signs that it is down on any power at all, seems very strong. any help would be awesome. thanks

Sounds like you need a tune. Those marble sounds are not good and everytime you here it it puts wear on the engine.
Im guessing you are talking about this happening NA and normal driving. I would start with checking your spark plugs.Then take it and have the tune looked at.You may be running lean or just to much timing.If you are not running super unleaded try that.If you do not have a tunner in yuor area I always use Moe Baily.He does mail order tunes also.If you need his number feel free to pm me.
Dave

well i was setting up a full exhaust with longtubes and what not and then i was gonna get a full mail order tune from MadZ28. should i save the money and just go right to Speed INC and have professionals actual get their hands on it? but that is a lot of money i have a feeling.

Unless the previous owner disabled the knock sensor there is no way you will hear detonation. The sensor prevents it. Check with him.

Like Dave said check the spark plugs for black or silver specs.

Otherwise maybe you can hear the rocker arms, I'm guessing oil pressure is good.

my old car was a 93 Z, it was quieter than ****, except the exhaust. that ran excellent. this car will walk that car and pulls like hell, only difference is this kinda has a knock. im thinking maybe its somethign to do with the cold. its been around 0-20 degress outside. oil pressure is awesome, if i beat on it i wait till about 170 degrees just so i know the t-stat is open. i havent looked but im damn near sure the knock sensor is still connected. this is what he said about the plugs"I put new Autolite 103 sparkplugs gapped at .035". im not sure if those are nitrous plugs or what. this car really does seem to run awesomely and it doesnt miss or anything, just sometimes that knock. any more ideas? you guys think it would be fine to go ahead with my longtubes/y pipe and maybe check the plugs while im doing that?

You can still get knock if your tune is WAY out of whack. The knock sensors will sense knock and pull timing...but it only has so much authority as far as I know. If the tune is way off the timing pulled may still not be enough to prevent 100% of the detonation.

You could put a few gallons of 100 octane in it and try again. If the knock and pings subside...its likely detonation. If not...look for somewthing mechanical as stated above.

will a basic mail order tune help out? i know they are supposed to help with performance but will it help get things correct in the computer if it really does have a messed up tune right now? basically im asking if this needs to be a trial and error thing like pull timing and run it etc...

I dont really see a reason, based on your mods, why your tune would be SO off that it should still knock taking into acct that the computer will sense knock and pull timing. This means you would have to be WAY out of whack to still have detonation.
I would not get a tune just yet. I would also not beat on the car just yet.

I would get 5-7 gallons of 100 octane unleaded and put it in the car to see if detonation goes away. If it does a tune may fix you up.
I would also check your fuel pressure to see that you dont have a dieing pump or some other fuel issue. If so fix that first.
If possible then get a dyno tune with a good tuner so he can see your AF ratio and adjust it as required as well as timing

i just seem to think that if there was somethign wrong with the tune/fuel etc... the car would run like crap. right now if the noise wasnt there you wouldnt suspect anythign was wrong at all.

but if the noise is actually detonation...believe me...its running like crap. LOL.
It really means either too little fuel or too much timing for the parameters the car is operating under. Several things can cause that.

And if it detonates on motor as you describe...it will likely be catastrophic if you spray it.

alright. i just requested a qoute from Speed INC. im gonna see if they can just check it out and maybe see if everything is alright in the PCM itself and other stuff. a full dyno tune is 500 bucks from them, but if they tell me its something really simple ill just continue on with my exhaust and mail order tune plans. we'll see. thanks guy.

Man it sucks to have to pay that. But it will help you down the road. One thing though. Dont just take it in for a tune and drop it off. Be sure to tell them that is seems you are detonating and that if necessary you will get a tune to correct that if thats the problem. May want to have them look at it and scan it first to see if its something simple and NOT tune related. If something obvious doesnt jump out at them...if there is a mechanical or sensor issue that is causing this...they will likely uncover the problem during the tuning process. So hopefull its money well spent. Good luck!

