[screamingchief]

Originally Posted by Torment

1000-1100 NA BBC built for a bottle hit ends up in the 15-1600 range. Few guys at my local track are doing or have done that setup. Some all fogger, others a plate or two and a fogger - different way to get to about the same place. A 632 with a 400cc head and a big hit will go well into the 7's at 34-3500lbs, and go rounds all day long.

That's sounds pretty close to what Maschmeir's camaro is doing,cid is close too IIRC.

Not an entirely uncommon combo for those BBC's.

There were a whole lotta 'em like that when I'd go to the track down in Texas,plenty of 'em around this area too (lotta chi-town racers seem to love the stuff).

Is that close to the limit,yeah sure for most it is,but IMO it's not quite at the ultimate limit.

Still takes a fair amount of skill to make it all work.

Kudos to anyone willing to go for it and put in the hard work & time to do such.



Bret P.

[johnta1]

Anyone use sequential injection on the N2O?

Direct cylinder chamber injection with the N2O?

Who's the go-to-guy to flow your setup?

[Torment]

That's kind of inline with my joke in post 36... but no I'm not aware of anyone. If you can't get it past the damn intake valve, take the intake valve out of the equation Then just meter the air in.

Ive seen Steve Johnson/Induction Solutions get people setup and running hard pretty quick. Money well spent just like getting a mechanical injector system flowed, nozzled and jetted for a boosted program.

[mike leech]

Originally Posted by Elarson

Grocery Getter is 900 hp NA (unported heads) and we spray 600 hp of nitrous. We've tried spraying more with no gain; so we're about at that 70% rule. Bigger head flow is what we need next.

Eric

Are you getting 600 hp more?

[Engo]

Injecting nitrous into a naturally aspirated engine does not change the fact that it is naturally aspirated.
Thus, the absolute limit is to feed the engine with 100% nitrous. That means shutting off the carb/throttlebody completely.
I have never heard of anyone doing that succesfully but I have read about those that have tried and are very close to doing it.

[Elarson]

Originally Posted by mike leech

Are you getting 600 hp more?

Close, but the last few jets sizes didn't seem to do much.

Eric

[goatracer]

Originally Posted by Engo

Injecting nitrous into a naturally aspirated engine does not change the fact that it is naturally aspirated.
Thus, the absolute limit is to feed the engine with 100% nitrous. That means shutting off the carb/throttlebody completely.
I have never heard of anyone doing that succesfully but I have read about those that have tried and are very close to doing it.

This should be clarified, feeding an engine 100% nitrous without adding fuel gains nothing. The point of injecting nitrous is to ad oxygen in order to burn more fuel. Nitrous by itself is not flamable.

Another point of consideration when trying to max out a nitrous combo is being able to control detonation...ie, timing. The more nitrous that's added, the less timing you need. Well, you can only pull so much timing before you change you engine set up.

[Engo]

Originally Posted by goatracer

This should be clarified, feeding an engine 100% nitrous without adding fuel gains nothing. The point of injecting nitrous is to ad oxygen in order to burn more fuel. Nitrous by itself is not flamable.

Another point of consideration when trying to max out a nitrous combo is being able to control detonation...ie, timing. The more nitrous that's added, the less timing you need. Well, you can only pull so much timing before you change you engine set up.

I never said without fuel?

[Elarson]

Running pure nitrous (+ fuel) might not work. (Important.....I said Might).

Nitrous chills to -120 degF when it's released from the jets and flashes from liquid to vapor. But it has to be heated in the combustion chamber to 475 degF to liberate the oxygen. Too much nitrous would probably drop cylinder temp low enough to misfire.

Note that the trend in Pro Mod has been higher compression.....which raises combustion chamber temp.

Also note that when the dentist gives you room temp nitrous, it knocks you out because it's an asphyxiant...no oxygen available for use.

Eric

[goatracer]

Originally Posted by Engo

I never said without fuel?

