TheSamba.com :: View topic - Any reason not to build a WBX bigger than 2.2?

Fri May 20, 2011 9:52 am

STOP RUNNING REGULAR :? It says on your Vanagon to only use 91OCT The same people on this forum that are going to run regular fuel in the WBX are going to be the same people who later say that the WBX is a piece of crap so they are going Subaru :x I suggest people need to stop thinking they know better and understand that the engineers in Germany design things to run on good quality fuel. 91 Oct is the lowest grade they make. In the US is it our high end fuel. :oops: To the person who is running regular in a new GoWesty 2.5 :shock: Stupid move. You just voided your warranty now that you have paraded your mistake on the forums :roll:

Fri May 20, 2011 9:54 am

Quote: Yes, the Porsche 944 S2 and the 968 have 3.0L inline 4 cylinder engines, or 750cc per cylinder. But they use balance shafts to counter the vibrations from such large cylinders, and they rob about 5 hp. These are very smooth and reliable engines. I wonder what kind of vibrations would exist in a boxer configuration.

My understanding is they use balance shafts because inline 4's need balance shafts, I don't think it has to do with the piston size. There are established harmonic patterns that arise in that configuration regardless of displacement, so you see most I4's have a balance shaft to counteract the inherent imbalance of that config. H-4's, straight 6's, and 3 or 4 other config's I can't think of at the moment are inherently balanced.

Fri May 20, 2011 11:57 am

Quote: It says on your Vanagon to only use 91OCT

Um, this is old hat, but you might look up the differences between the octane ratings systems used in Europe vs. USA (RON vs. (RON+MON)/2, aka CLC or AKI ratings). In a nutshell, 91RON used in Europe is about equal to a US 87 AKI, also known around here as "regular unleaded".

Quote: I suggest people need to stop thinking they know better and understand that the engineers in Germany design things to run on good quality fuel.

The exalted German engineers* designed things to run on the fuel that is available to public highway drivers, the quality of which doesn't vary substantively between the major markets. The wbx is not only not required to use high octane fuel, it is especially tolerant of low octane fuels, by design.

I know it feels good to believe we're driving the thoroughbred horse of vans, but the reality is a bit more parochial, it's just a delivery van.

*(many of whom were not German, multinationals like VW have been global polyglot institutions for decades now; Ford for instance has for years been as German a company as it is American, but they also employ many Italians, Japanese, Indians, Armenians, etc....um, you know, people? I promise you that portions of the design work on any VW car of the last 30 years or longer were carried out in VW's operations in many countries besides Germany, where there were few if any actual Germans to be found. Put another way, nations have nationalities; business shitcanned that notion a long long time ago because it's a severe impediment to making money)

Fri May 20, 2011 1:45 pm

tencentlife wrote: Quote: Yes, the Porsche 944 S2 and the 968 have 3.0L inline 4 cylinder engines, or 750cc per cylinder. But they use balance shafts to counter the vibrations from such large cylinders, and they rob about 5 hp. These are very smooth and reliable engines. I wonder what kind of vibrations would exist in a boxer configuration.

My understanding is they use balance shafts because inline 4's need balance shafts, I don't think it has to do with the piston size. There are established harmonic patterns that arise in that configuration regardless of displacement, so you see most I4's have a balance shaft to counteract the inherent imbalance of that config. H-4's, straight 6's, and 3 or 4 other config's I can't think of at the moment are inherently balanced.
Somewhere in the attic I have a "Porsche Buyer's Guide," that talks about the process that brought balance shafts to the 944 engines. According to the book, at around 2.4 liters, the harmonics present in all inline fours are significant enough to require counter-rotating balance shafts for high-RPM use. Porsche messed with it for a while, then licensed Mitsubishi's patented system for their engines. 90-degree V8s are also inherently balanced.

Fri May 20, 2011 2:05 pm

tencentlife wrote: Um, this is old hat, but you might look up the differences between the octane ratings systems used in Europe vs. USA (RON vs. (RON+MON)/2, aka CLC or AKI ratings). In a nutshell, 91RON used in Europe is about equal to a US 87 AKI, also known around here as "regular unleaded".

You beat me to it tencent. Different rating system.

I was always under the understanding that octane requirements were primarily a function of compression ratio.

Fri May 20, 2011 2:05 pm

Seems like Porsche should've just borrowed Audi's inline five blocks and then bored those out to achieve the desired effect. Way less complicated and those fivers are bulletproof. My DD is a 2.5L fiver and I absolutely love the smoothness and awesome sound.

Fri May 20, 2011 5:17 pm

Horizontally opposed fours, though still not perfectly balanced, are balanced well enough that they don't need balance shafts at 2.5 liters. To be refined, an inline four typically needs to be balance shafted when larger than 2.0 liters. There are limits to what a balance shaft can do. A Mitsubishi 2.6, or for that matter a Porsche 944 S2 with the 3.0 inline 4 are certainly not what I would call silky smooth.

FWIW, the only engine configurations that are truly 100 percent balanced are the inline 6, the H6, and the 60 degree V12. V8s with 90 degree crank throws come pretty close as do some V6s and H4s, but they are not perfect.

D

Sat May 21, 2011 12:02 am

I don't think displacement has much to do with an engine needing a balance shaft, it'ts the layout. Most inline fours need them even the 600cc total displacement motorcycle engines, in fact they probably need them much more than a 3000cc car engine, the bikes rev up to 15,000+ rpm.

Sat May 21, 2011 11:10 am

Vango Conversions wrote: I don't think displacement has much to do with an engine needing a balance shaft, it'ts the layout. Most inline fours need them even the 600cc total displacement motorcycle engines, in fact they probably need them much more than a 3000cc car engine, the bikes rev up to 15,000+ rpm.

If we're talking inline fours, 2.0 liters is the point that most modern automotive engines become fitted with balance shafts. It simply comes down to the magnification of the second order forces that are present in the inline four configuration. Above 2.0 liters the pistons get large and heavy, and/ or the stroke gets significantly longer. Both of these characteristics amplify the magnitude of internal vibration.

I wasn't aware that 600cc motorcycle inline fours had them, but I guess I'm not surprised given their extremely high redlines.

David

Tue Aug 30, 2011 5:23 pm

Bump.

I'm loving my 2.3 liter Rocky Jennings engine!
http://www.thesamba.com/vw/forum/viewtopic.php?t=470798

Steve

Tue Aug 30, 2011 9:04 pm

Jedi wrote: STOP RUNNING REGULAR :? It says on your Vanagon to only use 91OCT The same people on this forum that are going to run regular fuel in the WBX are going to be the same people who later say that the WBX is a piece of crap so they are going Subaru :x I suggest people need to stop thinking they know better and understand that the engineers in Germany design things to run on good quality fuel. 91 Oct is the lowest grade they make. In the US is it our high end fuel. :oops: To the person who is running regular in a new GoWesty 2.5 :shock: Stupid move. You just voided your warranty now that you have paraded your mistake on the forums :roll: On page 56 of my 1986 owners manual there is an explanation under the heading FUEL SUPPLY and Octane Rating: "The 91 RON octane rating which you will find on the inside of the fuel tank flap is based on the research method. The CLC octane rating usually displayed on U.S. gasoline pumps is calculated as follows: Research octane number plus motor octane number divided by 2. Regular fuels have an octane rating ranging from 91 to 95 RON (Research Octane Number) or 87 CLC (U.S. Cost of Living Council Octane rating)." Chris is right.