Will The Elio Have An Interference Engine?

[2.ooohhh]

My ford zetec engine is non-interference and it has variable exhaust valve timing. I specifically sought a non-interference engine since my previous car (plymouth with an interference engine) died a premature death due to a timing belt failure with only 40k miles on the belt. I didn't do an autopsy but I assume the tensioner failed. It would be awesome if the elio was non-interference but using a chain opposed to an unreliable belt if it is an interference engine would be acceptable to me. I guess we'll have to wait and see what the final specs are on the engine. I thought just maybe, they had mentioned it somewhere that I had missed.

Some ztec engines are non interference, others are interference, depends on which cams and pistons are installed from the factory. While a US spec 2.0l focus engine is non interference, some of the race chassis I tinker with that are "powered by ztec" are interference due to higher lift cams and higher compression pistons. ztecs are easier to make non interference b/c they are DOHC allowing the valves to be installed into the heads and an angle and allowing longer duration on the cams without compromising compression.

 

[Triangles]

Interesting, I've never heard of any zetec being interference, but it makes sense if you custom build a race engine that it would be. My car is an Escort not a Focus. Interestingly the manual incorrectly says my engine is an interference engine. Not sure if this was an error or if it may have referred to the older SPI engines. Are there any factory stock zetecs that are interference?

 

[2.ooohhh]

Interesting, I've never heard of any zetec being interference, but it makes sense if you custom build a race engine that it would be. My car is an Escort not a Focus. Interestingly the manual incorrectly says my engine is an interference engine. Not sure if this was an error or if it may have referred to the older SPI engines. Are there any factory stock zetecs that are interference?

Well, that's a very complicated question, technically the motor I was working on was a factory interference engine supplied direct from (Ford EU) to Caterham. The zetec platform is distributed globally with both gas and diesel versions as well as dohc and sohc cylinder head variants in displacements from 1L-2.4L.(it gets around )

 

[goofyone]

Yes, due to the adjustable valve timing it is almost certainly an interference engine. Though the chain should alleviate any concerns in this area.

Hey Goofyone, could you ask your friend @ IAV if the Elio design is interference
or not?
View attachment 2218

At this time I do not have any information abut this being an interference engine however it would not surprise me if it is. What I can do is help clear up some confusion about variable valve timing. The fact of the matter is that this engine will have two-step variable LIFT and not variable valve timing. I had to go back and re-read the Tech Talks and discovered that Elio Motors has actually all along stated that this engine would feature variable valve lift and not variable valve timing.

In the very first Tech Talk IAV/Elio states that this engine will use 'two-step variable lift technology' and in Tech Talk v24 EM confirms that VVT will not be used in this engine. This information is further corroborated by the IAV/Elio demo engine spec sheet stating that 'switchable tappets' will be used as switchable tappets are specifically used to change lift. Switchable tappets are commonly used as one component of a VVT package however there is nothing to say they can not be used on their own. In the following rendering you can see how dual cam lobes, as shown in the Elio engine animation, can be used in combination with switchable tappets to provide two stage valve lift.

Tech Talk V1: http://us6.campaign-archive2.com/?u=24b371802c83d81776b06aa68&id=545e7f615f
Tech Talk V24: http://us6.campaign-archive1.com/?u=24b371802c83d81776b06aa68&id=4801365dc7

 

[2.ooohhh]

At this time I do not have any information abut this being an interference engine however it would not surprise me if it is. What I can do is help clear up some confusion about variable valve timing. The fact of the matter is that this engine will have two-step variable LIFT and not variable valve timing. I had to go back and re-read the Tech Talks and discovered that Elio Motors has actually all along stated that this engine would feature variable valve lift and not variable valve timing.

In the very first Tech Talk IAV/Elio states that this engine will use 'two-step variable lift technology' and in Tech Talk v24 EM confirms that VVT will not be used in this engine. This information is further corroborated by the IAV/Elio demo engine spec sheet stating that 'switchable tappets' will be used as switchable tappets are specifically used to change lift. Switchable tappets are commonly used as one component of a VVT package however there is nothing to say they can not be used on their own. In the following rendering you can see how dual cam lobes, as shown in the Elio engine animation, can be used in combination with switchable tappets to provide two stage valve lift.

