Mythbuster: continuing project thread of my 1303 '75

[Wally]

Originally Posted by Steve Arndt

Do you have a spring scale? I am interested in your old and new spring data. (install height, poundage)

No, not a professional one. I use a digital scale and measure in the exact same way as much as possible with the different springs I've used new and after usage. I usually measure at installed height (type 4) and 10mm compression after installed height.
As its my own method, it doesn't have reference to published data with anyone else. That doesn't bother me, as its for my own personal use only. I am not a shop, nor do I sell anything commercially, hence my testing is just for my own interest

A real spring scale would be nice though, just hard to justify the investment with so little use...

[Steve Arndt]

Can you give a qualitative comparison of the old and new springs? Are they much stiffer?

Do you have your installed height number handy? I am curious and would like to compare it to my heads.

Steve

[Wally]

Originally Posted by Steve Arndt

Can you give a qualitative comparison of the old and new springs? Are they much stiffer?

Do you have your installed height number handy? I am curious and would like to compare it to my heads.

Steve

Sure, you asked for it though :
actually I also had a set of the old CB regular HD springs and they were about the same pressure at 10mm compression! (actually a tiny bit less, but that may have been accuracy or a batch or..):
10mm compression: 120kg from the CB650 outer spring
10mm compression: 130kg from the old (cheap) CB HD single(=outer) spring.
This made little sense, so I put the inner spring in also and got these results:

I use an installed type4 height of about 1,50-1,52" or ~38-38.6mm, which is a bit less even then T1 IIRC.

At installed T4 height I got 88kg ('seat pressure') with the dual CB650 springs.
10mm compress.: 177kg (which was not that much more comparively)
As I thought they might only start shining with higher lift cams, I got past my own '10mm reference' and measured also at larger compressions:
12mm compress.: 217kg (!)
15,2mm compr.: 228kg
which were somewhat the pressures CB advertises with, so I was happy after all

So the 'over the nose' pressure is fine with cams of about 0.500" lift which most of us use.
So much for my 10mm reference

Oh, BTW, the Gene Berg double springs that came off the engine after 2,5 season had a pressure of:
Installed height (T4): 61 kg
10mm compress. : 115kg (!!)

Now, I hadn't measured the GB's when new, but they are probably in the same range new as the CB's or Scat's. That means a HUGE reduction in spring pressure after my relative short milage and relatively mild cam (just 0.500" lift). This is about 35-40% loss after 2,5 season!!!

My Scat springs I had a few years ago measured 95-100 kg installed height and 145-150kg at 10mm compression when new, so they were even less then the CB's when new and showed 25% loss of pressure after 1 season !!

This led me to my conclusion: valve springs are wear items and most all are near junk to begin with!... Actually to be renewed after every season is the only thing to do. But what could you expect from 30-35 dollar spring sets...
I hope these CB650 (which are about 3 times as costly as the other springs mentioned, but still not really 'expensive') hold their pressure better.
Only one way to find out I guess...

[Bad bug]

Originally Posted by Wally

Interesting will also be how the heavier CB 650 valvesprings will go along with my stock 'non-straight-cut' cam gear and stock single thrust cam bearing...

Well i hope these springs don't cause you any grief. Wally about your shroud, is there any possibility of getting anymore.

[Humble]

That's an interesting exercise and not something I'd considered. I'd be interested in seeing how the K-motion LS1 springs I've got hold up after a season of abuse. Thanks for the heads up!

[70Turbobug]

Indeed interesting info! I wouldn´t have thought that the loss in pressure would be so dramatic! One possible explanation would be that the advertised spring pressure exceeds the the tensile modulus (http://en.wikipedia.org/wiki/E-modulus) of the material used.To put it simple the spring pressure is calculated in such that the steel returns to its original strength after "stretching" without loss of tension.This value is the same no matter what steel is used,whether its a cheap steel or a high tensile alloy just as the expansion rate is the same if they are of the same diameter.The diameter of the steel is the key and base for calculation - not the alloy!! If the force applied exceeds that value (calculated in mm²),the material will wear quickly.Hence,the advertised spring value is higher than what actually should have been calculated.

