Need Some Advice Rb26, Pfc, Cam Gears, Cams?

[djr81]

djr81,

if we compare what mine has 'down low' just from this graph you can see tomei cams absolutely hand standard ones thier ass not the other way around.

I'm investigating going down the same path again and I have absolute confidence of the outcome on stock turbos, as unremarkable as they are.

Um, posterity. The only ones getting rich of dyno tunes are the oil companies & the workshops. But I digress.

From your chart one of two approaches work:

1. Cams.

2. Larger turbos.

From my chart it would appear that the combination of the two sucks wang for mid range grunt.

Good work with the cams. I am curious to see what changes you made to the phasing and their affects on the torque curve. I reckon my thing would benefit.

Edited January 21, 2008 by djr81

[Beer Baron]

yeah that is a nice result. but I still believe you could have got the same result with just adjustable cam gears and the stock cams. and you are right, you can never have too many charts, so much to analyse. case in point:

my old set-up. stock turbos, 1.05bar boost, cat less, cat back exhaust and power FC with fairly conservative tune (stock AFMS, stock injectors, stock IC etc). this was after adding and tuning cam gears. no changes made to the boost controller and no changes made to the tune at all (which was tuned without the cam gears).

here it is:

and this was after some more tuning of the power FC.

[rev210]

Um, posterity. The only ones getting rich of dyno tunes are the oil companies & the workshops. But I digress.

From your chart one of two approaches work:

1. Cams.

2. Larger turbos.

From my chart it would appear that the combination of the two sucks wang for mid range grunt.

Good work with the cams. I am curious to see what changes you made to the phasing and their affects on the torque curve. I reckon my thing would benefit.

I can't spell sorry....

My bigger group A turbos installed later on were heaps laggier. They were a fairly big turbo afterall , there is only so much you can do with big turbos. I also dusted piston 3 (lowish compression) so the 280rwkw tune I put in later was pretty faggy and I didn't spend as much time on cam timing.

However I would gladly take the $50 challenge against a set of GT-SS turbos and 260 tomei's and stock cams (with adjustabe gears) on the same motor. Actually I might challenge myself to that one as well I happen to have the GT-SS units.

The setup of the cam timing is a tricky thing for many, including me. It took lots of time to set up mine on the dyno (I was fortunate it didn't cost me much). I dropped the allen key and burnt my hand so many times too altering the exhaust cam.

I'm like a broken record I know but, good matched cams work a treat if you bother with them and work out what to do.

Beer Baron,

Most stock cammed and even cam gear adjusted GTR's have basically the same power as yours at 3,000rpm. ie: not oodles.

On your curve see if you can find another 40rwhp or so at 3,000rpm with adjustment of cam gears on stock cams, to match the tomei's I assure you it's a waste of time trying buddy. You could maybe try race fuel? or a 50hp shot of nitrous?

Also, think about how much additional power curve I would have on there at 3,000rpm with the same boost as you. I had standard front and dump pipes on mine. But, basically the same setup as yours with the exception of running a cat.

Edited January 21, 2008 by rev210

[Beer Baron]

yeah for sure. 3,000rpm is not exactly setting the world on fire. but 3,500 is getting there and 4,000 is humming nicely. outright power was not really what I was into though. more just the difference between before the cam timing adjustment and after the adjustments. 26kw atw is a pretty handy gain, and it's 20-30kw throughout the range.

You could be right and the cams may give an increase down low and up top too, but damn it's a lot more money from cam gears to cams. unless you can do it yourself properly it's a $2000 + job to do even 'bolt in' cams.

having said all that my new motor does have cams. and they are 260/9.15mm tomei cams. but it also has a lot of headwork etc and will be running much more boost to make the most of them.

I still think on stock turbos there are many better things you can be doing with $2500 that buying and having cams fitted. but it's an interesting discussion none the less.

