///M535i engine swap

[dom535inik]

I'm curious to hear some of your opinions about swapping the high compression engine in my M535 with an M30b35.
I purchased the car and was having serious difficulties getting the car to pass emissions. This was the original reason I was considering the swap, but I've since passed so that's not as much of an issue anymore.
My reasons for using the b35 were:
1. comparable horsepower (208 vs. 218)
2. emissions friendly
3. ability to run on lower (less expensive) octane fuel
4. increased fuel efficiency (?)
Also, unless I'm mistaken, the b35 should be easier to upgrade to increase horsepower than the high comp. b34.
However, quite a few people I've talked to have questioned my decision. They claimed not having the original engine would detract from the originality of the car and lessen the value. I'm not planning on showing the car nor do I remotely consider it an investment and I'm definitely not considering selling it any time in the near future.
I don't think the people who are telling me these things are very familiar with the M535i though. I think, like most people, they are confusing it with an M5. (I don't think anyone in their right mind would dare replace an S38 with an M30.) True the M535 is somewhat rare, but its engine was not what made it stand out most from a standard 535. In some cases the M535 had the exact same lump as a standard 535.
I have the b35 and the means to make the change, but I just wanted a few opinions of some folks who are "in the know."
Thank you for your time,
Dominik

[Duke]

I am confused. The picture in your avatar is a US spec car. Is this your M535i?

Swap the engine, very few people would even figure out that it's a different engine anyway. If you had an absolutely bone stock/never modified M535i. I would think about keeping the original engine. That would indeed be a rare car.

[Rich Euro M5]

I am confused. The picture in your avatar is a US spec car. Is this your M535i?

You know I wonder if this is a Pacific NW thing. My DD the '86 535i with the Zender kit was badged as an ///M (removed) car when I purchased it. My 535i originated in Hawaii but then went to the Portland area. The second owner even referred to the car as an M535i when it's nothing more than a US car with a Zender kit. I guess where I'm leading with this. If the Avatar pic is what is being referred to as an M535i, it would seem that this is a PNW thing to mis-identify certain BMW models.

Rich

[dom535inik]

I have 2 e28s. The avatar picture is my '88 535i.

[Rich Euro M5]

I have 2 e28s. The avatar picture is my '88 535i.

Thanks for clarifying this.

Here's the links to the original thread and pics of my DD '86 535i.

Faux M535i Thread

Link to Faux M535i PIcs

Rich

[DRP535]

Don't touch it. You would be batshit insane to swap out a perfectly good B34 10:1 with a B35 just so you can put standard fuel in it. The work involved to do so is worth a hundred times more than the few cents you're gonna save on the cheaper fuel. And then there's the whole non-original thing I could go into as well.

Do yourself a favour and put the B35 in the US-spec 535i instead.

[miamirex]

Do not dare remove that moror, there are other tricks to passing emmisions testing, thr cost of fuel is of minor concirm, get a honda for everyday driving if fuel costs are a isssue.

[Rich Euro M5]

The emissions issue isn't a result of the higher compression. The most probable cause for emissions is the lack of an O2 sensor and the Lambda feedback circuit in the Motronic ECU used in non-green Euro cars. The easiest solution is installation of a US/NA 059 ECU and tuning with a custom chip, or installing a piggyback with Lambda capabilities and tuning for emissions. Once you dial in the A/F ratio and timing, passing emissions is generally not an issue.

Rich

[M635CSi]

I agree with Rich, higher compression increases thermal efficiency and reduces emissions. Get the engine tuned to pass the emission test. It isn't the compression ratio that is the problem but the B35 head would reduce emissions.

As far as the whole "originality" thing, it's kind of sad. One of the things I liked about BMW owners was they used to seem less interested in BS originality and more interested in the cars themselves - I hope that doesn't change. These cars are old, they will never be original again so make the car what you want and enjoy it and thank god the car isn't original!

[alpinewhite]

As far as the whole "originality" thing, it's kind of sad. One of the things I liked about BMW owners was they used to seem less interested in BS originality and more interested in the cars themselves - I hope that doesn't change. These cars are old, they will never be original again so make the car what you want and enjoy it and thank god the car isn't original!

well said....

[DRP535]

I agree with Rich, higher compression increases thermal efficiency and reduces emissions.

