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Tomei Poncams - RB26 - HELP!

Amaru

By Amaru,
in Engines & Forced Induction

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pnblight Mentor

pnblight

Posted
Posted

Ha Amaru,

Glad to hear someone else benefit from cam tuning as i'm got great results for advancing exhaust and inlet (10deg adv inlet ,8deg adv exh) exhaust is very similar to yours can i ask did you try the inlet adv?

pete(someone might actual believe me know NOT):rolleyes:

Amaru Veteran

Amaru

Posted
  • Author
Posted

Hi pnblight

It was taken back to 0/0 and we tried going the opposite way (retarding inlet, advancing exhaust) to see what happened, and it started running better.

Will try advancing the inlet cam again to see what difference makes.

:rolleyes:

rev210 Grand Master

rev210

Posted
Posted

Just to add to the thread a bit more.

I just had a tune on my old bunky with the tomei cams. Got rid of the breakdown issue ala plug change and gapped to 0.7mm.

Cam timing wise we tried a couple of settings ultimately settled on 4deg & 8 deg retard . The tune was nice and conservative on fuel and igntion to allow the very old motor to avoid too much stress. The boost was onyl 10/11 psi or 0.8 bar. Both my AFM's need a good clean as there is a nice difference between them reading wise on idle.

proengines Rising Star

proengines

Posted
Posted

Does anyone have the lift@TDC figures for the poncams? or the full timing figures/lobe centrelines?

I just thought it might be worth checking that the advance/retard on the cams is actually from where they are supposed to be zeroed.

Also, what are the symptoms of one leaking wastegate on a twin turbo setup?

Scooby Veteran

Scooby

Posted
Posted
Does anyone have the lift@TDC figures for the poncams? or the full timing figures/lobe centrelines?

I just thought it might be worth checking that the advance/retard on the cams is actually from where they are supposed to be zeroed.  

Also, what are the symptoms of one leaking wastegate on a twin turbo setup?

Pretty sure the lift and duration specs are on the Tomei website, accessed through the Hi Octane Racing site if neccessary.

rev210 Grand Master

rev210

Posted
Posted

proengines,

I think you will find no one just 'slaps' cams in. Didn't you properly measure your cam install?

You can spend quite some time altering the cam timing to yeild different power characteristics. Different turbo's / boost etc. all affect the relationship with cam timing and power curve.

Emre Proficient

Emre

Posted
Posted
Quoted from TOMEI.JP  

So as PONCAM, the best duration timing and the valve lifts are decided from torque characteristic and acceleration data that is based on huge numbers of tests both on the bench actual running. You'll get the best valve timing without any adjustment but just a replacement of the factory camshaft with PONCAM.

The cams are ground totally different to factory specs, quite possibly (total assumption) with some retardation on the exhaust side. So, by advancing it 8 degrees, you basically would be returning it closer to factory spec.

It's still amazing how one can settle on 8 degree advance and someone else on 8 degree retard, when according to the manufacturer they should be pretty close without any adjustment.

Mine are going to go in sometime next year, can't wait now.

rev210,

Very nice curve.

The black line, being your second run, was it with no or minimal adjustment...?

Was your first run before the cam change...? If yes, can you post that up as well...?

Cheers.

proengines Rising Star

proengines

Posted
Posted
proengines,

I think you will find no one just 'slaps' cams in. Didn't you properly measure your cam install?

You can spend quite some time altering the cam timing to yeild different power characteristics. Different turbo's / boost etc. all affect the relationship with cam timing and power curve.

rev210,

I didn't install the cams at all. Why I wanted the cam specs is so the cam timing can be checked, it's a bit awkward to do without knowing what the cam specs are.

Why I wanted lift@TDC is so it can be checked accurately without dismantling too much of the car to fit a degree wheel to the crank. It's easy to find true TDC with a dead stop and check the lift against that. It's much quicker and dead accurate, if you have more than the specified lift@TDC you retard the cam, less than specified you advance it.

By the way, I think that you will find that most people who fit cams do just "slap them in" as they dont have the facilities to check the cam position.

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