Highest compression on pump gas?
Adrenaline-
Nitrous is not the same as a super/turbo charger. A supercharger or turbo compresses the incoming air, which allows for more fuel to be added, with the same AFR. With nitrous injection, there is no compression of the incoming air, only added oxygen from the nitrous. This also allows for more fuel to be added. The fuel/oxygen mix is what contains the energy to make power. The cylinder pressure in a turbo/supercharged engine is much higher before compression, due to the incoming air already being at a pressure higher than atmosheric pressure. You can think of this as effectively increasing the compression ratio. With nitrous, the cylinder pressure prior to combustion is not any different than without the nitrous, it does not effectively increase the compression ratio. Increasing compression ratio increases engine efficiency, therefore increasing power.
Therefore, while using nitrous, an increase in compression ratio will make more power and not increase cylinder pressure to dangerously high levels. With increased compression there needs to be an increase in fuel octane, to prevent pre-ignition. This need is increased by the use of nitrous, which makes the mixture more volatile due to the increased amount of oxygen.
I would suggest 11.0:1 or so, but I am no expert.
Nitrous is not the same as a super/turbo charger. A supercharger or turbo compresses the incoming air, which allows for more fuel to be added, with the same AFR. With nitrous injection, there is no compression of the incoming air, only added oxygen from the nitrous. This also allows for more fuel to be added. The fuel/oxygen mix is what contains the energy to make power. The cylinder pressure in a turbo/supercharged engine is much higher before compression, due to the incoming air already being at a pressure higher than atmosheric pressure. You can think of this as effectively increasing the compression ratio. With nitrous, the cylinder pressure prior to combustion is not any different than without the nitrous, it does not effectively increase the compression ratio. Increasing compression ratio increases engine efficiency, therefore increasing power.
Therefore, while using nitrous, an increase in compression ratio will make more power and not increase cylinder pressure to dangerously high levels. With increased compression there needs to be an increase in fuel octane, to prevent pre-ignition. This need is increased by the use of nitrous, which makes the mixture more volatile due to the increased amount of oxygen.
I would suggest 11.0:1 or so, but I am no expert.
Originally Posted by XAntivenomX
Adrenaline-
Nitrous is not the same as a super/turbo charger. A supercharger or turbo compresses the incoming air, which allows for more fuel to be added, with the same AFR. With nitrous injection, there is no compression of the incoming air, only added oxygen from the nitrous. This also allows for more fuel to be added. The fuel/oxygen mix is what contains the energy to make power. The cylinder pressure in a turbo/supercharged engine is much higher before compression, due to the incoming air already being at a pressure higher than atmosheric pressure. You can think of this as effectively increasing the compression ratio. With nitrous, the cylinder pressure prior to combustion is not any different than without the nitrous, it does not effectively increase the compression ratio. Increasing compression ratio increases engine efficiency, therefore increasing power.
Therefore, while using nitrous, an increase in compression ratio will make more power and not increase cylinder pressure to dangerously high levels. With increased compression there needs to be an increase in fuel octane, to prevent pre-ignition. This need is increased by the use of nitrous, which makes the mixture more volatile due to the increased amount of oxygen.
I would suggest 11.0:1 or so, but I am no expert.
Nitrous is not the same as a super/turbo charger. A supercharger or turbo compresses the incoming air, which allows for more fuel to be added, with the same AFR. With nitrous injection, there is no compression of the incoming air, only added oxygen from the nitrous. This also allows for more fuel to be added. The fuel/oxygen mix is what contains the energy to make power. The cylinder pressure in a turbo/supercharged engine is much higher before compression, due to the incoming air already being at a pressure higher than atmosheric pressure. You can think of this as effectively increasing the compression ratio. With nitrous, the cylinder pressure prior to combustion is not any different than without the nitrous, it does not effectively increase the compression ratio. Increasing compression ratio increases engine efficiency, therefore increasing power.
Therefore, while using nitrous, an increase in compression ratio will make more power and not increase cylinder pressure to dangerously high levels. With increased compression there needs to be an increase in fuel octane, to prevent pre-ignition. This need is increased by the use of nitrous, which makes the mixture more volatile due to the increased amount of oxygen.
I would suggest 11.0:1 or so, but I am no expert.
Exactly which is why 90 percent of the nitrous motors on this board are 10:5:1 or higher if they arent stock bottom ends...
