Jump to content
SAU Community

Recommended Posts

Hey mates I'm just looking at the dyno sheet I got with this beast. I'm wondering about the boost curve. Does it show that it doesn't make full boost until 7500 rpm? I would expect it to make that at worst case 5700rpm then the line to stay flat till max rpm.

It's a gt35 .82 rear on a rb20. Garrett turbo. China stainless manifold. 38mm wastegate screamer pipe.

Boost controller is a turbo smart dual stage manual one.

No idea what spring is in wastegate

Looking for some ideas on if that's how it shud be or if something's goin on with setup.

I understand its not the ideal size turbo but that's what's on it. Il live with it

Thanks mates

post-34298-0-01513500-1409233809_thumb.jpg

Link to comment
https://www.sau.com.au/forums/topic/447367-rb20-gt35-dyno-graph-boost-curve/
Share on other sites

Have a look through the RB20 Dyno sticky thread. For example, the dyno sheet on the top of the last page shows the sort of shape you should be aiming for manifold pressure (boost). I'd guess your setup is always going to be horrible with a turbo that big. Suggest you change your mind about living with it. You want to enjoy driving your car don't you? :)

Yea I've seen a lot of dyno sheets on there. I believe it should be as I suggested and reach full boost at a certain point in the 5000rpm range and hold it but want to confirm something may be up with mine and if something isn't right suggest what is causing it.

Edited by joe blo

The turbo is too big, and the .82 housing is more suited to a 3L engine. A stock RB25 turbo can make that power, and come on by 3k on a 2L.

It could make bulk KW if you were willing to rev it to 12k and make use of that amount of airflow. (porting heads, massive cams etc.)

Yes, the peak boost is at 7500rpm but that's not so much a factor of turbo lag as it is boost control - its boost creeping which is why it keeps climbing and ending up at it's highest there. Looks like the gate is opening at around 6000rpm, which is closer to your expectations and I'd say is probably more or less what you're going to get on an RB20.

  • Like 1

Yes, the peak boost is at 7500rpm but that's not so much a factor of turbo lag as it is boost control - its boost creeping which is why it keeps climbing and ending up at it's highest there. Looks like the gate is opening at around 6000rpm, which is closer to your expectations and I'd say is probably more or less what you're going to get on an RB20.

Yea I did consider it could be boost creep but I thought that if it could hold the 12 psi setting fairly well it should be able to control 21 psi.

If I put a spring closer to 21 psi in the wastegate could that make it better? Could probably assume the current spring is below 12 psi

That will increase the boost, you should hit 21psi by 10k or so. :P

An electronic boost controller may help with the boost curve, but a heavier spring will definitely be required in the wastegate.

as said totally wrong setup so 7500 would be correct

to give you an example I ran an rb22 with gtx3076 with 0.82 tial 44 Vipec 88 and e85 with basically everything you can get for that setup (cams dialled in etc) and had full boost at 5200

as all said above get rid of that turbo its never going to work

food for thought (ignore if you wish).

  • Sell turbo
  • Sell manifold
  • Sell gate

then

  • buy a brand new hypergear highflow
  • stock manifold
  • spend all leftover cash on hookers and cocaine
  • and whatever is left on tyres
  • Like 1

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

    • Car has been running great, I've put about 300km's of break in time on it. First thing that stands out with properly sealing rings is no more noticeable crankcase smell coming out of my catch can. This may seem insignificant, but the constant smell while driving around was infuriating. It's also nice to see my oil level remain stable. Two new issues have developed that I only noticed this weekend though. There's a very noticeable driveline vibration past 100kmh. I only noticed it now as I've been babying it under 100kmh in the backroads. This comes as no surprise as I'm running a one-piece shaft, and I paid zero attention to my driveshaft angle when I put everything back in. I also have a fair bit of voltage drop on hot starts. The starter audibly is forcing. No issues on cold start though. I must not have removed all the paint under my main block ground during assembly. I'll try and take care of both those issues this week once the kids are asleep.  I also received all the parts I was missing for my direct port setup. I will hopefully have pictures of that up soon. I'm hoping to get back on the dyno the week of June 30th as I'll be on vacation. I'm confident I should be able to make north of 500rwkw on pump gas and WMI. I'll go back again later this summer with E98, but I want to confirm my ethanol content sensor is working properly first. I've never seen it read anything but 11%. This makes sense for our 10% ethanol content pump gas here, but I would expect the occasional movement between fill ups. 
    • 75% complete. Will now need to get a new axle with 5x114.3 hubs and then figure out how to customize some mudguards for it once the wheels are on.
    • Trailer prep is underway... Lined up the wheel to get a rough indication of how it would sit Then removed all the bits (as far as possible) and gave the frame a light sand and quick lick of paint   Then added some carpet
    • okay, so I figured this out, removed needles and reinstalled after swapping the gauge face on my triple gauge for my ER34, all work and look good. I tried to do the same for the main cluster, but the main cluster gauge faces are dished, the replacement gauge face are flat, so due to the dish in the org face ,mounting backing plate (clear) and depth of the needle, the flat gauge face will not work. I notice that R34 gtr gauges are flat, appears to be different clear backing plate that aren't dished. are these available, or what have others done to install flat gauge faces?
    • Cheers mate. Seems some people get lucky others don't. It looks like the motor was detonating (to be expected if it was overboosting I suppose) as the pistons had a lot of detonation damage, and the bearings were stuffed. The bores were very scoured too, not sure if that's from the pistons or bits of ceramic turbo. By the by now. Have been trying to avoid the rabbit hole too much on the rebuild, and there's been a few hurdles along the way, but with any luck I'll have the car back soon™. Might even pop up a thread then.  
×
×
  • Create New...