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Discussion Starter · #1 · (Edited)
Hi
I think I'm a bit low on power. My car goes dead even with an M3 with Dinan exaust, filter and chip until 4th gear, and I start pulling away in 5th. An Audi RS4 with no cats slightly pulled on me in 2nd and 3rd gear. I saw 300 on the speedo, but i think the car should have pulled harder to that speed.
I recently changed one MAF, so maybe the other one is giving up. I have no cats. It is also possible the chip hasn't been done perfectly.
My car is a MY 99 Euro.
So here are my questions:
First of all, I'd like to get an Air/Fuel measuring out of the dyno, and for that I understand a probe has to be inserted into the exhaust, and a hole has to be drilled. Where, in the exhaust system, should I have this hole made by the exhaust shop?
Second. Do I have to pull any fuses on my car for it to work regularly on the dyno? If so, which ones?
Thank you very much, any further advice will also be appreciated. I'll post results as soon as I get them.
Greetings,
Raul
 

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silverstone400 said:
Hi
I think I'm a bit low on power. My car goes dead even with an M3 with Dinan exaust, filter and chip until 4th gear, and I start pulling away in 5th. An Audi RS4 with no cats slightly pulled on me in 2nd and 3rd gear. I saw 300 on the speedo, but i think the car should have pulled harder to that speed.
I recently changed one MAF, so maybe the other one is giving up. I have no cats. It is also possible the chip hasn't been done perfectly.
My car is a MY 99 Euro.
So here are my questions:
First of all, I'd like to get an Air/Fuel measuring out of the dyno, and for that I understand a probe has to be inserted into the exhaust, and a hole has to be drilled. Where, in the exhaust system, should I have this hole made by the exhaust shop?
Second. Do I have to pull any fuses on my car for it to work regularly on the dyno? If so, which ones?
Thank you very much, any further advice will also be appreciated. I'll post results as soon as I get them.
Greetings,
Raul
Most shops just put a probe in the tailpipe. Not the most accurate, but you are looking for mid to low 12's or very high 11's ( a little rich but safe) on the AF ratio. Pull fuses 17 and 30. Try to use 5th gear, that is 1:1 gearing. Have fun!
Regards,
Jerry
 

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Gsfent posted the most important stuff. I´d just like to add a few details:

If one MAF gave up, you might just as well replace the other one too.

Put new original paper intake air filters in as well. Those steal a lot of power when dirty.

Run high octane commercial fuel.

Try to keep the engine as cool as possible during the dyno runs. Get as much air flowing into the engine compartment as possible. Have the bonnet (hood) open.

Measure the intake air temperature, the barometric pressure and the relative humidity. This is absolutely necessary in order to be able to compare your data with other dyno data.

Try to make the dyno session in as cold air as possible, and at high (or at least) normal barometric pressure.

I´d like to ask you to do me a favour, make the dyno runs from really low RPMs. Like 800 RPM upwards. Then post the graphs here, please.

Enjoy the Dyno Roar!

Best Regs,

David
 

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BTW, I don´t think you need to drill a hole for the O2 sensor, unless you want to do precision tuning work. It would be a waste of time and money, and potentially a bit risky for the engine. I wouldn´t do it.

If you do decide to do that anyway, I´d like to share what a very good tuner once told me on this matter:

He said to put the sensor as close as possible to the engine, and to use a new and very sharp hole-saw suited for stainless steel cutting, not a drill bit. Put a lot of grease on the hole-saw and run the drill-machine very slowly. After the hole is open, check carefully for any loose metal or burrs. Deburr very carefully both inside and outside. Any loose metal at this location can easily be sucked back into the engine and cause catastrophic mechanical failure by scratching the cylinder walls.

When the hole is open you need to weld a nut in place to allow mounting the sensor. The weld should be gas-tight. It is difficult to weld stainless steel.

When you choose the location to place the O2-sensor bear in mind that the engine moves a lot on its rubber mounts, so check that you have enough clearance.

To repeat, I do not think you will need more than putting an ordinairy tail-pipe AFR O2-sensor into the exhaust tube. I advice against cutting into the exhaust pipes, but if you do so, then do it right.

Best Regs,

David
 

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MPRESIV said:
Is this for stock 3:15 final gear ratio or 3:45?
Or are they the same?
Transmission 5th is 1:1 regardless of diff. The diff ratio makes no difference, which is why you can (and many do ) dyno in 4th gear and get a decent result. Some dyno operators don't like using 5th gear because of the really high wheel/dyno speeds.
I don't completely understand why, i'd think lower gears would put more torque to the wheels and give a different result, but i assume you're just measuring acceleration of the dyno drum, and calculating from there.
 