One more question...do you have any SES or check engine lights?

nope SES never comes on at all. i just got an e-mail from Larry at Speed INC. he said they can have a look at it and tell me their best guess. so i asked what it would cost if anything to have them check it out and what it would be to actually scan it etc. it just seems weird cause the car seems like nothing is wront at all, just the stupid knocking. ill see what he says and maybe ill take it over there sometime. thanks again

Good deal. Hope its something simple first. But even though the car isnt terrible...the knocking needs to be fixed before you proceed to nitrous. Youll be glad in the long run when the car is running right and making great power.:)

Seems unlikely that a "great running" stock car, operating in sub freezing weather, with a cold stat, and a bypassed throttle body, all anti-detonation, would produce any, let alone audible detonation.

I was barely able to confirm (hear) audible detonation under moderate acceleration, lugging the car in high gear, with a hot engine, with 50-60 degrees advance forced into the ignition advance table. And only with the laptop hooked up monitoring knock count and knock retard for verification.

I doubt you're able to hear detonation with a correctly functioning knock sensor and stock programming. The computer just doesn't allow it. And, the dynomax muffler would make it almost impossible. The car runs good, the computer is working.

The computer is capable of pulling 15+ degrees timing under various operating conditions using many different criteria.

You should find the rattle, since it bothers you, and before you beat on the car. Check the plugs, it's free. Buy an AKM cable for $50 and use freescan (it's free) to look at knock retard and count.

I'd look for a loose heat shield or something else that's about to fall off.

My 2001 GMC Sierra C3 with the 6.0 LS1and its getting audible knock right now in Fl....although very minor. The weather is cold and it runs very good. Under certain curcumstances...depending on the tune cool weather can sometime create more knock due to better cylinder fill. Especially at part throttle. Just because the computer senses knock doesnt mean it will pull enough timing to cancel all of it. Especially at part throttle driving. Even the knock paramters are adjustable.
Now at WOT it may be different entirely.

If it were my car I would do the following:
1) Establish if it is knock or not via a scan or the cable mentioned above, or put some 100 octane in and see if it goes away.
2) if its knock fix it either via a retune or correct the issue thats causing it if its a fialed or degraded sensor
3) if it is determined it is NOT knock. Find and correct the problem

The priority here is to establish beyond a shadow of a doubt that it is not detonating and that your tune will be nitrous freindly. The result otherwise could be catastrophic. If you look at all nitrous manufacturers website the first disclaimer is alwasy "be sure the car is in perfect running order with no issues"

Thats there for a reason.

That cable mentioned above by Andy seems like a good option. Its cheap...and it will come in handy in the future. Again...good luck.

alright im scheduling an appointment at Speed INC tomorrow. Larry said they can scan it and just give me an honest opinion for free. hopefully its nothign really at all or a very easy fix. im gonna talk to them and see what they can come up with. ill keep everyone updated. thanks

Now ya cant beat FREEEEE:bow:

Good luck! Hope its something simple so you can get to spraying and beating on your car:D

lol. i hope it something simple, stupid and cheap. so then i can continue with my longtube/offroad y pipe install. thanks again to everyone who contributed their thoughts.

Quote: "My 2001 GMC Sierra C3 with the 6.0 LS1and its getting audible knock right now in Fl....although very minor."

Sounds like your truck needs service.

Quote: "The weather is cold and it runs very good. Under certain curcumstances...depending on the tune cool weather can sometime create more knock due to better cylinder fill. Especially at part throttle. Just because the computer senses knock doesnt mean it will pull enough timing to cancel all of it."

What would be the purpose of a team of GM Engineers spending hundreds of hours and thousands of dollars concepting, designing, manufacturing, and programming a device that senses detonation but doesn't retard the timing enough to prevent enging damage? I know, it's a spare part conspiriacy. LOL.

Additionally, please PM me your part throttle test data I'd like to learn more on the subject than my own testing allows. Thanks.

Quote: Even the knock paramters are adjustable.

I looked in the car and the manual I can't find these knobs anywhere.

Quote: "Now at WOT it may be different entirely."

No one mentioned WOT operation. The main knock sensor programs use two engine parameters to determine retard: engine RPM and MAP. There is yet another program "burst knock" that is activated from sudden changes in throttle position but still not one program strictly devoted to WOT engine operation.

