n2o and 10.5:1 ?
Thread Starter
Registered User
Joined: Jan 2002
Posts: 160
From: Denton,TX USA
n2o and 10.5:1 ?
I'm currently building a 355, 5140 crank 4340 rods, and srp 10.5:1 forged pistons. Is the 10.5 too high for nitrous, casue some one told me to be careful once you get past about 9.5 and nitrous.
Registered User
Joined: Apr 2000
Posts: 555
From: Yakima WA
Superchargers and Turbocharging require lower CR ~8-9.5. In a Nitrous Application use as much Compression as you can get away with using (assuming in your case) Pump gas.
If you can bump it up a lil more, closer to 11:1.
------------------
Kurtis Tamez
LT4-396.com
97 Z28 LT4-396
94 Firehawk LT1-396
Team NW F-Body
If you can bump it up a lil more, closer to 11:1.
------------------
Kurtis Tamez
LT4-396.com
97 Z28 LT4-396
94 Firehawk LT1-396
Team NW F-Body
Registered User
Joined: Jan 2001
Posts: 97
From: Connersville, Ind
I am running about 11.25 to 1 compression with 150 shot, getting ready to go 200. 
------------------
93 Z-28, 355, Moser 9", 8 point roll cage. You know Slow
Best track time so far.
N/A 1.8 60' 13.0 106- old motor
N/A 2.0 60' 12.7 113- needs tuning
N20 1.9 60' 11.8 119- needs tuning and slicks
rwhp; 324.0 rwtq; 339.3 n/a
rwhp; 471.8 rwtq; 618.0 N20
------------------
93 Z-28, 355, Moser 9", 8 point roll cage. You know Slow
Best track time so far.
N/A 1.8 60' 13.0 106- old motor
N/A 2.0 60' 12.7 113- needs tuning
N20 1.9 60' 11.8 119- needs tuning and slicks
rwhp; 324.0 rwtq; 339.3 n/a
rwhp; 471.8 rwtq; 618.0 N20
Administrator
Joined: Nov 1998
Posts: 71,094
From: Hell was full so they sent me to NJ
10.8:1
500crankHP on motor
800crankHP on spray
C-16
------------------
Fred
94 Formula A3: 381/TH400/N2O
Advanced Tech Posting Guidelines
Detailed Mod's List
11.513@115.59 on motor; 11.162@127.67, 1.643 60' on a 125-shot. Going with a 275-shot this year
[This message has been edited by Injuneer 94FormM6 (edited July 19, 2002).]
500crankHP on motor
800crankHP on spray
C-16
------------------
Fred
94 Formula A3: 381/TH400/N2O
Advanced Tech Posting Guidelines
Detailed Mod's List
11.513@115.59 on motor; 11.162@127.67, 1.643 60' on a 125-shot. Going with a 275-shot this year
[This message has been edited by Injuneer 94FormM6 (edited July 19, 2002).]
Moderator
Joined: Dec 1969
Posts: 10,745
From: Buffalo, New York
The discussion can only be general without reference to the fuel you plan to use. In general, there are two philosphies wrt nitorus setups.
1. build the best na motor you can and add a bit of spray for some additional hp.
2. build a low compression motor (as for a SC setup) and use a large shot of nitrous.
Obviously, you can also be somewhere in the middle. If the motor isn't built yet and you plan to spray it with 10.5:1 I'd strongly suggest that having the piston crowns ceramic coated will be ~$200 well spent. I have used Swain Technologies at http://www.swaintech.com/ and they do a good job with coatings. My next motor will not only have coated piston crowns but coated exhaust valves as well.
Rich Krause
------------------
'95 Z-28 383 with Vortech, nitrous, etc.
"1FASTZ28"
1. build the best na motor you can and add a bit of spray for some additional hp.
2. build a low compression motor (as for a SC setup) and use a large shot of nitrous.
Obviously, you can also be somewhere in the middle. If the motor isn't built yet and you plan to spray it with 10.5:1 I'd strongly suggest that having the piston crowns ceramic coated will be ~$200 well spent. I have used Swain Technologies at http://www.swaintech.com/ and they do a good job with coatings. My next motor will not only have coated piston crowns but coated exhaust valves as well.
Rich Krause
------------------
'95 Z-28 383 with Vortech, nitrous, etc.
"1FASTZ28"
Registered User
Joined: Apr 2000
Posts: 555
From: Yakima WA
For once I'd have to disagree with ya Rich(even using just generalities LOL). Although in a street car things ar different then a racecar, and like you said fuel requirements play a large role, I would never lower the CR because I was planning on using a large system. The nice thing with Nitrous is you can add the proper fuel requirements in only when you'll be using it. 
My own motor, should be *able* to use pump gas naturally aspirated, but on the system, will utilize a much higher grade. However, at this point I wish I had added more CR (13.5-14:1) since this car will no longer truely be driven. I still would use the large system, however the motor itself would be making that much more power.
