Author Topic: Barometric Pressure Mod yields 10% HP/TQ gain  (Read 2524 times)

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Rusty

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Barometric Pressure Mod yields 10% HP/TQ gain
« on: February 01, 2005, 01:47:37 PM »
Barometric Pressure Mod yields 10% HP/TQ gain

Remember this?: Adjust Timing using Barometric Pressure Circuit

I did some more experimenting, and went from 200WTQ/170WHP to 220WTQ/190WHP. This was gained by setting the barometric pressure signal equivalent to near sea-level. Here's the before and after dynos:




The "before" dyno is one that's been repeated a LOT of times - I thought I was going to be stuck there until I got some fuel management.  I ran four dynos "after" and they all agreed.  Seat-of-the-pants it's been a tremendous punch, even better at lower altitude.  After doing this mod I drove to Tennessee and back for Christmas.   The car ran flawlessly at all altitudes in-between, and pulled like a mule at 1500 ft. with five people in the car.

I do not know why the mod does what it does.  :confused:  I have suspicions, but that's all - I suspect it primarily modifies lamda regulation, making it run richer closed-loop.  Secondarily, maybe alters load tables, and may or may not affect timing directly.  The reason I suspect lamba regulation is that, as I adjusted the device "downward" elevation-wise, the car started gaining boost while running richer (O2 sensor voltages increasing during open-loop). I compensated this behavior by turning down the peak fuel pressure on my Cartech, from 90 to 75 psi.  And my fuel trims actually went richer, from -6% to -5% or so.  If the ECU knew it was running richer, it would have trimmed out more fuel, i.e. gone more negative. So I got almost 20 extra HP with 15 lbs less peak fuel pressure than when I started.

I missed this O2 behavior the last time I tried the lower altitude (parallel-resistance) settings, because I wasn't logging O2 voltage.  I only logged O2 for the higher altitude, series-resistance settings.

The other reason I think lambda reg (or maybe load table adjustment) is that it pulls so much stronger during closed-loop.  Around town, I have so much power now, it takes very little boost to keep abreast of traffic; as a result, around-town mileage has gone up from 15 to 20mpg.  Highway mileage is about the same, 28-32 depending on how fast I go.  It'll be interesting to see my next emissions inpection report.

I used the "retard timing" a.k.a. "lower the altitude" setup, where the added resistance is in parallel with the signal, thus lowering the effective resistance, corresponding with lower altitude.  The final value was 2-1/2 turns on my 50K Ohm 10-turn pot, which is 12.5K Ohms.  The total effective resistance calculates to be 2.58K, which is 72 feet based on the altitude data I logged (see first baro pressure post).

The funny thing is that the VAG-COM data block for barometric pressure compensation doesn't agree with this.  At my altitude of 5300 ft, the value is typically -17%.  I would expect it to go to zero or near zero, but it's currently reading -21%. :confused:  Whatever - it works!

I'd like to see someone else try this... at your own risk, of course.  Log a bunch of data and pay attention to it.  I can't guarantee anything other than it works in my car.  It would be interesting to see the effects on other engines, especially other engine codes - mine's a cable-throttle AEB.  Maybe this interacts in a fortuitous way with one of my other mods, like the Holey MAF?  With that in mind, here's the mod list:

'98 AEB cable-throttle engine
Stock ECU (Motronic 5.9.2 IIRC)
Stock K03 turbo
Stock 2.25" exhaust (with resonator removed)
COAM (Colorado Outlaw Airbox Mod)
Dawes MBC 15lbs boost
440cc injectors
2 bar base fuel pressure
5 bar fuel pressure at max boost via Cartech FMU
'Holey' MAF
Port-matched intake
Port-matched exhaust
FMIC
Baro Mod
i]AEB Engines have better-flowing heads and a real throttle cable...[/i]

jayryan

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Barometric Pressure Mod yields 10% HP/TQ gain
« Reply #1 on: February 01, 2005, 02:31:49 PM »
I was read this over on CB5...you're nuts! Very cool.
'03 A4 1.8TQM
'68 MG C
'06 4Runner

Rocky Mountain Club B5

Barometric Pressure Mod yields 10% HP/TQ gain
« Reply #1 on: February 01, 2005, 02:31:49 PM »

Chas

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Barometric Pressure Mod yields 10% HP/TQ gain
« Reply #2 on: February 02, 2005, 02:08:15 AM »
Very Cool Rusty!! Neat and elegant as well! I would love to give it a go. I'll have to look up all your past threads. I'm sure I read those in the past and you had a list of the parts needed to make the Baro adjustment kit. If I remember correctly it wasn't too difficult, but slightly costly for the one major bit of electronics.