Higher compression increases oxides of Nitrogen in the exhaust which is one of the things they measure in determining the "dirtiness" of an engine. That's one of the reasons BMW installed those scolloped pistons to get the 8:1 cr in the M30. Bizarre but true. They actually had to reduce the efficiency of their engines and make them burn the fuel less completely in order to supposedly clean up their exhaust. Crazy for sure but that's the kind of really smart thing our governments legislate for on our behalf to make the world a better place.

That said though, I agree that with the experience in the US on these issues it can't be that hard to dodgy up something temporarily just to get a "dirty" motor to pass the US exhaust inspection, and that would be far perferable to swapping the entire engine.

[canyoncarver]

mine has,........it took some tweaking, but it passed californias stringent requirements.
having driven a "dirty" motor, youd definitely notice the difference if going to the B35. regardless of the advanced motronic management........it just does not have the snap the hi-comp motor does.
stick with a good thing..!!

[cgraff]

I agree with Rich, higher compression increases thermal efficiency and reduces emissions.

Higher compression increases oxides of Nitrogen in the exhaust which is one of the things they measure in determining the "dirtiness" of an engine. That's one of the reasons BMW installed those scolloped pistons to get the 8:1 cr in the M30. Bizarre but true. They actually had to reduce the efficiency of their engines and make them burn the fuel less completely in order to supposedly clean up their exhaust. Crazy for sure but that's the kind of really smart thing our governments legislate for on our behalf to make the world a better place.

That's interesting.....can you explain where you heard about the higher compression and increased NOx? As well as the resultant emissions effects you talk about? I'd be interested to hear about this. Thanks

-Chris

[M635CSi]

I agree with Rich, higher compression increases thermal efficiency and reduces emissions.

Higher compression increases oxides of Nitrogen in the exhaust which is one of the things they measure in determining the "dirtiness" of an engine. That's one of the reasons BMW installed those scolloped pistons to get the 8:1 cr in the M30. Bizarre but true. They actually had to reduce the efficiency of their engines and make them burn the fuel less completely in order to supposedly clean up their exhaust. Crazy for sure but that's the kind of really smart thing our governments legislate for on our behalf to make the world a better place.

That said though, I agree that with the experience in the US on these issues it can't be that hard to dodgy up something temporarily just to get a "dirty" motor to pass the US exhaust inspection, and that would be far perferable to swapping the entire engine.

DRP535, thank you for the correction, I should have said higher compression ratios increase thermal efficiency and reduce fuel consumption (not emissions). One aspect fuel efficient engines is they tend to have higher combustion chamber temperatures. It is when combustion chamber temperatures get above 1,300 deg C. that Nitrogen in the intake charge react with oxygen to form oxides (nitrogen dioxide and nitrogen monoxide).

[DRP535]

I'm no chemical engineer, but I dare say on overall balance of every noxious fume that comes out of a tailpipe, the sum total of the ones that come out of a high compression/high efficient engine is considerably less "bad" than the sum total of the ones that come out of a low compression/low efficiency engine. But that's neither here nor there. Everybody probably suspects or realises this already, but for the sake of taxation and government legislation, they have to put numbers against certain compounds as limits. So if NOx has to be xyz ppm then they'll make it so even if that means radical increases in unburnt fuel and CO2 and particulates exiting the pipe instead. But those things don't matter because they aren't measured.

It's all crap and stupid anyway. Designing a machine to government legislation instead of to ideal engineering efficiency principals is simply not right.

[cgraff]

DRP535, thank you for the correction, I should have said higher compression ratios increase thermal efficiency and reduce fuel consumption (not emissions). One aspect fuel efficient engines is they tend to have higher combustion chamber temperatures. It is when combustion chamber temperatures get above 1,300 deg C. that Nitrogen in the intake charge react with oxygen to form oxides (nitrogen dioxide and nitrogen monoxide).

But don't temperatures get above 1300 deg C, significantly above that, in the combustion chamber during flame initiation and propagation? So isn't formation of NOx a given during any sort of combustion then? And given that, aren't there other more significant and fundamental effects on the formation of NOx than just higher compression ratios that one should be investigating then so that one can put this into perspective and have a better understanding of exactly the principles behind pollutant formation?