Granted a Full Effort Nitrous Mill won't make the power of an NA Motor, due to camshaft design, heavier rotating assembly, etc, so I see that as being moreso the area where trade offs are going to be made.
10.5:1 should work just fine, but as I said above, if you haven't nailed down your CR yet, I'd opt for the 11-11.5:1 range. For the average guy, try to make more power on the motor so you can use a smaler system to get the job done when the need arises.
------------------
Kurtis Tamez
LT4-396.com
97 Z28 LT4-396
94 Firehawk LT1-396
Team NW F-Body
My own motor, should be *able* to use pump gas naturally aspirated, but on the system, will utilize a much higher grade. However, at this point I wish I had added more CR (13.5-14:1) since this car will no longer truely be driven. I still would use the large system, however the motor itself would be making that much more power.
Granted a Full Effort Nitrous Mill won't make the power of an NA Motor, due to camshaft design, heavier rotating assembly, etc, so I see that as being moreso the area where trade offs are going to be made.
10.5:1 should work just fine, but as I said above, if you haven't nailed down your CR yet, I'd opt for the 11-11.5:1 range. For the average guy, try to make more power on the motor so you can use a smaler system to get the job done when the need arises.
------------------
Kurtis Tamez
LT4-396.com
97 Z28 LT4-396
94 Firehawk LT1-396
Team NW F-Body
Moderator
Joined: Dec 1969
Posts: 10,745
From: Buffalo, New York
<font face="Verdana, Arial" size="2">Originally posted by KTamez:
For once I'd have to disagree with ya Rich(even using just generalities LOL). Although in a street car things ar different then a racecar, and like you said fuel requirements play a large role, I would never lower the CR because I was planning on using a large system. The nice thing with Nitrous is you can add the proper fuel requirements in only when you'll be using it.
My own motor, should be *able* to use pump gas naturally aspirated, but on the system, will utilize a much higher grade. However, at this point I wish I had added more CR (13.5-14:1) since this car will no longer truely be driven. I still would use the large system, however the motor itself would be making that much more power.
Granted a Full Effort Nitrous Mill won't make the power of an NA Motor, due to camshaft design, heavier rotating assembly, etc, so I see that as being moreso the area where trade offs are going to be made.
10.5:1 should work just fine, but as I said above, if you haven't nailed down your CR yet, I'd opt for the 11-11.5:1 range. For the average guy, try to make more power on the motor so you can use a smaler system to get the job done when the need arises.
</font>
For once I'd have to disagree with ya Rich(even using just generalities LOL). Although in a street car things ar different then a racecar, and like you said fuel requirements play a large role, I would never lower the CR because I was planning on using a large system. The nice thing with Nitrous is you can add the proper fuel requirements in only when you'll be using it.
My own motor, should be *able* to use pump gas naturally aspirated, but on the system, will utilize a much higher grade. However, at this point I wish I had added more CR (13.5-14:1) since this car will no longer truely be driven. I still would use the large system, however the motor itself would be making that much more power.
Granted a Full Effort Nitrous Mill won't make the power of an NA Motor, due to camshaft design, heavier rotating assembly, etc, so I see that as being moreso the area where trade offs are going to be made.
10.5:1 should work just fine, but as I said above, if you haven't nailed down your CR yet, I'd opt for the 11-11.5:1 range. For the average guy, try to make more power on the motor so you can use a smaler system to get the job done when the need arises.
</font>
But if you'll note, I didn't say which was the best philosophy, just that there are two basic approaches. No matter what, the octane of the fuel and the CR are the major limiting factors in determing how much nitrous you can inject: no parts (especially piston crowns) will stand up very long to detonation. Of course, the physical strength of the whole motor (but especially pistons and rods) needs to be man enough to withstand the expected peak cylinder pressure, but if that's assumed the upper limit is based on detonation.
In the original post, "menlatin" asked if 10.5:1 was "too high" for nitrous. The answer is "no", but the CR will limit the amount of nitrous compared to a lower CR. For a given engine type, the main variable that will determine the maximum amount of nitrous for a given CR is octane.
In terms of ultimate performance, I think that an optimized N2O setup is actually based moderate compression with a big dose of N2O. The reasons for this belief are more theoretical than practical and since I'm not (for a change) in the mood to write an essay I won't elaborate here. OTOH, N2O can be used on a high revving, big cam, high CR NA motor to fill in the weak midrange torque inevitable with big heads and cam and make a superperforming motor. I don't think anyone has a definitive answer.
BTW: I am talking about a production based motor running on gas. "Exotic" combos are different.
Rich Krause
------------------
'95 Z-28 383 with Vortech, nitrous, etc.
"1FASTZ28"
Thread
Thread Starter
Forum
Replies
Last Post