alfriedesq

Bump - - anyone fic the problem yet ???

BretMan

As mentioned in the thread, mine is fine now.

The lesson is that if you put on a decat downpipe without checking it out you WILL get boost spiking up to 1.7 bar (although the fuelling at 1.7 bar is still apparently okay!). To solve, I recommend contacting someone who is a specialist without an axe to grind (i.e. they are not selling you an EBC!) who can modify the restrictor appropriately, ideally using the Subaru Diagnostics (or ECUTEK's tools) to verify all is well afterwards.

After mods, max spike should be around 1.3 bar.

The result is much improved throttle response under 4000 rpm, more progressive acceleration and stronger performance after 5000 rpm.

The only other point is that replacing the factory up-pipe seems to make things worse - so best to stick with stock.



[Edited by BretMan - 5/13/2002 10:09:20 PM]

alfriedesq

BUT you still HAVE a boost spike

Before when i was running the 02 US WRX motor with VF 30 and Blitz SBC boost controller there were NO boost spikes - - I;d like to eliminate all boost spikes - !!!

alfriedesq

Problem fixed - see my other topic for details -- just put on a bigger turbo with upograded wastegate acutator

BretMan

That is not really a practical solution for those who don't want to buy a turbo!

Its overkill, and really not necessary to solve the issue.

The boost spike seems to be engineered into the factory boost control and with an EBC (at least a basic one) you are simply going for a flat boost level.

The factory ECU has quite a complex set of target boost levels at different revs and so on which you throw out the window if you use an EBC (at least one with a single fixed target).

Modifying the restrictor and possible switching to a 3 port solenoid can solve the issue and return to stock boost levels.

I'm not questioning that you have no boost spikes, but just saying that much cheaper alternative solutions can give an acceptable result.

mutant_matt

.....still asking.....anyone know *why* and *how* the 3-port helps solve the problem????

Matt

Dave T-S

Matt

The feedback I have got is that it appears to be able to react to the initial turbine spool up which causes the spike better. Simply, it opens the wastgate quicker.

BretMan

Guys: we tried it over here on my STi and found *poorer* boost control than with a 2 port.

It was much less stable and actually slower to catch the boost spikes. With the 2 port though, and just a restrictor mod, I reconfirmed with the Select Monitor that we only have only a max spike of 1.26bar, so it seems fine.

Its strange that we seem to be getting different results with NZ/JDM spec models over here than you are in the UK?

I'm getting the boost gauge on next week as additional insurance to keep an eye on it in heavy load conditions.

jonno

Hi guys
sorry havent had time to post on this.... will try and explain

27/3 Fitted a three port instead of the factory two port with a 1.25mm restrictor in the return pipe.....no restrictor in the feed pipe to 3 port. Tryed different sized restictors and found this to be best as it was pulling back too much.

The three port controlled the boost very well, didnt spike whatsoever. It was totally controlled all the way to 1.2-1.3 bar depending what gear i was in and didnt seem to spike at all.....

Trying to catch it out.....

Initally after fitting it, i tryed to catch the thing out and could only get 1.4 bar realy trying ..5/6 gear 5000+ rpm boot down!!!.... Untill last week, had a spike of 1.6+ bar, dont know when exactly it happened and under what conditions as i wasnt trying, i reset the defi everytime i drive it so i know what my peaks are .......

So the three port controls it better but is not the answer!!.

Hope this helps .

Thanks Jonno.

BTW, i have my Delta dash traces from PE RR day when i ran with my 2 port if any one wants to have a look at them as i dont have the software for them and couldnt understand anyway.

Razor2001

Excellent thread guys.....

Keep the info coming as I will soon be going the decat route and will have to do all the work myself with only a boost guage as my guide to keep my engine from blowing up.....so I need a tried and tested decat system before I can put it on my car

What a superb source of info ScoobyNet is !!!!


Thanks again for all the info !

Ray

BretMan

Jonno:

You can download the Delta Dash demo version from ECUTEK's website and display the logs on-screen.

I'd be interested to see them... my email is in my profile.

Cheers,

Bret

Razor2001

Hi guys,

Where are the two cats located on the Japanese spec STI 7 ? One after the downpipe and one right before the mufler box ? I assume both are removed when changing exhuast from turbo back (downpipe back to exhuast tip) ?

After removing both these cats do you just pop the 02 sensors into (via a small hole) the new decatted exhaust and no worries about the CEL issue ?

Does anyone know if there is any performance companies working on a full turbo back (ie: downpipe to exhaust tip) for the Japanese spec STI 7 ? It would be good if they sold this kit with a modified restrictor which would make the whole system a simple bolt on package that did not cuase boost spike. They could even throw in a boost guage into the package I would be a buyer, and all in one decat package that one could install themselves

Cheers,
Ray

Razor2001

bttt

mutant_matt

Jonno,

I've been looking at your PE DD traces again and:

1. you are peaking (and in some cases) holding 18.4psi (1.26bar)
2. you are never peaking above 18.4/1.26
3. you are usually holding around 15psi (just over 1 bar)
4. the Ignition Timing usually takes a serious dip around 3000rpm and recovers around 4500rpm
5. the boost is not very consistent

Can you please remind us what exhaust/restrictors/solenoid you were running at PE and can you remember what boost was showing on the gauge at the time? What was the Defi reporting for that run (if you know)?

Did you get my mail from this morning?

Matt

jonno

Hi Guys,
Bret, YHM DD traces as requested, (have looked @ figures & more figures cant work it all out!!.

Ray....
Only one cat on my 01 JDM sti thats in the down pipe, none in the up pipe and only a resonator in the centre section.

