a cam to spray on
06-18-2005, 01:18 PM
#1
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a cam to spray on is there specific things I want to look for in a cam if I am going to be spraying about a 100-150 wet shot on? Wont be doing anything else to the car.
Current mods:
Gutted cats
cutout
K&N intake
SFC's
Free mods
Dyno tune
343hp/354tq
Current mods:
Gutted cats
cutout
K&N intake
SFC's
Free mods
Dyno tune
343hp/354tq
06-18-2005, 02:17 PM
#5
TECH Senior Member
You might benefit from a reverse split holding the intake valve open for a longer time, therefore allowing more charge in. As said above this is only applicable for smaller shots of nitrous, the amount is relative to the cam /head and exhaust specs (at which point is the motor not able to expel the burned charge and contamination of intake charge has a negative effect).
Basically choose your cam for your best desired NA application if you shoot small amounts of nitrous.
Basically choose your cam for your best desired NA application if you shoot small amounts of nitrous.
06-18-2005, 02:26 PM
#6
Do you know why a smaller exhaust duration that a reverse split cam gives you does to the TQ curve and why?
Interesting way to think about the cam....
So the intake and exhaust are independant of each other? So letting more in doesn't in turn qualify a need to let more out?
I wouldn't go to a reverse split cam in about any N2O motor, but then again what do I know?
Bret
Interesting way to think about the cam....
Originally Posted by Predator-Z
You might benefit from a reverse split holding the intake valve open for a longer time, therefore allowing more charge in.
I wouldn't go to a reverse split cam in about any N2O motor, but then again what do I know?
Bret
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06-18-2005, 02:37 PM
#8
TECH Senior Member
What stroker, following me around? Welcome!
Quote the whole paragraph and discuss it please.
Here, I'll do it for you:
I use such a cam with pretty good results. Hey, what do I know, it just works, I'm in fantasy land remember?
Quote the whole paragraph and discuss it please.
Here, I'll do it for you:
the amount is relative to the cam /head and exhaust specs (at which point is the motor not able to expel the burned charge and contamination of intake charge has a negative effect).
06-18-2005, 03:04 PM
#10
TECH Senior Member
Originally Posted by SStrokerAce
Do you ever answer any questions? I mean EVER?
Following you around.... I mean how can you not here you post every 5 mins.
Following you around.... I mean how can you not here you post every 5 mins.
Let us put this to an end. Ignore my posts and voice your opinions; I'll do the same regarding yours.
This squibble squabble is not benefiting any poster.
Simple, isn't it?
If you state A
and I state B
Let us just leave it at that and let other people make their choice.
I do not need this here, and I do not wish any further conversations with you.
Please, at least grant me that.
Respectfuly
06-18-2005, 07:09 PM
#13
TECH Senior Member
This is how I exploit my reverse cam under nitrous: Mind you this a small duration cam 224/220.
It allows for a bigger intake charge, with N20 the pressures inside the cylinder climb dramaticaly, this in turn will require less time to exit as per the simple rule of higher density to a lesser density once the exhaust valve opens, combining this with good exhaust flowing heads/headers and a negative overlap, the burnt mixture has plenty of time to get out.
Now this is only true under certain parameters (I've never tried this on big duration cams), but I was able to yield very good results and tremendeous trq down low, making for some pretty good 60' ft times. (considering the size of the cam).
It allows for a bigger intake charge, with N20 the pressures inside the cylinder climb dramaticaly, this in turn will require less time to exit as per the simple rule of higher density to a lesser density once the exhaust valve opens, combining this with good exhaust flowing heads/headers and a negative overlap, the burnt mixture has plenty of time to get out.
Now this is only true under certain parameters (I've never tried this on big duration cams), but I was able to yield very good results and tremendeous trq down low, making for some pretty good 60' ft times. (considering the size of the cam).
06-19-2005, 01:26 AM
#16
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Originally Posted By PREDATOR-Z
I mean't "degree of overlap at .050" is negative
I mean't "degree of overlap at .050" is negative
at higher RPM?
Being N/A, with Nitrous, wouldn't we want overlap to help scavenge the chamber
and pull in more charge for the next cycle?
From what I understand, a higher oxygen density intake charge (N20) allows
for more fuel to combust, which means the exhaust gasses are typically more
in volume. Wouldn't we want more duration and lift on the exhaust side?
