nitrous V quench

Increasing squish velocity might or might not have a positive effect depending on the combustion pressure angle and engine geometry. Excessive squish velocity can over-advance combustion pressure. It can also cause a mixture impingement into the flame front which dramatically changes the burn angle, combustion pressure curve (amplitude and shape), which then produces changes in the instant angular torque locations.


copy/paste

John Myrick wrote:Would it make sense then to not run as much compression on the BBF's as the chevy's do ?

Not in my opinion.....it'd be a crutch to apply a bbc tune to a bbf.

richter69 wrote:66 cc chambers, .110 quench, comeic gaskets, sprayed two kits for over a season w no issues....well i did have a cracked valve cover leak a tad of oil of you wanna call it a "issue".

HeRo, did you use your tune up or a store bought one?

Lem Evans wrote:

richter69 wrote:66 cc chambers, .110 quench, comeic gaskets, sprayed two kits for over a season w no issues....well i did have a cracked valve cover leak a tad of oil of you wanna call it a "issue".

HeRo, did you use your tune up or a store bought one?

Also was this on methanol?

Hero runs gas

Lem Evans wrote:

richter69 wrote:66 cc chambers, .110 quench, comeic gaskets, sprayed two kits for over a season w no issues....well i did have a cracked valve cover leak a tad of oil of you wanna call it a "issue".

HeRo, did you use your tune up or a store bought one?

my tunes

kasse p51 chamber

that .110 quench with a aluminum rod ? thanks

brodix head hunter

c460 heads

Tfs a460

yates c351 GM's kryptonite

the hemi head chamber Ftw........

has anyone noticed the theme of the ford chambers?

10SHOTS wrote:that .110 quench with a aluminum rod ? thanks

I was going to bring up running aluminum rods. On my little A headed deal, we set the ring gaps to handle a larger hit, but I'm just worried about it and have been trying to stay around a 250 or less tune. Static compression, with BME's recommended rod growth info added in, puts me over 14.5:1. The higher compression is needed to help me be competitive in my n/a classes (mud drag truck that runs several classes), so I really don't want it to be a dog. The problem is, when on the jug and pulling 10* timing (2* for every 50hp formula dealio) it seems to want to fall on it's face. So with the quench coming into play on A heads, am I just way off on my tune? It's hard to stop at the end and pull plugs, but after making a pass and quickly getting to an area where i can get towed back to the pit and pull a plug, they seem to look normal. Not bone white, not speckeled or brown/black, just light greyish/ash like a normal run plug.

Box recommended settings are safe safe... If your using a 250 shot, plate? nozzle? multiple nozzles? What fuel and N2O pills are you using? Its probably rich and a little too little on the timing.

kim wrote:Box recommended settings are safe safe...   If your using a 250 shot, plate? nozzle?  multiple nozzles?  What fuel and N2O pills are you using?  Its probably rich and a little too little on the timing.

NOS Big Shot plate, 6lbs fuel psi, dedicated system (flowed before each run using my nifty IS flow tool). Jets are .089n/.073f. Motor is timed at 35* n/a and I pull 10* in the wot switch. I got stupid on the last motor and let a guy talk me into pulling about half on the same tune on the d0ve headed 466 and popped it like a ballon. Guess I'm leary on the much better A headed motor with more compression (14.5:1 now vs 12:1 old)

This string has me re-thinking my situation.  My 545 is a P51 headed, flat top piston 13-1 engine with 6.8 rods.  The pistons are above the deck by .010 and I am running a .056 Cometic (.046 squish).   I have started adding nitrous a bit at a time through an IS fogger and just recently went to a 30 jet.   My intention was to keep climbing up the "jet" ladder as long as the chassis would hold it (looking at a 36 jet)

After reading this, I want some input on how close I might be to melting a piston.  I am no where near the .100 squish some of you are talking about.  Surely, I am not the only one in this same boat.   At what point am I too close to the edge?

edit - I am running base timing of 28* and am pulling 10.5 at WOT. The fuel jet is currently .021 @ 6.5lbs, using a -10 plug and Outlaw 118NOS fuel.

kjett wrote:

kim wrote:Box recommended settings are safe safe...   If your using a 250 shot, plate? nozzle?  multiple nozzles?  What fuel and N2O pills are you using?  Its probably rich and a little too little on the timing.

