Jump to content
SAU Community

Recommended Posts

Just got my adjustable cam gears from Just Jap, and will be fitting them over the weekend, looking through a few threads (trying to use the search function incase this has already been discussed in past seven years etc) the basics have been retard the inlet, advance the exhaust. Is there a pretty common degrees that works? I understand engines are different etc, but, the standard cam timing on these engines are identical, and the standard cams are all identical, so surely there is a pretty well recognised adjustment. Car only has -7s and exhaust/filters. It will be going for a PFC and tune soon.

Link to comment
https://www.sau.com.au/forums/topic/364112-cam-timing-rb26/
Share on other sites

when my car was tuned (stock cams, -7 turbos) tuner told me the inlet liked to stay on 0 and the exhaust got retarded 2 degrees (1notch) and made a tiny bit more top end

hmmmm... i'm pretty sure you'll find most people like the inlet moved on a few more degree's than that -should be able to pick up 300-400 rpm better response with the inlet advanced and without really any top end loss

if you've got adj cam gears, i'd have a play, you might have a bunch of midrange you're missing out on :)

  • Like 1
Link to comment
https://www.sau.com.au/forums/topic/364112-cam-timing-rb26/#findComment-5813396
Share on other sites

  • 3 weeks later...

Retard the exhaust 4 deg and it will be on boost in no time, i'd leave the inlet at 0. You have nothing to loose retarding the exhaust just be sure to reset your ign timing.

I have played around with mine quiet a bit and the difference in lag from 0 to retarded 4 deg is awesome, it is MUCH more responsive but it might/will fall over in the higher rpm.

Link to comment
https://www.sau.com.au/forums/topic/364112-cam-timing-rb26/#findComment-5848292
Share on other sites

no, he's right. you retard the exhaust cam, and yeah it makes a big difference. every car is different though but generally I've found with stock cams on a 26 you end up in the sweet spot somewhere between 2-4 degrees retard on exhaust side, and anywhere from 2-6 degrees advanced on the inlet side.

  • Like 1
Link to comment
https://www.sau.com.au/forums/topic/364112-cam-timing-rb26/#findComment-5851587
Share on other sites

no, he's right. you retard the exhaust cam, and yeah it makes a big difference. every car is different though but generally I've found with stock cams on a 26 you end up in the sweet spot somewhere between 2-4 degrees retard on exhaust side, and anywhere from 2-6 degrees advanced on the inlet side.

retarding the exhaust helps with top end generally, advancing the inlet helps response. I generally go small retard on exhaust but big advance on the inlet. Doing what chrisking666 suggested will work (same power curve but later) but wont have the benefit of the response.

  • Like 1
Link to comment
https://www.sau.com.au/forums/topic/364112-cam-timing-rb26/#findComment-5851689
Share on other sites

  • 5 years later...

Back from the dead.

I confirmed 300 rpms earlier spool with exhaust retarded -4 deg (CRANKSHAFT degrees), and Intake cam advanced 6 deg (CRANKSHAFT degrees) on a 2.75L stroker w/ BW 8374 EFR .92 turbo with very little if any loss on top end. Gained MASSIVELY from 4k to 7k rpms (no kidding 30+ rwhp across the board). Same boost pressure (20 psi) on pumpgas.

 

Dyno Cam changes converted.JPG

  • Like 1
Link to comment
https://www.sau.com.au/forums/topic/364112-cam-timing-rb26/#findComment-7812525
Share on other sites

  • 6 years later...

This is interesting... I was wondering why my setup wasnt making anymore boost. Maybe this related maybe not. I was looking at some of my pics and noticed the cam gears were at ZERO for both intake and exhaust.

My setup is BNR32 with a built 3.2, Hypertune FMIC bla bla, 9180 with 1.05 on a CNC head with 278/286 cams. On the dyno, we couldnt make anymore then 23-24psi. turbine speed was around 105k, and my EMAP ratio was higher, meaning turbine was being choked.

How would dialling in my cams change my power curve? It made only 530~awkw on around 23-24psi on pump. The turbo is rated to 900 theoratical, but Im only at around 800~ at the fly. Whenever he tried to add more boost, the fkn IAT would sky rocket.. even at 24psi, the IAT would be around 60~ by the end of the dyno pull. The tuner said he would check the cams but i guess he didnt, so im kind of annoyed... but the low down torque of this setup is nuts.

