Tuning Update…still a lag monster.

Thursday, 17 January 2008 | Comments (3) | Categories: Engine

Well the car spent some time on the Allstar Dyno yesterday with Sean at the helm. The aim of this tune was to try and bring the response back down the rev range as it was way up top. This was to be achieved by adjusting the cam timing using the adjustable camshaft sprockets that have been fitted.

Adjustable Camshaft Sprockets

Now this is a time consuming job, as each time you want to change the timing, you need to crack open the rocker cover make the change and screw it back down. It would have been easy if we knew the characteristics of the camshafts themselves, but all we had were the basic specs - 264deg duration with 11.8mm lift on both intake and exhaust.

Camshaft specs

Unfortunately, no matter what was done, we couldn't get any better response out of the engine. We could however put more lag in...but yeah, you probably guess that isn't what we're after. Boost comes on strong at 5300rpm, where I've seen some dyno graphs seeing boost rise from 2500rpm with full boost by 3600rpm. It is however making between 310-320rwhp, but only for about 2000rpm :( So currently in the throes if researching my camshaft options for maximum response. If anyone knows that HKS recommend as the best match for the HKS GT-RS turbo, I'd appreciate it if you could let me know what they say.

Now, onto Motorvation!


Your Comments

Posted by bas van Melis | 17 February 2008 at 11:47 AM

Hi Brendan,

First of all nice website! I run a similar spec s14a, currently maken 387 at the fly. I run Tomei 356 camshafts together with the GT-rs hks turbo. I have full boost @ about 3500 rpm. Runs great.

Regards, Bas

My website is http://www.s14trackedition.nl

Posted by Anonymous | 23 June 2008 at 01:03 AM

I’ve got a HKS GT-RS with standard cams, on the standard manifold.  It starts boosting at 2400 and reaches at least 1 bar boost before 3600 rpm like you described with some of your runs. 

Perhaps your wastegate is opening too early for whatever reason.
Try using the boost controller, inline with the wastegate actuator rather than with a T piece to drain the boost signal (I’m not sure how this is connected on your car, though I’ve found most people use EBCs with a airbleed T piece).  I’ve found better midrange torque with the EBC connected inline, as this keeps the wastegate 100% shut until such time as the target set boost arrives.

You can experiment :
Maybe run a line straight to the wastegate from the throttlebody to observe the natural wastegate spring characteristics first, you should notice slightly less torque between 3-4000rpm due to the wastegate opening slightly, as the wastegate spring is not on/off but variable.  Then try experimenting by blocking the wastegate signal totally with a fuel hose clamp, obviously be careful with your right foot to avoid overboosting.  Then you can see the earliest possible rpm that you can make good boost at with those cams and turbo. 

I haven’t used those cams before, but you’d surely have something by 4000rpm no matter what.

I’ve heard good things about the Tomei 256 cams, and you don’t need to dial them in.

Posted by Anonymous | 23 June 2008 at 01:11 AM

Also make sure that the breather is going thru the intake pipe, so that the AFM registers any extra air getting into the system.  It makes a difference.  It puts a minor vacuum under the pistons on light throttle.

Love your car by the way.
Nice photos.
If I have to work underneath my 180, I can check some of your photos to get my brain thinking about it the night before.

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