BMW and Toyota tie-up for new Supra?

[sdistc]

A lot of it is down to packaging and homologation too - there's a huge amount of investment needed for high-volume engine manufacture and so it makes sense to use powerplants also used in road cars, and in many race series it's a regulation.

 

So do you think, that with Toyota's insider knowledge of the Subaru boxer, that we might see an entirely new boxer motor appearing in Toyota's lineup? Or, given the pragmatic considerations, we would only ever see a new Subaru motor (but potentially with Toyota fingerprints on it, like the new direct injection system)?

[Digsy]

So do you think, that with Toyota's insider knowledge of the Subaru boxer, that we might see an entirely new boxer motor appearing in Toyota's lineup? Or, given the pragmatic considerations, we would only ever see a new Subaru motor (but potentially with Toyota fingerprints on it, like the new direct injection system)?

 

 

I thought the GT86 engine already had Toyota's latest DI system on it, or have they got a newer one coming out?

[Gaz6002]

So do you think, that with Toyota's insider knowledge of the Subaru boxer, that we might see an entirely new boxer motor appearing in Toyota's lineup? Or, given the pragmatic considerations, we would only ever see a new Subaru motor (but potentially with Toyota fingerprints on it, like the new direct injection system)?

 

I can't see an all-new Boxer from Toyota personally. Subaru has sort of built a reputation around Boxer engines whereas Toyota has no reason to look into it.

 

If there's another sports car coming from Toyota, my guess would be similar to my original post - a BMW powerplant but with Toyota's racing hybrid system.

 

- - - Updated - - -

 

I thought the GT86 engine already had Toyota's latest DI system on it, or have they got a newer one coming out?

 

Yep, it's using the D4-D system already.

[Digsy]

As well as the packaging and low center of gravity advantages, Boxer 4 engines have slightly better vibration characteristics than inline 4's. That is vibration as in what is felt externally rather than internal balance to make it "revvy". I.e. they are in theory slightly more refined. This is not true of flat 4 engines, which are worse for vibration than inline 4's.

 

Their big downside is cost. They have the component count of a V configuration but they don't add enough "bang per buck" to justify it compared to a more conventional inline 4 layout, and I'll take a guess that this is a big factor in why they don't appear in more cars.

[Scott]

I always thought boxer engine WAS a flat 4?

[Digsy]

I always thought boxer engine WAS a flat 4?

 

All boxer engines are flat, but not all flat engines are boxers.

 

A flat engine has both banks opposite each other (a "180 degree V" if you like). In a flat engine you have two con rods on one crank throw, so when one piston is at TDC the other piston is at BDC. On a boxer engine each rod has its own crank throw, so that pairs of pistons are at TDC and BDC together. The piston motion is supposed to be analagous to a boxer's fists, but I've yet to see a boxer throw a punch with his left and right simultaneously

Edited September 6, 2013 by Digsy (see edit history)

[Scott]

All boxer engines are flat, but not all flat engines are boxers.

 

A flat engine has both banks opposite each other (a "180 degree V" if you like). In a flat engine you have two con rods on one crank throw, so when one piston is at TDC the other piston is at BDC. On a boxer engine each rod has its own crank throw, so that pairs of pistons are at TDC and BDC together. The piston motion is supposed to be analagous to a boxer's fists, but I've yet to see a boxer throw a punch with his left and right simultaneously

 

 

Great diagram, cheers

 

So with a flat 4 pistons 1 & 4 are in the same position, same with 2 & 3, but with the boxer they will be paired 1 & 2 and 3 & 4? I'm surprised that makes any difference to vibration.

[Digsy]

In the flat engine you have two piston and rod masses moving from left to right at one end of the engine and two more masses moving from right to left at the other end. These two opposite motions create a couple which tries to rotate the whole engine around its centre of mass. The bigger the piston / rod mass and the more seperation between the cylinders the bigger the couple. In a boxer engine there are two smaller couples which almost cancel each other out.

