V8's vs I6's - Page 3 - PeachParts Mercedes-Benz Forum

LUVMBDiesels · #31 08-30-2010, 02:21 PM

One car I always wanted was the old Firebird Sprint with the OHC I6.
It was supposed to be much better balanced than her V8 powered sisters and almost as fast.

Hey, while we are on the subject, what about flat sixes?
I loved the flat six in my Corvair. It had plenty of torque and was pretty smooth. You could not rev it too hard though or the fan belt would fly off!

400Eric · #32 08-31-2010, 01:36 AM

Flat 6s are great! If Subaru would ever get serious and turbo theirs I'd be all over it!
Regards, Eric

400Eric · #33 08-31-2010, 01:42 AM

Quote:

Originally Posted by 400Eric

400E vs. C36
(4.2 M119 V8 W124 vs. 3.6 M104 I6 W202.)

This 3.6 M104 I6's advantages:
Was built, modified, and breathed upon by AMG
Housed in a smaller, lighter car
Owned, maintained and driven by a M.B. master tech
Much better gearing (2.82 vs. 2.24)
Riding on MUCH better tires (4.2 car was/is on tiny 205/60-15s!)
Is newer (about the same miles though)
Not T-boned to within an inch of it's life like the 400E was

This 4.2 M119 V8's advantages:
Um, err, ah, ......
OK! Here are two! It's about a half liter bigger and...
There are 32 ports and valves feeding it instead of only 24.

Here's what happened: http://www.youtube.com/watch?v=Sa5h4fq2Jkg
The 4.2 had the higher MPH but the 3.6 had the quicker E/T.
If the 400E had only ONE of those advantages that the C36 enjoys (the 2.82 gears), it would easily out E/T the C36 as well.

The OP's original post was also about handling. There's less engine sitting out in front of the front wheel centerline with the V8, leading to the advantage of better weight distribution.

I don't think M.B. ever made an all aluminum I6. Their all aluminum V-8s are common however.

I'd still love to be able to add a C36 to my fleet though.

Regards, Eric

Correction! the C36 has 2.87 rear gears not 2.82.
Regards, Eric

wbain5280 · #34 08-31-2010, 04:35 AM

[QUOTE=400Eric;This 4.2 M119 V8's advantages:

I don't think M.B. ever made an all aluminum I6. Their all aluminum V-8s are common however.

Eric[/QUOTE]

MB's M189 was all aluminum, save the cast iron liners, and was used in 50's and 60's 300's, such as 300SL's and 300SE/L's. It's a robust, though complex, engine.

samiam44 · #35 08-31-2010, 12:35 PM

Flat 6-s are nice as they don't have counter weighted crankshafts- so they are very light and rev happier.

400Eric · #36 09-01-2010, 01:54 AM

Yes, it's too bad only 2 car manufacturers are currently making them.
Regards, Eric

MAG58 · #37 09-01-2010, 11:10 PM

Like the I6, the H6 has become a victim of the packaging craze of mfg's. Either way you slice it there are drawbacks to packaging a flat six, most of them involving interaction between the heads and the tires on turning circle.

It's a pity. I6 and H6 are two of my favorite configurations.

400Eric · #38 09-02-2010, 02:10 AM

Maggie, it's September now. Where are those block photos and crankshaft weights? You said you'd post them after summer school ended August 13! You were also gonna check crank forging numbers to confirm that the 3.2 M104 crank is indeed the same as the OM603 3.0 crank. I don't mean to be so demanding, it's just that I'm just itching to see that post! I'm like you, I'm curious!
Regards, Eric

JamesDean · #39 09-02-2010, 03:05 AM

400Eric · #40 09-02-2010, 07:28 AM

Thanks!
Regards, Eric

MAG58 · #41 09-02-2010, 02:19 PM

Sorry, I've been super busy these last few weeks with med school apps, school, work, and right as it all looked to clear and I'd have some time to work on the merc (and by work on the merc I mean put a bigger motor in it

), my 240Z got t-boned on campus by some sorority slut so I'm haggling with their insurance to get my baby back.

Don't worry though, it's under the list of things I need to do soon.

Though if anyone has the rod length to the C36 motor that would be greatly appreciated....

400Eric · #42 09-03-2010, 12:58 AM

Med school? I thought you were gonna be an engineer? Although I have to agree med school is the way to go unless you want to be an engineer for a foreign car company.

