Valve overlap.......

Post 684714 by oblark on 2014-01-27 08:49:57

I hope someone can help with this little problem that Ive encounted on my engine rebuild when timing the N/A cams. A four stroke engine has 4 strokes, intake, compression, power and exhaust also the crank does two revolutions to one camshaft revolution. Starting At top dead centre (TDC) the crank is rotated clockwise, as the piston goes down on the intake stroke the inlet valves open. When the crank is at bottom dead centre (BDC) the inlet valves close and the piston comes up on the compression stroke. At the TDC on the the first rotation all valves are closed and this is power stroke. The piston then is pushed down to BTC at this point the exhaust valves open and the piston comes up to push out the exhaust gas. The problem I`ve got is the exhaust vales are open when the piston passes TDC for the intake stroke at the same time the inlet valves start to open Is this right or do I need to advance the exhaust cam timing more ?

Post 684721 by MoleT-5R on 2014-01-27 09:05:13

[QUOTE=oblark;684714]I hope someone can help with this little problem that encounted on my engine rebuild when timing the N/A cams. A four stroke engine has 4 strokes, intake, compression, power and exhaust also the crank does two revolutions to one camshaft revolution. Starting At top dead centre (TDC) the crank is rotated clockwise, as the piston goes down on the intake stroke the inlet valves open. When the crank is at bottom dead centre (BDC) the inlet valves close and the piston comes up on the compression stroke. At the TDC on the the first rotation all valves are closed and this is power stroke. The piston then is pushed down to BTC at this point the exhaust valves open and the piston comes up to push out the exhaust gas. The problem I`ve got is the exhaust vales are open when the piston passes TDC for the intake stroke at the same time the inlet valves start to open Is this right or do I need to advance the exhaust cam timing more ?[/QUOTE] this is probably correct as in alot of engines the out going exhaust gases start to suck in the start of the intake gases to fill the cylinders better, as in your thread title 'valve overlap' someone probably has the data on how long that duration should be, but your's is possibly extended with your n/a cams and extra couple of degs timing each way

Post 684723 by jamesy12345 on 2014-01-27 09:09:54

This is the thread on NA cam timing http://www.vpcuk.org/forums/showthread.php?53969-n-a-cam-timing-for-the-t5/page2 Advance the exhaust 2 degrees from standard I think

Post 684725 by oblark on 2014-01-27 09:11:05

I found this last night on valve duration on the speedswede forum N/A Intake:250dr duration 0.332 inch lift Exhaust:252,6dr duration 0.332 inch lift T5 Intake:242dr duration 0.312 inch lift Exhaust:243,5dr duration 0.312 inch lift But as yet I haven`t found any imformation on valve overlap.

Post 684727 by jamesy12345 on 2014-01-27 09:23:52

From the IPD website...... [I]Generally turbocharged engines will have very little overlap. Overlap is defined as the period where the exhaust and intake valves are open at the same time during the exhaust stroke. In most instances turbocharged engines will perform best with minimal overlap. To reduce overlap, advance the exhaust cam and retard the intake cam. For more overlap, retard the exhaust cam and advance the intake cam. Certain engine modifications to turbocharged cars can create a situation where more overlap can be desirable. These modifications are generally anything that effects exhaust back pressure or intake restriction. For instance; larger turbocharger, higher flowing downpipe and cat back exhaust or higher flowing intakes, intercoolers, or porting/polishing of the intake manifold. A popular upgrade to Volvo 5 cylinder turbocharged engines, without variable valve timing, is to replace either one or both of the factory camshafts with camshafts from a non turbo engine of the same family. These non turbo cam shafts have more lift (total valve opening) and longer duration (total time the valve is open). Non turbo intake camshafts have 0.020 inch more lift and 7 degrees more camshaft duration. The non turbo intake cam also starts its opening 4 degrees sooner than the turbo camshafts. So if a non turbo intake camshaft were to be used in a turbocharged engine, and the same overlap were desired, then the intake cam would need to be retarded by 4 degrees from the factory base setting. Non turbo exhaust cam shafts have 0.014 inch more lift (total valve opening) and 3 degrees longer duration (total time the valve is open). The non turbo exhaust cams start opening 2 degrees later than the turbo cam shaft. So to maintain the same overlap, a non turbo exhaust cam in a turbocharged engine would need to be advanced 5 degrees from the factory base setting.[/I] http://www.ipdusa.com/products/7047/115377-cam-timing-tool

