How Much Of A Difference Higher Lift Makes ? + Camshaft Duration

[GTSBoy]

I've pesonnaly never seen it happen and can't imagine it's possible

Think F1 and Indy Car type setups. Corky Bell had a whole section on this in his turbo book.

[XKLABA]

What can be considered as high duration ? Is it dependant on the engine make or theres some sort of concensus ?

You went with TYPE-R, if you could, wouldn't you have prefered if it came with a higher lift ? like 10.25 ?

260 is as far as I would go on anything other then an auto backed drag car planning on 10k + revs, even at 260 it would have to be no less then 10mm lift so you still got the volume into the motor, IMO ideally around the 250 mark is where an RB is best

I am looking at either or both of the cams I mention earlier, if possible I will be getting the 248s for the 32 but haven't dicided if I will get the 248s or 252s for the 34, so yes if I could have got Type Rs with more lift I would have

[XKLABA]

Think F1 and Indy Car type setups. Corky Bell had a whole section on this in his turbo book.

Ok, i will have to find that book, though what do they rev those two types of cars to and the likely hood of someone driving a street car that way cause that is really what we are talking about here

[bigmikespec]

I've pesonnaly never seen it happen and can't imagine it's possible and I have been involved in a few turbo charged race car builds, the only way to lower manifold pressure is bigger exhaust housing and bigger turbine wheel, both of which induce lag, the turbine would need to be bigger then the comp wheel for starters

Then add to that you want to use high duration cams, I hope your happy to rev this thing past 10k chase my guess is your going to have to

The only reaso you use high duration cams is if you want to increase your high range

You haven't seen it happen? Must not be possible then

That last comment is a consequence of higher duration and not necessarily reason to do it!

Zeb, are you on about raising static comp to compensate the dynamic comp drop when you go longer duration cams?

[XKLABA]

You haven't seen it happen? Must not be possible then

That last comment is a consequence of higher duration and not necessarily reason to do it!

Zeb, are you on about raising static comp to compensate the dynamic comp drop when you go longer duration cams?

That not what I said, I said i can't imagine it would be possible and that I haven't seen it happen for my self, at no point did I say it's not possible, it may very well be but at what cost to response, reading not a strong point ?

If having to use higher revs is a consequence of high duration why would you use them, you use higher duration to increase rev range not increase rev range to use higher duration

[djr81]

What was the lift and love centres on the 256/252 cams, also did you check cam/bucket clearnces

on mine both sets of cams where setup on the dyno to give best response and most linear power graph as possible, not just dropped in and that'll do

If the stock cams had more lift I would have found a set to replace the Poncams, I may have found a lobe which [email protected], if this can be scaled down to a 32mm base and fitted to an RB stick it will be

Lift and lobe centres are as per the Tomei cam spec sheets posted earlier.

Lift is

260 is 9.15

256 is 9.25

252 is 9.15

Lobes are 110 inlet 115 exhaust - same for all.

[bigmikespec]

That not what I said, I said i can't imagine it would be possible and that I haven't seen it happen for my self, at no point did I say it's not possible, it may very well be but at what cost to response, reading not a strong point ?

If having to use higher revs is a consequence of high duration why would you use them, you use higher duration to increase rev range not increase rev range to use higher duration

Response? Not important below 4000rpm if you never drop below there.

I will just let you know when I do it!

[GTSBoy]

Sometimes there is cause. Sometimes there is effect. Sometimes you swap these.

Need to make massive power? NA? Then you have to rev the engine. For us, big revs is 9000-10000. For motor bikes it's 16000+. For F1 cars it's 20000. If you have to rev the engine high to make your power, then you have to let it breathe. So you need long duration camshafts. Aim for 18000rpm and the cams will only work above about 10000-12000.

Big cams have big overlap? So now you're wasting compression? Ok, so now you bump up the static comp ratio to gain some back.

But......how about if you need to make as much torque as you can because you can't afford to rev or the rules put a rev limit on you? So you bump up the static compression to make the engine as sharp as possible. But you can very easily bump up against the knock limit of your fuel this way. So big cams to the rescue. Blow off some of that static comp ratio so that the engine works. Don't make the cams too big or too overlappy, because you still can't afford to build the engine for revs, but the concept is still valid.

These sorts of turnabout compromise decisions are all over the place with nearly all of the choices people have in how to build an engine. Rod-stroke ratio? Bore-stroke ratio? Same there. Piston skirt length, pin height, etc? Same there. Sometimes you are forced to make a choice because you're constrained by a rule or a need. Sometimes you make the same choice because you're constrained from completely the opposite direction.

[XKLABA]

Response? Not important below 4000rpm if you never drop below there.

I will just let you know when I do it!

Again, are we talking about a street car or race car, I drive both my cars between 2-3k RPMs for street duties but I still have power all the way to 8500

I'm also talking about response between gears

[bigmikespec]

Again, are we talking about a street car or race car, I drive both my cars between 2-3k RPMs for street duties but I still have power all the way to 8500

I'm also talking about response between gears

That's fine, I get that.

At the opposite spectrum having higher boost than exhaust pressure is achievable and using camshafts with longer duration and appreciable overlap works to improve performance/power. At ultimately higher rpm, more rpm... more power (derr).

[XKLABA]

ok yeah no worries if that is what you think is right I'll leave you to it

Have you got a build thread showing what you are doing ?

What are the specs you are looking at ?

this is for a RB26 in your r33 yeah ?

When are you doing this build or expecting it to be finished ?

Let me know how it turns out for you yeah ?

