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      08-30-2009, 08:47 PM   #1
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Why Didn't E9x M3's Come w/ Direct Injection?

I apologize if this has already run it's course, but does anybody happen to know why BMW didn't use direct injection with the V8? It's had already been proven to improve power and fuel economy silultaneously prior to the release of the E9x M3s in 2007. Anybody w/ inside knowledge out there? Obviously, with the plans to run a twin-turbo V6 with the next M3s, it should be considered crucial technology, but even normally aspirated cars reap the same benefits.
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      08-30-2009, 10:01 PM   #2
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Just an idea, but maybe it would've cost too much to R&D direct injection since our V8 is derived from the M5/M6 V10?
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      08-30-2009, 10:30 PM   #3
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You're probably right...I hear R&D for direct injection on an existing platform is costly. It makes sense from a cost perspective to just put it in the bag for the next engine design.

Probably the deal is when they originally started designing the S65, direct injection was not widely talked about like it is today.
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      08-30-2009, 10:48 PM   #4
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Quote:
Originally Posted by M3V8Driver View Post
I apologize if this has already run it's course, but does anybody happen to know why BMW didn't use direct injection with the V8? It's had already been proven to improve power and fuel economy silultaneously prior to the release of the E9x M3s in 2007. Anybody w/ inside knowledge out there? Obviously, with the plans to run a twin-turbo V6 with the next M3s, it should be considered crucial technology, but even normally aspirated cars reap the same benefits.
The three primary reasons:

a) BMW did not have a naturally aspirated direct-injection system developed at the time the S65B40 was engineered. (NA + 8400 rpms = long R&D lead time) The 335i's forced-induction N54B30 3.0-liter inline-6 was designed from the ground up.

b) The 4.0-liter V8 S65B40 engine, is based off the S85B50 5.0-liter V10 engine. There are obstacles to making major design changes to a engine that was previously developed as non-DI. An all-new head casting and fuel system would have been required. The R&D costs could not be accurately projected. (unknown) The is no way BWM's upper management would have green lit such a project for a low production (volume) car like the M3.

c) The eight individual throttle bodies. (which would have complicated matters even more)

Since BMW did not not originally engineer DI technology for the M5 or M6, there was little to no chance this was ever going to happen for the M3. The engineering costs required to 'retrofit' a direct injection system for the M3 ultimately killed any chance of seeing DI on this car.
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      08-30-2009, 10:52 PM   #5
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There is definately a thread or two about this, I remeber reading about it here...
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      08-30-2009, 11:21 PM   #6
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I wouldn't have bought my M3 if it was DI, so I'm glad it wasn't. It's going to take time for that new technology to be perfected; it's a work in progress. And with the stratospheric pressures needed, I don't think it'll ever be as reliable over the years as MPI IMO. Only time will tell.
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      08-31-2009, 12:26 AM   #7
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I just wonder what kind of performance we would get from it. It seems it gives an engine 10% gain in power and mileage. That would put us around 450 HP!! With better mileage.

The flip side is, we won't have to worry about carbon build up on the valves like what's happening to all the other DI engines.
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      08-31-2009, 06:01 AM   #8
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I would not have bought the M3. I dealt with the HPFP (high pressure fuel pump) problems way too many times.
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      08-31-2009, 08:18 AM   #9
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Quote:
Originally Posted by aus View Post
I just wonder what kind of performance we would get from it. It seems it gives an engine 10% gain in power and mileage. That would put us around 450 HP!! With better mileage.
I thought that DI has little (if anything) to do with improved power but is rather about better fuel economy.
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      08-31-2009, 08:26 AM   #10
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Quote:
Originally Posted by aus View Post
The flip side is, we won't have to worry about carbon build up on the valves like what's happening to all the other DI engines.
Yes, that's a serious issue with some. I've read about the problem in Audis.
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      08-31-2009, 09:24 PM   #11
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Quote:
Originally Posted by elp_jc View Post
I wouldn't have bought my M3 if it was DI, so I'm glad it wasn't. It's going to take time for that new technology to be perfected; it's a work in progress. And with the stratospheric pressures needed, I don't think it'll ever be as reliable over the years as MPI IMO. Only time will tell.
Me too--I wouldn't have bought one if it were DI. While I didn't have any problems with my 335 in the short time I had it, I was always wondering when the HPFP would fail. (BMW even extended the warranty to 100K on that component because it fails so often.)

