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

[No Crust Racing]

Agreed. 

 

[No Crust Racing]

Here's what Josh from Kelford had to say when I was questioning him. 

 

In regards to cam selection, yes you are right in some cases the bigger the cam the further up the mid-range the power will go, picking the right cam for the power level and the application is a must.

Centre line of the cam shaft is one of the biggest thing when trying to bring the power on earlier, the L182-A setup intake on 108  centreline and the exhaust on 114 is where I would recommend, and then move them around a few degrees on the dyno to find the power curve that suits you.

You should be able to achieve roughly the same response you are getting now with stock cams but an increase in midrange and holding to the red line, you will find the boost pressure will drop because the engine is breathing more efficiently and make similar power as before but on less boost.  

It’s a bit of give and take though, you get improvements by moving stock cams but from the dyno figure you have sent it did hurt the top end, if it’s a decent increase in power you are after then you will need a larger cam and more it around too suit.

[GTSBoy]

55 minutes ago, r32-25t said:

We've got dyno sheets and compression tests that prove how much they ruin the bottom end but yeah go and buy a set cause the placebo effect of the lumpy idle fixes everything

 

51 minutes ago, ActionDan said:

You're not convincing me one way or the other, there's far too many conflicting opinions and dyno sheets for there to be a clear answer to this. 

 

Every engine/turbo/cam choice/dyno read out combo seems to say slightly different things - As per the above example (which is the opposite result of many of the other examples we've also seen). 

 

 

 

And the winner is......Piggaz.  Seriously, if you change NOTHING else, then more duration pretty much has to hurt response.  It simply makes the engine work better at higher revs than before.  But if you change ANYTHING else, then you have to balance the pluses and minuses.  Add some duration but add a lot of lift?  Yup, probably improve response, because the thing is flowing more air down low AS WELL as flowing more air up high.  And so on, and so forth.

Cam profiles are a little like dyno curves.  Area under the curve is important.  If you can open the valves on a steeper ramp (and keep them under control) and you can open them further you can make a lot more power even with the same or smaller advertised duration.

[r32-25t]

or fitting a set of turbo chargers then aren't out of flow would work as well 

 

the reason the cams "worked" on your Silvia and on simons gtr would have a great deal to do with the single turbo changer and the ability of the manifold turbine housing to get the gas through it efficiently, where with the twins the exhaust housing will cause the  exhaust has to begin to back up and making the larger cam useless and even a disadvantage 

[No Crust Racing]

1 minute ago, r32-25t said:

or fitting a set of turbo chargers then aren't out of flow would work as well 

 

the reason the cams "worked" on your Silvia and on simons gtr would have a great deal to do with the single turbo changer and the ability of the manifold turbine housing to get the gas through it efficiently, where with the twins the exhaust housing will cause the  exhaust has to begin to back up and making the larger cam useless and even a disadvantage 

Despite the weird grammar and typos, I think I get what you're saying, less gain from improvement in airflow if it just chokes the exhaust housing/increases back pressure etc. 

Which is not something I'm disputing anyway?

I'm simply saying, as I've always said, that it;s not as simple as CAM A will always get X result and Cam B will always get Y result. 

Too many variables for the sweeping statements people make. 

 

 

[Lithium]

26 minutes ago, GTSBoy said:

And the winner is......Piggaz.  Seriously, if you change NOTHING else, then more duration pretty much has to hurt response.  It simply makes the engine work better at higher revs than before.  

Was a little sad to read this post.  You are usually one of my favourite guys to read posts from, both paying attention to what others have to say and also a bit more thoughtful/wise about what you say.   None of us here are expert enough to pull a trump card and state what the correct answer like that, and seriously I'm bewildered you feel you can launch into a topic and effectively say "no, this stuff is not that complicated. More advertised duration makes a car laggier and worse, end of." 

I am no expert but I have been around and played with enough to know that when playing with this kind of thing that making that kind of generalisation is folly, I can't say I know enough to know what will work or how things will compare as again by my own admission it's something I am far from an expert on and there are wayyy too many variables involved to even try.  General rules of thumb are one thing and often work but that's for general estimation, not the rules that all of physics have to abide by to keep things simple for us to compare - as nice as that would be. 

