Jump to content
SAU Community

Recommended Posts

So I've just had my 32 GTR tuned, she made 309 rwkws & 20psi tailing off to 18psi. Basically made the power I was expecting so no dramas there.

The issue of concern is where she's not making full boost til ~5000RPM, reading the RB26 results it would appear virtually everyone with similar mods and power levels are seeing full boost by ~4000RPM.

Below are my mods:

Rebuilt forged RB26

R34 GTR N1 turbos (GT2860-7)

Splitfire Coilpacks

Sard 650cc injectors

Nismo AFM's

Greddy cam gears (2 degrees adv. on inlet, 4 degrees ret. on exhaust)

Nistune ECU

Blitz SBC

Walbro 460lp/h fuel pump (12v direct feed)

Stock airbox with K&N panel filter and CAI

Full custom Exhaust (2.5" twin split dump pipes (350mm separation-1.5" wastegate pipes) into 3" collector into 3.5" decat and all the way to the tip 3.5" with two mufflers)

All intake piping is stock

I did have a boost leak which is now fixed and when doing so and pressurising the system we checked actuators were opening together and they all looked good, the turbos were checked over when exhaust was done and all appeared in good nick <200kms ago.

So any thoughts?! car feels great, mind you I do now have 100+ rwkws more at the wheels so that is to be expected...but on paper it just doesn't seem right.

post-16187-0-29922400-1457570611_thumb.jpg

post-16187-0-49507500-1457570638_thumb.jpg

post-16187-0-71993800-1457570676_thumb.jpg

So you're getting 10psi at 3800. Should be more like 14 at 3800. What did the tuner say?

I'd be looking at exhaust restriction or boost control setup. Eg. did they wind some preload into the actuators?

I dont think "full boost" is a useful term, better off saying X psi IMO.

Get a passenger to watch for you. See at what speed or rpm it hits 20 psi.

BTW boost tails off slowly straight after hitting 20 psi - is this normal for these turbos?

Are the internal wastegates working properly? Not catching anywhere?

Did the tuner spend some time on the adjustable cam gears (I have no idea what the settings should be for your engine)?

If you get the same result as your chart consider changing the boost controller if adjustment doesn't fix it.

Crappy HKS style split dumps ain't helping, nor is the 3 inch small point in the exhaust.

How would they slow spool? I thought the argument against these dumps was boost creep. FWIW, i have the xforce knock offs and have neither issue.

So you're getting 10psi at 3800. Should be more like 14 at 3800. What did the tuner say?

I'd be looking at exhaust restriction or boost control setup. Eg. did they wind some preload into the actuators?

I dont think "full boost" is a useful term, better off saying X psi IMO.

actuators have the typical 4-5mm preload on them, boost control has been played with (gain etc.)

Crappy HKS style split dumps ain't helping, nor is the 3 inch small point in the exhaust.

I spent quite a bit of time reading the threads on here with bellmouth vs. split dump pipes etc. and came to the conclusion that provided the split was long enough the benefits of either were negligible. I've attached a pic above of my system so that you can see its quite different to the HKS / X-Force style dumps you are referring to.....not saying that my system style still couldn't be the issue...though I thought it would have had an affect on power output too?!

Get a passenger to watch for you. See at what speed or rpm it hits 20 psi.

BTW boost tails off slowly straight after hitting 20 psi - is this normal for these turbos?

Are the internal wastegates working properly? Not catching anywhere?

Did the tuner spend some time on the adjustable cam gears (I have no idea what the settings should be for your engine)?

If you get the same result as your chart consider changing the boost controller if adjustment doesn't fix it.

didn't spend a heap of time with cam gears, tuned with them set to '0' and got to around 283kws @ 18psi from memory then from the research I did on here set the cam gears at 2 degrees advanced on the inlet and 4 degrees retard on the exhaust and netted 309kws @ 20psi (went to 20psi and tailed to 18psi without actually touching the boost controller settings.) so I was relatively happy with that change and didn't play around any more...

How would they slow spool? I thought the argument against these dumps was boost creep. FWIW, i have the xforce knock offs and have neither issue.

interested in this too...

It's probably in the tune. We need real world not stupid dyno paper

as I mentioned the car itself feels great.....though I'm not sure if that's because I've been driving it around with <100kws less or if its just the dyno sheet playing funny buggers with my head ;)

Yeah, I notice a difference in hitting "full boost" on the street compared with my dyno sheet.

The way you load it up makes a big difference, well in my case. But I have a turbo that is too big for the engine.

Definitely hear what you're saying, I had an RB30/25 with and XR6T (35/40 - 1.06 e/h) and that was my definition of lag yet that hit full boost around the same as this motor.

Just getting my head around it all I think...and the different types of power and curves....

