Tomei Poncams Installed ! Hmmm power...

[rev210]

Just installed a set of Tomei 260deg 9.15mm lift cams into the old aussi R32 GTR today. What a difference!

I have dialed them in at 0 deg to start.There is a little bit more growl in the idle

and once the accellerator is fed at any rev over 3000rpm there is an awsome responce improvement over factory.

I have to say installing GTR cams is pretty easy. Having said that mine were R34 cams and I had to modify the CAS input to suit the exhaust cam's key (easy, sort of).This is also a way of instantly knowing if you have R34GTR cams when trying to do a Rb20 cam upgrade (basically without a modified CAS you can't use a set of R34GTR units).The great thing is the Tomei Poncams don't need any shims !!!!

Have yet to dyno ( I have a power FC pro waiting to go in) but It will be interesting to see the torque improvement considering I have factory turbos and most don't bother doing cams untill they upgrade everthing else.

If anyone 'has' installed these cams on factory turbo equiped Rb26dett then I'd be interested in the results.

BTW I will have a pair of factory R32 GTR cams and gears for sale soon

[GTS-t VSPEC]

Well done Dave, be nice to see what difference it makes on the dyno:D Will be putting a set of cams into my RB25 soon, so I hope I get similar gains:D

[rev210]

Paul,

It's a shame I missed the dyno day on sunday. I only just finished on the sunday night. I thought two afternoons of work was pretty good going by myself in the dodgy dave shed workshop .I did have the dyno comp in the back of my mind.

I think the gains will be quite substancial in your case. I have only got standard turbo's and you can still tell the decrease in restiction at the valves is huge at even modest rpm and throttle.

[Abo Bob]

Do you get any extra vibration at idle or did you up the idle rpm to compensate?

[GTS-t VSPEC]

Dave, Never mind, no point rushing something to fit into a Comp. I'm hoping on gaining a reasonable amount in the mid-range, only problem is the hydraulic lifters restrict me to lowish lift, but still got to be better than stock.

[lukevl]

Did they say not to modify the shims? I take it you checked them and they were all within spec?

[Trust33]

yes is the stock valve train up to the task with poncams on an rb25...What should be looked at??

[rev210]

Did they say not to modify the shims? I take it you checked them and they were all within spec?

They don't say anything on the Tomei website about not checking the clearence. However the base circle is exactly the same as factory on these cams, so if you didn't need shims before you wont after installing the new Tomei Poncams. This is what they suggest by the 'no shims required'. I think in most cases if the camshaft has been worn you need to re-shim, for the worn camshaft. Put a new one in with the same base circle as factory new and it won't need any shims.

Abo Bob,

There is a slight lump on idle due to the overlap. Induction/exhaust noise is increased. Having said that a new ignition map will help. I have a factory ecu with a spare PFC Pro waiting to go in shortly.

[Trust33]

good luck rev210.....are the adj cam gears in your opinion absolutly nessesary as i heard that there was not all that much more power to be coaxed from the rb 25 after it has cams installed,meaning that the adj cam gears dont do all that much in th eway of making power because the lift and duration are meant to be perfect..Which i tend not to beleive.

How can an adj cam gear not create a wider power band?

My only theory is that it can create too much overlap resulting in a piston meeting the vave....Correct me if im wrong...

[nitemare5]

i think in the case of the tomei poncams, sydneykid said that cam gears aren't necessary because tomei got the timing spot on. In the case of having normal cams in the rb25, cam gears in the series 1 rb25dets alot of ppl have seen nice improvements.

[Amaru]

Induction/exhaust noise is increased.

On a different note to most of the questions in here, how much is exhaust noise increased be? I take it this is on idle and while driving?

[rev210]

good luck rev210.....are the adj cam gears in your opinion absolutly nessesary as i heard that there was not all that much more power to be coaxed from the rb 25 after it has cams installed,meaning that the adj cam gears dont do all that much in th eway of making power because the lift and duration are meant to be perfect..Which i tend not to beleive.