As a thought experiment ... you say longer duration makes the engine work better with more rpm... purely hypothetically but what say you have an engine which makes full boost at 4700rpm with a 240degree cam and change to a set of 260degree cams of similar peak lift where the threshold of working worse to  working better than stock is around 3000rpm - are you suggesting that despite the motor being able to pump air better above 3000rpm and assuming the engine is not running turbo(s) that are choking the motor at that point that it's not going to yield torque / spool gains from the resulting VE improvement despite the gains starting to happen well within boost threshold? 

Edited October 27, 2016 by Lithium

[r32-25t]

 

41 minutes ago, ActionDan said:

Despite the weird grammar and typos, 

The joys of trying to type on a phone when half asleep 

[GTSBoy]

1 hour ago, Lithium said:

As a thought experiment ... you say longer duration makes the engine work better with more rpm... purely hypothetically but what say you have an engine which makes full boost at 4700rpm with a 240degree cam and change to a set of 260degree cams of similar peak lift where the threshold of working worse to  working better than stock is around 3000rpm - are you suggesting that despite the motor being able to pump air better above 3000rpm and assuming the engine is not running turbo(s) that are choking the motor at that point that it's not going to yield torque / spool gains from the resulting VE improvement despite the gains starting to happen well within boost threshold? 

 

Actually, I think I am saying that.  Of course it is going to depend on what you call "response", but in general I take the view of assessing how it works from below the boost threshold, up through the onset of boost and onwards (so starting a dyno pull at 2000 rpm say).  If the car is running NA (below the boost threshold), then the whole question of what the turbo is doing is moot, and you can look at what the engine is doing as if it actually was NA.  If longer duration cams are swapped in with no other changes, then the breathing at lower rpm is compromised compared to what it used to be.  The engine makes less flow, which does less to spool up the turbo, which in turn should actually make the whole situation even worse than if the engine was NA.

If however you are looking at it from the point of view of dropping revs from an upward gearchange and staying in the rev range where the cams are pretty happy and the turbo will make some boost, then the situation will be a bit more blurry.  Your thought experiment could be the perfect example of that view.

And so of course you are right.   I made a sweeping statement, based on my concept of what response means.  And if that does not align with how others are thinking about what it means, then the sweeping statement is not valid.

The only time I've actually played with cams on my cars was in my ALFA, because I haven't modded the Skyline to the point where it's worthwhile.  So it was carburetted and all the other evils that come with it.  Carb tuning makes even more complications to assessing cam changes.  But the simple fact with that engine was that longer duration cams with the same lift made the car slower everywhere except when keeping it on the boil.  It was only when some properly thought out cam profiles were put in it (as much lift as would fit and fairly steep ramps without much more total duration) that it worked better.  It got crankier though, even with not much extra duration, because the sudden valve opening events changed the way it pulled on the carbies.  /sidetrack discussion.

[SimonR32]

8 hours ago, GTSBoy said:

And the winner is......Piggaz.  Seriously, if you change NOTHING else, then more duration pretty much has to hurt response.  It simply makes the engine work better at higher revs than before.  But if you change ANYTHING else, then you have to balance the pluses and minuses.  Add some duration but add a lot of lift?  Yup, probably improve response, because the thing is flowing more air down low AS WELL as flowing more air up high.  And so on, and so forth.

I literally just pulled one set of cams at 250deg 9.15 lift and replaced with 260deg 9.15 lift from the same manufacturer (Tomei). Changed NOTHING else and picked up 300rpm of boost response, so please tell me again how I'm wrong and it has hurt response?

[GTSBoy]

What's the lift at 50 thou for each of those?  Maybe there's a reason why they are called "Type-R".  Maybe they are Civic VTEC yo cams.

 

But seriously, maybe Mr Lithium is right.  If the boost threshold is significantly above where the cams start working well for the engine, then they will flow more gas and get the turbo spinning earlier.  Otherwise we have to say measurement error, [mumble mumble], works in theory therefore the practice must be wrong [mumble mumble] etc.

[Lithium]

10 hours ago, GTSBoy said:

 

If longer duration cams are swapped in with no other changes, then the breathing at lower rpm is compromised compared to what it used to be.  The engine makes less flow, which does less to spool up the turbo, which in turn should actually make the whole situation even worse than if the engine was NA.

