0.9 Bar WG spring measurements please

[Rusty]

As per title, anyone got the dims for a 0.9bar WG spring, I've calculated it roughly based on the stock WG but want to double check...

Or, does anyone know what spring rate is required? The link from Pembo's thread showed up at 9.72 N/mm.

[AndyP]

These are from my 034 0.9bar spring:-

Height : 64mm
Dia : 42mm
Coils : 4.75
Wire dia : 3.75mm

[Rusty]

The Lee Spring catalogue has that at 8N/mm so more than the 5 that I guessed at. Then again, there's much less pre-load on it as it's shorter.

http://www.leespring.com/uk_product_spec.asp?partnum=LHC148T03S&springType=C&subType=

I was looking at a pre-load of 230N to get 0.9 bar. Using a stock WG cap this spring would give a preload of approx 260N so I wasn't far off.

Has this spring been tested and doesw it definately give 0.9bar gauge?

[Rusty]

Done some measure ment s on the stock WG spring set to 0.4 (1.4) bar depending on your point of reference.

Outside Diameter 38.55mm
Free Length 80.5mm
Wire Diameter 2.8mm
Number of coils 4

This spring translates to equivalent springs with a spring rate of 3-3.5 N/mm.
The approximate pre-load is 46mm, thus 46 x 3.25 = 150N.
Some testing showed that between 8 and 10 turns of the cap screw gave 0.6bar.

The screw is M12 so I have assumed 1.25 pitch as this is stock size, I will check this.
Thus 9 turns gives an extra preload of 9 x 1.25 = 11.25mm.

To get 0.5 bar extra I have assume a linear relationship, thus

11 / 0.2 x 0.5 = 27.5mm extra preload
Added to the original, 46 + 27.5 = 73.5mm
73.5 x 3.25 = 240N preload for 0.9 WG opening.

I have compared these calcs to the 034 spring and calculated a pre-load of 260N based on my stock WG cap.

Now comes the interesting bit as I am not sure how to choose the spring rate.

The 034 spring has a rate of approx 8.5N/mm, 2.5 times that of the OE spring.

[AndyP]

Ignore the information in my last post, thats not a 0.9bar spring! I got it from 034, see here

http://www.034motorsport.com/product_info.php?products_id=199

I'm sure I checked first and they said the 1.9bar was absolute, so it should give 0.9bar boost. But I've been doing some testing this afternoon and it goes way higher than that, I only put my foot down once and it boosted to well over 1.4bar, my car is only mapped for 1bar so I backed off sharpish. Must say it was pulling really well though!
I checked my original spring and it's different to Andy's measurements from a stock spring, so I put that back in and checked it with and without the WGFV. Sure enough I got 1bar both times. So here are the dims for a 1bar spring

Length : 83mm
Dia : 39mm
Coils : 6
Wire dia : 2.8mm

This is the spring from 034 ( Left ) and the 1bar spring.

[A80Avant]

interestingly enough, on my wastegate with the screw totaly unsprung, i got 1bar with the 034 spring....

that is without the N75 connected

[Rusty]

Andy, those dims are the same as the OE 1.4 bar spring. The spring in the pic on the RHS is OE too, identical to the one I removed and measured yesterday, even down to the mottled copper finish. Your WG pre-load spring must have been tweaked.

You've confused me now...

[newsh]

Thats a pretty strong spring you've got there AndyP

Here's my spring, this can be adjusted to give around 1 Bar with the WGFV disconnected

Length 72mm
ID 32.7
Wire size 3.5mm
Turns = 5

Stock on the left, UR spring in the middle (3.2mm wire), 1 Bar on the right. The 1 Bar spring came from Mihnea.

My disclaimer is I used a plastic Vernier Guage

[Rusty]

LOL, so many differnt phooking springs! Will have to have a look tomorrow and see what I can find. Cheers for posting up John.

[AndyP]

Andy, those dims are the same as the OE 1.4 bar spring. The spring in the pic on the RHS is OE too, identical to the one I removed and measured yesterday, even down to the mottled copper finish. Your WG pre-load spring must have been tweaked.

You've confused me now...

Your spring only had 4 coils on it, mine has 6, could this make a difference? The wastegate cap still has the tamperproof bung in place on mine and there were no shims on the spring.

[Rusty]

If it's the spring pictured then it's the same, I didn't count the base and top coil so 4+2 = 6. Strange.

just looking into Newsh's spring now.

[Rusty]

Newsh's spring seems to have a rate of betweem 5.5 and 6N/mm, as it is 10mm shorter, the preload will be 36mm approx.

35x5.75 = 207N

I was thinking last night, P=F/A, P=manifold pressure, F = spring force, A = WG area = constant.

Thus P1/F1 = P2/F2

So F2 = P1 / P2 * F1

F2 = 1.9 \ 1.4 * 150

F2 = 203N

So form this is looks like Newsh's spring gives the correct opening force. This assumes a linear realtionship for all the parts in the system. Only way really is to suck it and see I guess.

Just checked my calcs from last night and it seems that I chose the same spring that best matches Newsh's.

Next step is to call the company and see if I can get a spring sent out to try.

[newsh]

Yeah the long spindly one is deff the stock S2 spring no question.

What I'm wondering is why Andy's car is making 1Bar with and without the WGFV

[Rusty]

Another thread perhaps

Is your spring in the car at the mo John? I'd like to try one before spending ££ on springs if at all possible...

[newsh]

Another thread perhaps

Is your spring in the car at the mo John? I'd like to try one before spending ££ on springs if at all possible...

It is yes, I took it out to measure it and then put it straight back in, I could run on the ur spring for a few days though if you want to give it a go.

Actually I quite fancy trying AndyP's extra stong spring, I reckon this would give 1.9 Bar of boost without the WGFV


Oh BTW I forgot to say, for those who enquired, I don't have a spare ur spring any more sorry.