Valve clatter???

[jbice03]

I bought a 2010 GT500 a couple of months ago and decided I wanted a throatier sounding exhaust. While having the exhaust changed I find out the car already has aftermarket exhaust. It already had high flow cats an X pipe and magnaflow mufflers. All I did was change to magnapack mufflers which made the car sound alot better in my opinion but the car ran terrible after that. The day after I changed the mufflers I took it to have it dyno tuned and found out it had an aftermarket upper and lower pulley. Went ahead and bought a JLT CIA and FRPP 65mm throttle body and some NGK spark plugs. The car dynoed 556 RWHP and ran alot better. Ever since I had the car dyno tuned I've had what sounds like valve clatter between 4000 and 6000 RPM also I had the throttle body hang at 5000 RPM on one occasion. I took the car back to the tuner and he changed a setting on the throttle body that is supposed to fix the throttle hanging problem but now the RPMs at idle fluxuate between 500 and 900 RPM. It sounds like it almost dies and then catches. The tuner told me he had the timing advanced 20deg. at WOT and lowered it to 18deg. Called him today and I'm supposed to take it back to him Tue. and he is going to put it back on the dyno. The valve chatter has me worried though. This problem seemed to go away when I added a bottle of Lucas octane booster. Sorry for the long thread I just wanted to give as much info as I could so someone may be able to diagnose this for me. Thanks

 

[VNMOUS1]

Detonation, not valve clatter, most likely.

 

[jbice03]

Thats what I'm thinking from what I've read so far. I only run 93 octane fuel and have fueled up at several different stations. The timing advance is at 18deg. now and I've read here alot of other people are running upwards of 22 to 24deg. of timing. Hope my tuner can figure this out.

 

[VNMOUS1]

Thats what I'm thinking from what I've read so far. I only run 93 octane fuel and have fueled up at several different stations. The timing advance is at 18deg. now and I've read here alot of other people are running upwards of 22 to 24deg. of timing. Hope my tuner can figure this out.

Spark depends on a number of factors. I run 17-18 degrees on my 93 tune and 21-22 psi. 720 rwhp with VMP TVS and our tune.

 

[jbice03]

Yea this crap is way over my head. I've got the stock SC and a stock gauge in the car so as far as I can tell I'm at 15 to 16 PSI. I think thats what my tuner told me it was to.

 

[04SNK390HP]

Do you have a wideband A/F gauge you can monitor or know what A/F ratio is during WOT? What fuel mods do you have?

-Nick

 

[jbice03]

I have A SCT programer, does that read A/F ratio? If not I'm sure my tuner can check that. As far as fuel mods I bought the car used so I am guessing saying its all stock.

 

[gearhead08]

i know your talking about valve clatter a d detonation and such. the one thing that i see is you changed out tb and cai. did you hook everything up correctly? everything seat perfectly? so no unmetered air gets through the cai or tb.

 

[VNMOUS1]

I have A SCT programer, does that read A/F ratio? If not I'm sure my tuner can check that. As far as fuel mods I bought the car used so I am guessing saying its all stock.

No, but if your tuner has a dyno have him run a wideband a/f sample.

 

[jbice03]

i know your talking about valve clatter a d detonation and such. the one thing that i see is you changed out tb and cai. did you hook everything up correctly? everything seat perfectly? so no unmetered air gets through the cai or tb.

They hooked it up at the shop that did the tune but I can check that. Thanks

 

[jbice03]

No, but if your tuner has a dyno have him run a wideband a/f sample.

I'll make sure we do that. Do you think I should take more timing out at 15 psi of boost. Currently at 18 degrees. Thanks

 

[VNMOUS1]

I'll make sure we do that. Do you think I should take more timing out at 15 psi of boost. Currently at 18 degrees. Thanks

No idea. Too many factors. We'd want to see a datalog.

 

[jbice03]

No idea. Too many factors. We'd want to see a datalog.

Ok thanks.

 

[lawdude]

Your 2010 has two knock detectors in the valley under the supercharger (one each bank of cylinders). If you have detonation your engine should be pulling timing. Not that I'm impressed by how quickly the factory system reacts, but it react it does and you can definitely feel it pulling timing.

BTW I'm running Magnapacks and two Magna Flow resonators before the axles. Never at any time adversely affected how the car runs.

 

[jbice03]

Your 2010 has two knock detectors in the valley under the supercharger (one each bank of cylinders). If you have detonation your engine should be pulling timing. Not that I'm impressed by how quickly the factory system reacts, but it react it does and you can definitely feel it pulling timing.

BTW I'm running Magnapacks and two Magna Flow resonators before the axles. Never at any time adversely affected how the car runs.

As soon as I replaced the magnaflow mufflers with the magnapacks the car ran terrible. In the upper RPM range the car would start spitting and popping and lose power. (I suppose it was pulling timimg) As soon as I took it to the guy to have it tuned he checked the plugs and said it looked like it may have been running a little lean but the plugs didn't look all that bad. I replaced the plugs added the JLT CIA, FRPP 65mm throttle body and had him tune it. The car runs much better and since I don't drive the car hard very often I didn't notice the sound I'm hearing now. If I add Lucas octane booster to a tank of gas the sound disappears. I use to have a chevy truck and if I put regular gas instead of premium it would make the same sound this is making when it was under a load.

 

[04SNK390HP]

Sounds like detonation to me............

 

[rotor_powerd]

You need to get the tune revised by a reputable tuner before you spit a rod through the block.

 

[nxhappy]

If I add Lucas octane booster to a tank of gas the sound disappears.

You are getting detonation. DO NOT put the car into boost into you get your tune figured out. You might have a bad tank of gas. I would run the gas as low as possible and fill up at a new station with 93. Then throw in some octane boost (torco). Have your AFR checked, you should see 11.5-11.8 @ WOT. You can also check your spark plugs for detonation. If you see shiny metal.....you are F^ckd.

 

[VNMOUS1]

You need to get the tune revised by a reputable tuner before you spit a rod through the block.

And then there's always that option. :rockon:

 

[jbice03]

You need to get the tune revised by a reputable tuner before you spit a rod through the block.

The tuner I'm using has tuned alot of GT500s and has a good reputation I'm just not going to drive it until we put it back on his dyno and get this figured out.

You are getting detonation. DO NOT put the car into boost into you get your tune figured out. You might have a bad tank of gas. I would run the gas as low as possible and fill up at a new station with 93. Then throw in some octane boost (torco). Have your AFR checked, you should see 11.5-11.8 @ WOT. You can also check your spark plugs for detonation. If you see shiny metal.....you are F^ckd.

I've filled up at several different stations and I don' drive the car hard enough to hear it under normal driving conditions only after about 4500 RPM and up. With the Lucas octane boost the ping went away. Just won't drive it until next week when I take it to be put back on the dyno.