Tech Talk V1: http://us6.campaign-archive2.com/?u=24b371802c83d81776b06aa68&id=545e7f615f
Tech Talk V24: http://us6.campaign-archive1.com/?u=24b371802c83d81776b06aa68&id=4801365dc7

While technically, for marketing, a dual profile cam to provide variable lift doesn't have to be enabling variable valve timing I've NEVER seen a production dual lift camshaft profile that was not also enabling a second valve timing as well as additional lift. Most often one timing profile is low lift and LONG duration while the second is comparatively very high lift and short duration. Valve timing in relation to the crank is measured from the centerline of the lobe. Often the "efficiency" cam profile is also set to slightly or very nearly overlap the exhaust valve timing. Meanwhile the high lift "performance" profile is centered several degrees before "efficiency" timing's centerline to give the valve time to close completely at high RPM. Now that isn't to say that Elio can't perfectly center both cam lobes, it's just not very likely, but since they are going for efficiency the lobe centerlines may be much closer than typical in a VVT setup. For example BMW utilized 30 degrees of intake cam timing swing on it's earliest vanos configurations, but I would be surprised if the difference in centerlines for the elio cam profiles are more than 8-10 degrees. ANY(even 1 degree) difference in centerline of the cam lobe between options would be considered mechanically variable valve timing, even if it's just A/B profiles 10 degrees apart.(very little cam timing adjustment by today's standards)

 

[goofyone]

While technically, for marketing, a dual profile cam to provide variable lift doesn't have to be enabling variable valve timing I've NEVER seen a production dual lift camshaft profile that was not also enabling a second valve timing as well as additional lift. Most often one timing profile is low lift and LONG duration while the second is comparatively very high lift and short duration. Valve timing in relation to the crank is measured from the centerline of the lobe. Often the "efficiency" cam profile is also set to slightly or very nearly overlap the exhaust valve timing. Meanwhile the high lift "performance" profile is centered several degrees before "efficiency" timing's centerline to give the valve time to close completely at high RPM. Now that isn't to say that Elio can't perfectly center both cam lobes, it's just not very likely, but since they are going for efficiency the lobe centerlines may be much closer than typical in a VVT setup. For example BMW utilized 30 degrees of intake cam timing swing on it's earliest vanos configurations, but I would be surprised if the difference in centerlines for the elio cam profiles are more than 8-10 degrees. ANY(even 1 degree) difference in centerline of the cam lobe between options would be considered mechanically variable valve timing, even if it's just A/B profiles 10 degrees apart.(very little cam timing adjustment by today's standards)

I completely agree that to accommodate the change in lift will also require a change in timing however I believe the people on here who actually understand what we are discussing also understand that two cam profiles allow for a timing variation along with the change in lift.

For everyone else it is just easier to say that this engine will not have variable valve timing as this is much easier than trying to explain how dual cam profiles work to someone who does not understand the workings of an internal combustion engine.

By the way we had a new member join today who has provided some very good insight into this engine:

The Elio will be using a dual lift or shifting hydraulic bucket on the intake. This allows for high and low lift based on engine RPM and load demands. There are three lobes per intake. Effectively the same system as Porsche uses as it's Variocam Plus System. As pointed out earlier in this post the bucket tappets are hydraulic. The integral cam cover with integral cam bores, would require a lot of tooling to allow the use of a shim style mechanical adjustment.
View attachment 2219
To clear up any doubt, the cams run in the parent aluminum of the camcover and cylinder head. This is a proven method in engine design for 35 plus years. It does require tighter design and manufacturing tolerances with today's lower viscosity oils.

Guys, thanks for the welcome. To add a bit more to the valvetrain discussion, I have it on good authority that VVT is not completely out of the picture. It will be employed if required once by the testing is completed and the engine does not meet targets. VVT systems are expensive and technology that will not make as much of a difference on this motor as it is already designed and maximized for mileage. If you look at the current design you can see there is space around the cam drive to add a cam phaser as well as cast features on the head to be machined for the placement of control solenoid.

 

[wheaters]

It's good to see some more factual information, otherwise all we have is speculation.

 

[Snick]

This has awakened my inner nerd. Good discussion, and I'm hoping EM hits the sweet spot of smooth, flat power delivery (no big gaps, holes, and have early rpm reserve power)...or in other words makes the motor very diesel-like.

BUT, I'll understand if cost prohibits it in generation 1.

Mr. Paul Elio, could you look at the feasibility of offering a more sophisticated power curve as an option? Raw HP doesn't matter nearly as much as the shape of the power curve. And I love, LOVE the option of OBD tuning. I've personally desoldered and replaced chips; it isn't that hard, but having OBD tuning capability expands the third party vendor market dramatically. All the performance chip tuning companies will love to have another car to tune, and they will generate positive buzz on the Elio, too, I think.

 

[Folks]

It's good to see some more factual information, otherwise all we have is speculation.

Speaking of factual information. Unless I missed your post somewhere you never answered my question; A photo of your Leigh had a caption referring to it being on an old logging trial. I did not know there was still logging going on in Briton. Yes or no.

 

[wheaters]

"Yes or no"? .....You sound just like my wife!

Not sure where Briton is.....but logging still goes on in Britain on a relatively small scale.

It's spelled "Liege", btw.