Sorry to hear about the 240Z. When that insurance company starts quoting you "comps" ask to see them (you have the right). The comps they were quoting me when Benzer 3 got T-boned weren't comps at all. I proved to them that every comp they sent me was a car that wasn't of the caliber as mine (B-3 was a perfect car before he got hit). Also, if you can successfully claim that the Z was your only source of transportation, do it! That way you can make them provide you a rental car which will motivate them to settle with you quicker.

I'd like to know the C36 rod length too, although we do know it's gonna be either 145mm or 149mm! I thought I saw it somewhere before and I think it was 145mm. I guess there wasn't enough room for the 149mm rod which is too bad because with the 145mm ratio the ratio is pretty stinky. Even with the 149mm rod it's not that great.
Regards, Eric

MAG58 · #43 09-03-2010, 02:56 AM

I was thinking it was the 145mm rod too but if I calculated right, the CR on that is tiny. I checked EPC and while all other M104's either carry M104 or the M102 number (149 or 145), EPC listed the rod as an HWA part # (AMG Specific), though there are plenty of non HWA parts in the motor.

Just remember, BMW turns 8k on a 91mm stroke 139mm rod in a much more distended engine.... Hence my inquiry.

Shoomakan · #44 09-03-2010, 04:44 AM

Somebody on page 1 said I6's are more compact. That's the farthest thing from the truth, man. V8's are essentially as long as inline 4's, but they're alot wider. And width is not something usually lacking under any car's hood. The I6 is one of the longest engine configurations around, not to mention the heaviest.

I dropped an old 5.0 V8 from a Mustang into my old 240SX, and the front end of the car rose a few inches. That V8 was significantly lighter than the 2.4 litere KA24 that was in the car. V8's are light, too. New all aluminum units are even lighter.

V8's are also extremely revvy when they're breathing properly, more so than a inline 6. I think it's because they have double the displacement, but not double the weight. Less relative intertia, I guess.

So, since this page is about V8's vs V6's, here is what I think:

V8:

Lighter
Easier to package
Lots more power usually (unless they're the same displacement, which is rare) (ex: TVR 4.0/4.5 inline 6, I think those came on the Cerbera)

I6's:

Usually revvier, but again, depends on the V8 (E92 V8 comes to mind)
Heavier
Less vibration
More linear powerband

And I'd like to correct the assumption that V8's spend more fuel. Highway mileage, V8's are almost always more economical than I6's, usually due to way longer ratios.

V6's I find quite useless, to be honest. V8's are just a TAD bit bigger and have better characteristics.

Any other opinions? I'd really like to hear 'em.

MAG58 · #45 09-03-2010, 11:11 AM

Hmm....
V8's are still not light engines.

KA24DE = 368lbs (Source: Drifting.com)
Ford 5.0L Weight = just under 460lbs (source: gomog.com)

I'm not sure where you got that a 302 ford is anywhere near the weight of an I4.

V8's require a substantial amount of work to be a 'revvy' engine because by the nature of the design, they require heavy first and last counterweights. Unless it's a flat plane motor. Then they're very displacement limited and still vibrate. I've built both, and if they're both setup right, the I6 will still out turn a V8 unless it's a small displacement motor vs. a larger displacement under square I6. Again, perfect balance means a bunch of weight can be taken out of I6 bob weights. Unless you do like BMW and put heavy metals in the counterweights ($$$) you're dealing with big, ungangly counter weights lest you like vibrations.

And what are your statistics for highway mileage here? The LSx is the only engine that comes to mind that is close to the modern I6's in mileage relative to body weight. The Atlas I6 did very well against the 5.3 LSx despite having over a liter of displacement disadvantage. I'm not sure what ratio you're talking about here, but there are also surprisingly few V8's that have decent rod/stroke ratios and even fewer that have bore/stroke ratios near/above 1:1 any more. They keep trying to be more compact which means bore goes away in leiu of additional stroke, though unfortunately rod/stroke ratio suffers.

Yes, Iron I6's are heavy because they require a substantial amount of bracing within the engine to dampen NVH of a crank that long. But the aluminum I6's are not heavy at all. Have you weighed the current BMW N series Aluminum/Magnesium I6's? They compare VERY well to any OHC V8 save maybe the featherweight UZ engines.

Packaging is a relative issue. I can tell you right now that an I6 is much more friendly to work on in the long, narrow hood of my 240Z whilst a V8 accommodates much better to the short, wide engine bays of the current trends.

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