jonno

Hi Peeps,

Just to let you know ive returned to my two port solenoid and have changed the restrictor, the results are a little releiving and will try another in a few days time as i want to monitor what spikes i may get.

So far seems okay maybe too restrictive if anything but no real performance loss

Jonno

Deep Singh

Keep us posted as to which restrictor gives the best compromise.

Pete Croney

Update...

I just spoke to Jono and the 1.3mm works best with the full exhaust and up pipe.

No spikes over 1.3bar (same as standard), although most of the time the spikes are contained to 1.2bar even in 5th and 6th.

Jono said his car holds 1.1bar and is great to drive

Makes you wonder why some people insisted it couldn't be done/wouldn't work with a full system and up pipe

Dave T-S

Well, I was one of the sceptics, but as he was kind enough to call me and tell me I know Pete's comments weren't directed at me LOL - thanks.

I have felt for some time once more people worked on this it would be got to the bottom of. Jonno, i'll just give you a few weeks to make sure yours doesn't blow up ( ) and may then have to dust down the downpipe in the garage........

Interesting how critical the fix is to the size of the restrictor - 1.35mm doesn't work, 1.3mm does!

mutant_matt

Dave,

I think Jonno told me that 1.35 was too subdued so he went for the 1.3 instead.

Matt

Razor2001

Nice guys, glad you are having success !!!

Just to clarify.....1.25mm for turbo back(full decatt)

1.30mm for up pipe + turbo back (full decatt)

above correct ????

Cheers,
Ray

Edited becuase suppossed to be a question not a statement


[Edited by Razor2001 - 6/12/2002 8:43:28 PM]

russell hayward

"to make sure yours doesn't blow up "

Dave

You mean your warranty when you have decatted dont you ?? !!

mutant_matt

What is the original restrictor size?

Matt

RT

Believe the original restrictor size on the JDM STI MY01 is 0.75mm.

Dave T-S

Russell
If it works and doesn't "blow up" in the first place, the warranty won't be an issue. Reference to "blowing up" was not necessary literal, of course - I meant works properly on a long term basis without harm.

Matt
Without digging out old info that mentioned this, which I can't remember where it is, IIRC the OEM STi7 restrictor is either .95 or .75. The former, I think.

Dave T-S

Cross posted with RT re restrictor size.......

James_Harvey

Great thread folks... Very interesting!

Am I correct in assuming the UK STi7 has no Overboost protection? Do you not experience fuel cut @ 1.5bar???

My UK MY98 fuel cuts at 1.25bar. I replaced the standard solenoid with an HKS EVC IV to fix this... Now peaks at 1.23bar and holds 1.2 bar.

I am about to take delivery of a UK STi7 and am looking to run a Scoobysport DP with Blitz Nur Spec R backbox and some form of cold air induction, using the EVC-IV to control boost. All the talk of 1.5 and even 1.7 bar spikes makes me wonder what levels I should set the EVC to, to keep things safe......

James.

Deep Singh

Pete,thats actually less boost than standard! Mine was spiking at almost 1.5 bar in 5th and 6th.

Pete Croney

Deep we have had another owner of a standard one (Jap) that is hitting 1.5bar in 6th. He wants to keep it standard but has asked us to tame the spikes down for safety.

So that's 3 standard ones that spike to 1.5bar. UK 7s seem to only hit 1.3-1.4 in 6th. Still very poor that they should do it, but I suppose Subaru were trying to get as much out of them as they could, whilst using the latest emission control gear.

RT

Just to revive this thread...

Me being my curious self, decided to try a 1.2mm restrictor hole size in my MY01 JDM STI RA. Std engine, std turbo, std exhaust (with downpipe cat).

Pete C is right. A 1.2mm hole size is overly conservative. Now, I only get 0.9bar max boost - I tried in 2nd, 3rd and 4th, WOT. The boost build is also slower.

But surprisingly, the "seat of the pants" feel is not that much different. I guess running 1.3bar with knock correction for ign timing may be about the same as running 0.9-1.0bar with max advance.

Right now, this seems a fix, albeit overkill, to my momentary det with WOT (2 sudden green LEDs on the KL, sometimes audible). I may want to try a slightly smaller hole, or perhaps chop the std cat'ted downpipe top and weld in a "decat-style" top. This may raise the boost slightly, but not as much as a full decat as I'm sure the cat adds quite a bit of flow restriction...

