Calling Max_Torque - manifolds and turbos question

[Evoluzione]

When Honda put so much into the design of this engine and it worked so well, you do wonder how much of the geometry of it should just stay the same. From a dimensional viewpoint unless there is a packaging need to change it i'd be pretty much keeping it as it was, just lower CR and different materials etc.

[anonymous-user]

227bhp said:

Max_Torque said:

227bhp said:

There is very little chance of reversion on this engine, it's VTEC.

What has "VTEC" got to do with anything? You have, for a typical road sized turbine, EBP at around 2 to 3 times IMP, so "reversion" is un-avoidable.

I explained it there:

227bhp said:

There is very little chance of reversion on this engine, it's VTEC. Reversion happens at low engine speed with long duration/tight LSA cams, they won't be so at low rpm.

Without using obscure terminology to put you off the scent.

To explain further:
Reversion happens with long overlap, long duration cams at low rpm. The Vtec system adjusts the cams duration, overlap and lift so you don't get that effect at low rpm, low rpm being where it occurs, not high rpm.
High rpm is where the high speed lobes come in (longer duration, higher lift, more overlap) and reversion isn't a problem.

Is that easier for you to understand?

No, sorry, that's no easier to understand.

Consider the pressures in an N/A engine across the Exhaust valve opening action:

At EVO, in cylinder pressure is, typically, 10 to 20 bar, Exhaust Back pressure is, typically 0.5 bar or less. A sudden and turbulent initial blow down pulse occurs with a choked (M1.0) valve throat, and continues for some time, before the piston starts moving upwards to exhaust the chamber. At some point, in cylinder pressure falls, and un-chokes the valve throat. Then, as the in cylinder pressure falls to the same pressure as the exhaust, all flow stops. At this point, a dynamic pressure pulse can continue exhaust flow, or, impede it, no matter what the state of the intake valve is

On a turbo charged engine, the EBP is typically, 2 or 3 times higher than the intake manifold presure, and the engines pressure ratio is degraded compared to a similar N/A engine. hence, the cylinder volume is significantly greater when pressures equalise, and the piston then must do more positive work towards the end of the exhaust stroke to continue to evacuate the cylinder. During this period, a non symetrical exhaust port discharge characteristic is desirable, to prevent as much as possible, any reversal of flow.

[stevieturbo]

Max_Torque said:

On a turbo charged engine, the EBP is typically, 2 or 3 times higher than the intake manifold presure

I've only tested a handful of engines, and certainly none have ever reached those sort of levels.

My own is pretty much 1:1 at almost all times. Worst I tested hit around 1.8:1 although I've never tested an OEM turbo setup.

[227bhp]

stevieturbo said:

Max_Torque said:

On a turbo charged engine, the EBP is typically, 2 or 3 times higher than the intake manifold presure

I've only tested a handful of engines, and certainly none have ever reached those sort of levels.

My own is pretty much 1:1 at almost all times. Worst I tested hit around 1.8:1 although I've never tested an OEM turbo setup.

No that depends where and at what time you measure it.

[stevieturbo]

227bhp said:

No that depends where and at what time you measure it.

Pre turbine close to the turbine, and throughout all boost/rpm ranges of course.

[227bhp]

stevieturbo said:

227bhp said:

No that depends where and at what time you measure it.

Pre turbine close to the turbine, and throughout all boost/rpm ranges of course.

No I mean where he's talking about measuring it, he mentions Mach1, so it's probably in the exhaust port. It varies throughout the cycle, it's not constant.
O/T, but measuring cylinder pressure is very revealing, the equipment is a bit expensive though! If you can interpret it and use it properly it's very valuable info to have.

Edited by 227bhp on Monday 19th December 04:46

[227bhp]

Max_Torque said:

No, sorry, that's no easier to understand.

Consider the pressures in an N/A engine across the Exhaust valve opening action:

At EVO, in cylinder pressure is, typically, 10 to 20 bar, Exhaust Back pressure is, typically 0.5 bar or less. A sudden and turbulent initial blow down pulse occurs with a choked (M1.0) valve throat, and continues for some time, before the piston starts moving upwards to exhaust the chamber. At some point, in cylinder pressure falls, and un-chokes the valve throat. Then, as the in cylinder pressure falls to the same pressure as the exhaust, all flow stops. At this point, a dynamic pressure pulse can continue exhaust flow, or, impede it, no matter what the state of the intake valve is

On a turbo charged engine, the EBP is typically, 2 or 3 times higher than the intake manifold pressure, and the engines pressure ratio is degraded compared to a similar N/A engine. hence, the cylinder volume is significantly greater when pressures equalise, and the piston then must do more positive work towards the end of the exhaust stroke to continue to evacuate the cylinder. During this period, a non symmetrical exhaust port discharge characteristic is desirable, to prevent as much as possible, any reversal of flow.