Correct me if I'm wrong but Nitrous and Boost cams are typically split with
higher values on the exhaust side?
Not trying to side here, but it's going against all sources of tuning that I've come across.
06-19-2005, 02:51 AM
#17
TECH Senior Member
Originally Posted by ADRENALINE-Z
Now wouldn't a negative overlap cam produce poor power results, especially
at higher RPM?
Being N/A, with Nitrous, wouldn't we want overlap to help scavenge the chamber
and pull in more charge for the next cycle?
From what I understand, a higher oxygen density intake charge (N20) allows
for more fuel to combust, which means the exhaust gasses are typically more
in volume. Wouldn't we want more duration and lift on the exhaust side?
Correct me if I'm wrong but Nitrous and Boost cams are typically split with
higher values on the exhaust side?
Not trying to side here, but it's going against all sources of tuning that I've come across.
at higher RPM?
Being N/A, with Nitrous, wouldn't we want overlap to help scavenge the chamber
and pull in more charge for the next cycle?
From what I understand, a higher oxygen density intake charge (N20) allows
for more fuel to combust, which means the exhaust gasses are typically more
in volume. Wouldn't we want more duration and lift on the exhaust side?
Correct me if I'm wrong but Nitrous and Boost cams are typically split with
higher values on the exhaust side?
Not trying to side here, but it's going against all sources of tuning that I've come across.
That was negative * of overlap @ .050
Let me give it to you at adv. Duration .006
273 int/ 269 exht
So degree of overlap at adv durations:
273+269=542
542/4=135.5
135.5-116 (lsa)=19.5
19.5x2= 39* of overlap at .006
Like I said, a big shot nitrous has to have more exhaust. Now in my particular application, my reverse 224/220, .581/.581 116+0, behaves very well under 150>200 shot dry, (gain from 175>200 is where I start seing an inneficiency), I never shot more than 200 dry on it.
To help countering the higher intake charge Vs shorter exhaust, I enlarged the exhaust ports, portmatched to my 1 3/4 header primaries (they are midlength which scavenges more at higher rpms). the high lifts and XE-R ramps combined with a tall lsa and no advance, seem to work well alltogether.
I've been 6.7x and 6.8 in the 1/8th with a 3200 stall and an estimated 3600 weight at least.
Your reasoning is completely on the ball (correct), but apparently, under specific applications (parameters), a reverse like mine does pretty well.
Simple explanation is like this:
Bigger charge>bigger bang>bigger pressure>faster exit (like I said, this is only true within specific, ( I can even say) limited parameters), but fits my desired overall combo.
My goal was a mid to low 10sec car on 150/175 shot, almost identical to stock street manners, that passes sniffer with flying colors on a regular tune, still fuel efficient and has loads of trq and power under the curve.
Right now my heads (mildly modified) keep me in the high 10's but I got a set of stage 2.5 5.3L comming soon, and I firmly believe I should achieve my goal of mid to low 10's by September.
Last edited by PREDATOR-Z; 06-19-2005 at 03:09 AM.
06-19-2005, 02:08 PM
#20
Originally Posted by Adrenaline_Z
Now wouldn't a negative overlap cam produce poor power results, especially
at higher RPM?
Being N/A, with Nitrous, wouldn't we want overlap to help scavenge the chamber
and pull in more charge for the next cycle?
From what I understand, a higher oxygen density intake charge (N20) allows
for more fuel to combust, which means the exhaust gasses are typically more
in volume. Wouldn't we want more duration and lift on the exhaust side?
Correct me if I'm wrong but Nitrous and Boost cams are typically split with
higher values on the exhaust side?
Not trying to side here, but it's going against all sources of tuning that I've come across.
at higher RPM?
Being N/A, with Nitrous, wouldn't we want overlap to help scavenge the chamber
and pull in more charge for the next cycle?
From what I understand, a higher oxygen density intake charge (N20) allows
for more fuel to combust, which means the exhaust gasses are typically more
in volume. Wouldn't we want more duration and lift on the exhaust side?
Correct me if I'm wrong but Nitrous and Boost cams are typically split with
higher values on the exhaust side?
Not trying to side here, but it's going against all sources of tuning that I've come across.
Rob this man understands how the world works listen to him.
FWIW I don't think most people need as much exhaust duration as they think they do on a N2O cam but you still need overlap etc... to get the job done.
Bret
