shunty

John Stevenson - what is the whistling noise when I change up a gear? started after new downpipe fitted.
thanks

shunty

[This message has been edited by shunty (edited 15 September 2001).]

Sith

That'll be your turbo. Whistles merrily as boost builds. My re-circ dv gives a slight shhh weeee noise. Techy term that. You can also hear the waste gate fluttering as well. Mine seems to flutter all the time while on boost.

P.

shunty

cheers Sith, I'm obviously showing my technical car knowledge for what it is......
I thought it would be the turbo to be honest.
sounds the biz anyway

shunty

[This message has been edited by shunty (edited 16 September 2001).]

Marty.S

Hi John,
Had the downpipe fitted saturday on my 00ppp , car is pulling stronger now but occasionaly a bit hesitent, does this mean i need a 1.3 restrictor?

thanks
marty

john banks

Possibly. What revs/gear does it happen at - mine was in 4th at between 3200 and 3600. I still might get a boost gauge - I'm seeing how the cold weather goes, but it's OK on 1.3 at present. Marty - mine needed a 1.3mm with just PPP to always pull smoothly, and now hesitates stupidly with a 1.2mm restrictor. Might be a few boost gauges getting sold...

john banks

It was **COLD** this morning and damp. And the car was doing its overshoot the boost thing again, and was still noticeable all day. I have put the restrictor back in the proper place as described above, but only after drilling it out to 1.5mm but only down half its length. I could not source a 1.4mm drill. It works and the car pulls smoothly again with no loss of performance. I don't know if we'll gradually get bigger as winter comes, but if going up by 0.1mm helped when PPP was originally fitted, I am hoping the extra 0.1mm again will compensate for the more aggressive boost ramp of the downpipe. Must get a boost gauge or work out how to decode the MAP sensor signals as per my separate post in Drivetrain. Happy boosting!

John Stevenson

John, I've made myself a 'set' of restrictors. I can now adjust boost from 0.7 bar to 1.5 bar in roughly 0.2 steps. Took half an hour in the Garage and cost...erm a bag of brass Screws from B&Q, which I then cut the thread and the head off, leaving only a blank 'shank' to work with. Works a treat.

---john---

[This message has been edited by John Stevenson (edited 18 September 2001).]

john banks

How long do you make them? I would have thought that the length as well as the calibre is important - the flow should be proportional to the fourth power of the radius divided by the length of the restriction. Hence my reason my drilling out 1.5mm only half way - seems to do the trick. What size drill bits did you use and did you make it the same length as the OEM one? Which one are you using now? Is it only affecting peak not held boost?

john banks

john banks

Maplin have some handy small drill sets also, and some nice gauges for my little project. Will post details if it works.

John Stevenson

John, Mailed you.

---john---

matt b

John
when i bought my D/P from falkland the other day i mentioned your problem with overboost and asked if a boost controller would be advisable. the very helpful bloke who's name i cant remember said that he wouldn't call you problem overboost as such and instead recommended shaving a few thou off each spark-plug. im not in the slightest bit mechanically knowledgeable but he said if you were to take your spark-plugs out and give him a call he would be able to advise the clearance increase he would recommend.
does that make any sense at all?

Marty.S

A mate of mine has made me some restrictors,1.3 & 1.4mm dia.I am going to try them but wanted to be sure of the consequences before going ahead.
Any advise appreciated
thanks
Marty

