NITROUS OXIDE ( nos / n2o ) advice forum

okay first off, noswizard the spark strength hasn't been tested
In that case I STRONGLY advise you to do so.

but all plugs record good colouring, ecu does not detect misfire nor does the lambda sensor detect any unburnt fuel or a excessively rich/lean mixture on nitrous.
That's of no consequence as INADEQUATE spark strength does NOT show up as misfires or incorrect Lambda readings. What it does show up as is RELATIVELY INEFFECTUAL RESULTS!!!!
What happens is the spark doesn't have enough energy to jump at the desired time (due to elevated pre combustion pressures due to the added nitrous) and as a consequence the spark is delayed until the cylinder pressure drops to a level it can jump at. The result is an overly retarded ignition which produces LESS POWER than would have been the case, if the spark had jumped at the intended time.

The ignition system is a direct coil type, that being the type with pencil cos over each plug, wasted spark setup as standard with standard plugs ( although they seethe same plugs as used in the turbo megane so should be more than cool enough ).
Direct coils are far more prone to failure than older types of ignition coils, because they are subjected to much more heat and we FREQUENTLY find them to be the cause of inadequate results on nitrous.

The car runs fine off nitrous, keeping on par with other similar powered vehicles. And yes it does have 6 gears for those enquiring.
Again another indication that the cause is INADEQUATE spark strength (and its the cause of a common misconception that it indicates it won't be the cause of the problem you're experiencing), because it's ONLY INADEQUATE when the nitrous is added, causing the cylinder pressure to rise to a high enough level, to exceed what is normally required and the system is capable of delivering under normal conditions. When NOT adding nitrous, the spark energy required to jump the plug gap is much less and as a consequence the car runs fine without nitrous.

I will move the bottle to the 5 o'clock position for safe measures. Regarding the line I replaced the braided line with the nylon line myself so know it isn't kinked, I will however check in the alkward places like the pedal area where it passes behind them securely.
The bottles NOT going to be a problem - the pipe MAY be if kinked or overly tightened but it's unlikely.

Thanks.

Edit: on a side note how do you go about testing the spark strength on a modern ecu controlled car.
With this and a copy of my book would help with this and any other issues if you have thoughts of ramping up the power;
http://www.noswizard.com/product_desc.php?id=104
http://www.noswizard.com/product_desc.php?id=97

And regarding an earlier question, my car has a small primary cat at the end of the manifold where as the other car doesn't. This is a 300 cell type I believe, approx 1/3rd the size of a normal cat.

Is there much gain to be had from a straight through exhaust with nos?
I must have missed the original mention of that - IF that is in anyway restrictive to flow (as most are), that could also be the cause of the lower performance on nitrous, as you generate MUCH MORE exhaust when using nitrous and ANY restriction in exhaust flow will CHOKE the engine and limit the performance.
Increasing the exhaust flow on ANY vehicle will result in improved results.
We're offering the following product (and will be making own own better alternative ASAP) specifically for that purpose, so that you can be legal when off nitrous and maximise the results when on nitrous. Such a device can be worth up to a second or more on the 1/4 mile, depending on how bad the exhaust is originally restricted.
http://www.pdfdownload.org/pdf2html/vie ... alogue.pdf
Last item.

That must the culprit. That catalytic converter chokes the engine when on the gas.
I have a decatted racemanifold on my car and it`s a night and day difference on and off the gas.
See if your can get a decat pipe. B.T.W. What diameter exhaust do you have?
While I was away typing, you beat me to it Paul - LOL