Edited by mr_rbman

When the car is on the dyno I think its worth paying the tuner as long as it takes to get the camgears right - makes a huge difference on a 26.

I realise this is a completely different turbo set up (GT 3540 on an RB30) but achieved rock solid boost control with a Link, Mac Valve and a Synapse 50mm wastegate:

post-49463-0-53359000-1457661275_thumb.jpg

That's more like what I expected to see Bob, I know my Blitz SBC unit isn't by any stretch top of the line but from what I'd read before purchasing it was a pretty good electronic unit but the boost curve looks more like one controlled by a bleed valve :-/

I have similar mods to you except on an unopened motor, and on an R34

Did a test just now actually.

On my HKS EVC6 at 3900 rpm (or around 96km/h) I get 13.9 psi of boost in 4th Gear. It's an average mild day in Syd - roughly 22 deg and its not crazy humid.

I adjusted the "offset" map feature in all my RPM ranges on my controller and push a tonne more offset than the default 100% as per HKS.

Tune has a massive influence. My last tune with a different tuner was absolutely shite and was a laggy pos with -7's.

I have similar mods to you except on an unopened motor, and on an R34

Did a test just now actually.

On my HKS EVC6 at 3900 rpm (or around 96km/h) I get 13.9 psi of boost in 4th Gear. It's an average mild day in Syd - roughly 22 deg and its not crazy humid.

I adjusted the "offset" map feature in all my RPM ranges on my controller and push a tonne more offset than the default 100% as per HKS.

Tune has a massive influence. My last tune with a different tuner was absolutely shite and was a laggy pos with -7's.

Thanks for that input.

Can gears are setup for peak not response. There is 500 to 650rpm in fixing the cam timing.

Status, what settings would you suggest for more midrange/earlier boost?

I did search here before having it tuned and the settings I went with were the general consensus for good midrange?!

^ haha.. that's IP man, most tuners won't give that out :)

but generally advance intake, retard exhaust.. the magically number really needs decent dyno time to overlay the graphs.

Thanks for that input.

Status, what settings would you suggest for more midrange/earlier boost?

I did search here before having it tuned and the settings I went with were the general consensus for good midrange?!

Settings can only be determined on the Dyno (or repeated back to back street runs). As always every car is different and a good tune is never cheap if you take the time to do it properly.

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

    • For once a good news  It needed to be adjusted by that one nut and it is ok  At least something was easy But thank you very much for help. But a small issue is now(gearbox) that when the car is stationary you can hear "clinking" from gearbox so some of the bearing is 100% not that happy... It goes away once you push clutch so it is 100% gearbox. Just if you know...what that bearing could be? It sounding like "spun bearing" but it is louder.
    • Yeah, that's fine**. But the numbers you came up with are just wrong. Try it for yourself. Put in any voltage from the possible range and see what result you get. You get nonsense. ** When I say "fine", I mean, it's still shit. The very simple linear formula (slope & intercept) is shit for a sensor with a non-linear response. This is the curve, from your data above. Look at the CURVE! It's only really linear between about 30 and 90 °C. And if you used only that range to define a curve, it would be great. But you would go more and more wrong as you went to higher temps. And that is why the slope & intercept found when you use 50 and 150 as the end points is so bad halfway between those points. The real curve is a long way below the linear curve which just zips straight between the end points, like this one. You could probably use the same slope and a lower intercept, to move that straight line down, and spread the error out. But you would 5-10°C off in a lot of places. You'd need to say what temperature range you really wanted to be most right - say, 100 to 130, and plop the line closest to teh real curve in that region, which would make it quite wrong down at the lower temperatures. Let me just say that HPTuners are not being realistic in only allowing for a simple linear curve. 
    • I feel I should re-iterate. The above picture is the only option available in the software and the blurb from HP Tuners I quoted earlier is the only way to add data to it and that's the description they offer as to how to figure it out. The only fields available is the blank box after (Input/ ) and the box right before = Output. Those are the only numbers that can be entered.
    • No, your formula is arse backwards. Mine is totally different to yours, and is the one I said was bang on at 50 and 150. I'll put your data into Excel (actually it already is, chart it and fit a linear fit to it, aiming to make it evenly wrong across the whole span. But not now. Other things to do first.
    • God damnit. The only option I actually have in the software is the one that is screenshotted. I am glad that I at least got it right... for those two points. Would it actually change anything if I chose/used 80C and 120C as the two points instead? My brain wants to imagine the formula put into HPtuners would be the same equation, otherwise none of this makes sense to me, unless: 1) The formula you put into VCM Scanner/HPTuners is always linear 2) The two points/input pairs are only arbitrary to choose (as the documentation implies) IF the actual scaling of the sensor is linear. then 3) If the scaling is not linear, the two points you choose matter a great deal, because the formula will draw a line between those two points only.
×
×
  • Create New...