I have had no probs with the CEL on mine, been Decated now for nearly 3k.

I think a few peps are working on a fix, some say they have sorted it out with a restrictor change, havent tried a restrictor change may look at that next, unless ..........

Matt, thanks for your mail, more mail returned, while i was at PE i was running the 2 port and had SS up pipe/SS down pipe and HKS TT C&R i dont recall what the Defi was reading on the rollers that day, they said it was overboosting 1.7+bar and was not controlled, as it was all over the place, hence different results on every power run.

I will try have a good look at the DD traces tonight.

Hope this helps
Jonno.

Deep Singh

Had mine decatted today at Scoobysport.Its a JDM Oct 2000,as far as I can tell two cats.I replaced down,mid and backbox but not Up pipe.1.25mm restrictor in the return pipe.Max spike 1.2 bar holding 1.1-1.15 bar.1 bar boost being achieved at about 3000-32000 rpm.No det on the Knocklink(Optimax and Octane booster).Pulls better low down and better up top and sounds good.
Excellent job done by the Essex gang! Now that this works I'll be having the up pipe done and heads ported as the Link gets nearer.Hope this helps

Razor2001

Hey Deep, congrats man !!! Hope it keeps working well for you.


Please clarify.....you have a JDM STI -7 (Bug eye) ? The '2000' confused me ?

There seems to be conflicting views on the stock setup, you say two cats ? others have said one cat ?.....where are your cats located ?

Finally, can you supply a contact where I can get ALL parts needed to perform the mod you did ?

Thanks,
Ray

RT

Deep, 32000rpm?! (sorry, couldn't resist)

Can you try this - cruise in 4th gear light throttle at a steady 2700rpm. Hold that for 10sec. Now, RAPIDLY put your foot down, giving it WOT as fast as possible. Watch the boost gauge carefully. Do you still get a max spike of 1.2bar ONLY?

If so, I'm taking out my restrictor and drilling it out to 1.25mm!

Plse try and let me know. I'm very interested in hearing the results...
Much appreciated.

For the record, yours is a MY01 JDM STI, right?

Pete Croney

Hi Guys

I did all the road testing with Deep and we were seriously trying get it to spike.

5th gear WOT from 3,000 to 4,500, lift off to drop the boost and then nail it... No spikes over 1.25 bar and boost held steady at 1.1 bar.

WOT in 4th up from 2,500 to 6,000+... Builds quickly to 1.15 by 3,200 then smoothly drops to 1.05 and holds this all the way up.

6th gear, steady throttle at 4,000 then WOT. Builds instantly to 1.2 then drops to 1.1 and holds steady.

The car feels very nice. Its power delivery is very smooth and it is away at 3,000 better than the standard car is at 4,000.

With regard to CEL issues, we also fitted the Scoobysport Active Rear O2 signal modifier.

Not only is the car spooling up and pulling much better than standard, but with the spikes reduced from what people are seeing on standard cars (1.4 in some cases), its also running a lot safer

Deep Singh

Can confirm all Petes comments.Gave it some real welly on the way to work today,no more than 1.25 max spike at any point,any gear.I'm acheiving 1 bar boost at 3100 rpm in 5th gear.The car holds a steady 1.15 bar boost,no knock.
When I said 2000,I meant that was year first registered in Japan(yes STi7/Bugeye.)
As far as I can tell two cats.One in the DP,and one in the midsection.The mid had two bulges,I presume one is the cat one a silencer but could be wrong.
Razor,Scoobysport can sell you everything you need.
Pete,I hope you're sitting there right now figuring out my lights mate!

Razor2001

Thanks Deep,

I will contact them

Ray

RT

Cheers Pete and Deep!!
I'm off to drill out my restrictor to 1.25mm.

Deep, I think the mid-section only has a resonator. I looked into mine when it was off the car and I could see right thru it. No fins of any sort that a cat would have. To the best of my knowledge, the JDM STI only has 1 cat, and that's in the downpipe.

Razor2001

Hi guys,

Sorry to be a pain, but anychance someone could post a few pics of the 'restrictor' and where it is located in the engine bay ?

Can the job of making it bigger, (ie: drilling it out) be performed with a standard drill and drill bit ???


Cheers,
Ray

Deep Singh

Sorry mate did'nt pay that much attention when sccobysport were doing it.I know its in what they call the 'return pipe'.Why d'ont you just get Scoobysport to mail you one out,perhaps a selection ie one size bigger one smaller just in case your car responds slightly differently.I'm sure it would'nt cost much.

mutant_matt

Razor,

It's in the pipe which comes out of the Turbo nipple just near the other end where the T-piece is.

Matt

RT

See page1 diagram, in stock condition it doesn't have the RED bits.

Razor2001

Thx guys,

Gonna contact ScoobySport and try and get all the info to get this decatt going. Either will go full scoobysport or perhaps part scooby part Maclennan similar to BretMan

Cheers,
Ray

jonno

Hi Guys,

Deep,
did you have the up pipe changed as well?? if so, thats will make a differnce.
have you a permenant boost guage?? you need to keep an eye on it just in case.
think you will find there is no cat in the centre, just a resonator!!

Cheers Jonno.

Deep Singh

Hi Jonno.I stand corrected on the cats then.No I did'nt have the up pipe done as I thought I'd see how the exhaust did first.Up pipe will be on as soon as I have time.I'm glad you say it makes a difference as it gives me something to look forward to!!

BretMan

I told you guys it worked! (no-one ever believes me )

Interesting to note that both Deep and my cars are JDM spec and both SS downpipes.

I still reckon that split pipe downpipes make boost less controllable, and I wonder if the STI Type UK responds as well to just the restrictor mod?