NOS Big Shot plate, 6lbs fuel psi, dedicated system (flowed before each run using my nifty IS flow tool). Jets are .089n/.073f. Motor is timed at 35* n/a and I pull 10* in the wot switch. I got stupid on the last motor and let a guy talk me into pulling about half on the same tune on the d0ve headed 466 and popped it like a ballon. Guess I'm leary on the much better A headed motor with more compression (14.5:1 now vs 12:1 old)

Never take big leaps with N20. Creep in on your tune... start where you did, suppliers SAFE setting. Then walk into better performance. Usually peole creep out of the fuel pill a little... they tend to supply really rich (or creep up the N20 pill). Watch spark plugs etc... once your "close" with the pill change. Then a little more can be had by adding in a little timing, again, the 2 per is SAFE. With a little less fuel, (or a little more N2O) and 2 to 3 degrees more timing that hit might be a whole other story. But do it in baby steps, not one swift change it all and watch it melt.... shot.

52... and not so long ago I realized the more I learn, the more aware I am that I don't know shit.............

Mine is an alum rod deal

I've read through here twice now.  Is the issue quench, and the rate of burn of high volumes of N2O shocking (detonating) on the combustion side of the piston???

Is the issue cylinder volume and the amount of N20 and fuel attempted to shove in?  

As several have pointed out, almost all the performance ford big block heads are developed with a small combustion chamber, to promote a fast burn cylinder for NA applications.  On the big bore, without quench, and the standard burn rate of stiometic AF ratios and gasoline use, the 4.6+" bore can be detonation prone if using a steel rod etc... 6500 to 7000 RPM and if WE had open chamber heads  (no quench).  The burnt gas pressure would develop fast enough that the remaining cylinder air fuel mixture wouldn't burn linear, but would detonate at once.  Linear burn has cylinder pressures in the 1300 to 1500 psi range, 3800psi+ spike with detonation.

Now aluminum rods, 7000+ RPM, the rod stretch coupled with the higher RPM shock wave above piston.. more air gap less an issue, actually REQUIRED because of the aluminum rod stretch. So aluminum rod combinations get built NA with greater clearance, but still function with "quench" because of rod stretch and the shock wave above the piston.

But we aren't looking at NA performance, we are looking at player N20 loads, 500 to 1500????  loads of N20 and fuel.    Are we running into an issue where the standard fast burn small combustion chamber head from FORD suppliers is just too damn small for the amount of fuel???  The Chevy guys have combustion chambers of 90 to 120+CC in wedge head offerings.   Are the players compensating for small combustion chamber volume and allowing player level fuel in by simply eliminating quench and making the head a large open chamber head with the use of head gaskets and or piston placement?  

N20 will burn damn near anything if there isn't sufficient gasoline available.  Piston tops, gaskets, and even the iron of the block itself.  We have to get enough fuel into the cylinder to add the amount of spray we want to add.  Is the volume of gasoline (and or alcohol) so great that there are issues that damage engines unless we open up the cylinder and allow more volume?  

The neat thing about N2O is although its an oxygenate and will burn anything, its introduction into the cylinder, especially in large volumes cools the cylinder soo much that its actually a detonation inhibitor.  That HP gain by getting the air/fuel super cold in the charge, also prevents it from going Kaboom under pressure. N2O engines are far less likely to destruct from detonation issues, unless timing is just way too damn aggressive.  

