Mad Hammer

iTrader: (55)

Ok, I posted a couple of days ago about setting up of my knocklink on my MY98 STI 4 RA V-Ltd with full de-cat and recent high spec re-build. Just trying to work out what to do next.
Got the knocklink on max and only get one light upto 6000rpm but after that it starts moving up the lights! This was on optimax and millers booster.

I have now got a tank of Esso SUL plus millars and have let that get into the system. So took it out tonight warmed her up and tried my luck, same thing happened so obviously backed it off.

I have order some colder NGK plugs as I believe the chap that owned it before put HKS items in. Will this help?

Made enquiries about re-map but this seems to be a little tricky for the 98 spec STI engine.

Any other suggestions ?

Cheers

ozzy

Do you have any other gauges? AFR, for example?

You really need to know more information to assess what's causing the det and if it actually is. You should air on the side of caution and assume that the ativity is det until someone can confirm otherwise with a set of det cans.

Have you tried adding some more OB or are you using the same amounts all the time?

Stefan

Mad Hammer

iTrader: (55)

Have bought an AFR too, going to fit that with boost gauge that's on the way. Only used one bootle of booster each time, do others use more ? Can you explain what the problem is if it's rich aor lean at higher revs ?

ozzy

Sorry, I'm not experienced enough to give you a detailed explanation, but you certainly don't want the car running lean or too rich as this will alter the combustion.

I would suspect poor fuel quality first, so you should try some extra Millers or even get hold of some NF. The japanese cars are mapped to run on 100RON fuel and you need to get to this rating with good fuel + OB.

You really need someone to listen with det cans and then get the car re-mapped. The de-cat will exacerbate the problems on a STI.

Some good articles on det:-

http://www.streetrodstuff.com/Articl...ne/Detonation/
http://bbs.22b.com/cgi-bin/ultimateb...=000548#000000


Stefan

Mad Hammer

iTrader: (55)

Did not think of the decat causing a prob, worth putting the front cat back on then ? unless a second bootle of booster does the trick

zhastaph

Howz about boost guage? The decat on an STi will most likely cause boost spiking, anything over 17psi (from a standard map) and you've got a good chance of seeing det

Mad Hammer

iTrader: (55)

I really should have thought of that as have read that before. This is my first STi after having a UK car for 3.5 years. I have the downpipe cat from my old car, could fit this although it does not have the hole for the second sensor at the bottom of the pipe. Excuse my ignorance but what's that for ?

ozzy

Isn't it for another O2 sensor. I'm sure the older models have 2 - manifold + DP.

Yep, DP downpipe will cause issues on a japanese STI.

Stefan

Mad Hammer

iTrader: (55)

That means I need to get hold of a downpipe with cat with two holes. bugger! I would rather lose a few bhp and be safe as it seems remaps for the 98 STI engine are as rare as.....well you all know.

Anyone got a pipe they would like to donate ? Sure a new one will cost a bomb!

Mad Hammer

iTrader: (55)

That means I need to get hold of a downpipe with cat with two holes. bugger! I would rather lose a few bhp and be safe as it seems remaps for the 98 STI engine are as rare as.....well you all know.

Anyone got a pipe they would like to donate ? Sure a new one will cost a bomb!

ozzy

I've replied to your other post. AFAIK the downpipe had one sensor - O2. The other sensor was in the headers/manifold, but that could be older cars (e.g. <97). Only other time I've heard about 2 is with an EGT sensor probe.

Sorry if I'm confusing the issue.

Stefan

Mad Hammer

iTrader: (55)

It's definately got two sensors in the downpipe. Top of pipe where they all are and the second one is towards the bottom where it meets centre section. I have seen de-cat pipes before with two holes, in fact my old one on my UK car has the second hole so I blanket it off with a bolt.

Clive

dowser

When you say it starts 'moving up the lights' after 6k, does it slowly rise or are there quick spikes?

Maybe the rebuild used aftermarket pistons with greater tolerances and are just causing background noise? In *general* more leds slowly lighting up as revs increase do not indicate det, but background noise. I'd suggest getting some det cans onto the car and confirm what it is the KL is actually picking up.

Richard

Houghton

iTrader: (1)

Just looked at the OE exhaust system from my STi3 and there's only one sensor hole, at the top the down pipe.

Mad Hammer

iTrader: (55)

When car gets to higher revs it spikes (straight from green to the red !) I have only tried this twice once with the optimax then with the Esso.

Details of rebuild inc -

Steel con rods,
Ross forged pistons,
New mains,
New B/ends,
A.R.P head bolts,
New Cambelt,
Uprated Oil Pump

I have beed told elsewhere that the second hole in the downpipe is for the EGT sensor and it can be disconected. Don't know what this does though ?

Sounds like I should try my old cat downpipe to see if this stops what looks like spikes of boost causing my problem.

Anyone agree ?

Dark Blue Mark

Standard fuel pump and reg will not be able to keep up the fuelling at high revs, with a decat on an STi. IMHO

Ive seen det on mine with this setup. speak to Mark at lateral Performance.

MB

Dark Blue Mark

PS - dont find the need to take mine over 6000 rpm

Either get an FSE uprated pump and reg, or get the cat back on.

MB

Mad Hammer

iTrader: (55)

Thanks to everyone for the advise, looks like I now have the solution.

Will get the cat on this weekend as I have a Hiper to fit rather than the full Mongoose decat fitted when I got the car last weekend.

May go for the de-cat and uprated fuel pump at a later date. This car is plenty quick enough for me after a modded uk car!

As for more than 6000rpm, I don't under usual circumstances but I don't want the worry of detting engine if I did creep over 6.

Thank again.

Clive

Dark Blue Mark

Just one more point, MY98 MAF's are quite relaible, but may be worth checking that its not the MAF failing thats causing lean running. They are pricey though, so you need to be sure. Mine actually would start lighting up at about 7k+ rpm, (mis information in my last post!) so a bit higher than yours, hence im questioning the MAF. Other things suh as the fuel pressure / flowrate could do with a check.

Having said that, you could just do what I did and but the cat back in and see if the prob goes away. Im happy running mine with the cat now, and dont really notice much power difference to be honest...

On your downpipe, there will be a cat on fire sensor (not needed with a decat) and the one for the lambda,

MB

Mad Hammer

iTrader: (55)

Ohh that's what the second hole is for! I have no second hole on my cat pipe so will have risk burning fur

Dark Blue Mark

Can you let me know if your det goes when you put the DP on?

MB

Mad Hammer

iTrader: (55)

Will do fella

Mad Hammer

iTrader: (55)

Well, 3 hours and bloody knuckles to prove I put cat on and new Hiper system. Now only getting a 2nd green at 8000 rpm. Problem solved

Dark Blue Mark

Ta for letting me know, always good to conclude on these things. Proves the fuel pump cant cope though....

Lesson to any other decatted STi owners with no knocklink

MB

Mad Hammer

iTrader: (55)

Couldn't agree more cheers for the help, uprated fuel pump must go on the list though.