Compression

[340runner]

I doubt you would have much trouble with stock-ish ring gaps as long as you didn't give it too much timing. Overly rich nitrous tunes want more timing for best power, problem with rich is that you will then get into trouble with too much timing if for some reason the fuel system doesn't keep up. Contrary to popular opinion, a "lean and mean" nitrous tune is safer than a rich one.

I used an early warning system to detect damaged hyper pistons and compromised ring seal, a sealed crankcase with a pcv valve drawing crankcase vacuum. If the pcv valve drew less crankcase vacuum at idle after making a pass, I drove it home and leaked it down. Caught many cracked hyper pistons before they took out the entire engine...

View attachment 1840924
View attachment 1840925

A similar system could give you some peace of mind if you wanted to incrementally sneak up on spraying 200hp with unknown ring gaps.

Grant

Where should I measure vacuum from?

 

[weedburner]

I had a cheap diagnostic vacuum gauge velcro'd to the dash, it referenced crankcase vacuum via a fitting screwed into the engine's fuel pump blockoff plate. Crankcase had no vents, so loss of vacuum pulled thru the pcv valve orifice was generally an indication of either new crankcase air leaks or compromised cylinder seal. Cheap/easy way to tell if the engine is hurt.

I've used this system with the same vacuum gauge since 2011, pcv typically pulls 16-18"Hg in the crankcase @ 2500rpm down the highway. With the cracks in this pic the engine still seemed to run fine, but crankcase vacuum was all the way down to 5"Hg on the drive home...

Grant

 

[Curiousyellow71]

I had a cheap diagnostic vacuum gauge velcro'd to the dash, it referenced crankcase vacuum via a fitting screwed into the engine's fuel pump blockoff plate. Crankcase had no vents, so loss of vacuum pulled thru the pcv valve orifice was generally an indication of either new crankcase air leaks or compromised cylinder seal. Cheap/easy way to tell if the engine is hurt.

I've used this system with the same vacuum gauge since 2011, pcv typically pulls 16-18"Hg in the crankcase @ 2500rpm down the highway. With the cracks in this pic the engine still seemed to run fine, but crankcase vacuum was all the way down to 5"Hg on the drive home...

View attachment 1840980

Grant

That cracked piston doesn't make we want to run cast or hypereutectic's!!
Wow! That almost ended up in the pan!

 

[340runner]

That cracked piston doesn't make we want to run cast or hypereutectic's!!
Wow! That almost ended up in the pan!

And crazy how he said he is able to drive home with those cracks, wouldn't have known without telling the crankcase vaccum

 

[weedburner]

That cracked piston doesn't make we want to run cast or hypereutectic's!!
Wow! That almost ended up in the pan!

At the time, I had an obsession with seeing how far I could push those cheap rebuilder hypers. I was putting $800/set Stock Eliminator ring packages on $95/set pistons

Grant

 

[Cop car wagon]

Man, I love the cracked hyperutectic pictures.
Like I said, in my first post.
"All I could find with a 340 style dome were cast or hyperutectic, which I won't run."
The endurance motor I'm building has forged that are 550gr.

 

[340runner]

Got the book, read it a good bit, and I will say it definitely opened my eyes on the theory side of things, especially how it's not the nitrous but the fuel that makes power. The thing directly with the book is the tunes for the jets are very rich from almost everything I've heard. They're straight from the NOS powershot tunes, and the fuel is a good bit larger than the nitrous jets.

Another thing is, why do people recommend 2 fuel pumps for reliability? If the fuel pump breaks with only one, the motor is likely toast due to running lean. On the other hand though, if you have two wouldn't if either one breaks the motor is still toast? If the fuel pump for the nitrous breaks it's going to run lean obviously, but if the fuel pump for the carb breaks isn't it still going to lean out, and at a much larger magnitude since it'll still run and take in air because of the fuel solenoid, but it will have all the air from the carb so it'll lean out?

 

[BSB67]

theory side of things, especially how it's not the nitrous but the fuel that makes power.

No. Not sure you meant what you said here, or if you were simply being brief.

Fuel and oxygen make power. Air is 19.5% oxygen. N20 is about 35% oxygen, Additional fuel is needed to combust with the additional O2 the N2O provides. This results in more energy/power.

 

[340runner]

No. Not sure you meant what you said here, or if you were simply being brief.