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Discussion Starter · #7 ·
Thank you very much for the replys guys...
David, as for the O2 sensor, I get what you're saying, I'd prefer not to make a hole in the exhaust, but I think that with this shop it's the only possible way of getting the Air/Fuel results. I'll call one of these days and ask them if the probe can be placed at the back, without needing to drill the exhaust, but a friend of mine that went there told me he had to drill his, so I don't think there's an option. Thanks for the detailed explanation of how to make the holes, I'll supervise the procedure at the exhaust shop.
I told my dad he should have gotten both MAFs at once, but sometimes he can be such a cheap mofo.
I'll be making the runs from 800 to about 7500 RPMS, in fifth gear if possible.
Once I pull fuses 17 & 30 should I touch the DSC button to turn it off? Will sport mode be enabled?
Thank you very much for your help,
Raul
 

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since you don't have cats, i wonder if you could use the factory post cat hole (where the o2 sensor would be) for you AFR.

No, you don't need sport mode, and when the fuses are out, you can't engage it, i believe.
mike
 

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mottati said:
since you don't have cats, i wonder if you could use the factory post cat hole (where the o2 sensor would be) for you AFR.

No, you don't need sport mode, and when the fuses are out, you can't engage it, i believe.
mike
Are you sure abou that? So i should accept that the sport feature is offline when DSC fuses are pulled out?
 

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Ahmed said:
Are you sure abou that? So i should accept that the sport feature is offline when DSC fuses are pulled out?
I;m not positive, but that's what i've read on this board (can't engage sport mode with fuses 17 and 30 removed). At any rate, sport mode makes no difference on the dyno, as far as the numbers go.
Mike
 

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mottati said:
I;m not positive, but that's what i've read on this board (can't engage sport mode with fuses 17 and 30 removed). At any rate, sport mode makes no difference on the dyno, as far as the numbers go.
Mike
I have to agree with Mike...When my car was on the dyno, with the fuses pulled, we could not engage sport mode...

Mark
 

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mottati said:
since you don't have cats, i wonder if you could use the factory post cat hole (where the o2 sensor would be) for you AFR.

No, you don't need sport mode, and when the fuses are out, you can't engage it, i believe.
mike
That is a brilliant solution!

David
 

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mottati said:
At any rate, sport mode makes no difference on the dyno, as far as the numbers go.
Mike
Are you sure of that too? Sorry for all the questions, its just that i'll be dynoing my car and dont want any surprises!
 

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Sport mode only makes an adjustment to the rate of throttle applications. Once wide open (ie sport or not) the throttle butterflies can only be open so much. Once they are at WOT, the HP number the S62 makes will be the same sport mode or not. Sport mode doesnt make more HP, it just makes the throttle sharper to inputs...
:cheers:
 

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silverstone400 said:
...I told my dad he should have gotten both MAFs at once, but sometimes he can be such a cheap mofo.
I'll be making the runs from 800 to about 7500 RPMS, in fifth gear if possible.
Raul,

Thanks for keeping the low RPM measurements in mind! I appreciate it a lot.

When I think about it, it is probably a good idea to rule out a simple MAF problem before you spend the time & money on the dyno session.

You can easily test the function of MAFs yourself. Look at:

http://www.m5board.com/vbulletin/showthread.php?t=54788

If the conclusion after test is that you need new MAFs, and you want to get it at the lowest possible cost, look at:

http://www.m5board.com/vbulletin/showthread.php?t=55391

David
 

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Discussion Starter · #18 ·
David, unfortunately I can't check If my MAFs are working well using the method of checking the fuel consumption with the OBC, because some of the pixels on my dashboard aren't working. Its strange, because some days they work well, and some they don't. I'll have to be lucky enough to use the car on one of its good days.
I'm very interested in that alternative to replacing the whole MAF unit by the dealer, I hope they get good results.
Greetings,
Raul
 

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Get a scan-tool!

Raul,

The dashboard pixel problem is very well known. It happens more or less to 100% of the E39s.

There is a connection betwen a printed circuit-board and the LCD, which is pressed together by a piece of sheet-metal. If the pressure is too low you get a bad connection. It is very dependent of temperature and humidity.

Let me guess: the display in your car works better on cold wet days?

If you were in the US, BMW NA would cover the replacement. Maybe the Argentinian BMW has a similair policy? Check with your kind SA.

Anyway, to test the MAFs you can also use an OBD-II scan-tool. Then you don´t need to look at the dashboard display.

I have described that method too in the MAf testing post linked to earlier in this thread.

Do you have a laptop? If so you can get a good scan-tool for US$ 100.

How much does the dyno-run cost?

David
 

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Discussion Starter · #20 ·
Let me guess: the display in your car works better on cold wet days?
I hadn't thought it that way, but it is very possible.

BMW of Argentina doesn't have that policy, unfortunately. Now that I think about it, a shop I take my cars for simple stuff has an OBD 2 scanner, I'll try with theirs.

The dyno run costs $100 pesos, and more or less 3 pesos = 1 dollar. So it costs approximately US$33

Raul
 
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