[Bad bug]

Have any of you thought about using oteva 75 springs from Sweden. I don't know about the price but from what i hear they are good.

[Wally]

Originally Posted by Bad bug

Have any of you thought about using oteva 75 springs from Sweden. I don't know about the price but from what i hear they are good.

Yes, I looked and i believe they are probably very good also and could be much set-up like the CB's, however they are also 3,5 times the cost of the CB's (which makes them 10 times as expensive as a 'normal' spring set...).
I'll try these first

Got the 3,5" bore Borla XR1 silencer in today!

[Wally]

All parts in da house and making it all fit went well (I'am getting almost a routine in this ):



Went for a first test drive today
Needed to set-up the EBC again and by accident selected the wrong button...which led the boost rise to 30 psi before I backed off...
Fortunately all corrections and setting were entered up to 2 bar boost and the engine suffered no harm apparently. I did get launched pretty well though
Spool-up is indeed a lot slower as expected: I measured about +800rpm in the log before 15 psi was reached. I also must confess I checked the headers I welded and saw about 4 or 5 small leaks... so maybe spool will improve some when I have solved the leaks. Initial boost threshold seems a lot less slow and impressions are only about +500rpm for boost threshold.
I would have expected about +1000 rpm considering the size of the new turbo and all the extra volume in piping, so I am actually still vary happy already with spool as it is

Outside temp today was very cold: around freezing point: 0 Celcius. Intake air temperature was only 4 Celcius under boost. Air-air intercooler FTW

The most important benefit I saw from this turbo is that EGT was much lower throughout the whole rpm range, even when cruising! I had a lot to keep an eye on today, but if I had to make a guesstimate, 50 Celcius lower at least, maybe even 70-80 Celcius, but will have to investigate that when I have driven more.

I also have anothe HKS (SSQV) BOV installed and that seems to work well too. Seems to keep the flow more constant after it opens, but hard to tell exactly what/how it works different. We'll see.

Made a little vid in the hope to capture the Borg whistle, but I don't think I can hear it destinctly enough from the inside.

http://www.youtube.com/watch?v=f4iuImkFo0I

[Humble]

I love my borla xr1 it really toned down the exhaust quite a bit. How much rpm are you spinning by the time you hit 1 bar boost now? I know it added a bit more lag but is it tolerable?

I went with hks ssqv bov because a friend was using it in his car. I've found that I can keep about 10psi in the intake between shifts which really helps to kill turbo lag when rowing through the gears. I don't like the whistle though, and just put the recirculation fitting on it instead.

[Wally]

Originally Posted by Humble

I love my borla xr1 it really toned down the exhaust quite a bit. How much rpm are you spinning by the time you hit 1 bar boost now? I know it added a bit more lag but is it tolerable?

Surprisingly, it is very drivable still even lag is a lot more, but I still have about 5 leaks to fix with welding header connections...
1 bar was at ~ 3600 rpm in 4th, now its ~4400. Hope fixing the header boostleaks will help a bit to bring that down some.

[Wally]

Fixed some header leaks, so I now get 1 bar at 4250 rpm

Also got all springs back in the Tial so it opens at 1 bar when not controlled. Also retuned the maps a bit and went for a test drive again. Man, what a rush! At 1,2 bar I got actually a little scared and didn't proceed with the other higher boost settings I had planned today...

Picture from the new exhaust openings

[Bad bug]

Good job wally, i guess we can say that twin scroll turbos work, but just a little question here how did you group the exhaust pipes is it 1 and 3 4 and 2.

[Wally]

Yes, pairing 1/3 and 2/4 together is very important and ideally they should be equal length as well as this will give equal spaced exhaust pulses which helps spool. in TS configuraion.

[Sandeep]

Looks awesome Walter !

Might be the picture, but looks like paint on the apron is discoloring a bit, might be touching the header in this area ?

Fantastic build overall.

Sandeep