PS, Lith, I'll be at Micks Saturday night, don't get to drunk before I get there, would like to take you for a run in the 34

And I'm out, it's been fun

[bigmikespec]

ok yeah no worries if that is what you think is right I'll leave you to it

Have you got a build thread showing what you are doing ?

What are the specs you are looking at ?

this is for a RB26 in your r33 yeah ?

When are you doing this build or expecting it to be finished ?

Let me know how it turns out for you yeah ?

PS, Lith, I'll be at Micks Saturday night, don't get to drunk before I get there, would like to take you for a run in the 34

And I'm out, it's been fun

It is not what I think, it is proven and documented. It might not be applicable for 99% of people on this forum but don't discount it as not possible or not achievable. It has been done, people are doing it!

If you seriously are interested then PM me and I can answer what ever question you have; don't just bash me with condescending questions then say 'I'm out'... come on dude.

[djr81]

260 is as far as I would go on anything other then an auto backed drag car planning on 10k + revs, even at 260 it would have to be no less then 10mm lift so you still got the volume into the motor, IMO ideally around the 250 mark is where an RB is best

I am looking at either or both of the cams I mention earlier, if possible I will be getting the 248s for the 32 but haven't dicided if I will get the 248s or 252s for the 34, so yes if I could have got Type Rs with more lift I would have

be interested to hear some comments on the above. 98, 256 & 252 cams & -5 turbos.

[SimonR32]

3102_001.jpg

be interested to hear some comments on the above. 98, 256 & 252 cams & -5 turbos.

Needs E85 and a medium single?!?

[djr81]

Stock rods too?

E85 I would love but the logistics of it are hopeless.

[GTSBoy]

Lower ex manifold pressure than boost is not a workable engine configuration for a street engine. What it comes down to is a very large back half of turbo meaning low restriction. Makes the engine very very efficient when it's on boost.....but means that it doesn't want to come on boost until there is seriously high exhaust flow. Strictly race engine stuff. Race/ski boats would be the best example.

[XKLABA]

3102_001.jpg

be interested to hear some comments on the above. 98, 256 & 252 cams & -5 turbos.

PM sent, I meant 252

[jet_r31]

Think F1 and Indy Car type setups. Corky Bell had a whole section on this in his turbo book.

maybe look at the drag turbo v8 guys in the states aswell

big cams having big overlap..i thought the way to stop this was to increase the lobe separation angle of the camshaft

as you run more duration, you widen the separation to combat this, also makes it idle smoother and increases the midrange.

eg

240 [email protected] 114 lsa

250 duration @.50 115 lsa

260 [email protected] 116 lsa

or similiar

probally doesn't kill top end like you think it would either as most cars are turbine/housing limited anyway once on kill

interesting subject, i know enough to get me in trouble from just playing around with stuff, but nothing in the whole realm of it

at least australian suppliers have picked up there game in the last 15yrs, with regards to a "turbo' cam

most older people will remember when using a stock cam was the go and there was a myth not to use a bigger cam in a turbo motor.

Now looking back you can see how the myth started, cars would have been out of turbo flow and hotside limited so a bigger cam

woudn't help, and most turbo cams had bad lsa's..

having said that, its easy to overcam most turbo motors, my most fun to drive setups

have always had small camshafts to fatten midrange and bring it on boost quick, but lots of turbine flow so you can run heaps of boost

and it still makes shitloads of grunt with not a lot of backpressure, they live longer to as they don;t rev as hard.

cheers

darren

Edited October 9, 2014 by jet_r31

[cobrAA]

For anyone searching throught this thread in the future, I asked kelford for a very responsive rb26, efr 83/74 EWG with civile idle because I mostly drive the car downtown ( lots of stop and go, can be stuck in traffic at anytime, etc). Here's their answer :

Very nice choice on turbo and manifold mate, I love those EFR's, for your package I'd be looking at the 182-S cams mate http://www.camshaftshop.com/products.php?productid=41337#specs along with our KVS15 drop in spring. These don't have too much duration so that you'll be waiting all day for power which is what it sounds like you're in to and they have 10.5mm of lift which in an RB is nothing to be scoffed at.

They have our split intake technology as part of the deal so you get increased efficiency and torque over standard set of the same specs.

These along with that awesome turbo of yours should make for a very potent little street package mate, with great response and midrange torque, but still have the ability to stretch its legs out when you feel the need

1) Anyone heard about this split intake technology ?

2) comparaison

182-S ... nett valve lift 10.5mm at 1mm, duration is 236

Tomei:
type-R net valve lift 8.7mm at 1mm, duration is 216
Procam 270 10.8mm.. net valve lift is 10.4mm and at 1mm, duration is 237.

Like other said, theres more than simply the number, anyone heard of this split intake tech ?

thank guys!

[r33_racer]

Sounds like they are mismatching the intake lobe centres so they are phased differently to each other in each cylinder grouping. So they are basically opening one valve earlier or later then the other (depending on which way you look at it lol).

A quick and easy way to change the mixture motion going into the chamber. Trying to induce more swirl into the airflow pattern entering the chamber which will increase efficiency and torque through better air/fuel atomisation and more complete burning of the mixture.

If I were you I would go for those new kelford cams!

Actually if you didn't want to use their cams you could achieve a similar effect by mismatching the valve lash on your intake valves. Set 1 valve at say 0.010" and then its mate at say 0.020". I have no idea what that difference might achieve in terms of valve opening degrees though. You would have to try it and dummy assemble and then use degree wheel & dial indicator to measure the difference in actual valve timing.

Edited October 9, 2014 by r33_racer