Detonation?

[Flynfox]

I know this is always a topic for discussion so I appreciate any help.

My issue with what I believe is detonation is: I have a '93 GT modified with all the bolt-ons including NOS. I only hear the infamous rattling sound if I lug the engine (say 5th gear at 40 mph). My mechanic friend says this is normal because the engine is under load but others tell me different.

I have pretty much determined the problem to come on when engine temp reaches 180 or higher. I have replaced the ECT & ACT to no avail. I don't believe fuel is the problem either. Last dyno tune was 50lbs pressue (vacuum on) and timing @ 12 degrees.

I also cannot pinpoint when the problem started. May have been this way and I just never noticed.

Thanks in advance,
Rob

 

[HISSIN50]

most motors i have ever seen will 'ping' as yours does when being lugged like you describe. it is terribly hard on the bottom end to do that, so i say dont do it. it should be normal (in my experience) for whatever that is worth.
the hotter the motor is, the more likely detonation (or pre-ignition) is to occur. this could be why you can get away with the lugging on a cold (and running richer) motor, but not hot. leanness also leads to detonation. richer mixture has a slight cooling effect and helps to ward off the pings.
just my two cents worth.

 

[Flynfox]

Hissin50 - I've read many of your posts and value your opinion. Therefore, I have another question: I blew a set of heads gaskets not long ago shooting 125 w/10 degrees timimg. When I popped the hood I noticed that the CAI tube had popped out from the MAF. I'm not sure if the gaskets blew because the motor leaned out or from detonation. What do you think?

 

[GT350R]

leanness also leads to detonation. richer mixture has a slight cooling effect and helps to ward off the pings.
just my two cents worth.

I have seen this alot with bypassed EGR's on all different kinds of cars.

Most people have this hang up about lettign hot air get into the engine, BUT they dont realize that teh EGR should only work when under a part htrottle vruise, and shoudl not work , under wide open throttle.. So there is no performace lost.

What happens to cause a lean issue with a disconnected EGR.. The exhaust gas that is allowed to circulate will displace the incoming air, allowing the computer to cut back teh fuel to meet the 14:1 air fuel ratio. When the EGR is plugged or bypassed, the motor is runnign on the verge of lean and if it does not detonate then , it will as soon as you tip in the throttle and the computer advances teh timing.

Just something to consider in yoru quest for gettign rid of the pinging. If you dont look into it, you accelerate the wear on your bottom end , and will eventually kill the motor.

 

[HISSIN50]

Hissin50 - I've read many of your posts and value your opinion. Therefore, I have another question: I blew a set of heads gaskets not long ago shooting 125 w/10 degrees timimg. When I popped the hood I noticed that the CAI tube had popped out from the MAF. I'm not sure if the gaskets blew because the motor leaned out or from detonation. What do you think?

Rob, thanks for the kind words. i will speak about what i know (or think i know). my guess on the headgasket would be that if it blew between two cylinders, you would have compression on one cylinder compress the mixture, shoot the compressed air through the adjacent cylinder (which had an open intake valve). this compressed air could shoot up the intake and cause the inlet tubing at the MAF to pop off.

i think you know this, and are asking if it happend this way, or if the maf popped off and caused the leanness, causing the head gaskets to blow. kind of a chicken or the egg thing to me, as im not well versed in nitrous or MAF (im S.D). i would think if the maf went screwey, if it was bad enough, the car would figure it out and run in open loop. and if the nitrous has its own fuel feed, it should not have leaned out that much,IMHO.

if this what you were asking, and i were to guess, i would say the former (you ran a ton of "boost" through the intake).
this is just my idea. i would welcome others to say if this sounds feasible or take me to school. i dont have a lot of first hand experiences with nitrous (just turbos).

im sure others will have much better info for you. i try to say what i know or sounds plausable, and not say anything when i dont know or dont have a decent idea.

good luck with everything.

P.S. is it all fixed now and you are just wondering (wisely after the last events) about the pinging when lugging? sounds like it; glad to hear you are back up and running. wideband O2's are pricey, but nice to have in your situation. 125 is a healthy shot.

 

[jrichker]

Pinging is caused by a number of things:
1.) Hot spots in the combustion chamber such as carbon deposits from high mileage or excessive oil consumption.
2.) Wrong heat range on the plugs.
3.) Too much initial spark advance.
4.) Lean fuel mixture.
Lean fuel mixture breaks out into several sub categories:
A. Vacuum leaks
B. Air entering the intake without passing through the MAF
C. Failure of the MAF, BAP/MAP (Baro or Manifold Air Pressure, same sensor, different name), ACT (air charge temp), or ECT (engine coolant temp). These should set a code in the computer.
D. Leaking exhaust gases from EGR valve at WOT.
E. Clogged fuel injectors.
F. Fuel injector wiring problems causing injector not to deliver rated flow.
5.) Computer problems: (computer problems are not common like sensor problems)
A. ROM has bad data in fuel or timing table. This should also set a code in the computer.
B. Failure of one or more of the computer's driver transistors for the fuel injectors. No code set on this one.