Post 684733 by MoleT-5R on 2014-01-27 09:38:06

[QUOTE=oblark;684725]I found this last night on valve duration on the speedswede forum N/A Intake:250dr duration 0.332 inch lift Exhaust:252,6dr duration 0.332 inch lift T5 Intake:242dr duration 0.312 inch lift Exhaust:243,5dr duration 0.312 inch lift But as yet I haven`t found any imformation on valve overlap.[/QUOTE] Not taking into account the 2 degs extra you have put on each of your n/a cams, you have 8 degs extra intake duration and 9 degs extra exhaust duration, so 17 degs extra in total. Now depending on where the exhaust opens at the end of the power stroke 252.6 degs takes its closing point well into the intake stroke, helping to draw though the new intake gases and expel all of the lingering exhaust gases. For the intake to have closed by the bottom of the intake stroke it would have had to of opened 70 degs before the start of the intake stroke. Don't forget that the degrees are crankshaft movement so the cam movement will be halved. I think I've understood it right from my old a-series days

Post 684734 by jamesy12345 on 2014-01-27 09:38:11

Just a thought, as there seems to be conflicting info: Maybe the 'standard' timing is 3 degrees for the exhaust and 2 degrees for the intake. Then advancing the exhaust by 2 degrees makes 5 degrees in total, and retarding the intake makes 4 degrees total. This should give the standard value for overlap in a turbo. If you have a larger turbo/exhaust/etc i.e. less restriction then you may get away with more overlap – so then the exhaust could be retarded a little and the intake advanced from the 4 and 5 values mentioned above. BUT turn it over by hand first just in case I am talking rubbish!! I haven’t done this yet but soon will be…….

Post 684735 by oblark on 2014-01-27 09:38:12

[QUOTE=jamesy12345;684727]From the IPD website...... [I]Generally turbocharged engines will have very little overlap. Overlap is defined as the period where the exhaust and intake valves are open at the same time during the exhaust stroke. In most instances turbocharged engines will perform best with minimal overlap. To reduce overlap, advance the exhaust cam and retard the intake cam. For more overlap, retard the exhaust cam and advance the intake cam. Certain engine modifications to turbocharged cars can create a situation where more overlap can be desirable. These modifications are generally anything that effects exhaust back pressure or intake restriction. For instance; larger turbocharger, higher flowing downpipe and cat back exhaust or higher flowing intakes, intercoolers, or porting/polishing of the intake manifold. A popular upgrade to Volvo 5 cylinder turbocharged engines, without variable valve timing, is to replace either one or both of the factory camshafts with camshafts from a non turbo engine of the same family. These non turbo cam shafts have more lift (total valve opening) and longer duration (total time the valve is open). Non turbo intake camshafts have 0.020 inch more lift and 7 degrees more camshaft duration. The non turbo intake cam also starts its opening 4 degrees sooner than the turbo camshafts. So if a non turbo intake camshaft were to be used in a turbocharged engine, and the same overlap were desired, then the intake cam would need to be retarded by 4 degrees from the factory base setting. Non turbo exhaust cam shafts have 0.014 inch more lift (total valve opening) and 3 degrees longer duration (total time the valve is open). The non turbo exhaust cams start opening 2 degrees later than the turbo cam shaft. So to maintain the same overlap, a non turbo exhaust cam in a turbocharged engine would need to be advanced 5 degrees from the factory base setting.[/I] http://www.ipdusa.com/products/7047/115377-cam-timing-tool[/QUOTE] I`ll try that tonight when i get home :) inlet retard 4 degrees and exhaust advance 5 degrees (hopefully these enough movement in the cam slots) :)

Post 684736 by MoleT-5R on 2014-01-27 09:46:02

[QUOTE=jamesy12345;684727]From the IPD website...... [I]Generally turbocharged engines will have very little overlap. Overlap is defined as the period where the exhaust and intake valves are open at the same time during the exhaust stroke. In most instances turbocharged engines will perform best with minimal overlap. To reduce overlap, advance the exhaust cam and retard the intake cam. For more overlap, retard the exhaust cam and advance the intake cam. Certain engine modifications to turbocharged cars can create a situation where more overlap can be desirable. These modifications are generally anything that effects exhaust back pressure or intake restriction. For instance; larger turbocharger, higher flowing downpipe and cat back exhaust or higher flowing intakes, intercoolers, or porting/polishing of the intake manifold. A popular upgrade to Volvo 5 cylinder turbocharged engines, without variable valve timing, is to replace either one or both of the factory camshafts with camshafts from a non turbo engine of the same family. These non turbo cam shafts have more lift (total valve opening) and longer duration (total time the valve is open). Non turbo intake camshafts have 0.020 inch more lift and 7 degrees more camshaft duration. The non turbo intake cam also starts its opening 4 degrees sooner than the turbo camshafts. So if a non turbo intake camshaft were to be used in a turbocharged engine, and the same overlap were desired, then the intake cam would need to be retarded by 4 degrees from the factory base setting. Non turbo exhaust cam shafts have 0.014 inch more lift (total valve opening) and 3 degrees longer duration (total time the valve is open). The non turbo exhaust cams start opening 2 degrees later than the turbo cam shaft. So to maintain the same overlap, a non turbo exhaust cam in a turbocharged engine would need to be advanced 5 degrees from the factory base setting.[/I] http://www.ipdusa.com/products/7047/115377-cam-timing-tool[/QUOTE] so there is no increase in overlap, just the advantage of higher lift then. it will be interesting to see how Robs engine performs on the dyno