[djr81]

Maybe we should all harden up & put some money down in a "Who has the most powerful RB26 at 3500rpm" competition.

For me I am surprised (pleasantly) that cam phasing can have such an effect at low rpm. Certainly something I should go back to looking at.

[rev210]

I think the cost aspect is certainly a downside for sure.

But, when you are looking at the alternatives for limited top end power to get a much faster car. They aren't bad value really. I was lucky

* $800 second hand tomei's with gears

* $300 dyno use (mates rates).

I sold the GTR cams for $200 so all up I was $1,100 down for them. Pretty good value for me.

But you can imagine what driving the car was like in terms of on-call power. Really cool having pull from 3,000 rpm.

With bigger huffers you say good by to that sadly. Be interesting to see what I can do with the GT-SS units. I'll make notes of cam timing settings when I get round to it.

BUT.

If the motor I had wasn't so old and I wanted to lean on the turbos for more boost. At the time I could have had that 50rwhp more advantage from 3,000rpm over a cam gear adjusted stocker plus the better part of 30+rwkw all the way up the curve more than adjusted stock cams . Thats not a chicken feed power gain. I say that knowing I can replicate it again.

Edited January 22, 2008 by rev210

[RNGTR]

No need to look at a cam catalogue until you are well past 400rwkw...

We rarely put cams in RB26's anymore and are making more/better power than ever!!

This man speaks the truth... Whatever GTR i build next time will have stock cams & GTSS turbos after driving RPMZ's car.....

[TommO]

I will be able to help provide before and after results with 2860-5s (currenty fitted) and 260/260 9.15mm Poncams/Cam Gears (unfitted). I was actually doing it to beefen up my midrange (not that it's laggy now but more is better!) but based off this thread, perhaps that won't be the case... I've read plenty of internet talk that says otherwise, but who knows, you guys have real world experience.

My car goes in today to have them fitted and tuned (+ cam gears adjusted). I made 280kw@4 last weekend in shootout mode 6F on teh same dyno it will be getting tuned on. I'll ask for a before and after dyno sheet on the same printout so we can have our 3500rpm battles.

Should have some results to post on Thursday.....

Edited January 21, 2008 by TommO

[DAN00H]

I can't understand why there are many saying a cam with greater lift (therefore greater cylinder filling capacity) won't work better than a stocker... isn't that what the mines cam package is all about?

[rev210]

I can't understand why there are many saying a cam with greater lift (therefore greater cylinder filling capacity) won't work better than a stocker... isn't that what the mines cam package is all about?

Basically that's what I was asking someone to help me understand in terms of why the stock cams are so much better.

I've seen evidence to the contrary, my own car on the smallest turbos.

What I'd like to see is a graph showing the low rpm greatness of stock cams on the upgrade turbos (like the N1/GT-SS/-7's/-5'S) exact same turbo type / boost and prefferably engine. Also with a list of all the settings for both (I don't ask too much do I).

Wonder if Sydneykid would like to stick his nose into this thread?

Edited January 22, 2008 by rev210

[depalma-bcnr33]

these responses have kicked me in the brain, REV210 love the curve on your graph and is exactly what im aiming for... i hope to upgrade to some hiflowed 33gtr turbos eventually, and still manage a good low range rpm. your right, the cams handed ass to the stockers... is this all dependant on the tune as the djr81's graph had much less down low?

Tommo, looking forward to your post of results will be the 'be all and end all' of proof i guess.

i think im going to need some tissues after reading these responses...

Edited January 22, 2008 by depalma-bcnr33

[rev210]

these responses have kicked me in the brain, REV210 love the curve on your graph and is exactly what im aiming for... i hope to upgrade to some hiflowed 33gtr turbos eventually, and still manage a good low range rpm. your right, the cams handed ass to the stockers... is this all dependant on the tune as the djr81's graph had much less down low?

Tommo, looking forward to your post of results will be the 'be all and end all' of proof i guess.

i think im going to need some tissues after reading these responses...

