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E39 (1997 - 2003)
The BMW 5-Series (E39 chassis) was introduced in the United States as a 1997 model year car and lasted until the 2004 when the E60 chassis was released. The United States saw several variations including the 525i, 528i, 530i and 540i. -- View the E39 Wiki

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  #326  
Old 08-03-2011, 03:08 PM
98540iA 98540iA is offline
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unlock your OBC and you can see exactly what rpm you are running at idle, test #7 one click after the coolant temp display.
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  #327  
Old 08-03-2011, 03:42 PM
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unlock your OBC and you can see exactly what rpm you are running at idle, test #7 one click after the coolant temp display.
Oh, right, thanks! I'll try that.
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  #328  
Old 08-03-2011, 03:57 PM
franka franka is offline
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Centrifugal SCs need rpms to build pressure. They are not known for good low rpm output. Think of a fan with air leaking around it's perimeter.
That is why I've always promoted a twin screw type for street use. But they are more expensive. They have boost right from idle. Centrifugals are lowest cost type and therefore popular, but do produce good high rpm power.

My idle is around 5-600 and I like like that. I never liked a low idle. I think Dinan can raise for you if you want. It's not like a carb with an idle speed screw, as you know.
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  #329  
Old 08-03-2011, 05:09 PM
98540iA 98540iA is offline
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Originally Posted by franka View Post
My idle is around 5-600 and I like like that. I never liked a low idle. I think Dinan can raise for you if you want. It's not like a carb with an idle speed screw, as you know.
Yes, they can adjust your idle. I have Powerchip and they asked me if I wanted my idle raised but I didn't, mine idles consistently at 550 rpms and it feels just right.
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  #330  
Old 08-03-2011, 08:16 PM
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Alex, mine idles smoothly at 500 rpm. It took me a while to get used to it, because I was always used to 750-850 rpm, but it seems perfectly happy at that sped, and I see no reason to mess with it.
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  #331  
Old 08-03-2011, 09:12 PM
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Flug540 Flug540 is offline
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Alex, mine idles smoothly at 500 rpm. It took me a while to get used to it, because I was always used to 750-850 rpm, but it seems perfectly happy at that sped, and I see no reason to mess with.
Thanks! One thing I realized today is that RPM is higher with A/C on, and, of course not having it charged, I had it off. Charged it today (here is a very nice writeup btw) and RPM rose with A/C on to the level I remember it at, which is slightly higher then the middle line. I'll check what it actually is tomorrow.

Last edited by Flug540; 08-03-2011 at 09:15 PM.
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  #332  
Old 08-03-2011, 10:03 PM
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Idle raises by about 150 - 200 rpm iirc as soon as the A/C compressor is fired up. I suspect it may stall otherwise.
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  #333  
Old 08-04-2011, 03:19 AM
franka franka is offline
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Driving tricks for very high temp locations. FYI

With a manual tranny and the heat in Dallas, as well as other West and Southwest locations like Phoenix, El Paso, etc I would like to go up to 700 rpm idle to be easier to move off line quickly w/o stalling absent mendedly, and to keep the air moving thru the radiator and engine compartment when standing still in traffic. This is a good time to have the lower engine cover in place as it's main function is to direct the cooling air thru thre engine compartment in a most eff way.

The official temp here in dallas two days go hit 110 F in the shade. So when you are stuck in a wide and stopped traffic jam on concrete with no overhead cover it is close to 125-130 itself, and then add the heat of all the other engines and people around you, the air temp can easily hit 135-140F. Maybe spike to more than that at times like 150 near a large truck.

It also keeps the coolant flowing faster too. In such conditions I have found that using my foot to keep my rpms around 1000 helps keep the electric fan off more than it would be other wise and keeps the engine a bit cooler. The electric fan does its job but does not move the coolant any faster. When the traffic moves I keep the car in a gear that will keep the rpm over over 2000 and move slowly up to the next car stop at least one car back. This may sound extreme to those not in such heat but it does work.

Then once we p/u some speed I still keep the rpms above 2-2500 for a few mins to give the cooling system time to cool down. More rpm creates more internal friction and move the coolant thru the radiator too fast to cool. But once moving I never get in a gear that drops the rpm below 1500 rpms.

On the other end of the spectrum a 6 or V8, with an automatic trans, will generate even more heat. If it's cooling system is in good shape it will survive normal driving and the lower idle rpm but it will not run as cool as the method above and put more stress on all components.

Running a SC, even w/o not running boost, will add to the engine and coolant temperature above.

Quality oil is a must in ALL such above situations. Good luck. We have had over 33 days of 100 plus that started in early June. This rest of this week will be in the 108 and 109s. The all time record here is 113, in the shade and not considering heat factor.
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Last edited by franka; 08-04-2011 at 03:32 AM.
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  #334  
Old 08-04-2011, 09:45 AM
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Flug540 Flug540 is offline
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Originally Posted by franka View Post
With a manual tranny and the heat in Dallas, as well as other West and Southwest locations like Phoenix, El Paso, etc I would like to go up to 700 rpm idle to be easier to move off line quickly w/o stalling absent mendedly, and to keep the air moving thru the radiator and engine compartment when standing still in traffic. This is a good time to have the lower engine cover in place as it's main function is to direct the cooling air thru thre engine compartment in a most eff way.