How can an adj cam gear not create a wider power band?

My only theory is that it can create too much overlap resulting in a piston meeting the vave....Correct me if im wrong...

The cam gears are a must have on a modified engine with these cams. (I have an R32 GTR). The reason for this is that every engine combo is different and depending on application the timing of the cams can be made to affect the engine performance greatly. The 260deg 9.15mm lift Poncams have been known to make more horsepower at 10deg advance for intake 8 advance for exhaust cam on a particular car/engine, with better all round characteristics. Doing the same on my car would not necessarily be as wise considering the smaller turbos (and turbines) I have and more restrictive exhaust setup. If you are serious about 'tuning' the car then the 'bolt on boy' approach must be thrown out.

If you are a cheap arse and want to go without the adjustable cam gears you can. Take off the timing belt every time you want to change the cam shaft timing and dial it in with a large protractor. It's just much more time consuming to try out new cam timings then a simple losening of a few allen key bolts on adjustable gears.

[rev210]

The extra exhaust noise is not that bad at all, lots more air going in and gas going out always makes a little more noise.

At idle it growls with a little lump. At cruise there is very little difference if any. At decent throttle there is more induction noise and a louder deeper exhaust note, nothing over the top.

[600hp]

i ran the standard turbos with 260/9.15 tomie cams.the mods were as follows.

stainless manifolds

dump pipes

twin 2.5 inch into 3 inch exhaust

nismo twin plate

power fc

trust 100mm intercooler

hks air filters

that was it at the time the car just hammered!

we had a drag Vs another 33 gtr which had cat back boost up and intercooler we were running up to .9 bar

anyway we completely smashed him blew him away.

the car is going in at the end of the week to see how much power we can get at 15 PSI i'm hopeing 270awkw.we'll see.

[lukevl]

Even if the base circle is the same that doesn't mean the clearances should be the same. The profile determines what clearances to run and what shims to use. Plus when you measure the base circle you are measuring part of the ramps so you can't tell what the base circle is. Perhaps Tomei copied Nissan ramps perfectly. maybe... But its still hard to get a consistant enough finish to justify no ramps.

Also with mechanical cammed motors, over time the cam doesnt' wear, instead it pulls the valves back through the cylinder head and the clearance grows which makes the valves seat harder and the process doesn't stop. Thats why clearances must be checked regularly.

I would check them to make sure if I were you. All the compenents we are talking about aren't as consistant in machining and setup as you may think.

[rev210]

lukevl,

Good info mate. I must admit it's great having people in the camshaft biz on the forums. I did check the clearences on the new cam and it was within the factory range, so it's all good.

The Tomei cams are finished very well indeed. By comparison they looked much better than the HKS 264 9mm lift cam I had purchased some time ago for the Rb25 powered R33 gtst. They appear to be a 'billet', whereas the HKS units looked to me like regrinds. There seems to be quite alot of people I have spoken to who have found the Tomei 260deg 9.15mm lift cams drop straight in without shims (the guys I spoke to measured the clearences to make sure too). On the other hand the HKS units even at 8.7mm lift have sometimes required slight head machining on supposedly "step 1's" with a nice compliment of shims.

It seems the Tomei guys may have done a pretty good job of replicating the nissan ramps.

Cheers

Dave

[GTS-t VSPEC]

I have Apexi cams coming, I hope there as well designed as the TOMEI ones.

[rev210]

Paul,

You don't have solid lifters so if it doesn't need head machining then it's too easy. Whats the lift and duration on those?

Dave.

[GTS-t VSPEC]

Because they use hydraulics the lift isn't as aggressive as you get with solid lifters, but there the biggest I could find. 270duration 8.9mm lift. Shouldn't require any machining, and we're just putting a set of performance valve springs in to cope with high revs, 8.5k:D

[rev210]

Dude thats very large duration.

Have you got enough room in your exhaust pipe for all that gas?

What rpm is your peak power being made at now?