 

The thing about these couples are they occur at engine speed - what we call first order. First order vibrations are bad because they are relatively low frequency and can induce resonances in other engine parts like brakets, heatshields and even heavier items like alternators and AC compressors, causing them to fail. They can also be felt or heard by the driver.

 

I said above that in a boxer engine the first order couples almost cancel each other out. In practise they don't because the motion of the piston that is coming up the bore is slightly different to that of the piston going down the other bore. Therefore instead of cancelling out toally you still get a residual couple. The good thing about this couple is that it is small, and also it occurs two times per crank revolution. Thus it occurs at double the frequency of the larger couple present in the flat engine. It is therefore much easier to design around.

[Nodalmighty]

£40k budget, what high performance road car would you buy then?

 

Audi RS6 V10 TT Avant. 577bhp stock.

 

Lyndon.

[Scott]

In the flat engine you have two piston and rod masses moving from left to right at one end of the engine and two more masses moving from right to left at the other end. These two opposite motions create a couple which tries to rotate the whole engine around its centre of mass. The bigger the piston / rod mass and the more seperation between the cylinders the bigger the couple. In a boxer engine there are two smaller couples which almost cancel each other out.

 

The thing about these couples are they occur at engine speed - what we call first order. First order vibrations are bad because they are relatively low frequency and can induce resonances in other engine parts like brakets, heatshields and even heavier items like alternators and AC compressors, causing them to fail. They can also be felt or heard by the driver.

 

I said above that in a boxer engine the first order couples almost cancel each other out. In practise they don't because the motion of the piston that is coming up the bore is slightly different to that of the piston going down the other bore. Therefore instead of cancelling out toally you still get a residual couple. The good thing about this couple is that it is small, and also it occurs two times per crank revolution. Thus it occurs at double the frequency of the larger couple present in the flat engine. It is therefore much easier to design around.

 

Great explanation, thanks again

[Digsy]

I need to make a correction to what I wrote above. Lower frequency vibrations are EASIER to deal with than higher ones. The reason that the second order vibrations in the boxer engine are better than the first order in the flat is because the magnitude is smaller.

[Scott]

I need to make a correction to what I wrote above. Lower frequency vibrations are EASIER to deal with than higher ones. The reason that the second order vibrations in the boxer engine are better than the first order in the flat is because the magnitude is smaller.

 

Believe it or not, I knew that. Just guessed you had them mixed up

[j_jza80]

Audi RS6 V10 TT Avant. 577bhp stock.

 

Lyndon.

 

I've heard 700hp is possible with nothing more than a decat and remap. Yikes!

[JamieP]

Audi RS6 V10 TT Avant. 577bhp stock.

 

Lyndon.

 

I bet you ain't been out in one? They are not all that, not what id call a high performance road car anyway, feels like a nippy people carrier and handles like one, you can hardly feel the turbos, they must be tiny, it's not that quick either.

[sdistc]

I can't see an all-new Boxer from Toyota personally. Subaru has sort of built a reputation around Boxer engines whereas Toyota has no reason to look into it.

 

If there's another sports car coming from Toyota, my guess would be similar to my original post - a BMW powerplant but with Toyota's racing hybrid system.

 

Yep, it's using the D4-D system already.

 

Sorry, I was unclear.

I was basically suggesting that if the boxer is the "best" motor type for sports cars, why don't Toyota produce them - especially now that they have seen inside the Subaru's?

 

As well as the packaging and low center of gravity advantages, Boxer 4 engines have slightly better vibration characteristics than inline 4's. That is vibration as in what is felt externally rather than internal balance to make it "revvy". I.e. they are in theory slightly more refined. This is not true of flat 4 engines, which are worse for vibration than inline 4's.

 

Their big downside is cost. They have the component count of a V configuration but they don't add enough "bang per buck" to justify it compared to a more conventional inline 4 layout, and I'll take a guess that this is a big factor in why they don't appear in more cars.

