N/a Cams In A Turbo Engine.

[Oblivion]

Crossed this the other day.

I know it would be possible but what kind of gain would you get respectfully of the fact that it prob would not handle high boost.

[Oblivion]

So, has anyone heard of this or done it themselves?

[carl h]

http://www.tomei-p.co.jp/_2003web-catalogu...haft-specs.html

take a look, you'll see its not an improvement...

[Craved]

looks like the exhaust cam would help though

[Warpspeed]

Messing around mixing factory cams is just not worth the effort. All of these cams are emissions cams and almost identical in specification.

Either leave the standard cams alone, or get some proper aftermarket cams.

[psybic]

I have na cams in a turbo head on a na bottom end. Response is awesome!

[Oblivion]

Ok thanks for the info.

Best upgrade on a stock engine?

Would it be to go a 26 cam set...if so would the lifters needs replacing?

[Cubes]

The rb20 N/A cams trade a little top end mid range. The N/A cams are essentially 'smaller'.

The best upgrade for a stock engine is no upgrade. Spend the $$ on a nice turbo and the rest of the supporting mods then throw decent cams in it.

[impreziv]

if you have an OEM turbo engine, it is best to keep your OEM cams, or replace them with cams designed for your engine.

NA cams that are more aggressive, will have valve-overlap, meaning that at one point in their cycle the intake valve is open at the same time as the exhaust valve. so if you use this in a turbo engine, all your boost will go in through the intake valve, and out the exhaust valve before the spark even fires.

if youre boosting a mild NA engine (meaning that the engine isnt a very high performing NA engine, like less than 100hp/L of displacement), then you should usually keep the stock NA cam for low boost.

one good example is my VW 2.0L 8v engine (makes 110hp). there is no valve overlap on the stock cam, it is great for boosting. but my friend's Honda B18C5 has a small amount of overlap, so he changed the cams before running too much boost.

[Cubes]

impreziv,

The rb20det cams run less duration and lift, BUT they do run more overlap, around 8degree's from memory.

I'm running the standard N/A cams in my rb25 head, the inlet is the same as the turbo cam however the exh. cam runs slightly less duration and lift.

The 25 na cams also run an overlap of around 8degree's where as the turbo's run 0 degree's overlap.

But yes, I experience a little funny flat spot at low rpm where no matter how much fuel I push in it still reads lean. Maybe the overlap at that rpm is such that the charge is blown straight out the exhaust.

[impreziv]

yeh, the flat spot is prolly the boost escaping.

i dont know alot about the RB25's cam specs, but i can imagine it to be ok on the top-end.

[Cubes]

Here's the cam specs if your interested.

[RNS11Z]

I know its not an rb but on my sr i have just fitted an na regrounded cam into my s15, will let post dyno results up soon, as i hope to get it tuned on wed.

h.