Jump to content
SAU Community

Recommended Posts

Hi ppls,

I've had my valve springs replaced and was told with the standard RB25 N/A valve springs I had seat pressure of 10pounds across the board.

After the valve springs were replaced this jumped to 35-40pouinds (was vague).

Would any one know what the factory seat pressure is supposed to be for the RB20DET, RB25DET or even Rb26DETT?

He was quite happy with the seat pressure its now at.

What do you all think? Whats considered 'good' or 'over the top' seat pressure for an RB DOHC head?

Thanks ppls. :thumbsup:

Link to comment
https://www.sau.com.au/forums/topic/175738-valve-seat-pressure-for-rb202526/
Share on other sites

I'd say it was 10 pound. It was valve floating with anything more than 4500rpmish and 10pounds of boost.

Hrmm so now its 35pound and possibly still not enough. :S

He was a little vague when I spoke to him though. He said its much better 35 to 40 pounds. Not psi like I repeated. :P

Any idea what RB25DET's std or Rb26DET std run?

I'd say it was 10 pound. It was valve floating with anything more than 4500rpmish and 10pounds of boost.

Hrmm so now its 35pound and possibly still not enough. :S

He was a little vague when I spoke to him though. He said its much better 35 to 40 pounds. Not psi like I repeated. :P

Any idea what RB25DET's std or Rb26DET std run?

It could be, but the head shop(the one sydneykid uses) siad 35lb wasn't enough, at 10lb, boost pressure would be holding the valve open(assuming the valve it 1sq inch), nothing to close it, but im no expert, sounds like we have a mix up in measurements. The head shop also said that hydrauloic lifters need more spring pressure as they have to move the weight of the lifter.

In the manual the GTR springs are supposed to see 24kg (52.9pounds) at installation load which is the spring length compressed to 35mm. Not sure if installation load represents seat pressure? :S

Ahh well as the saying goes. The poor/tight man pays twice. lol

I dropped a set of GTR springs in my RB25 head; the gtr springs are slightly taller than the gtst springs so they should provide more seat pressure than when sitting in a GTR head.

Hopefully all is good, if not I'll be paying twice. lol

Should have simply dropped a set of performance springs in they only cost $280 odd.

In the manual the GTR springs are supposed to see 24kg (52.9pounds) at installation load which is the spring length compressed to 35mm. Not sure if installation load represents seat pressure? :S

Ahh well as the saying goes. The poor/tight man pays twice. lol

I dropped a set of GTR springs in my RB25 head; the gtr springs are slightly taller than the gtst springs so they should provide more seat pressure than when sitting in a GTR head.

Hopefully all is good, if not I'll be paying twice. lol

Should have simply dropped a set of performance springs in they only cost $280 odd.

Yep, installation load is seat pressure, i would just make sure that its not going to coil bind at full lift.

I had them check that; no bind.

Quite a few others have ran with GTR springs and they haven't had issues so I was fairly certian I wouldn't either.

Sky30 ran tomei 260 9mm cams without bind.

This is bugging me... It can't have 35-40lbs of seat pressure if anything it must have equal to or slightly greater than what a gtr runs.

That being ~52lbs.

I'll give them a buzz tomorrow and ask how they check the seat pressure and quiz as to why it may be lowish. They feel that 35 to 40pounds what ever that means is perfectly fine for DOHC turbo.

Makes me wonder if they check valve seat pressure while installed (if thats possible) or if they simply measure valve spring pressure at possibly suspected installation load.

Gave them a buzz.

What they did was measure from the seat to the top of the shim??? and then throw the spring on the spring compressor and check the load required to compress the spring to that value. So sounds all a little dodgy but ahh well you get that. :S

He said GTR's generally get a little less than 35lbs. So I suspect they are not using the 35mm compressed value but rather a slightly higher value which is why they are getting a lesser lbs value. So using the same measurement.. 10pounds with the std springs and 35pounds after.

If all that makes sense. :rant:

Ahh well bugger it; see how it goes.

Thanks Adriano. :rant:

  • 1 month later...

joys!

I have been looking into this a bit as i gather the bits for my 25/30 combination.

I am using a series 1 R33 RB25DE head. I have just pulled out 1 intake and 1 exhaust valve to find they have different length and thickness springs.

both are VERY stiff but i will have to have them measured for seat pressure the measurement I have for base of seat to top of retainer is 37.5mm and the retainer is a few mm thick so i will have them compressed to say 34mm and see what the pressure is.

Are GTR springs different lengths? its a budget build I am doing and don't really want to run much over 1bar ever so the factory items might do the job. I will post my findings once i get them over to someone with a guage

Ahh I was under the impression you went with the R32 RB25DE head. :D

Yes the R33's run 2 different length springs; they are a tad more than the r32 springs from Performance springs in QLD.