91 octane here and 11:1 compression. Milled AFR's and .040" Cometic gaskets, TSP 233/239 112LSA cam. I plan to shoot a 150 wet shot.
Adrenaline-
The combustion chamber in the LSx heads is miles ahead of the old Vortec heads and other performance heads. In addition the beauty of fuel injection allows for abnormally high compression on 91 octane and a big cam with lots of duration bleeds off cylinder pressure. I'm sure that individual coil packs don't hurt either. GM really did their homework when building this engine.
After building 5 Buick Grand National engines and finally tearing apart an LS1... The LSx technology (reusable gaskets, oil pump driven off the crank snout, cross bolted main caps, good flowing factory casting heads with interesting port designs, composite intake (helps to lower intake temps over long periods of time) and other great features) is the best engine I've come across in making things more simple in an engine for a good reason. No complex 4 valves per cylinder, multiple cams, timing chains etc.
When there are hundreds of LSx people running 11:1+ on 91/93 octane I'd say it is safe to assume it can be done... even if a book says it can't. Carb'd setups and EFI yield different results when pushing the compression envelope on pump gas. The beauty of computer controlled engines.
-Mark
Adrenaline-
The combustion chamber in the LSx heads is miles ahead of the old Vortec heads and other performance heads. In addition the beauty of fuel injection allows for abnormally high compression on 91 octane and a big cam with lots of duration bleeds off cylinder pressure. I'm sure that individual coil packs don't hurt either. GM really did their homework when building this engine.
After building 5 Buick Grand National engines and finally tearing apart an LS1... The LSx technology (reusable gaskets, oil pump driven off the crank snout, cross bolted main caps, good flowing factory casting heads with interesting port designs, composite intake (helps to lower intake temps over long periods of time) and other great features) is the best engine I've come across in making things more simple in an engine for a good reason. No complex 4 valves per cylinder, multiple cams, timing chains etc.
When there are hundreds of LSx people running 11:1+ on 91/93 octane I'd say it is safe to assume it can be done... even if a book says it can't. Carb'd setups and EFI yield different results when pushing the compression envelope on pump gas. The beauty of computer controlled engines.
-Mark
TECH Senior Member
Joined: Mar 2004
Posts: 14,620
Likes: 17
From: BFE
Originally Posted by XAntivenomX
Adrenaline-
Nitrous is not the same as a super/turbo charger. A supercharger or turbo compresses the incoming air, which allows for more fuel to be added, with the same AFR. With nitrous injection, there is no compression of the incoming air, only added oxygen from the nitrous. This also allows for more fuel to be added. The fuel/oxygen mix is what contains the energy to make power. The cylinder pressure in a turbo/supercharged engine is much higher before compression, due to the incoming air already being at a pressure higher than atmosheric pressure. You can think of this as effectively increasing the compression ratio. With nitrous, the cylinder pressure prior to combustion is not any different than without the nitrous, it does not effectively increase the compression ratio. Increasing compression ratio increases engine efficiency, therefore increasing power.
Therefore, while using nitrous, an increase in compression ratio will make more power and not increase cylinder pressure to dangerously high levels. With increased compression there needs to be an increase in fuel octane, to prevent pre-ignition. This need is increased by the use of nitrous, which makes the mixture more volatile due to the increased amount of oxygen.
I would suggest 11.0:1 or so, but I am no expert.
Nitrous is not the same as a super/turbo charger. A supercharger or turbo compresses the incoming air, which allows for more fuel to be added, with the same AFR. With nitrous injection, there is no compression of the incoming air, only added oxygen from the nitrous. This also allows for more fuel to be added. The fuel/oxygen mix is what contains the energy to make power. The cylinder pressure in a turbo/supercharged engine is much higher before compression, due to the incoming air already being at a pressure higher than atmosheric pressure. You can think of this as effectively increasing the compression ratio. With nitrous, the cylinder pressure prior to combustion is not any different than without the nitrous, it does not effectively increase the compression ratio. Increasing compression ratio increases engine efficiency, therefore increasing power.
Therefore, while using nitrous, an increase in compression ratio will make more power and not increase cylinder pressure to dangerously high levels. With increased compression there needs to be an increase in fuel octane, to prevent pre-ignition. This need is increased by the use of nitrous, which makes the mixture more volatile due to the increased amount of oxygen.
