[Tkenupp]

i had a problem where i didn't know that was a difference between 91 and acn 91(i'm in CA) and besides that i was fueling at sams club, then switched to shell nitro+, long story short i flashed the ECU for acn91 and the car got way better and know it's reaching 25psi. Should i be concerned of overboosting or something? Here's my log. the car has DP, 3 inch exhaust, IC , Stage 2 LPFP, brand new hpfp, CP , and a new diverter valve. This is my first modified turbo car, all the other ones were pretty much stock, i appreciate all the help. Thanks



https://datazap.me/u/tkenupp/top-tie...14&mark=24

[NoGuru]

You are about 4psi off target so you might have a boost leak or possibly solenoids.

[wheela]

Wow, that car is making some boost, are you sure it has a stock turbo in it? Obviously there is that big boost spike (and resultant throttle closure), but you're staying well above boost target even after the spike through the pull. I don't recall seeing any logs with the stock turbo and stage 2+ MHD tune being able to maintain that kind of boost???

As far as the overboost - boost is the tool the DME uses to hit the load request. You'll see that once your load actual hits load request, you get a throttle closure to prevent exceeding load request. Load is just a way to express air comsumption as a percentage of cylinder volume (load = cylinder stuffing factor). So the throttle closure is keeping air consumption into the cylinders on target. However, a lot of people don't like throttle closures because they beleive they can contribute to timing corrections, but I haven't seen a lot of solid data to support/deny this - I often get corrections at the start of a pull just like on your log, but I have 0 throttle closures. Plus the stock tune has a ton on throttle closures. But that high pressure spike is more wear and tear on everything upstream of the throttlebody, so probably not great.

Your short term fuel trim (stft) goes really negative throughout the pull. For example, at stft of -15%, your DME is removing 15% of fueling to hit it's afr target based on O2 sensor feedback (after adjusting fueling per ltft). This means without DME intervention, you'd he running richer than target - some possible causes could be a boost leak (loosing metered air) or excess fuel is getting injected that's unaccounted for by the DME for some reason (leaky injector maybe???)

Also, what tmap are you running? I didn't think the stock tmap could read that high.

[wheela]

When you flashed stage 2+, did you accidentally have the n20 tmap checkbox checked in the flash options menu? If this was checked, and you don't have the n20 tmap installed, un-check the box and re-flash your tune - that box should only be checked if you actually have a 3.5 bar tmap installed (stock tmap is 2.5 bar). Checking this box with the stock tmap installed would cause the boost reading to be higher than in reality, and maybe mess up some other stuff too.

[Tkenupp]

Originally Posted by wheela

Wow, that car is making some boost, are you sure it has a stock turbo in it? Obviously there is that big boost spike (and resultant throttle closure), but you're staying well above boost target even after the spike through the pull. I don't recall seeing any logs with the stock turbo and stage 2+ MHD tune being able to maintain that kind of boost???

As far as the overboost - boost is the tool the DME uses to hit the load request. You'll see that once your load actual hits load request, you get a throttle closure to prevent exceeding load request. Load is just a way to express air comsumption as a percentage of cylinder volume (load = cylinder stuffing factor). So the throttle closure is keeping air consumption into the cylinders on target. However, a lot of people don't like throttle closures because they beleive they can contribute to timing corrections, but I haven't seen a lot of solid data to support/deny this - I often get corrections at the start of a pull just like on your log, but I have 0 throttle closures. Plus the stock tune has a ton on throttle closures. But that high pressure spike is more wear and tear on everything upstream of the throttlebody, so probably not great.

Your short term fuel trim (stft) goes really negative throughout the pull. For example, at stft of -15%, your DME is removing 15% of fueling to hit it's afr target based on O2 sensor feedback (after adjusting fueling per ltft). This means without DME intervention, you'd he running richer than target - some possible causes could be a boost leak (loosing metered air) or excess fuel is getting injected that's unaccounted for by the DME for some reason (leaky injector maybe???)

Also, what tmap are you running? I didn't think the stock tmap could read that high.

hi there! Thank you very much for the report. the guy who sold me the car said to check the 3.5 bar tmap sensor box while flashing the map because he had
upgraded it. The car also has a precision racing stage 2 lpfp. Since i'm running rich i shouldn't be worried about a engine failure, right? I'm looking for an excuse to upgrade my turbo, so i wouldn't mind about a reduced lifespan of mine lol. looks i have an upgraded tmap sensor, do you believe is it better to run a e30 map ?

attached pic of the replaced sensor

[IMG]undefined[/IMG][IMG]undefined[/IMG]

[Tkenupp]

Originally Posted by wheela

When you flashed stage 2+, did you accidentally have the n20 tmap checkbox checked in the flash options menu? If this was checked, and you don't have the n20 tmap installed, un-check the box and re-flash your tune - that box should only be checked if you actually have a 3.5 bar tmap installed (stock tmap is 2.5 bar). Checking this box with the stock tmap installed would cause the boost reading to be higher than in reality, and maybe mess up some other stuff too.

hi! thanks for the reply, and yes, i did check the box because the last owner said he had upgraded the tmap sensor for one with 3.5 bar. i attached pictures of the old sensor.

