Intake/ exhaust lift ratio theory

[TorQuePimp]

Very interesting thread. I am not a cam designer, but like everyone, I have my favourites as players in the overall combination of any particular build. It is interesting that it only appears to be MR and HQ cams that have the low lift exhausts. I haven't had the opportunity to try any of the Kury cams, but I do use the HQ ones.
This is a 2012 Canbus Dyna I tuned last week with a HQ113 build. HQ heads (1.900/1.625), HQ-575 cams, 10.5 compression, Supermeg 26 discs closed cap, HPI 55mm TB with 1.660 intake runners, SE Heavy Breather.
HQ-575 specs are IN 20/40 240 .575  EX 52/24 256 .530. The lobes are also asymetric.
This combo is designed for early torque rather than big horsepower, and whilst I accept that the cams are only one factor in this, it doesn't appear that the low lift, long duration exhaust is hurting anything at lower rpm. At small throttle openings on the street, the response is instant.

http://harleytechtalk.com/htt/index.php/topic,59224.0.html

  Not sure HQ/Kury Roland would be the only people

[Powerglides]

Very interesting thread. I am not a cam designer, but like everyone, I have my favourites as players in the overall combination of any particular build. It is interesting that it only appears to be MR and HQ cams that have the low lift exhausts. I haven't had the opportunity to try any of the Kury cams, but I do use the HQ ones.
This is a 2012 Canbus Dyna I tuned last week with a HQ113 build. HQ heads (1.900/1.625), HQ-575 cams, 10.5 compression, Supermeg 26 discs closed cap, HPI 55mm TB with 1.660 intake runners, SE Heavy Breather.
HQ-575 specs are IN 20/40 240 .575  EX 52/24 256 .530. The lobes are also asymetric.
This combo is designed for early torque rather than big horsepower, and whilst I accept that the cams are only one factor in this, it doesn't appear that the low lift, long duration exhaust is hurting anything at lower rpm. At small throttle openings on the street, the response is instant.

http://harleytechtalk.com/htt/index.php/topic,59224.0.html

  Not sure HQ/Kury Roland would be the only people

Sorry, perhaps I should have worded things a little better. There may well be other cams that follow this line of thought, but I was unaware of them. Some of the HQ and Kury cams have low lift exhaust, relative to the intake lift. Many existing "bolt in" grinds from the Evolution and early Twin Cam era (including the HQ 0024 and 0034) had the same In and Ex lift, as the constraints were imposed by the wish to use the existing OEM springs.

[uglyDougly]

Powerglides, do you have any other dyno charts using that pipe with other cams? and displacement?

Being a Superflow, those numbers are huge.

  Doug

[1FSTRK]

It was just a month or two ago here the cams to get were the Fueling cams with between 5 and 15 degrees more exhaust duration than intake and some with more exhaust lift.

[Steve Cole]

Cam of the week club around here.

The truth is there are lots of cams that work well on a HD with the right combination of parts. Low lift longer duration and higher lift shorter duration has to go with whatever the rest of the parts you put with it. Theory changes as the various parts do, it's NOT all Black and White. What works well for one setup maynot work well for another, so pick your poison.

[TorQuePimp]

  Steve it is not about the "cam of the week" club at all.

  I have a hard time understanding where some of the cam designs come from but there is the possibility that there will be some more good ones.

  Kury it appears has another winner with the tc-24,Ive seen a few sheets from really stingy dynos with the CR630 from cyclerama that look real good with low 190's ccp and heads done by a guy I know well who is scared of a grinder.

  Then you have copycats and that just happens

[Powerglides]

Powerglides, do you have any other dyno charts using that pipe with other cams? and displacement?

Being a Superflow, those numbers are huge.

  Doug

Yes I do Doug. The Supermeg is my pipe of choice if I can get to the customer first (they are easy to tune with and noise is becoming a big issue over here). I have only used that 575 cam with these particular builds (113, 4.375 x 4.065).
The numbers thing is is a whole different debate, but the Superflows, as well as the DynaPros, read lower than Dynojets. Both of these dyno softwares can add a multiplier to the SAE correction to mirror how a DJ would read. This, of course, assumes that the multiplier is accurate. Superflow told me that the DJ 250i reads 12% higher than the Cycledyn, and S&S told me it was 9%. When Superflow came over to commission my Cycledyn, once it was installed, I asked them to configure it at 10%. Note that my charts show DJWP and DJWTq, as this is the best comparison we can come up with. When I'm tuning and testing, I just ignore this and use the SAE corrected values, as I'm only really interested in the % gains and losses and the shape of the torque curve.
If you PM me an e-mail address I can send you whatever relevant info I have regarding the Supermeg with different cams and builds.