-Chris

[cgraff]

I'm no chemical engineer, but I dare say on overall balance of every noxious fume that comes out of a tailpipe, the sum total of the ones that come out of a high compression/high efficient engine is considerably less "bad" than the sum total of the ones that come out of a low compression/low efficiency engine. But that's neither here nor there. Everybody probably suspects or realises this already, but for the sake of taxation and government legislation, they have to put numbers against certain compounds as limits. So if NOx has to be xyz ppm then they'll make it so even if that means radical increases in unburnt fuel and CO2 and particulates exiting the pipe instead. But those things don't matter because they aren't measured.

It's all crap and stupid anyway. Designing a machine to government legislation instead of to ideal engineering efficiency principals is simply not right.

I wouldn't disagree with that statement. A 'system's view' or understanding of looking at all the pollutants that come out, not just xyz ppm NOx or whatnot, is a far better methodology. One of the strengths of the EU emission regs vs the CARB or US ones is that they take into account the inherent differences in diesel vs gas engines, for example, so that the strengths' of each system are enhanced and the downsides reasonably limited on a system-wide perspective. This is just one of the big issues involved with bringing diesels to the US - that of passing 50-state emissions regs vs the equivalent gas engine's ability to do so.

However, what BMW does today or done in the past, granted what any manufacturer does is a trade-off in current tech available, marketing, and product development.

I really used to wonder why BMW did the 10:1 and 8:1 B34 engine split vs the older M90 9.3:1 engine. But then I figure that the common parts to the later 745, perhaps Motronic limitations using the O2 sensor feedback, cat longevity, emission regs, all these issues more than likely played a part in their decision to go one way or another.

-Chris

[Rich Euro M5]

I'm no chemical engineer, but I dare say on overall balance of every noxious fume that comes out of a tailpipe, the sum total of the ones that come out of a high compression/high efficient engine is considerably less "bad" than the sum total of the ones that come out of a low compression/low efficiency engine. But that's neither here nor there. Everybody probably suspects or realises this already, but for the sake of taxation and government legislation, they have to put numbers against certain compounds as limits. So if NOx has to be xyz ppm then they'll make it so even if that means radical increases in unburnt fuel and CO2 and particulates exiting the pipe instead. But those things don't matter because they aren't measured.

It's all crap and stupid anyway. Designing a machine to government legislation instead of to ideal engineering efficiency principals is simply not right.

In actuality BMW as well as the other auto manufacturers of the time didn't understand or know how to deal with emissions as they do today. Back in the bad ol days of low comression smogger engines like the M30s used in the US.NA cars there wasn't an NOX value to meet simply because they didn't have a way of measuring for NOX. Now we are expected to pass NOX levels that the cars were never designed to meet. Also you can't lump all emission tests in the US together. Some areas have emissions testing that is much less stringent than other areas. An E28 that passes in one geographical area with emissions testing might fail in another locality with testing because the standards are different from county to county and state to state.

My experience with the very strict ASM-II treadmill test used in certain Texas counties is:

1) You can have very low CO and HC values and fail NOX if the catalytic convertor and O2 sensor aren't functioning correctly.

2) If the cat isn't functioning correctly, increasing HC and CO to bring NOX into speciifcation will cause you to fail CO, while HC will be marginal but passing.

Rich

[M635CSi]

DRP535, thank you for the correction, I should have said higher compression ratios increase thermal efficiency and reduce fuel consumption (not emissions). One aspect fuel efficient engines is they tend to have higher combustion chamber temperatures. It is when combustion chamber temperatures get above 1,300 deg C. that Nitrogen in the intake charge react with oxygen to form oxides (nitrogen dioxide and nitrogen monoxide).

But don't temperatures get above 1300 deg C, significantly above that, in the combustion chamber during flame initiation and propagation? So isn't formation of NOx a given during any sort of combustion then? And given that, aren't there other more significant and fundamental effects on the formation of NOx than just higher compression ratios that one should be investigating then so that one can put this into perspective and have a better understanding of exactly the principles behind pollutant formation?

-Chris

Hi Chris, temperatures may get above 1,300 deg C. in some areas of the combustion chamber but as thermal efficiency goes up, so too does the heat and temperature of combustion so it's a question of degree (no pun intended). The the reason EGR systems work is they pump polluted air back into the combustion chamber thereby lowering combustion temperatures. If I wanted to lower the NOx in a high compression engine, I would install a water injection system to lower combustion chamber temperatures and keep the oxygen from combining with the nitrogen.