My 15 minutes of typing..  I think you could run a tight quench piston to head clearance, cutting flame front travel time, IF we had combustion chambers that were big enough to take the N2O load the players are talking about.  Without a bore scope that could survive combustion, or at the least a cylinder pressure probe.....  and some heads that would allow the use of the same N2O shot and varying the combustion chamber volume...  the answer isn't available.   But, there are people that have proven combinations, and nothing says yes, like success.  So until there is an alternative, the best answer is .100 or more clearance...

Anyone got the bucks to come up with a 150CC combustion chamber wedge head for a 4.9 bore center ford?  Ill bolt em to my block and spray a 1500 shot at em to test the idea.

460Dave wrote:This string has me re-thinking my situation.  My 545 is a P51 headed, flat top piston 13-1 engine with 6.8 rods.  The pistons are above the deck by .010 and I am running a .056 Cometic (.046 squish).   I have started adding nitrous a bit at a time through an IS fogger and just recently went to a 30 jet.   My intention was to keep climbing up the "jet" ladder as long as the chassis would hold it (looking at a 36 jet)

After reading this, I want some input on how close I might be to melting a piston.  I am no where near the .100 squish some of you are talking about.  Surely, I am not the only one in this same boat.   At what point am I too close to the edge?

edit - I am running base timing of 28* and am pulling 10.5 at WOT.  The fuel jet is currently .021 @ 6.5lbs, using a -10 plug and Outlaw 118NOS fuel.

I'm just a want a beeee but if it was mine with that 6.8 rod I would go .070 on squish.....Imo which don't mean much

gmsmkr wrote:

460Dave wrote:This string has me re-thinking my situation.  My 545 is a P51 headed, flat top piston 13-1 engine with 6.8 rods.  The pistons are above the deck by .010 and I am running a .056 Cometic (.046 squish).   I have started adding nitrous a bit at a time through an IS fogger and just recently went to a 30 jet.   My intention was to keep climbing up the "jet" ladder as long as the chassis would hold it (looking at a 36 jet)

After reading this, I want some input on how close I might be to melting a piston.  I am no where near the .100 squish some of you are talking about.  Surely, I am not the only one in this same boat.   At what point am I too close to the edge?

edit - I am running base timing of 28* and am pulling 10.5 at WOT.  The fuel jet is currently .021 @ 6.5lbs, using a -10 plug and Outlaw 118NOS fuel.

I'm just a want a beeee but if it was mine with that 6.8 rod I would go .070 on squish.....Imo which don't mean much

If your going to be a sprayer, get an .080 to .090 head gasket.

kim wrote:

gmsmkr wrote:

460Dave wrote:This string has me re-thinking my situation.  My 545 is a P51 headed, flat top piston 13-1 engine with 6.8 rods.  The pistons are above the deck by .010 and I am running a .056 Cometic (.046 squish).   I have started adding nitrous a bit at a time through an IS fogger and just recently went to a 30 jet.   My intention was to keep climbing up the "jet" ladder as long as the chassis would hold it (looking at a 36 jet)

After reading this, I want some input on how close I might be to melting a piston.  I am no where near the .100 squish some of you are talking about.  Surely, I am not the only one in this same boat.   At what point am I too close to the edge?

edit - I am running base timing of 28* and am pulling 10.5 at WOT.  The fuel jet is currently .021 @ 6.5lbs, using a -10 plug and Outlaw 118NOS fuel.

I'm just a want a beeee but if it was mine with that 6.8 rod I would go .070 on squish.....Imo which don't mean much

If your going to be a sprayer, get an .080 to .090 head gasket.

the cometic gaskets must be one tough sunbitch.......I was always told the weak link between the block and heads is the gasket

I've read through here twice now. Is the issue quench, and the rate of burn of high volumes of N2O shocking (detonating) on the combustion side of the piston???


I never seen any detonation on the plugs....5820 ngk plug 48 nos jet with a 8 jet fuel spread @ 5.5 fuel psi.i pulled 12*@3800 and 12*@5800=24*out initial timing was@27* so leveing 3*in the motor for the rest of the run no moor than 72-7800rpm.yes steel rods at the time with .072 quench using a .062 copper gasket.