I would suggest 11.0:1 or so, but I am no expert.
But soon I leaned the difference.
11 & 7 Second Clubs
Joined: Oct 2004
Posts: 1,299
Likes: 0
From: Motorhome, Freeways, Truckstops, Pits
Originally Posted by tim99ws6
I think i'm gonna shoot for around 11.5 compression. I am hoping this will help a more aggressive cam be more useable on power under the curve. Is this a valid thought? Am i going in the right direction?
Tim
Tim
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8 second mod
iTrader: (37)
Joined: Nov 2002
Posts: 17,879
Likes: 1
From: East Side Performance! mASShole
My tuner runs 700 plus rwhp on pump 93 octain. with a Super charger, he starts off with 9-1 CR, now add 16 psi and his CR turns up to around 15-1/17-1 so he keeps timming down a scunch.
On the gas, if you start with 11-1 cr and spray it, the CR never changes, you motor just turns into a pump. so if your cam is perfect and your tune is correct, CR should be able to be run at 11-1 to 12-1 without an issue. and for safe messure, when racing throw a couple gallons in of race gas.
FWIW, my car is around 13-1, i run race gas, and 117 in my stand alone. when i run on the street to car shows and stuff and i know i will not spray, im running 93 octain pump gas with no issues. i dont do it much, but i do it.
Not sure who is putting the specs to this motor/cam ect, but be sure they know what they are doing, not just talking.
as you can see from a few of theses posts, anyone can talk like they know somthing.
On the gas, if you start with 11-1 cr and spray it, the CR never changes, you motor just turns into a pump. so if your cam is perfect and your tune is correct, CR should be able to be run at 11-1 to 12-1 without an issue. and for safe messure, when racing throw a couple gallons in of race gas.
FWIW, my car is around 13-1, i run race gas, and 117 in my stand alone. when i run on the street to car shows and stuff and i know i will not spray, im running 93 octain pump gas with no issues. i dont do it much, but i do it.
Not sure who is putting the specs to this motor/cam ect, but be sure they know what they are doing, not just talking.
as you can see from a few of theses posts, anyone can talk like they know somthing.
Originally Posted by PREDATOR-Z
Adrenaline,
Quit acting like you know it all Bro. He said (93 pump gas) and I gave him my answer.
N2O use is very tune dependent, so of course you have to reduce timing and add fuel accordingly while monitoring with data logger.
Do you even have an LS1?
Juicers all know that the higher CR the more power. Of course higher CR demands higher Octane.Quench plays a big role to.
Here I have 98 Octane premium and I can shoot 200 dry on stock motor without even pulling timing. Yes 28.8* with a 12.6 AFR and I could lean it a bit.
CR 10.4x
So please try to relax, trade info, learn a bit but avoid bashing, and acting like you are King of all knowledge.
Some BBC at the track here are running 14:1 and shooting 400 rwhp shot DP.
Quit acting like you know it all Bro. He said (93 pump gas) and I gave him my answer.
N2O use is very tune dependent, so of course you have to reduce timing and add fuel accordingly while monitoring with data logger.
Do you even have an LS1?
Juicers all know that the higher CR the more power. Of course higher CR demands higher Octane.Quench plays a big role to.
Here I have 98 Octane premium and I can shoot 200 dry on stock motor without even pulling timing. Yes 28.8* with a 12.6 AFR and I could lean it a bit.
CR 10.4x
So please try to relax, trade info, learn a bit but avoid bashing, and acting like you are King of all knowledge.
Some BBC at the track here are running 14:1 and shooting 400 rwhp shot DP.
Edit: missed the last page.
Last edited by Tiger2o69; Apr 13, 2005 at 03:11 PM.
[QUOTE=Noyzee]
FWIW, my car is around 13-1, i run race gas, and 117 in my stand alone. when i run on the street to car shows and stuff and i know i will not spray, im running 93 octain pump gas with no issues. i dont do it much, but i do it.
My setup is alot like this but on a lt1 stroker with 11:5:1 and will be putting c16 in my stand alone.. My cam is a 236/245 114lsa .569/.580
FWIW, my car is around 13-1, i run race gas, and 117 in my stand alone. when i run on the street to car shows and stuff and i know i will not spray, im running 93 octain pump gas with no issues. i dont do it much, but i do it.