 

Again, this would seem to me to be a very good pragmatic reason for a company like Toyota that is quite aware of cost to benefit ratio.. but startup costs aside, if the boxer has so many advantages, surely it is a good investment?

[wile e coyote]

Here you go nice flat 12 out of the Ferrari

[Digsy]

Again, this would seem to me to be a very good pragmatic reason for a company like Toyota that is quite aware of cost to benefit ratio.. but startup costs aside, if the boxer has so many advantages, surely it is a good investment?

 

I think the key there is "so many advatnages". Boxer engines have some advantages, but I don't think they have enough advantages. The vibrations of a large displacement inline 4 are only slightly worse and (and usually are) addressed through the addition of balance shafts, and how many everyday drivers are so close to the edge that they would notice the centre of gravity changing by a few cm vertically? I think justifying a flat engine in intangible terms like handling versus something as tangible as cost might be very hard. Its a nice way to get a low bonnet line in a small car while keeping to the predestrian impact regulations, though.

 

Also, if you want to turbocharge one and get a good spool up because of the firing order you would need a manifold with crossover pipes to keep the pulses from adajacent cylinders 180 crank degrees apart (clicky). Realtively easy to do with an inline 4, but a bit harder on a flat engine.

[sdistc]

I think the key there is "so many advatnages". Boxer engines have some advantages, but I don't think they have enough advantages. The vibrations of a large displacement inline 4 are only slightly worse and (and usually are) addressed through the addition of balance shafts, and how many everyday drivers are so close to the edge that they would notice the centre of gravity changing by a few cm vertically? I think justifying a flat engine in intangible terms like handling versus something as tangible as cost might be very hard. Its a nice way to get a low bonnet line in a small car while keeping to the predestrian impact regulations, though.

 

Also, if you want to turbocharge one and get a good spool up because of the firing order you would need a manifold with crossover pipes to keep the pulses from adajacent cylinders 180 crank degrees apart (clicky). Realtively easy to do with an inline 4, but a bit harder on a flat engine.

 

This has been precisely my point all along: it seems to my elementary logic that the Boxer motor *isn't* that great if it's not the first choice of high performance car manufacturers (for whatever reason, be it cost, packaging, ease of turbocharging etc).

[Digsy]

This has been precisely my point all along: it seems to my elementary logic that the Boxer motor *isn't* that great if it's not the first choice of high performance car manufacturers (for whatever reason, be it cost, packaging, ease of turbocharging etc).

 

I'd broadly agree with that but replace "high performance" with "almost any". But its horses for courses. If you decide early on that you are going to go absolutely all-out for a low centre of gravity and stuff everything else, then a flat engine is the obvious choice. However I rather suspect that what happened with the GT86 is that Subaru said the engine had to be a boxer because Subaru's have boxer engines, end of. I can't think of a really good reason why Toyota would have suddenly decided to design one when they have a perfectly good range of modern I4s already. I guess it will be telling if they use it in their "own" vehicles going forward.

 

Many years ago I did some work on a job once where a company wanted to use the old Subaru SVX engine in a high tech MPV purely for the reason that they percieved that boxer 6 engines were sexy (through their association with Porsche).

Edited September 10, 2013 by Digsy (see edit history)

[tbourner]

All boxer engines are flat, but not all flat engines are boxers.

 

A flat engine has both banks opposite each other (a "180 degree V" if you like). In a flat engine you have two con rods on one crank throw, so when one piston is at TDC the other piston is at BDC. On a boxer engine each rod has its own crank throw, so that pairs of pistons are at TDC and BDC together. The piston motion is supposed to be analagous to a boxer's fists, but I've yet to see a boxer throw a punch with his left and right simultaneously

 

So do you get flat twin bike engines? Or are they all boxers? I would imagine a flat twin would be very unbalanced?