NITROUS OXIDE ( nos / n2o ) advice forum

Lets take a Busa and fit an inlet cam in the exhaust, now what would you do with the cam timing for a huge nitrous dose?

When you say fit an inlet cam in the exhaust I guess you mean a longer duration lobe?

I've no Hayabusa experience so don't know what cams they have or if you can fit the inlet in the exhaust.

Yes its common on bikes to fit inlet cams in the exhaust for increased lift and duration.

You could do it on old gs's,once you took the sprockets off the only "visible" difference would be the tacho drive

Wouldn't have a clue about a busa.IDP any idea on the valve opening mechanism? rockers or shim and bucket? Then are the valve centres the same?


It's a little difficult to say without some timing figures,I mean it might be perfect already.

And this is nitrous only? no concern to NA perfomance?

I'd be fairly sure the Hayabusa is bucket and shim.

I guess Trev is asking, for a big nitrous dose using a longer cam would you add the extra duration equally (same LCA) or earlier/later.

I've read some ideas about increasing exhaust valve and port size too,while leaving inlets alone as they don't need to flow more.

During the Eco tec developement they say that the engine became "constipated" on large nitrous doses(ref;Jeff Hartman...turbocharging performance)

I advanced my exhaust cam on the beemer after blowing the plenum apart,shifting with the nitrous on. Didn't do it again.

was considering retarding inlet cam to reduce overlap to minimum.

It doesn't have to be a Busa (that was just an example that related to Brad as he'd mentioned cam timing in previous posts), any engine would do and I'm only interested in ALL OUT nitrous motors.

I'd expect Stephen Moon to have some inside info on how the American's do it and I'd like to compare that with what I've done in the past and any thoughts anyone else has on the subject.

Just for the record on my very first V8 engine, I considered reversing the functions of the inlet and exhaust systems, so the exhaust came together and exited through the center of the bonnet and 2 banks of 4 carbs would have been attached where the exhaust manifolds were originally.

The original exhausts would have been as heavily ported as possible, along with bigger valves etc. but the inlets would have only been modified to flow exhaust rather than intake charge but left alone on size, as they would already flow MUCH more than the original exhaust ports could every have been modified to achieve.

Obviously that was an extreme case and based on limitations of that particular engine design but something for you to think about.

My motors have the largest possible valves you can get into them, both inlet and exhaust, with serious reworking of the inlet tracts to get more flow.

The motors are built to make good horsepower naturally aspirated.

Inlet and exhaust cams are the same lift and duration - high lift, long duration. Fuel pressure on the high side as well.

The idea on the exhaust side is having excess fuel to cool the valve and exhaust tract.

I also play around with the spark plug and siting to ensure there are no hot spots in there to cause detonation.

Have you picked up cam timing tips from the high end US contacts you have and if so what do they currently do with overlap/lobe centers?

Inlet and exhaust cams are the same lift and duration - high lift, long duration.

I'm using the same motor as stephenm, obviously hugely lower spec, but i do have two sets of cams, the 1100k cams i used to get more power than my stock bandit cams. the are a bit tired, so i just got some good gsxr 750 long-stroke cams i was going to replace the 'k' cams with.
do you think i should just swap the 750 inlet cam into the exhaust side?
any hints about cam timing?

lorenzo

Nobody else want to share their thoughts on cam timing with us, Stephen, Brad?????

Most motors come to me built so I don't always know what the cam timing is.On my own stuff I've never played around to much with it due to the fact that is a bastard to do with a Busa motor in the frame.I normally set the nitrous bikes I run at 110/110,but the Motec has a facility to check the cam position relative to the crank and the cams move as much as 3 degrees on my bike as the engine accelerates.This is the inlet cam so I'm guessing the exhaust does the same I've seen logs of other bikes that move more.
The cam chain is correctly adjusted too, so you can imagine that when I hear that people have seen gains by swinging the cams a few degrees I'm always sceptical as it will depend on the cam chain tensioning system,

curious do you think the long run on chain from crank to exhaust and then the short run from zorst to inlet and back to crank factor into this in any way , or is that just the reason that the weak cast cams fail more on inlet than zorst

Brad,I take it the cam position sensor is there for the sequential fuel injection?

and ignition
Although by the time you get up in boost the things vertually like batch fire due to the duration of the injectors.

No waste spark any more?

Doesn't cam timing have an effect on ignition and injector timing then?

Do you have to add a correction factor,if the cam timing has been altered?

Just curious,only just getting familiar with the le jetronic on the beemer,wanted to learn from the bottom up,rather than jump straight in with a laptop and no idea what i was trying to do.

Is it true that busa's break cams?

No and no........the cam pos sensor just tells the computer to 'look' at the crank sensor and start counting.I've never heard of any cams breaking

My US 'expert' says that most people increase the lobe centers but he thinks they're going the wrong way.

Wide lobe centres on my motors and a lot of the quick US nitrous bikes.

I think its another of those U turn situations.

Until now I've repeated pointed out that TIME is the factor that most people overlook but I'm now going to add the U turn factors, because people see what works best on small amounts of nitrous and assume those factors will stay constant no matter how much nitrous you add but the more I learn about nitrous the more U turns I see and the more I suspect there are still to be realised.

Up to a certain amount of nitrous, increasing the lobe centers is the better option but when you start pushing the limits the reverse MAY be true.

I don't understand the last post - the quick US guys are using wide lobe centres and putting in huge amounts of nitrous and fuel.

Yes I'm with you on that BUT the American 'expert' who I'm talking to, THINKS that large doses of nitrous would produce better results if the cam lobes were closer rather than wider apart.

The point I'm making is that MOST people learn what works well on small power levels (which makes a lot of sense) and then ASSUME it will work the same or need more of the same as you crank up the power. However, as I've found with a number of nitrous related issues, that is not always the case and the REVERSE often starts to apply at some elevated level of nitrous flow.

Now I'm not saying I agree with this US 'expert' but his reasoning behind it appealed to my "common" sense approach to things, so he could be right and as a consequence I'm going to keep an open mind on the subject until I have more proof either way.

BTW this expert is a car guy and has no experience of bikes. Although a good deal of nitrous info is universal regardless of engine size (to a degree) there are some factors that aren't, so although he's confident it applies to cars, it may not apply to bikes BUT the logic behind should apply to all.

I just wonder if the "rules" do actually change for the cars - it looks as though the large motors can put in huge dosages of nitrous compared to bikes and that may change things entirely.

We hit on this in the dissociation thread.

The "big" cars have huge bores and half the rpm of the top bikes.

So it could well be the "time" thing again.

which one's easier to detonate?