It's all fun and games until someone burns a piston...

[disco stu]

 

[yullose]

I've pulled nitrous motors apart that looked like that.

What happened ?

 

[disco stu]

Not the first time in this car it's happened. I thought I found the problem the first time when I had the injectors flowed. #1 was lazy about 10%. Not tnough to do that IMO but thought that it could have gotten worse by the end of the run. so I replaced the injectors and the harness just to be sure.

It's deja vu. #1 cyl, about the 1000 foot mark 8 seconds into the pass. 11:1 AFR, 20 deg, 22 psi, 60% DC, 14XX EGT's on every hole, 02 correction right on, no knock (a couple 3 degree blips on the 2 step but whatever) ..... sounds pretty safe right? Then temps rise faster than the probe can read it and I pull out a melted plug.

Everything looked great on the dyno. Everything looked great all the 1/8 mile passes. It just all the sudden happens at the big end of the track.

I'm thinking one of the pumps got weak, and cyl 1 is the last piggie on the tit so it burns up first. I know, I know what you are thinking (double pumper?! ) But the hanger has two separate -6 lines Y'd into an Aeromotive filter, -10 to the rail (Saginaw fitting cut off and -10 fitting welded on) and an Accufab reg with the bottom cut off and hole opened up with a -6 return welded on. Fuel pressure was right on on the dyno. And this same fuel system was on my car (different car) and fueled it to 9.60's with good fuel pressure and VE table numbers that jived.

This time I'm putting a proper pump on it, double feeding the rail, and logging FP. But if it's FP dropping all of the sudden then I'll be right back where I'm at. So.... new fuel system it is.

 

[disco stu]

All the other plugs looked fine. Rich, even. Everything looked clean internally. Well, except for #1 of course. :redface:

 

[Boost231]

wow man sorry to hear this. thats one hell of a toasted piston

 

[GNBRETT]

Dohhhhh.....

 

[WSLN 6]

If your O2 correction was fine, why would you suspect the pump?

 

[gnxtc2]

What size injectors?

Billy T.
gnxtc2@aol.com

 

[street6]

valves hit the piston too?

 

[gnxtc2]

I'm thinking one of the pumps got weak, and cyl 1 is the last piggie on the tit so it burns up first. I know, I know what you are thinking (double pumper?! ) But the hanger has two separate -6 lines Y'd into an Aeromotive filter, -10 to the rail (Saginaw fitting cut off and -10 fitting welded on) and an Accufab reg with the bottom cut off and hole opened up with a -6 return welded on. Fuel pressure was right on on the dyno. And this same fuel system was on my car (different car) and fueled it to 9.60's with good fuel pressure and VE table numbers that jived.

This time I'm putting a proper pump on it, double feeding the rail, and logging FP. But if it's FP dropping all of the sudden then I'll be right back where I'm at. So.... new fuel system it is.

Let me see if I'm reading this right........

(2) -6 AN (3/8') coming out of the hanger getting Y'd into the filter. What is the filter made out - paper or stainless mesh?

What size line are you feeding the rail with?

Billy T.
gnxtc2@aol.com

 

[johnplogii]

John, have you flow tested the fuel system on the car? (crank the reg to 67psi or whatever it is at wot and run both pumps to measure how many lbs of fuel it flows) I never did this to mine yet but then again I'm not having the same problem. I believe you flow it for 1 minute, weigh the fuel, multiply by 60 for lbs/hr, then multiply by 2 because the bsfc? # is around .5. That number should tell you how much flywheel hp you can support.

John Plog

 

[yullose]

What fuel was being used ?

 

[bison]

John, have you flow tested the fuel system on the car? (crank the reg to 67psi or whatever it is at wot and run both pumps to measure how many lbs of fuel it flows) I never did this to mine yet but then again I'm not having the same problem. I believe you flow it for 1 minute, weigh the fuel, multiply by 60 for lbs/hr, then multiply by 2 because the bsfc? # is around .5. That number should tell you how much flywheel hp you can support.

John Plog

More like .6 at safe a/f ratios

 

[disco stu]

I havent flowed the pumps but you can bet I will.

It was 3 gallons 112 and 5 gallons 93 and meth with 2 M10 nozzles.

 

[yullose]

I havent flowed the pumps but you can bet I will.

It was 3 gallons 112 and 5 gallons 93 and meth with 2 M10 nozzles.

I put my car on a strict diet of strait Sunoco 116 just to prevent a scenario like this. I don't trust any pump gas or alky at these levels of performance... just one little blip of trouble and you have melted parts on your hands.

 

[boostingirl]

I put my car on a strict diet of strait Sunoco 116 just to prevent a scenario like this. I don't trust any pump gas or alky at these levels of performance... just one little blip of trouble and you have melted parts on your hands.

x2 race gas is a life saver sorry about your motor :frown:

 

[TurboBuRick]

If your O2 correction was fine, why would you suspect the pump?

+2

 

[disco stu]

Right about the race gas, but i should not need it at this boost level and 20 degrees. There is still a problem. Yes, octane probably would have saved my ass but there is still a problem. 11.1, 1400 degrees EGT's is not a recipe for this disaster. 100+ octane and meth should havebeen plenty for this tune IMO.

 

[TurboBuRick]

Did the piston smack the valves?

 

[disco stu]

No.