Hello there Guys! I need someinfo has anyone of you ever running G35c/350z NA with Low compression Piston?
I have just installed some of my internal -

1. CP Piston Low 8:5:1
2. Eagle Rods H beam
3. Cometic Gasket
4. Main & rod bearings
5. JWT 256 Camshaft
6. JWT Valve Spring & shim kit
7. UR Pulley
8. Powerlab Spacer

Now my Car is tottal NA with those setting - Just Uninstall my HKS GT Supercharger. Because im going for JWT TwinTurbo soon. The problem is the car is tottaly no response. Some say because of the Low compression Piston 8:5.1 .

And Now I reliase the Engine RPM got problem from 0 MPH (Stop) to 60+++ MPH.
Starting The Car STOP, Once I hit the accerlation/gas pedal From 850Rpm to 2000 Rpm ---> It is smooth - No problem.
But from 2000 Rpm - It stops/hang for a while like 1 sec and then go all the way up to 6.5K Rpm.

I also Tried from other way- Like If I shift from 1st Gear - while the car is running (5-8Mph) from 1000 RPM ,
It turns the car is smooth again , No problem, No hang/stop at 2000 Rpm.

Thats is the Main Problem guys -- thank you for helping & sharing

 

and revision

 

well hurry up and put the TT on it

 

As I understand your post, you have just installed the 8.5 CR pistons and removed the SC and you have not retuned the engine. Yes, the lower CR ratio has reduced the torque that your motor can put out N/A. If you increase spark advance on a re-tune the situation should improve, Otherwise I wouldn't be surprized that your car runs like crap.

 

Yes the New low comm piston 8:5 & rods - never tuned before. It is just like plug & play. No management at all
I have just uninstalled my HKS GT Supercharger complete kits + the HKS F-CON sz.

Totally NA -- with my setup camshaft, Okada coils, HKS Twin Power, UR Pulley, exhaust, Headers, downpipe, plenum spacer etc.. ( only remain original Stock Air Cleaner )

Last time when I havent installed the HKS SC - with NA setup Plenum Spacer, Okada coils, HKS Twin Power, UR Pulley, exhaust, Headers, downpipe, Blitz Air cleaner (wt Stock Piston & rods), I have beaten the same car G35 Coupe Manual - nearly 1.5 Car away. It was great , But now Even I have the new JWT camshaft 256 - Valve spring additional - He beaten me nearly 2 car away!!!

I thought my car will Scream & Kill my friend G35 -- hehe ended I lost - disapointed because I have upgrade
so many things wt my NA car.

But Im still worrying why is my car from stop and press hard the gas pedal.
The Rpm stop at 2000 Rpm for 1 sec then afterthat going all the way to the Redline.
Maybe something problem with Throttle Response?

Has anyone of you ever had this kind of experience before?
NA with Low Compression Piston.

 

How to Re-tune the Spark advance? any otherway?
Is this normal --

 

If you have plug N play ems there isn't much you can do, unless you have a cipher program you can advance the timing 2 degs across the board. If you have a Utec or other programable ems, just put in on a dyno add timing.
A stock 05 VQ35DE has 10.3 CR and produces 287 hp and 282 ft/lbs of torque. you have dropped the compression ratio to 8.5 and without re-tuning the spark advance map, thus your max torque has been lower as much as 80 ft/lbs. Torque is what makes a car accelerate or pull a load. I would imagine that when you rev past 3500rpms you torque drops off dramatically. This is why your engine seem unresponsive in the higher rpm range. Boost raises your dynamic CR back to where is should be. Sooner or later you will have to tune your new setup for the 8.5 CR pistons.

 

As I told you via PM's, you need proper engine mgmt (at minimum a UTEC, but given your setup, preferably, a Haltech)

 

yeap I have figure it out, will find the UTEC or Fcon V pro to settle my problem. Do you think the SS box in the JWT kits can tune this problem?
anyway thxxx

 

I wouldn't use the split second box as a paperweight, but that's just me - UTEC would be the minimum choice, but even that has its limitations. Haltech or F Con are what I'd select given the build

 

Id listen to Adam's advice as he knows his stuff!

If u have the money, go for the haltech, gives u ability to change cam timing and u don't have to go to a hks pro dealer to get a tune or another map when u want to make changes.

Plus, Haltech offers great customer service from what I hear.

 

I don't think a Utec will work, You need to re-tune the stock spark map or you'll have the same problems when driving and not in boost. The Utec can't change the spark advance settings while driving under vaccum state( No boost). If this car is your daily driver your better off with the Haltech, or any type of Standalone ems. Remember you have to re-tune your OEM spark advance map because you no longer have OEM engine compression. The Cipher program will let you add 2 degrees of timing to the OEM settings, not sure if that is enough, but it should definitely help. If you buy the Haltech, forget the Cipher, the Haltech can precisely add timing at various rpms.

 

a utec would work just fine - I run no where near a factory timing curve, nor does my car ever see boost

Given the level of the build though, I'd go to something more like the Haltech/FCon, etc

 

yeah. The problem is now there are no Haltec or Hks V-pro agent in my place.
I have to call them and make an appointment for the HKS V-pro Tuner to come down all the way from Japan to do the tune.. @ Headache

 

Hal at ip could get u started with some base haltech maps. The haltech is not "locked" like the v pro. That's ur best bet azreen. F*k paying for a goldmeister to come tune all the way from japan, that's gotta be $$$ and a pain when u want changes. Go haltech!

 

But none of the Workshop Tunerz in my State/Country know about this HALTEC -- Because this Car/Engine is very new in here. I think they didnt know how to tune this Engine. The latest is only they know how to tune with e-manage ;(
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