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      07-27-2007, 10:57 AM   #23
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Originally Posted by NavNurs View Post
Actually, you did state it......."while the RS4 engine does feature DI/HPI it is not a refined process."
I realize that, I was using both terms as interchangeable.
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      07-27-2007, 11:16 AM   #24
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Details

South, others: Sure I care about the details of the system, it's applicability to a very high reving engine as well as longevity etc. All I am saying is that at the top level Audi is ahead of BMW and I really hoped for the wide spectrum of benefits (torque, mpg, etc.) of some form of DI for the M3.

Epacy: I saw the post about the oil consumption, didn't read it very carefully - did it mention DI as a known culprit?
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      07-27-2007, 11:29 AM   #25
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Epacy: I saw the post about the oil consumption, didn't read it very carefully - did it mention DI as a known culprit?
From the link.

Quote:
Originally Posted by RI_RS4
This engine has proven to be a bear on oils, because of chemical shear, due to high fuel dilution of the Direct Injection, combined with the mechanical shear of an 8250 rpm racing V8. Oil in this engine has been shown to have about a 3000 mile or less life expectancy.
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      07-27-2007, 12:32 PM   #26
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Quote:
Originally Posted by Epacy View Post
Isn't HPI just BMW's name for DI?

RS4 engine does feature DI.

You are technically correct that the RS4 doesn't have HPI as that is BMW's implementation. But that was never being stated.
No, RS4's DI is a socalled "first generation DI" whereas HPI is on of the first second generation DIs.

HPI is a spray-form DI (RS4's DI isn't spray-form) which has the advantage of extended lean-operation. Whereas FSI can save fuel (lean operation) only at low revs and quite low acceleration, the HPI stays in lean operation (=fuel saving) until about 4000rpm. As I said it's a totally new technology. Audi does not offer second generation DI to date.

So I am just as disappointed as Swamp that BMW didn't manage to feature HPI in M3's engine, but hopefully could clarify that it's nothing that Audi (RS4) "has" already.

Best regards, south
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      07-27-2007, 10:03 PM   #27
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Makes me wonder if red may be the color to get. For a while I was leaning to the white. Great review btw.
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      07-27-2007, 10:52 PM   #28
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Quote:
Originally Posted by southlight View Post
No, RS4's DI is a socalled "first generation DI" whereas HPI is on of the first second generation DIs.

HPI is a spray-form DI (RS4's DI isn't spray-form) which has the advantage of extended lean-operation. Whereas FSI can save fuel (lean operation) only at low revs and quite low acceleration, the HPI stays in lean operation (=fuel saving) until about 4000rpm. As I said it's a totally new technology. Audi does not offer second generation DI to date.

So I am just as disappointed as Swamp that BMW didn't manage to feature HPI in M3's engine, but hopefully could clarify that it's nothing that Audi (RS4) "has" already.

Best regards, south
Thanks for the clarification. Thought the terms were interchangeable.
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      07-27-2007, 11:17 PM   #29
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Originally Posted by The CSL View Post
Is Fuel Stratified Injection not a form of direct injection?

I don't know.
The RS4 FSI V8 uses direct injection with 1800 psi fuel rails. In Europe, with low sulfur fuels, the engine is enabled to use lean burn stratified mode. In the US stratified mode is disabled (until our sulfur levels in fuel are reduced), and DI is used.
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      07-27-2007, 11:30 PM   #30
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Quote:
Originally Posted by southlight View Post
No, RS4's DI is a socalled "first generation DI" whereas HPI is on of the first second generation DIs.

HPI is a spray-form DI (RS4's DI isn't spray-form) which has the advantage of extended lean-operation. Whereas FSI can save fuel (lean operation) only at low revs and quite low acceleration, the HPI stays in lean operation (=fuel saving) until about 4000rpm. As I said it's a totally new technology. Audi does not offer second generation DI to date.

So I am just as disappointed as Swamp that BMW didn't manage to feature HPI in M3's engine, but hopefully could clarify that it's nothing that Audi (RS4) "has" already.