[cgraff]

DRP535, thank you for the correction, I should have said higher compression ratios increase thermal efficiency and reduce fuel consumption (not emissions). One aspect fuel efficient engines is they tend to have higher combustion chamber temperatures. It is when combustion chamber temperatures get above 1,300 deg C. that Nitrogen in the intake charge react with oxygen to form oxides (nitrogen dioxide and nitrogen monoxide).

But don't temperatures get above 1300 deg C, significantly above that, in the combustion chamber during flame initiation and propagation? So isn't formation of NOx a given during any sort of combustion then? And given that, aren't there other more significant and fundamental effects on the formation of NOx than just higher compression ratios that one should be investigating then so that one can put this into perspective and have a better understanding of exactly the principles behind pollutant formation?

-Chris

Hi Chris, temperatures may get above 1,300 deg C. in some areas of the combustion chamber but as thermal efficiency goes up, so too does the heat and temperature of combustion so it's a question of degree (no pun intended). The the reason EGR systems work is they pump polluted air back into the combustion chamber thereby lowering combustion temperatures. If I wanted to lower the NOx in a high compression engine, I would install a water injection system to lower combustion chamber temperatures and keep the oxygen from combining with the nitrogen.

I was hoping for a more fundamental analysis.

The truth of the matter is that flame temperature in an SI combustion chamber routinely reach 2000 deg K +. With the temperatures reached already well into the NOx formation temperatures, doesn't matter if you compare 8:1 or 10:1, the difference is actually negligible (relative to other effects described below). More critical to flame propagation is the combustion chamber shape, spark plug location, and other aero effects (swirl, etc), which then give dynamic effects. For example, remember that the gases burned early in the combustion phase are further compressed to higher temperatures as the rest of the charge burns and cylinder pressure rises. This is a dynamic effect that is highly important that one doesn't see initially by comparing on peak combustion temperature to another.

Yes, higher burned gas temperatures and oxygen concentrations in the burned gas are fundamental to NOx formation, with higher values leading to faster NO formation. But remember....it's *burned* gas temperature and oxygen concentration in the *burned* gas; not the intake charge per say. Again, it's dynamic, and not simply the *peak* combustion temperature or a single temperature value. And lowering combustion chamber temperature (e.g. water injection) is like robbing Peter (reducing efficiency) to pay Paul (get lower NOx)....a better solution all around would be a better combustion chamber design, for example.

The dilution of the unburned mixture with EGR leads to lower burned gas temperature due to increased heat capacity of the mixture per unit mass fuel, not exactly cooling of the combustion temperature as you note. One must be specific in this respect. Also, there is a limit to the amount of EGR that one can use, until other factors limit its use.

There are a couple other factors that directly effect NOx formation (spark timing also being one factor) that I can outline if you want. But, the point I want to get at is that NOx formation is not as simple as one might think. It's not 'purely' an issue of 'combustion temperature' per say, but has other more fundamental effects that one must be exact in describing. I could go on, but I want to suggest being a bit more exact in nature when describing these phenomena for the benefit of others and their edification.

-Chris

[M635CSi]

DRP535, thank you for the correction, I should have said higher compression ratios increase thermal efficiency and reduce fuel consumption (not emissions). One aspect fuel efficient engines is they tend to have higher combustion chamber temperatures. It is when combustion chamber temperatures get above 1,300 deg C. that Nitrogen in the intake charge react with oxygen to form oxides (nitrogen dioxide and nitrogen monoxide).

But don't temperatures get above 1300 deg C, significantly above that, in the combustion chamber during flame initiation and propagation? So isn't formation of NOx a given during any sort of combustion then? And given that, aren't there other more significant and fundamental effects on the formation of NOx than just higher compression ratios that one should be investigating then so that one can put this into perspective and have a better understanding of exactly the principles behind pollutant formation?

-Chris

Hi Chris, temperatures may get above 1,300 deg C. in some areas of the combustion chamber but as thermal efficiency goes up, so too does the heat and temperature of combustion so it's a question of degree (no pun intended). The reason EGR systems work is they pump polluted air back into the combustion chamber thereby lowering combustion temperatures. If I wanted to lower the NOx in a high compression engine, I would install a water injection system to lower combustion chamber temperatures and keep the oxygen from combining with the nitrogen.

