What happens at 3900 rpms on a S52 that always causes a dip in hp and torque?

I would also want to know, I have a AA sc 95 m3 which also dip around the rpm that made it loose hp and tq.

Are you sure? That is when VANOS kicks in; rpms drops for a moment because of the additional air (meaning that your HP and TQ just increased); I can't think of anything that would happen at that rpm that would make you lose power...

In fact, I lost power when I did my M50 manifold on the low end and I don't feel any better power until the VANOS kicks in because that is when it can take the full advantage of the higher flowing intake mani.

I would also want to know, I have a AA sc 95 m3 which also dip around the rpm that made it loose hp and tq.
I think he is talking about stock; your car is S/C with new software... isn't your VANOS disabled too?

Better not be, there's no good reason to disable it besides a tuner not knowing what they're doing.

Better not be, there's no good reason to disable it besides a tuner not knowing what they're doing.
My bad, you're right I was thinking E46 that tuners have problems keeping vanos running.

No the vanos is not disabled, when I got it dynoed they said it could be that the A/F ratio was causing the dip not supplying enough fuel.Could it be software?

At 3900??? Do you mean 4900?

http://i19.photobucket.com/albums/b162/galleyan/Stock.jpg

Like that?

I was under the impression VANOS kicks in right at about 5000rpm, thus resulting in that sudden "dip" in power while it's switching profiles.

PS: I no longer have that "dip" on any of my dyno graphs after going TT Stage 1.

http://www.368s.com/photos/photo001468_large.jpg





Juker008

il post my dyno sheets as soon as i can

From what I understand Vanos advances the intake cam at about 3500-3800 and retards at 5200-5500. The reason I asked is that my turbo setup does fine up to 3900 rpms and then goes in the toilet, even looses hp until it starts coming back at 5200 and then continues gaining power up tp redline. These dips are much worse in higher gear dyno pulls than third gear where it hits redline exxtemely quick. I'm wondering if this is a fuel problem that shows itself when the cams advance 12 degrees imcreasing valve overlap and fuel needs or a timing issue and the knock sensors are pulling the timing? My AEM shows no leaner than 12.8 all the way to redline. I'll post dyno's tomorrow to demonstrate what is happening.

That's wierd.. I can't imagine your VANOS unit being faulty w/ only 29k.. No clue on what it could be :help

PS: I no longer have that "dip" on any of my dyno graphs after going TT Stage 1.
To me, that indicates your previous inferior tuning (or current superior tuning).

To me, that indicates your previous inferior tuning (or current superior tuning).

Both!

Previous tuning was ... dun dun dun.. BMW! Bone stock.. haha..

Nick is, CLEARLY... and I mean.. CLEARLY.. > BMW.. :buttrock

here is the dyno sheets

here is the dyno sheets

How many miles on that motor? The only thing I can personally think of (and I may be WAY off) is that your VANOS unit has failed. Don't quote me on that, but that's literally the only thing I can think of that would make it die when in the VANOS curve, and then come back on once it's back on the normal profile.

On that plot, I see the clear negative spike of about 50 wftlbs at around 3700 rpms. Then the trq curve seems to continue on, as if never interrupted by the neg spike around 4300 rpms. But i dont think that means vanos hits at 3700, and again at 4300. Or that it turns 'on' at 3700 and 'off' at 4300.. Im just not sure how to interpret that plot in terms of vanos operation or non-operation.

Are you sure that the dyno run in question didn't include an upshift rather than measurements during one continuous sweep? If it's legitimately there, you WILL feel a HUGE gap in power (as you sweep through this specific RPM range) followed by the definitive return of power on the street if you were to go WOT early. ...looks fishy...

Yea.. that is clearly NOT what a 'normal' or properly running M3 under forced induction, or otherwise, should look like.

Well Iam replacing the vanos unit today let you know what happens

There's a problem there dude ...

Well Iam replacing the vanos unit today let you know what happens

That trq dip in your plot represents a sudden power drop of something like 50 ft lbs as I recall.. From what I thought, the Vanos doesnt contribute anywhere Near that amount of power. So Id be very surprised if a vanos 'problem' was solely responsible for your large power dip, but, let us know what you find for sure.

What do you think is going on here?

>>What do you think is going on here?<<

This looks like alot of AA charts Ive seen wrt shape. SAE correction would have reduced those numbers somewhat, but what youre talking about is shape of the curve, and it doesnt look all that unusual to me for what youve got. It does seem a little 'lumpy', but I dont think its excessively so. And if you took the chart and stretched it out some along its x axis from left to right, it would smooth out the lumpiness, making it look very 'normal'.

What do you think is going on here?