Best regards, south
South, actually you are wrong about Audi's DI technology. FSI technology in the RS4 engine is a second generation technology known as tumble/swirl flow guided DI. It uses high pressure spray that is guided by the intake and combustion chamber flow pattern. The main difference between Audi DI and BMW DI is the use of piezoelectric actuated injectors in the BMW system, instead of electromagnetic injectors. Neither of the technologies, however, can be used in lean burn mode in the US, because of the high sulfur content in our fuels. Both technologies provide a fuel economy and power advantage, even in the US. If there is an advantage to HPI, (and there may be due to the way a piezo transducer might be used to shape the fuel charge) it is in the lean burn mode that is not enabled in the US, and only available in the European market.
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      07-27-2007, 11:34 PM   #31
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Originally Posted by Epacy View Post
Thanks for the clarification. Thought the terms were interchangeable.
Essentially they are interchangeable. Both are direct injection systems. In the US, both have similar performance. FSI and HPI are trademarked names for Audi and BMW direct injection systems, respectively.
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      07-27-2007, 11:41 PM   #32
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Quote:
Originally Posted by Epacy View Post
From the link.
Epacy, ah, I see you like to quote things that you don't understand, do you? Since you are quoting myself directly, you might want to ask me to clarify my quote. If you don't ask me to clarify, then I'll just assume that you want to distort what I've said.
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      07-28-2007, 12:39 AM   #33
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Would not running leaner in the US also increase NOx? I think the emission specs are a bit looser in Europe, especially NOx (which is why they can have more diesels).

-Dave
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      07-28-2007, 01:29 AM   #34
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Originally Posted by bower View Post
Would not running leaner in the US also increase NOx? I think the emission specs are a bit looser in Europe, especially NOx (which is why they can have more diesels).

-Dave
Yes. For lean burn, a NOx accumulating catalytic converter is used that stores nitrous oxide to be burned off later in the regeneration cycle, when the engine returns back to normal operation mode, where it burns off the accumulated NOx.
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      07-28-2007, 01:30 AM   #35
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Quote:
Originally Posted by RI_RS4 View Post
Epacy, ah, I see you like to quote things that you don't understand, do you? Since you are quoting myself directly, you might want to ask me to clarify my quote. If you don't ask me to clarify, then I'll just assume that you want to distort what I've said.
If you felt your post that I linked to required clarification, why didn't you do that in the first place? You posted it and others have linked to it. If your post was insufficient in the first place then that is up to you to correct. You can't go back and get on the others for not asking you for clarification. I hope you are actually joking about this.
Please elaborate on how I distorted what you said? I linked to the post you made about the very topic. Doesn't sound too distorted to me.
Please tell me all this is a joke because the claims you are making are absurd.

Also, why is it that alomst every Audi owner, that takes time out of their day to register on this board, resorts to personal attack? A little insecure?
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      07-28-2007, 02:21 AM   #36
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Quote:
Originally Posted by RI_RS4 View Post
South, actually you are wrong about Audi's DI technology. FSI technology in the RS4 engine is a second generation technology known as tumble/swirl flow guided DI. It uses high pressure spray that is guided by the intake and combustion chamber flow pattern. The main difference between Audi DI and BMW DI is the use of piezoelectric actuated injectors in the BMW system, instead of electromagnetic injectors. Neither of the technologies, however, can be used in lean burn mode in the US, because of the high sulfur content in our fuels. Both technologies provide a fuel economy and power advantage, even in the US. If there is an advantage to HPI, (and there may be due to the way a piezo transducer might be used to shape the fuel charge) it is in the lean burn mode that is not enabled in the US, and only available in the European market.
Thank you for the description of FSI. But that actually confirms what I said:
RS4's DI is indeed a first generation DI, whose characteristics are the injection pressure of 1800psi (about 120bar), being guided by the chamber flow pattern aswell as a "swirl flow."
Second generation DI (HPI, Mercedes CGI) however uses a higher injection pressure of 2900psi (200bar) and is only guided by spray form. That is what you also confirm with "the piezo transducer might be used to shape the fuel charge". I don't know if there are benefits on US market with their lower quality fuels, but nonetheless that a different generations of DI.