I was hoping for a more fundamental analysis.

You deserve a refund!

The truth of the matter is that flame temperature in an SI combustion chamber routinely reach 2000 deg K +. With the temperatures reached already well into the NOx formation temperatures, doesn't matter if you compare 8:1 or 10:1, the difference is actually negligible (relative to other effects described below).

Negligible or not, as the compression ratio on a given engine goes up, so too does NOx emissions. Argue all you like but this is a settled issued within the automotive community which research such things.

More critical to flame propagation is the combustion chamber shape, spark plug location, and other aero effects (swirl, etc), which then give dynamic effects.

That's one of the reasons manufactures have gone to more open combustion chamber shapes and four valve configurations.

For example, remember that the gases burned early in the combustion phase are further compressed to higher temperatures as the rest of the charge burns and cylinder pressure rises. This is a dynamic effect that is highly important that one doesn't see initially by comparing on peak combustion temperature to another.

What's your point?

Yes, higher burned gas temperatures and oxygen concentrations in the burned gas are fundamental to NOx formation, with higher values leading to faster NO formation. But remember....it's *burned* gas temperature and oxygen concentration in the *burned* gas; not the intake charge per say. Again, it's dynamic, and not simply the *peak* combustion temperature or a single temperature value. And lowering combustion chamber temperature (e.g. water injection) is like robbing Peter (reducing efficiency) to pay Paul (get lower NOx)....a better solution all around would be a better combustion chamber design, for example.

When you say "a better solution all around", you're obviously not talking "all around" the economics of getting an old E28 to pass an emissions test.

"Parallel theoretical and experimental studies of the influence of inlet manifold water injection on nitric oxide emission from spark-ignition engines have been performed. Theoretical analysis based on chemical equilibrium calculations indicates that the reduction of combustion temperature due to water injection at rates comparable to the engine fuel consumption rate is sufficient to yield significant reductions in nitric oxide emissions. Theoretical results further show that water injection may be accompanied by increased volumetric efficiency due to evaporative cooling of the inlet charge during induction." - SAE Technical Papers; Inlet Manifold Water Injection for Control of Nitrogen Oxide Emissions From Spark-Ignition Engines Document Number: 690018

The dilution of the unburned mixture with EGR leads to lower burned gas temperature due to increased heat capacity of the mixture per unit mass fuel, not exactly cooling of the combustion temperature as you note.

Scroll up, although you've misquoted me, the result is the same; lower temperatures...

One must be specific in this respect. Also, there is a limit to the amount of EGR that one can use, until other factors limit its use.

Yep.

There are a couple other factors that directly effect NOx formation (spark timing also being one factor) that I can outline if you want.

Thanks Chris but I wasn't the one that asked the question. Increasing spark advance increases NOx emissions and while retarding the spark tends to reduce NOx emissions it also increases exhaust gas temperature.

But, the point I want to get at is that NOx formation is not as simple as one might think.
It's not 'purely' an issue of 'combustion temperature' per say, but has other more fundamental effects that one must be exact in describing. I could go on, but I want to suggest being a bit more exact in nature when describing these phenomena for the benefit of others and their edification.

Had my intent been to write a textbook on the subject I would have directed it to a different audience. My desire was to not speak over the heads of those who may benefit from practical information. I wonder why you would ask a question that you thought you knew the answers to...
I learned as a child this is a complex subject - my dad was a senior engineer with Universal Oil Products (UOP) in the Air Correction division.

[cgraff]

The truth of the matter is that flame temperature in an SI combustion chamber routinely reach 2000 deg K +. With the temperatures reached already well into the NOx formation temperatures, doesn't matter if you compare 8:1 or 10:1, the difference is actually negligible (relative to other effects described below).

Negligible or not, as the compression ratio on a given engine goes up, so too does NOx emissions. Argue all you like but this is a settled issued within the automotive community which research such things.

I was not arguing with comp ratio increasing temps. I am arguing that there are other issues that are just as, if not of greater importance here, which were not completely and accurately illustrated and ought to be for a complete understanding. If it were purely and chiefly an issue of compression ratio, then we'd be running 6:1 motors to pass NOx emissions, which is a ridiculous conclusion. Of course, there are more issues involved then that ought to be explained a bit.

