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Cam Gear Adjustment To Reduce Lag.

chrisking666

By chrisking666,
in South Australia

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chrisking666 Explorer

chrisking666

Posted
Posted

Hi guys and gals, so I have built a new forged RB26, with 270 10.8mm tomei cams and a 70mm billet turbo (slightly bigger than a t04Z), problem is its very laggy, it starts to make boost around 3500 1-2 psi but takes till about 5700 to get up to even 8-9 psi and then full boost of 19 at about 6500. I have adjustable cam gears and want some info on how advancing or retarding inlet/exhaust mght help my lag problem to make the car more responsive.

Im quiet aware that big turbo = lag, but this is a bit frustrating.

I had an rb30 with t04z and it would not come on boost with your foot on the brake and flat out on the gas standing still. We went drag racing and it ran a 13.6, spoke to a guy in the pits who said to roll the cam 1 whole tooth to advance the cam timing, next pass was an 11.1!!! It came on boost at least 1000 rpm earlier!

So just want to know if it might work the same way with this engine. Any opinions would be appreciated..

Thanks Christian

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Martin Donnon Mentor

Martin Donnon

Posted
Posted

You will make - some - more torque down low adjusting the cam gears, however its like pissing in the ocean to top it up. You might change the level, but you wont really notice it. Your turbo to engine to tune match is wrong, simple as that :action-smiley-069:

whatsisname Grand Master

whatsisname

Posted
Posted

But in a freezing Southern ocean it can really help to warm the inside of your wetsuit, or so I hear.

I'd rather a healthy area under the curve at the expensive of peak power than visaversa, both at the same time would be nice but you can't have it all, unless you go to extremes. I dropped exhaust housing size to gain response and mid range and never looked back.

SLED Grand Master

SLED

Posted
Posted

it amazes me that we need to retard and advance valve timing that much on an RB to get a better deal in the performance stakes down low..........bit like robbing Peter to pay Paul.

Nissan clearly had no idea what they were doing when they structured the RB's valve timing :/

chrisking666 Explorer

chrisking666

Posted
  • Author
Posted (edited)

Why such a big "f off" turbo mate? Why not go with something slightly smaller to get good value out of the built RB26??

Im building a spool stroked 3.4 liter motor next, just wanted to spend some time doing the new motor so I built this one to fill in the time..Im sure i'll have no problem selling it when the new motor is ready to go.

Im quiet aware of the lag issue with a big turbo, just wanting to know of peoples experience with varing the cam timing to counter act somewhat the large frame turbo hence the tread in the first place.

Its running a .81 exhaust housing, 4 inch dump, and 3 inch exhaust but the exhaust will be upgraded very soon to 4" all the way.

Don't get me wrong its great fun to drive but just wanted to get the spool time down as low a is possible with the 26 capacity motor.

Thanks for your feedback everyone

Edited by chrisking666
chrisking666 Explorer

chrisking666

Posted
  • Author
Posted (edited)

retarded to -4 is generally the consensus for Rb26 exhaust cam gear setting

not too sure on the intake, advanced to +1 or +2 ?

I was thnking the same thimg myself, I have retarded the exhaust cam 4 deg and it has definatly made it come on earlier prob 500-700 rpm earlier with no sign of falling over in the top end.

Im waiting for the adjustable inlet cam gear to arrive, I ordered 2 and only one turned up! pain in the arse really but when it gets here i'll advance the inlet 2 deg and see what happens.

Cheers Christian

Edited by chrisking666
bezender Grand Master

bezender

Posted
Posted

Im building a spool stroked 3.4 liter motor next, just wanted to spend some time doing the new motor so I built this one to fill in the time..Im sure i'll have no problem selling it when the new motor is ready to go.

Im quiet aware of the lag issue with a big turbo, just wanting to know of peoples experience with varing the cam timing to counter act somewhat the large frame turbo hence the tread in the first place.

Its running a .81 exhaust housing, 4 inch dump, and 3 inch exhaust but the exhaust will be upgraded very soon to 4" all the way.

Don't get me wrong its great fun to drive but just wanted to get the spool time down as low a is possible with the 26 capacity motor.

Thanks for your feedback everyone

a shot of nos low in the rev range would get the turbo spooling faster. or something as simple as a smaller intercooler so there is less volume to be pressureised by the turbo. i binned my omg look at me whale baleen cooler and put on a smaller unit, still get same power but less lag.

something like >>>THIS<<< could help improve the effectiveness of the cooler.

Luke_ENR34 Grand Master

Luke_ENR34

Posted
Posted

Thats what I'm trying to do, save buying 2sets of turbs's I'm going be running the gtrs's on the 26 with a small ARC 70mm twin entry cooler with cam gears and see how I go. I know it's gonna be laggy as Fu*k but time will tell.

SLED Grand Master

SLED

Posted
Posted

If your mind is set on that particular setup, go and see Martin, get the thing tuned for Hoon Juice, then not only will you be able to throw a bunch of valve & ignitition timing at it but extra boost too.

That'll help with what you're looking for.......plus a few extra killawasps which can never go astray.

Krishy even has a cigarette hanging out of his mouth whilst pouring the stuff into his tank :yes:

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