Happy holidays.

My truck does need service. The Area right around the flyby wire TB has a tendancy to build up a "lip" of grime that can be as much as 1/2 MM thick. This is enough to cause some airflow descrepencies that cause some undesired behaivior. 1 is idle surging...the other is detonation at part throttle. Clean the TB and the area behond the blade...and it all dissapears. ANytime we mess with the airflow such as removing MAF screens we can induce areas of operation that arent fully covered with GMs stock program. Yes...even knock

No one said anything about engine damage from light knock.

GM does a damn good job of setting the knock parameters...but they are not 100% foolproof under all curcumstances.

Many LS1s experiance light knock in bone stock form. When you do mods you can further upset the balance.

Knock paremeters atleast on LS1 can be manipulated via LS1edit of other software...including the amount of timing the computer will pull overall, how rapid it brings the timing back in after knock is not sensed and a few others. Im sure the LT1 would be somewhat similar. I never stated there would be "knobs".

well i went to Speed INC this morning. its about a 30 minute drive so the car was at running temp when i got there which kinda sucks cause the sound is unnoticeable at warmer temp. anyways he couldnt hear it cause it was warm but he scanned it and everything checked out awesomely, he said i have a tiny miss, and should prolly just do a nice full tune up and he said the noise is most likely piston slap, and not to worry about it. so im continuing with my long tubes etc. and im prolly gonna go with a OVC wire kit, new coil and stuff like that, then a MadZ28 tune:) anyone have any ideas what it should be pulling in the quarter with those mods? im figuring as it sits it should be 13.8's or so with a mediocre 60'. thanks again for all the help guys.

Sorry for the post jack.

Cool now you know. Let the moddin' begin.

Headers are worth a couple tenths. Who's are you buying?

A good tune is worth a couple tenths.

It should be close to 13.8, maybe faster. May take a little while to learn to "launch" the car at the track with the six speed. Get some sticky tires.

Where are you going racing in this cold? Do you go to 66 or 41?

Let us know.

my old 93 Z had a CAI, bullet after the cat and free mods and i went 14.1 in that thing, so im figuring this car should be a bit quicker as it is now. it definitly feels much faster then the Z. i never drove the Z in winter time, but it was a little damp out the other day and i roasted the tires all the way into 4th gear. just stabbing it and shifting very quickly.lol. im hoping for anything better than a 13.5, i might get some Nittos before i go too tho. i usually go to Great Lakes Dragaway in Union Grove, Wisconsin. im only 16 so the first time i went (with the 14.1) it was three days after i got my liscense, and just as i started getting a method down and getting a better feel for the car it started raining so i had to go home:( will a low 13 be feasable with the full exhaust and tune if i can pull say a 1.9 60' and go through the gears well?

I worked hard to get to 14.0. My car started off with 14.4 - 14.5. So you never know what she's going to run till you get there.

The short time will be key. Get the good tires.

I'd run it open headers, maybe you'll have a chance.

im running the Hooker LT's, offroad y pipe, then the exhaust that came on my Z before i changed it to the bullet. its kinda like a loudmouth but homemade, with no muffler. i want winter to be over so i can head to the track.:D

That should be pretty loud.

I'm probably going to go with pacesetter cause i'm cheap.

I hear ya, at least we had a warm up.

I've been working hard to get ready for spring.

Guess we'll be watching video's till then.

lol yea. i have so much on my plate to do before spring.

install headers, y pipe, rest of exhaust, get computer tuned, new wires when headers go on, install my Eibach's, wanna do a poly trans mount, new tires and paint my hood.lol

My car ran the time in sig. at GLD this past Summer. FWIW, I sprayed a ~100 shot and it ran a 12.8X @ 115 MPH(will probably run closer to 118-120 MPH this year). Getting out of the hole is KEY!

I was also going to add that I hear all kinds of noises now that the weather is cold. Engine noises, suspension noises, dash rattles, etc... The cold amplifies everything big time, especially in Chicago on those zero degree morings. If I get on the gas at all before the thermostat opens, it sounds and feels like the car is going to fall apart. Chances are you were experiencing the same thing.