"...Thus, the absolute limit is to feed the engine with 100% nitrous. That means shutting off the carb/throttlebody completely."

Sorry, I misunderstood your definition of theoretical nitrous limit.

My bad,
Bryan

[goatracer]

Originally Posted by Stan Weiss

In talking about top fuel, they use a hemi combustion chamber. Pontiac heads need to have the combustion chamber softened so that a greater amount of nitrous can be run. Is there still something more that can be done to the combustion chamber design?

Stan

IMO, this statement regarding the softening of the Pontiac chamber should also be clarified. The average Pontiac "open" chamber design can handle quite a bit of nitrous before softening may be considered. Just like the std chambers of the 23* sbc or *24 BBC, its a non-efficient/slow burning chamber that needs more timing to burn the mixtures compared to the more modern chamber design as used on the Tiger heads, which burns faster and requires less timing. The faster burning chamber will need to be softened.

Assuming the tunes are clean and the correct parts are used, you can spray a Pontiac motor with "open chamber" heads ( IE...E-heads) with 500hp before you start getting down into the lower teens for total timing, based on my experience with my 475" Eheaded combo (450hp from 2 kits, 20* total). The chambers on my 505 CV1 combo were slightly more efficient, but spraying 300hp (32 jet), my timing was still 21* with hardly any heat showing on the plugs. Neither heads had the chambers softened.

Now my current combo, a 14* sbc, is the perfect candidate for softening. When attempting to spray the same amount of nitrous as I did with my Pontiac motors, my total timing is 10*-12*. This is the result of having a head with extremely fast burning chamber.


Bryan

[Stan Weiss]

Originally Posted by goatracer

IMO, this statement regarding the softening of the Pontiac chamber should also be clarified. The average Pontiac "open" chamber design can handle quite a bit of nitrous before softening may be considered. Just like the std chambers of the 23* sbc or *24 BBC, its a non-efficient/slow burning chamber that needs more timing to burn the mixtures compared to the more modern chamber design as used on the Tiger heads, which burns faster and requires less timing. The faster burning chamber will need to be softened.

Assuming the tunes are clean and the correct parts are used, you can spray a Pontiac motor with "open chamber" heads ( IE...E-heads) with 500hp before you start getting down into the lower teens for total timing, based on my experience with my 475" Eheaded combo (450hp from 2 kits, 20* total). The chambers on my 505 CV1 combo were slightly more efficient, but spraying 300hp (32 jet), my timing was still 21* with hardly any heat showing on the plugs. Neither heads had the chambers softened.

Now my current combo, a 14* sbc, is the perfect candidate for softening. When attempting to spray the same amount of nitrous as I did with my Pontiac motors, my total timing is 10*-12*. This is the result of having a head with extremely fast burning chamber.


Bryan

Bryan,
By their design are not open chamber heads somewhat "softened"? How much less squish area do they have as compared to a 670 head?

Stan

[goatracer]

Originally Posted by Stan Weiss

Bryan,
By their design are not open chamber heads somewhat "softened"? How much less squish area do they have as compared to a 670 head?

Stan

I would agree that open chamber head designs are "softer".

Below is a pic of the 72cc eheads off of my 475. The chambers are out of the box with the exception of a very minor smoothing of the ridge across the spark plug side. The second pic is the Tiger chamber. It is clear why the "OE style" open chamber of the ehead will be less timing sensitive, therefor is more ready available to handle higher nitrous loads than the more modern/efficient chamber designs.

Bryan

[Stan Weiss]

Originally Posted by goatracer

I would agree that open chamber head designs are "softer".

Below is a pic of the 72cc eheads off of my 475. The chambers are out of the box with the exception of a very minor smoothing of the ridge across the spark plug side. The second pic is the Tiger chamber. It is clear why the "OE style" open chamber of the ehead will be less timing sensitive, therefor is more ready available to handle higher nitrous loads than the more modern/efficient chamber designs.