The factory springs may very well do the job with the r33's. The problem witht he R32's is that the springs they use in the R32 Rb25DE head are the same as they are in the RB20DET head. While they are fine controlling a smaller valve with the rb20; once you shove more weight behind from the rb25's head them they struggle. :S

Let us know the seat pressure just for my own curiosity. If need be shim them up a touch to get around 50-55 pounds.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • Please use a modern ECU. PowerFC with the Nintendo Gameboy controller is horrible. It's not 2005 anymore.
    • The car/ECU will have all the sensor that it needs and expect to have. I think i do not have to explain to you how the Link is way better specialy if you have swapped engine   I just do not want to deal with any "problems" cuz i have only Nistune which i learned is not that great and in my case cant even deal with that speed problem (Link can) And of course it will be way more easier to tune and diagnose and safe. And for the ECU/speed problem...i dont know.
    • Per Mark Roberts of Sonictune: Mark Robert Author At this time, no. No ETA either 2016-17 models. You will be able to purchase and install a 2018.5+ TCU though   TCU purchasing and pricing info! As we near the release of TCU tuning, I am going to answer some questions I get asked often.   What do I need for TCU tuning? At this time, you will need a 2018.5+ TCU to be able to tune. If you have a 2016-to early 2018, you will need to replace your TCU with the newer version. One good way to know if your TCU is good is if you have auto upshift in manual mode in 1st gear around 6500 rpms. If your manual 1st gear goes to 7k rpm and will hit the rev limiter unless you shift, you have the older TCU.   Why do I need to buy another ecu license/phone flash if I already have it on my ECU tune? The TCU is its own computer module. It is completely separate from the ECU. Because of this, you will be required to purchase a TCU license and, if your tuner has it, the phone flash license required to tune it via phone/bluetooth.   Do I need TCU tuning? TCU tuning is NOT required. However, the faster your setup, the more it will assist in track and dragy time consistency.   If I’m ECU tuned by (tuner A) can I get my TCU tuned by (Tuner ? Yes, since it’s a different module and a completely separate flash, you can have two different tuners. However, it is highly recommend that you have both tuned by the same tuner. For me, my TCU tuning will directly complement my ECU tuning style and features and running my ECU and another TCU or vice versa MIGHT cause some issues. At this time and for the foreseeable future, I will only be tuning my current ECU tuned customers TCUs.     I have a SYVECS AWD controller. Do I still need it? Yes! The AWD controllers main job is to control your AWD system. However, with TCU tuning, you will no longer need the auto-shift function as that will be done through the TCU. The AWD controller will still be very beneficial for racers looking to maximize traction on the launch.     Shift schedule changes: holding gears longer at lower pedal input as well as max shift rpm changes. Please note, the new ECU race rom coming out will address 90% of the shitty drivability issues these cars have through custom maps from myself and Racebox—as well as others I am sure.   Increase shift speeds: as seen in the videos I’ve been posting, the TCU shifts much faster once tuned.   Increased shift pressures: as also seen in the videos, much firmer full throttle shifts.      
    • Per Mark Roberts of Sonictune:     Mark Robert Author At this time, no. No ETA either 2016-17 models. You will be able to purchase and install a 2018.5+ TCU though   TCU purchasing and pricing info! As we near the release of TCU tuning, I am going to answer some questions I get asked often.   What do I need for TCU tuning? At this time, you will need a 2018.5+ TCU to be able to tune. If you have a 2016-to early 2018, you will need to replace your TCU with the newer version. One good way to know if your TCU is good is if you have auto upshift in manual mode in 1st gear around 6500 rpms. If your manual 1st gear goes to 7k rpm and will hit the rev limiter unless you shift, you have the older TCU.   Why do I need to buy another ecu license/phone flash if I already have it on my ECU tune? The TCU is its own computer module. It is completely separate from the ECU. Because of this, you will be required to purchase a TCU license and, if your tuner has it, the phone flash license required to tune it via phone/bluetooth.   Do I need TCU tuning? TCU tuning is NOT required. However, the faster your setup, the more it will assist in track and dragy time consistency.   If I’m ECU tuned by (tuner A) can I get my TCU tuned by (Tuner ? Yes, since it’s a different module and a completely separate flash, you can have two different tuners. However, it is highly recommend that you have both tuned by the same tuner. For me, my TCU tuning will directly complement my ECU tuning style and features and running my ECU and another TCU or vice versa MIGHT cause some issues. At this time and for the foreseeable future, I will only be tuning my current ECU tuned customers TCUs.     I have a SYVECS AWD controller. Do I still need it? Yes! The AWD controllers main job is to control your AWD system. However, with TCU tuning, you will no longer need the auto-shift function as that will be done through the TCU. The AWD controller will still be very beneficial for racers looking to maximize traction on the launch.     Shift schedule changes: holding gears longer at lower pedal input as well as max shift rpm changes. Please note, the new ECU race rom coming out will address 90% of the shitty drivability issues these cars have through custom maps from myself and Racebox—as well as others I am sure.   Increase shift speeds: as seen in the videos I’ve been posting, the TCU shifts much faster once tuned.   Increased shift pressures: as also seen in the videos, much firmer full throttle shifts.      
    • The fancy pants red shock tower brace is finally incoming from MX5 Mania, getting it shipped from 'Merica has been a long and problematic process, and GWR, the 'Merican supplier will not ship directly to consumers outside of the US, Mania basically had to order a heap of them, the colour choice was silver, or red, and we all know anything red adds 5 killerwasps of dynotorques..... Whilst it does fit over a 2.5, and I've seen a few photos and videos of it being installed and fitting, google also says it might get real close to the FAB9 intake front runner, people in the US says it does fit with the FAB9 intake, except for one person who said it slightly touched.......so there is that.....LOL..... As it seems that I am the first in AU to have this combination of parts there's no local knowledge about fitment, so I'm just a willing guinea pig in this endeavour, I'll cross my fingers and toes and hope for the best In other news, I ordered stuff from China  on the same day I ordered the 23° silicone bend from Victoria, the stuff from China arrived a day ago, the 23° silicone bend is still travelling around Australia thanks to Australia Post, and "may" be here next week
×
×
  • Create New...