swajames

But how do you define detuned? At around 100 bhp per litre, the M5 isn't pushing any boundaries in respect of specific output from a normally aspirated engine. The V10 is a great engine, but some others are getting more out of their powerplant. Porsche's 3.6 liter engine in the GT3 for example generates 415 bhp, has an 8200 rpm redline and yet remains utterly bulletproof. Apply what Porsche did to the M5 and you'd be looking at 575 normally aspirated horses. As is stands, the S85B50 has 500. The S85B50 seems to have as much untapped headroom as the LSA in its application in the CTS-V (if you compare it to its cousin, the LS9 in the ZR-1). So which one is "detuned"? BMW feels that what it gave the M5 was enough, so why do you have such difficulty with the determinations that GM deemed to be appropriate for the CTS-V? The recently released initial specs (and supporting video evidence) would appear to confirm that the CTS-V isn't struggling for performance.

BetterMakeWay

Agree and disagree at the same time. You can't simply compare each output/liter for every NA engine. It's not that simple. Smaller engines are known to develop high specific output per liter. The same goes for the Porsche GT3 engine (115,2hp/l) and the same goes for the BMW E46 M3 CSL which provides 112.5 hp/liter compared to the 101.4 hp/liter of the M5 V10.

In the same side note the E92 M3 V8 delivers 103,05 bhp/liter.

Also Honda S2000 still hold the record (if i'm not mistaken) of 118.5 bhp/liter.

So you see there is a connection here and a trend, which is by far not a coincidence. The bigger the engine is the harder it is to obtain top performance/liter as to the bigger displacement and more complex internal mechanics. You ca't simply apply what Porsche did and claim BMW could or should develop 575 bhp from the M5 because on that side note it should develop 592 bhp if BMW were to "apply" what Honda did.

Another example is exactly the inhouse production of the Carrera GT which performs at 105.5 bhp per liter which is considerable less than their own recipe for the GT3. Mind though the Carrera GT's engine was first developed for racing purposes.

So to conclude i don't think at all BMW "detuned" in any way the V10 M engine. That was simply their result being happy with the output and performance but also the reliability.

LE: When producers claim or leak out that that engine is detuned to suit better that model/car that's probably the truth. I'm sure that is the truth with the AMG 63 models from Mercedes.

swajames

BetterMakeWay, that's dead on and it was the point I was making all along. These engines are bang on the the money as they are. BMW is right to be happy with the output and performance of the V10, but so is GM with the LSA. Could both of these engines output more if the engineers pushed them a little harder? Sure, but as they stand they are great engines and they get the job for which they were intended done.

StealthM8

The CTS-V engine is not a simple "detuned" version going in the ZR-1. The LSA supercharger is smaller and the engine has lower cost guts inside (no titanium), etc.

The "detuned" V engine wasn't to save room for more LS9 like power in the future, it was done for cost reduction. Because quite frankly, who would pay $100k M5 money for a Cadillac with the ZR-1's LS9 engine? But at $60k, the more cost effective LSA engine still provides enough power for the white and blue punch in the face of performance luxury.

LSA vs. LS9

But what the heck do I know, I'm a BMW owner today and a former M5 killing supercharged, modded to the max (for way less than BMW mod money!), LS6 CTS-V owner.



P.S. There's no replacement for displacement coupled with forced induction. Torque always wins.

swajames

+1

Bimmer32

It's nice to hear that after 4 years, GM finally got something to compared to the BMW v10. Too bad, it's still NOT NA. BMW just have the pull the "turbocharged" card, and history repetites itself for GM.

There IS a replacment for displacment. It's called, "high reving engines." Who is better at it than the v10 5.7liter NA outputting 605 hp @ 8K rpm? PORSCHE. High reving always has a step ahead of big blocks. Just study your history.

JetBlack5OC

Actually no, they already had it.

GM LS7 7.0 liter V8 - 505 hp - Peak output 505 hp at 6300 rpm and 470 tq at 4800 rpm.

BMW 5.0 liter V10 - 500 hp - Peak output 500 hp at 7750 rpm and 383 tq at 6100 rpm.

Both normally aspirated.

So since you think you are the engine guru on here. Why is using two extra cylinders and less displacement to get the same horsepower, better than using a bigger displacement V8.

Bimmer32

Let me clarify my statement above so worms don't break out from the cans. Strictly speaking, BMW's high rev high tech v10 is one step ahead of the LSA. In this sense, the high reving (proven in the past to have higher technology and cost more than "big blocks") is a replacement for displacement. BUT, as an engine baseline, there's is no replacement for displacement. To clarify, a bigger v10 will produce more hp than a smaller v10 of the small engine and technology. High reving engines tend to be more efficient with hp/liter (but not always necessarily fuel efficiency).

Here's a link I found on autoblog that said something about a v10 that inspired the LS9.

http://www.autoblog.com/2008/01/10/corvett...ed-by-bmw-m-v1/

JetBlack50C, the actual hp for the BMW v10 is 507, not 500. Please read this source:

http://www.mwerks.com/artman/publish/featu...inter_594.shtml

It may answer your question.

If I may, reiterate my stands: The LSA engine is nothing impressive compared to the BMW v10 based on that if the v10 were subject to the same force induction, it's high reving and more advance use of technology is still superior than the LSA and maybe even the LS9. In this regards, the replacement for displacement is higher technology (high reving). On the other hand, as total package (bang for the buck), the 09 CTS-V may well be "impressive" just like my 5.0 Mustang that was voted as "Best Bang for the Buck" back in its hay day. Today, it's in the junk yard while the Supra TT, RX-7 TT, and 300Z TT, are still sought after.

JetBlack5OC

Actually you are incorrect. You're quoting 507 bhp, not hp. The M5 is measured 500 hp SAE in the US. So the LS7 would be rated higher in bhp.


You really didn't answer my question about the LS7.

GM LS7 7.0 liter V8 - 505 hp - Peak output 505 hp at 6300 rpm and 470 tq at 4800 rpm.

BMW 5.0 liter V10 - 500 hp - Peak output 500 hp at 7750 rpm and 383 tq at 6100 rpm.

Both normally aspirated.

Why is using two extra cylinders and less displacement to get the same horsepower, better than using a bigger displacement V8?


Also one small thing, you keep referring to them as "big blocks", when actually they are "small blocks."

AMG uses the same philosophy with their 6.2 liter V8 normally aspirated and pushing 518hp. I believe its one of best engines being produced right now. Both engine philosophies do have their drawbacks.

swajames

It still speaks to two different philosophies to get to same end result. One isn't necessarily better than the other. Take forced induction off the table. As an example, despite its smaller displacement the V10 powerplant is physically heavier (by about 70lbs) and produces less specific output per lb of engine weight than say the LS7. The LSA is based on the LS3 which is lighter still than the LS7. Even with additional hardware, the LSA engine should weigh less than the S85. BMW's approach enables the higher RPM needed to generate power out of a smaller displacement, but it comes at the cost of extra weight. GM's OHV approach may be "lower tech" but it gets just as much output out of less physical mass. Why in your mind is one clearly better than the other? Subjectively, one may prefer one engine's characteristics over the other (the S85 trades its high RPM ability against a relative lack of lower end torque, the LS7/LSA offer much more torque, but can't rev to the same highs as the S85) but objectively they both churn out the same end result. If the V10 resulted in a smaller, lighter engine I would think that you have a point, but it doesn't. It's simply a different means to the same end.