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Poncams installed... 221 rwkw in RB20

jnr32r

By jnr32r,
in Engines & Forced Induction

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FATGTS-R Experienced

FATGTS-R

Posted
Posted
Nah, power noses over at about 6800.

From what I have seen and experienced the standard cams fall over at approx. 6,000rpm.

Although a lot of cars feel as though they are still pulling away strongly after 6k, mine included, a dyno graph will show power on the decline after that mark.

A good example is Troys RB20 who from memory makes peak power between 6-6.2krpm. But shifts far north of 7,000rpm on occasions.

180bfj20det Community Regular

180bfj20det

Posted
Posted
Surely a much larger turbo would change the power band a bit?

Nope, only cam timing does this and duration and lift. I fitted a GT30 on my car and peak power is the same as it was when I had the standard t3 which means my car is acutually a lot slower down low now because now the cam timing events are still the same ie too early for the GT30.

Turbo provides airflow.

Cam timing determines when this airflow is most efficient.

If you fit big turbo, it will want will not change when the cams open at a certain rpm and thus you will still have peak power at the same rpm. This may not be the case however if your orginal turbo was really shit and couldnt provide enough air through the cams efficiency range.

Cubes Grand Master

Cubes

Posted
Posted

Larger exhaust housings create less back pressure that improves top end VE. This in affect will help extend where peak power is made.

A good example is the rb20 turbo on the rb30det. lol.

Peak power is made by 4400rpm then goes flat and falls off rapidly after ~4900rpm.

The larger exhaust housings raise peak power to around 5800-6000rpm.

Back pressure = reversion.

The stock log manifold = back pressure + unequal reversion.

Which is why an equal length exhaust manifold is best for peak rpm power.

So realistically if you want to keep the stock log manifold keep the cam specs mild.

If you really want to extend your peak power you must not only do cams but also look at your exhaust manifold, ensure the turbo exhaust housing can handle the higher airflow at highrpm.

Possibly why Roy's power looks so awesome.

Nicely sized exhaust a/r equiv to .7 something from memory + a nice exhaust manifold. All he needs now is a nice set of cams. :P

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