Have you dumped out the codes?
Here's the link to dump the computer codes with only a jumper wire and the check engine light. I’ve used it for years, and it works great.
See http://www.batauto.com/Ford/
OR
See http://www.dalidesign.com/hbook/eectest.html for more descriptive help
OR
See http://www.mustangworks.com/article...c-iv_codes.html

 

[willys1]

Pinging is caused by a number of things:
1.) Hot spots in the combustion chamber such as carbon deposits from high mileage or excessive oil consumption.
2.) Wrong heat range on the plugs.
3.) Too much initial spark advance.
4.) Lean fuel mixture.
Lean fuel mixture breaks out into several sub categories:
A. Vacuum leaks
B. Air entering the intake without passing through the MAF
C. Failure of the MAF, BAP/MAP (Baro or Manifold Air Pressure, same sensor, different name), ACT (air charge temp), or ECT (engine coolant temp). These should set a code in the computer.
D. Leaking exhaust gases from EGR valve at WOT.
E. Clogged fuel injectors.
F. Fuel injector wiring problems causing injector not to deliver rated flow.
5.) Computer problems: (computer problems are not common like sensor problems)
A. ROM has bad data in fuel or timing table. This should also set a code in the computer.
B. Failure of one or more of the computer's driver transistors for the fuel injectors. No code set on this one.

Have you dumped out the codes?
Here's the link to dump the computer codes with only a jumper wire and the check engine light. I’ve used it for years, and it works great.
See http://www.batauto.com/Ford/
OR
See http://www.dalidesign.com/hbook/eectest.html for more descriptive help
OR
See http://www.mustangworks.com/article...c-iv_codes.html

*** I did #3,, I bought my lx with 18,900 miles,100% stock,and put the timing to 16.Way to much,so I backed it down to 14! Drove it like that for a while,but it still pinged alot,so I got it down to 12! And now it still pings!!!!!!!!!WTF?? How do I correct this?

 

[sleeper89]

willys - it's possible the pointer/balancer aren't lining up properly, i'd back the timing down until it stops pinging. is she still 100% stock?

-steve

 

[HISSIN50]

Willys, sounds like no. 1 is always possible. hard to tell from the outside, but if there are a ton of carbon deposits in there, it can artificially raise the compression a little. more important, the deposits can act as a heat plug and light off whenever they feel like it.
retard the timin some more or try higher octane gas and see what that does. different fuels at different times of the year can make a difference too.
good luck.

 

[willys1]

I dont think theres any build up,its only got 33,000 miles on it.I just installed a screamin demon ign. system today.Didnt drive it though.( Freezing rain today).Im taking it out for a drive tomorrow though.Started it up and let it idle a while.Sounds "real healthy"! I'LL let you know how I make out!

 

[willys1]

I got all the parts put in,waited till today to put in the modular.Runs real good,BUT,,,from a stand still and flooring it,it doesnt ping anymore.(and I advanced it to 14 )But when cruising on the highway doing 70,if I nail it ,,it pings! WTF...So screw it,I put it back to 10 degrees!!

 

[Idwitheld-1`]

I got all the parts put in,waited till today to put in the modular.Runs real good,BUT,,,from a stand still and flooring it,it doesnt ping anymore.(and I advanced it to 14 )But when cruising on the highway doing 70,if I nail it ,,it pings! WTF...So screw it,I put it back to 10 degrees!!

Have you ever had a wide band O2 on the car? Dyno can help diagnose your problem.

 

[jerry beach]

Go out and look at a few plugs. Take some pics if you can. Simple thing that I employ alot. Are they a nice tan color?

 

[makarov]

I agree with hissin. 10* with a shot sounds high to me, as nitrous is just chemical boost. It's not unusual to run 8* base. Run the highest octane you can find, go to an octane booster if you haven't already and drop at least one heat range on the plugs.

Are you running a timing retard box? If not, you're taking a chance because high base or even stock base may be too high, but reduced to 8* base would probably lower your power in normal driving. Make sure you not only run a colder plug, but gap it at .035. You have to remember that the cylinder pressure goes up drastically when you hit the button.

And you have to keep in mind that off nitrous performance will suffer, but it's the price you pay for the additional hp when you want it, otherwise, get ready to pay for blown engine parts (the head gaskets were a warning). If you're running around town pinging without the nitrous, if I were you I wouldn't even get close to that nitrous switch.

 

[willys1]

UUMMM,,maybe you read it wrong,or maybe I misprinted something,but I dont have nitro!! I think I need a dyno tune like idwithheld-1 stated.The motor only has 33,000 miles on it! It shouldnt ping at 14 degrees,with this new ign. system.I always use 93 octane.The pinging has me concerned because its a 93,and it has hyper... pistons.

 

[TT91]

your original post says you do....

"My issue with what I believe is detonation is: I have a '93 GT modified with all the bolt-ons including NOS. I only hear the infamous rattling sound if I lug the engine (say 5th gear at 40 mph). My mechanic friend says this is normal because the engine is under load but others tell me different. "

 

[willys1]

No I didnt,,,sorry, this isnt my thread!