RB25DET max 'safe' boost for valve springs?

[Torques]

RB25DET max 'safe' boost for valve springs?

What would be the safe boost level before I get valve float?

(intake valve not reliably closing anymore)

Thanks

[Dale FZ1]

The answer is a bit rubbery, will depend a little on how big/small spec your turbine and exhaust system is.  The original springs aren't that heavy, and if they've seen a bit of work it's probably time to replace/upgrade. 

Setups will vary, and some will experience float earlier than others if the springs in that car are on the softer end of production tolerances or otherwise tired.

If I was looking to run up over 20psi, springs would be on the shopping list.

[Dose Pipe Sutututu]

Might be irrelevant but with stock cams and a Hypergear SS2 EWG I was able to squeeze about 25psi into the motor without any valve float on the stock springs. Motor lasted about 1 year of track abuse before it went bang lol.

[Dale FZ1]

^^ Highly relevant.  Consistent with observations about turbine spec etc.  I'm not suggesting 20psi is where it all goes downhill, but below that point we don't hear much talk about valve float.

 

 

[r32-25t]

It really is a how long is a piece of string questions, basically it all comes down to a lot of things including cams, how far you want to rev it, wear on the springs or even the old was it built on a Wednesday or is it a Friday afternoon special 

[Torques]

OK, thank you ...

I'm usually not revving the engine highly , it rarely sees 6500 rpm. The limiter is set to 7000 rpm.

The engine has 70k km on the odo, and poncams installed.

I'll take your advice and will run 20PSI for the time being, other than on a dyno how can you tell you get into valve float territory?

 

 

[Dale FZ1]

So you are getting float, or don't know and are just chasing info?

 

Probably a bit hard to contemplate playing with the tune without at least giving it a squirt on the rollers to validate what's going on.  You can achieve plenty with road tuning, but an hour of dyno time isn't that expensive and will tell you heaps.

[Dose Pipe Sutututu]

Often the car will lose power and fall flat on its face or you other times will misfire or worse case is valves kiss cylinders lol.

[Torques]

I was trying to get some information since got a new turbo capable of 24PSI@ 6500rpm which is a big step from the 15PSI of the old turbo.

While being on a roller I found that the power curve went through some strange 'ditches' and I was wondering if that might be due to valve float.

Valve float was not of any concern to me before simply because my old turbo was running less boost.

I'll dial in 20PSI and run more timing to get a good baseline, from there I can work it up should I feel the need.

 

 

 

 

[thebe]

Out of curiosity, how do you notice valve float on dyno? Stock springs here running 23psi

[GTSBoy]

Wiggly lines on the graph up the top end.

[Scott Black]

f**k it 40psi then you get an excuse to build a 3l

[Scott Black]

On a serious note however http://www.hypergearturbos.com/index.php?route=product/product&product_id=57
Scroll down. Click dyno results, scroll down and read special consideration for rb25 and it has some info on this for you

[thebe]

Good stuff. Sorry for hi-jacking the thread a bit but can you guys recommend valve springs? Heard supertech are good, are singles enough or should you get dual springs while at it? Retainers aswell or are springs enough?

 

In my case running rb30 (not forged) so revving only 6800 atm. Looking for ~500-550 hp, now at 440hp and 23psi (holset he351) with suspected leaking standard bov

 

 

[hypergear]

Valve float:

it gives this M shape dyno reading

 

I personally use Supertec valve spring kit:

http://www.digi-hardware.com/photos/head/springs.jpg