My dyno was also done 'bonnet down'.

I really haven't seen any evidence provided that explains how relatively big 260's on a stock turbo do such a mint job on stock turbos and yet don't work for another 100rwkw and then suddenly they work well again once you hit 400rwkw.

Although I completely dissagree with this idea in both theory and practice ,I genuinely am interested in knowing why people think this might be the case.

The tune I had was a nanna one, so just like others with stock turbos you can push them up in power. The cams will see every bit of the curve 20rwkw or so better and depending on the flow of restricting items like exhaust etc. you ought to see more peak power than you will ever manage from stock cams and turbos.

What's important about the install of the cams is that you do it spot on and spend some time with the adjustment of timing. I am kicking myself that I didn't write the cam timing down on a bit of paper I actually kept but, I have this feeling I tried 8 retard exhaust and 2 retard intake , 6 deg retard and 6 deg retard also rings a bell but, might have been for the group A's.

Anyway you need to spend good time and money on that side of things and completely ignor the top end whether it's up or down in the initial stages of tuning, come back to it later.

Edited January 22, 2008 by rev210

[TommO]

Got my car back today... well, bugger all mid range gained but a fair bit of top end. In total, it cost me $2k for parts and labour and tuning to have the cams/gears installed.

Beer baron's old dyno sheets certainly show more power than me around the low end, I pass him at around 5000rpm and my rev limit is 8000rpm. It's still really nice to drive power wise from 3k on, I think this dyno graph makes it look much worse than it is. Most of my racing is drag stuff anyway, so this powerband is fine for me....

I would like to try some different turbos though, I'm actually surpised how little mid range it shows on the dyno... feels great out driving around in but yeah..

You can see old power vs new power in one of the dyno sheets. The black line power run was done 2 weeks ago at a dyno day

Edited January 24, 2008 by TommO

[rev210]

Hi TommO,

what are the mods you have to the car?

Pretty great improvement over the stock cams I'd say. You have picked up an earlier spool and 14-20rwkw and then a big fat load more power in the top end.

The low rpm tuning isn't really shown on that graph ,looks like a top end focused power run/tune that dyno readout.

I'm interested in what cam timing settings you tried and where you ended up?

Edited January 24, 2008 by rev210

[TommO]

Hi TommO,

what are the mods you have to the car?

Pretty great improvement over the stock cams I'd say. You have picked up an earlier spool and 14-20rwkw and then a big fat load more power in the top end.

I'm interested in what cam timing settings you tried and where you ended up?

Mods:

Apexi Power FC

Greddy E0-1 boost controller

660cc Nismo injectors

Nismo Fuel Regulator

Bosch 044 fuel pump

Turbo back Fujitsubo Exhaust

Garrett 2860r -5 turbos (3 months old)

RB25 AFMs

Apexi Pods

Tomei 260/260 Poncams 9.15mm

Tomei Adjustable cam gears

For $2k, a beefer mid range with 38kw gained in the top end... money very well spent in my case

In terms of cam timing settings, we ended up with 2 degrees advanced on the exhaust side, with the intake still set to 0... He spent four hours in it trying different things (I'm happy to pay costs when it comes to this kinda stuff, but he looks after me anyway...) and in the end this was the best combination. I know he definitely tried a lot of settings, but as I was in a rush (my tuner lives over the other side of the city and my car isn't fun in peak hour traffic) so can't tell you exact combinations. I was surprised to hear this setting worked best anyway, I expected the exhaust to be retarted at least a few degrees. I suspect that might be why I've gained mid-range and top end.. not sure Car isn't lumpy on idle, but sounds a lot nicer. On a side note, if I look at djr81's PDF, I've got less midrange than all of them. Wonder if my car is average or something weird is going on there

Edited January 24, 2008 by TommO

[rev210]

Mods:

Apexi Power FC

Greddy E0-1 boost controller

660cc Nismo injectors

Nismo Fuel Regulator

Bosch 044 fuel pump

Turbo back Fujitsubo Exhaust

Garrett 2860r -5 turbos (3 months old)

RB25 AFMs

Apexi Pods

Tomei 260/260 Poncams 9.15mm

Tomei Adjustable cam gears

For $2k, a beefer mid range with 38kw gained in the top end... money very well spent in my case

In terms of cam timing settings, we ended up with 2 degrees advanced on the exhaust side, with the intake still set to 0... He spent four hours in it trying different things (I'm happy to pay costs when it comes to this kinda stuff, but he looks after me anyway...) and in the end this was the best combination. I know he definitely tried a lot of settings, but as I was in a rush (my tuner lives over the other side of the city and my car isn't fun in peak hour traffic) so can't tell you exact combinations. I was surprised to hear this setting worked best anyway, I expected the exhaust to be retarted at least a few degrees. I suspect that might be why I've gained mid-range and top end.. not sure Car isn't lumpy on idle, but sounds a lot nicer. On a side note, if I look at djr81's PDF, I've got less midrange than all of them. Wonder if my car is average or something weird is going on there

You have certainly improved over the stock cams everywhere on an apples for apples comparison.

I seem to recall I began with more radical timing combos and worked back. With the stock turbos I had some info on where to start with the timing.

Sometimes a tuner will assume you want a glorious top end and if at any point they adjust the cam and top end disapears they adjust the cam back, naturally. This isn't right. I do seem to remember you do that to chase earlier spool then on the other gear you change the adjustments and you find the power again.

The basics I use to try and work it out (my reasons for things may be wrong but, seemed to work for me at the time)

* Advancing the intake cam moves the valve closer to the piston (be careful- not too far) and as a result you get increased cranking compression. You end up with better bottom end power. The peak magnitude of power changes is centred around really the peak of the hill (one spot) but, kind of moves the whole hill under it. You advance and generally the power peak moves down the rpm range, to a point. I think you find due to the relation to cranking compression , things like turbos airflow/boost characteristics make it slightly more tricky and effect which way you go from 0 -or+ and how far.

* Retarding the exhaust cam moves the valve closer to the piston (be careful not too far) it tends to effect power more generally over the entire curve. But to less magnitude than the intake changes do. The exhaust cam setting is more of a mystery sometimes advanced sometimes retard.

* Tune at an initial boost a little lower than you want to end up at. Tune for increased boost later.

* Dial in and advance/ retard intake cam first , then the exhaust cam.

* I think the idea with the bigger tomei cams , is 'not' to assume they need more overlap like the stockers 2+adv and -4/-6 exh, they have bigger overlap out of the box anyway. Thats why I think the stock cams need help and they are too small. being designed with some sort of emissions in mind compromises them in this way.

graph wise;

You have less bottom end on the graph because I think he ran those graphs as power runs and probably loaded the motor up a little later in the rpm range.

0 is a little strange for the intake cam timing but, perhaps there was a desire to leave the peak power bump in the same spot as the original.

Edited January 24, 2008 by rev210

[TommO]

Good post, thanks for the information. Considering I use my car for drags and street driving (through national parks etc), I'm more concerned about mid range and top end. If I change at 8k I always end up above 5k so the power graph of my car is perfect. I imagine on a tighter track it might not work so well as it wouldn't have the pull from the lower RPM (I imagine it's often hard to keep the car above 4500rpm), but it's good enough for the moment and not that laggy. I'd love to go for a spin in a GT-SS GTR.... My tuner reckons these turbos (2860-5s) would be brilliant on a high comp motor but in the current form they do pretty average. Not many other twins out there I can run to achieve more low-mid range without sacrificing top end, unless I look at converting to a single turbo.

Either way, took the car for a run tonight and it goes great... feels just as fast but a hell of a lot smoother. I recommend this mod to anyone running upgraded turbo/s.