Looks pretty normal to me, actually. boostedm3freak's is the one that is clearly not working correctly.

well replaced the vanos today.felt a difference in low rpm's, have not reved high yet .I just need to dyno it now. Ill post the result as soon as I dyno it.

Hey boosted-I pulled my Vanos and re-installed it to make sure I had done it correctly when I did my headgasket about a year ago. I don't think I had it installed properly before because the splined cup that engauges the cam was extended all the way without being activated. I also did the test after the reinstall with an airline and by jumping the Vanos leads and the unit moved the 8.5 mm it was supposed to. I drove the car and it felt worse so I started wondering if I had screwed the Vanos up again. I jumped the Vanos unit with the car running at idle and when the intake cam advanced it pulled the idle way down and it became rough so I'm sure Vanos is working.

I haven't re-dynod yet so I don't know what I have now. Unfortunately the dyno is down and they can't even download the previous dyno's so I can't even post, but my dip looks considerably different from yours. Mine actually doesn't recover until 5300 rpms and my torque and horsepower lines are very loopy through this 1500 rpm range. I just posted a new thread about knock sensors possibly being bad causing my timing to be pulled.

Sorry to show my inexperience here but I'm dealing with a similar problem at different RPM and I have not measured it with a wideband yet or dyno.

One area I suspect could be my problem is not the VANOS but the HFM and air mass meter. If the voltage coming from the HFM going back to the DME is not sufficient during WOT acceleration, won't the DME trim back fuel and in turn cause a lean condition resulting in a loss of power?

My problem extends beyond tonym though where I get bucking between 3500 RPM to 3900 RPM during the power loss. Do you get any bucking tonym or does the car stay smooth during the whole process?

Here is a copy of the dyno from a couple of weeks ago. What is happening at 3900 rpms on the 4th gear pulls? Is it timing being pulled? Unfortunately, their afr wasn't working but my AEM wideband guage is showing a consistent 11.8 to 12.2 under there wot pulls. Help!

Here is a copy of the dyno from a couple of weeks ago. What is happening at 3900 rpms on the 4th gear pulls? Is it timing being pulled? Unfortunately, their afr wasn't working but my AEM wideband guage is showing a consistent 11.8 to 12.2 under there wot pulls. Help!

Tony, pic isnt showing up... just an empty attachment box.

It's showing up on mine. The same dyno is shown on the clutch chatter post. What do you think?

Sounds to me that the injectors are too small. Granted that your AFRs are fine, I believe that the car is pullign timing.

AA = FTW :stickoutt

Pull an OBDII scan while you are on the dyno. See what your injector duty cycle is along with your knock values.



Juker008

Sounds to me that the injectors are too small. Granted that your AFRs are fine, I believe that the car is pullign timing.

AA = FTW :stickoutt

Pull an OBDII scan while you are on the dyno. See what your injector duty cycle is along with your knock values.

Juker008
If injectors were too small you would dip lean since your running out of needed fuel, no?. 30lbers do seem a bit low for 10lbs boost though.

Tony did you ever have misfire codes? Any coil issues? When my coils were on the way out i had a big dip in the first few dyno runs only for them to give out a week later with no previous precaution. At first i had some serious dips around 4000rpm when boost started kicking in on my SC.,

I have this issue on my na 328i. I'm leaning towards vanos solenoid ,alfunction

30lb. injectors are too small for the power your making!How are your afr's?

I'm sorry guys. I need to update my info. I'm now TT MAF, 36 lb injectors, and tuning. It's weird that whatever is causing the problem, only happens in 4th gear pulls and seems to correct itself around 5000 rpms.

I'm sorry guys. I need to update my info. I'm now TT MAF, 36 lb injectors, and tuning. It's weird that whatever is causing the problem, only happens in 4th gear pulls and seems to correct itself around 5000 rpms.

Even more precisely, Tony installed a second-hand ECU tuned for a completely different setup than what he has (cause we all know the question will come up........).

well, you have massive dips in power in the 4000 to 5500 rpm range, usually where the VE would peak... except in 3rd gear where you don't build as much load.
Looks like too much timing in that mid RPM range.

This could also mean too much timing for the load that is built on the dyno, and it could be fine on the street. thats one of the hard parts about tuning on a dyno. It doesn't always build the same amount of load as would be seen in real world conditions.

I'd still get it retuned.

you ever fix your wastegate issue?

I'm sorry guys. I need to update my info. I'm now TT MAF, 36 lb injectors, and tuning. It's weird that whatever is causing the problem, only happens in 4th gear pulls and seems to correct itself around 5000 rpms.


Active 30 lb injectors and remapped
ecu...


Might want to change that.





Juker008