Bryan

Bryan,
Everything has a trade off. While the Tiger will not take as much nitrous without work done to its chamber it is also a more efficient N/A chamber.

Would you or anyone else knew where the term "softening" started or come from?

Stan

[goatracer]

Originally Posted by Stan Weiss

Bryan,
Everything has a trade off. While the Tiger will not take as much nitrous without work done to its chamber it is also a more efficient N/A chamber.

Would you or anyone else knew where the term "softening" started or come from?

Stan

Well, I wasnt saying anything bad about the tiger, I used it for example. The same chamber mods are done to any head originally designed for high na hp. Be it the tiger, sb2 sbc, yates headed sbf, 18-12* big chief bbc, etc...

Bryan

[Stan Weiss]

Originally Posted by goatracer

Well, I wasnt saying anything bad about the tiger, I used it for example. The same chamber mods are done to any head originally designed for high na hp. Be it the tiger, sb2 sbc, yates headed sbf, 18-12* big chief bbc, etc...

Bryan

Bryan,
I did not take it that way, sorry if my post sounded that way.

Stan

[screamingchief]

Yep,if one really wants to blow some NA engine guys mind,all one has to do is tell the NA engine guy to start asking around the big time nitrous camps about what they run their deck height & head gasket thickness @ LOL.

Yeah sure their CR ranges from like 13:1 to 15:1 as SOP,but they're often running the pistons down -.050",-.075" or even more on some of those "big" nitrous combos.

That too has a "softening" effect as well.

Lotta that goes back to the timing deal,as one can only pull so much till your @ 0° TDC.

That directly affects the combustion speed situation,so yeah many "big dose" nitrous engines dont necessarily like/want really "fast/efficient" chambers as SOP.

So if your close to that "edge" as it relates to the timing "window",soften things up a bit and your timing situation changes for the better.

I'm sure some of the NA engine guys are all like wha,wha,what reading this right now?

Sure NA hp suffers slightly,but they make it all back up when it's on the stuff,and then some.

There are other misc. reasons for that deal too.

Another shameless Monte Smith quote:

Originally Posted by Monte Smith

What you are speaking, is theoretical and is absolutely true, from that sense, but in the real world of making power, "theory" and what "should work", does not always work out that way.

A modern, 850+ cube, 5.300 bore space, nitrous motor, with 4 kits on it, has a pretty large sum of fuel, that needs to be burned. It takes a certain amount of spark lead, to give enough time, to burn that fuel.

The current motor I reference here, it is common practice, for the piston to be .080 in the hole, have a .060 head gasket, an 85ish CC chamber and final static compression, in the 13.5 -14.0 range. Even at that, with water injection, all that quench area, monster cams to get the heat out..........with 4 guns on, these beasts are STILL in low, low, single digits on timing. So are you going to tell me it would be better to tighten the quench, make it burn faster and light the fire AFTER TDC..........don't imagine that will work well.

My tuning philosophy, is ALWAYS, as little timing as possible and I have stated so many times..........however..........you must have enough lead to burn the fuel you are putting in there

Monte

Another Monte tidbit on the same subject:

Originally Posted by Monte Smith

It is not so much the "size" of the chamber........WAY more about shape. When I send heads out to have the chambers "softened", that usually only involves, about 2 CCs of material removal, if that. Not much material removed, but the reshaping, can have a HUGE effect, on how the motor acts.

"Softening" heads seems to be the hot topic. Yes, it is talked about here on a regular basis, but you have to remember, that we talk about a lot of different combos here, from one kit street cars, to 4 kit Pro-Mods. So people read about "softening chambers" on an 850in Pro-Mod motor, or a 12* 632 with 3 guns, or a SB.2, with two kits and they think, they need to soften their heads, as that is the "hot thing" for a nitrous motor. So while many can benefit from the mods, given their intentions, many others, simply don't need it. If you are not sure, always best to talk with someone you trust, than to just take the info from a wed board and run with it.