If however you are looking at it from the point of view of dropping revs from an upward gearchange and staying in the rev range where the cams are pretty happy and the turbo will make some boost, then the situation will be a bit more blurry.  Your thought experiment could be the perfect example of that view.

And so of course you are right.   I made a sweeping statement, based on my concept of what response means.  And if that does not align with how others are thinking about what it means, then the sweeping statement is not valid.

But the simple fact with that engine was that longer duration cams with the same lift made the car slower everywhere except when keeping it on the boil.  It was only when some properly thought out cam profiles were put in it (as much lift as would fit and fairly steep ramps without much more total duration) that it worked better.  It got crankier though, even with not much extra duration, because the sudden valve opening events changed the way it pulled on the carbies.  /sidetrack discussion.

OK, sorry - that makes more sense, yeah we're probably closer to the same view than I thought however you're still ignoring a few variables which can influence things.... though you aren't specifically saying "250deg for EVERYTHING" that I know of so possibly not relevant

Now we actually see there is a fair bit more overlap (hurhur) in how we're looking at it - and keeping with the NA view on things to keep it simple, I don't think I agree fully with the "just for up shifts" relevance - at least for my example.   3000rpm isn't upshift territory, that is actually often in the normal driving around zone - well below boost threshold, so realistically where the car would often be driven.    Yes, there is a sacrifice in response at very low rpm where if you are modifying to the point you need more head flow and have a bigger turbo then one would think of that area as not too relevant, so long as you have matched the cams and turbo to appropriately suit the rest of your setup.  That is the case with everything though, a bigger turbo makes the boost threshold come later AND transient response can become doughier - the hypothetical case I gave here will also bend the torque curve upwards like that too but without the transient response issue.   

The kind of thing you are saying is what I'd expect with huge drag spec / NA race motor cams, but the likes of Kelfords 270s won't be aiming for that kind of thing - at least I wouldn't think so.  I personally think if I'm using a car as a fast road car/track car then I would rather a car that stands up better from 3500/4000rpm and is still perfectly drivable below there as well as making more power everywhere above there, than making a car slightly more grunty and build a little more boost at "potter around town" rpm.  It all comes down to matching the parts to what you are doing.

Something to ponder in regards to your dyno pull example, yes - I agree the smaller cams are likely to build a bit more boost from 2000rpm but what is easily overlooked is how little air is moved at those rpm and realistically if you have a turbo that isn't going to be fully on boil until after 4000rpm then the "extra spool" is not going to be a huge deal.   If you are at 3500pm and we assuming you have the same VE there at 2000 then you are moving 75% more gas at that point with all things (including boost) being equal.  That won't be happening, though - even mild cam engines will have substantially more VE at 3500rpm so you have much more than 75% more gas, so what happens there has a MUCH bigger influence on how the turbo is driven in the real world.

Now imagine my hypothetical cam example - I'll be ultra silly about it and pull numbers out of nowhere, lets say little cam gives 85% VE at 2000rpm and 90% VE at 3500, and big cam gives 80% VE and 95% VE at those respective points on a 2.6litre.

At 2000rpm the small cam could be moving 2210lpm of air, the big cam could be moving 2080lpm.

At 3500rpm the small cam could be moving 4095lpm of air, the big cam could be moving 4323lpm.

Basically the difference in flow (/ perhaps ability to spool a turbo?) is 250% more with the big cam at 3500rpm versus the small cam at 2000rpm.   If you play with dynos, try doing a run starting at 2000rpm with a lead in time of 4 seconds and then another run with the same car starting at 3000rpm with a lead in time of 2 seconds - odds are reasonable that, depending of course on ramp rate etc the boost curve for the run starting at 3000rpm will look more flattering despite the 2000rpm run getting heaps more time to try and spool the turbo up as the sheer exhaust energy pushed through the turbine in that 2 seconds will be much more than the 4seconds at 2000rpm.

Any edge in engine flow you can gain with a turbocharged motor which doesn't rely on boost can pay big dividends as it tends to feed back on itself, the more you flow into the turbo the faster it can supply even more flow and so on.   A stroker is a foolproof way of doing it but if you can increase VE at useful rpm then that is also very cool but again, there will always be trade offs.  The very aggressive ramp rates to high lift with a short advertised duration which some people use is one way of trying to minimize the trade offs and to be fair it is pretty effective in a lot of ways, but it's not "for free" either.

