Shifting The Powerband

[R31Nismoid]

OP6 = R34 turbine housing.

[PM-R33]

i don't think they had obvious markings on them mate.

Well considering the three most common choices of cams in a RB25 heads are:

1. Stock cams

2. Poncams

3. HKS cams

Then you should be able to tell (or post up some detailed pictures and I can tell you since I have had them all) which one of those three they are or if they look like something different.

Edited May 6, 2010 by PM-R33

[Dose Pipe Sutututu]

He did mention he already has Poncams, installing an adjustable exhaust cam gear is silly, the Poncams have been already engineered for good mid response.

- Adjust your gain setting so the boost comes earlier

- post up your timing map, maybe your tuner was lazy and only tuned from columns 12+ to get you your kW figure and nothing else, you be amazed how many lazy tuners there are out there, that just subtract 5 degrees from the map from rows 15+ and then do a map trace and only tune on full throttle on the dyno

[STATUS]

To be 100% sure they are aftermarket cams, pull camcovers off and measure the height of lobe and base circle diameter with vernier clamp.

Aftermarket cams should increase mid to high hp, torque. Can create a bow look to dynograph at lower rpms when cams have enough duration, lift. Also aggressive enough cams should create a lumpy idle (or stock / Tomei cams that had camgears adjusted). Tomei Poncams probably would have a smooth idle and look similar to stock cams, unless you adjust the camgears to make idle lump.

This dynograph shows what happens when intake, exhaust cams are adjusted on RB20DET (should be similar with RB25DET) -

http://www.uniqueautosports.com/Dyno/yx32gtstdyno.gif

Not to be rude but is blatantly clear that the ramp rate was changed for the both cam gear changed run to make it look better.... so the graph is pointless and misleading.

[wolverine]

Trent is the change in ramp rates evident due to the earlier boost response shown on the graphs?

[juggernaut1]

Can't say I've seen too many (any) DD's using a ramp rate of 13.

[Harey]

I agree with Ash. I would be looking at the boost controller settings. Most hiflows I have seen go straight to say 18psi, hold 18psi and then drop off at the end. Yours is 16psi at 3500rpm, 17psi at 4500rpm. It just gets over 17psi for a short time so I would hardly say its running 18psi.

Set it up to go straight to 18psi or even a bit higher and then leave it drop off to 16psi near redline. Especially in the lower revs it doesnt hurt to have a bit of extra boost to get going.

I dont think its an exhaust restriction because it still makes good top end power.

[gt-ahhh!]

I agree with Ash. I would be looking at the boost controller settings. Most hiflows I have seen go straight to say 18psi, hold 18psi and then drop off at the end. Yours is 16psi at 3500rpm, 17psi at 4500rpm. It just gets over 17psi for a short time so I would hardly say its running 18psi.

Set it up to go straight to 18psi or even a bit higher and then leave it drop off to 16psi near redline. Especially in the lower revs it doesnt hurt to have a bit of extra boost to get going.

I dont think its an exhaust restriction because it still makes good top end power.

i wound the gain up from 19% to 30% (the max setting is 35%), and the start gain from 15psi to 15.5psi. it didnt make any difference as far as the seat of my pants is concerned. i still think its lacking power below 5000rpm.

will look at the other issues.

[Harey]

A whole 0.5psi

I know its a bit worrying but the tune should account for a bit more boost. if you are really worried try on a dyno. I would try 17psi so it flattens out to 18psi. will still be the same boost up top.

Edited May 7, 2010 by Harey

[gt-ahhh!]

A whole 0.5psi

I know its a bit worrying but the tune should account for a bit more boost. if you are really worried try on a dyno. I would try 17psi so it flattens out to 18psi. will still be the same boost up top.

im not worried about running more boost. id happily run 25psi if it made more powah.

the set gain of 15/15.5 psi setting is when the ebc starts to regulate boost, according to the greddy manual. and they recommend setting this for 2-3 psi below desired pressure. yeah i can wind it up to maybe 17 or such, ill try it tomorrow.

would 1 psi at 3500-4500 really make much difference? cant hurt i guess!

[Sheriff Wan]

Have you had the tuner go over it?

I know some people just tune for WOT and think that will satisfy 99% of people.