nitrous

[knelson]

here my delimma I have a new 11:1 JE 426 piston, hotcams stage 2, 39mm fcr , and ported head waiting to go into my 400ex but I don't feel that will be quite enough to keep up with all the guys I ride with(360r,moto,450r,and 450yfz). So I am contemplating the boon dockers kit with the 20oz bottle under the seat shooting the normal 10-15 hp shot to it. I know the pro's and con's of nitrous but the boon docker's kit seems to be a fairly safe nitrous setup , but I know that I probably need to run thicker gaskets such as the stock base and stock head gasket to maybe lose a little compression so I dont detonate and also so I dont stress my rod. I already planned on using av gas being it has 100 octane and is leaded to keep heat down.I plan on taking my aftermarket rev box off and using my stock so not to advance my timing for the nitrous and so I dont over-rev my bike and strech my rod(stock). So that is my plan does anybody have any experience with something similar,any tips,concern,etc.. please tell me if this is gonna be a big no no

[hondarider2006]

I believe a high compression piston and nitrous is a big no no to start off with. I'm not 100% sure on this though. But with the set-up you are talking about, without the nitrous you will hang with the 450's just fine;)

[wilkin250r]

High compression isn't a "no-no", but it does add to the danger factor.

Personally, I think 11:1 compression is fine for nitrous, as long as you're running a high-octane fuel. I'd stay away from the AV fuel and run true race gas. I know the AV gas is cheaper, but if you are going all-out with your motor, cam, and now nitrous, why are you cutting corners with your fuel?

[sleepin400]

I can't say any details from a 4 wheeler, but in the car world. Nirtous accepts high compression pritty well. I would definitally consider race gas and a colder plug. To be even more safe, if you can figure out how to back off your timing. I would think you'd be pritty good. And check that plug frequently. Lean=boom

But again, this is general auto knowlege. You'd think it'd be the same.

if you decide. let us know the results. Sounds fun :blah:

[NitrousEdge]

Like sleepin400 I only have knowledge of nitrous in the auto world, but I would love to learn a little more about it for atv's. I don't know how much the stock rods can take, but I would think you would be ok with stock or slightly retarded timing and good race gas - don't use av gas....a nice 110 octane would be more than enough to keep you safe - - I would think.

Let us know your results!!!:devil:

[knelson]

Well, I just left the airport and the 100ll fuel is actualy more about 115 depending on how old it is. The whole reason in running av gas is because it's leaded, it has always ran cooler in the past with it, and alot of the race fuels I have used in the past are not leaded. I thought that It may aid in keeping the temps down and its octain levels are more consistant where as some of the race fuels are not, but my friends father in law is a dealer in vp, sunoco,and erc race fuels so I can run race gas just as easy. I think the JE piston is 11:1 with no base gasket and the xr head gasket, so I figured with running stock gasket thickness on my base and head I could maybe lose some compression getting it closer to about 10:1 so to help out my stock rod. Im not sure how to retard my timing should I get a sparks key and turn it backwards(that would probably be retarded to much).Maybe I should get an adjustable cam sprocket? I would like to get something external though so I dont have to run retarded all the time.I will probably run the dpr9z plug to keep it cooler.

[wilkin250r]

Originally posted by knelson
I will probably run the dpr9z plug to keep it cooler.

A cooler plug doesn't cool anything but the plug. It is designed to keep the electrode end from overheating and creating a hot spot in the engine. It won't make your engine run any hotter or cooler.

[knelson]

I thought a "Cold" spark plug has a shorter insulator nose and absorbs more combustion chamber heat, that being heat would travel a shorter distance, and allow the plug to operate at a lower internal temperature. I was under the impression a colder heat range would be necessary when an engine is modified for performance, subjected to heavy loads, or it is run at high RPMs for significant periods of time. I thought the colder plug removed heat more quickly, so it would reduce the chance of pre-ignition/detonation. I really don't now that much on the 400ex so do you think I should run the normal dpr8z or the "hotter" dpr7z insted of the "colder" dpr9z spark plug, or does it not really make a diffrence?

[wilkin250r]

Yes and no.

The amount of heat dissipated through the spark plug is not very much, it really won't reduce engine tempuratures or combustion chamber tempuratures. All it really does is regulate the spark plug tempurature. A colder plug dissipates more heat, so the spark plug is colder, but it won't make the engine run colder.

The spark plug needs to be hot enough to burn off carbon deposits. Carbon build up is bad. But at the same time, you don't want it to be red hot, because it will cause pre-ignition or detonation. Hot spots are bad.

So basically, this means the spark plug has to stay within a certain tempurature range. If the spark plug dissipates too much heat to the head, then the electrode is not hot enough to burn off carbon deposits. You need a hotter spark plug.

If the spark plug does not dissipate enough heat, then the spark plug gets hot, and you have a hot spot in your engine. You need to get a colder plug.

In a modified engine, you increase combustion tempuratures, which will increase spark plug tempuratures. So you need to get a colder plug to bring the electrode tempurature back down.

So yes, you are right, you need a colder plug in a modified engine, heavy loads, or at sustained high RPMs. But you need to realize that the actual AMOUNT of heat dissipated by the spark plug isn't very much, it won't really affect engine tempurature. All it really does is regulate the spark plug tempurature to keep it within it's allowable range (hot enough to burn off deposits, but not so hot that it causes pre-ignition).