Quote:
Originally Posted by RI_RS4 View Post
Essentially they are interchangeable. Both are direct injection systems. In the US, both have similar performance. FSI and HPI are trademarked names for Audi and BMW direct injection systems, respectively.
No, they are not interchangeable. Only terms being interchangeable are HPI and (Mercedes) CGI. See above...


Best regards, south
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      07-28-2007, 03:46 PM   #37
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South.

Okay, I'll give you that. There are multiple forms of 1st, 2nd and 3rd generation Direct Injection, and can be classified as Spray Guided (as you said) and Wall Guided. First generation spray guided systems sucked and never got to market. First generation wall guided systems also sucked, since the fuel was litterally sprayed on the wall. Later generation DI either uses the spray nozzle to direct the flow into the spark plug, placing the injector between the valves and the spark plug (which requires much higher pressure to make sure that intake flow does not disrupt the spray), or the flow pattern in the combustion chamber, combined with the location of the spray nozzle. The spray guided method has a long term issue with intake valve deposits, since detergents from the spray cannot be deposited on the valves efficiently. The wall guided method with tumble swirl flow pattern can be designed to allow some fuel to swirl back onto the intake valves for cleaning. It will be quite interesting to see how both systems fare at 100K miles, since the biggest unresolved issue with all DI systems is intake valve deposits and oil fuel dilution.

All are forms of direct injection. Differences in one over the other only occur in lean burn mode. In homogeneous operation there are no differences, and certainly none at WOT. Thus no advantage or disadvantage of either type of direct injection with respect to top end performance. However, it remains to be seen whether any advantages hold true in practical applications after 100K miles are on an engine. Since you are from Germany, you are fortunate enough to be able to use engines which run in lean mode. I'd be interested to hear how both types hold up. Here in the US, the advantages/disadvantages are nil.

Both BMW and Audi engage in disingenuous marketing in the US. Both tout their HPI and FSI systems for significant fuel economy increases, yet neither use the fuel conservation mode in North America.

Last edited by RI_RS4; 07-28-2007 at 04:05 PM.
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      07-28-2007, 04:05 PM   #38
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Quote:
Originally Posted by RI_RS4 View Post
South. All are forms of direct injection. Differences in one over the other only occur in lean burn mode. In homogeneous operation there are no differences, and certainly none at WOT. Thus no advantage or disadvantage of either type of direct injection with respect to top end performance. However, it remains to be seen whether any advantages hold true in practical applications after 100K miles are on an engine. Since you are from Germany, you are fortunate enough to be able to use engines which run in lean mode. I'd be interested to hear how both types hold up. Here in the US, the advantages/disadvantages are nil.

Both BMW and Audi engage in disingenuous marketing in the US. Both tout their HPI and FSI systems for significant fuel economy increases, yet neither use the fuel conservation mode in North America.
Sure are both forms of DI, but you said it's the same technology/generation and I'm pleased that you now seem to agree that it's not. I already mentioned that HPI is able to stay in lean burn mode over a wider rpm-range than FSI.
HPI had quite good results in recent tests, but nobody knows anything about its long-term durability to date...
If your right about the US, also DI generally has no advantage over conventional engines, right? (Do you hear me, Swamp?)

Best regards, south
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      07-28-2007, 04:25 PM   #39
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south

Actually DI does have a small advantage over manifold injection w.r.t fuel economy and performance.

Fuel economy in the US is slightly better with DI, because the fuel is better atomized and mixed in the combustion chamber. This leads to much more efficient burning and lower emissions. By using some advanced oil analysis, we've found that Audi engine has a very clean burn, which can be detected with a Nitration analysis.

Max power is increased in a DI engine due to CC cooling. That's what allows Audi's engine to have a 12.5:1 compression ratio. The fuel spray helps to keep CC temperatures down and the engine out of detonation.
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      07-28-2007, 04:44 PM   #40
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Quote:
Originally Posted by RI_RS4 View Post
south

Actually DI does have a small advantage over manifold injection w.r.t fuel economy and performance.

