Which Camshaft For Responsive 2.9L Bc Stroker?

[HarrisRacing]

I am building my R32 (build thread on this website under that section), and have ordered the Brian Crower 2.9L stroker setup for it. So far I have all of the oiling mods (including Tomei oil pump), and am gonig with 86.5mm bores with CP 8.5:1 pistons. I also jumped the gun and ordered some GT2860-7 turbos since they were on sale when I was initially ordering things for my car before I knew the stock 2.6L crank was bad. I will likely run these turbos for a year or so and then go straight to a single turbo setup BW EFR 7670 or BW EFR 8374.

I am wondering which cams I should go with that may possibly cover both setups or if I should just go stock now and a larger set later.

What do you guys think about Tomei Type A poncams? type B? BC offerings?

Those with actual 2.8 or 2.9l stroker builds please chime in. I have searched through the dyno databases and haven't found a solid comparable setup yet.

Thank You

Patrick

[GTSBoy]

I think the general concensus is that neither of the poncam choices really offer anything worthwhile. Big cams and "responsive" are not really directly related anyway. If you were to fit the poncams and wanted to enhance responsiveness you'd pretty much have to be looking at adjustable cam gears anyway, and setting the overlap to make them work better at the lower end of the rev range.

Now, you could do that with your stock cams anyway. Keep that in mind.

The other thing is....if the chances are that your turbos are not really going to be large enough to keep up with the stroker, or at least are going to be pushed towards their limits, then you probably don't really need to add any extra breathing ability to the engine.

If it were me, I would build it with the stockers and get it set up. See what you get. If it looks like you should be able to lean on the turbos and you want more power, then it isn't hard to slip cams in (unless you go large enough to need to make changes to the head.) On that note, you might look at what else you could do with the money that you might spend on cams and gears in the head area. You could look at making the necessary preparations to accept high lift cams (springs, retainer upgrades, reliefs, etc), and maybe even some light duty port cleanup or something. Things that will make the engine better (even if they don't all enhance power now) but will make it easier to get bigger cams into it later should you go down that path with the bigger turbo.

And seriously ask BC what cams they recommend to go with a 2.9 kit.

[r32-25t]

For response you want low duration 250-260° with as much lift as you can get, in my rb30 I used a jun 264 with 10.5mm of lift and it sounded like a factory idle.

Piggaz is using a 260 with 10.8mm but wants to try a 250 and his car is 2.8L

But with -7s you may as well leave the factory cams in it cause they will won't flow real high into the rev range anyway

[Piggaz]

Don't use a drop in cam if you're going to all that effort of building a stroker engine. That's like mixing everything for a cake, putting it in the baking dish and not turning the oven on!

As Brett said, something with not much duration and big lift. My tuner and myself went through this a few years ago. We spun up a JUN. 264 @ 10.5 and a Tomei 270@ 10.25 and found the ramp rates to be very very mild.... So we made our own which was actually a Alfa Romeo NA Lobe and stuck them onto RB sticks. 260 @ 10.85 mm. ( they also use stock buckets) Don't forget, you'll need a decent valve spring with cams with agro ramp rates.

There are a few VQ lobes which are of interest. One is a 248 @ 10.56 mm iirc. Can always try and get that lobe put on an RB stick.

[Piggaz]

http://www.mines-wave.com/english/CATALOG/ENGINE/CAMSHAFT_SHORE.htm

Check these out. 252 at 10.05mm.

[HarrisRacing]

Doing a bit of research online shows the following:

Description, Advertised Duration (IN/EX), duration at .050" (IN/EX), max lift (mm) (IN/EX)

Stock, 256/256, 209/206, 8.51/8.18

Poncam R, 250/250, 216/218, 9.15/9.15

Poncam A, 260/252, 222/214, 9.15/9.15

Poncam B, 260/260, 222/224, 9.15/9.15 (uses exact same intake cam as Poncam A but longer duration exhaust cam).

BC Stage2, 264/264, 222/224, 9.14/9.19

Honestly I have a hard time believing that there would be little difference in powerband between these cams and stock cams. All gain 0.64mm of intake lift and ~1mm of exhaust lift, all gain at least 7 deg on intake and exhaust at .050". It also shows that the ramp rates of these are all substantially quicker than stock as the "advertised duration" and "duration at .050" are spread far apart on the stock cam vs. the others on the list. It also tells me that the BC stage2 (only ones I see that they sell for the RB26) are very similar to Poncam B. Note, we didn't get to the "pro" larger lift/duration cams (requiring use of larger springs, etc) yet.

I like how the mine's cams have larger lift and mild duration. Big duration to me often lets boost blow out the cylinders, but the lift helps all around if you get the ramp rates correct.

FYI I will already have stiffer springs in the engine...not sure about titanium retainers yet or not, but at the minimum manley replacement valve springs which have a nice increase over stock seat and @lift spring pressures.

And I think the reason cams get a bad rap is that they are expensive and a lot of work for the HP gains...$2000 in turbos can make FAR more HP than $1000 in cams and springs.

Edited September 7, 2014 by HarrisRacing

[r32-25t]

If you know everything why are you asking for advice?

[HarrisRacing]

Sorry if it sounded like that...just trying to add more data to the pool so I can make a more educated decision. Your input is appreciated greatly.