I take a peek at E90post every now and then and the HPFP failures are still ongoing and a major problem for those with the N54 engine. The issue hasn't been resolved for the reasons you noted. Some guys are on pump 4 or 5. It's a common and very frustrating issue for N54 folks.

I've read several threads where the OP was lucky to be alive when it totally crapped out on the highway or in other high-risk situations leaving the car dead in the water. That's pretty scary and dangerous.

Quote:
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The flip side is, we won't have to worry about carbon build up on the valves like what's happening to all the other DI engines.
Yep, another issue with the N54 and other DI engines leading to misfires amongst other nasty things. Several threads going on that one as well I've seen.

I'm very happy we don't have DI on the S65 engine. To me it's plus not a minus. I'm open to the technology if they work out the bugs, but that day hasn't arrived yet.
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      08-31-2009, 09:30 PM   #12
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Just be glad it isn't and leave the issue at that.
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      08-31-2009, 10:29 PM   #13
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I thought that DI has little (if anything) to do with improved power but is rather about better fuel economy.
It also makes more power since it results in a more efficient burn. The Porsche engines made a good amount more power with DI.

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Yes, that's a serious issue with some. I've read about the problem in Audis.
There have been a lot pic's on the E90 side here and some Porsche engines with a ton of gunk on the valves. I'm just wondering if the Mazda and VW engines have the same issues.
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      09-01-2009, 12:03 AM   #14
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Quote:
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It seems it gives an engine 10% gain in power and mileage.
It doesn't 'give' the engine any more power by itself. It allows the compression to be raised (less possibility of detonation due to the cooler charge) so the engine can make more power, but it's not easily done. In the S65's case, I doubt it could have been raised any more than the already sky high 12:1 ratio, so the only gains would have been maybe a few HP from more aggressive timing, and better emissions. Hardly worth the risks now IMO, but once perfected, it'll help manufacturers cope with ever tightening emissions without sacrificing power that much. We'll see. Take care.
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      09-01-2009, 12:16 AM   #15
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I agree 100%, JC. Great points .

Quote:
Originally Posted by elp_jc View Post
It doesn't 'give' the engine any more power by itself. It allows the compression to be raised (less possibility of detonation due to the cooler charge) so the engine can make more power, but it's not easily done. In the S65's case, I doubt it could have been raised any more than the already sky high 12:1 ratio, so the only gains would have been maybe a few HP from more aggressive timing, and better emissions. Hardly worth the risks now IMO, but once perfected, it'll help manufacturers cope with ever tightening emissions without sacrificing power that much. We'll see. Take care.
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      09-01-2009, 12:39 AM   #16
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Quote:
Originally Posted by elp_jc View Post
It doesn't 'give' the engine any more power by itself. It allows the compression to be raised (less possibility of detonation due to the cooler charge) so the engine can make more power, but it's not easily done. In the S65's case, I doubt it could have been raised any more than the already sky high 12:1 ratio, so the only gains would have been maybe a few HP from more aggressive timing, and better emissions. Hardly worth the risks now IMO, but once perfected, it'll help manufacturers cope with ever tightening emissions without sacrificing power that much. We'll see. Take care.
Audi RS4/R8 4.2L runs at 12.5:1 compression ratio - as do I think the Porsche DI engines, so yes you can run them higher. DI should result in more complete combustion, allow for leaner air fuel ratios and more ignition timing, so potentially there could be some power to be gained.