None of that would happen if the ex valve was closed early enough. What you have identified there is a constant RPM engine with a poorly specified ex cam. In real life it's far from that simplistic, everything varies wildly throughout the rev range with a fixed cam, even more so with VTEC.
VTEC effectively stops flow reversal by closing the ex valve at the correct time at low rpm, it then opens it for longer at high rpm.
Anyhow, I can see i'm banging my head against a brick wall here, so that's all from me for now.

[anonymous-user]

227bhp said:

None of that would happen if the ex valve was closed early enough.

You are correct. Shutting the exhaust valve "early" does indeed prevent any flow reversion. Unfortunately, it also stops ANY flow what so ever! Far better to design the exhaust flow line to continue to positively scavenge the cylinder down below EBP, keep the Exh valve open, and reduced internal EGR, and with that reduction in residuals, pick up a free lunch from higher manifold volumetric efficiency and be able to run closer to MBT due to a lower charge temperature at IVC. Which is probably why i've got championship winning F1, WRC, and Touring car engines to my name, and you got, er what exactly?

VTEC is irrelevant, it's just a variable cam drive, like lots of other systems that can phase the valve events to optimise gas exchange vs speed and load. In all cases, the better your base engine aerodynamics, the more CAM duration / overlap you can run, and the more power you can make.............

[sl0wlane]

^ see above for reason why I asked Max_Torque for comment and not the PH clicky crew

Thanks again for the help Max, I'll be back with measurements as this finally turned up:

Edited by sl0wlane on Monday 19th December 19:38

[227bhp]

Max_Torque said:

You are correct. Shutting the exhaust valve "early" does indeed prevent any flow reversion. Unfortunately, it also stops ANY flow what so ever! Far better to design the exhaust flow line to continue to positively scavenge the cylinder down below EBP, keep the Exh valve open, and reduced internal EGR, and with that reduction in residuals, pick up a free lunch from higher manifold volumetric efficiency and be able to run closer to MBT due to a lower charge temperature at IVC. Which is probably why i've got championship winning F1, WRC, and Touring car engines to my name, and you got, er what exactly?

VTEC is irrelevant, it's just a variable cam drive, like lots of other systems that can phase the valve events to optimise gas exchange vs speed and load. In all cases, the better your base engine aerodynamics, the more CAM duration / overlap you can run, and the more power you can make.............

One can only assume your place on any design team was to serve coffee and biscuits, it certainly wasn't cam design. There won't be many on here who can smell it, but I can.
The only thing it looks like you might have put your name to is in readers cars and it remains unfinished.

[anonymous-user]

227bhp said:

Max_Torque said:

You are correct. Shutting the exhaust valve "early" does indeed prevent any flow reversion. Unfortunately, it also stops ANY flow what so ever! Far better to design the exhaust flow line to continue to positively scavenge the cylinder down below EBP, keep the Exh valve open, and reduced internal EGR, and with that reduction in residuals, pick up a free lunch from higher manifold volumetric efficiency and be able to run closer to MBT due to a lower charge temperature at IVC. Which is probably why i've got championship winning F1, WRC, and Touring car engines to my name, and you got, er what exactly?

VTEC is irrelevant, it's just a variable cam drive, like lots of other systems that can phase the valve events to optimise gas exchange vs speed and load. In all cases, the better your base engine aerodynamics, the more CAM duration / overlap you can run, and the more power you can make.............

One can only assume your place on any design team was to serve coffee and biscuits, it certainly wasn't cam design. There won't be many on here who can smell it, but I can.
The only thing it looks like you might have put your name to is in readers cars and it remains unfinished.

LOLZ!

[Mr2Mike]

227bhp said:

None of that would happen if the ex valve was closed early enough.

Closing the exhaust valve early will increase the amount and pressure of exhaust gasses remaining in the cylinder. What do you think will happen when the inlet valve opens?

[227bhp]

Mr2Mike said:

227bhp said:

None of that would happen if the ex valve was closed early enough.

Closing the exhaust valve early will increase the amount and pressure of exhaust gasses remaining in the cylinder. What do you think will happen when the inlet valve opens?

Early compared to what? Taken out of context and with no accompanying figures your post is pretty pointless.
Closing the valve too early will give what you state, closing it at the correct time won't. That is what any variable valve events give us, the ability to close the valve to suit any engine speed, load etc.

For a 950rpm to 3000 rpm range which cam will work best and why?
A. 220 degree 8mm lift
B. 300 degree 12mm lift

Which will give the least reversion?

It's not difficult, it's basic Ladybird book of 'How engines work'.

Edited by 227bhp on Monday 26th December 05:53

[stevieturbo]

Work best for what and how/why/when are any duration and lift measurements taken ?

Although none are hardly relevant to the OP's manifold where he wants the best....yet uses an old single scroll turbo.
So not really sure best of what either.

[227bhp]

stevieturbo said:

Work best for what and how/why/when are any duration and lift measurements taken ?

Although none are hardly relevant to the OP's manifold where he wants the best....yet uses an old single scroll turbo.
So not really sure best of what either.

I did say 'best' quite purposely, I couldn't think of one single reason to use cam B in that rev range so best just covered everything.

