Why boost is falling on stockers... [Archive]

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valmes

09-04-2006, 07:22 PM

It got colder once again and at -15C I can as well put out some theories :) ...

Have you noticed that when upping boost with your EBC/MBC you can't get it to hold up to redline?

It is generally believed that our turbos are "running out of puff" (is that the term?), but I think you can hold more to redline...

The problem is that our actuators come with springs preset at either 0,5 or 0,6 bar... Even before the set level they start cracking open, but turbos can pump so much air that this is not noticeable on stock boost levels.

When you up the boost with your BC - all it does is delaying the control pressure applied to actuator diaphragm/spring and making wastegates open later... allowing for higher boost.

Now, there is also such thing as exhaust pressure and it can get nasty... it can basically crack open your wastegates without any air pressure applied to actuators! It is getting worse with a high amount of backpressure...

Ok. Solutions. First - good exhaust and DOWNPIPES (Kakimoto has downpipes for 6a13TT) will allow for less backpressure, hence - more boost held to redline on stock actuators... Second - by changing stock actuators springs to some stiffer ones or changing your stock actuators to some aftermarket units you can trash the hell out of your turbos! :)

I seriously think that upgraded actuators (and probably some exhaust side clipping) were the only upgrades done to PROS Eng./Bozz turbos for EC5W/EC5A ...

Forge actuator upgrades (http://www.splparts.com/Parts/Z32/Turbo/Kit/default.asp) btw can be found for less... I've seen 190$ price tag somewhere.

Hope that info is of some use to clubvr4 members/readers :book:

Kieran

09-04-2006, 07:29 PM

I concur with what you've said Valmes. I have noticed since refitting the cat convertor and during the colder weather, boost bleeds more easily. Currently I can only hold 0.47bar at WOT in high gears.

Looked several times at the Kakimoto downpipe, I could get it from TakaKaira. It's relatively cheap too. The only thing putting me off is the diagram on the Kakimoto website:

http://www.kakimotoracing.co.jp/image_MF303.html

More specifically, It doesn't look like an "Equal Length" downpipe - surely that would unbalance the pressure waves and leave it a bit 'gruff' - a bit like Stock Imprezas are?

valmes

09-04-2006, 08:21 PM

There are only two options for EC5A/EC5W:

PROS Eng. equal length downpipe... with a ¥98000 :) price tag and Kakimoto downpipe at ¥35000 (US$323 Takakaira price) ...

From the price point of view, we can't really complain... :) and IMHO they wouldn't sell crap for so long ;)

You can always try to do them locally.

bradc

10-04-2006, 12:10 AM

I had mine done by Pitstop in NZ and while they aren't equal length they freed up about 11kw ATW compared to the stock exhaust setup.

In regards to the actuator, would it be possible to crack a stock one open and change the spring?

valmes

10-04-2006, 01:52 AM

In regards to the actuator, would it be possible to crack a stock one open and change the spring?

http://photo.platonoff.com/Auto/20051003.Saab_NG900_Wastegate_Actuator_Spring/

It might be possible... but (disclaimer) I didn't say they will still be in working condition after you try to open them up... ;) :afro:
I have my old turbos+actuators laying around somewhere… I might have to take a look at them. :inquisiti

bradc

10-04-2006, 02:33 AM

nice link thanks

valmes

10-04-2006, 03:03 AM

Hell... I've never seen this thread before (link below) :)
So I am kinda late...
Michaeli :2thumbsup

http://www.clubvr4.com/forum/showthread.php?t=13368&highlight=external+wastegate

Also some good post by AllBeItMine in that thread... any updates on your upgrade progress?

My poin is PROS/Bozz speed claimed something around 400BHP on their cars with PROS turbos (made out of stockers)... Even if Springs/Downpipe/Exhaust allows to go up to 350HP that would be a worthy (and not too expensive of an) upgrade...

Right now, I am aiming at 22-24 PSI max (May be more later) and 12-14 PSI base spring pressure, so will eventually have to upgrade my 8 psi WRX actuators too.

Kieran

10-04-2006, 08:46 AM

Second - by changing stock actuators springs to some stiffer ones or changing your stock actuators to some aftermarket units you can trash the hell out of your turbos! :)

How so, Valmes? I presume you mean you can trash the turbos if you fitted too stiff a spring?

Kieran

10-04-2006, 08:49 AM

And, would something like this be suitable, with a 9-15psi spring in it?

http://www.forgemotorsport.co.uk/content.asp?inc=product&cat=0001&product=FMAC049

mpau009

10-04-2006, 09:06 AM

Interesting thread.:2thumbsup

I was wondering if there would be any advantage in running a larger diameter replacement line from the actuators to the boost controller solenoid? obviously it wouldn't be as good as new wastegates, but do you think a bigger return would help sustain boost? Might be worth a go if i can get some spare hardline from work.

Nick Mann

10-04-2006, 09:44 AM

How so, Valmes? I presume you mean you can trash the turbos if you fitted too stiff a spring?

I am guessing, but I would imgine that it is simply a case of the harder you work the turbos, the less time they will last. Having them working under higher pressure will increase wear and decreas life. I don't think it is linear either - so 10% increase in pressure is more than 10% reduction in life.

