NITROUS OXIDE ( nos / n2o ) advice forum

Hi

Looking for some advise

At low boost 15psi and below car runs spot on.
However when I run my boost it starts to misfire -the higher the boost the worse it gets.
I also get this when I try to add nitrous ontop of the low boost

I have already changed the leads for 8.5mm magnecors, ngk iridium 8 plugs and even changed the coil for a high output msd version.
Its running on the rich side on boost at arround 11-11.5 afr

Reducing the plug gap from 0.8mm -0.7mm seemed to improve things but I think with a slight loss of power.

Today I also shortened the coil lead -no effect.
Then lastly carried out the rotor arm mod -giving it close to o ohms resistance.

This has made thing double as bad and it now misfires coming on to boost on low boost!

any ideas?
cheers scott

The mods you've made should have increased the spark strength which should have improved any internal misfires, therefore the cause of the problem must be the spark leaking out of the system and making the spark stronger is now making that happen more easily/often.

Make sure ALL your HT connection are good and well insulated.

Route your HT leads well away from metal parts

Make sure nothing conductive, metal components or electrical connectors are close to where HT connections are made, like the HT lead to coil connection.

Make sure ALL the HT components are clean.

If that doesn't do it then replace the plugs one at a time with new ones, testing after each one is fitted. Any that result in less misfires need to be binned and any that don't improve the misfire can be kept as spares.

yeah leads are all good route.
did the same misfire on old plugs also

could the rotor arm being too far away from the dizzy cap points cause it as it looks quite a big gap?

heres a vid -it happens at 1min 9sec in vid
http://www.youtube.com/watch?v=g-YflLKZEHo

A large rotor gap might cause it but only if its bigger than normal and because its out of phase, which may or may not be possible.

A cracked cap could cause it.

You might like to drop Ant a line on ant@noswizard.com as he had a Tomcat and may have 1st hand experience of such a problem.

Lift the bonnet when it's dark and preferably damp (Like very early morning / late evening)
Start it up, preferably from cold.

With any luck you'll SEE the blue/white sparks and maybe even HEAR the sharp little cracks they make.

If you DON'T have a pace maker and are as stupid as me, run your hands along each lead in turn, especially near the ends and where they cross while listening carefully.
But be prepared, if you find a short this way it could well bloody hurt.
If the short doesn't hurt the reaction of pulling away and hitting something else will.
But you'll have found the problem...........

Hi Loopy

I did the "run my hands across the leads trick" once on a Mustang lollllll

I did not realise it had a Mallory coil on it that guarantees 50,000 volts at the plugs !!!

It blew me across my workshop, and yes it hurt lol A LOT !

Visual inspection in the dark works much better lol

Or stick a timing light on each lead and watch for irregular flashes....

All the best Brett

Loopy? more like certifiable

Some of us have a higher resistance than others.
An MSD on a sidecar outfit left me with a numb arm for the afternoon, Owner wouldn't go near the fecker after it belted him accross the pits........

It teaches you two things though, sparks can leak and sometimes too much really is too much !

right checked all leads all good
tried std coil king lead - no differance
checked coil resistance etc -ok and its clean.
changed plugs to some new racing ngk non resister 8's gapped to 0.8mm

car actually feels more responsive and really smooth right until the boost comes up and then it misses like a ......

going to try a new original rover part dizzy cap next, then a std rotor arm

hopefully this might help!

no sign of sparking in the dark and earth connections all ok.

spark tester time i reckon, everything youve said points to a weak spark
could be the coil ignitor thats weak, its the only thing you havent changed as far
fitting new parts is no guarantee of a correctly working ignition system, you need to test it

Is that a part readily available for cheap money?
cheers
Scott

i bought mine from WON, im not sure if they have it on the website yet
but they do sell them

http://www.noswizard.com/product_desc.php?id=104

sorted, £9 plus vat

20mm+ gap has to be jumped for a spark thats reliable with nos
on that type of tester you have to open it beyond its max slightly
like so


copyright of image Highpower NS LTD

hope its ok to show a picture from your book trev to illustrate the point

cool just bought one

be interesting to see what it is

i had all sorts of issues scott till i bought one of these
at the very least youll know whats going on, it seems youve done just about everything to be sure the spark is as strong as possible

btw how did you seal over the rotor arm?
i was stupid and used a hot glue gun
100bhp shot of nos going down the quarter at the pod, the glue melted DOH
with the spark arching off the rotor whenever it felt like the headgasket melted and i dont mean it blew, it melted!

X2 OBVIOUSLY - so why did I assume it was too strong (even though it does cause similar results), I can only assume I'm past it now.

still going to check the spark strength.

however got a new dizzy cap and rotor arm yesterday.

fitted the cap - no noticable differance although it must have been better as the gap was about 2-3mm less to the rotor arm to the cap points!

Fitted the new rotor arm and touch wood seems perfect and now running 1psi higher boost without touching anything -I guess thats probably the larger plug gap though.

thanks for your help -fingers crossed it goes ok at the weald next week


still not sure why the modded rotor arm caused issues though
checked it again 2ohms across it on my meter and i filled the new cable in with super steel cold weld

as long as the melting temperature is high it dont matter ( plus what u fill it with is non conductive )

that stuff is only rated to 150C so im not 100% that it would be ok

What does your meter read when the leads are touching ? 0.00 or 2.00 ? because 2 ohms accross a modded rotor arm is a lot !
It's also possible the rotor tip is burnt away but are you sure the cold weld is non conductive ?
The alloy version has alluminium powder in it and the Iron version has iron powder in it.
Not enough to really show on a meter, but enough for HT voltage to jump

yes its 2.0 ohms

I will buy a spare new arm and try it again.


however I recieved the spark tester .

spark similar on all leads

Up to 25 gap fine once I get to about 28 it starts to cross arc -Is this pretty good?

can you put a pic of the spark tester in the max position??
mucho easier to tell by lookin at it