Understand Correct Cam Choice

[cobrAA]

baron, your talking about big cams but poncams ain't really big cams.. very mild cams compared to others.

[Kaido_RR]

That is exactly my point! And the same point a number of others have had (Marlin, djr82 etc etc).

Over Kaido's threads (there is a massive one in MSport), it's just about him buying parts without any thought or experience.

He is building a track/circuit/club GTR. The best thing initially it get it reliable, which he has done with oil cooler/turbo swap and so on.

The next part now is to stop worrying about spending money and go and drive the car. Learn it, talk to others @ club days to see what makes their car fast. Workout what they have tried/have not tried.

I think that's the best advice - and best of all, it's free!!!!

I'm not having a go at him or anything like that, I just think it's very silly to be talking about spending thousands of dollars without even knowing how to drive the car fast at this stage. It's the same thing many have been saying for 6 months now.

I'm in a similar boat. The GTR I've purchased has very similar spec/proven formula to many other cars and at a recent hillclimb i was 8 seconds slower (over 60 sec lap).

It's not setup slow - its driver slow. It'll take me many sessions to knock off those 8 seconds. I will get there eventually but it won't be by spending $1,000's on parts i don't need. It's simply experience which costs nothing but holds the most value

Nismoid if you read my 1st post, i said its highly likely that my head will need to come off. This is the only reason why i have been looking into cams. i'm very happy with the engine and power level and have no real plan to do anything engine wise. However if the head must come off for other reason i see it as a good times to look at upgrading the head (port/flow, cams etc)

If you look at the list of mods on my car its far from $$$$, its pretty much all just bolts on gear, yes all of it is name brand jdm gear however i never paid full price.

I have been driving the car at the track however, last track day i hit some reliability issue which i am trying to fix atm which may required the head to come off.

And yes i have had chats with 2 of the faster gtr runners here in perth. one pretty much said i needed all the big dollars gear if i wanted to run his sort of lap times (sub 55sec)

djr81, i'm just trying to build all rounded car yes i like doing track day @ Wanneroo, but their is plan to run rally-sprints, speed-event series.

So its a toss up between keeping top end but also not losing too much in the lower rpm range too.

[djr81]

Nismoid if you read my 1st post, i said its highly likely that my head will need to come off. This is the only reason why i have been looking into cams. i'm very happy with the engine and power level and have no real plan to do anything engine wise. However if the head must come off for other reason i see it as a good times to look at upgrading the head (port/flow, cams etc)

If you look at the list of mods on my car its far from $$$$, its pretty much all just bolts on gear, yes all of it is name brand jdm gear however i never paid full price.

I have been driving the car at the track however, last track day i hit some reliability issue which i am trying to fix atm which may required the head to come off.

And yes i have had chats with 2 of the faster gtr runners here in perth. one pretty much said i needed all the big dollars gear if i wanted to run his sort of lap times (sub 55sec)

djr81, i'm just trying to build all rounded car yes i like doing track day @ Wanneroo, but their is plan to run rally-sprints, speed-event series.

So its a toss up between keeping top end but also not losing too much in the lower rpm range too.

Then for what it is worth just leave the stock cams in it for now. Focus on making the car reliable, handle well and be (relatively) cheap to run. Sub 55's wont win anything much anyway so just go have a go.

As for running in stuff to give you an idea the last Speed Event Sprint at Collie a couple weeks ago - there were only 3 R32 GTRs entered - mine and a couple others. To be honest the cars are more different than they are similar. The Speed Aware Rally sprint at the boganplex a few weeks back had others that were different again.

How you want your car to finish is up to you but understand that you will never actually finish & that there is no one right solution. I have been doing the SES for 6 or so years now & it is rare that my car is the same two events in a row. Some times the mods work, sometimes (like last time) they dont. Or they only half work. But that is part of the fun - figuring out how to go quicker then going your hardest to find out if you are correct or not.

Sub 55 on the short circuit is a pharken good time. It takes alot of work to get to those times even if you have massive rwhp numbers. You cant just bolt stuff on & go bang there is a 54.5. It doesnt work like that.

Edited March 16, 2011 by djr81

[Beer Baron]

baron, your talking about big cams but poncams ain't really big cams.. very mild cams compared to others.

I am talking about pon-cams? see the bit in my post where I say "pon-cams". the other cams are not 'really big cams' either. the HKS cams were smaller than type B pon cams at (from memory) 256 degrees duration and around 9mm lift. midori cams about the same size as well. I've also used N1 cams, but they are sort of a step between standard cams and pon cams at 248 degrees duration.

everything i said is from my own experience and I can promise you for this application the best bet is fit some cam gears and tune them. as I said there is no need to remove the head to fit cams so saying you'll do it now while the head is off is not really going to save you any money at all. the smart option is try the cam gears first. it's no risk as if you don't like it and do eventually get cams you can still use them to set up the new cams. all you will have lost is $200 or $300 in dyno time for the initial setup time

[R31Nismoid]

Kaido, i know what you said but as the above posts say... You really aren't going to save money. Can be done with the head on and cost isn't majorly different.

The two posts above hit the ole nail perfectly and would be what id say.

