allmotor_2000

The original WG springs that BlueCLS6 and myself ordered were 7.25psi units. We figured due to inherent system 'losses', we were seeing anywhere from 5.7psi to 6.2psi - sometimes peaking to 6.5psi. So, we decided to order 8.7psi springs which would leave us with around 7.5 to 7.7psi. Anyways, we removed our original springs and they turned out to be 5.8psi springs!!! It appears that either the WG has boost creep (extremeley unlikeley considering out boost levels) or our boost guages (full-sweep, self-calibrating electrical units) can be about 0.3 - 0.4psi off on their reading. It is quite possible that even though the WG is rated to 5.8psi, we can see 6.2'ish psi - it is a metal spring after all and not sure if its necessary that precise. It is likeley that the WG spring is allowing about 6psi and the guage might be 0.2psi off; a believable scenario.

Anyways, so we are either going to go for the 8.7psi spring, in which case we might even see 9psi of boost!! OR, we can go for the original 7.25psi springs where we could see a max of about 7.5psi.

I need to get a third-party boost guage to get a check on what the boost really is I think there is a LOT of power to be gained with a moderate boost increase!!

mattg

you definately need more power.

JaredGMS

BlueCLS6

I currently have a 3.63, 5.80, & 8.70psi spring sitting on my desk... hmmmm which shall I install I need to order some 7.25psi ones. I was thinking; we are stuffing 3.2L of air at 7,ooo rpm through a 38mm wastegate so boost creep has definitely crossed my mind. Actually it's the design of the WG cross over that comes to mind. The hole in mine isn't exactly ideal. That's the only explanation I have for more than the rated 5.8psi of the spring. I don't think the WG is undersized, but the passage leading up to it... at least on mine. Yours looked a little more restrictive in design, thus the slightly more boost (besides the open exhaust)? I bet the boost gauge is pretty accurate. At higher boost I bet it will more closely match the spring rated value. Soooo I'll get us some 7.25psi springs...

allmotor_2000

I don't think its the angle of the wastegate inlet... under pressure exhaust gas will go where it needs to. The diameter might be an issue, although it is pretty much matched to the 38mm inlet (probably a tad smaller). Even cars that boost 30psi don't have anything much bigger than a 46mm wastage, so I doubt that's the problem.

I do see 0.25psi or more with the exhaust open... but don't understand how it can be more than the rated spring value.

allmotor_2000

Given the circumstances I am not entirely comfortable going with the 8.7psi spring... understandable reasons!! By the way, can you also get one of those bolts for the wastegate... I lost one Had to steal one from the BOV... figured the BOV can do with one less bolt!!

Louie11

Can't wait to see the results of the new spring.

scalbert

It is my understanding that the WG spring rating is dependant on the differential on both sides of the WG. There is still back pressure on the outlet of the WG due to the catalytic converter and the rest of the exhaust. This could cause a slight error in the actual opening.

Had the WG dumped to atmosphere the rating and actual values may have been closer.

Also, as pointed out, there is quite a bit more when you consider ancillary components. The WG system may not flow.

scalbert

^^^^^

scalbert

Ah, come on and go for it.

Actually, I would start with the 7.25 PSI spring and if everything holds true, that may give near 8 PSI. About all that you will want to run on the street.

allmotor_2000

Actually the only pressure preventing the spring from compressing is if you feed boost via the top of the wastegate - that's how a boost controller does its job. Exhaust pressure at the WG discharge end has negligible or minimal effect on the spring - it could impede flow, but does not prevent the spring from being compressed.

scalbert

This is a piston style WG?

I was under the impression that the delta across the valve can cause a resistance of the valve to move.

scalbert

The line of thinking is that if the pressure differential is increased, depending on which side is higher will either increase or decrease the boost levels.

For instance, if the valve opens towards the flow and the pressure differential is increased, such as the cut-out opening, the creates a greater resistance for the valve to open against and potentially raising the boost.

Just a thought though as it appears the amounts are not too significant.

allmotor_2000

It is like a pneumatic piston I suppose but spring-loaded, so its natural tendancy is to keep itself shut. The flow of exhaust is in an 'L' shape, it comes in from the bottom and leaves through the side. There is a pressure-input port on the bottom of the chamber (help compress the piston under boost) and there is a pressure-input port on the top of the chamber (help prevent the spring from compressing under boost as well - boost controller uses this). Exhaust pressure can tend to exceed intake pressure, so I can see how exhaust flow can get impeded; under boost exhaust is not trying to get 'into' the WG from the discharge side. I should try to find a cross-section drawing online somewhere... maybe in Maximum Boost.

BlueCLS6

http://www.tialsport.com/gates.html

the Instructions link has a good cutaway...

darrinb

more is better!!!

ghost_masterCL

holy mother of god! You're making 419 WHP at less than 6 psi?!?! WHy are'nt teh SC guys making that? I'd stick with the 7.25 psi spring and just tak teh 500 whp you'll make off of that.

scalbert

Easy, greater compressor efficiency and most importantly, much less parasitic loss. A turbo system does not have the 10% power loss by way of turning the blower/compressor.

evilone

what gauges are u usen autometer??? are u usen a mech gauge or digital?? i have 2 blitz blm series gauges that retail for 350 each but i dont have a boost one otherwise i would ship it out to you to see if that might help to solve ur prob. (the blm series is the carbon fiber face with black light display)

BlueCLS6

Yeah we use an Autometer self-calibrating full-sweep digital boost gauge, see avatar...

evilone

well blue u work for garret right well u should have plent of turbo cars at work right??? if so see if one of ur work homies could do with out a gauge for a couple of hours. i would try a dif brand other than autometer just to see if it has anything to do with there product... good luck and keep us updated

allmotor_2000

It is highly possible to get more boost than the rated WG spring due to many factors... 0.5psi is entirely believable - just need to know that's how this system works. I can swear I see nearly 6.5psi at times... dunno!

allmotor_2000

... and its not going to hit 500whp - need cams and some headwork to get that kind of power @ < 8psi.

ThinJim

iTrader: (3)

you'll need more than cams, say goodbye to yer stock rods and pistons