[dynaglide]

so if I'm understanding this thread, as well as the one WFOLarry linked to, I can take an existing cam, e.g. an Andrews 37, and gain a bit by adding SE 1.725 rockers on ONLY the intake side...?   

[TorQuePimp]

 Not alot but some yes,should work well with a 37,se204 and a few others.

  Or buy a better cam

[dynaglide]

it was a theoretical question to make sure I'm understanding the concept, not a complaint about that particular cam - I just picked the 37 out of the air to use as an example, could just as easily have said S&S 570, or any other cam with more exhaust duration than intake duration.

And part of the intent behind the question was to clarify that adding the higher rocker ratio on the exhaust side would not net any additional gain over what was to be had (regardless of how much) by only putting "stilts" on the intake side.

[strokerjlk]

And part of the intent behind the question was to clarify that adding the higher rocker ratio on the exhaust side would not net any additional gain over what was to be had (regardless of how much) by only putting "stilts" on the intake side.

I don't think you could say that straight across the board. In other words its not going to apply to every combination . IMO

[Sporty 48]

When Roland and I did the separate inlet Buell project, I gave him my Dynomation dongle and he did hundreds of simulations.
  The first thing we did was establish a Dynomation model that matched the parts and then changed that to replicate the dyno results of our parts combination.
  One of the major mistakes others make when modelling H-D engines is to input the inlet length by measuring the length from the valve seat to the mouth of the carb.
That model is optimistic because it implies a long-ish intake tract.
  In fact the 'Y'manifold H-D has an inlet length that goes from the inlet valve seat to the significant cross-sectional area change. That is a couple/few inches.
  At that time Feasel had modelled his from the seat to the carb inlet but he didn't consider that the port length went from the seat to the closest part of the siamesed section.
  George Smith showed us the cam specs, port molds, and flow-sheets to Dave Feasels 8.09 second pro-stock at that time.
  We figured out the power that it needed to do 8 sec. flat. and properly modeled, with the correct inlet dimensions, and it was spot on.
  Basically, that confirmed that the method we were using to model the inlet was correct. Then we confirmed the same with Mike's separate inlet Buell using actual dyno results.
  When Mike rebuilt the engine with 1/8 in. greater bore (the 78.69 CI engine) he had the 0.650" lift cams
that Andrews had done to the same open/close specs as the previous 0.510" lift cams, (White Lightning on slightly wider centerlines) he did the Dynomation simulations.
By that time we were able to predict direction and magnitude of the changes pretty well with Dynomation.
  When Mike modelled the next build with the 0.650" lift cams, he also modelled it with the existing 0.510" lift exhaust cams that we had been using.
The Dynomation results were exactly the same. We discussed it and he put the 0.510" lift cams on the exhaust side.
  Some people in the know have said that I have the best collection of Ducati Desmo-Quatro (851-996 engine series) cam information in the world and that shows me that Ducati went from 140HP in 1992 to 190HP in 1999 with the same exhaust cam. That cam is the 'G' cam with limited lift and way too much duration for 10,500 RPM in 1992 to over 12,000 in '99 with larger exhaust valves.
  At the same time the 'factory' increased the lift and decreased the duration of the inlet cams (to support bigger inlet/exhaust valves and keep them from hitting one another.)
  That showed me that the exhaust doesn't need high lift and does need longer duration for high RPM.

  All of this means (to me) that all of the H-D cams have too much exhaust lift and duration. Outrageous, no?!!!
  I worked with Steve Vermeer of Induction Research and he always said that too much exhaust (Ex-to-In%, or exhaust valve size, or exhaust duration) will kill torque but you can make the peak HP.

  The place you need enough overlap is at the HP peak, every place below that you have too much. It hurts emissions and drivability, but the correct minimum overlap is necessary to maximize the HP.

  Sorry guys, if all of the cams available to you have too much exhaust and/or overlap for the RPM you run, you will never know how little you need. And you'll never know how much torque you are giving up.

  Roland did put the 0.510" lift inlets into his 'Y' manifold engine along with stock (non-White Lightning) exhausts and it made 90HP when fresh but the power dropped off as the valves got carboned up. Never got 90HP after fresh. All we can do is assume that the stock Buell exhaust cams may be marginal for anyting over 90HP.
  Nobody ever puts in inlet cams only and none of the cam grinders make/sell Twincam cams with stock exhaust lift and duration, so nobody else has actually tested these things.
  Also, we tuned for every change, and almost nobody does that either.

