[savannahz]

Hey,

I'm experiencing an issue of where I hit target boost quickly, overboost slightly, and then steadily lose boost over the pull. By the end of third gear I'm 5.5 pounds down from target. I've checked the charge pipe and o-ring, all cp connections and re-did the top (easy to get to) vacuum lines with silicone. I'm going to do the rest of the vacuum lines this weekend. I'm also going to check my intercooler hoses.

The car is running great, with tons of power, and I only would have known there was an issue by looking at the logs. I'm running beta 8 mhd and am fbo.

From what I've described, what could be my issue? I've read a lot about people with boost leaks who couldn't reach target, but haven't read any who could and then slowly siphoned off. I guess it could mean just a smaller leak somewhere?

Here is my datalog: https://datazap.me/u/savannahz/boost...&data=2-3-4-19

Thanks

[RSL]

If it's the same issue (and appears to be), haven't seen that in a while and 2 now within a week. Figured it was an MSD80 / I8A0S + cooler weather thing and so far, yours follows that pattern. No clue how to work around, but you're not alone. PID isn't doing tons, so if you log boost mean and that's on/close to target, your issue is probably an MAF limit.

http://www.e90post.com/forums/showthread.php?t=1313558

Originally Posted by RSL

Boost mean is actual TMAP reading, boost is DME modeled boost, so something is going on between reality and what the DME thinks is going on.

https://datazap.me/u/phob/log-151196...-22&solo=18-19

I've seen this issue before, person said it resolved itself after not boosting for a while. It was also a 2007, so might be something specific to the MSD80/I8A0S and maybe weather conditions?

From 2012:

[savannahz]

My first number does seem inline with the post you shared. The second number seems healthy?

MAF (g/s) hit 285.15

and

MAF req (wgdc) (g/s) hit 407.7

[RSL]

It means I don't think you have an actual boost leak, I think the DME is modeling and reporting boost (boost psi) based on a capped MAF. Next time you log, add load actual, load request and boost mean.

...but careful logging, DME may just be seeing less boost than you're actually running.

[savannahz]

I'll add these values and log on the way home. Thanks

[savannahz]

ok, I put the boost mean psi, load required and load actual in the log:

https://datazap.me/u/savannahz/possi...3-4-5-12-13-19

Thanks!

[RSL]

Yep, not a boost leak, it's capped MAF.

Boost mean is the average actual boost you're running base on TMAP. Boost mean is the boost the DME is calculating, which is low based on the limited MAF.

Essentially running 14psi up top, but DME is only running load/tune for 10-11psi (lower load, leaner AFR, more timing, less torque output, etc). It's not ideal and the larger the spread between boost psi and boost mean (with boost psi lower), the more careful you need to be. Nothing seems too ticked off right now, but that doesn't mean it will stay that way.

As I said before, I don't know of a work around and it will probably go away at some point (warmer weather), but might consider working with a tuner while the situation is present to see if they can clear it up.

[savannahz]

thanks so much for your help!

[BaaQaf]

Too much valve overlap or air restriction. Valve overlap affects cars differently depending on mods and altitude. It may have been done this way to encourage tapper

[savannahz]

Originally Posted by BaaQaf

Too much valve overlap or air restriction. Valve overlap affects cars differently depending on mods and altitude. It may have been done this way to encourage tapper

I did recently take off my Mr. 5 dual CAI and just dropped a K&N panel filter into the stock housing. I've read this isn't an issue and provides enough air flow, but I could switch it back to see.

[Sgop335]

it is maf capped, right about 285g/s. Why tho? I don't see throttle in the log (many useless channels but not throttle) it must be closing to reduce your boost. this is not your air box since boost mean is following target ok (meaning you are building boost), it must be the throttle.

[savannahz]

I'll take a log with throttle position this afternoon, thanks!

