Cam Timing- Rb26

[iplen]

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.

[N1GTR]

Install them at the dyno before the tune

[Don Dada]

the basics have been retard the inlet, advance the exhaust.

From research I think its the other way around to increase low to mid range power

[GTRsean]

That's what I thought!

The other way you mentioned would be top end and less low and midrange torque.

[iplen]

Okay, well my mechanic has no sense of adventure, so they are staying 0 until the dyno (possibly because I am racing him in his 180 tomorrow..) thanks anyway guys

[snozzle]

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

[Fullboost_Performance]

Agree with N1GTR, adjust them on the dyno, a friend of mine set his the same spec as mine, went to the dyno and made 12kw less ! Different engine different setup required.

[iplen]

Well as it turns out... The front of the exhaust cam is destroyed, so timing could be moving anything upto 15 deg... Explains why performance has been all over the place

[SS8_Gohan]

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

[NSNPWR]

My inlet was '+1' and exhaust was left at '0' when it had stock cams...so every car is definitely different.

[STATUS]

hmm get more adventurous (like double) on the inlet, its where the gains are.

[chrisking666]

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.

[SS8_Gohan]

^ you mean the other way around yeah?

EDIT: did i just fail in internet sarcasm

[Beer Baron]

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.

[STATUS]

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.

[HarrisRacing]

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.

 

[Predator1]

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.

[The Bogan]

Is the ignition pulling timing because of high IAT?

[GTSBoy]

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.

[Predator1]

11 minutes ago, The Bogan said:

Is the ignition pulling timing because of high IAT?

Yes from memory. I cant remember how much timing he added up top but it wasnt much at all.