The 2.4 MIVEC is a interference engine.....right?
The 2.4 MIVEC is a interference engine.....right?
I'm just wondering if the 2.4 mivec in our ralliarts is a interference engine. I assume so, but I may be wrong and that is why I'm asking. Given the choice I would perfer non interference, but I'm probably dreaming. So does anyone know for sure?
Interference / non-interference:
Basically its how far the valves are from the pistons. Basically the difference comes into play when a timing belt breaks. On a non-interference design, there is enough clearance between the pistons and valves to prevent damaging contact. An interference design does not have sufficient clearance between those parts and engine damage would result from a broken timing belt.
Basically its how far the valves are from the pistons. Basically the difference comes into play when a timing belt breaks. On a non-interference design, there is enough clearance between the pistons and valves to prevent damaging contact. An interference design does not have sufficient clearance between those parts and engine damage would result from a broken timing belt.
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The 4G69 is a small bore, long stoke design. Small bore engines are interference 99% of the time because there is very little area for the valves. Engineers try to compensate for this with longer lift on the valves.
BTW, it has a chain for the cams, not a belt. Belts will slip, a chain will not. Any slip on the cams could result in a valve meeting a piston.
Also, interference engines perform better.
The only advantage a non-interference engine has is high revs. I don't feel like doing a write-up, but trust me. At 12,000+ rpms, it helps.
BTW, it has a chain for the cams, not a belt. Belts will slip, a chain will not. Any slip on the cams could result in a valve meeting a piston.
Also, interference engines perform better.
The only advantage a non-interference engine has is high revs. I don't feel like doing a write-up, but trust me. At 12,000+ rpms, it helps.
Originally Posted by Tristar Racing
Interference / non-interference:
Basically its how far the valves are from the pistons. Basically the difference comes into play when a timing belt breaks. On a non-interference design, there is enough clearance between the pistons and valves to prevent damaging contact. An interference design does not have sufficient clearance between those parts and engine damage would result from a broken timing belt.
Basically its how far the valves are from the pistons. Basically the difference comes into play when a timing belt breaks. On a non-interference design, there is enough clearance between the pistons and valves to prevent damaging contact. An interference design does not have sufficient clearance between those parts and engine damage would result from a broken timing belt.
Damn good stuff man! Thanks for the info!
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Yeah, I thought it was, but I just wanted to make sure. I'm use to non-interference engines, but oh well. Good explinations on interference and non-interference; I should have explained when I posted originally. Thanks.
My understanding of this is that the DOHC being interference would cause the valves to be in a bad place on part of the engine if the belt was to snap.
Although sense the RA is a SOHC then this is not a problem. If the belt goes the pistons won't "interfere" with the valves.
Anybody correct m e if I'm wrong, but this was my understanding of this. The 1.8 engine in the 90-94 Eclipses was not interference because it was SOHC, although it had a close area between the valves and pistons.
Although sense the RA is a SOHC then this is not a problem. If the belt goes the pistons won't "interfere" with the valves.
Anybody correct m e if I'm wrong, but this was my understanding of this. The 1.8 engine in the 90-94 Eclipses was not interference because it was SOHC, although it had a close area between the valves and pistons.
What we really need here is some good engine specs. I'm assuming that the piston crowns flat with the block at tdc; so if someone knows if we have flat top pistons or valve reliefs and as had the head off the car we could know. If the valves fully opened don't contact the top of the piston at tdc were all set. I have seen a few engines that did this where the fully opened valves just missed the valve relifes. Anyway; were not gong to know until someone gets good specs or takes one of or engines apart and looks. On another note: Wouldn't it be kinda cool if when the lower rpm cam ratio is in effect the engines not interference and then when the mivec kicks in it becomes interference......it's certianly possable. 
Thats true; but the idea behind the MIVEC engine is that once over 3500 rpms the valves open further and the timeing is advanced (or at least thats how I think it works). So under that rpm the valves might have enough clearence because they don't open as far as when the mivec kicks in. All of this is speculiavive of course; but I still tink it's possable.
Ummm, I think that the MIVEC control on the valves is more in control of the duration of time the valve remains open that how far it opens. I MIGHT be wrong, but the valves dont open any further under MIVEC, just stay open longer under MIVEC. That and MIVEC has 2 hit points, not just 3500ish RPM, there is supposed to be another point somwhere in the 5000's.