Post 684737 by jamesy12345 on 2014-01-27 09:46:41

[QUOTE=oblark;684735]I`ll try that tonight when i get home :) inlet retard 4 degrees and exhaust advance 5 degrees (hopefully these enough movement in the cam slots) :)[/QUOTE] I made a mistake in post 7 above, now corrected.......good luck fella I will interested to know as I have new head and NA cams to go in. I follow your posts btw but usually over my head :)

Post 684738 by oblark on 2014-01-27 09:48:25

With this and the M4.4 remapping my brain is getting a real hammering :)

Post 684739 by jamesy12345 on 2014-01-27 09:50:43

[QUOTE=MoleT5-R;684736]so there is no increase in overlap, just the advantage of higher lift then. it will be interesting to see how Robs engine performs on the dyno[/QUOTE] With those settings, I guess not. But Mr Oblark (Rob?) may get some benefit with increasing the overlap a little due to less restriction in the exhaust. Turn it over by hand first!!!!!!!!!

Post 684741 by MoleT-5R on 2014-01-27 09:56:50

[QUOTE=oblark;684735]I`ll try that tonight when i get home :) inlet retard 4 degrees and exhaust advance 5 degrees (hopefully these enough movement in the cam slots) :)[/QUOTE] but if you are measuring the degrees on the cam when you adjust it, as your pics the other day http://www.vpcuk.org/forums/showthread.php?54351-How-to-setup-N-A-cams-in-a-850-T5, won't the amount of adjustment need to be halved as it is measured as crankshaft movement. 2 degs adjustment on the cam would equal 4 degs at the crank as far as i see it

Post 684745 by oblark on 2014-01-27 10:04:07

[QUOTE=MoleT5-R;684741]but if you are measuring the degrees on the cam when you adjust it, as your pics the other day http://www.vpcuk.org/forums/showthread.php?54351-How-to-setup-N-A-cams-in-a-850-T5, won't the amount of adjustment need to be halved as it is measured as crankshaft movement. 2 degs adjustment on the cam would equal 4 degs at the crank as far as i see it[/QUOTE] I`m under the impression from what I`ve read on other forum that the degrees the cam shaft needs to be advanced/retarded are measured on the camshaft :) As in the photo`s in this thread http://volvospeed.com/vs_forum/topic/142294-using-ipds-prototype-cam-gear-adjustment-tool

Post 684747 by artfulflounder on 2014-01-27 10:23:44

[QUOTE=oblark;684738]With this and the M4.4 remapping my brain is getting a real hammering :)[/QUOTE] Good to see you getting stuck in.......useful threads like these could do with being stickied for reference.

Post 684750 by smithy on 2014-01-27 10:39:49

I had n/a cams in my v70 2.5t and timed them straight with no probs but I was running lower compression. But the car ran fine and pulled very well

Post 684751 by jamesy12345 on 2014-01-27 10:45:14

[QUOTE=MoleT5-R;684741]but if you are measuring the degrees on the cam when you adjust it, as your pics the other day http://www.vpcuk.org/forums/showthread.php?54351-How-to-setup-N-A-cams-in-a-850-T5, won't the amount of adjustment need to be halved as it is measured as crankshaft movement. 2 degs adjustment on the cam would equal 4 degs at the crank as far as i see it[/QUOTE] see point 6 in the link below http://www.ipdusa.com/files/product/321/PI%20401%20CAM%20TIMING%20TOOL%20INSTRUCTIONS.PDF that agrees with what you are saying

Post 684752 by MoleT-5R on 2014-01-27 10:45:35

[QUOTE=oblark;684745]I`m under the impression from what I`ve read on other forum that the degrees the cam shaft needs to be advanced/retarded are measured on the camshaft :) As in the photo`s in this thread http://volvospeed.com/vs_forum/topic/142294-using-ipds-prototype-cam-gear-adjustment-tool[/QUOTE] Cheers Rob, very useful link