RT

Tks for the tip John. I don't really have to worry about temp fluctuations climate-wise. Singapore's always 24-32 degC.

Personally, I tend to favour the "neat" approach. I'll prob try different sizes of restrictor (they're not expensive) and then settle for one which I'm comfortable with.

Will try this setup a few more days just to get used to it. Frankly, off boost I feel that its a bit more lively as its not running any knock-correct retard. But of course once I put my foot down, it is slower than before.

Pete Croney

RT

1.0mm seems about right with the standard exhaust.

Spikes are corrected, but boost build is still good.

Razor2001

Hi Pete,

I should be receiving my new SS turbo back exhaust very soon. I think it is in Miami waiting for my friend to bring it in with his next container load for his business

Can't wait to put the sucker on....1.25mm restrictor is still the best choice for the configuration I purchased correct ? (same climate conditions at RT, 25 - 33 c??)

Yeeee haaaaaa !
Ray

RT

More updates. I guess the moral is: "how much power can you live without..." haha

Today I tried again, gears 3 and 4 WOT. Definitely not more than 0.9bar. But gear 5 --> steady throttle --> floor it, gave me slightly above 1.0bar.

I'll leave it in this form for the next couple of days to monitor further. But at the moment, I think I'll be taking the path of using a std cat'ted downpipe modified at the turbo exit (rather than the path of reducing the restrictor hole to 1mm). This is still emissions legal, and I'll be able to reduce lag slightly.

Razor2001

bttt

RT

I did more testing this morning...

From stationary, gears 1, 2, 3, 4 with WOT each time. Am now convinced that the std solenoid runs 2 different routines.
Gear 1 = max boost approx 0.8bar.
Gear 2 = max boost approx 0.7bar.
Gear 3 = max boost approx 0.9bar.
Gear 4 = max boost slightly more than 0.9bar.

While the open loop boost control does allow for higher boost in higher load conditions, this does not explain why boost in 1st gear is higher than boost in 2nd gear. This would confirm my previous suspicions that for the first "pull", the oem ECU runs a different routine to allow a faster spool up.

This routine also prob allows the boost to peak higher (think subaru calls this the "boost achieve" mode?). In subsequent "pulls", the car runs the std routine which prob targets 1bar (called the "target hold" mode?). But since my case is hardware limited by the 1.2mm restrictor, it fails to achieve that level.

I feel that even playing with restrictors and downpipe configurations, we will not get round the fact that the car runs 2 boost control modes, and may not achieve max desired boost on occassion (lower gears), and may spike on other occassions (higher gears). Much as I dislike them, the only sure way around this phenomenon seems to be a closed loop Electronic Boost Controller.

Thoughts?

mutant_matt

RT,

On a completely standard STi that I logged with Delta Dash, I got:

1st gear: 16.7psi/1.15bar peak (but because 1st lasts such a short amount of time, I have no held figure, it's just up to that and back down again)

2nd gear: 14.7pst/1.01bar peak, 13.1psi/0.90bar (ish) held
3rd gear: 16.7psi/1.15bar peak, 14.0psi/0.97bar (ish) held
4th gear: 17.1psi/1.18bar peak, 14.9psi/1.03bar held
5th gear: 18.0psi/1.24bar peak, 16.0psi/1.10bar held
6th gear: ran out of road

I say ish on the held figures because the STi doesn't seem to hold boost as such, more that after the peak, it starts tapering boost down straight away. Perhaps with the restrictor fix, because the peaks are more controlled (even on a standard car), the held is a) higher and b) more consistent/less tapered. As I think we all know, the ECU isn't great at reacting to the peaks and tends to overreact and pull the boost back too much.

Having said that, apart from 2nd gear, it all seems pretty consistent.

On another STi, standard apart from Scoobysport centre and BB I got:

1st gear: 15.2psi/1.05bar peak
2nd gear: 14.1psi/0.97bar peak 13.5psi/0.93bar held (ish)
3rd gear: 14.5psi/1.00bar peak 14.4psi/0.99bar held (ish)
4th gear: 16.8psi/1.16bar peak 14.7psi/1.01bar held (ish)
5th gear: 17.8psi/1.23bar peak 14.8psi/1.02bar held
6th gear: Ran out of road again

Comparing these figures, you can see that the standard car peaks and holds slightly less boost than the SS equiped one. What I do plan to do is to get some logs off cars which have had the full system and the full system + Up-pipe logged as well for comparison.