What I was noticing were things like someone taking a stock or aftermarket camshaft and dialing them in using adjustable cam gears and still making great power increase with NO changes to cam duration or lift whatsoever, but simply changing overlap timing by changing cam timing.

One example is on post #19 of this thread: http://www.sau.com.au/forums/topic/93880-rb26-turbo-upgrade-all-dyno-results/

He makes 17 more KW and greater power everywhere in the curve from just changing cam timing...seems like a lot of power increase from rotating cams and from what I read most people don't move them more than a few degrees apart.

In the list of durations of "bolt in" cams there is clearly more than just 4 degrees of cam timing changes going on and it's leading me to believe that there should be more room in there even on the smaller turbos that I will be running to gain some response from changing out the factory cams and likely even more response when I get them timed right on the dyno.

Edited September 7, 2014 by HarrisRacing

[GTR_JOEY]

Like what Brett and Paul are trying to tell you, its not just about the specs the manufacturer gives you ie duration and lift

Cam lobe aggression plays an important role in how quickly/much air gets into your cylinder.

All these cams you quoted are very mild in terms of lobe design. Do what the guys are saying, either keep your standard cams for your -7s or if your going to change to a big single get the custom cams from UNIGROUP here in Aus.. they re not cheap but why go to the trouble to do a half assed job.

PS cant you micro wave a cake Paul?

[r32-25t]

Cams are easy to explain, lift=Horsepower, duration=rev range, higher the duration the higher the revs required before they start working.

Pon cams don't have enough lift available for the amount of duration and the gains suffer because of it.

[GTR_JOEY]

I have matched these cams with a Ferrea dual valve springs, titanium retainers and locks.. money well spent in my opinion

[GTR_JOEY]

double post

[Piggaz]

Stock duration with 11 mm lift

[Lithium]

Stock duration with 11 mm lift

Barely a month to the day that its going to be a replay of last year - I am looking forward to further discussion on these things. Oh what I wouldn't do for a way of testing things like this along with a bunch of "top" off the shelf alternatives.

[cobrAA]

Thank you for this thread, I was going to ask the same question. Difference is I have a rb26 with 83/74. So you guys reckon the ''PROCAM 260 10.8mm lift'' a better choice versus my Poncam Type-B 260 9.15mm ?? I need to know because I'm bulding the head so I don't care about cam not fitting, we'll work it out.

I thought the lift was what make the idle lumpy and rought ? I guess it's the duration then ?

[GTSBoy]

Stock duration with high lift will idle exactly as stock. Stock lift with 290deg duration will idle like a race car.

Of course, you actually often need extra duration to be able to package more lift onto a lobe, otherwise the ramp rates can become excessive and valve contol becomes difficult. I spent some time designing some cam profiles for my ALFA (that I never got around to trialling) and most of what I wanted wasn't doable - 13mm lift with not much more than 105-248 (the best stock cams) duration.

[XKLABA]

Cams are easy to explain, lift=Horsepower, duration=rev range, higher the duration the higher the revs required before they start working.

260 Pon cams don't have enough lift available for the amount of duration and the gains suffer because of it.

This is the simplest answer to the question

Lift will give torque every where duration will give HP in the top end, top end horse power comes at the cost of low end torque

My car came with 260 poncams I the changed then to 250 poncams and everything happened 800-1000rpm sooner with the same peak power and made the car a lot nicer to drive in the low rpm range for DD

NAs need velocity to get their best which is why long duration cams work for them but turbos need volume which is why high lift works for turbos

My philosophy with turbos is get the cams to take care of the pre boost area which will load motor off boost helping the turbos came on sooner and then let the boost take care of the top end

[bigmikespec]

This is the simplest answer to the question

Lift will give torque every where duration will give HP in the top end, top end horse power comes at the cost of low end torque

My car came with 260 poncams I the changed then to 250 poncams and everything happened 800-1000rpm sooner with the same peak power and made the car a lot nicer to drive in the low rpm range for DD

NAs need velocity to get their best which is why long duration cams work for them but turbos need volume which is why high lift works for turbos

My philosophy with turbos is get the cams to take care of the pre boost area which will load motor off boost helping the turbos came on sooner and then let the boost take care of the top end

Works for NA's because they have atmospheric exhaust back pressure, when a turbo engine has boost pressure higher than exhaust manifold back pressure then you can choose an NA cam (almost).

[XKLABA]

Works for NA's because they have atmospheric exhaust back pressure, when a turbo engine has boost pressure higher than exhaust manifold back pressure then you can choose an NA cam (almost).

The explanation depends on how much detail you want to go into on it, simple answer is the cams barely close so the air keeps moving though motor faster

[HarrisRacing]

This is the simplest answer to the question

Lift will give torque every where duration will give HP in the top end, top end horse power comes at the cost of low end torque

My car came with 260 poncams I the changed then to 250 poncams and everything happened 800-1000rpm sooner with the same peak power and made the car a lot nicer to drive in the low rpm range for DD

NAs need velocity to get their best which is why long duration cams work for them but turbos need volume which is why high lift works for turbos

My philosophy with turbos is get the cams to take care of the pre boost area which will load motor off boost helping the turbos came on sooner and then let the boost take care of the top end

I can assume based on your signature that this is with stock turbos and stock displacement? Also assuming stock springs?