Valmes? Is that what you are hinting at?

valmes

10-04-2006, 10:31 AM

2 Nick Mann & Kieran:

I guess my English is getting worse...
I meant - you can squeeze every available HP/CFM out of your turbos with upgraded actuator springs/downpipes combo. That will probably allow to hold more than 8 psi of boost to red line.

Sorry, I guess I just used a Russian expression in English... :thinking:

However you are right, more power from stock stuff - usually comes to less reliability...

Forge Motorsport actuators would be an option... or take a look at the link above (For Saab) - I think its not that hard to replace the spring s in our stock actuators. I will take one apart today... will see ;).

2 mpau009
"larger diameter replacement line from the actuators to the boost controller solenoid" - just think of it as increasing lag in your control line (is that what you mean?) I doubt you will notice any changes, aside from more boost spikes... :)

Nick Mann

10-04-2006, 01:44 PM

I understood the theory fine, Valmes. I think the confusion came from 'trash the hell out of the turbos' which to me means hit them hard until they break!

What does it mean in Russian?

caishanvr4

10-04-2006, 02:12 PM

So is the kakimoto downpipe a good investment? is it easy to fit and do you think funky styling can get it. Anyone fancy doing a group buy :-)

valmes

10-04-2006, 03:08 PM

I understood the theory fine, Valmes. I think the confusion came from 'trash the hell out of the turbos' which to me means hit them hard until they break!

What does it mean in Russian?

Same thing here - "Push them to their limits... until they break!" :5shots:

Ehhh... :inquisiti are we now playing some "confuse this Russian guy" game? /Grrr

J/k :)

PS: Another game I see all the time is called a "group buy"... what are the rules? ;) Sorry, I just can't stop once I started... I will go break that stock actuator to pieces and report back with results :)

valmes

10-04-2006, 03:45 PM

I just realized that Ive got no tools for the job... /pan will do that tomorrow.

EdmundVR4

10-04-2006, 06:36 PM

Valmes, what about the wastegate mod ? Would that not achieve the same thing, instead of buying new wastegates ?
My mechanic has installed 3 metal washers on on each wastegate spring & now my stock boost pressure is 10 psi...used to be 7 psi before this mod. However, boost still drops off & the most I hold to redline is 11-12psi in the higher gears.

Axeboy

10-04-2006, 07:03 PM

So is the kakimoto downpipe a good investment? is it easy to fit and do you think funky styling can get it. Anyone fancy doing a group buy :-)

You can just order from takakaira direct... good online system.

bernmc

10-04-2006, 10:58 PM

buy it here (http://www.takakaira.com/asp/template.asp?cat=2&id=595&prodID=OPpLmMmhjIkgnJi)

35K yen is around £170. Don't know if anyone's bought from these boys before... not sure what post will cost, then add 10% + 17% for Gordon Brown...

emailed them to ask about delivery costs.

caishanvr4

11-04-2006, 12:34 AM

Kenneth

11-04-2006, 01:05 AM

You lot aught to get pipes like these::pimp2:

bernmc

11-04-2006, 08:03 AM

You lot aught to get pipes like these::pimp2:

/JawDroppi

valmes

11-04-2006, 10:55 AM

You lot aught to get pipes like these::pimp2:

Are you saying it's "custom made"?

Resembles the one from PROS Eng. (around ~ 100 000 yen in Japan):

http://www.venus.dti.ne.jp/~debizoh/car/fpipe.jpg

You See

11-04-2006, 11:16 AM

oh I want oneeeeee!!!!! ..damn you Kenneth! /Grrr

Kenneth

11-04-2006, 08:59 PM

Are you saying it's "custom made"?

Resembles the one from PROS Eng. (around ~ 100 000 yen in Japan):

No, my step-father reckons its done by machine. I picked those front pipes up off a guy in NZ (marmel) who was breaking his legnum 3 or so weeks ago. Got his almost full 3" stainless exaust system actually, still using a 2.5" decat pipe though :P

valmes

13-04-2006, 04:00 PM

http://i9.photobucket.com/albums/a82/valmes/actuator.jpg

That's stock VR-4 actuator... the spring thing COULD be changed to something stronger... Although I will be performing this mod on my TD04L-13T turbos... :afro:

Nick Mann

13-04-2006, 04:43 PM

So in your opinion, would there be any side effects? For example, if the spring is stronger, will the boost controller still be able to accurately control the boost?

valmes

13-04-2006, 05:46 PM

Depends what kind of boost you are aiming for... as was previously stated boost controllers are ok at controlling boost through internal wastegates, at base spring pressure (lets say it is 7,5 psi) + 10-12 psi on top of that... Moreover, whoever came up with that theory didn't know how tiny our turbos are (stock), so on top of spring pressure we will probably have like 6-8 psi before our wastegates are pushed open by exhaust pressure... that's imho.

Well, for me with WRX actuators set at about 8 psi plus 12 psi on top of that = 20 psi - not enough... will have to get 10-12-14 psi spring in there... :))

michaeli

17-04-2006, 08:30 PM