Gt2860r -5

[RPMGTR]

I'm really keen to see some 'stock cams' graphs with the benifits. It's certainly a different way of looking at the traditional and I'd love to know how it's supposed to work.

Herein lies the problem.......

Are we racing dynos or cars??

For a few years now , the dyno (ours included) has said that the cammed cars make a slightly better power graph.

However our experience has 'found' that the cars go FASTER with std cams on these little turbos.

And its interesting when you reverse engineer these things (take them out) and don't immediately tell the owner.

You get a response like "I don't know what you did but it feels great and I improved my PB"....

So I guess at the end of the day its a little subjective hence the differences of opinion.

cheers

[R31Nismoid]

Tekin - if your going down the line of why a commercial company out there to make money... offers parts other than standard, i think you've failed to see the whole point of the discussion here.

Its like saying why do companies make Neons, 100dB and 90dB exhausts....

Its all about offering a product range that makes money, doesnt mean it offers benefits over and above something else at all.

I think its sorted though, dynos or cars - dynos for you, cars for the others

[djr81]

Problem being is that you need to sit down & assess where in the rpm range you want your torque. Basically do a log of the % of time spent in various rpm ranges at 100% TPS. Then graph it. Then use that to determine whether or not after market cams are for you. The larger units (relative to stock) struggle at around 4000rpm which coincides to alot of corner apexes around the country.

Anyway the track versus dyno thing is just another way of saying your turbo motor sucks going down hill....which they do.

[archie01]

...if stock cams where the best for GTR's...why would we have so many different after market ones to choose from.All that time and money from HKS, Tomie, etc etc..is it all a waste.????????.lol

I think you can email them now...let them know..Racepace has decided this and thus it it true.

My statement stands....

The -5's and -7's are small turbos and are very similar to the stock items and as a consequence it has been found that running standard cams provides better response and power on pump fuel (not talking race fuel here).

Bigger turbo's (GTRS's, single TO4z on an rb26 for example) will definitely benefit from bigger cams ie will make more power compared to standard cams, however the -5's and -7's don't seem to respond as well.

The aftermarket (HKS, Tomei etc) is catering for the 'bigger turbo' instances.

[djr81]

The -5's and -7's are small turbos and are very similar to the stock items and as a consequence it has been found that running standard cams provides better response and power on pump fuel (not talking race fuel here).

Bigger turbo's (GTRS's, single TO4z on an rb26 for example) will definitely benefit from bigger cams ie will make more power compared to standard cams, however the -5's and -7's don't seem to respond as well.

The aftermarket (HKS, Tomei etc) is catering for the 'bigger turbo' instances.

A dash five small?

Depends on what you consider to be small, I suppose.

One of these things will flow just over 35lb/min of air. So two of them will happilly give you 700hp, or over 525rwhp without any fancy fuel or much other bullshit.

My set up has 260 degree cams with these turbos. Turned down to 15# (& I mean turned down) it makes good torque all the way to redline.

The upside of the larger cams is less heat through the engine....

[tacker]

We did a track mapping Vs Rpm and found that the high % engine RPM was firmly planted above 4.3k RPM. Which is due to circuit lay out, and most circuits here are F1 standard so not to many tight corners to worry about. I guess in a track only type car we hope to see better performance higher up in the rev range. Also the amount of head work the builder was very keen to see some bigger lumps involved.

[700HP-GTR33]

Tekin - if your going down the line of why a commercial company out there to make money... offers parts other than standard, i think you've failed to see the whole point of the discussion here.

Its like saying why do companies make Neons, 100dB and 90dB exhausts....

Its all about offering a product range that makes money, doesnt mean it offers benefits over and above something else at all.

I think its sorted though, dynos or cars - dynos for you, cars for the others

Ash- It has always been great discussing topics like this one with you over the few years I have been a member.

Yes...creating parts for the after market is what makes money for most of these companies.

But in most cases it is justified....take the- stock brakes on a GTR..great but need better for the track...Pads and Discs.

- stock Turbo's on a GTR..great but need some help getting past the line in 13 seconds.

- stock exhaust on a GTR..great but a little restrictive

- stock fuel pump..............great but can't pump too much..especially if you want a great tune.

- can I mention the clutch...5 drops at 6K and the organic crap disappears

ETC ETC ETC.............