That said the new Porsche GT3 is Porsche's most powerful naturally aspirated engine in terms of horsepower per litre (115 HP/L) and doesn't run Direct Injection.
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      09-01-2009, 01:50 AM   #17
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Quote:
Originally Posted by elp_jc View Post
It doesn't 'give' the engine any more power by itself. It allows the compression to be raised (less possibility of detonation due to the cooler charge) so the engine can make more power, but it's not easily done.
This was the topic of a very lengthy and heated debate. Well in the end it was not much of a debate since there was a vast majority who believed the evidence showed quite clearly that DI, BY ITSELF, without the benefits gained from the almost always accompanying compression bump, still does provide power gains.
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      09-01-2009, 11:37 AM   #18
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Quote:
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so potentially there could be some power to be gained.
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still does provide power gains.
Yeah, 1HP is a gain, and am sure our S65 would gain at least that much, so you guys are right. I should have said a 'significant' gain . As Mixja said, the GT3 is not DI, so DI is not a requirement to extract power. But for emissions reasons alone, the technology is here to stay, and I'm all for it; I just didn't want to deal with engine reliability issues when the technology is clearly not ready for prime time, that's all. Good day gang.
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      09-01-2009, 08:12 PM   #19
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Quote:
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Yeah, 1HP is a gain, and am sure our S65 would gain at least that much, so you guys are right. I should have said a 'significant' gain . As Mixja said, the GT3 is not DI, so DI is not a requirement to extract power. But for emissions reasons alone, the technology is here to stay, and I'm all for it; I just didn't want to deal with engine reliability issues when the technology is clearly not ready for prime time, that's all. Good day gang.
Wrong again. DI alone without a compression increase can provide nearly 10% power gains. Numbers from various tests and sources vary but DI does quite a lot more than just allow more compression. The basic phenomena is that fuel (rougly 15% of a premixed charge) is missing from the intake charge when using DI. The fuel is then forced in to the combustion chamber, this providing more air and more fuel per detonation. This provides a volumetric efficiency gain and hence a power gain.

You can find the reference to an SAE paper that gives such a figure (and an unbelievably long debate on the topic) here.

http://www.m3post.com/forums/showpos...&postcount=187
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      09-01-2009, 10:56 PM   #20
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What swamp2 is referring to is increased volumetric efficiency. In DFI engines, only air is brought in through the intake valves and not an air/fuel charge. Thus a greater amount of oxygen (and accompanying gasses) can be "inhaled" every intake stroke on a DFI engine and thus a greater amount of fuel can be injected. More air + more fuel = more power. Simple. Volumetric efficiency gains for DFI engines are about 15%. Only about half of this shows up as a power gain (hp) due to the additional power necessary to run a HPFP.

FWIW, BMW did have a DFI NA engine prior to the N54. The V12 used in the prior generation 760i/il was BMW's first foray into direct injection. Said engine pre-dates the S65 by a long shot.

With all of that said, I really don't see how the S65 could have been a DFI engine. The placement of the throttle bodies seems to preclude DI (the injector is almost always located at TDC requiring that a throttle body be located upstream in an intake manifold). Also, FWIW, the gains from individual throttle bodies is similar to the gains from DI so it's kind of a wash.

Here's to hoping that the next M3 uses some sort of an innovative engine layout. A short stroke flat six with twin VGT turbos would be pretty cool (essentially the same engine that is in the 911 turbo). Flame suit on
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      09-01-2009, 11:27 PM   #21
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The basic phenomena is that fuel (roughly 15% of a premixed charge)
Check your math. Stoichiometric ratio is 14.7:1 (a good average to use), which means 1 of 15.7 mass units is fuel, or 6.4%. Even a super rich 12.5:1 ratio adds up to 7.4%, not 15%. But that's irrelevant.

Bottom line is you're not getting even close to 6.4% power increase with DI alone on a high performance engine. Main reason for DI is EMISSIONS, not power.
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      09-02-2009, 02:40 AM   #22
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Check your math. Stoichiometric ratio is 14.7:1 (a good average to use), which means 1 of 15.7 mass units is fuel, or 6.4%. Even a super rich 12.5:1 ratio adds up to 7.4%, not 15%. But that's irrelevant.

Bottom line is you're not getting even close to 6.4% power increase with DI alone on a high performance engine. Main reason for DI is EMISSIONS, not power.
Yes I meant 1 part in 15 not 15%, a small brain fart. The numbers speak for themselves in the engineering literature. Either way you still are and were flat out incorrect when you stated that DI alone can not add power. The ranges I have seen are between 3% to 10%. We can only really speculate on how much power you would get in the M3s engine from DI alone, but it absolutely would be way way more than 1 hp. A mere 3% gain would provide 12 hp (all else equal).

Now that being said I will freely admit that DI is a feature implemented more for improved emmissions rather than power gains. Its magic is that is can provide both.
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