Hks 264 Inlet Cam For Rb25Det No Vct

[WARLORD]

1) Hi,would anyone know the correct way of installing this cam and turning off the vct.?

2)what would the pro and cons be for using a 264 in let cam besides a lumpy idle. ?

3)my mid range is from 160kwatw to 260kwatw then up to 315kwatw just so we know what i may loss or gain.

idea of my set up,on my old tune as i have not had it tuned since i added new mods, just had it run on dyno so i know it safe.. build engine,greddy plenum, hks256/264 cams,head done with o/s valves,90mm t/b,hks 3037 pros,.87,++++++++++

i trying to gain more top end with this change but i can't find much info on this subject ive look on the net and found little to nothing on this if someone can shine some light on the subject it would be good.

[Dale FZ1]

VCT offers a better compromise between low-mid range torque, and stopping the torque falling off at high rpm (ie helps the top end power production).

Fixed cam timing brings compromises, but you can obviously move things around to a degree by playing with cam timing.

It would be interesting to see/compare the exact cam lobe specs with what you're considering vs what you are running, but it appears the total lift is close enough to the same, and the duration figure changes a small amount. Possibly you can gain more top end, but you'd think the compromise would be a disproportionately high drop in the low-mid range torque due to deletion of the VCT.

I'd think that some cam combinations would offer very good scavenging and hence lower retained combustion chamber temps, more high end torque etc. But I'd also think they would be generally associated with increased noise, dropped mid range torque, and generally increased fuel consumption.

It's just a matter of moving the balance point of compromises around.

If the cam is a "drop in" spec ie. no clearancing required in the head, it would be a simple matter of installing and tryinhg the thing out. Disable the VCT actuation via the ECU and try the thing out.

[JonnoHR31]

yep just unplug the solenoid and/or turn it off in the ecu. the oil feed also lubricates the front cam journal so leave that as is

[Rolls]

VCT offers a better compromise between low-mid range torque, and stopping the torque falling off at high rpm (ie helps the top end power production).

VCT only helps down low/midrange by advancing the intake cam. Above 4.5 or 5k (can't remember the factory point) it turns off as it would kill top end power.

Edited July 24, 2011 by Rolls

[Dale FZ1]

Exactly. Removes the compromise associated with fixed cams where you can have either beefed up low-mid range, or top end torque, but not usually both. So essentially VCT helps both parts of the torque curve.

[WARLORD]

ok the cam is a drop in rb20 hks 264 9mm lift. so there will be a drop in the mid range torque, now my torque level is 844nm a drop in the low- mid range might help with the wheel spin problem i having (tyres are m/t street radials 16/60/255 with a 2way kaaz 4.3.1 ratio which might help the low to mid loss i think) so the real interesting thing is will i gain much more torque+kw at the top ? if the vct stops at 4500rpm and redline is 8200 i guess it should gain something.i also am running a 75 shot of nos with a nos controller that i can change when it comes on so i could play with that to help with loss in mid range if its a very large loss.

i do remember a green r33 that had a gtrs turbo which i had at one stage and he made 301kw at db4's with the same set up but no vct and a 264 hks 9mm lift cam +cam gear i could only get 278kw.could there be that much to gain from this change?

has anyone done this mod on sau ? there has to be one person.

thanks guys

[WARLORD]

Exactly. Removes the compromise associated with fixed cams where you can have either beefed up low-mid range, or top end torque, but not usually both. So essentially VCT helps both parts of the torque curve.

but if the vct stops at 4500 how would it help top end would it not just help low more than high end

[JonnoHR31]

because it means you can run a cam thats good in the top end then use the vct to beef up the midrange aswell. without vct you have to run the same cam timing all the time so the grind has to be a compromise between top end power and midrange torque.

[Rolls]

Exactly. Removes the compromise associated with fixed cams where you can have either beefed up low-mid range, or top end torque, but not usually both. So essentially VCT helps both parts of the torque curve.

But it doesn't, the top end would be identical with or without VCT as it isn't active after 4.5k. Basically if you do a dyno run with VCT on and off. you'll see the top end is the same, it is only the bottom/mid range that is fatter with the VCT on for the 1 to 4.5k window.

edit: Oh right johhno, I guess thats not really the VCT doing it though, it is the different cam profile, but I get what you are saying.

Edited July 24, 2011 by Rolls

[WARLORD]

because it means you can run a cam thats good in the top end then use the vct to beef up the midrange aswell. without vct you have to run the same cam timing all the time so the grind has to be a compromise between top end power and midrange torque.

so if the cam profile suggest that a 264 9mm lift 110^ no vct cam is good for mid to high range would that not help the mid range as well

here is a dyno i found of a vct run and then a none vct with a 264 cam the mid range dont look so bad.

[Dale FZ1]

If a single camshaft is not that expensive, why not give it a try? Surely they offer the potential to give that top end lift, and you don't have any issues with taming the mid range down a bit.

I have fixed cams in my 30DET, and no complaints for what I want it to do. Tighe 805C, 8.9 lift 265 duration. There is no massive hump in the torque curve, so it just knuckles in and drives. Gives a very linear acceleration right through the range. But its rev ceiling is down 1100 on yours and I've never dragged so take from my comments what you can.