My setup is alot like this but on a lt1 stroker with 11:5:1 and will be putting c16 in my stand alone.. My cam is a 236/245 114lsa .569/.580
TECH Resident
Joined: Dec 2004
Posts: 845
Likes: 0
From: K-W, Ontario
What a ******* joke.
My car is naturally aspirated using 9.7:1 compression and running 12's this year with this 1.6 rockers and new exhaust.
http://www.gmthunder.com/main/module...&p=44981#44981
The last motor ran 13.2 @ 105 with 248 HP at the wheel, street tires and
3761 lbs race weight. But you dumb punks forget to include that.
http://gmthunder.com/tino/dynograph.jpg
My 1st gen SB is surpassing your LS1. FWIW, with a slick, I'm destined for mid
12's ALL MOTOR. Ever wonder how that works with only 248 HP at the wheel smart guys?
But why do you people with no engine building skills always attack facts outside
of the debate?
What difference does it make what motor I have in my car, or how fast it runs?
That is such a typical reply for an internet car forum bench racer!
TY_TY13 posted some information and highlighted a paragrah that you all
need to read.
Get your head out of your asses and read the damn links! You can't run
93 pump gas with tons of nitrous and be effective.
You NEED to drop the compression, or resort to higher octane fuel.
What part of this do you not understand?
Let's take a little poll since the **** talkers are not smart enough to post cam specs:
Engine 1:
10.5:1 comrpession, DCR 8.5, 100 shot of nitrous, 93 pump gas, timing -4
Engine 2
9:1 compression, DCR 8, 250 shot of nitrous, 92 pump gas, timing -2
Engine 3
11.5:1 compression, DCR 8, 100 shot of nitrous, 93 pump gas, timing -2
Engine 4
11.5:1 compression, DCR 8.5, 250 shot of nitrous, 93 pump gas, timing -8
Which engine is stronger?
Which engine is not likely to work?
Which engine is just average?
Which engine is weakest?
SOrry, I'm not supposed to reply because I got owned?
Are you fools still sitting on your *** agreeing with each other becasue you're
all internet friends, or have you researched and called some engine tuners yet?
My car is naturally aspirated using 9.7:1 compression and running 12's this year with this 1.6 rockers and new exhaust.
http://www.gmthunder.com/main/module...&p=44981#44981
The last motor ran 13.2 @ 105 with 248 HP at the wheel, street tires and
3761 lbs race weight. But you dumb punks forget to include that.
http://gmthunder.com/tino/dynograph.jpg
My 1st gen SB is surpassing your LS1. FWIW, with a slick, I'm destined for mid
12's ALL MOTOR. Ever wonder how that works with only 248 HP at the wheel smart guys?
But why do you people with no engine building skills always attack facts outside
of the debate?
What difference does it make what motor I have in my car, or how fast it runs?
That is such a typical reply for an internet car forum bench racer!
TY_TY13 posted some information and highlighted a paragrah that you all
need to read.
Get your head out of your asses and read the damn links! You can't run
93 pump gas with tons of nitrous and be effective.
You NEED to drop the compression, or resort to higher octane fuel.
What part of this do you not understand?
Let's take a little poll since the **** talkers are not smart enough to post cam specs:
Engine 1:
10.5:1 comrpession, DCR 8.5, 100 shot of nitrous, 93 pump gas, timing -4
Engine 2
9:1 compression, DCR 8, 250 shot of nitrous, 92 pump gas, timing -2
Engine 3
11.5:1 compression, DCR 8, 100 shot of nitrous, 93 pump gas, timing -2
Engine 4
11.5:1 compression, DCR 8.5, 250 shot of nitrous, 93 pump gas, timing -8
Which engine is stronger?
Which engine is not likely to work?
Which engine is just average?
Which engine is weakest?
SOrry, I'm not supposed to reply because I got owned?
Are you fools still sitting on your *** agreeing with each other becasue you're
all internet friends, or have you researched and called some engine tuners yet?
TECH Resident
Joined: Dec 2004
Posts: 845
Likes: 0
From: K-W, Ontario
For those claiming to have more than 12:1 compression on pump gas,
let's see your engine specs.
Did you actually cc the head, or did you use an online calculator to figure
the compression ratio
Maybe you used that wonderfull program uhhhh...ummm...Desktop Dyno 2000?
