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roba

By roba,
in Engines & Forced Induction

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GT-RZ Community Regular

GT-RZ

Posted
Posted
my car did this. i spent months and months chasing the problem. Cams are not too small, i am making 375rwkw with STOCK cams.

I think the issue is cam timing. Getting the cam timing right on a RB30 is quite tricky. I would first start by setting both cam gears to 0 and then tuning it and see what power it makes. Dont be suprised if the power sky rockets. on my RB30DET the car makes the most power with the ext cam gear set to 0.

Set them all back to stock and try again - report back with results

I wondered about this.

Do you have two tensioners? Or the idler on the exhaust side and a tensioner on the intake side?

I can't remember the post but it was suggested to keep an idler rather than another tensioner on the exhaust side for easier tuning. (obviously the 'new' drilled location for the intake side tensioner stud determines if you can get the correct tension with an idler and tensioner)

Guilt-Toy Grand Master

Guilt-Toy

Posted
Posted
I wondered about this.

Do you have two tensioners? Or the idler on the exhaust side and a tensioner on the intake side?

I can't remember the post but it was suggested to keep an idler rather than another tensioner on the exhaust side for easier tuning. (obviously the 'new' drilled location for the intake side tensioner stud determines if you can get the correct tension with an idler and tensioner)

I have one idler and one tensioner. This issue is a pain in the friggin ass. I pulled my hair out for months trying to chase the 50rwkw i had lost. The timing marks were never 100% spot on, but we left it and said it was close enough but it was out enough to make a big difference in power.

Once it was fixed after hours and hours of stuffing around the first run produced a extra 45rwkw without any extra tuning / changes. I could not believe it. The previous dyno run was the day before then i took car home fixed it and came back early the next morning.

This issue needs to be looked at - you need to be 100% sure the timing marks are spot on 100% and this also means removing the harmonic balancer and making sure the bottom cog mark and the top marks are 100%. Also take the plugs out and turn the motor over by hand and by started motor quite a few times and re-check before putting it back together.

roba Enthusiast

roba

Posted
  • Author
Posted

Autronic SM4 ecu

Initially the timing was set to 0 - 0 on the pulleys, last time I was strugling to make power this was checked using deg wheel and dial gauges etc.

We found the correct cam timing after dialing in was 7deg Retard and 7deg advance (In & Ex). - it gained a massive amt of pwr.

I thought I read in one of sydneykids posts years ago this was normal due to the extra deck height Is this correct??? I expect it is cam specific as well?

cheers rob.

roba Enthusiast

roba

Posted
  • Author
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Initally when it was making 250rwkw we dialed in the cams properly (as well as all the other stuff listed on the first couple of posts) and the power jumped up to 370rwkw.

We have played with the cam timing on the dyno to find the sweet spot. Power has only gone up not down so I dont think we are too far off from when it was properly dialed in.

My engine builder wants to change the cams to increase the duration at 0.05" - esp on the exhaust side.

He has shown me specs of HKS RB20 cams with 238 deg at 0.05" (exh) compared to my 216 deg at 0.05".

Im just trying to be certain its the right thing to do before throwing any more money at it!

Cheers.

  • 3 weeks later...
psi Experienced

psi

Posted
Posted
Well im pleased to say I found the restriction (yes in the exhaust).

Got it retuned this week and made 470rwkw and 2100n.m torque at the hubs.

Will post a dyno sheet when I get one printed.

So...

What was the problem exactly??

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