Jetta uses cylinder head from Lamborgini Gallardo

[Hokiefyd]

Originally Posted By: JHZR2
Yet it fits fine in the engine bay of the golf/rabbit, and there is no imbalance or harmonic. It isnt a screamer, but it does not have to be.

Why try to force every powerplant to look like a Honda? Id prefer to not have to take my engine to 5000 RPM every time to make full torque.

And we rarely, if ever, see 2.5L I4 engines for whatever reason. LOTS of 2.4L I4s though...


1) Yes, it fits. Would a 2.5L I-4 be more compact, allowing for more optimal placement or easier serviceability of things like serpentine drive belts? Perhaps.

2) Honda has nothing to do with this. Not sure why you brought that up. You don't have to take a Honda to 5,000 rpm to make peak torque anyway. My 2.4L makes peak torque at 4,200 rpm and the VW I-5 makes it at 4,250 rpm.

3) Yes, tons of 2.4-2.5L I-4s. That's my point: why are so many using the 4-cylinder architecture instead of the 5-cylinder architecture?

 

[JHZR2]

Well after 35k in the rabbit and a few hundred k in MB diesels, id say that the harmonics at other RPMs are really a non-issue.

 

[Quattro Pete]

Originally Posted By: Hokiefyd
My 2.4L makes peak torque at 4,200 rpm and the VW I-5 makes it at 4,250 rpm.

According to MSN Autos, your 2.4 makes peak torque at 4,400 rpm.

Also, I think you need to look at the overall torque curve, not just the peak, before drawing any conclusions. I haven't seen it for either of these engines, but I would expect the I5 curve to look somewhat smoother.

 

[Klutch9]

Originally Posted By: JHZR2
Yet it fits fine in the engine bay of the golf/rabbit, and there is no imbalance or harmonic. It isnt a screamer, but it does not have to be.

Why try to force every powerplant to look like a Honda? Id prefer to not have to take my engine to 5000 RPM every time to make full torque.

And we rarely, if ever, see 2.5L I4 engines for whatever reason. LOTS of 2.4L I4s though...


Ford/Mazda, Nissan, and Toyota all have a 2.5L I-4's. But I do agree with the fact that you do see quite a few more 2.4 I-4's than 2.5's, for whatever reason.

 

[rslifkin]

Keep in mind, peak numbers aren't everything. Area under the curve matters. Based on what people are saying on here, and how the 2.5 powered cars do compared to others (on pavement, not on paper), it probably has a pretty flat power curve.

 

[Vikas]

Anybody knows what is involved in replacing drive belts on this specific engine? There had been few Jetta models, where this job needed hours and hours. I still have a video which shows dropping the entire front end, evacuating A/C and draining the coolant, removing the radiator to replace the fan belts

You expect this type of maintenance on Lambo but not on VW :-(

- Vikas

 

[KrisZ]

Personally, having read this thread I also don't understand why so many people are bent out of shape about VW's I5 engine. It's just another way to make the car go.

VW makes it work well as a package, judging from reviews and personal feedback in this thread, so why complain about one aspect of that package just because it doesn't look good on paper?
The same people should also start criticizing Porsche for putting their engines in the worst place possible. It also looks bad on paper.

 

[Hokiefyd]

Originally Posted By: Quattro Pete
Originally Posted By: Hokiefyd
My 2.4L makes peak torque at 4,200 rpm and the VW I-5 makes it at 4,250 rpm.

According to MSN Autos, your 2.4 makes peak torque at 4,400 rpm.

Also, I think you need to look at the overall torque curve, not just the peak, before drawing any conclusions. I haven't seen it for either of these engines, but I would expect the I5 curve to look somewhat smoother.


MSN Autos must be showing the torque peak for a 2010-2011 CR-V with the K24Z6/Z8 engine, which is 4,400 rpm. The K24Z1/Z4 in the 2007-2009 CR-V makes it at 4,200 rpm.

I wasn't drawing any conclusions. I simply responded to the suggestion brought up by JHZR2 that you have to rev a Honda to 5000 rpm to get peak torque, because you don't. The Honda's peak torque is actually very close to the VW's peak torque at 4,250 rpm.

I'm sure VW's 2.5L I-5 makes great torque. I'd like to see a curve of it, and if a super-flat torque curve is the reason they did that, I'm fine with it.

I don't have any issue with them using 5 cylinders. I just wonder why.

 

[raaizin]

Originally Posted By: KrisZ
Personally, having read this thread I also don't understand why so many people are bent out of shape about VW's I5 engine. It's just another way to make the car go.

VW makes it work well as a package, judging from reviews and personal feedback in this thread, so why complain about one aspect of that package just because it doesn't look good on paper?
The same people should also start criticizing Porsche for putting their engines in the worst place possible. It also looks bad on paper.