The official temp here in dallas two days go hit 110 F in the shade. So when you are stuck in a wide and stopped traffic jam on concrete with no overhead cover it is close to 125-130 itself, and then add the heat of all the other engines and people around you, the air temp can easily hit 135-140F. Maybe spike to more than that at times like 150 near a large truck.

It also keeps the coolant flowing faster too. In such conditions I have found that using my foot to keep my rpms around 1000 helps keep the electric fan off more than it would be other wise and keeps the engine a bit cooler. The electric fan does its job but does not move the coolant any faster. When the traffic moves I keep the car in a gear that will keep the rpm over over 2000 and move slowly up to the next car stop at least one car back. This may sound extreme to those not in such heat but it does work.

Then once we p/u some speed I still keep the rpms above 2-2500 for a few mins to give the cooling system time to cool down. More rpm creates more internal friction and move the coolant thru the radiator too fast to cool. But once moving I never get in a gear that drops the rpm below 1500 rpms.

On the other end of the spectrum a 6 or V8, with an automatic trans, will generate even more heat. If it's cooling system is in good shape it will survive normal driving and the lower idle rpm but it will not run as cool as the method above and put more stress on all components.

Running a SC, even w/o not running boost, will add to the engine and coolant temperature above.

Quality oil is a must in ALL such above situations. Good luck. We have had over 33 days of 100 plus that started in early June. This rest of this week will be in the 108 and 109s. The all time record here is 113, in the shade and not considering heat factor.
Wow! Thanks for sharing, great tips.

It never gets so brutal here in the Bay Area though. We have some customers in Dallas, they really like coming over and work from our office here.

I went for a drive today and thought it was a bit better in the lower RPM range. Could it be that it just needs some time to adjust DME? I read somewhere that it does automatically adjust with time.
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  #335  
Old 08-04-2011, 11:50 AM
franka franka is offline
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Could it be that it just needs some time to adjust DME? I read somewhere that it does automatically adjust with time.
Sorry but I can't speak to that particular aspect. But if its like the OEM DME it can take a couple of weeks to self adjust because it uses averages and that takes time to accumulate. Also the OEM DME will adapt to your driving style. If you have a heavy foot It'll adjust so that the throttle will open quicker and farther anticipating that that is what you will be wanting.

I also wanted to clarify the temps here in Dallas. We started in early June with temps over 100 F and fluctuated above and below 100 until the most recent past 34 consecutive days that have all been over 100. Going to 105 seems common place now. Some are saying we will break 110 or more this week. Most here, including me, have had enuff. It's physically and mentally wearing us down. I'll be leaving Dallas and going North for about a month on the 17th. I hope its cooler when I get back.
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  #336  
Old 08-04-2011, 02:07 PM
bobdmac bobdmac is offline
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Alex, you could well be right about the DME, but I think most of the "learning" they do concerns the shift points and throttle position in cars with automatic transmissions, not the basic idle speed.
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  #337  
Old 08-04-2011, 02:13 PM
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Flug540 Flug540 is offline
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Alex, you could well be right about the DME, but I think most of the "learning" they do concerns the shift points and throttle position in cars with automatic transmissions, not the basic idle speed.
I did not mean that in regards to idling, I meant in terms of how the power is applied. As I mentioned high RPM feels a lot more powerful, but lower RPM feels hesitating and lacking power. But today I felt it was changing for the better, hope it isn't just my wishful thinking
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  #338  
Old 08-04-2011, 02:20 PM
bobdmac bobdmac is offline
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Ah, okay. I misread your post. I frankly have no idea about the power application at higher RPM's. Even if it is only wishful thinking, this may be a case where perception=reality, practically speaking.
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  #339  
Old 08-04-2011, 08:13 PM
98540iA 98540iA is offline
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I did not mean that in regards to idling, I meant in terms of how the power is applied. As I mentioned high RPM feels a lot more powerful, but lower RPM feels hesitating and lacking power. But today I felt it was changing for the better, hope it isn't just my wishful thinking
What exhaust are you running?
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  #340  
Old 08-04-2011, 08:36 PM
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What exhaust are you running?
Stock... the plan is to replace the mufflers with a straight pipe.
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  #341  
Old 08-04-2011, 08:55 PM
98540iA 98540iA is offline
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I would replace the stock exhaust to compliment the powerplant you now have. A 14 year old tired exhaust system bolted to your rebuilt and s/c'd engine with headers is probably your problem with the lack of low end power. That big Y resonator plus the 2 big cans in the rear are not helping you. I had the rear straight piped for the last year it was lacking in the low end but then I put a bullet resonator (16-18 inch) in place of stock boomerang and put Flowmaster 40 muffler on back and it sounds mean and is noticeably more powerful at low rpm's. I think exhaust tuning is overlooked in performance tuning these cars, I wouldn't overlook it considering how much you've put into this already.
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  #342  
Old 08-04-2011, 08:58 PM
franka franka is offline
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I would replace the stock exhaust to compliment the power you now have. A 14 year old tired exhaust system bolted to your rebuilt and s/c'd engine is probably your problem with the lack of low end power.
So the exhaust system can handle wide open, high rpms but not the low end? I doubt that is the case.
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  #343  
Old 08-04-2011, 09:17 PM
98540iA 98540iA is offline
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I didn't say it couldn't handle it but I doubt its performing at the top of its game.... I figure if you rebuild the engine, put headers on, install supercharger.... then why not go the whole way. Upgrading everything except the exhaust does not seem very wise to me. Feel free to keep it stock if you want, I'm just offering an idea and it's what I would do.
Actually, if it was me who just put headers and supercharger on I would install an x-pipe after the cats with an 18" bullet resonator right off the x-pipes and run 2.25" tubing back from both resonators to the stock muffler area with 2 small mufflers exiting from stock position..... but this is not my project..... yet.
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  #344  
Old 08-05-2011, 08:41 AM
franka franka is offline
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I didn't say it couldn't handle it but I doubt its performing at the top of its game.... I figure if you rebuild the engine, put headers on, install supercharger.... then why not go the whole way. Upgrading everything except the exhaust does not seem very wise to me. Feel free to keep it stock if you want, I'm just offering an idea and it's what I would do.
Actually, if it was me who just put headers and supercharger on I would install an x-pipe after the cats with an 18" bullet resonator right off the x-pipes and run 2.25" tubing back from both resonators to the stock muffler area with 2 small mufflers exiting from stock position..... but this is not my project..... yet.
I agree about improving the exhaust w/a SC. But my point was that was not his low end problem, as you suggested it might be.

