P20SPD

iTrader: (1)

Some of you will know that i run the HKS Hiper on my car coupled upto a H&S 3" downpipe and OBX headers, well until recently anyway.

The car ran fine up untill i removed the headers, due to selling, and replacing with standard unported headers and up pipe.

Most of the time i run with the bung in the back box, just to keep noise levels down, as i do a lot of miles each week. However i do take it out now and again, just for fun.

After putting the standard headers back on, i have suffered some really violent miss fires in 3rd 4th and 5th, basically once the car had got hot, perhaps too high an egt?

I couldnt be bothered checking it out, as some new headers will be with me shortly, but out of curiosity i thought i would remove the bung to see what the effect would be.

Strangely, the missfire has completely gone and if i put the bung back in, the miss fire returns!

I seriously didnt think the bung could make such a difference, i assume its EGBP thats at fault?

Another observation is that the car has turned into a bit of an animal again, easily able to spin all 4 wheels in 2nd, and even get some wheel spin in 3rd in the current weather conditions.

I honestly cant believ how much of a difference it has made!

Will the bung go back in? more than likely once i get fed up with the noise again.

Steven

Jolly Green Monster

iTrader: (4)

Have you tried tweaking the Link Map?

You might find it is running rich on the standard headers with bung in and causing a miss?

Is there any associated knock when it misses?

Whilst mapping mine I have noticed two things occur which I was surprised about.. get the cruise slightly two lean and then if you cruise along and then go on boost it will knock due to preignition (hot spark plug or similar I presume) or if the on boost is too rich then it can miss or knock.

Stick the Laptop in the car and log it with and without the bung to check the OXY I suppose?

Simon

Chaddy

Depends very much on the configration of the internals of the box, obviously with the bung in the gas is diverted around an alternative route through the box which will obviously increase backpressure. It is quite common for the alternative route to be solely through the holes in the perforated tube, and these can partially, and occasionally totally block, either with carbon, debris such as rust scales, or bits of packing material..or all three mixed with condensate! I have seen boxes of the flow through holes design, totally blocked, to the point where the engine wouldn't run. This may, or may not be your problem, but it sounds like you have a big difference in backpressure with and without the bung. Just thinking about it some more as to why it should have occurred after changing the headers, it is entirely possible that you have dislodged some debris whilst changing the headers, and this is now stuck in the flow holes in the box. The only other reason I can think of, is that the ( presumably equal length )headers were more tolerant of high backpressure, which is possible, as the longer primaries do help to stop cross contamination, or backwash, i.e gas from one port flowing back into another, grasping at straws now !! hope this helps.
Chaddy

jameswrx

iTrader: (4)

I'm glad you said that because the bung really does make alot of difference to performance that I've noticed aswell. Bung in.. the car lacks spool, feels wooly and is noticably down on performance.

I bought mine so as not to annoy my neighbours, but it was too awful to keep in.