Can nitrous be discussed in this forum also?

[Kstang]

Well I recently came across some money and I was thinking of getting a cam and roller rockers. I was also thinking of adding some juice, my friends recommended the Nitrous Express “Hitmanâ€￾ system. Now I have an aussie 4v head and I was wondering about the distribution of nitrous and fuel using a plate system. From what I have read Dan (import killer) was running a 100 shot on a log head. I was just wondering if their was any problems with cylinders 1 and 6 not getting enough of the gas/fuel mix and cylinders 3 and 4 getting to much? I am assuming that since Dan has not had problems with the log head I shouldn’t worry to much using the much better flowing aussie head. The other thought was a direct port system using individual foggers per cylinder. This will be more $$ and I was wondering if the better distribution is worth it at the 100 shot level.

Thanks in advance.
kevin

 

[xctasy]

KASTANG asked

Can nitrous be discussed in this forum also?

Sure, why not. It's just chemical supercharging!

The reason why nitrous is a bit of a worry on a poorly distributed air/fuel mix is the excess fuel factor. If there isn't the correct cc/minute flow of gasoline to suppress the lean-out condition nitrous oxide creates, then the other or even number 5 and 2 cylinders may roast the ring lands. The great thing is that the I6 has very strong rods and crank...there isn't a lot of bending moment on anything, even with a poor rod ratio. The effectiv compression is good, and the engine is well cooled at number 1. The real issue is number 2 and 5, the cylinders most likley to die from detonation. On the log or cross-flow, these are the ones that get hammer time.

The 2v head breaths very evenly, and I'd be looking at ensuring the large 42 mm ports are feed with sufficient excess fuel via a port gasoline/n20 system. Then read spark plugs, and experiement. With good quality US pistons from the I4 HSC engines, this would be perfect. I'd say you could go up quite a good deal more than the 50% of stock hp rise. You may get into the 275 hp level's if you have only 130 hp. The cam has to be right for nitrous, with good duration on the exhast to bleed off the exhast.

One other thing is differential compression ratios 0.5:1 lower on 2 and 5. Not silly if you want to avoid detonation.

On another tact, just a stock D7 log with a port gasoline/n20 system would be okay only if feed with a good mixture distribution from a dual carb set-up. The stock 1.75" hole does look a bit of a worry, when there is up to one quart of gas per minute traying to feed two branches with a concentration time of 5 milliseconds for each side. Thats wayyyyy too long for an engine which fires a cylinder every 290 milliseconds at 5000 rpm. If there is not enough fuel in the cylinder, it'll never safely get the percentage increase in power.

Another way to put it, is every second, a 275 hp I6 engine needs almost one tea-spoon of gas in each cylinder, each second. If it doesn't get that while the carb barells and nitrous is being delievered,guess what, it'll lean out on the outer cylinders! That 'time of concentration' thing again.

But, hey, the 200 has a huge factor of safety! It'll just

a) blow number 2, 5 or 6 on the fire ring of the gasket
b) melt the spark-plug head
or
c) break a ring land if it gets too much termal loading in the chamber.


Remember, its possible for a 155 hp unleaded 350 to hit 500 hp on Nitrous if its done right...on a stock engine with manifold bolt-ons and th right cam. 275 hp on a 100 net hp log I6 shouldn't be a problem!

Hmmm, wonder what a 300 would do? Kill Chevies?????

 

[MandarinaRacing]

Best piece of advice I could give you is to go with the direct port set-up. One nozzle per cylinder, that takes cares of even fuel and N2O distribution...OTOH you could try a "cloverleaf" plate, since your intake is 4BBL.
Check these out...
http://www.slantsix.org/articles/hrm-slsick/hrm-dec-pg1.jpg
http://www.dutra.org/pictures/engine/dutra-cuda-engine/nos-test.htm

Alex

 

[Kstang]

You have the plate system don't you? Are you not happy with that? Have you had any problems with the plate system and leaning out? Thanks a bunch

 

[Anonymous]

The hyper pak intake is the best as far as equal runner lenght. They still have issues with rich plugs. A plate system just will not distrubute fuel and nitrous like a fogger system can.

On the six with the fogger. He used steel lines and after some use they will corrode like crazy. Stainless is the best but a little pricey.

Steven

 

[MandarinaRacing]

Kstang wrote:

You have the plate system don't you? Are you not happy with that? Have you had any problems with the plate system and leaning out? Thanks a bunch

VERY happy indeed, it's probably the best mod I've made. I've tried the 50 shot, and no problems so far...we'll see how it goes with the 75 and 100 shot once I've sorted out my clutch problems.

Alex

 

[Anonymous]

This is my system
Its a 250hp plate from OZNOS

 

[Kstang]

a 250 shot of juice? really? how does the engine take that much? Thanks

 

[Anonymous]

I will let you know in a month
But I think it wont take it very well

 

[xctasy]

Hehehehe, Gassem all GASSED250!

The increase you can hope for for a perfect nitrous oxide car is 1.5 times the original power. If your stock power is 130 hp, don't ever go for more than 65 hp gain. I fit is a 320 hp XR6Turbo, you can go for 160 shot extra tops.

Go for a cam bigger on duration than on lift. Make it streetable, but attempt to get a wide power band. If you six only gave power at 3800 rpm, then aim for power at 5000 rpm+, with a redline at 5500 to 5750 rpm. It will remove some of the torque down low, but it'll be okay if you go for a high stall converter or a close ratio 5-speed gearbox with a set of 3.55/3.5/3.45 gears. Remember, some one may not let you use the nitrous on the street!