  When I wrote that thing on the 110 Kury thread I realized as I was wrapping it up the the key component was the part about the Chevy cams being the centerline for the Chevy engines and the H-D engines are all to the more exhaust, less RPM side of that centerline. (Just a reminder that the discipline of writing, is a learning process in itself.)

  So, since I have had the opportunity to test a lot of these things, and most people don't, pardon me if I have a little confidence in my conclusions.

  In God we trust, all others bring data!!! (quote; Ed Dahir, The Dyno Difference.)

   Doug

Doug,
Wow! Have been struggling with this and you seem to have hit it on the head with a hammer.
My turbo Sportster does act like a NA Harley, it still it has 1.81" intake and 1.575" exhaust valves and stock cams, in other words, a stock motor with an exhaust driven hair dryer for boost and more power.
In looking for the next level of performance to go from 100 to 125hp I was thinking about increasing the exhaust valve size plus some port smoothing, intake manifold matching with a couple more pounds of boost. Now I think the next jump in power could very well be right in the exhaust cams. Usually air cooled turbos have bigger exhaust valves, 0.87-0.9% of intake size but a cam could compensate some.
This is going to take some thought. Thanks.
Of course the next 25hp could just be gained by increasing the boost another 5psi, but that would not be fun, would it.
Edit: EricZ got 125 hp with 7psi boost on a stock XB, so the stock cams are not so bad. http://xlforum.net/vbportal/forums/showthread.php?t=1609936&page=2

[strokerjlk]

Doug,
Wow! Have been struggling with this and you seem to have hit it on the head with a hammer.
My turbo Sportster does act like a NA Harley, it still it has 1.81" intake and 1.575" exhaust valves and stock cams, in other words, a stock motor with an exhaust driven hair dryer for boost and more power.
In looking for the next level of performance to go from 100 to 125hp I was thinking about increasing the exhaust valve size plus some port smoothing, intake manifold matching with a couple more pounds of boost. Now I think the next jump in power could very well be right in the exhaust cams. Usually air cooled turbos have bigger exhaust valves, 0.87-0.9% of intake size but a cam could compensate some.
This is going to take some thought. Thanks.
Of course the next 25hp could just be gained by increasing the boost another 5psi, but that would not be fun, would it.
Edit: EricZ got 125 hp with 7psi boost on a stock XB, so the stock cams are not so bad. http://xlforum.net/vbportal/forums/showthread.php?t=1609936&page=2  « Last Edit: Tuesday, March 12, 2013. 08:00:32 AM. by Sporty 48 » 

it needs someething besides the stock cams.
whatever you buy into for exhaust lobe  profile 
it still needs intake improvement or its going nowhere.
nice job with the turbo

[uglyDougly]

  With any supercharged application the inlet pressure increases the volume flow during overlap. Clearing the cylinder of residual charge (EGR) is critical to producing torque.
  Stock cam overlap (chosen for emissions) may be adequate for some supercharged engines. In the good-old-days they used 'blow-down', or inlet flow thru the chamber and out the exhaust, to cool their engines. For record attempts they didn't care about fuel efficiency.
  In a turbo-supercharged application, there is more exhaust back-pressure than stock and I have no idea what the exhaust cam needs to work with that.
  As with any other application, intake closing will be critical to maximising power and I don't know what IVC would work for this situation.
  Don't know, don't know, don't know!!??!!  That's what testing is for.

  Doug

[Sporty 48]

it needs someething besides the stock cams.
whatever you buy into for exhaust lobe  profile 
it still needs intake improvement or its going nowhere.
nice job with the turbo

Thanks.
Planning the Stage 2 for next fall-winter.
The turbo is by Hellcat Customs Jason Sarratt, a young old master.

  With any supercharged application the inlet pressure increases the volume flow during overlap. Clearing the cylinder of residual charge (EGR) is critical to producing torque.
  Stock cam overlap (chosen for emissions) may be adequate for some supercharged engines. In the good-old-days they used 'blow-down', or inlet flow thru the chamber and out the exhaust, to cool their engines. For record attempts they didn't care about fuel efficiency.
  In a turbo-supercharged application, there is more exhaust back-pressure than stock and I have no idea what the exhaust cam needs to work with that.
  As with any other application, intake closing will be critical to maximising power and I don't know what IVC would work for this situation.
  Don't know, don't know, don't know!!??!!  That's what testing is for.

  Doug

Doug,
Testing is good.
Using the work of the old masters is nice too. WW2 aircraft, air cooled turbocharged gas engines are examples worthy of consideration. This is not new, just need to learn, understand theory.
Of course with EFI the injected charge of gas can cool the engine, the hp gains quickly test the limits of connecting rods and cranks as well, so it is a balancing act. 
Thanks.