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Valve Float - Hardtuned.net
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Valve Float

KillaFlop's Photo KillaFlop 19 Feb 2017

Hey guys,

Johnny & I have reached the conclusion that my S15 is more than likely experiencing valve float at high boost (22psi+).
Essentially after 6000rpm the motor feels like it's choking and needs a few seconds to recover thereafter.
Originally thought it was the high flow cat or dump but after replacing those we're still experiencing it.

There are Tomei Type A Valve springs installed as we wanted to keep the beloved VCT (originally purchased BC Springs but ditched those).
Currently running your basic drop in Tomei Poncams 11.5/256.

Has anyone else experienced my issues with the Tomei Type A's? Would have thought they were sufficient for my purpose.
Or is there something else amiss here?
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Scotties15's Photo Scotties15 19 Feb 2017

i have the Type A's with Procams 260/12. no such issues to report to date and its seen 22psi every time its driven, spikes to 23/24 sometimes.

sure its not a faulty FPR loading too much fuel in, or MAF is dirty etc,

do you have stock FPR?

i had a similar problem with stock fpr and stock injectors when stock turbo and cams was on. replaced both, and never had a problem since. with nismo inj and tomei fpr.
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Dose Pipe Sutututu's Photo Dose Pipe Sutututu 20 Feb 2017

Not fuel related, AFR dead constant

Torque drops significantly once more boost is added however the load cells are referencing similar timing cells...Not MBT related too, as taking timing out makes no difference.
I suspect valve float, as the car made more power/torque with less boost and there wasn't a sharp decline with torque.
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SJB87's Photo SJB87 20 Feb 2017

Have also experienced this with my 15.

VCT
Poncams
Tomei type A springs
T518Z with an external gate

Just after about 6200 the curve almost stops climbing. Tuner put it down to valve float as I'd just recently fixed the VCT gear, recommended Supertech springs as they reckon they've run into this issue with Tomei type A's before since they're only about 10-15% stiffer than factory.

Haven't bothered to do anything about it yet though.
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KillaFlop's Photo KillaFlop 21 Feb 2017

Cheers for replies guys.

Sam - yup sounds like my symptoms, power pretty much plateaus after 6k rpm too.

Sounds like new springs are in order. Any other brands worth looking into besides Supertech that won't kill VCT?
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liambrm's Photo liambrm 24 Feb 2017

Make sure exhaust is free flowing as well and turbine housing isn't too small
Edited by liambrm, 25 February 2017 - 11:37 AM.
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KillaFlop's Photo KillaFlop 24 Feb 2017

Originally thought it was the cat so went catless (for testing) and then to a 3.5" dump pipe... no difference :(
It's got a rear muffler but don't think that'd be it.

It's 0.64 rear on the GTX2867 which should be ok?

Attached is the dyno graph, you can see power/torque nosedives after 5000rpm...
Posted Image
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Scotties15's Photo Scotties15 24 Feb 2017

did some reseaerch, and from what i can find stock springs are like 48lb seat pressure
kelfords are 85lb
tomei type a's area 56lb
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Scotties15's Photo Scotties15 24 Feb 2017

kelford NISSAN SR20DE/T. 'Drop in' PACALOY High performance single valve spring set. For use with OEM retainers and spring base. 85lb seat pressure at 40.50mm installed height. Coil Bind is at 25.00mm

BC Spring Pressure: BC1200 Seat: 1.550" @ 90 lbs / Open: 1.025" @ 220 lbs / Coil Bind: 0.910" (no machine work required)
DIA SET LIFT COMPATIBLE LIFT(mm) SET LIFT REV MATERIAL PROCESS COLOR METER LENGTH LENGTH LOAD LOAD LIMIT ID (mm) (mm) (kgf) (kgf) (Ref.) ø3.9 35 25 10.35 24.2±7% 80.6±7% 53.24 8500 SWOSC-V Nitride Blue SR20
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SJB87's Photo SJB87 27 Feb 2017

What I found from Supertech.

Single Valve Spring Kit
TYPE: Single Spring
PRESS.SEAT: 68 @40.50mm
MAX LIFT: 15.00mm
COIL BIND: 22.70mm
RATE: 9.30 lbs/mm
RETAINER: RET-NSR20/T1
SPRING : SPR-H1021S/SR20
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GTS4WD's Photo GTS4WD 27 Feb 2017

Interesting post,

Firstly I have had an issue ever since I had Tomei Type A Springs and 256 Poncams installed and tuned..

Around 5900-6000 power dramatically drops and will not regain itself until 7000.Been back to workshop thinking tune related and not resolved. Spent around 4 months replacing and fixing everything I thought it was.

Went to another workshop and tried update ecu, retune and even went with another ecu to try and same issue.

Tuner first mentioned valve float and ultimately that was the outcome of the day after 5 hours working on it.
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GTS4WD's Photo GTS4WD 27 Feb 2017

Mods I have

Tomei type a Springs
Tomei pon cams
Arp head studs
Crg manifold
Gtx2867. 64
Nistune
740cc Nismo
Dw300
Brand new VCT gear and solenoid.


Going to have to find a Spring that suited to retaining VCT. Anyone know specs on Performance Valve springs from qld?
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Scotties15's Photo Scotties15 27 Feb 2017

View PostGTS4WD, on 27 February 2017 - 05:55 PM, said:

Interesting post,

Firstly I have had an issue ever since I had Tomei Type A Springs and 256 Poncams installed and tuned..