Post 684754 by MoleT-5R on 2014-01-27 10:52:10

[QUOTE=jamesy12345;684751]see point 6 in the link below http://www.ipdusa.com/files/product/321/PI%20401%20CAM%20TIMING%20TOOL%20INSTRUCTIONS.PDF that agrees with what you are saying[/QUOTE] so it's as clear as mud this timing minefield.....lol but from what I've read Rob has timed his right as far as I can see, but is just concerned by the amount of overlap

Post 684755 by jamesy12345 on 2014-01-27 10:58:44

[QUOTE=MoleT5-R;684754]so it's as clear as mud this timing minefield.....lol but from what I've read Rob has timed his right as far as I can see, but is just concerned by the amount of overlap[/QUOTE] Yep total confusion :) My plan was just put them in at standard and adjust away from that (assuming it would run and the valves didn't hit the pistons!!)

Post 684911 by oblark on 2014-01-27 21:18:05

So I`ve now set the cams as per the Ipd spec :) Inlet :- [I]So if a non turbo intake camshaft were to be used in a turbocharged engine, and the same overlap were desired, then the intake cam would need to be retarded by 4 degrees from the factory base setting.[/I] Exhaust :- [I]So to maintain the same overlap, a non turbo exhaust cam in a turbocharged engine would need to be advanced 5 degrees from the factory base setting.[/I] The results of this is that the overlap between the exhaust valves and inlet valves is next to nothing, also the exhaust valves are almost closed as the piston comes up to the second TDC. [I]Generally turbocharged engines will have very little overlap. Overlap is defined as the period where the exhaust and intake valves are open at the same time during the exhaust stroke. In most instances turbocharged engines will perform best with minimal overlap. To reduce overlap, advance the exhaust cam and retard the intake came. For more overlap, retard the exhaust cam and advance the intake cam. Certain engine modifications to turbocharged cars can create a situation where more overlap can be desirable. These modifications are generally anything that effects exhaust back pressure or intake restriction. For instance; larger turbocharger, higher flowing downpipe and cat back exhaust or higher flowing intakes, intercoolers, or porting/polishing of the intake manifold[/I] The conclusion of this, there is no set timing for N/A cams in a T5 it`s down to the state of tune of the engine.

Post 684935 by Volvostorm on 2014-01-27 22:23:23

Interesting reading, I have Piper V5BP270H in mine, timed to stock settings, I wonder if I should retime mine. http://www.pipercams.co.uk/pipercams/www/product_nav.php?type=C&cat=CM&man=29&engine=227

Post 684969 by MoleT-5R on 2014-01-28 00:31:49

[QUOTE=oblark;684911]So I`ve now set the cams as per the Ipd spec :) Inlet :- [I]So if a non turbo intake camshaft were to be used in a turbocharged engine, and the same overlap were desired, then the intake cam would need to be retarded by 4 degrees from the factory base setting.[/I] Exhaust :- [I]So to maintain the same overlap, a non turbo exhaust cam in a turbocharged engine would need to be advanced 5 degrees from the factory base setting.[/I] The results of this is that the overlap between the exhaust valves and inlet valves is next to nothing, also the exhaust valves are almost closed as the piston comes up to the second TDC. [I]Generally turbocharged engines will have very little overlap. Overlap is defined as the period where the exhaust and intake valves are open at the same time during the exhaust stroke. In most instances turbocharged engines will perform best with minimal overlap. To reduce overlap, advance the exhaust cam and retard the intake came. For more overlap, retard the exhaust cam and advance the intake cam. Certain engine modifications to turbocharged cars can create a situation where more overlap can be desirable. These modifications are generally anything that effects exhaust back pressure or intake restriction. For instance; larger turbocharger, higher flowing downpipe and cat back exhaust or higher flowing intakes, intercoolers, or porting/polishing of the intake manifold[/I] The conclusion of this, there is no set timing for N/A cams in a T5 it`s down to the state of tune of the engine.[/QUOTE] so there is still room for experimentation with the overlap period, especially when flow restrictions have been removed, will need some dyno runs to back up different settings, but it is unfortunate that the settings will be slightly different for each of our engines as they all vary in their state of tune and supporting mods, but I'm guessing that the IPD timing settings are a happy medium somewhere in the middle

Post 684977 by jamesy12345 on 2014-01-28 02:48:17

[QUOTE=oblark;684911]So I`ve now set the cams as per the Ipd spec :)..... The conclusion of this, there is no set timing for N/A cams in a T5 it`s down to the state of tune of the engine.[/QUOTE] [QUOTE=MoleT5-R;684969]so there is still room for experimentation with the overlap period, especially when flow restrictions have been removed, will need some dyno runs to back up different settings, but it is unfortunate that the settings will be slightly different for each of our engines as they all vary in their state of tune and supporting mods, but I'm guessing that the IPD timing settings are a happy medium somewhere in the middle[/QUOTE] That's it now maybe you can run the car for a while, get used to how it feels or log some data/have a go on a dyno, then increase the overlap gradually to see what position get the best out of your set up.