Put it down in writing and I'll do some CR math for you and post it.
let's see your engine specs.
Did you actually cc the head, or did you use an online calculator to figure
the compression ratio
Maybe you used that wonderfull program uhhhh...ummm...Desktop Dyno 2000?
Put it down in writing and I'll do some CR math for you and post it.
TECH Resident
Joined: Dec 2004
Posts: 845
Likes: 0
From: K-W, Ontario
With nitrous, the cylinder pressure prior to combustion is not any different than without the nitrous, it does not effectively increase the compression ratio. Increasing compression ratio increases engine efficiency, therefore increasing power.
So nitrous doesn't increase cylinder pressure huh?
And all of you beleive that too?
Wow, this thread is getting stupid.
Is there ANYONE out there reading this with a half a brain that can read the
links and back me up?
Is there an engine tuner on this board that can back me up?
So I'm saying initially on page one, that 11:1 is about as high as you shuold
go with pump gas and 100 shot of nitrous...but now I'm owned because...
everyone said it afterwards?
I see how this works. I just can win because I worked in a speed shop and
don't have an LS1.
WHat if I run down the road to the local car dealer and pickup a used 'Bird,
or Camaro with an LS1. Will that make everything I typed true?
TECH Resident
Joined: Dec 2004
Posts: 845
Likes: 0
From: K-W, Ontario
Damn , you guys made me so mad, I had to waste my time to search for more
info.
Here's ANOTHER credible link to discredit all of you guys posting BS:
Have a read, it's good stuff!
http://www.noswizard.com/technical.php
I really like the part where they say, "adequate to fire a standard inlet charge effectively, never mind a charge at the higher pressures caused by injecting N2O. However it is easy to understand that as the pre-combustion chamber pressures rise due to higher volumes of inlet charge, the spark strength required to jump a fixed plug gap is also going to rise"
Oops, looks like a few of you got owned there huh?
Oh wait, here's another good quote regarding low compression, "e.g. you could run normally on lower octane fuel and put your engine under less stress), plus it brings the added advantage of raising the power potential of the nitrous system before problems are encountered. "
Geez, that's FOUR unique links and still nobody can prove me wrong.
I can't wait to read the replies when I get home tonight. Should make for
some good laughs.
(Again, sorry for adding four posts in a row. I have a huge internet image to
protect don't you know).
I love it when I'm right.
info.
Here's ANOTHER credible link to discredit all of you guys posting BS:
Have a read, it's good stuff!
http://www.noswizard.com/technical.php
I really like the part where they say, "adequate to fire a standard inlet charge effectively, never mind a charge at the higher pressures caused by injecting N2O. However it is easy to understand that as the pre-combustion chamber pressures rise due to higher volumes of inlet charge, the spark strength required to jump a fixed plug gap is also going to rise"
Oops, looks like a few of you got owned there huh?
Oh wait, here's another good quote regarding low compression, "e.g. you could run normally on lower octane fuel and put your engine under less stress), plus it brings the added advantage of raising the power potential of the nitrous system before problems are encountered. "
Geez, that's FOUR unique links and still nobody can prove me wrong.
I can't wait to read the replies when I get home tonight. Should make for
some good laughs.
(Again, sorry for adding four posts in a row. I have a huge internet image to
protect don't you know).
I love it when I'm right.
I run my LS motor at 12:1 with a 200 shot on 93 octane. When tuning it for the spray 6 degrees of timing were taken out which cost me less than 10 hp at peak on a motor run. I am not an engine builder and I don't want to go around searching for why it works. I know of many other ls1's setup this way. While I guess 10,000 lemmings can be wrong. I think I will listen to the advice of people who own ls1 cars and tune them on a daily basis. Now before you blow a head gasket Adrenaline_Z; I am not saying you are wrong I am just stating what works in my car and some of my friends cars. To settle this bs two of you could always have an engine build off and see what setup was better for the ls1 otherwise this thread may never stop. 
TECH Resident
Joined: Dec 2004
Posts: 845
Likes: 0
From: K-W, Ontario
I'm not going to blow a head gasket.
I think some people are mistaking my reply to say:
"reduce compression to run any amount of nitrous"
That is NOT what I'm saying.