Around 5900-6000 power dramatically drops and will not regain itself until 7000.Been back to workshop thinking tune related and not resolved. Spent around 4 months replacing and fixing everything I thought it was.

Went to another workshop and tried update ecu, retune and even went with another ecu to try and same issue.

Tuner first mentioned valve float and ultimately that was the outcome of the day after 5 hours working on it.

what sort of power / boost levels was this at? E85?
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KillaFlop's Photo KillaFlop 27 Feb 2017

So to recap:

Stock - 48lb
Tomei Type A's - 56lb
Supertech Single - 68lb
Kelford - 85lb
BC - 90lb

Anyone running Supertech springs retaining VCT?
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GTS4WD's Photo GTS4WD 27 Feb 2017

I'm running 98. On 20 psi I'm seeing 225rwkw up to 6000 then it drops dramatically..
On 15 psi around 190rwkw perfect all way to 7000. The more boost added the worse and more dramatic the drop. Dyno sheet coming

Attached Thumbnails

  • Attached Image

Edited by GTS4WD, 27 February 2017 - 11:58 PM.
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Dose Pipe Sutututu's Photo Dose Pipe Sutututu 28 Feb 2017

tell Jez to pull out more timing on lower boost to atmospheric, the turbo will wake up.

I got Killerflop's car all in by 3700rpm.
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GTS4WD's Photo GTS4WD 28 Feb 2017

I am running an internal gate so harder to control how boost comes on
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liambrm's Photo liambrm 28 Feb 2017

porting the gate helps a lot with a bigger flapper
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liambrm's Photo liambrm 28 Feb 2017

porting the gate helps a lot with a bigger flapper
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Scotties15's Photo Scotties15 28 Feb 2017

WOW hey. !!! i have the 67r with procams and type a's
there is no rev drop at all, through too 7400rpm. just keeps powering on at 22/23psi all day long. VCT is dead, embarking on changing that on thursday.

also by looking at those springs, myself, id be aiming at the supertech's ... goign too stiff does nothing to your head with these sized turbos other than putting unnecessary strain in the drivetrain.

mine also comes on full boost by 4000 :( johnny, might need to show me what le trix are?
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SJB87's Photo SJB87 28 Feb 2017

^ Procams or Poncams?

Bigger Procams will help more up top than Poncams will won't they?
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Scotties15's Photo Scotties15 28 Feb 2017

PROCAM - 260/12
yes they will move more up top.
but if suffereing from valve float id assume they would be worse unless the springs are that compressed they provide the spring resistance needed... cant know..
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GTS4WD's Photo GTS4WD 28 Feb 2017

I've had the rev drop issue for around 4 months now and I've been replacing everything I personally thought it was.

*Dw300, coil pack harness, Z32 air flow meter, coil packs, spark plugs (6 and 7 heat range and all gaps tested, earth kit, fuel pump rewire, upgraded turbosmart iwg, porting to waste gate hole on turbo with xr6 flap.

Problem still was there. Tuner mentioned valve float and I didn't think it could be possible being new Tomei Springs and 256 cams. After diagnosing and testing more things it's the only thing left we have to try. Been searching the net for springs and speaking to my new tuner and I've come down to picking the Supertech Specs:

Seat: 75 @ 40.5 (lbs@mm)
Open (lift): 168 @ 12.0 (lbs@mm)
Max net lift: 15.00mm
Coil bind: 25.50mm
Rate: 7.90 lbs/mm

Tomei type A specs are :

Seat: 56.43lb @ 7%
Open (lift) : 177.7lb @ 7%
Max lift : 12.5mm

Not much specs on Tomei.

I think there must have been a bad batch of springs. Or it might be some other issue. Any one that has any ideas feel free to help
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SJB87's Photo SJB87 28 Feb 2017

Where are you getting the Supertech values from? I pulled the values above from their website.

I only ask as the values are conflicting. Unless they're a double spring kit?
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SJB87's Photo SJB87 28 Feb 2017

Pulled from Mazworx's site regarding Supertech spring kits.

Spring Pressure:
Single Valve Spring, 68 lbs
Dual Valve Spring,GTi-R, 75lbs / add $2.83
Dual Valve Spring, 90lbs / add $3.73
Dual Valve Spring, 106lbs / add $2.83
Dual Valve Springs, 116lbs / add $2.83
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GTS4WD's Photo GTS4WD 28 Feb 2017

There seems to be 2 single versions. Only one listed on official site as you see part numbers are different.

SPRK-H1021S/SR20
http://supertechperf...&ec=334&em=5332


SPRK-H1020S/SR20
http://www.frsport.c...bs_p_15734.html
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SJB87's Photo SJB87 01 Mar 2017

Weird, frsport seem to have an inner and outer diameter measurement which seems to be for dual springs. I wouldn't take it as gospel, unless there are other places that list the 75 pound springs as singles and not doubles.
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GTS4WD's Photo GTS4WD 01 Mar 2017

Got this email today

"SPR-H1020S/SR20 was superseded to SPR-H1021S/SR20 in 2010

Thank you,


Supertech Performance "
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GTS4WD's Photo GTS4WD 01 Mar 2017

So they must have had issues and went down to a lower seat pressure. So deff order from the Australian supertech website. Springs are $15ea. No need to buy titanium retainers oem are fine
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