[Gunt]

Have to say, i see why you wanted max powers imput not knowing who he is and never been on this forum before . but it seams your preset plans leave it a bit outside the optimum experiment you seamed first to want to go through .
I would love to be heading into your project , don't forget to bear in mind you are not starting with a predesigned engine for your purpose and you are modifying a OEM product greatly for your purpose , some body earlier recamended and praised std cams and as for your propose they will suffice but there are much better out there suited to your goal , but i wouldn't go as far as bragging about the millions spent developing the perfect cam , as at the time Honda were designing a cam for the future from when the car was launched that would give a sell-able bhp figure while complying with emissions and running with cat's meeting the forthcoming regs . Also note they are right v-tech is nothing relay at this point but I vtech is and that's going to be your bigger extra to almost every engine and usually banned in every form of racing , so i would only consider development data from some one used to these systems more .

on the cams see an interesting testing not for your engine but someone who was and it the best on that generation of engine

http://www.superstreetonline.com/features/sstp-100...

and below what i would consider a far better manifold , modify it a bit and let the throttle body fit on top and it might also help feed piping [ i cannot get the pic to paste ]

https://www.google.ie/imgres?imgurl=http%3A%2F%2Fi...

as before i would do 2 manifolds one at you length and the other at a little over half , most race engines are built to suit restrictions or class , but they never generally start out with what ou have and the one thing that is going to affect your car is the fact that your are starting with an engine far exceeding 100% ve and easily capable of 100% tq effiency in n/a trim

[stevieturbo]

Gunt said:

Have to say, i see why you wanted max powers imput not knowing who he is and never been on this forum before . but it seams your preset plans leave it a bit outside the optimum experiment you seamed first to want to go through .
I would love to be heading into your project , don't forget to bear in mind you are not starting with a predesigned engine for your purpose and you are modifying a OEM product greatly for your purpose , some body earlier recamended and praised std cams and as for your propose they will suffice but there are much better out there suited to your goal , but i wouldn't go as far as bragging about the millions spent developing the perfect cam , as at the time Honda were designing a cam for the future from when the car was launched that would give a sell-able bhp figure while complying with emissions and running with cat's meeting the forthcoming regs . Also note they are right v-tech is nothing relay at this point but I vtech is and that's going to be your bigger extra to almost every engine and usually banned in every form of racing , so i would only consider development data from some one used to these systems more .

on the cams see an interesting testing not for your engine but someone who was and it the best on that generation of engine

http://www.superstreetonline.com/features/sstp-100...

and below what i would consider a far better manifold , modify it a bit and let the throttle body fit on top and it might also help feed piping [ i cannot get the pic to paste ]

https://www.google.ie/imgres?imgurl=http%3A%2F%2Fi...

as before i would do 2 manifolds one at you length and the other at a little over half , most race engines are built to suit restrictions or class , but they never generally start out with what ou have and the one thing that is going to affect your car is the fact that your are starting with an engine far exceeding 100% ve and easily capable of 100% tq effiency in n/a trim

Whilst you are correct in observing the thread seems a pointless experiment in seeking optimum for a sub optimal set of restrictions in place.....the thread is also about exhaust manifold. Your entire post seems aimed at intake.

But all the same rules do apply...he is most certainly not re-inventing the wheel here. So with either intake or exhaust, there are already proven designs and technologies out there to assist with making the right design choice. Although in this case he seems to be opting for a lesser design of exhaust right from the outset

[Gunt]

agreed , only making the point you cannot try to design perfection in one area while generally taking the intake off the shelf , i'd love to see where his choice came on that product ,

getting back to the exhaust , id nearly view the engine as sections , intake 1/3 engine 1/3 exhaust 1/3 and putting them tgether to get the optimum out of a package .

sad to say this had great potential for data and unusually while striving for the best , using the best , hope it doesn't fall short , hope he at least grabs the tial v band exhaust housing

[stevieturbo]

Gunt said:

agreed , only making the point you cannot try to design perfection in one area while generally taking the intake off the shelf , i'd love to see where his choice came on that product ,

getting back to the exhaust , id nearly view the engine as sections , intake 1/3 engine 1/3 exhaust 1/3 and putting them tgether to get the optimum out of a package .

sad to say this had great potential for data and unusually while striving for the best , using the best , hope it doesn't fall short , hope he at least grabs the tial v band exhaust housing

Without hours of dyno testing, he will never find optimal it really is as simple as that. Unless optimal means something different. And as you say, all aspects need factored in, not just one part.

And a Tial housing wont matter much when he's still retaining a non twin scroll setup, although Tial do now offer divided V-band housings to allow people to build twin scroll setups. Unless a V-band actually benefits the install, they are hardly worth the extra money though.

[227bhp]

Gunt said:

on the cams see an interesting testing not for your engine but someone who was and it the best on that generation of engine

http://www.superstreetonline.com/features/sstp-100...

It's a shame there are no cam specs on that test, then it would have been useful.