Jump to content
SAU Community

Recommended Posts

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.

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.

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

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • It would be different if the sealant hadn't started to peel up with gaps in the glue about ~6cm and bigger in some areas. I would much prefer not having to do the work take them off the car . However, the filler the owner put in the roof rack mount cavities has shrunk and begun to crack on the rail delete panels. I cant trust that to hold off moisture ingress especially where I live. Not only that but I have faded paint on as well as on either side of these panels, so they would need to come off to give the roofline a proper respray. My goal is to get in there and put a healthy amount of epoxy instead of panel filler/bog and potentially skin with carbon fiber. I have 2 spare rolls from an old motorcycle fairing project from a few years back and I think it'd be a nice touch on a black stag.  I've seen some threads where people replace their roof rack delete with a welded in sheet metal part. But has anyone re-worked the roof rails themselves? It seems like there is a lot of volume there to add in some threads and maybe a keyway for a quick(er) release roof rack system. Not afraid to mill something out if I have to. It would be cool to have a cross bar only setup. That way I can keep the sleek roofline that would accept a couple bolts to gain back that extra utility  3D print some snazzy covers to hide the threaded section to be thorough and keep things covered when not using the rack. 
    • Probably not. A workshop grade scantool is my go to for proper Consult interrogation. Any workshop grade tool should do it. Just go to a workshop.
    • In my head it does make sense to be a fuel problem since that is what I touched when cleaning the system. When I was testing with the fuel pressure gauge, the pressure was constantly 2.5 bar with the FPR vacuum removed. When stalling, the pressure was going up to 3.0 bar (which is how it should be on ignition).
    • ECUtalk pages don't mention they support the ABS computer (consult port has more than one CAN), so you might just need a different scan tool. But, I would expect ABS is a different light to the brake warning/handbrake light, do you see an ABS light come on for a few seconds when you turn the key from ACC to IGN? But since you said: I'd have a look at the ABS sensors in the rear hubs to make sure they are not damaged, disconnected etc.
    • OK, if it idles at 1000+ with the AAC, its not an idle airflow problem. The cold start valve just gives extra air when the engine is cold, but you have enough air without it to idle at 1000. I think you are back to a fuel problem, sorry. Can you see the fuel pressure staying constant or does it drop as the revs drop to a stall?  
×
×
  • Create New...