[savannahz]

Here is the log with throttle position included. It takes a dip at the front of the run, but holds steady all the way to the end:

https://datazap.me/u/savannahz/throt...-5-18-19-22-25

Thanks

[Sgop335]

Originally Posted by savannahz

Here is the log with throttle position included. It takes a dip at the front of the run, but holds steady all the way to the end:

https://datazap.me/u/savannahz/throt...-5-18-19-22-25

Thanks

Your boost is dropping dont know why or how. Throttle seems fine.

[savannahz]

Yeah, I'm going to hopefully have time Friday to check the:

1. intercooler hoses as I have an aftermarket unit and the silicon hoses have given me trouble in the past.

2. manifold as I did recently clean my valves.

3. finish replacing my vacuum hoses (I'm half done).

Past that, I'll do a boost leak test by pressurizing the system with my air compressor.

Thanks

[Sgop335]

Originally Posted by savannahz

Yeah, I'm going to hopefully have time Friday to check the:

1. intercooler hoses as I have an aftermarket unit and the silicon hoses have given me trouble in the past.

2. manifold as I did recently clean my valves.

3. finish replacing my vacuum hoses (I'm half done).

Past that, I'll do a boost leak test by pressurizing the system with my air compressor.

Thanks

all those will help anyway.

Boost is not a measured qty in our great n54. Boost mean is. Boost is then computed from boost mean, throttle position etc. Typically when throttle is fully open (81%) boost and boost mean are quite close, unlike yours where they are moving apart and throttle is fully open. If there is a boost leak it should be reflected in boost mean (there may be still be a leak in your case since boost mean is barely keeping up w target). But its not as bad as boost. Still pointing towards that mysterious 285g/s maf cap. What I don't understand is physically how is the boost reduced in the log? Since the last line of defense (the throttle) is fully open. dme reporting error?

[savannahz]

Great news...my issue is resolved.

I tried several things before I found what fixed it. Boost solenoids - didn't resolve, but made the car much better to drive. The car felt like I was pushing it and it and now it feels like it's pulling me (hopefully this makes sense).

I changed all vacuum hoses to silicon.

This weekend I changed out my o-rings in the divertor valves (x4). I noticed when doing my pressure test that they leaked when I touched them. I got new ones from McMaster and changed out the large one at the throttle body connector with one from an oil filter. I ran a quick log this morning and my boost all runs together as it should. When I pushed the diverters back into the charge pipe the connection was very firm and had resistance. Before, they just slid in very easily.

I should also note: I flashed MHD back to stock and then back to version 7 at the same time I did the seals. Not sure exactly which fixed it. Either way, the car feels better than ever.

Thanks again for all the help!

log:https://datazap.me/u/savannahz/after...&data=3-4-5-21

[Sgop335]

Originally Posted by savannahz

Great news...my issue is resolved.

I tried several things before I found what fixed it. Boost solenoids - didn't resolve, but made the car much better to drive. The car felt like I was pushing it and it and now it feels like it's pulling me (hopefully this makes sense).

I changed all vacuum hoses to silicon.

This weekend I changed out my o-rings in the divertor valves (x4). I noticed when doing my pressure test that they leaked when I touched them. I got new ones from McMaster and changed out the large one at the throttle body connector with one from an oil filter. I ran a quick log this morning and my boost all runs together as it should. When I pushed the diverters back into the charge pipe the connection was very firm and had resistance. Before, they just slid in very easily.

I should also note: I flashed MHD back to stock and then back to version 7 at the same time I did the seals. Not sure exactly which fixed it. Either way, the car feels better than ever.

Thanks again for all the help!

log:https://datazap.me/u/savannahz/after...&data=3-4-5-21

Log looks good and is resolved except for some overboosting and low lpfp pressures. So watch that. Not sure what fixed. Could hav been the reflash, of course as mentioned earlier other things helped. Can you post part # of diverter valve o ring?

[savannahz]

I found this part in another thread. This is from my order from McMaster. Unfortunately, they only come in a pack of 50:

Line Product Ordered Ships Price Total
1 9262K553 Oil-Resistant Buna-N O-Ring, 3.5 mm Wide, 24 mm ID, packs of 50 1
pack today
15.35
per pack 15.35
Merchandise $15.35
Applicable shipping and tax will be added.