A few people have expressed they believe nitrous backfires they have had (on all make kits) to be linked to running wasted spark coilpack ignition.


The theory is that the spark which occurs on the waste cylinder can ignite the charge in the inlet.


My own view (and experience of DIS cars running wasted spark) is that this is not a risk, but i would be interested to here the views of others?


Surely if this WAS a risk it would be a risk on any car running batchfire injectors and wasted spark as they would also risk ignition of the fuel on the wasted cylinder?

If anything i would propose that the prescense of nitrous to cool the inlet would make it less like to happen?



Your views/experience/opinions please????

 

For this purpose call Adrenaline Race and Performance for our inlet Burst panel kit.

 

i'm also inclined to think that the risk is low.

if the petrol burnt that easily in the inlet plenum, why does the engine normally bother to compress the charge?

 

How sure are you thats what happened Danny?

No disrespect to your opinion, but its just ive seen seemingly near identical backfires on cars that dont run wasted spark too

 

is NOS on it's own highly flammable chip? or do you have to release the oxygen somehow during the combustion process?

 

Until it reaches a few hundred degrees its as flammable as co2, you can actually use it to put out fires as it starves them of oxygen.

IF there is any risk at all, its not from the nitrous, its from the extra fuel from the nitrous kit, the nitrous itself will NOT aid the combustion in the inlet until its already well and truely started anyway.

 

I Thought you would know the answer to this chip
Dont you post on the wizards site
does trev know
my old inlet is orbiting the moon
have been to scared to run it on this new engine

 

I think i know the answer, which is that i dont think its a risk.

But i havent conducted enough tests to be confident my opinion is definitive, hence this post to try and find out what others experience is.

And yes ive just posted this same thread on the nitrous forum to get info from their too.


Ive personally nitroused several DIS engines with wasted spark, including increases of 100% power, but ive NEVER had a misfire linked to that.

Ive only ever had one nitrous related backfire in fact, and i know what caused that as it was on engine startup!



Ive not discussed it with Trev yet, so hopefully he will respond on the nitrous site.

 

mine was my own fault as trev pointed out to me but im still aprehensive to use it as i dont want to damage anything
i may just change my ign system to what Karl has sugested for peace of mind
and see how it goes from there

 

I dont know the details of your failure (sorry if you have told me and ive forgotten but i speak to a lot of people about gas) so its impossible for me to comment on it.

Can you tell me what happened?

If so, we can at least hazzard a guess if wasted spark will make the slightest difference or not?

 

I've seem it happen without wasted spark also, EFI or even Carb and a basic coil it can happen, Dont get involved with the why but it does happen so now do the burst panels as this is a cheap alternative to replacing inlets or sometimes the whole motor. they look good also.

 

LOL Fair enough Danny, sounds like a good workable solution to the problem.


I personally think people are barking up the wrong tree with the wasted spark, unless they are running wild cams with lots of overlap, but i can understand the logic of why they think it but i just havent seen anything conclusive to support it yet.

Got any pics of the blast panel?

I take it that it involves chopping a hole in the plenum and then bolting on a thin piece of ally or something like that?

 

will post pics tomorrow, you got the right idea though, each panel has a 70psi breaking point so should anything happen the relief panel will split.

 

Sounds like fantastic insurance

I might actually look into doing something similar as im going to be using an inlet manifold thats custom made and so not easy to replace if it happens to me.

I was thinking of possible a section between the inlet and the TB, so that if the TB is shut the blast still has somewhere to go, rather than have to modify the inlet itself?

 

Good topic

I was under the impression that the possible risk of it happening with wasted spark was dramatically increased when running cams with long duration/overlap.

 

Thats possibly true, although again ive not presently seen any evidence of it.

Turbo cars typically run LESS overlap though of course, so arguabley are less likely to suffer than a N/asp car.

 

Why not fit a high speed pressure relief valve to the plenium, set at 3 or 4 BAR Or is the explosion too fast for any relief valve available?

 

Im not aware of any valve that would work in the case of an explosion.

 

I read a post on one of the Skyline forums where some guy had blown his trick Veilside plenum and its was the general consensus of opinion that it was due to running wasted spark CDI ignition and 290deg/hi lift cams. A lot of hipo road GTRs are running 272+ deg/high lift cams [mines running 282 deg/10.8mm lift] so its one of the main reasons that I dont want to run wasted spark CDI.

 

Cam, i assume that his failure was not on a nitrous car?


As the thing that people seem to be completely missing is that this is a risk irrelevant of wether nitrous is used or not if you have a batched fire injection system.

 

Sorry should have made it clear it was on a NOS equipped [125 shot IIRC]GTR but others posted that they had experienced the same on non NOS GTRs running big sticks [270deg plus/highlft with plenty of overlap]. I think it was on SDU but I cant find the thread at the moment.

 

ITS looking grim on the wasted spark system

 

I will be prepared to risk mine on gas , IF i can get a blast panel fitted, not gonna risk it without.
good discussion but we need more facts

 

My engine management is a batchfire, wasted spark only. And it´s got a nitrous controller built in. Can´t be too dangerous with the wasted spark, I reckon.

 

ahh but what duration cams r u running ?

 

More than any of the "off the shelf" BD turbocams available.

 

This is an age old argument that cannot, technically, ever be satisfied by a definitive answer.

There is of course a possibility of the fuel in the inlet runners igniting when the spark from a wasted spark system fires on a dead cylinder that still has an intake valve open.

The problem with the argument is the fact that it is just as much a danger on a system not using nitrous, especially one running batch fire injection, as that is essentially the same thing. The NOS is rather irrelevant given its inflamability at the intake runner stage.

I know of only 3 cars that have ever had an issue this way, and i look after well over 100 Nitrous equipped cars, a good 50% of them running WS ignition systems. An example many of you on here will recognise is Lee Catermole (TiB) How long has he succesfully ran Nos and Wasted spark with 500bhp and a healthy dose of NOS? Yes, years. He is one of many many thousands i assure you all.

All we can do is view it as another very small but real risk, just one more of many we run when we modify our cars for more performance.