Nissan made a car for the people.....in stock form they though it would be adequate for the mass public.

Then N1 improved all aspects to create a race car.....N1AFM,N1Fuel Pump,N1 Block,N1 Pistons,N1 Clutch. N1 Fuel pump..

ETC ETC ETC..............

It is not Dyno figures I seek...KW's mean nothing when a Freight train does not kick in with it.

Cams give you lots of Torque...that is my argument.

And yes..I like to see a bit of rocking when I pull up at the lights.

[700HP-GTR33]

The -5's and -7's are small turbos and are very similar to the stock items and as a consequence it has been found that running standard cams provides better response and power on pump fuel (not talking race fuel here).

Bigger turbo's (GTRS's, single TO4z on an rb26 for example) will definitely benefit from bigger cams ie will make more power compared to standard cams, however the -5's and -7's don't seem to respond as well.

The aftermarket (HKS, Tomei etc) is catering for the 'bigger turbo' instances.

You have confused the -5's with the -9's

GTRS and -5's have the same housing.....just different turbines'

[R31Nismoid]

In some cases - not all, certainly not most.

Lets get back to turbos and cams ye?

Rather than 11ty other things that mean nothing and offer nothing to the discussion here - to which has pretty much been covered i think

RPMGTR builds the cars, archie01 is one of the many.

Good enough for me in the real world

[JAGR33]

My advice is to change to bigger cams unless your mechanic/tuner/dude that makes your car go faster says otherwise.

I had 260 poncams with my -5's, now I don't...

[Snowman]

My advice is to change to bigger cams unless your mechanic/tuner/dude that makes your car go faster says otherwise.

I had 260 poncams with my -5's, now I don't...

Thats pretty much what I said. Sure there are guys like myself, JagR33, archie01, Soctsman, Aaron34, JFKGTR, RPMZ, etc etc (even R31Nismoid if his car ever see's the road again) all with better results on either -7's or -5's with standard cams in an RB26 - but we've all got the same guy with his own secret little tricks that get them to work the way they do.

My old experience with the poncams was that the beauty of them was all you had to do was fit them and set the cam gears to 0 and you has some pretty damn good results for very minimal effort. So unless you have someone that knows the secret little tricks you are going to get better results easier with poncams there's no question.

[donkey]

holly shit that was some sweet debating.....nice one

Edited May 10, 2008 by donkey

[rev210]

Herein lies the problem.......

Are we racing dynos or cars??

For a few years now , the dyno (ours included) has said that the cammed cars make a slightly better power graph.

However our experience has 'found' that the cars go FASTER with std cams on these little turbos.

And its interesting when you reverse engineer these things (take them out) and don't immediately tell the owner.

You get a response like "I don't know what you did but it feels great and I improved my PB"....

So I guess at the end of the day its a little subjective hence the differences of opinion.

cheers

Thats actually fair enough, I was thinking there was some dyno's around showing the changes. In practice though you are most likely finishing the tune off at the track anyway as you would. Who cares about the dyno numbers if you are losing races

Really the dyno does it's best to simulate a road going condition but, since you can't simulate accurately a bunch of conditions at speed on the track, you are best off bunging a wideband in and logging/changing away.

I suppose I am struggling to understand why the small standard cams would work better. Would like to get some insight though.

Perhaps the cars in question have built motors with flow restictions removed elsewhere in the head? It's certainly true that a higher flowing valve needs less time open to achieve the same volume so maybe there is some sort of wierd pulse frequency thingo going on?

[rev210]

My old experience with the poncams was that the beauty of them was all you had to do was fit them and set the cam gears to 0 and you has some pretty damn good results for very minimal effort. So unless you have someone that knows the secret little tricks you are going to get better results easier with poncams there's no question.

I think your experience is like lots of others on the forum. Cam's are a bit of a mystery. The setting to '0' assumption on the tomei's is common and basically on a GTR a bad one, I've found it to be quite wrong. The assumption seems like it comes from the belief that cams are a cheap mod or at least only as expensive as buying a couple and bunging them in with a slight tune. But, adjustment can take awhile to get perfect.

When I came to these skyline forums I noticed there was a distinct lack of knowledge about cams and how to set them up, I think there has been alot of change since but, there really isn't much understanding in the average skyline punter about the whys and hows of cams (ok so we aren't all mechanics or misguided car-wrecking idiots like myself).