Link to comment
https://www.sau.com.au/forums/topic/364112-cam-timing-rb26/#findComment-7979649
Share on other sites

38 minutes ago, Predator1 said:

rated to 900 theoratical, but Im only at around 800~ at the fly. Whenever he tried to add more boost, the fkn IAT would sky rocket.. even at 24psi, the IAT would be around 60~ by the end of the dyno pull.

So what you need to do is plot where this operating point is on the compressor map and see why the efficiency is so crap and what direction you have to go in order to get it to work better.

The thing is, just because a turbo is "rated" at 900, does not mean that you can reasonably make that amount of power on a given engine. Let's take an extreme position on this. Instead of a 3.2, let's say that you try this on a 6 litre version of an RB26. Same efficiency as an RB, just twice as large. It is going to make about twice as much power for any given boost level, right? Or, more to the point of this, it will take a lot less boost at any rpm to make a given amount of power. So, let's say you want to get 900HP out of it. How much boost is that going to take to do that? A lot less, right? So it will be way over on the RHS and down low on the compressor map. Down where the efficiency is shit. Can you actually make it work from that position? Hell no. Anything you do here is just going to make it walk up the map towards the right. In the same direction as the island on the map runs, but off to the RHS. If you add boost, it will flow more air and you go up diagonally to the right. It will always suck. It needs a bigger turbo, so that at the lower boost levels required to make the power, it will be closer to the middle of the island on the map.

So, with this 9180, I have no idea where you'll be on the map at 800HP, but I'm willing to bet it's the wrong place. What we'd call a bad match. I'm going to go play with matchbot right now to find out.

Link to comment
https://www.sau.com.au/forums/topic/364112-cam-timing-rb26/#findComment-7979652
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now



  • Similar Content

  • Latest Posts

    • I've heard the Tomei USA head gaskets are decent if you want to o-ring the heads but otherwise not recommended.
    • The 296mm rotors are the R33 turbo brakes. The 310mm rotors are the R34 turbo brakes. The calipers are nearly the same, but not. They're the same caliper but the R34 caliper has longer legs so that it sits out far enough to go over the rotor. The pads are the same for both. When you say, "I bough tsome EBC"....did you just mean pads? Or rotors? 310mm rotors fit under 17" wheels. There may be some wheels without enough clearance though. I can't fit my fingers between the barrel of my wheel and the "corners" of my R34 calipers, but there is plenty of room behind the spokes. This is on Enkei RPF1. You can fit 324mm rotors inside a 17" wheel, but I'd be willing to bet that it would be close to impossible with the Nissan/Sumitomo caliper (using an adapter, of course), because the Sumitomo caliper is fatter than the Brembo caliper that is supposed to go on the 324mm rotors.
    • Hi. Can someone tell me what brakes(and mainly WHERE) can i buy brakes on R34 GTT? I bought some EBC which SHOULD go on my car(i have GT but it has GTT brakes) but it does not fit, Brakes are "too" small(296mm) Are 310mm be good or? I have 17 inch wheel so no "big boys" but for me driving i just need one that fits and i can get here in EU/Czech.
    • Since winter isn't that harsh anymore in Poland, i will definetely drive it 365 days a year 😉. But if the snow hits i will try it for sure and let U know. Only swap i am planning to do is of course R34 GTR front 😍.
    • Hey. Very valuable information about pitwork, I will pay attention when buying any consumable parts 🙏 As for the carpets - I got a handful of information from nengun, from which it appears that indeed the carpets for the driver's side are OEM. They are not able to show me any pictures due to the long chain of different sales entities but after I place the order, as soon as the goods arrive at the nengun warehouse from which they will send the shipment to me they can send me photos and if my purchase differs from OEM I can immediately return it / cancel the purchase. I think I will give it a try 😉. Of course i'll let you know what's what as soon as i get them P.s. I know the topic is not relevant to the thread, but both nengun and amayama have these SICK 😍 trunk room lamps available. Do you know anyone who ordered them? I need to have one in my car
×
×
  • Create New...