Fuel and oxygen make power. Air is 19.5% oxygen. N20 is about 35% oxygen, Additional fuel is needed to combust with the additional O2 the N2O provides. This results in more energy/power.

yes, I was being brief here, I know how it makes power, I'm in high school chemistry right now and went over combustion reactions just like you did in high school. I know you need both, and I'm not sure how to really word it without just writing down the whole book word-for-word, but he basically explains how it's really the fuel that is the thing that's providing the potential energy in the whole equation, the nitrous is really just cold o2 dense air and is a oxidiser. Thus, when one melts a piston, they dont go and blame nitrous instead of their crap tuning ability. Again, I could go into how the bond enthalpy in fuel actually provides the energy to turn the motor, but I don't want to go into more chemistry crap. He explains in the book better how to tune, and what direction to take when you read plugs. As I said, that's a terrible explanation because you really need to read the book to understand and grasp it.

 

[RemCharger]

Got the book, read it a good bit, and I will say it definitely opened my eyes on the theory side of things, especially how it's not the nitrous but the fuel that makes power. The thing directly with the book is the tunes for the jets are very rich from almost everything I've heard. They're straight from the NOS powershot tunes, and the fuel is a good bit larger than the nitrous jets.

Another thing is, why do people recommend 2 fuel pumps for reliability? If the fuel pump breaks with only one, the motor is likely toast due to running lean. On the other hand though, if you have two wouldn't if either one breaks the motor is still toast? If the fuel pump for the nitrous breaks it's going to run lean obviously, but if the fuel pump for the carb breaks isn't it still going to lean out, and at a much larger magnitude since it'll still run and take in air because of the fuel solenoid, but it will have all the air from the carb so it'll lean out?

yes, I was being brief here, I know how it makes power, I'm in high school chemistry right now and went over combustion reactions just like you did in high school. I know you need both, and I'm not sure how to really word it without just writing down the whole book word-for-word, but he basically explains how it's really the fuel that is the thing that's providing the potential energy in the whole equation, the nitrous is really just cold o2 dense air and is a oxidiser. Thus, when one melts a piston, they dont go and blame nitrous instead of their crap tuning ability. Again, I could go into how the bond enthalpy in fuel actually provides the energy to turn the motor, but I don't want to go into more chemistry crap. He explains in the book better how to tune, and what direction to take when you read plugs. As I said, that's a terrible explanation because you really need to read the book to understand and grasp it.

Wow. Good for you, you're a very smart young man.keep reading. That's the old foundation of knowledge

 

[340runner]

Well, I certainly try to build knowledge, instead of going in blind to something you can't mess up if you want to keep everything intact.

Wow. Good for you, you're a very smart young man.keep reading. That's the old foundation of knowledge

 

[weedburner]

Another thing is, why do people recommend 2 fuel pumps for reliability? If the fuel pump breaks with only one, the motor is likely toast due to running lean. On the other hand though, if you have two wouldn't if either one breaks the motor is still toast? If the fuel pump for the nitrous breaks it's going to run lean obviously, but if the fuel pump for the carb breaks isn't it still going to lean out, and at a much larger magnitude since it'll still run and take in air because of the fuel solenoid, but it will have all the air from the carb so it'll lean out?

It's too much timing/detonation that kills a nitrous engine, not running lean. When you start out with an outdated fat/lazy N/F tune and then optimize the timing to that rich tune, you will then have too much timing if something goes wrong and the fuel system can't keep up.

Start off with a proper lean N/F tune and safe timing, then pull even more timing out for the next pass just to see if the car slows down. This verifies which side of optimum timing you are starting out from, far safer to sneak up on optimum timing rather than blindly starting out optimum and then going too far.

Here's a Steve Johnson post I saved from the YB, modern N/F ballpark tunes for a plate...

Grant

 

[340runner]

It's too much timing/detonation that kills a nitrous engine, not running lean. When you start out with an outdated fat/lazy N/F tune and then optimize the timing to that rich tune, you will then have too much timing if something goes wrong and the fuel system can't keep up.

Start off with a proper lean N/F tune and safe timing, then pull even more timing out for the next pass just to see if the car slows down. This verifies which side of optimum timing you are starting out from, far safer to sneak up on optimum timing rather than blindly starting out optimum and then going too far.

Here's a Steve Johnson post I saved from the YB, modern N/F ballpark tunes for a plate...
View attachment 1842113

Grant

Okay, that's making more sense and is definitely a better safeguard against failure of parts. Leaning out isn't killing it, detonation is, if it leans out because of a failure of something but the timing isnt too far advanced, just means loss of power

 

[Mebsuta]

I might put the Isky cam back in mine to attract gurls.