The irony is that I reckon the RB head/cam setup is so easy to tune by comparison to the other abominations I've setup over the years (although I leave room for the idea that I have no idea what I am doing if the stock cam thing is right). I did a cam road tune (adjustable gears) on a young lads skyline today and it took bugger all time to get sweet (not assuming cam timing either). On the other hand helping a mate with his worked up red motor EH was an excersise in me saying at least 50 times 'you know this would have been so much faster if you just dropped an RB in here, it will fit you know...'

The thing is even I can setup a set of tomei's or standard cams to work as well as they can using the same basic theory and experience from other types of motors. And I am as dodgy as you get I got bucket loads of power out of the tomei's over stocker cams with some mucking around and the car was an absolute weapon to drive compared to a GTR with stock cams adjusted well, with more boost and harder tune.

I think your experience with the -5's and stock cams is really valuable to the forum but, for me being the meddling idiot I just want to find out how

Edited May 10, 2008 by rev210

[zebra]

My Understanding of it all, is that Smaller cams i.e Less lift and Less Duration will make more torque than larger cams more lift and duration, which are aimed at high rpm power.

Torque accerates a Vehicle,

Also as a thought while im thinking about cams.

Do the Japanese Measure their cam duration at .050 thou Lift (when the valve has lifted off the seat enough to actually flow air) or do they just measure total lobe duration to make their product sound cool to the masses.

Lobe Ramp rates have a lot to do with how a cam performs as well, To Sudden a movement Will Kill Gas Velocity, while too slow creates a restriction in the port, Cam Overlap affects Dynamic Compression aka True compression, True compression doesnt start untill both inlet and exhaust valves are seated which may explain why people are getting better results with standard cams over larger aftermarket ones.

Ive noticed there is bugger all technical info on Jap Cams so its almost impossible to choose a set to suit a set up, Take a look through an American Cam manufacturer's listing for cams theye give heaps more specs on the cams and what they're suited for, with the jap ones its look through a magazine and find a car that makes BS horsepower and copy what they have done.

Everything can affect what cam to choose - Intake Runners, Head work, valve size, target peak power and torque RPM's < probly the biggest factor in choosing a cam.

If I change cams in my car (RB25) Ill get custom ground ones over anything ive seen avaliable off the shelf.

Soz for the long post, Its Saturday and Im staying In :-/

Regards

Andrew

[rob82]

I think Zebra has hit the nail on the head. Smaller duration camshafts have better dynamic compression and there is no better mechanical way of getting a turbo to spool than compression - hence incresing torque and throttle response. The other advantage/disadvantage of the 26 is that it has a tiny stroke and rod length so the it lends itself to being reved and not hanging around at TDC for too long this is why the timing numbers are so large even at large boost levels.

With the -5 there really is that much more power to be made above about 22-24psi of boost on a standard displacment 26 and at those boost levels on standard cams I've seen up to 16deg total advance which to me is just perfect.

[donkey]

as much as i learn so much from these forums, sometimes i walk away trying to figure out what advice to follow? standard cams on the -5 or aftermarket ones?....haha

Edited May 11, 2008 by donkey

[rev210]

I think Zebra has hit the nail on the head. Smaller duration camshafts have better dynamic compression and there is no better mechanical way of getting a turbo to spool than compression - hence incresing torque and throttle response. The other advantage/disadvantage of the 26 is that it has a tiny stroke and rod length so the it lends itself to being reved and not hanging around at TDC for too long this is why the timing numbers are so large even at large boost levels.

With the -5 there really is that much more power to be made above about 22-24psi of boost on a standard displacment 26 and at those boost levels on standard cams I've seen up to 16deg total advance which to me is just perfect.

I think it must be something other than the compression idea, as advancing the intake cam timing and does this along with higher lift. The tomei 9mm lift units smack the standard cams for cranking compression and they smack them very hard, so it's probably something else.

I wouldn't mind having a crack at the standard cams again but, I can't really see a reason to do so given my experience so far is when setup correctly the tomei's maul them everywhere. I'll probably only try if someone can give me some timing points to try and some reasons why to try them . I admit I am being a bit cheeky in asking for what might be a 'secret'