FYI 91 Accord EX 4dr 140k miles, and had complications while using NO2
Okay...I took my head off because I thought I had a blown head gasket...upon removal I discovered that two of my exhaust valves had about 20% of the total surface area gone (think of a pie divided six ways with two slices missing)- I know the percentages don't add up but just go with it please because the center of the valve is still intact because that is where the metal is the thickest
PLEASE IGNORE these ^ symols in the drawing-...these * signify solid metal
_______
\******/
^\****/
^^|**|
There is my text version of a valve to help you visualize what a standard valve looks like
____
\***|_
^\***/
^^|**|
That is what my valve looks like, give or take.

So here is my theory on why it happened...BTW the valve does NOT appear to have broken. If you are familiar with an Oxygen-aceteline torch and how it cuts steel this should make perfect sense(if you do not, here it is the torch heats the steel to a certain temperature(glowing red usually) and then the operator squeezes and pure oxygen goes onto the metal, literally burning it away) so, I think that my valve was quite hot, and when the nitrous oxide sprayed, due to its high oxygen content, It actually burned the valve away which would explain why there are NO signs of the rest of the valve in the engine. This same instance occured in both cylinders one and two to only one of the exhaust valves for each cylinder.
My question is that was this due to there not being enough fuel in the cylinder to mix with the oxygen which allowed the oxygen to make direct contact with the valve?


[Modified by tharptroy, 3:13 AM 2/9/2003]


[Modified by tharptroy, 3:14 AM 2/9/2003]


[Modified by tharptroy, 3:17 AM 2/9/2003]

 

don't know much about nos, but detonation could do that.

 

I've seen what I "think" you are trying to illustrate on air cooled motors, and a couple drag motors buddies tore down. Those instances were usually caused by a severe lean condition on the effected cylinders, incorrect valve lash can also contribute. Those are the ones I have had experience with. You may also have some other factors but that's where I'd start looking.

Additives in your fuel also act as a "coolant" for the exhaust valves (a primary reason it used to have lead in it and that we now have hardened seats and valves) so if it leans out the exhaust valve gets hotter and when you give it a shot of nitrous that makes it that much worse.

 

What should I do about the fuel system then, obviously it needs modification. I am thinking along the lines of a new higher capacity in-tank pump and a new fuel pressure regulator...but I am unsure of how I would hook it up to where it knew to increase pressure when I use nitrous, or do I just increase the pressure in the system and expect it to fix itself? is a higher volume fuel rail in order? AEM maybe?

So, Ill replace all of my exhaust valves for now, should I worry about the intake valves, they were not affected at all, and should I brush off the pistons while I am there? they seem to be a bit dirty


[Modified by tharptroy, 4:19 AM 2/9/2003]

 

you could fill your pistons with ATF fluid till the head is done, the ATF fluid will get the carbon out

 

you have detonation, your valves are screwed, if you had done a leakdown test it would have shown this

 

the only thing that kind of would make me wonder, even in the chemical equation, when N02 is used, oxygen is burnt off and would cause hotter temps, but then again, you are left over with Nitrogen, which would cause the temps to drop drastically...If you were to do fuel upgrades, i'd recommend a better fuel pump, FPR, and get the injectors blueprinted and also an ECU if you dont have one...but thats just my 2 cents.

 

You know now that you've stated that, that is possible where the actual loss of mass occured. Think about it in terms of like the colonial ages when blacksmiths were tempering iron, They made the Iron very hot to where it was glowing red then they would quickly dip it into water to cool the metal at an extremely fast rate causing the Iron to permenantly warp. I believe this to be what happened in this guys case but with aluminum instead of Iron(which has a lower melting point then Iron I believe, correct me if I'm wrong). Then with the added nitrous shot heating the metal even more, then being cooled by the nitrogen at an extremely fast rate, thus causing the aluminum to not only warp but actually break down caused by the dramatic changes in Temp. in such a short period of time. I also believe that the break down was so dramtic that it pretty much turned the aluminum into almost microscopic fragments which was why you couldn't detect any loose chunks of metal near the site, or it could've been then just blown right out with the exhaust gasses. Thats just my theory on the situation, someone please correct me if I'm wrong.


[Modified by Maybomb119, 12:42 AM 2/9/2003]

 

definately lean running when you 'burn' a valve.

get fuel to her with a fuel pump and a fuel pressure reg or something.

 

Thanks guys, I wanted to run that by you just to check...BTW the valve is not made of aluminum, it is too heavy (I just picked it up, it is on my desk). So I will for sure be off of the bottle for a while...until I can get my fuel system upgraded.

 

definately running lean.

a new fuel pump may be overkill. the AEM fuel rail definately is. start with an adjustable FPR, and turn up the pressure. you may need to get bigger injectors, and a VAFC too.

you sould also get a WIDEBAND O2 sensor and guage or a EGT guage to keep an eye on cyl temps and the A/F mix.

 

I guess an overkill would be better than a kill though...I will take my car to a few tuning shops and see waht they reccomend to keep me from running lean.so, I have a random question. would it be okay to clean all of the exhaust valves with a wire brush while I am there?

 

better safe than sorry...

 

BAH damn those lazy bastards...why can't I get valves on a sunday and WOW those head bolts are tight, along with the exhaust bolts. I broke a socket on the head bolts, and Broke or stripped out all of my header bolts. would it be okay just to redrill and tap them? or should I buy a new header?

And a final question. Do you think that the damage caused from running lean would have been worse had I not been using 93octane pump gas with off-road NOS brand octane booster?


[Modified by tharptroy, 10:39 PM 2/9/2003]

 

your theory is interesting and intellegent, but id trust the people on here. like everyone says...it was the fuel system. run to lean and youll get fucked up valves.


denotation = bad.

 

Octane resists detonation, or pre-ignition. basically spontaneous combustion.

yours was most likely caused by leaning out, or not having enough fuel.

being lean increases cyl temps, which increases the chance of detonation.

wether the higher octane saved you a little bit or not is kinda hard to say. it's possible, but lean is lean...

 

Was it by chance cylinders 1 & 2? I would definitely get a an adjustable FPR and gauge. Your stock pressure may be low. Also, how is your timing and did you get cooler spark plugs?

 

YES, it was cylinders one and two. Is there any significance to that, or did a similar situation just happen to you? By gauge, I'll assume you mean a fuel-pressure gauge right? the timing should have been stock but I didn't have it checked and I have NGK one step colder plugs. I will definetly replace the fuel filter as well before I use nitrous again

 

having your timing too far retarded, while on nitrous, can cause burnt exhaust valves. This happens when the powerstroke is still burning when you go to the exhaust stroke. The fuel/air is still burning while its exiting the exhaust valves.

 

Valve lash to tight, timing to advanced..

 

well boyz, thanks for all the advice, I will have my car ready to go on saturday and have found a prospective buyer for my nitrous kit...needless to say, no more squeeze for me i don't want to fork with this crap again...ever

 

Cylinders 1 & 2 are the last to get fuel, and if the pressure is too low, they suffer. Yes you check it with a fuel pressure gauge I paid $40 for my B&M one.