I agree, as I am the original poster I was just pointing out what I thought was an interesting fact. A 20k car shares a significant component with a 200k car. Folk lets get one fact straight each car is a compromise. If the compromises work for you buy it and enjoy it. If it is not what you want, purchase what you desire. It would be pretty sad if we all drove same cars. Diversity in the marketplace keeps things interesting. Having said that the jetta works for us. My daughter really does not car about packaging efficiency, NVH, Max hp or torque

 

[07Wolfie]

The Honda K24 (2.4L I-4) can certainly be held as an example of an engine's versatility across platforms or of a conservative design philosophy that results in longevity and reliability. I don't think, however, that we ought to use it as a yardstick by which we measure other engines...

I think a major factor that contributed to VW designing the 5-cyl instead of a completely new 4-cyl was money. They already had the proven 2.0T, but they needed a new base engine for the mkV. Rather than start from scratch, they ended up using the 2.0 as a starting point for the design of the 2.5. In other words, take some blueprints, erase some lines, draw in a fifth cylinder, and voila. Modify a few bolt locations so you can use the casting from an existing head design, even better.

The other thing that keeps coming up is the terrible, harsh, rough, unrefined, off-balance nature of this engine. It's just not true, as many people who own this engine have said. True, there are second- and third-order vibrations which do not exist in I-4 designs, but there is a great deal of engineering between those mathematical calculations and actual driving feel. I especially like when C&D or Motortrend praise the wonderful new 2.5T in the TTRS, reveling in it's "growl"... after all, Audi has been making 5-cyl engines for years and they really know what they're doing. Oh, but that base Jetta engine, it's sure unrefined.

 

[Hokiefyd]

Originally Posted By: 07Wolfie
The Honda K24 (2.4L I-4) can certainly be held as an example of an engine's versatility across platforms or of a conservative design philosophy that results in longevity and reliability. I don't think, however, that we ought to use it as a yardstick by which we measure other engines...


I don't think so either. I only compare VW's 2.5L I-5 with other manufacturers' engines of similar displacement and power to point out that VW didn't necessarily realize a substantial increase in power or torque over other 2.4/2.5L displacements, so there must be a reason why the 5 cylinder architecture was used.

Originally Posted By: 07Wolfie
I think a major factor that contributed to VW designing the 5-cyl instead of a completely new 4-cyl was money. They already had the proven 2.0T, but they needed a new base engine for the mkV. Rather than start from scratch, they ended up using the 2.0 as a starting point for the design of the 2.5. In other words, take some blueprints, erase some lines, draw in a fifth cylinder, and voila. Modify a few bolt locations so you can use the casting from an existing head design, even better.


That's the best explanation I've heard, and makes a lot of sense to me. Thank you. I can't speak for others who posted in here, but all I personally was asking is why VW chose to use the 5 cylinder configuration rather than the more widely-used 4 cylinder configuration, especially given their success with 4 cylinder engines in the past. Using the 2.0L block as a starting point makes perfect sense.

I wasn't trying to say the I-5 is a bad choice and I wasn't trying to say that other engines are better. I'm afraid I was mis-interpreted, and if I wasn't clear, I apologize for that. My intent was not and is not to criticize VW's design choice, but to learn why it was used.

Edit: hey, my 4000th post!

 

[Spazdog]

Originally Posted By: 07Wolfie
...
I think a major factor that contributed to VW designing the 5-cyl instead of a completely new 4-cyl was money. They already had the proven 2.0T, but they needed a new base engine for the mkV. Rather than start from scratch, they ended up using the 2.0 as a starting point for the design of the 2.5. In other words, take some blueprints, erase some lines, draw in a fifth cylinder, and voila. Modify a few bolt locations so you can use the casting from an existing head design, even better.


But they already had a 5 cylinder. The VR5. The VR6 is still in use in various vehicles, to the best of my knowledge, it's still availiable in the Passat. And the VR5 would package better in an engine compartment than a L5 would...or should anyway.

Maybe the bean counters forgot about the VR5. Or maybe it was less expensive to modify the castings and make a new 5 cyl...

And as far as the imbalance, In my memory, the F22 with a cylinder grafted on (G25) was just better balanced. And that above 4000 rpm it just seemed to make more noise. That was just my opinion based on my experience. YMMV.

 

[JHZR2]

Originally Posted By: Hokiefyd


2) Honda has nothing to do with this. Not sure why you brought that up. You don't have to take a Honda to 5,000 rpm to make peak torque anyway. My 2.4L makes peak torque at 4,200 rpm and the VW I-5 makes it at 4,250


Because my wife came from a Honda (Acura) Integra. She drives gently and conservatively, and the driving style from this engine versus the integra is vastly different, though I'll bet power to weight and all performance aspects are roughly equivalent.

The integra 1.8 also drove different and operated different than, say, the 1.8L engine in my 318i. The integra 1.8 engine was a gem and ran beautifully at 186k when the car was overcome by rust and rubber part degradation. But it sure is a different type of powerband.

