Problems with Detonation after Plugs
 

I replaced the original plugs with NGK Iridium IX BKR5EIX in my 1992. I also installed a K&N and a Marc HAibeck chip the same day. Now, I get a TINY amount of what I think is detonation just after 2nd and 3rd gear. You have to listen for it....but it is a definate...click...click...click on acceleration.

I installed the plugs with no gap change as they are gaped at .50. I left the washer on when I installed them.

Suggestions?

As far as I know, it was not detonating with the original plugs (though it ran like crap in comparison)

Re: Problems with Detonation after Plugs
 

UPDATE

I just got back from this procedure:

I decided to look at the most simple things first and then move forward. I drove the car (detonation)..I came home and disconnected the batt and removed the marc haibeck chip and put the stock chip back in. Zipped it back up and drove it (NO DETONATION) came home...put the marc haibeck chip back in and drove it (DETONATION). I did this 2 more times as the temp went up outside to near 80 degrees. I am going to drive it again this afternoon with the stock chip in when it get hotter outside. I did all drives with the AC wide open and hit many a hill to put the engine under a load.

Haibeck chip=detonoation
Stock chip=no detonation

The car does not have the crisp power of the haibeck chip etc etc..and that sucks. But the detonantion is gonehttp://images.corvetteforum.com/imag.../confused5.gif http://images.corvetteforum.com/imag.../confused5.gif

What do you guys think?
Can Marc burn a new chip with different parameters to work this out?
http://images.corvetteforum.com/imag..._invisible.gif http://images.corvetteforum.com/imag...ons/report.gif http://images.corvetteforum.com/imag...c/progress.gif

Re: Problems with Detonation after Plugs
 

Call Marc, I have the chip in with Bosch Platinum plugs gapped at .035 and have no problems at all.

Re: Problems with Detonation after Plugs
 

Do you think I need to regap my plugs to .35 instead of .50?

Re: Problems with Detonation after Plugs
 

What concerns me about this, is the fact that you can hear detonation. I would expect the knock sensor to detect knock & back out advance timing. Marc's tune may be optimizing A/F to make the engine develop more power, but would still be controlled by ECM knock sensing.

Failure of a knock sensor should throw a code and prevent open loop performance. I would be looking into replacement of the knock sensor or checking the lead/connection.

Youe OEM chip may be "fat" enough to prevent the knock, but wouldn't develop the hp Marc's chip would.

Re: Problems with Detonation after Plugs
 

You can hardly hear it when it does it. My wife is who noticed it. It is a click...click...click (sometimes just one knock) right after you switch gear and hit the gas. Definatly detonation.

Could the plug-gap have anything to do with it?

Re: Problems with Detonation after Plugs
 

BTW, when I cranked it the other day...I got an SES light. It did not come on again, but I pulled the code and it was code 43 (which I think is the knock sensor)

The light has not come back on since

Re: Problems with Detonation after Plugs
 

Not in my opinion. Under the worst scenario, you would experience a miss-fire, specifically incomplete combustion or no combustion at all, i.e. a dead miss.

I have yet to see or hear a plausible explaination regarding the gap difference between the early & late LT5. All, use the same ignition system. Plugs are interchangable, both washer & tapered seat. IMO, 0.050 gap is correct for the Iridium plugs. At the risk of being flamed, I would recommend running 0.050 gap on all years just for the benefit of a bigger spark. If the rest of the ignition system is in top condition, it should perform fine.

DTC 43 is the knock sensor. The service manual procedure for checking the knock sensor loop is fine if the sensor has completely failed. Mine failed intermittently. Resistance checked fine several times until it was finally open the last time. A real bear to analyze under those conditions.
Good luck with your diagnostic procedures.

If you're planning on calling Marc, please post his opinion. Always interested in Marc's wisdom!

Re: Problems with Detonation after Plugs
 

Marc emailed me about Code 43 and said pretty much don't worry about it unless it comes back.

We are going to speak in-depth about the chip/plug situation tomorrow.

I tried to put a fresh tank of 93 octane Exxon and octane boost in and reinstall the Haibeck chip. It did not help. But, you put the stock chip back in and the car runs like it always has (well, a little better with the new plugs)

From the lack of response on all forums about this.....it must be a unique situation (which is par for the course with my cars)

Re: Problems with Detonation after Plugs
 

From Marc

You're getting tip-in throttle knocks. They are quite common on most LT5's. The issue is addressed by my calibration. This is described on the information sheet that came with the chip. While the knock sensing is tuned to reduce the effect on engine torque, the additional spark advance that is a big feature of the chip work in opposition to that.

The knocks that you are hearing are happening as the throttle opens, initially the engine goes lean as the throttle opens, and it knocks. Beyond about 50% throttle the engine gets fueling for the load and the knocking stops. When I drive a car, I evaluate that situation by monitoring the knock system with a scanner. Normally the scanner reports an approximately 3 degree retard event and then another smaller one. About half of the LT5's do this. The knocks are not harmful because the engine is under light load at less than 50% throttle. Using 93 octane fuel might help. A .050" spark plug gap might help.

We could try to make tuning adjustments for your engine, but some of the improvement in throttle response and low speed torque that you are noticing with my chip will be diminished.

Re: Problems with Detonation after Plugs
 

You should try running the Haibec chip with a colder set of plugs. 1 heat range may make all the difference. If the problem is tip in fuel, you could take a look at the fuel pressure when it happens, it may not be increasing as it should. These 2 things were problems for me when I first got my ZR1. Goodluck, nothing is more annoying than a problem at WOT.

Re: Problems with Detonation after Plugs
 

The problem only happend at low speed and medium speed....

When I hammer down...it seems to be fine...of course it is so loud, I could not hear the knock

Re: Problems with Detonation after Plugs
 

Ahhhhh, then the solution is simple, just stay at WOT throughout your entire driving experience. Goodluck with the fix.

Re: Problems with Detonation after Plugs
 

That is pretty much what Marc said.....drive it like I stole it...because the previous owner didn't

Re: Problems with Detonation after Plugs
 

I just put in a Haibeck chip 1 week ago and its great; can feel the difference. Still using stock plugs and at 17500 miles.
For what its worth.

Re: Problems with Detonation after Plugs
 

LowFlight, Did you ever get a scan done on your engine to get a positive verification that you are getting knock? I have scanned mine and my I get a lot of knock spark retard events. I am trying to isolate the problem to something that I can fix or tune out.
Thanks, Jim

Re: Problems with Detonation after Plugs
 

i would. the larger the gap the more it taxes the rest of the ignition system. everything is going toward smaller gaps these days. that said if you have detonation at .050" it'll probably still be there at .035". the last NHRA SS/AS legal super stocker i built made a little over 2.3 HP/Cube with one 4150 carb naturally asperated & i set the gap at .035"ish. didn't want any more.

Re: Problems with Detonation after Plugs
 

for what it's worth do yourself a favor & install new plugs.