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Keeping Vct - Ecu And Cam Choice

aDrew_C

By aDrew_C,
in Engines & Forced Induction

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aDrew_C Enthusiast

aDrew_C

Posted
Posted (edited)

Basically just need to know what mods will keep VCT and what ones will not.

I have a microtech LTX-12 at the moment, got it cheap and wasn't concerned about VCT at the time so didn't research it. It's a plugin for an RB25DET, does this ECU support VCT? From searching I can't find anything that says it does, so I'm guessing it doesn't.

Now if I'm right that it doesn't support VCT, I might be looking at a new ECU (depending on how happy I am with my next tune after next mods). So far I like the look of the new Haltech Platinum range as well as the Vipec V88 or Link G4. I will have a speak to my tuner about which of these he thinks is the best option, but need some feedback here about the haltech platinum pro range for R32/R33's. Basically, because I had a microtech, and thus no longer have the stadard ECU, AFM, loom and whatever other sensors that have been replaced, will this cheaper plugin option still be worth it? I don't want to run an AFM, and i know the ECU does support MAP sensors as well as MAF, but would I be better off going with the Platinum Sport 2000 for the extra money considering my already hacked loom and no AFM's etc? Does the Sport 2000 support VCT, I know it supports VTEC, but not being a plugin for an RB25DET would this cause problems or would it simply be a matter of my tuner enabling VCT control and adjusting when it comes on and switches off?

Ok now the next thing - Cams. I know that you can only use an exh adjustable cam wheel as an intake one will not allow VCT to work, but what about drop in cams? Tomei poncams are the cheapest so I'd be looking at some 256 duration and 8.5 lift exh and intake. I've noticed HKS sell their exh and intake cams seperate, besides the reason of countering intake/exhaust flow balance is this also because an intake cam will not allow for VCT to function? I'll only be looking at cams if I can't get the power I want without them, since my goal is 280rw/kw with as much response as possible.

Edited by aDrew_C
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https://www.sau.com.au/forums/topic/294187-keeping-vct-ecu-and-cam-choice/
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R31Nismoid Grand Master

R31Nismoid

Posted
Posted

You can make over 350rwkw with a factory RB25 head. I've done it, Guilt-Toy has also achieved the same.

Bigger cams don't always = best response from what i've seen.

My setup was as responsive as any other. So save your money.

aDrew_C Enthusiast

aDrew_C

Posted
  • Author
Posted

Have been told the same thing by my mechanic, so it's really down to the result I get now. In theory bigger cams should always shift the power curve, but a lot of people here state that poncams (256dur 8.5 lift) have no noticable effect on low end and increase midrange and top end by a good margin. I guess it depends on the turbo.

The turbo is a HKS 2835Pro S and i'll be using a Greddy intake plenum with standard 70mm TB. Respone should be good with this setup but if cams can get the midrange to be a bit beefier while keeping VCT then I'm all for them. Again, it will come down to how the car feels after the first tune.

R31Nismoid Grand Master

R31Nismoid

Posted
Posted

It won't feel as agressive with the stock cams, but that does not mean it is slower :/

You also won't see the difference on a dyno sheet. On a dyno bigger cams always looks better. However if you are running around a circuit/street, that changes.

Cjmartz2k Proficient

Cjmartz2k

Posted
Posted
It won't feel as agressive with the stock cams, but that does not mean it is slower :ninja:

You also won't see the difference on a dyno sheet. On a dyno bigger cams always looks better. However if you are running around a circuit/street, that changes.

Completely agree :blush:

BTW, granthem, are you sure you still have VCT? I didn't know any of the HKS cams kept VCT.

Granthem Mentor

Granthem

Posted
Posted (edited)
Completely agree :blush:

BTW, granthem, are you sure you still have VCT? I didn't know any of the HKS cams kept VCT.

I was under the same impression. I thought VCT would be long gone. But there is a definite kick in the revs, and the Nengun site says they are for NVCS engines (that could mean it is or is not retained however, depending on how you read it).

I have been told the HKS cams do keep the VCT however, and the standard cam gear is still on my intake, with an adjustable cam gear on the exhaust.

Power seems to come on quite agressively with them.

Edited by Granthem
badhairdave Proficient

badhairdave

Posted
Posted
Completely agree :blush:

BTW, granthem, are you sure you still have VCT? I didn't know any of the HKS cams kept VCT.

The 256 inlet for rb25det does. Pretty sure it's the only one

re vct control, just get your self a separate rpm based trigger so it'll be on at idle and switch off at your designated change over point or if you really want to be fancy get a window switch for full factory style operation so it's off up to 1050-1100 and then back on up to the change over point.

badhairdave Proficient

badhairdave

Posted
Posted
Have been told the same thing by my mechanic, so it's really down to the result I get now. In theory bigger cams should always shift the power curve, but a lot of people here state that poncams (256dur 8.5 lift) have no noticable effect on low end and increase midrange and top end by a good margin. I guess it depends on the turbo.

The turbo is a HKS 2835Pro S and i'll be using a Greddy intake plenum with standard 70mm TB. Respone should be good with this setup but if cams can get the midrange to be a bit beefier while keeping VCT then I'm all for them. Again, it will come down to how the car feels after the first tune.

Keep the stock ones in it.

With the same turbo a mate made a peak of 269rwkw without cams, and 271 with....

PM-R33 Grand Master

PM-R33

Posted
Posted

Your ECU supports VCT, ive got a LT12S plug and play. Have you got a hand controller? If so go to screen 29 (Aux options) and there is an AUX RPM ON and a AUX RPM OFF. If you have a plug and play unit it will allready be set and running the VCT.

Regards to cams, the HKS 256 cam allows you to run the VCT, as does the Tomei Poncam. I have had both.

badhairdave Proficient

badhairdave

Posted
Posted
Where they dialed in?

Timing checked, exhaust at zero.

Basically identical engine side to my setup, i found about 30rwkw with the addition of 256/264 with the old t300s as it liked the lower boost pressure higher flow scenario. similar power output too at similar pressure.

The 2835 obviously didn't benefit as much with it's smaller more modern wheels.

Can't remember if there was a significant midrange gain.

PM-R33 Grand Master

PM-R33

Posted
Posted

256's aren't really there for peak power. I didn't gain much peak power with mine (plus did the headwork), however i gained 30-40rwkw nearly throughout my whole revrange which for a street car makes a hell of a lot of difference. My old thread is kicking around somewhere if you want to look for it.

Granthem Mentor

Granthem

Posted
Posted
256's aren't really there for peak power. I didn't gain much peak power with mine (plus did the headwork), however i gained 30-40rwkw nearly throughout my whole revrange which for a street car makes a hell of a lot of difference. My old thread is kicking around somewhere if you want to look for it.

So you have had the HKS cams and the Poncams... why the switch? Poncams get better results?

Our set ups are nearly identicle! And our power outputs are pretty close too... Mine just made 253rwkw on around 16psi on a newly calibrated dyno.

PM-R33 Grand Master

PM-R33

Posted
Posted

Long story with the cams lol. I thought the HKS ones were f**ked so i sold them off and got Poncams. Turned out it wasn't the cams which were the problem and the new owner of the HKS cams got good results from them haha.

Tangles Grand Master

Tangles

Posted
Posted

i love me tomei 256 in/exh. camshafts. 8.8mm springs, ported head

makes the car feel like a throaty 3.0L off boost, and screams to redline with boost on.

made a difference to how the car "feels & drives' without a doubt.

recommended if youve got the coin....... i bought my bits ages ago (20 months?) when the aus:usa dollar was comparable.

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