If people were to read my very first post, I clearly stated that 11:1 with
pump gas is about the max before getting into detonation issues.
Check the knock counts if you're up around 11:1 SCR, and see if the motor
is giving full advance at wide open (this leaving about 8-8.5 DCR with IVC).
Being all aluminum, and the chamber design, the LS1 can probably handle
a touch more compression. I have no problem with that either.
For those that are telling Tim to rise over 11-11.5:1 on pump gas and spray
100 shot of N20 are dreaming.
That's not the best setup to run.
My position is this:
To run nitrous effectively, you need to consider the extra charge volume.
Much to everyone's surprise, nitrous adds a **** load of cylinder pressure.
The only saving grace is the chamber temperatures drop...so that may allow
slightly higher static and dynamic compressions than non intercooled boost.
Why? Because compression adds heat, heat can trigger early ignition.
When you stuff extra charge into a compression stroke (N20, boost), the
fuel becomes more prone to pre-ignition because of the higher charge
volume getting squeezed into that very same chamber size.
But that doesn't change the FACT that reducing the DCR/SCR and stuffing
more nitrous per compression stroke increases power.
Again, what makes more sense:
Engine 1:
10.5:1 comrpession, DCR 8.5, 100 shot of nitrous, 93 pump gas, timing -4
OR
Engine 2
9:1 compression, DCR 8, 250 shot of nitrous, 92 pump gas, timing -2
Now read back to all of those people who said, "Nitrous isn't like boost,
it doesn't change the cylinder pressure, or effective compression" and laugh at them.
Clearly, we are dealing with magazine mechanics here.
I think some people are mistaking my reply to say:
"reduce compression to run any amount of nitrous"
That is NOT what I'm saying.
If people were to read my very first post, I clearly stated that 11:1 with
pump gas is about the max before getting into detonation issues.
Check the knock counts if you're up around 11:1 SCR, and see if the motor
is giving full advance at wide open (this leaving about 8-8.5 DCR with IVC).
Being all aluminum, and the chamber design, the LS1 can probably handle
a touch more compression. I have no problem with that either.
For those that are telling Tim to rise over 11-11.5:1 on pump gas and spray
100 shot of N20 are dreaming.
That's not the best setup to run.
My position is this:
To run nitrous effectively, you need to consider the extra charge volume.
Much to everyone's surprise, nitrous adds a **** load of cylinder pressure.
The only saving grace is the chamber temperatures drop...so that may allow
slightly higher static and dynamic compressions than non intercooled boost.
Why? Because compression adds heat, heat can trigger early ignition.
When you stuff extra charge into a compression stroke (N20, boost), the
fuel becomes more prone to pre-ignition because of the higher charge
volume getting squeezed into that very same chamber size.
But that doesn't change the FACT that reducing the DCR/SCR and stuffing
more nitrous per compression stroke increases power.
Again, what makes more sense:
Engine 1:
10.5:1 comrpession, DCR 8.5, 100 shot of nitrous, 93 pump gas, timing -4
OR
Engine 2
9:1 compression, DCR 8, 250 shot of nitrous, 92 pump gas, timing -2
Now read back to all of those people who said, "Nitrous isn't like boost,
it doesn't change the cylinder pressure, or effective compression" and laugh at them.
Clearly, we are dealing with magazine mechanics here.
Nitrous does create a ****-load of cylinder pressure... after the spark. There's no difference pre-spark. Nitrous does not pack itself in the cylinder along with all of the air that would have gone in otherwise, it takes some of that air's place in the cylinder. There's no force squeezing them in together like i think you're saying. You can burn more fuel with it because it has more oxygen than regular old air. You're packing the same volume of gas in the compression stroke, but with N2O the same volume has a much bigger punch because of the building blocks of power (to make more power, burn more fuel. N2O allows you to burn more fuel due to the higher O2 content).
Pulling some timing advance simply moves this faster burning pressure wave out of the 'danger zone' (at or near TDC) and places it further along the piston's downward travel. Just the same as if you tuned your car with too much advance on regular old air, just back it out and move the pressure spike into that 'usable zone.'
Pulling some timing advance simply moves this faster burning pressure wave out of the 'danger zone' (at or near TDC) and places it further along the piston's downward travel. Just the same as if you tuned your car with too much advance on regular old air, just back it out and move the pressure spike into that 'usable zone.'