Dialing In Poncams On Rb30dett

[James_03]

Hey guys,

Last weekend I removed my standard gtr camshafts and replaced them with a set of 260 poncams on my rb30dett. I have them at 0 inlet 0 exhaust at the moment. The power delivery is ok, but definately better with the standard gtr cams. I also cannot get it to idle anymore with it hunting back and forth 200rpm then eventually stalling, is it normal to loose the ability for it to idle?

I know that a tune will more than likely need to take place now, but just curious to see if people have had better success with these cams by dialing them in using a different setting other than 0,0?

How much is the tune dependant on taking advantage of the cams? I just want to know if there is anything I can do to improve response/idle without playing with the tune.

Basically my worry is that I will have to cough for another dyno run just to get my stable idle back, and I just don't know if the gains are going to be worth it, especially if the whole tune will need to be done again.

The tune I have now with the gtr cams is very good and somewhat refined now, it spat out 250rwkw on 14psi, and response was great.

[bubba]

Will need a tune, the engine will now be ingesting different amounts of air at different times.

[James_03]

Yeah that's cool. I didn't think the change in 260's would be drastic enough to leave me with no idle but

Makes sense but all the same.

Ill just leave them at 0,0 and get another tune on it then. I searched yesterday and a couple of ppl had posted recommending +2 in -4 ex, so I thought it was worth asking.

[Sydneykid]

Generally with Poncams the 0/0 ends up being the best all round position. The -2/+4 ends up with slightly more torque due to slightly more boost at slightly lower rpm. Note the multiple use of the word "slightly", it's generaly not dramatic, but it is noticeable. Of course you get nothing for nothing, you will sacrifice a slight (that word again) amount of top end.

Cheers

Gary

[Swiper the Fox]

Degreeing them properly would be a good start.

http://www.skylinesaustralia.com/forums/De...ts-t240804.html

[James_03]

Generally with Poncams the 0/0 ends up being the best all round position. The -2/+4 ends up with slightly more torque due to slightly more boost at slightly lower rpm. Note the multiple use of the word "slightly", it's generaly not dramatic, but it is noticeable. Of course you get nothing for nothing, you will sacrifice a slight (that word again) amount of top end.

Cheers

Gary

Thanks for that Gary, info I was after.

[Sydneykid]

Degreeing them properly would be a good start.

http://www.skylinesaustralia.com/forums/De...ts-t240804.html

Please Paul, help me out here with what that actually achieves? I set the cams at a perfect 0 then I stick the car on the dyno and move the cam timing around till I get the desired result. So why does it matter where I started from (perfect 0) when all that I am interested in is getting the power curve on the dyno that I want? I can understand the process for a control engine, say Formual Ford or Formula 3, where it is important to precisely duplicate the desired cam timing. But the reason for spending time so much time and effort getting it perfect only to go and change it escapes me.

Cheers

Gary

[Dale FZ1]

Question directed at both Gary and Paul:

running a 25 head with custom grind non-VVT cams and hydraulic lifters

Is the process in dialing the cams in any different, or any more (or less) worthwhile than with solid lifters?

A mate suggested that the hydraulic setup introduces a level of imprecision not experienced once a solid setup is used. His suggestion is to follow the route advocated by Gary, while I'd steered towards making the adjustments while the engine is still on a stand and access easy.

As always it's a different path towards the same/similar end, but interested whether hydraulics tend to confound attempts to get them dialed in by conventional means.

Edited July 22, 2009 by Dale FZ1