Anyway, apologies for the huge post - I wrote the first part last night and my computer reset itself to do updates just before I sent and I felt more like spewing ideas on this morning's commute.... finding an interesting thing to discuss when I have 2 hours on a train each day is temptation I struggle with resisting.

[Lithium]

4 hours ago, GTSBoy said:

But seriously, maybe Mr Lithium is right.  If the boost threshold is significantly above where the cams start working well for the engine, then they will flow more gas and get the turbo spinning earlier.  Otherwise we have to say measurement error, [mumble mumble], works in theory therefore the practice must be wrong [mumble mumble] etc.

Haha you're very generous, alas I actually made up a bunch of variables with that example and I'm not going to argue a rule of thumb otherwise - I just made up a theoretical situation which would/should function the way I hypothesized if such a cam existed.  The main reason I posted was just to try and highlight there is much more going on when changing to a different spec cam than just "losing response" as an all encompassing thing - it comes from people focusing on a specific rev range.  

I nearly don't know enough about how cams etc etc work to just glance at a spec and tell you how it's going to work on a setup, but I also suspect I have more of an idea than your average punter so one way or another I think this discussion is the blind leading the blind - but it's interesting to compare ideas and experiences to see what comes out.  

I very much look forward to how Simon's car comes out with the Kelfords, I've been wanting to see a set of those tried for AGES and you can't really argue with real world results - for better or for worse.

[No Crust Racing]

I think we can all agree that what I said was right, there are too many variables to make large sweeping statements.

I've shown Josh from kelford my dyno graph and given him a list of my mods and asked him what he thinks the outcome will be so it will be interesting to get his view.

[WMDC35]

/\ I'd tell Kelfords what you have, what you want & trust them to supply something good.

[No Crust Racing]

I said to Josh:  Based on your cam recommendations, what would you expect the behavior/power/torque differences to be? 

He said:  It will all depend where you put the cams and start moving them around on the dyno, the L182-A will come on about the same on 110 114 centrelines, you could advance both intake and exhaust and it should come on a tad earlier than you have now with the standard cams just because the extra exhaust flow will help spool the turbos, by doing this you will lose peak power though, like I said in the last email it’s give and take you will trade some bottom end for peak power or peak power for bottom end. Most guys find that medium that works for them.

I then said:Would you think I'd be able to match the response but see torque gains from boost onwards? And what sort of increases are realistic with this cam?

And he said:  You should easily match the response and yes there will be defendant mid-range gains, we normally put the gains in the 10-12% mark for a cam of this size.

That's from the expert. 

[No Crust Racing]

I'm a bit confused as earlier in the email he refers to the cam as  L182-A 264-9.2mm cams

But L182-A on the site only shows 8.95/8.9mm lift. http://www.camshaftshop.com/products.php?productid=1051

A 10% gain from boost on wards would be pretty tasty... 

[No Crust Racing]

He explained:  Yes that is the cams, I have stated cam lift not valve lift, the link you sent through is correct for valve lift.

[No Crust Racing]

He also added when I questioned lift. 

This is the max valve lift you can run for a drop in RB26 cam, we allow for any differences we have seen in head castings as core shift is quite large on RB26 heads. Some other cams on the market may state a little bit more lift but it is more and likely cam lift or they may reduce the base circle, and lift the bucket higher to allow for more lift but then that defeats the purpose for a drop in cam.

 

I thanked him for his fantastic customer service. 

[No Crust Racing]

He also added:  No problem what so ever Dan I’m glad to help, just for a matter of interest Tomei pon cams are 9.15mm cam lift on both and are 8.7mm valve lift on the intake and 8.77mm on the exhaust, that also means they run very large ramp heights or in other words big valve clearances, that says the lobe is lazy and will have more seat timing that inherits a loss in throttle response, just thought I would put that out there.

[Lithium]

25 minutes ago, ActionDan said:

He also added:  No problem what so ever Dan I’m glad to help, just for a matter of interest Tomei pon cams are 9.15mm cam lift on both and are 8.7mm valve lift on the intake and 8.77mm on the exhaust, that also means they run very large ramp heights or in other words big valve clearances, that says the lobe is lazy and will have more seat timing that inherits a loss in throttle response, just thought I would put that out there.

This is all awesome input, cheers for sharing it.  Again - this stuff will only be scratching the surface, too.