Rb25 Poncam Issue = Missing 80kws

[rev210]

Changing the cam timing is not a simple thing. Saying this cam timing for x motor and so on is misguided. There are lots of variables. It isn't somthing you can approach with a 'bolt on boy' attitude and expect to always have a win.

[paulr33]

does help but youve changed far too much to even get an idea of whats skewed the results, it could be as simple as the afm ducting trashing the afm signal around and bending the tune. or it could be the cams are offset or too big/small etc (i dont know) or it could be something else is wrong, cam timing is wrong, vct is off etc etc...

anything odd in SENSOR SW CHECK when u do a dyno run or drive around?

do the results change if you pull of the afm ducting and leave the AFM open mouthed?

the only way u will know its the cams 100% is to put the old set back in and prove it, then and only then u will know for sure its them and can work out why, currently we are guessing. try and take out some of the possibilities to make it easier to work out which one is the baddie

[rev210]

definately

* get adjustable cam gears.

* degree wheel check the cams initial timing.

* alter timing and fuel maps for every adjustment made to the cams at the dyno.

* unless you have a 'clone motor', cam timing seldom ends up exactly the same as another engine.

* you can alter the shape of the power graph massively with adjustments to cam timing and appropriate alterations to timing and fuel maps, this is a good thing to have access to exploit it!

* a good cam install and setup can take plenty of time to do right the first time (again if your motor isn't a clone of someones that has already done the hard work).

[GTR1993]

when your motor was rebuilt, have your decked the block, got a different thickness head gasket? All of these will make 0 not zero, on my GTR cam timing found me like 70 kw as they were set incorrectly, and even both at zero was still wrong.

Edited December 31, 2006 by GTR1993

[dangerman4]

do the results change if you pull of the afm ducting and leave the AFM open mouthed?

open mouthed?

its only 4:30 on new years eve and pauls allready vision impared..

as stated on page one.

i replaced the 4 inch elbow from the turbo to the afm with stainless instead of silicone.

[dangerman4]

when your motor was rebuilt, have your decked the block, got a different thickness head gasket? All of these will make 0 not zero, on my GTR cam timing found me like 70 kw as they were set incorrectly, and even both at zero was still wrong.

yea the block and the head were both decked slightly and im running a genuine nissan head gasket. so it may be a little out, but if anything that would only be retarding the cams a half a degree maybe.

[Cubes]

RE: The cam timing being thrown out with the block being decked etc..

Another reason to use a tensioner on the idler side.

The first reason., They are less than half the price from nissan.

[dangerman4]

RE: The cam timing being thrown out with the block being decked etc..

Another reason to use a tensioner on the idler side.

The first reason., They are less than half the price from nissan.

to true

but why would anyone buy them from nissan?

surely everyone knows you can get the exact same bearings for less then half the cost from a local supplier.

So hows the 10 sec auto 32 going Joel?

[Cubes]

to true

but why would anyone buy them from nissan?

surely everyone knows you can get the exact same bearings for less then half the cost from a local supplier.

So hows the 10 sec auto 32 going Joel?

lol yes..

I had a couple of bearings pressed in from CBC for all up around $38 or so.

Its interesting Nissan use 2 bearings within the shell where as Holden on their tensioners/idlers use a single bearing. lol.

My 10sec 32.. lol only a few more bits to get.

[dangerman4]

back on topic.

has anyone found there intake vct pulley had slipped or wasnt set at zero?

[rev210]

An example of cam timing changes I can give you on an RB , my old GTR with stock cams ran the happy +2 intake and -4 exhaust with stock turbos.

When the Tomei cams came along I ran +3 and -2 on stock turbos

To get the same shape on the power curve with more power everywhere with 700hp Group A turbos I had -2 and -5. Another guy with the same sized turbos shooting for more power had radically different cam timing again to reflect the rpm and higher boost he was running.

Each step of the way a retune took place.

As a point of interest each tune with the tomei's had the cams set at 0 and 0 at one point. They made less power than stock up top when matched to stock turbos and the power fell off at high rpm particularly with the group A turbos when at 0 and 0 as opposed to other settings.

Porting the heads and enlarging valves also can have an effect as does different manifold designs both intake and exhaust.

You just need to spend more time on the dyno adjusting and tuning for the cams. There is probably nothing wrong at all with anything.

[BHDave]

back on topic.

has anyone found there intake vct pulley had slipped or wasnt set at zero?

Mine looks like it hasn't moved from the day it was installed. I'm assuming your talking about the grub screw adjustment on the back of the pulley? I have a stock engine though so just left it alone when installing my cams, didn't go the extra yards to dial everything in.

Just one other thing that may be skewing your results: Is the vct still working properly? Have you done a run with it off and on to see what happens?

Have you looked at the numbers on the handset? stuff like peak afm voltage, peak injector duty and the like to see whether they are significantly down on the old peak numbers? As these are only looking at the engine, rather than the drive line it could give you an indication as to whether the engine is down on power at least.

[SLIMVLT]

does the car feal faster i bet it probably does. you have got a highstall.

that will cause a drop in power but you will still have a freaking quick car.

ive seen plenty of drag racing boys who run 10's disapointed cos there highstalled car doesnt make huge power at the wheels. this doesnt mean squat to the times the thing runs. (these cars are high hp cars too)

also u said that u where geting a boost spike to 27 psi and now its stedy at 24 that would be helping the power output.

[sky30]

gizmo tune was 26psi droping to 24 psi at redline

pfc ebc was constant 24 psi to redline

The spiking boost you previously had with the old setup would have given a lot more midrange compared to a constant lower boost level.

[dangerman4]

The spiking boost you previously had with the old setup would have given a lot more midrange compared to a constant lower boost level.

yea im more concerned as to why the power curve is so much lower.

as i now have the poncams in, they should more then compensate for the high stall i would have thought

[Abo Bob]

Sometimes these bigger stallys don't work perfectly out of the box. I would be thinking about tuning it again with a stock converter in it. If the one you have is slipping too much or not locking up properly then your top end will suffer.

Speak to Mike before you try this though. He will definitely have a better idea than me.

That said, there are plenty of other sensible things being said in thios thread. It's a tough one and hard to know where to start. There are a few simple and cheap/free things mentioned here that you can do first though.

I personally don't think that just by replacing the cams and keeping them at 0 can do this if everything was done right. Playing around with adjustable cam gears might get you more power but I really don't think this is where your power went.

When I put my poncams in I gained about 30rwkw without even getting it retuned. (Auto) I would also normally expect you to at least make the same power with less boost.

Good luck mate.

[Fastrotor]

When i fitted the 3000 stall from mike in my 33 4door my mph dropped 5 !!

But et's dropped .7 !

When are you going to run the car ? Anxiously waiting for results

[dangerman4]

When i fitted the 3000 stall from mike in my 33 4door my mph dropped 5 !!

But et's dropped .7 !

When are you going to run the car ? Anxiously waiting for results

still no track in SA so i have to wait..

very keen to get an 11 or close too...

[Devils_Advocate21]

Old thread dig up yes i know but curious did you ever solve your problem darren? or is it to this day still a mystery where the power went was it the stall convert or dialing in the cams, Im sure a few people may be intereested to know if they are to follow down the same path

Cheers

A

[4door_Sleeper]

Hi Darren

I,m also curious - did u solve this, and if so what was the problem?