Matt

Dave T-S

Matt
We must find a longer road next time

Pete Croney

Hi Matt

If you did these tests on yours and Dave's car, there could also be other factors at play. The ECU is adaptive, so will adapt to the driving style. If one car had been driven gently for the previous couple of days and the other had been "enjoyed" the boost characteristics would differ.

The main reason for achieving less boost in lower gears is that the rpm at which the peak is achieved in lower gears is always higher than in 5th/6th because the rate of engine rpm increase during boost build is faster. This means that the "hole" letting the boost out (the inlet valves) shifts more air and so spiking isn't a problem. Its the same reason why boost can't be held all the way up the rev range. In higher gears, the rate of change is more stable and its here that the spiking is worst.

The real test of spiking is not blatting through the gears, as you did (I assume this is why you were running out of road), but by applying WOT at 4,000rpm in each gear.

Its interesting that your boost tapers off straight away though and Dave's doesn't.

Have you driven both cars? How do they compare?

Dave T-S

Pete
The two STi's were mine and Carolyn's

Chances are they had both been "enjoyed" by me on the same routes in the few days previously

Re running out of road, most inconvenient of the planners to put five roundabouts in the bypass we were on

Pete Croney

Hi Dave

Just wondered if the two cars had similar use.

I know you haven't ventured further than the de-cat and backbox, but how do the two compare?

RT

Good good read!! Glad to see some hard data.

I'm assuming here all the "tabled" readings couple of posts up are "thru the gears" rather than Pete's hold-4000rpm-then-WOT technique? I would agree with Pete that this latter method does seem to give the worst spikes.

Matt/Dave, can I plse ask you to try (at your convenience) and see what boost readings you get by holding 2nd gear steady at 2700rpm or so for 5sec, and then WOT? (instead of going thru the gears) Repeat for 3rd gear.

Many tks guys! I intend to meddle more with the restrictor sizes and will report further. 1.2mm seems too big for the standard exhaust setup - 0.7bar in 2nd gear is simply unacceptable!

Cheers

RT

Matt, I just relooked at your figures more carefully. I note that both your examples also exhibit the "2 different solenoid routines phenomenon"!

#1
1st gear: 16.7psi/1.15bar peak
2nd gear: 14.7pst/1.01bar peak, 13.1psi/0.90bar (ish) held
3rd gear: 16.7psi/1.15bar peak, 14.0psi/0.97bar (ish) held

#2
1st gear: 15.2psi/1.05bar peak
2nd gear: 14.1psi/0.97bar peak 13.5psi/0.93bar held (ish)
3rd gear: 14.5psi/1.00bar peak 14.4psi/0.99bar held (ish)


1st gear seems to have a higher peak than the 2nd gear peak in both cars! Of course, the 3rd gear peak is back up due to the increased engine load. Seems like the theory is confirmed then...

Dave T-S

Matt

Yes, don't worry, you did

Don't bet on it matey....

Pete

Most of the time, I act as chauffeur, in one or the other of the cars.

Carolyn's is bog standard, with 4800 miles on.

Mine has decat centre plus backbox, with 1850 miles on.

Carolyn's is quicker. Mine needs more miles on! (or a PPP )

RT

As promised, more updates.

I have now reduced the restrictor size to 1.1mm as 0.75bar WOT in 2nd gear is unacceptable (with the 1.2mm restrictor).

Blasted some of yesterday, but went out for a good-and-proper blast early this morning in the Sunday AM non-traffic.

A.
From a standstill WOT through the gears:-
1st - 0.9bar max and falls off quickly.
2nd - 0.9bar max and falls off (not so) quickly.
3rd - 1bar max and (more or less) holds.
4th - 1.1bar max and holds.

B.
2nd gear hold at 3000rpm and then WOT, 1bar max. Holds momentarily and then starts falling off. I must say that this "falling off" mentioned here and above is only slight, maybe down 0.1-0.15bar or so as the rev's approach 7000rpm.

C.
3rd gear hold at 3000rpm and then WOT, 1.1bar max. Holds for slightly longer and tapers off more slowly.

I thus seem to have found a good compromise for my local climate and fuel. These 2 days, I did not get anything more than 1 flashing green on my KL (sensor mounted on manifold and set to max sensitivity). My fingers are still crossed though.

The car does not feel significantly slower. It actually feels a bit more responsive off-boost as I suspect less knock-correct is being run by the ECU.


Will report any significant further.

[Edited by RT - 7/16/2002 2:08:42 PM]