Fuel economy in the US is slightly better with DI, because the fuel is better atomized and mixed in the combustion chamber. This leads to much more efficient burning and lower emissions. By using some advanced oil analysis, we've found that Audi engine has a very clean burn, which can be detected with a Nitration analysis.

Max power is increased in a DI engine due to CC cooling. That's what allows Audi's engine to have a 12.5:1 compression ratio. The fuel spray helps to keep CC temperatures down and the engine out of detonation.
Interesting, but on the other side does the tumble swirl reduce some power again. Also read that there could be some issues with "wall wetting"...
No matter, it's a DI anyway...do you happen to know what "slightly better" means (in percent)?

Best regards, south
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      07-28-2007, 11:33 PM   #41
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South, theres around a 5-10% fuel economy increase with Audi's DI. I average about 2 mpg better fuel mileage with my RS4 than I did with my previous S4, which both have 4.2L V8 engines of similar design. The standard tune FSI version of the same engine makes 350 HP, while the manifold injection version makes 340 HP.

As for wall wetting, all DI engines, no matter the type, will have this potential, since at WOT the engine design is trying to maximize the air/fuel charge in the cylinder. Even spray optimized DI will need to use some sort of CC flow pattern to evenly mix the air and fuel, and under some scenarios, this can lead to wetting of either the walls or the top of the combustion chamber.

In the research I've done on fuel dilution issues with engines, it appears that most DI engines dilute, and that engines that use Alusil (or similar) cylinder walls and low tension rings also have a tendency to dilute. The BMW V8 in the X5 has fuel dilution issues, as does the new Mazda/Ford DI engine, and the Audi FSI engines. I've not seen any data on the GM Ecotec engines yet. Under some operating conditions, all engines can wet the cylinder walls, but I'm beginning to believe that modern engine designs, which use smooth silicon cylinder bores and low tension rings to reduce friction, allow more fuel to pass by the rings with current oils. Interestingly enough, the 335i does not seem to have any major fuel dilution issue, but it uses Iron cylinder liners, which may help to improve the ring seal and contain the oil film in the upper cylinder region.

I worked with an expert oil tribologist and a leading-edge formulator to come up with an oil that works well in the Audi RS4 engine, by providing a better ring seal under high rpm conditions, and better chemical containment of the fuel once it does get into the oil. I'll be interested to see what happens with the new M3 engine. Even though it is not DI, it does use low tension rings in hard silicon cylinder walls.

As an aside, I know quite a few M3 guys on this board think I'm a trouble making Audi troll. Well ... I might make trouble from time to time. But I actually do like and appreciate the M3. I really hate the black and white thinking that some enthusiasts have. This back and forth competition between Audi, BMW and MB is nothing but good for all of us. Had Audi not come out with the RS4, BMW would not have raised it's game, and vice versa. Competition, friendly banter and sharing of accurate information is good for all.
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      07-29-2007, 12:25 AM   #42
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MB's C class had a V8 before the RS4.
Please do not try to tell me that the reason BMW went with a V8 was because of Audi.....
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      07-29-2007, 04:08 AM   #43
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Quote:
Originally Posted by RI_RS4 View Post
South, theres around a 5-10% fuel economy increase with Audi's DI. I average about 2 mpg better fuel mileage with my RS4 than I did with my previous S4, which both have 4.2L V8 engines of similar design. The standard tune FSI version of the same engine makes 350 HP, while the manifold injection version makes 340 HP.
Wow, you must have a pretty sensitive right foot. Never heard before that anyone has a better fuel economy with his RS4 than with the S4. But the S4 is indeed very bad in fuel consumption.

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      07-29-2007, 07:36 PM   #44
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GM claims DI in the CTS V6 results in 15% power, and 8% torque increase @1750 psi.

http://www.motortrend.com/roadtests/...s/engines.html
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