Just remember cams is 1500 fitted/tuned. cam gears less than half

Good to see you are getting out among it, let your R&D begin

[NSNPWR]

Im curious as to where people put their adj gears with stock cams as when I fit my Poncams (car already had Tomei gears) I noticed the only gear moved was the Inlet and it was only by around 1deg...I know the car had been through a number of QLD tuners before I bought it so im wondering if there is actually that much to be had from adj gears on stock cams? As it was, car made 270rwkw with -7s on just under 1bar.

...And as long as you have basic mechanical knowledge, cams are so easy to fit yourself its not funny

Edited March 16, 2011 by NSNPWR

[djr81]

Im curious as to where people put their adj gears with stock cams as when I fit my Poncams (car already had Tomei gears) I noticed the only gear moved was the Inlet and it was only by around 1deg...I know the car had been through a number of QLD tuners before I bought it so im wondering if there is actually that much to be had from adj gears on stock cams? As it was, car made 270rwkw with -7s on just under 1bar.

Stock cams gain from more overlap ie advance the inlet & retard the exhaust. Aftermarket cams less so. The difference is aftermarket cam manufacturers didnt ever have to care about emissions compliance.

...And as long as you have basic mechanical knowledge, cams are so easy to fit yourself its not funny

RB26 cams are harder because they have to be shimmed.

[NSNPWR]

Poncams are a drop in?

[Shane_954]

Valve clearances need to be set by shim adjustment.

[MrStabby]

I've also used N1 cams, but they are sort of a step between standard cams and pon cams at 248 degrees duration.

Sorry for the hijack - but Baron do you have the rest of the N1 specs (exh duration, intake and exh lift?)

[Simonster]

Ive recently seen something that has turned my knowledge of cams on its head. I saw a 90hp gain at a specific rpm on a 2.6GTR with -5's. It was a really course adjustment- the limit of what the cam timing would allow. I didn't believe it, the tuner couldn't either, but there it is. It was around the 90km/h in 4th gear, adjusting the inlet only, ex was set on zero still.

[R31Nismoid]

stock or aftermarket you mean?

What happened to the rest of the rpm?

70kw is a bit stretch. you'd wonder if initially timing was incorrect and so on leading to such a gain when settings are adjusted.

Such gains in that type of scenario have a reasonable probability for sure.

[Beer Baron]

there must have been something massively wrong to gain that much from just inlet cam timing adjustment. normally you can gain around 30kw at the point you mentioned but most of that gain is in retarding the exhaust cam a bit and advancing the inlet gives about 10kw of those 30.

mr stabby, I will have a look for you. i have them somewhere. from memory inlet is same as regular GTR cams (though this has been debated) and exhaust has more duration (248 degree from memory). I still have a pair of N1 cams hear that I took out of my nur motor (they are brand new) when I put tomei cams in it.

[MrStabby]

mr stabby, I will have a look for you. i have them somewhere. from memory inlet is same as regular GTR cams (though this has been debated) and exhaust has more duration (248 degree from memory). I still have a pair of N1 cams hear that I took out of my nur motor (they are brand new) when I put tomei cams in it.

Thanks - I have found it difficult to get specs, but is sounds like it could be;

Inlet Duration: 240 std, 240 N1

Inlet Lift: 8.58mm std, ? N1

Exh. Duration: 236 std, 248 N1

Exh. Lift: 8.28mm std, ? N1

Do you know if N1 cams respond less to cam tuning? CRD found cam adjustment didnt make much difference on my car. I have a 24U block, N1 water pump, higher that stock oil pump flow, and an 8500rpm redline so i'm assuming its an N1 motor.

[NSNPWR]

Valve clearances need to be set by shim adjustment.

I know of more than one example with the Tomei cams where this has not been the case...with my motor in particular, the clearances were adjusted for the factory cams when the motor was rebuilt, its my understanding that the Tomei cams share the same base circle as the stockers? 32mm?

[wolverine]

I know people who have installed them without re-shimming.

Likewise it doesn't mean they are at Tomei spec.

[Beer Baron]

yes they are the same base circle as standard cams but that doesn't mean you wont need to re-shim the valve clearances when installing. re-setting valve clearances is a maintenance item which should be checked and done periodically. sadly not many do it. so quite often when replacing your cams it's past due and needs to be done (or should be done at least).

mrstabby. what you have seems correct. I think lift might be the same between standard and N1. maybe a little more lift on the exhaust side. with a longer duration ex cam overlap is increased a bit so yes it would mean less gain from cam gears as that is effectively what you're doing with cam gears.

[T04GTR]

for a general rule of thumb. on a n/a motor. more lift = more power. the duration simply moves the power band around.

with turbo. you want more lift and more duration if you are using smallish turbos. the boost will fill in the hole left by the larger duration..

with a larger turbo you would tend to do the same thing.. but this does make the power delivery more abrupt.

in my experiance a "safe" choice is no more than 270 degree with as much lift as possible.

if you are going to race it. a larger cam is better. unless you putt around at 3000rpm. in which case you should sell it and get a v8

with cam gears it up to the tuner to make them suit the turbo set you have.

ex back pressure has a large efect with big cams as there is generaly more overlap in which exhaust gasses are forced back into the combustion chamber at the moment there is overlap.

alot of these little t28 sized turbines can have as much as 2:1 back pressure so if youve got 20 psi boost. you will have 40psi in the exhaust manifold. so for that short time there is efectivly 20psi boosting its way back into the engine.

this can stop power production, this can be seen when more and more boost is added yet the power starts tapering off.

also can be seen as black soot evident in the inlet ports.