Valve overlap.......

[oblark]

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 ?

[MoleT-5R]

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 ?

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

[jamesy12345]

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

[oblark]

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.

[jamesy12345]

From the IPD website......

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.

http://www.ipdusa.com/products/7047/115377-cam-timing-tool

[MoleT-5R]

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.


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

[jamesy12345]

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…….

[oblark]

From the IPD website......

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.

http://www.ipdusa.com/products/7047/115377-cam-timing-tool

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) :)

[MoleT-5R]

From the IPD website......

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.

http://www.ipdusa.com/products/7047/115377-cam-timing-tool

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

[jamesy12345]

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) :)

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 :)

[oblark]

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

[jamesy12345]

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

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!!!!!!!!!

[MoleT-5R]

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) :)

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

[oblark]

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

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

[artfulflounder]

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

Good to see you getting stuck in.......useful threads like these could do with being stickied for reference.

[smithy]

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

[jamesy12345]

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

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

[MoleT-5R]

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

Cheers Rob, very useful link

[MoleT-5R]

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

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

[jamesy12345]

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

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!!)

[oblark]

So I`ve now set the cams as per the Ipd spec :)

Inlet :- 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.

Exhaust :- 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.

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.

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

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.

[Volvostorm]

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

[MoleT-5R]

So I`ve now set the cams as per the Ipd spec :)

Inlet :- 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.

Exhaust :- 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.

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.

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

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.

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

[jamesy12345]

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.


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

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.

[960kg]

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??


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

.................................................. ...

[MoleT-5R]

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??


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

.................................................. ...

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

[jamesy12345]

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!
.....

960kg, I think your numbers are referring to the T3 engine etc from 2001 on, all I can see on the net is matching with Oblark's numbers in post #4

[Volvostorm]

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

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

[MoleT-5R]

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

probably a trade off between performance and tidy tick over in traffic

[Volvostorm]

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

[MoleT-5R]

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

longer duration and higher lift required then sir

[Volvostorm]

That means getting a custom grind done.

Something to think about in the future I guess! ;)

[960kg]

That means getting a custom grind done.

Something to think about in the future I guess! ;)


Bob Fry of Kent Cams (http://www.motorsportworld.co.uk/frame-detail.asp?PAGE=/kent-cams.htm) 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.

[Volvostorm]

Its only Piper that list anything for the 5 pot, Kent on there website don't do anything Volvo!

[MoleT-5R]

Its only Piper that list anything for the 5 pot, Kent on there website don't do anything Volvo!

having thought about the pipers duration whilst at work, the duration may be shorter but the grind may bring the lift in faster