Jump to content


Photo
- - - - -

Boost versus RPM


33 replies to this topic

#1 coalman

coalman

    R33 Member

  • Members
  • PipPipPip
  • 544 posts
  • Location:Pittsburgh, PA

Posted 10 September 2014 - 01:52 PM

I'm wondering how quickly my 2014 GT-R should build boost. When I mash accelerator, boost doesn't build quickly till after 4,000 RPM. Is this normal?

#2 1flossedm3

1flossedm3

    Boost Junky

  • NAGTROC Certified Member
  • PipPipPipPipPipPip
  • 4007 posts
  • Location:Albany, NY

Posted 10 September 2014 - 02:08 PM

Need a little bit more info, video perhaps?
Ryan
2010 Nissan GT-R Pearl White
Proline Built Motor / GT30 / Sheptrans ONE-K/ E85 / 1100HP


Posted Image

Instagram: @FlossyRy

#3 Flash

Flash

    R34 Member

  • NAGTROC Certified Member
  • PipPipPipPip
  • 1865 posts

Posted 10 September 2014 - 02:19 PM

Isn't peak boost 4000rpms?

Nissan Altima Coupe w/ GTR Body Kit


#4 elp_jc

elp_jc

    R33 Member

  • Members
  • PipPipPip
  • 967 posts

Posted 10 September 2014 - 02:44 PM

Mine only goes to 10, and it gets there at half throttle and less than 4K rpm. Curious to see the answer to your question on a car not castrated by low-boost like mine :).

Edited by elp_jc, 10 September 2014 - 02:45 PM.


#5 coalman

coalman

    R33 Member

  • Members
  • PipPipPip
  • 544 posts
  • Location:Pittsburgh, PA

Posted 10 September 2014 - 03:27 PM

I will see when I can get video.

#6 coalman

coalman

    R33 Member

  • Members
  • PipPipPip
  • 544 posts
  • Location:Pittsburgh, PA

Posted 10 September 2014 - 03:28 PM

One other comment. Boost builds slowly to 4,000 RPM then races to peak boost of around 15 then settles back to around 13.5.

#7 coalman

coalman

    R33 Member

  • Members
  • PipPipPip
  • 544 posts
  • Location:Pittsburgh, PA

Posted 10 September 2014 - 03:30 PM

Mine only goes to 10, and it gets there at half throttle and less than 4K rpm. Curious to see the answer to your question on a car not castrated by low-boost like mine :).


10 can't be normal. Losing a lot of power.

#8 240Z TwinTurbo

240Z TwinTurbo

    R34 Member

  • Members
  • PipPipPipPip
  • 1939 posts
  • Location:Charlotte, NC

Posted 10 September 2014 - 03:41 PM

depends on your mods and tune. An example of mine is below with stock dp's in 3rd gear on the dyno.
Posted Image

2006 EVO IX (663hp/527tq @ wheels Shell 93 pump gas)
2009 GTR Premium (707hp/628tq @ wheels Shell 93 pump gas / [email protected])
1971 Datsun 240Z (Let the restoration begin!)

DIY700 - 700hp on a Budget

BW S366 SX-E (6668) TwinScroll Experiment

CURT BROWN 2.15L S362 vs S366 Results - 93 Pump


#9 STIITS

STIITS

    R37 Member

  • Members
  • PipPipPip
  • 683 posts
  • Location:Florida

Posted 10 September 2014 - 03:53 PM

Check for boost leak, loose lines, cuts.....

#10 awdcomplex

awdcomplex

    R32 Member

  • Members
  • PipPip
  • 164 posts

Posted 10 September 2014 - 04:31 PM

I think this is a simple issue of the OP understanding gearing and powerband of a R35. the lower gears like 1 & 2 will spool up boost pretty quickly.

Now if you are attempting to mash the throttle in auto mode while in 6th gear while at 2500 rpms then good luck waiting for the boost to build and the R35 to haul ass.

If you want the car to haul ass at a moments notice be in the right gear where your rpms are at least 4K rpms (drop a gear until your rpms are at least 4K). Soon as you goose the throttle the boost will build very fast problem solved.

Edited by awdcomplex, 10 September 2014 - 04:34 PM.


#11 cfyung85

cfyung85

    R33 Member

  • Members
  • PipPipPip
  • 866 posts
  • Location:Calgary

Posted 10 September 2014 - 04:37 PM

depends on your mods and tune. An example of mine is below with stock dp's in 3rd gear on the dyno.
Posted Image

is this tuned? a stock GTR should run around 14 psi max

#12 Flash

Flash

    R34 Member

  • NAGTROC Certified Member
  • PipPipPipPip
  • 1865 posts

Posted 10 September 2014 - 04:42 PM

damn my peak boost on my tuned gtr is until 4000...

Nissan Altima Coupe w/ GTR Body Kit


#13 240Z TwinTurbo

240Z TwinTurbo

    R34 Member

  • Members
  • PipPipPipPip
  • 1939 posts
  • Location:Charlotte, NC

Posted 10 September 2014 - 06:56 PM

is this tuned? a stock GTR should run around 14 psi max

09 with midpipe, modified OEM catback exhaust, stock dp's, 12+ ported turbo inlets, ported intake, 3" intakes, 1000cc, pumps, self tuned with AccessTUNER Race

2006 EVO IX (663hp/527tq @ wheels Shell 93 pump gas)
2009 GTR Premium (707hp/628tq @ wheels Shell 93 pump gas / [email protected])
1971 Datsun 240Z (Let the restoration begin!)

