Just had Cam Gear fitted, Results

[THE OAK]

Hey Ppls.

Also, I had a run done with and without my exhaust silencer (which I will also post up) and the results are remarkable.  HUGE drop in power through the whole rev range, as well as big boost drop up top.

Anyway, stay posted for pictures.

BASS OUT

hey dude,

i also have a silencer and after i fitted a turbo back zorst and a boost guage i have noticed the most i will hit (psi) is prob just under 9 ish, so about 8-9 then it drops to about 5-6 ish right b4 red line... So can you tell me what the results were like when you removed it...as i think im gona remove it ....guesss ill have to risk another yellow sticker for some extra power!

[paulr33]

the oak: yeah it will be cos the silencer is the bottleneck in the exhaust system (im pretty sure)

bass junky: did you notice the power band change at all after changing the cam? as in you could making the same max power in rwkw but you may find it'll pick up quicker and hit boost quicker as the cam gear gives more low end torque but still gives the same top end rwkw figure, it just gets there quicker and sharper

[Bass Junky]

Here's the Dyno Charts

First (Dyno with and without silencer) is the first run before any work was done.

It shows the power with the silencer in and out.

You can quite obviously see the 20kW and 0.1bar (1.5 psi) of difference.

I was expecting this, and it really shows the value of a good exhaust.

Second (Dyno with and without cam gear) is the runs with the cam gear installed and then the subsequent runs again trying to extract some power from it, but obviously not luck. The car was strapped to the rollers the whole time and was worked on in the dyno cell.

During this period the car was pinging quite readily as the fuel was Ampol "Premium" from Bendigo and the operator could induce pinging at 2500 rpm, standard computer was pulling timing a bit during this period, but all the lines are exactly the same, so there was no obvoius gain.

Third (Dyno final with Optimax) is the final run after the tank had been drained and some optimax was fitted. Again, no gain and the shape of the graph is identical to all others. You can also see the A/F Ratios richen right up in the top range.

So there you have it, and expensive day on the dyno for sweet FA.

The only comfort I can seem to come by is that maybe the difference in the weight of the standard pulley compared to the HKS one might give me a slight advantage due to reducing the rotating mass.

Anyway, I hope you can glean something from this all those R-34 drivers.

Maybe the differnt cams and heads in our cars make adjustable cam gears redundant.

I think I remember somebody saying that cam timing is how nissan retricted the cars in power, so with the magix 208kw in the R-34, the timing was optimized.

Now to go and fit a Power FC to try to fiddle with it some more!!

BASS OUT

[ylwgtr2]

i guess there good for getting the lobe centre figure set up if you have specs on the cam you have fitted....i found it very handy to use

[Sydneykid]

Hi guys, I am sorry but I don't understand why setting it up on the lobes centres on a DOHC engine is important when you are going to move the camshaft timing to where it produces the best power curve on the dyno. I spend an hour or two setting it up on say 118 degrees. That's seems like a huge waste of time to me. I am going to rotate the cams with the adjustable pulleys and take regular dyno readings to achieve the position that gives me the power curve I want. I don't really care whether that's 124 degrees or 112 degrees, as long as it makes the power where I want it.

When we had no dyno, or (heaven forbid) a unaccessable (on the dyno) single cam engine, then setting cams up to the specs was important. But on a Skyline with easy access to a dyno, it's a waste of time.

Moving onto the reason for this thread....

I have only had 2 Skylines that didn't benefit from retarding the exhaust camshaft timing, both were R34s'GTT's, both had Tomei Poncams in them and both had Power FC's. Nothing we did would make more power anywhere, compared to the standard timing position. I always put this down to the Poncams being very accurate from Tomei (ie; they got it right).

It will be interesting to see what happens when Bass Junky (or someone else with an R34 GTT) uses a tuneable ECU with an adjustable pulley on the standard camshafts. I, for one, am gunna watch this space.

[BHDave]

I've gotta say that that is just freakish, same bumps and dips in the curve and everything.

Did you try playing around with the cam timing anymore after the 4deg retarded run? Because a change of that magnitude will have some sort of effect, no matter how small. You seem to have no effect except for minor variations that may be attributed to different environmental conditions.

Is it definately an R34 exhaust cam wheel and not r33? do they have a differnt locating pin position like say an s13 vs s14 inlet cam? Only reason i ask is because those two curves look to be made by an engine that is identical.

Did you try a run at -4 then wind the cam timing back to 0, i reckon somethings out mate, no matter who did the work.

[ylwgtr2]

yes move then to where is good!I agree!But i prefered to 1st set up the cam to where the specs that the cam comes with and take it from there.....I would say that sydneykid sounds like he has quite a bit of experience....so any of his advice is good advice sk

[Sydneykid]

Like the rest of you, I am perplexed (and I don't like being perplexed). Let's say Nissan got it SPOT ON with the R34 GTT camshaft timing. Then if you retarded it 4 degrees, it would be 4 degrees WRONG!. Thus it would make LESS power, not the same power. Certainly not EXACTLY the same everywhere in the power curve. So that explanation is illogical.

I remain perplexed.

[ylwgtr2]

and the moral of the story is....dont buy cam gears for 34 GT-T with standard cams

*edit*dont buy them at all!!(i just read sk's post properly)

[Jay95R33]

Just a thought so don't flame me here

Running crappy fuel and getting the motor to ping (like he did) is gunna make the ECU retard the crap out of the timing right ??

Then going straight to good fuel without resetting the ECU isn't going to do that much cause the ECU has already retarded the ignition.....