I already pointed out that Centrifugal SCs do not have good low end performance. They have good top end but not low end.
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  #345  
Old 08-05-2011, 11:38 AM
98540iA 98540iA is offline
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I agree about improving the exhaust w/a SC. But my point was that was not his low end problem, as you suggested it might be.

I already pointed out that Centrifugal SCs do not have good low end performance. They have good top end but not low end.
I saw your post and agree about top end gains but I disagree with you in that I think it is possible an old, stock exhaust might be the cause of the low end hesitation. I will tell you from experience that you can tune the exhaust to get more out of low end (perhaps at the cost of some high end but with a S/C I donít think much can be lost there). I experimented with my exhaust and with my current set up I gained low end power (3k and under) and since that is where I drive 95% of the time I am keeping it like this. It also cost me ~$300 for my entire custom exhaust so itís not a lot of $$$ but it sure can make a big difference for the better.
I am not saying the exhaust is to blame but I am proposing that it might be.....
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  #346  
Old 08-05-2011, 09:21 PM
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I experimented with my exhaust and with my current set up I gained low end power (3k and under) and since that is where I drive 95% of the time I am keeping it like this. It also cost me ~$300 for my entire custom exhaust so itís not a lot of $$$ but it sure can make a big difference for the better.
I am not saying the exhaust is to blame but I am proposing that it might be.....
What is your 'current set-up' ? Its a friendly question.
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  #347  
Old 08-06-2011, 07:46 AM
98540iA 98540iA is offline
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Current set-up is 18" bullet resonator in place of the stock Y-resonator, 2.5" tubing back to a Flowmaster 40 muffler. Before I put the resonator on I had a straight pipe (resonator delete) and it had a lot of rasp and I lost low end power versus the "muffler delete" set up I had previously. Upon installation of the bullet resonator, I gained significant punch in low to mid range. If I had s/c and headers I'd probably put an x-pipe after the cats, 2 bullet resonators coming out of the x-pipe and then run 2.25" tubing back to 2 small muffler exits or a dual in/out in the stock muffler position.
I'm an exhaust junky ;-)
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  #348  
Old 08-06-2011, 10:09 AM
franka franka is offline
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Originally Posted by 98540iA View Post
Current set-up is 18" bullet resonator in place of the stock Y-resonator, 2.5" tubing back to a Flowmaster 40 muffler. Before I put the resonator on I had a straight pipe (resonator delete) and it had a lot of rasp and I lost low end power versus the "muffler delete" set up I had previously. Upon installation of the bullet resonator, I gained significant punch in low to mid range. If I had s/c and headers I'd probably put an x-pipe after the cats, 2 bullet resonators coming out of the x-pipe and then run 2.25" tubing back to 2 small muffler exits or a dual in/out in the stock muffler position.
I'm an exhaust junky ;-)
So you are still running your OEM cats?
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  #349  
Old 08-06-2011, 10:29 AM
98540iA 98540iA is offline
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No, new hi flo cats one year ago. Had bad cat and after new ones I gained lots of power due to clogged bank 2.
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  #350  
Old 08-06-2011, 01:14 PM
franka franka is offline
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No, new hi flo cats one year ago. Had bad cat and after new ones I gained lots of power due to clogged bank 2.
One would gain power if the cat was clogged and then replaced. A clogged cat produces a huge drop in power.

So as I read it you put on a new cat and felt the original power return. What was the brand name of the new hi flow cat?

On a related subject, do you believe that a certain amount of back pressure is required for good low end power and throttle response?
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