DIY700 - 700hp on a Budget

BW S366 SX-E (6668) TwinScroll Experiment

CURT BROWN 2.15L S362 vs S366 Results - 93 Pump


#14 elp_jc

elp_jc

    R33 Member

  • Members
  • PipPipPip
  • 967 posts

Posted 10 September 2014 - 07:37 PM

10 can't be normal. Losing a lot of power.

Yeah, I know. That's what 91 octane and high ambient temps (high 90s to 100) does to my car. Worst combination, but it is what it is. Car will be checked at the 1K-mile POS (now due), but everything looks perfect (car is brand new). It's just the damn stock tune. WIsh I knew this before. Oh well. Now that temps are starting to go down, hope to have 13.5 peak (rather than 15 with 93 octane), but when I really use the car is in summer, and that means 10 psi max. Will probably just buy Boostane for those instances and call it a day. Nothing else I can do short of losing my ass selling the car now, but I enjoy how the car drives, and 400HP (what I estimate it's making on 10 boost) is enough for me when not running with the fast guys.

#15 coalman

coalman

    R33 Member

  • Members
  • PipPipPip
  • 544 posts
  • Location:Pittsburgh, PA

Posted 11 September 2014 - 06:16 AM

I think this is a simple issue of the OP understanding gearing and powerband of a R35. the lower gears like 1 & 2 will spool up boost pretty quickly.

Now if you are attempting to mash the throttle in auto mode while in 6th gear while at 2500 rpms then good luck waiting for the boost to build and the R35 to haul ass.

If you want the car to haul ass at a moments notice be in the right gear where your rpms are at least 4K rpms (drop a gear until your rpms are at least 4K). Soon as you goose the throttle the boost will build very fast problem solved.


Actually, I am talking about first gear from the dig.

#16 tjlazer

tjlazer

    SpecV Member

  • Members
  • PipPipPipPipPipPip
  • 3560 posts
  • Location:Tacoma, WA

Posted 11 September 2014 - 09:27 AM

depends on your mods and tune. An example of mine is below with stock dp's in 3rd gear on the dyno.
Posted Image


Nice. I need to plot this out too. (How do you do that?) What's the red and blue?
Posted Image
2010 Nissan GT-R Pearl White Premium
2009 Nissan 370Z Nismo Monterey Blue

#17 sponaugle

sponaugle

    e^-2(PI)(i)(w)(x) dx

  • Members
  • PipPip
  • 326 posts
  • Location:Portland, Oregon

Posted 11 September 2014 - 09:53 AM

I think this is a simple issue of the OP understanding gearing and powerband of a R35. the lower gears like 1 & 2 will spool up boost pretty quickly.

Now if you are attempting to mash the throttle in auto mode while in 6th gear while at 2500 rpms then good luck waiting for the boost to build and the R35 to haul ass.

If you want the car to haul ass at a moments notice be in the right gear where your rpms are at least 4K rpms (drop a gear until your rpms are at least 4K). Soon as you goose the throttle the boost will build very fast problem solved.


Boost threshold (the rpm at which you build a specific amount of boost) will be lower in higher gears, not lower gears. In many cars with larger turbos it may not even be possible to get to maximum boost in 1st gear. Higher gears means higher load and slower acceleration, which will spool the turbos at a lower rpm. This is much more pronounced in smaller displacement engines. In a 2.0L Subaru with a larger GT35R turbo it is often not possible to get >30psi in 1st or 2nd gear.

This is one of the dangers if you tune in say 3rd gear, and then go out on the highway and floor it in 5th gear at 1500rpm. You will hit boost targets you didn't see in the 3rd gear tuning (unless you use a loading dyno correctly, of course. ;) )

Jeff

Edited by sponaugle, 11 September 2014 - 09:54 AM.

Posted Image

#18 sponaugle

sponaugle

    e^-2(PI)(i)(w)(x) dx

  • Members
  • PipPip
  • 326 posts
  • Location:Portland, Oregon

Posted 11 September 2014 - 09:58 AM

Also.. Take a look at this:


Posted Image

This shows the boost from stock, tuned stock, midpipe, and FBO. These are all on the dyno in 4th gear.

This is from my FBO tuning thread: http://www.gtrlife.c...s-lots-of-data/

Jeff

Posted Image

#19 EvilGT-R

EvilGT-R

    R34 Member

  • Members
  • PipPipPipPip
  • 1033 posts

Posted 11 September 2014 - 10:18 AM

Actually, I am talking about first gear from the dig.


Something definitely seems wrong if your not seeing full boost till 4000rpm in first gear.

#20 coalman

coalman

    R33 Member

  • Members
  • PipPipPip
  • 544 posts
  • Location:Pittsburgh, PA

Posted 11 September 2014 - 01:55 PM

Something definitely seems wrong if your not seeing full boost till 4000rpm in first gear.


Based on above comment by sponaugle (which is quite informative I might add), I am not so sure. Apparently, boost builds more slowly in first gear?



Reply to this topic



  

0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users