Post 685023 by 960kg on 2014-01-28 09:45:36

Just to try and understand myself....... This is what i don`t get: Read the lift of the cams stated and compare them to the Volvo chart.......so if the cam lift in the chart for B5234T* is higher than this quote why fit N/A cams where the Exhaust Cam lift is less? According to all the figures the only cam that surely wants changing for more lift is the Inlet Cam! Also hears another thought ......what happens if one puts a 2.4 engine camshaft with the longer stroke into the B5234T with the shorter stroke...is the overlap vastly wrong because the piston travels further but the cams are still turning at the same speed?? [B]T5 Intake:242 duration 7,95 lift Exhaust:243.5 duration 7,95 lift N/A Intake:250 duration 8,45mm lift Exhaust:252.6 duration 8,45mm lift Piper Intake: 248 duration 8,84mm lift Exhaust:248 duration 7,87mm lift[/B] .....................................................

Post 685029 by MoleT-5R on 2014-01-28 10:09:17

[QUOTE=960kg;685023]Just to try and understand myself....... This is what i don`t get: Read the lift of the cams stated and compare them to the Volvo chart.......so if the cam lift in the chart for B5234T* is higher than this quote why fit N/A cams where the Exhaust Cam lift is less? According to all the figures the only cam that surely wants changing for more lift is the Inlet Cam! Also hears another thought ......what happens if one puts a 2.4 engine camshaft with the longer stroke into the B5234T with the shorter stroke...is the overlap vastly wrong because the piston travels further but the cams are still turning at the same speed?? [B]T5 Intake:242 duration 7,95 lift Exhaust:243.5 duration 7,95 lift N/A Intake:250 duration 8,45mm lift Exhaust:252.6 duration 8,45mm lift Piper Intake: 248 duration 8,84mm lift Exhaust:248 duration 7,87mm lift[/B] .....................................................[/QUOTE] stroke length would make no difference to timing, you will have altered nothing timing wise only length that the piston will travel, You could have what ever stroke you like, it will still have completed all it's travelling in the same 360 deg period, but see your point with the piper cams less exhaust lift and a shorter duration and costing a lot more than some cams out of an N/A

Post 685036 by jamesy12345 on 2014-01-28 10:26:21

Post 685047 by Volvostorm on 2014-01-28 11:03:04

[QUOTE=MoleT5-R;685029]stroke length would make no difference to timing, you will have altered nothing timing wise only length that the piston will travel, You could have what ever stroke you like, it will still have completed all it's travelling in the same 360 deg period, but see your point with the piper cams less exhaust lift and a shorter duration and costing a lot more than some cams out of an N/A[/QUOTE] Thats true about the Pipers, I wonder why they open for less duration than the N/A's? I know they are regrinds Might explain why my car runs so smooth, even with 'fast road' cam profiles

Post 685049 by MoleT-5R on 2014-01-28 11:11:36

[QUOTE=Pault5estate;685047]Thats true about the Pipers, I wonder why they open for less duration than the N/A's? I know they are regrinds Might explain why my car runs so smooth, even with 'fast road' cam profiles[/QUOTE] probably a trade off between performance and tidy tick over in traffic

Post 685057 by Volvostorm on 2014-01-28 11:32:26

Thing is, I wanted the rough lumpy tickover! :D

Post 685059 by MoleT-5R on 2014-01-28 12:01:50

[QUOTE=Pault5estate;685057]Thing is, I wanted the rough lumpy tickover! :D[/QUOTE] longer duration and higher lift required then sir

Post 685060 by Volvostorm on 2014-01-28 12:04:02

That means getting a custom grind done. Something to think about in the future I guess! ;)

Post 685082 by 960kg on 2014-01-28 14:06:25

[QUOTE=Pault5estate;685060]That means getting a custom grind done. Something to think about in the future I guess! ;)[/QUOTE] Bob Fry of Kent Cams is a friend of mine who lives just up the road from me and his factory is in Folkestone Kent ....i noticed also that Piper Cams is Folkestone!!!!! You will get a good Grind from Kent Cams through an agent.