For example, remember that the gases burned early in the combustion phase are further compressed to higher temperatures as the rest of the charge burns and cylinder pressure rises. This is a dynamic effect that is highly important that one doesn't see initially by comparing on peak combustion temperature to another.

What's your point?
[/quote]

My point was to illustrate one needs to be more exact when describing this phenomena...see my points below.

Yes, higher burned gas temperatures and oxygen concentrations in the burned gas are fundamental to NOx formation, with higher values leading to faster NO formation. But remember....it's *burned* gas temperature and oxygen concentration in the *burned* gas; not the intake charge per say. Again, it's dynamic, and not simply the *peak* combustion temperature or a single temperature value. And lowering combustion chamber temperature (e.g. water injection) is like robbing Peter (reducing efficiency) to pay Paul (get lower NOx)....a better solution all around would be a better combustion chamber design, for example.

When you say "a better solution all around", you're obviously not talking "all around" the economics of getting an old E28 to pass an emissions test.

"Parallel theoretical and experimental studies of the influence of inlet manifold water injection on nitric oxide emission from spark-ignition engines have been performed. Theoretical analysis based on chemical equilibrium calculations indicates that the reduction of combustion temperature due to water injection at rates comparable to the engine fuel consumption rate is sufficient to yield significant reductions in nitric oxide emissions. Theoretical results further show that water injection may be accompanied by increased volumetric efficiency due to evaporative cooling of the inlet charge during induction." - SAE Technical Papers; Inlet Manifold Water Injection for Control of Nitrogen Oxide Emissions From Spark-Ignition Engines Document Number: 690018

Are you going to argue for the economics of installing inlet manifold water injection system on a M30 to merely pass emissions? Because that is what you could be inferring above. There are dozens more economical solutions to getting an E28 to pass emissions. And a better head design by simply installing a B35 motor is one such solution. Albeit, it may not be optimal, but it is an option.

Of course, I can spit out my SAE papers and text books as well. ...I don't need you to show me with those that water injection works. But what's interesting here is really only that "theoretical results...show that water injection *may* be accompanied by increased volumetric efficiency." Again *may* is the key word here. It's dependent on a lot of other factors in practicality.

But this is getting beside the point. My point is again, there are a wide variety of phenomena and solutions to problems. And one must explain these in a little bit more depth than just offering them out.

e.g. water injection is a solution, but has these effects. or...a better head design will give these effects.

The dilution of the unburned mixture with EGR leads to lower burned gas temperature due to increased heat capacity of the mixture per unit mass fuel, not exactly cooling of the combustion temperature as you note.

Scroll up, although you've misquoted me, the result is the same; lower temperatures...

Actually I didn't misquote you, you state:
"The the reason EGR systems work is they pump polluted air back into the combustion chamber thereby lowering combustion temperatures."

I merely pointed out the more exact issue. Combustion temperature is not the same as burned gas temperature, unless you define it as such, but in all my readings the two are differentiated for the purposes of being more accurate in describing the processes at hand.

But, the point I want to get at is that NOx formation is not as simple as one might think.
It's not 'purely' an issue of 'combustion temperature' per say, but has other more fundamental effects that one must be exact in describing. I could go on, but I want to suggest being a bit more exact in nature when describing these phenomena for the benefit of others and their edification.

Had my intent been to write a textbook on the subject I would have directed it to a different audience. My desire was to not speak over the heads of those who may benefit from practical information. I wonder why you would ask a question that you thought you knew the answers to...
I learned as a child this is a complex subject - my dad was a senior engineer with Universal Oil Products (UOP) in the Air Correction division.

This is not an issue where you subtly claim I'm wrong by saying I *thought* I knew the answer... I actually do know it (not to mention extensively studied it), as you can as well know it. But the fact that you had to reply to my previous message proves that you still didn't get my point. The issue here is that if one is going to go in depth about a subject like this, one ought to either state it correctly and accurately....and yes this may mean writing a text book on it to explain it; or simplify it appropriately, noting exceptions or simplifications where necessary; or not saying anything at all.

I'm not arguing with you, my perhaps too subtle questioning to you was to pull out a more extensive treatment of the subject and then hoping to connect it to practical issues (e.g. the pros/cons water injection, or EGR, or installing a B35 motor).