[wheela]

In that pic, is that the sensor you're running now, or do you have a different one on now? Googling the p/n's in your picture, that seems to be an n55 2.5 bar tmap. Do you have p/n's from the tmap you're running in your car now?

[Tkenupp]

Originally Posted by wheela

In that pic, is that the sensor you're running now, or do you have a different one on now? Googling the p/n's in your picture, that seems to be an n55 2.5 bar tmap. Do you have p/n's from the tmap you're running in your car now?

my apologies for the pic, that was the best i could take. It is a 3.5 bar tmap. Would be better run a e30 map? thanks


[IMG]undefined[/IMG]

[wheela]

Thanks for the new pic! I apologize, I took another look at your log, and after the spike I must have been looking at the boost target curve instead of the boost curve - the spike isn't normal, but that level of boost after the spike for the rest of the pull looks pretty doable for a stock turbo. But it looks like your wastegate duty cycle may be a little high? I don't know, on my stage 2+ logs the wastegate duty cycle usually stays in the 50's or 60's after spool. As no guru mentioned, there could be a small boost leak. But in general, these OTS MHD tunes for e-chassis n55 generally run under target on most cars, especially in upper rpm range.

If you'd like to try e30, you may want to try ruling out a boost leak first if you want to be easy on your turbo. It doesn't take much of a leak to throw things off, you could start by just tightening all of the clamps you find before the throttle body, take a log and see if the negative stft gets closer to zero, and if wastegate duty cycle drops. Other than that I'd say give it a try. I'd keep an eye on high fuel pressure in your logs to make sure everything is keeping up with the increased fuel demand. The e30 may even help clear up some timing corrections.

As far as safety of the engine, I agree with you - since stft is pulling fuel to stay on afr target I think that's safer for your engine than if it was adding stft to get to target.

Any thoughts from the peanut gallery? I'd love to hear some other opinions

[TheGoodTheBadTheUgly]

I have 28.4 psi overboost here and I was NEVER able to figure out why. Swapped my vacuum lines, used a friend's boost solenoid, all that's left is to remove downpipe and see if the wastegate actuation is good, but I don't feel like doing so since it's such a pain on the xDrive. I have the n20 TMAP sensor.

https://datazap.me/u/thegoodthebadth...og=0&data=4-21

[BimmerHausPerformance]

Originally Posted by TheGoodTheBadTheUgly

I have 28.4 psi overboost here and I was NEVER able to figure out why. Swapped my vacuum lines, used a friend's boost solenoid, all that's left is to remove downpipe and see if the wastegate actuation is good, but I don't feel like doing so since it's such a pain on the xDrive. I have the n20 TMAP sensor.

https://datazap.me/u/thegoodthebadth...&data=4-21

It looks to me like it would be your tune, or your tune needs adjustment. If you look at your target boost, and your throttle position, with your actual PSi they all correlate. There is no way you are actually feeding 28lbs into your engine, your throttle plate starts to close to prevent overboost into the motor and that creates a bottleneck in your charge pipe which raises the pressure (right where you are reading the PSI). So technically you are overboosting but not at 28lbs. Your wastegate should be double checked but I would get with a good tuner.

[BimmerHausPerformance]

Originally Posted by BrowBMW

It looks to me like it would be your tune, or your tune needs adjustment. If you look at your target boost, and your throttle position, with your actual PSi they all correlate. There is no way you are actually feeding 28lbs into your engine, your throttle plate starts to close to prevent overboost into the motor and that creates a bottleneck in your charge pipe which raises the pressure (right where you are reading the PSI). So technically you are overboosting but not at 28lbs. Your wastegate should be double checked but I would get with a good tuner.

Same situation with the OP.

[Tkenupp]

Hey guys! I just replaced the boost solenoid and the boost still all over the place, this time started hitting 18, then 19, then 22 and lastly 23.9 psi. However when i was running stage2 only, barely passed 18 psi.

I'll post some logs soon. Thanks!

[TheGoodTheBadTheUgly]

As BrowBMW mentioned, I really think the issue is related to the imperfection of the OTS maps. I am almost positive that if we were to get a custom tune, this would easily get fixed.

I know the OTS Maps have had an update, don't know if this could help, but hardware-wise I have almost tried everything possible expect checking on the wastegate. In the past I upgraded DV, change my vacuum hoses and solenoid as well.

[Tkenupp]

I agree! I'm running the new map , e30 on stage 2. The car now is within the boost margin of 19.9 psi peak(mostly less than 18psi) during a 3 hour canyon drive session. The car stil getting 7 degree timming corrections on some cylinders sometimes. I'll be getting a custom map when i finish the suspension upgrades.