john banks

No the spark plug thing doesn't make sense, because changing restrictors sorts the problem entirely. When I previously asked Falkland's advice about overboost they didn't really seem to know what I was talking about, had no idea about restrictor sizes, PPP boost cut off or overshoot, and said that the downpipe and induction kit would give no trouble with overboost. This is obviously complete nonsense in the case of the DP and I tried to tell them about the overboost I had been getting when PPP was fitted which required a larger restrictor 1.3mm in place of 1.2mm pre-PPP to stop too much overshoot on spool up. Its not enough to trigger fuel cut brick wall stuff, but it is an overshoot of boost which then undershoots before levelling out - ie an underdamped response. This is because the PPP and then the DP bits probably by reducing restriction in the exhaust allow faster spool up which is too quick for the standard system to cope with. You can feel it as initial enthusiastic spool up and then a disappointing undershoot and then a levelling out. The ideal is a response which is well damped where there may be a peak boost which is a little higher than held, but not so high that things go too far and there is then undershoot - an underdamped response - and a very disappointing driving experience and not very progressive. You can feel this and see it on the Select monitor which Nobles put on and we plotted boost curves for 1.2mm and 1.3mm restrictors. Now before my DP the PPP was fine on a 1.3mm restrictor - with about 60mmHg leeway in peak boost (ie peaking at 940mmHg) on a hot day in 4th gear which then stabilised at 860mmHg. This held boost was the same or slightly higher than had been the situation where the boost shot up and just touched 1000mmHg with a 1.2mm (original) restrictor, and then went down to 750mmHg before settling at about 860mmHg. Now that drives very craply indeed which is why I took the car back. When the DP went on it was hot weather, there was good smooth spool up and I think I was on the sweet spot. But as the Scottish mornings got colder and damper, the original problem returned - you can feel it - and it is really obvious on my car if I go back to the original 1.2mm restrictor - really really crap drive. Presently I have a restrictor half of whose length is 1.3mm and half of whose length is 1.5mm, and the spool up is very smooth even on cold mornings. I am sourcing some more precision drills and will try 1.35mm (which I am hoping will be the best compromise and drop peak boost by just enough to make the spool up smooth but still brisk. I may need to go to 1.4mm which is probably the equivalent of what I have now. I am also in the process of making up an electronic boost gauge, the results of which I will post if it works. The aim of this is to see the effect on peak and held boost of 1.3, 1.35 and 1.4mm restrictors. I think the sweet spot will be 1.35mm as only a 0.1mm change from others' experiences can result in anything from 0.1-0.4 bar change in peak boost. On 1.3mm the car does not feel right. It does at present, but I don't want to be running a bigger restrictor than I need to get good boost control as this dumbs down the spool up more than is necessary. Obvious disclaimers apply - this is a MY00 PPP and if you blow up your engine I am not responsible. But by gradually increasing the size of the restrictor I am reducing peak boost which can only be good for the engine and avoid possible lean spots from excessive boost spikes. If I was less fussy, I may not have noticed this poor boost control, but anyone would on the original restrictor on my car with DP - others cars are different. Nobles said that most folk with PPP do not get their restrictors changed at all. May be they are all running round with poor boost control and happy, maybe their cars are smooth. I know all the tubing is clean and the restrictors are not clogging, which can be another reason for poor boost control. But this side of an electronic boost control I would like a smooth, safe spool up which has some leeway for climate change, which is not the case with 1.2mm OEM or the 1.3mm dealer restrictor. I already got 3 or 4 runs with the Select monitor out of the dealer post-PPP (which took about 1.5 hours all in) but now I have got a DP fitted elsewhere I think it is my responsibility to sort it out, and I wouldn't trust the dealer or Falkland to do it for me, as I think the dealer would just bang in a bigger restrictor to save me coming back, and Falkland would start fiddling with my seemingly perfectly good spark plugs, which just does not seem to be the issue when a restrictor solves it.

matt b

fair enough- i thought their suggestion sounded a little bit too simple. what are the advantages to drilling out restrictors etc over a boost controller?
The problem with this site is to the unitiated it is difficult to pick up the basic principles in order to follow and understand the more advanced stuff.
i'm going to go off now(head hung in shame) and look for "restrictor" threads.
cheers

john banks

I'm only mumbling my way through this myself too. Some of the replies from Pat/Adam M/Bob Rawle/Sam Elassar et al (hope I've not forgotten any famous characters) are completely over my head, but I understand more each time.

The only reason for not going for a boost controller is £. Drilling restrictors is cheap - a drill set is less than £10 - an eagerly awaited delivery from Maplin when they have some in stock. I figure that this is one simple thing I can do to get my car running how I like it, and after all at the end of the day it is me that drives it and knows how it feels best. A Scooby is a tactile experience, and I don't care about RR bhp, but how it feels on the road, and I want a nice progressive but smooth turbo response.

Edited to say the only 1.35mm bit I've managed to find is a carbide one from

The Saint

John,

Your prose style could do with some punctuation !

Have you ever thought of using paragraphs ?

The Saint

john banks

See what you mean. What about the above?

Stelios

Fitted the Magnex d/p today on my PPP MY00 Euro lhd with K&N filter panel.
Comments
Fitment: Not quite straightforward as other aftermarket needed some forcing and heat shield needed cutting to re-fit.
Noise: Thank god for Dr Banks. No noticable increace in exhaust bass note at any speed! BUT now there is a turbo hiss all over the rev reange and blow off is now quite audible, suprisingly wastegate opening noise is down!
Performance: Turbine comes in smoother @ 500 rpm less. No PPP torque kick now just linear acceleration thru the revs. Big suprise no boost pressure increase as yet. Maybe it has to do with the fact that today is hot here. Car feels smoother accelerating, almost like it lost its edge, until one looks at the speedo and suddenly feels that a (yet another) brake upgrade is needed!

Overall : very pleased largest performance/money ratio, a must I think for noise concious PPP owners.

PS I owe the good doctor an ouzo!

john banks

That stuff puts me under the table - tried it when in your part of the world! Glad you like it - both the firewater and the DP.

john banks

Peak and held boost tonight are about 1.25bar based on a homegrown electronic boost gauge. The voltmeter is pretty quick, so I think I would see the peak if there was one.

This confirms my thoughts that the boost ramp is now a little overdamped - ie slow with no initial overshoot. That's how it feels too.