Now, if you want, I hope we can reconcile this and close this discussion out with a more extensive treatise on the matter of emissions and the practical issue involved? And perhaps some solutions to the problem of getting E28s to pass certain emissions?

-Chris

[DRP535]

The truth of the matter is that flame temperature in an SI combustion chamber routinely reach 2000 deg K +.

-Chris

I'm gonna be a Shawn here and point out there is no such thing as °K (degrees Kelvin). The terminology is wrong. When stating temperature in Kelvin, it is just that... "Kelvin" and nothing more. There is no degrees about it.

And while I'm here, I'll say that another very good reason for BMW going to the 8:1 cr motor was because they needed to build an engine that would be able to be sold in the most number of markets worldwide with the least modification at a time when the were looking to significantly expand their international market penetration. That means building an engine to the lowest common denominator and that means pandering to the worst available fuel supply in a market they wanted to supply to.

That meant catalytic converters were required for the US & Australia which in turn meant ULP had to be used. I don't know what it was like in the mid-80s in the US but in Australia ULP was very new. It was only introduced in 1986. The highest octane you could get in Australia at the time was 91 RON (87 pump), so if BMW were to sell cars in Australia they had to give them engines that would run reliably on 91 RON fuel. That's much lower than a simple timing change is going to be able to accomodate on an engine designed for 96 RON as the 10:1 cr is, so a change of piston shape was called for.

[Jimmie G]

Without changing the motor you could swap the head and intake for a b35 and use a little more cam with a piggyback for lambda control just keep the b34 head just for keepsake you can allways throw it bake on to keep it oem.

I am running a b35 with ported head and intake three angle vg and some tweaks and it runs strong no dyno numbers yet.

Jimmie

[cgraff]

Without changing the motor you could swap the head and intake for a b35 and use a little more cam with a piggyback for lambda control just keep the b34 head just for keepsake you can allways throw it bake on to keep it oem.

I am running a b35 with ported head and intake three angle vg and some tweaks and it runs strong no dyno numbers yet.

Jimmie

The problem with running a B35 head on a B34 bottom end is that you lose compression ratio. The combustion chamber volume of a B35 head is larger than a B34 head, and thus just swapping head will cause a loss in compression ratio.

[DRP535]

Shave the head at the same time to compensate?

[Jimmie G]

So 9.5 to1 is going to be low right well I would take that with larger intake valves and better intake ports with the cam and get more power. And yes I know it drops the cr. Just thought it was a idea maybe worth talkin about. And shave the head and bingo its just a matter of time and money!

Jimmie

[cgraff]

So 9.5 to1 is going to be low right well I would take that with larger intake valves and better intake ports with the cam and get more power. And yes I know it drops the cr. Just thought it was a idea maybe worth talkin about. And shave the head and bingo its just a matter of time and money!

Jimmie

Ah...you're referring to the high comp B34. Although you'll drop compression ratio approx to 9.0:1. RaceTEP cc'd my B35 head at ~72 cc (not 65 as previously quoted, I need to correct my website info), and I can cc my B34 head to confirm, but nonetheless, the data suggests that a B35 head on a B34 high comp motor will lower comp to 8.9:1 - 9.0:1 from 10:1. That's a big drop. Not to mention that the piston dome shapes are very different between the B34 high comp and B35 motors. The B35 piston dome is better matched to the head's combustion chamber profile.

The advantages of the bigger intake valve and better intake ports *may* make up for the drop in CR. But I've never seen any back-to-back dyno runs to confirm.

With regards to a cam, you will not be able to fully utilize a bigger cam with that compression ratio; there is a limit. Basically (simply) the cam and cam timing needs to be optimized to the compression ratio you are running on the motor.

The problem with shaving the head is that it'll only give you 0.1 or 0.2 on compression ratio if using BMW's specs for shaving the head; but you might run into cam timing issues since the distance between the cam and crank is now different. You may have to use an adjustable cam gear to resolve that issue.

[scottiesharpe]

Dominik -

Put a piggyback controller on your car and you will have no problems passing smog if you have a working Cat.

The other solution wouuld be to run a decent 02 sensor feed back "Johnson box". I just happen to be selling a very nice one made by Valentine on my perpetual garage sale at

http://www.scottiesharpe.com/sale

Use that box with a new 02 sensor and you'll pass smog without issues.

Good luck.