 

[JHZR2]

Originally Posted By: Klutch9


Ford/Mazda, Nissan, and Toyota all have a 2.5L I-4's. But I do agree with the fact that you do see quite a few more 2.4 I-4's than 2.5's, for whatever reason.


Recently we have been seeing some 2.5 engines, because to Joe consumer, bigger numbers are better. Historically though, we've seen LOTS of 2.4 L engines from most all of the majors.

 

[Quattro Pete]

Originally Posted By: rg200amp

VW's 2.5L I5 has a lot of untapped potential. I think VW will just up the HP and Tq through the computer by 10-20 each 4-5 years with each model face lift/generation.

At the same time, they'll have to up the performance of the 2.0T (which isn't hard to do either) in order to keep enough distance between the performance of the two engines to still justify the price difference.

 

[JHZR2]

Originally Posted By: Spazdog


But they already had a 5 cylinder. The VR5. The VR6 is still in use in various vehicles, to the best of my knowledge, it's still availiable in the Passat. And the VR5 would package better in an engine compartment than a L5 would...or should anyway.

Maybe the bean counters forgot about the VR5. Or maybe it was less expensive to modify the castings and make a new 5 cyl...

And as far as the imbalance, In my memory, the F22 with a cylinder grafted on (G25) was just better balanced. And that above 4000 rpm it just seemed to make more noise. That was just my opinion based on my experience. YMMV.


You have got to be kidding on a V engine! Unless the VR5 has some design aspect I'm not aware of, frankly, IMO, V engines in FWD vehicles are just plain stupid! Talk about a service headache for stuff like that rear bank of spark plugs.

No thanks!

 

[Quattro Pete]

Originally Posted By: 07Wolfie
I think a major factor that contributed to VW designing the 5-cyl instead of a completely new 4-cyl was money. They already had the proven 2.0T, but they needed a new base engine for the mkV. Rather than start from scratch, they ended up using the 2.0 as a starting point for the design of the 2.5. In other words, take some blueprints, erase some lines, draw in a fifth cylinder, and voila. Modify a few bolt locations so you can use the casting from an existing head design, even better.

So adding a 5th cylinder was easier to do than just increasing bore and stroke a little bit on the existing 4-cylinder? I'm no engineer, so I'm just asking.

Your theory of adding a 5th cylinder certainly holds water though since the bore and stroke are identical on the 2.0 and the 2.5.

 

[Spazdog]

Originally Posted By: JHZR2
Originally Posted By: Spazdog


But they already had a 5 cylinder. The VR5. The VR6 is still in use in various vehicles, to the best of my knowledge, it's still availiable in the Passat. And the VR5 would package better in an engine compartment than a L5 would...or should anyway.

Maybe the bean counters forgot about the VR5. Or maybe it was less expensive to modify the castings and make a new 5 cyl...

You have got to be kidding on a V engine! Unless the VR5 has some design aspect I'm not aware of, frankly, IMO, V engines in FWD vehicles are just plain stupid! Talk about a service headache for stuff like that rear bank of spark plugs.

The VR6 and VR5 only have one cylinder head. It's a 15° V engine. It was specifically designed to be fwd and fit in the space of a 4 cylinder
The plugs on a VR6 (that I have worked on)are kind of a pain but accessible between the intake runners. The 2-point-slow actually may be harder to do than the VR6 was.

 

[rg200amp]

Originally Posted By: Quattro Pete
Originally Posted By: 07Wolfie
I think a major factor that contributed to VW designing the 5-cyl instead of a completely new 4-cyl was money. They already had the proven 2.0T, but they needed a new base engine for the mkV. Rather than start from scratch, they ended up using the 2.0 as a starting point for the design of the 2.5. In other words, take some blueprints, erase some lines, draw in a fifth cylinder, and voila. Modify a few bolt locations so you can use the casting from an existing head design, even better.

So adding a 5th cylinder was easier to do than just increasing bore and stroke a little bit on the existing 4-cylinder? I'm no engineer, so I'm just asking.

Your theory of adding a 5th cylinder certainly holds water though since the bore and stroke are identical on the 2.0 and the 2.5.




Guys there not "adding" anything.

Instead of design a new base engine, they just took the Lambo's V10(they own that) design and used one bank.

It's WAY cheaper to use designs that have already been made than to design a totally new engine.

So, they did not "add a 5th cylinder".

They just deducted 5.

 

[Quattro Pete]

Originally Posted By: rg200amp

Instead of design a new base engine, they just took the Lambo's V10(they own that) design and used one bank.

It's WAY cheaper to use designs that have already been made than to design a totally new engine.

So, they did not "add a 5th cylinder".

They just deducted 5.

Going back to the C&D article that started this thread, it says:
Quote:
Unfortunately, the 2.5-liter is not the Gallardo's V-10 cut in half. Neither is it simply VW's familiar four-cylinder cast-iron block with an extra cylinder tacked onto the end. In fact, all three engines are part of the same extended family, as indicated by their shared 82.5mm bore and 92.8mm stroke.

Aren't they sort of contradicting themselves here?