One other thing that can have an adverse effect is the ecu. These modernday ecu`s have all kind of safety measures to keep the engine from knocking itself to death. But they can be overacting.
On my car for instance there is an active knock control system retarding ignition, but not when the knock sensor detects pre ignition but when it thinks the engine will detonate under certain engine loadings or fuel quality limits.
The detonation sensor is also a very crude one. It doesn`t have filters, so it picks up frequencies everywhere; road irregularities, noise from my race manifold, short ram intake, sharper cams etc. It even shows engine knocks when I accelerate hard in 1st gear because of my strengthened engine mounts.
I can monitor all ignition settings and detonation via my Hondata flashpro management system and I found that I hardly had to retard ignition advance, even when on a 100 bhp nitrous shot. What I did was compensating by adjusting fueling and cam angles.
The stock ignition advance curves were pretty conservative and the ecu had an overzealous tendency to remove ignition advance when it felt like it.
Don`t know if your ecu is chipped but the engine may be removing quite a lot of ignition lead as soon as you turn the gas on. On these engines as soon as you remove ignition timing you tend to loose a large amount of torque. My engine does.
I was saving all that until we'd dealt with the more common and easiest to deal with potential causes but all very true.

I understood that your F4R 830 engine has a rather high 11.5:1 compression. Perhaps it is possible to have the ecu remapped to make it better suited to nitrous use.
We can now offer a remap that will suit nitrous without having an overly adverse effect on NA performance should anyone need to resort to that.

How would I go about improving the ignition system if it were the problem though?
Just fit a new replacement - it's usually just one that goes down before the others, so the full set shouldn't be needed.

Short of fitting STD leads and single coil pack ignition which would require a very expensive aftermarket ecu.
Different coil options should still work with your existing ECU but you shouldn't need to take that route.
Another temporary option that will prove if the spark strength is inadequate, is to reduce the spark plug gaps. If you reduce them by 5 thou and see an improvement, reduce them another 5 and retest, ANY improvement proves the case.

The cars been mapped in the past, but it was to suit a pair of uprated cams I had fitted with no nitrous usage in consideration?
Was the timing advanced do you know and if so that could well be an alternative cause or at least a contributory cause.

The exhaust is 3.5 bore from block to tailpipes. I will get the cat cut out the manifold and tla decat pipe welded in. It's an expensive job as the subframe must be dropped to remove it but I'm willing to try anything.
It doesn't matter how big the exhaust is AFTER a restriction like the CAT, as it's TOO LATE by then. 99% of the exhaust could be 10" in diameter but if just 1% is 1" I/D it will be little (if any) better than a full 1" bore exhaust.
Some years ago I had a customer purchase one of my Rover V8 ignition systems (NO nitrous involved), which was guaranteed to make more power over his original. After he fitted it he dyno'd the car and called me to complain, that it made LESS power than before, so I asked him to bring the car for me to look at. A few hours later I heard a very strange sounding V8 pull up outside my premises, which turned out to be the car to which the ignition had been fitted. It was obvious to me (just from the exhaust note), that the exhaust was being choked, so I looked under the car and noted that he had 2 large diameter pipes from the manifolds, connecting to A SINGLE SMALLER BORE pipe, that then connected to 2 larger bore pipes that ran to the back of the car.
I pointed out the stupid nature of such an arrangement and explained, that although my ignition system was increasing the power, the exhaust was effectively being MORE CHOKED as a consequence (more power makes more exhaust flow), hence the lower dyno reading. He removed the small section and fitted a suitably sized pipe and repeated the dyno run, which produced the expected result.

Can anyone confirm the max extreme settings are correct and the injector nozzle is at an appropriate angle???
There isn't a clear cut answer to the injector angle and the best way to determine the optimum position, is to carry out static tests with it pointed in different directions - the one that gives the best results is the best position.
I didn't see any problems with the Max settings but I'll have Ant double check them as he has more expereince with them.

I was fascinated by these exhaust dump valves you pointed out to me Trev, but unfortunately as you can see from the next photo of my manifold ( upper one is the OEM ) there would be no place to locate it before the cat! Cutting the sole remaining cat out wasnt a route i wanted to go down as my car currently runs 95 decibles, the common trackday limit.
You could add a T or Y piece with one of these exhaust dump valves on 1 leg (as early as possible in the system), then have the required silencer on one the other.