It starts to boost at 1700rpm and reaches 1.25bar at 2800rpm and holds until about 6500rpm before a drop off towards the red line. No matter what revs/gear I try to floor the throttle, the boost never overshoots then drops back again.

Obviously at 1.25bar I have not too much margin for an overenthusiastic initial peak - when hitting 1.33bar = 1000mmHg on the Select Monitor before that is when things got wobbly, but not if the peak stayed below. I will try a 1.35mm restrictor when I get the drill to see if I can get the sweet spot. Then I can always go back to the current restrictor if things get really cold and the boost control is lumpy again through the winter.

matt b

John
it sounds as if youve finally sorted things to your liking. Now that you've got the overboost sorted are you still reporting the same rave review of the d/p and its performance hike?
Ive got my 99 ppp booked in 2/10/01 at a main dealer. Will i have a 1.2mm restrictor fitted at present and if so should i get them to replace that with a 1.3mm? Any other things you recommend i ask them to look at diagnostics or otherwise?
cheers

john banks

I still rave about the DP. I am just putting the final touches to boost control. The overtaking performance on a road I know well today was absolutely sensational - even with the wife on board.

I would recommend you get the dealer to put the car on the Select monitor after your PPP is installed and floor in in 4th from 2500rpm. This always showed up boost irregularities on my car. You want a brisk spool up with a peak below 1000mmHg, and then want it to smoothly hold something over 800mmHg if my car is anything to go by with just PPP. Change to a 1.3mm restrictor only if necessary to achieve this. This is an official Subaru fix according to my dealer.

I now have a mechanical boost gauge and today it was peaking at between 16 and 17psi and holding 16psi - and often could not see a peak at all which confirmed the electronic results, although with slightly lower boost - but probably within the error of these things.

With the OEM 1.2mm restrictor in the boost shoots up to around 20psi and then oscillates between 14 and 20psi all the time you are on boost thereafter at roughly 1/2 to one second intervals - like riding a kangaroo I suppose! But boy, does it feel fast when it spools up. Obviously for safety I'm not leaving it like this.

I think I've dumbed it down a BIT too much with the current 1.4/1.5mm half/half restrictor but at least it is smooth. I might try and source a valve which just adjusts restriction without a bleed port - ie. one input, one output, and a small screw which is very low geared to allow fine adjustment. This would allow easy compensation for summer/winter, and if always running a boost gauge will allow things to stay tip-top. I would plan to start fully open also using say a 1.5mm restrictor and gradually add restriction - or could of course use a bleed valve to do the same. The difference between this setup and the typical use of a bleed valve would be that even when adjusted I will be using less effective restriction in the pipe than the 1.2mm OEM restrictor - hence lower peak boost and less likelihood of underdamped boost control. Restictors seem a tad imprecise for this task. Some folk have reported 0.4 bar difference in peak boost from a 0.1mm increment in restrictor calibre. Anyone know off hand where to get the sort of valve I am looking for? In the meantime I'll hunt for one. It might be that if I find a simple restrictor valve I can use it in place of the brass restrictor.

If I use a bleed valve, I think I will need to keep the restrictor in otherwise I might get suction into the manifold through the bleed valve or loss of boost with the huge amounts being bled off as the bleed valve would be almost fully open to atmosphere to replicate the action of a brass restrictor.

Hope I'm making sense - any thoughts let me know. If they are "John don't be such a sad **** and get out more" then fair enough.

[This message has been edited by john banks (edited 23 September 2001).]

john banks

Taking John's cue I hacked about a brass screw. After a considerable degree of faffing, I now have about 17.5psi peak and 16.5psi held completely smoothly on a cool damp evening - tonight.

It only takes 18.5psi peak for 2 seconds to start getting very rubbish boost control.

If the restriction is too little, both the peak and the held are between 10 and 16 psi.

If the restriction is too much, the thing goes mad and peaks to over 18.5, drops to 14.5 then settles at 16ish with fluctuations - you can hear them also in the exhaust note! At the moment I'm on the sweet spot.

It seems John's MY98 PPP ECU will tolerate much higher peaks - ie up to 1.5bar - which is 22PSI. Mind you, I think this is a Phase I engine with a bigger turbo, and obviously a completely different ECU.

Looking on the dyno site, 17 peak and 16 held seem to be about the most noted on a MY99/00 PPP.

Filing the end of the restrictor actually makes the hole quite a bit smaller, which can be quite handy, but obviously it's trial and error. In the end the restrictor I am using was boosting to 18.5psi and now is 1psi lower and behaves much more smoothly after just barely a quick scrape from a drill bit in my hand - literally half a turn of the drill bit to enlarge the hole very slightly.

John you must be lucky having a car that will tolerate so much more peak boost than the held figure - must make adjusting it much easier.

Still not found a suitable valve for the job.