I mean, is that how the ECU works? Once it's detected pinging, will it leave the timing retarded all the time until you reset it ?

I say give the ECU a reset and see how it feels. Won't cost you anything except about 15 minutes of your time....

It's got me stuffed that it made NO difference, neither gained or lost power....

Or maybe a REALLY stretched or slack cam belt ??

Now I'm really stabbing in the dark..

J

[Warpspeed]

I can see where Sydneykid is coming from on this, but It really would be nice to know where both cams were in the first test, and where they were in the second test.

Jay is right about cam belt tension as well. If you really heave down on the tensioner you can easily move both cams a lot more than four degrees.

It really was a pointless exercise the way it was done. And no reflection on the workshop involved either. If the customers says dyno my car, than fit that pulley at -4 and dyno it again, that is exactly what was done. Now the result is total confusion.

At the very least the locations of both cams should have been measured after the second test so that they could be returned to that figure later on.

Was the ignition timing checked before the first run? probably not.

Its a bit like stuffing around with ignition timing on the dyno and after many runs saying yep, we picked up some power by advancing it a bit. Later the timing belt has to be replaced, and it is impossible to return the engine to the "good " ignition timing figure because nobody thought to record exactly where it was.

Its really no good saying that it does not matter, every time you adjust the timing belt tension it needs ten dyno runs to get it back to being right, because THAT is the only way to know for sure. Well, yes, and no. I would rather use a timing light, and every time I do an oil change, just have a quick look to see it has not moved from where I know is right.

As far as the ripples in the power curve go, all sorts of tuning factors such as fuel and spark mapping come into it besides small changes in valve timing, and none of those were touched.

The results while unusual, do not surprise me in the least. And yes the factory have changed the valve timing figures quite a bit for different RB engines and different model years. The cams themselves always have the bump exactly at the lobe centre of the first lobe. That is how they are ground on the cam grinding machine.

So the difference in factory lobe centre timing is done with the pulleys. So a set of aftermarket pulleys that will fit any RB engine and are set to zero, might do quite different things to different model years of RB20, RB25, RB26 and so on.

There is a lot more to it than just fitting a brightly coloured cam pulley and setting it to four degrees retarded, and expecting to pick up 15Kw every time.

Time and time again I hear, Yeah and fitting those pulleys will give me an extra 15 to 20Kw, and also I am gunna get a...........

[Bass Junky]

Sydney kid.

Watch this space, as I am currently building the cash for a Power FC.

All results will be shared.

[Guest RedLineGTR]

also why do u rekon stock r34gtt's have more power than stock r33gtst from the factory..??? it would have to do with the timing etc and little things that all add up if abit more time and research is taken.

[Bass Junky]

Yep, I'm beginning to think that.

THe turbo is also slightly bigger on the R-34 GT-ts but I think the cam specs and cam timing would also be optimised

[rev210]

my simple take on the matter is that you have a problem somewhere between the fittment of the new cam gear.

If the factory method was followed this involves the removal and replacement of the cam belt etc..

In most installs the existing cam belt is simply stretched to allow the fittment, this is not a great thing to do on a fairly old belt. The additional stretch may cause an issue. Why not rip out the dial guage and see where things are again?

This is not issolated to R34's , a person who did this on his R33 I know of had the same net result the difference being he experienced a loss of power at any other setting other than factory.

As in his instance there is always an underlying issue. Heat soak in a dyno environment can rob the modest power gains as well.

[Steve]

The thing that really gets me, and points to perhaps another problem is the fact that it didnt make much difference - 4 degrees is enough that you should have notice some result, be it either an improvement or reduction in power.

Sure the cams may be dialed in from the factory, but the power curve should change.

[benm]

My Before/After Results:

http://www.skylinesaustralia.com/forums/sh...5010#post755010

[Ryno]

I also had no bloody luck, when it came to tuning my cam gear, infact I lost power.

My engine is a series 2 RB25DET (1996 ECU) running 7 psi of boost.

With the cam gear set at zero degrees, it put down 154 Kw, with A/F ratio's almost spot on at 12:1

With the cam gear set at 2 degrees retard, it lost about 10 Kw, as the A/F ratioswent to 11:1. I believe if the A/F stayed at 12:1 I would have got more power, as the power curve looked to develop peak power later in the rev range.

We didn't go any further with the cam timing, as time is money, and it looked as though there was nothing to be gained with my Std computer.

Any thoughts?

[Steve]

At a guess, and it is a guess, so dont flame me if I am wrong, it sounds like the base timing wasnt reset properly. It doesnt seem to be a very uncommon problem.

I had the same thing, back to back dynos - but the operator 'guestimated' the CAS position, based on the initial timing setting marks on the CAS. Its pretty common when removing the CAS to put a small mark on it and the cam gear cover so the mech knows approximately where to relocate it before attempting to start the engine.

Unfortuneately when I had it done the first time the operator insisted that the way he was doing it was correct, and that the best setting for an exhaust cam gear was only around 1-2deg retard. He was able to prove his point with his method.

I then took the car to another place, he restet the timing with a timing light, and I picked up 15rwkw through the mid range going from -2 to -4 deg.

Is the cam gear still set to 2 deg retard?

[Ryno]

No we set it back to zero, and the power picked up again.

I think you are spot on with the ignition timing, that's exactly what he did (put a mark on the cam cover, to line it back up on). I asked about the timing light, and he wasn't sure that you could use one on a skyline!

I guess that's what you get for using a Dyno operator in Nowra, he still happily took my $200 though