Rb26 Cam Gears

[Ben C34]

Tomei Test car...

http://www.tomeiusa.com/_2003web-catalogue/e070_cam_RB26.html

But what about those cams all compared on a car with a decent exhaust? It's completely silly to compare to a restrictive exhaust, and unfair on larger duration cams.

[SimonR32]

But what about those cams all compared on a car with a decent exhaust? It's completely silly to compare to a restrictive exhaust, and unfair on larger duration cams.

Well I have a unrestricted exhaust and "smaller" duration cams (either 256 or 264) and they aren't exactly strangling power at over 520kw at the hubs.

If I could drop 10-20hp and pick up a few hundred rpm I'd do it, actually I'd just bump the boost up a tad to get those ponies back and be happy all round

[Ben C34]

My point is you might find you sacrifice alot of power as the comparison isn't like for like.

I certainly agree running the smallest cam to make the power delivery you are after is the best option.

[BlackBox]

Still unsure if I should go the tomei 252, stay standard or if there is a better option?

What if I was to go custom grind? Maybe around 240 and still 9.15 lift.. Still a bit larger than the 236/232 8.4/6.9mm standard

[XKLABA]

From what I could find the Neo turbo exhaust cam is [email protected] @115 LCA

Which I wouldn't change unless going for 10mm plus lift

[G37Sam]

So final verdict, If I'm keeping the Type B's with my 6266'd RB30DET, what's a good starting point to dial them in? +2 IN -2 EX?

I'd like to reduce the dyno tuning time

[BlackBox]

I have so decided to install the type B's in my NEO. The only bad reviews I have got are from people that haven't tried them in a neo

[Ben C34]

Good call guys.

I dont think you can discount the VCT being a HUGE benefit, and make comparisons the 26 with not only no VCT but also substantially longer inlet runners.

Being able to advance the inlet cam and affect overlap by 20 degrees has to make a huge difference.

I'm sure you will both be happy with the cams.

[XKLABA]

I have to disagree, with the correct cam selection and dialled in properly from the get go there should be no need for it to "adjust" timing through the rev range on a turboed engine, also it is only on the inlet cam and in my experiences the best gains are from the exhaust cam

Plus you lose the ability to fine tune with VCT

It also only does timing with no change in lift, the VE setup would be something worth having

[Ben C34]

I can't accept that.

Why do manufacturers go to all the trouble of variable cam timing? Of course cam shaft choice is limited due to emissions etc, but to say it doesn't help is nuts.

[XKLABA]

I said on a turboed engine, I can see its merit on a NA engine but you don't build a turbo and NA with the same principles

My idea is build a turbo engine so the cams take care of the low rev range and the turbo take care of the higher rev range, by building it so the cam are best down low it loads the engine bringing the turbo on sooner, then when the turbo/s comes on the same timing that makes the turbo work keeps the dynamic ratio up making full use of the forced air getting pumped into the engine, then to change the cam timing later in the rev range is taking away from what makes the turbo work efficiently

I will add I'm taking about performance here and not emissions, this is a misunderstanding that I have come across a bit lately

[XKLABA]

For Micky.

Just in case you missed it, my theories at work

I ran the time in the link below on the Wednesday night then that Sunday did this dyno run at a SAU dyno day

[Ben C34]

So why do people pay cash to put VCT onto an rb26?

That graph does nothing for your argument that VCT isn't important or matter much on a turbo engine.

Surely you have seen the difference with VCT in use?

Cam duration and timing is typically a compromise. Variable cam timing of some description takes away part of the compromise.

Edited January 7, 2015 by Ben C34

[GTSBoy]

I will add I'm taking about performance here and not emissions, this is a misunderstanding that I have come across a bit lately

That's an unsubtle barb aimed at me and I never made an issue about emissions in our arguments. Efficiency and emissions are not the same thing unless you're a CO2 nazi. Efficiency is the flip side of power. Improve efficiency, and you can have more of the other.

[XKLABA]

So why do people pay cash to put VCT onto an rb26?