See below the picture of my manifold and the modification im intending on doing if you think it will make a genuine improvement to the nos performance?
I've no doubt it will be improved but I'd aim to avoid that ABRUPT change in cross section, as it drops from 2 to 1 pipe, as it would be even better with a decent taper between the 2.

i want one i want one....this bugger has 2 http://www.youtube.com/watch?v=QJ-t094ow-g

Well firstly its worth mentioning off nitrous is has made the car abit of a pig to drive. A massive flat spot between 2500 and 3000 rpm is literally like a 4 cylinder misfire and the car halts. Also seems generally less torquey over the whole rev range.
I'm VERY surprised to hear that and are you sure that it's not due to some other issue that occurred by coincidence, at the same time as you switched the pipe.
IF the pipe is the cause of the problem, then it could only be due to needing a remap of the fuelling and then I'm CERTAIN that you'll see worthwhile benefits throughout the entire RPM range.

On nitrous... its difficult to tell really, its definately louder so it could be a placebo effect.
Louder generally means more free flowing and that should result in better performance nitrous performance.

I moved the bottle outlet to a 45 degree angle for transverse mounting and that definately helped as before a half full bottle was giving me little effect, now i have full effect to around 1/4 full bottles.
Very good.

Possibly a little quicker but the nos still lacks the improvements of the other car.
That indicates there is some ENGINE related problem.

I was at North Weald drag day yesterday and used it as a good proving ground. Over a quatre mile run the car runs half a second quicker with nos than without, is this about right for a 50bhp shot?
That depends on the car, conditions and the driver, so its impossible to judge from that statement.

Another note is that the car still white smokes like a pig when on nitrous down the strip, so much so that the commentry even warned me over the mic that my looked very unhealthy and he was worried about its remaining lifespan with nos?
White smoke is usually caused by water - are you using any water? A 'potential' explanation is that your head gasket is weeping when using nitrous and water is entering the combustion chambers. The gasket weepage would explain the less than impressive results as well as the white smoke. It might also explain the issue with the mid range problems.

I was at North Weald drag day yesterday and used it as a good proving ground. Over a quatre mile run the car runs half a second quicker with nos than without, is this about right for a 50bhp shot?



So was I??

Black MGB with supercharger.... If I knew who you were i may have been able to help ??

With regards to the head gasket, it has been compression tested and passed okay and it doesnt lose a single drop of coolant over many thousands of miles both on and off nos.
I can only think that there must be a great deal of condensation built up or generated in your exhaust system that get's blown out when on nitrous, as I can't think of any other explanation. I believe we've had a similar report once before but it's so long ago I can't remember what we determined was causing it.

I used the whole bottle at north weald last week on a 17 run crazy day. Is it worth checking my plugs for colour?
You SHOULD ALWAYS check plug colours and if you fail to get a better improvement from anything else, then I suggest you change the plugs for a new set. What type and number is standard and what type and number are you using now?

Static test was carried out by Julian at ActiveNitrous, a good friend of yours im told?
He seems to know his stuff so im assuming i can trust him when he tells me that the static test was fine.
Yes he's a good and informed guy, who has been an agent for longer than most other trade customers, so I'm sure his assessment will be correct.

I dont know my fuel pressure, whatever the standard pump runs.

I have a bottle heater fitted and always active yes, it runs at 950psi.

My jet sizes are as follows:

Fuel = 40
Nitrous = 100
OK on all the above

Will take plugs out this weekend and post pictures, i've also just ordered the spark strength tester from your site so hopefully that can tick my ignition off too
Wise move on the tester but can you tell me what plugs are standard and what you have fitted now and if they are new or not please?

I`m still baffled by this white smoke coming from your car when on a nitrous run.
Me to.

The smoke comes out of the exhaust pipe and only when on the gas right?
And not from somewhere else?
So it is reported.

Is it possible that there is a pinhole in one of the exhaustports of your cylinderhead letting a bit of coolant seep into the exhaust? That could explain the smoke.
That or the head gasket leaking under nitrous combustion pressure was my guess but Ben reported NO loss of coolant, so that seems to rule that out!!!

Paul.