Monte

Oh,and BTW the reason I like quoting this ^^^^ guy is he's one of the few well known nitrous tuners who'll actually talk about some of this stuff in a public forum,lotta the "other" guys just keep their mouths shut and only give info like this to their paying customers.

And here's a tid bit from that "well known nitrous sbf racer" I vaguely refered to in my earlier post.

I'm posting this vvvv comment as it was from the same group of notes I saved Monte's comments from (which means it's likely from the same thread over there).

Originally Posted by Sam Vincent

Nitrous doesnt need super efficient, fast burning chamber like a highend N/A engine does. it needs a slower smoother burning chamber to help keep control of flame front, not have hot spots/spikes which cause detonation.

this of course is on a heavily dosed nitrous engine. I went from running .060-.070" quench on my smallblock to about .100" quench at same compression ratio and it allowed me to use the three kits without burning it up. or if I ran same two kitsas before, could now run 10-11* timing vs 5-7* on the two kits before, go quicker and get many more passes. infact, we got 54passes before having to freshen our SBF spraying three kits of about 850hp worth of nitrous thru the engine

So yeah,this whole deal can be quite an important aspect of a heavy nitrous combo.

More food for thought.

Bret P.

[goatracer]

Originally Posted by screamingchief

Yep,if one really wants to blow some NA engine guys mind,all one has to do is tell the NA engine guy to start asking around the big time nitrous camps about what they run their deck height & head gasket thickness @ LOL.

Yeah sure their CR ranges from like 13:1 to 15:1 as SOP,but they're often running the pistons down -.050",-.075" or even more on some of those "big" nitrous combos.

That too has a "softening" effect as well.

Lotta that goes back to the timing deal,as one can only pull so much till your @ 0° TDC.

That directly affects the combustion speed situation,so yeah many "big dose" nitrous engines dont necessarily like/want really "fast/efficient" chambers as SOP.

So if your close to that "edge" as it relates to the timing "window",soften things up a bit and your timing situation changes for the better.

I'm sure some of the NA engine guys are all like wha,wha,what reading this right now?

Sure NA hp suffers slightly,but they make it all back up when it's on the stuff,and then some.

There are other misc. reasons for that deal too.

Another shameless Monte Smith quote:



Another Monte tidbit on the same subject:



Oh,and BTW the reason I like quoting this ^^^^ guy is he's one of the few well known nitrous tuners who'll actually talk about some of this stuff in a public forum,lotta the "other" guys just keep their mouths shut and only give info like this to their paying customers.

And here's a tid bit from that "well known nitrous sbf racer" I vaguely refered to in my earlier post.

I'm posting this vvvv comment as it was from the same group of notes I saved Monte's comments from (which means it's likely from the same thread over there).



So yeah,this whole deal can be quite an important aspect of a heavy nitrous combo.

More food for thought.

Bret P.

Yep, the points brought up regarding timing are why I believe the statement made previously about "Pontiac's need to have their chambers softened..." for nitrous use was not entirely true. For the vast majority of Pontiac racers, it's simply not needed.

PS...It's all good Stan.

Bryan

[Stan Weiss]

I guessed at bore, stroke, and rod length. The picture shows the calculated CR. The Graph shows the difference in squish velocity between 0.060" and 0.140" clearance (SqC). Sorry but I only have that function working with metric units.

Stan

[BruceWilkie]

Something to keep in mind NA or nitrous or boosted... for best power you typically need peak combustion pressure to occur @ 15º ATDC. Your fuel/air charge, its resistance to self igniting, compression, compressed charge temp, and chamber design influence when you fire the spark and start the combustion event so that PCP occurs at @ 15º ATDC. PCP much sooner leads to mechanical difficulties and a much later point of PCP cuts power.

Combustion control is a big key to success.