That graph does nothing for your argument that VCT isn't important or matter much on a turbo engine.

Surely you have seen the difference with VCT in use?

Cam duration and timing is typically a compromise. Variable cam timing of some description takes away part of the compromise.

I have no idea why, most likely the fact who ever is selling these has a great marketing team who realise the are a lot of people with more dollars then sense, it's truely beyond me cause every result I've seen on a turbo engine the power is the same till the VCT "turns on" then it screams away from the off setting so my thinking is why not just set the cam to the on setting as there is benefit to the off setting

It may very well be hurting it down low in the off setting aswell, but I have not yet seen someone set it up so the cam is at the on setting from idle right through and please correct me if I'm wrong here but my understanding is the VCT can't change the cam timing until it has enough oil pressure to do so

That graph was origanally posted for a post I made a few pages back about how I'm yet to see a NEO result that matchs it for response making the same power for the same boost level and that graph was when the engine was astill unopened with stock bush bearing turbos and simple bolt on upgrades

I have seen results from and like I said on beats off every where so why have off setting at all

I don't think there is a compromise on a turbo if the cams are selected correctly and dialed in properly, because people want peak HP and do so by putting big duration cams making the engine inefficient off boost inturn making turbos less responsive and now they try and compensate with things like VCT

[XKLABA]

That's an unsubtle barb aimed at me and I never made an issue about emissions in our arguments

Yes and at the same time not just you, but deffenintly mainly you

[brad 110]

Yes and at the same time not just you, but deffenintly mainly you

Mick , you may want to try you theory about turning VCt on at idle and see the effect (if the VCt static adjustment is optimised after modifying the inlet gear to allow front adjustment) you'll find that your 8 track cassette falls clean out of the dash and your flat white in the cup holder becomes a latte

[SimonR32]

With my old Green car with RB25 it has manual VCT switched through Vipec. I think we ended up switching it at around 1800rpm and never switching it back!

Which leads me to the question, apart from a shit idle why not just advance the timing the whole rev range?

[XKLABA]

Mick , you may want to try you theory about turning VCt on at idle and see the effect (if the VCt static adjustment is optimised after modifying the inlet gear to allow front adjustment) you'll find that your 8 track cassette falls clean out of the dash and your flat white in the cup holder becomes a latte

Do you know what the difference is between a flat white and a latte ?

I always get a flat white, with Carmel, cause well find out the difference and you'll know why, bang for buck is why

I not 100% against VCT, I just don't believe the hype people make about It with timing only cause I have been playing with it and studing it for more then a decade when we use to run 4AGE 20Vs in the 1650cc class restricted race cars and there was a deffenint advantage with them but when added to a turbo that only adjusts timing the advatage is lost due to boost, I inow there is all the theory in the world about it should work but that's just the practical out come

But hey, fark it if I'm wrong prove it, show me results from the RB25 VCT where being able to change cam timing mid rev range beats static cam failed in properly and with all the BS people say about the NEO head being that much better then the 26 head it should be easy, I even gave you a bench mark of a complete stock 26 with exhaust and cam gears and the factory shity old bush bearing turbos

[brad 110]

Do you know what the difference is between a flat white and a latte ?

I always get a flat white, with Carmel, cause well find out the difference and you'll know why, bang for buck is why

I not 100% against VCT, I just don't believe the hype people make about It with timing only cause I have been playing with it and studing it for more then a decade when we use to run 4AGE 20Vs in the 1650cc class restricted race cars and there was a deffenint advantage with them but when added to a turbo that only adjusts timing the advatage is lost due to boost, I inow there is all the theory in the world about it should work but that's just the practical out come

But hey, fark it if I'm wrong prove it, show me results from the RB25 VCT where being able to change cam timing mid rev range beats static cam failed in properly and with all the BS people say about the NEO head being that much better then the 26 head it should be easy, I even gave you a bench mark of a complete stock 26 with exhaust and cam gears and the factory shity old bush bearing turbos

I assume you mean that graph is the bench mark?