Then remember that if the rebuild engine comes out with, say:-

190hp flywheel as a modified hot 200 or
240 hp flywheel as a modified hot 250 or
280 hp flywheel as a modified hot 300 at 5300 rpm

then with the ideal nitrous system, you'll have maximum power at only 4500 rpm, and it will be about 100 hp up on stock, and behave like a 289 or 383 or 450 cube V8. Anytime you give an engine giggle gas, you reduce the speed at which peak power occurs by 20%. Great for people who don't want to thrash there engine.

Thats 280 hp for the 200, and
360 hp for the 250,
420 hp for the 300.

The real trick is that is all torque and it comes in only when you wide open throttle the engine. Then it locks out.

You must add the same extra fuel in jetting that a 280/360 or 420 hp six would need. You can't go beyound the 1.5 times the original power rule, or the engine will cope a thermal overload.

Example may be a 200 six with a 500 holley that does about 150 hp at 4500 rpm. It may have two 67 jets. If you add a port nitrous system, it will then need to find half that 160 hp in extra gasoline jetting. In other words, you'd need about one extra 67 jet just to stop the engine lean backfiring. All nitrous systems need an excess fuel factor to stop this.

If you want 200 hp extra of nitrous, you need an engine that has 400 hp without nitrous. You can't add more any more nitrous, because the engine is detonation limited. Even with forged pistons and the best intake, ignition or EFI ever made, you can't go over that relationhip.

Check out Australian Streeters. Some have 496 or 514 big blocks that only do 650 or 700 hp off the bottle. With Nitrous, they only ever go to about 1000 hp, a 250-300 hp increase. These are purpose built engines, designed with big duration cams and often 1050 cfm carbs that can only produce 700 hp without gas.

The key to making n20 work is to never walk past the 1.5 times power limit.

In practice, even with just one 500 Holley 2-bbl, a six port nitrous system is the ideal. The key is never to go any bigger than 23 thou jet on the gasoline side, and no more than about 20 on the nitrous. Always use 6 fogger nossels. Thats enough for a 120 hp boost. Most of our engines don't go over 160 hp stock. An 80 hp Fogger kit with six nossles could have 18 thou fuel jets, and 16 thou nitrous jets. On an EFI F150 with 155 hp stock, which does an 18 second quarter, this is enough to take it under the 16s with ease.

 

[MandarinaRacing]

Also dual pattern cams work best for a nitrous/blower/turbo engine.

Nitrous Oxide Cam Shafts

Choosing a Camshaft
Optimum cam timing for a nitrous motor will be different than optimum timing for that same motor off the bottle, so you will have to make a choice as to whether you want the most power with or without nitrous. Obviously if you are driving the car on the street most of the time, you will want the best power off the bottle. If you find that you can spare some power to make your car faster at the track, picking a camshaft to favor nitrous can make a substantial difference when nitrous is in use. If course it is a trade off, but usually the power that you make on the bottle, will be far greater than the amount lost off the bottle.

Pumping Losses
Nitrous oxide adds oxygen, much of which is in liquid form. So you can see that a large intake valve and port is not required or desirable. Larger intake ports cause more of the nitrous to turn to a gas and reduce the amount of normally aspirated power, if the nitrous takes up more room, there will be less room for air, reducing volumetric efficiency. Also, you do not want or need long intake duration or a very high lift, so the intake side of the cam does not need to be any different when nitrous is used. The exhaust is a totally different story. All that extra oxygen and fuel makes for a substantial increase in exhaust. How can the exhaust valves deal with this? It can't, pumping losses go out of sight. Much of the extra power made in the cylinders never makes it to the flywheel, because it is used to push out the exhaust. Since making the exhaust valve large enough and the port flow enough is impractical with most cylinder heads, we must take other actions to cut pumping losses (which is actually just a band aid fix).

Reducing Pumping Losses
The first obvious step is to use a dual pattern cam with longer exhaust duration. Opening the valve earlier will help by getting the valve open more and bleeding off some pressure before the piston starts moving up the bore. This does eat into the power stroke, but more power is freed up than would be made by holding it closed longer (the best solution would be a larger valve and better port). The blow down phase (overlap period) becomes very important in a nitrous engine, because the gasses has much greater velocity and can over scavenge, closing the valve exhaust valve a little earlier helps. Anytime you make more power by reducing pumping losses, you are freeing up horsepower that already existed in the cylinders. The engine will still experience the same loads, but more power will be put to the flywheel and less will be used to push out exhaust.

Camshaft Specs
As I said earlier, the intake needs to remain pretty much the same, but the exhaust needs more duration, an earlier opening point and an earlier closing point. To make this happen, you need to use a dual pattern cam with more exhaust timing, and a wider lobe separation angle. Cam's with 112-116° lobe separations are common is nitrous motors. To keep the intake timing the same, you must install the cam advanced, usually 6-8° advanced. The good things about this are that advancing a cam will bring more low-end (at a trade off of top-end) when running without the nitrous and the wider lobe center angle will also help idle and vacuum. Even the most radical nitrous profiles are usually pretty tame on the street. Ultra high lift cams are not need to make power with nitrous. On the exhaust side, the low lift flow is the most important thing, and must be dealt with much more seriously than high lift flow.

Alex