I'll look into it.
2003 Audi A6 2.7T
Some Sedans haul families,
this one hauls ASS!

Rusty

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Barometric Pressure Mod yields 10% HP/TQ gain
« Reply #3 on: February 02, 2005, 02:37:05 AM »
I used a high-quality, 10-turn pot from the parts bin.  It was only an accident that it would have cost $90 new.  I'm sure you can get a perfectly adequate one for $10-$20.
i]AEB Engines have better-flowing heads and a real throttle cable...[/i]

Chas

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Barometric Pressure Mod yields 10% HP/TQ gain
« Reply #4 on: February 02, 2005, 09:13:14 PM »
So did you leave the settings on the 10 turn pot the same as what you had back when you first tried this? Is this the only thing needed or would you suggest the new plugs as well?
2003 Audi A6 2.7T
Some Sedans haul families,
this one hauls ASS!

Rusty

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Barometric Pressure Mod yields 10% HP/TQ gain
« Reply #5 on: February 03, 2005, 01:21:05 AM »
I don't remember the exact settings for when I first tried it.  I don't even think they are relevant.

The first time, I was looking for the wrong things and I was in a hurry...  I adjusted it, it got better, I kept adjusting it, and it got  worse, and because I had preconcieved notions I missed what really happened.  Plus, the Cartech was adjusted in a very non-optimal way, and the ECU was constantly fighting short-term fuel trim (block 099).

This time around, my base fueling was much better - no longer fighting the STFT's,  I was not in a hurry, I patiently adjusted and logged the right data, and found a jewel.
i]AEB Engines have better-flowing heads and a real throttle cable...[/i]

the_russian

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Barometric Pressure Mod yields 10% HP/TQ gain
« Reply #6 on: February 03, 2005, 07:30:21 AM »
Hey man that's crazy. I'll defenatly try it as soon as figure out what exactly this mod does and how it does...and when i get some time :? . Ok so like what does it do ...it make the ECU think that you're at the lower altitude which gives it more fuel which makes the engine with MBC happier...or am i not even in the ballpark.

Alex

ZenItRam

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Barometric Pressure Mod yields 10% HP/TQ gain
« Reply #7 on: February 03, 2005, 07:04:23 PM »
ah, the secret mod released!

tweakeDub

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Barometric Pressure Mod yields 10% HP/TQ gain
« Reply #8 on: February 04, 2005, 08:35:38 PM »
Just out of curiousity how come your running a 440 injector on stock turbo... ?
You cant ever get the full potential out of them can you?

Rusty

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Barometric Pressure Mod yields 10% HP/TQ gain
« Reply #9 on: February 05, 2005, 08:06:45 PM »
Quote from: "tweakeDub"
Just out of curiousity how come your running a 440 injector on stock turbo... ?
You cant ever get the full potential out of them can you?

No, I can't.  310's would be plenty of fuel for my setup.  But the AEB has a 16.32 msec injector duty cycle ceiling.  So to get enough fuel for the stock ECU's timing curve in less than 16.32 msec I have to have the 440's.  To keep the fuel trims happy, I have to run 2 bar base fuel pressure.  To keep WOT happy, I have to have 5 bar fuel pressure at 15 lbs boost.  The max pulsewidth I see at WOT is around 14.5 msec.

It's not optimal but I have learned a LOT trying to get it all to work...

I'll be introducing some fuel management (still stock ECU) soon, which will enable me to go bigger than 16.32 msec.  I expect to run 380's at 3bar with this setup.
i]AEB Engines have better-flowing heads and a real throttle cable...[/i]

jayryan

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Barometric Pressure Mod yields 10% HP/TQ gain
« Reply #10 on: February 15, 2005, 09:19:08 PM »
Just an FYI, here's the prices I got from Tynan's so you have a ballpark on the cost for this:

443-906-233 qty-1   $13.15
000-979-133 qty-3   $2.93ea.
443-906-247 qty-1   $4.48
000-979-129 qty-3   $3.00ea.

You still need knob of choice. And maybe an ECU when you blow yours up :lol:
'03 A4 1.8TQM
'68 MG C
'06 4Runner