[OpenFlash]

Hi guys,
We've spent the last two weeks testing a few higher capacity MAP sensor options. A much needed option for single turbo applications. While the factory MAP sensor can read up to 21psi, it's good tuning practice to have at least 3psi of overhead (i.e., only run 18psi) since PID boost controls logic requires accurate error measurement to functional properly. And so the quest for the ideal upgraded MAP sensor began.

TEST 1: BMW N20 3.5 Bar MAP sensor


It was close to being plug-and-play (required an adapter harness or re-pinning of the terminals on the MAP sensor connector). And it worked as expected. Which is good as well as not so good.

The Good-- It provided a nice noise-free signal and offer what seemed to be perfect linearity from full vacuum to well over 30psi. It doesn't require an extra Procede input which means no additional wiring outside of physical installation.

The Bad-- Since the sensor mounts in the charge pipe (pre-Throtte body), it is subject to pressure spikes caused by throttle blade activity. It also doesn't account for the pressure loss induced by the throttle body/blade which can easily account for 1.0+psi at high boost applications.

Conclusion-- A good sensor for measuring charge pipe pressure. Not so great for measuring actual engine load since it reads pressure from the wrong side of the throttle blade. The DME had an internal model for calculating engine load based upon the pressure differential between the baro sensor (mounted post-throttle in the intake manifold) and the charge pipe pressure. However well it may calculate engine load at stock-like boost pressures, it does a pretty miserable job when running high boost. It also doesn't help that the pre-throttle baro sensor can only read up to 5-6psi of boost before flatlining. Which means that you can easily get an partial throttle scenario (where the throttle blade is partially open) where the baro sensor is maxed out AND the charge pipe pressure sensor is reading an artificially high pressure (due to partial throttle closure). Not really an issue when running stock-like boost pressures of 5-9psi, somewhat of an issue when running FBO levels of boost (15-17psi) and a real big issue when running big turbo boost (20+psi). Understandable given the fact that boost, fuel and ignition control are all essentially being referenced off of an inaccurate load signal.

TEST 2: GM 3bar MAP sensor


Unlike the N20 3.5bar MAP sensor, this unit can only read up to ~30psi. Those familiar with programming stand alone engine management systems back in the 90s are very familiar with this sensor. Also unlike the N20 sensor, this unit reads off of actual intake manifold pressure (post throttle body!) which means that it will read actual engine load and not be subject to throttle blade-induced misreadings/fluctuations. It installs by Tee-ing into a bypass valve signal hose and routing it to the nipple of the sensor. All the sensor needs is 5v and a ground which we tapped from the factory MAP sensor connector. The signal wire from the sensor goes to an unused analog input on the Procede harness.

The Good-- It reads actual engine load/pressure. It doesn't replace the factory MAP sensor which means that going back to a stock tune doesn't require a sensor swap.

The Bad-- It's noisy. Not surprising given how old the design is. The signal provided by the sensor is relatively choppy. Back in the 90s, we accepted this and tuned around it. But now, it's a bit out of place. Requires an unused Procede input channel.

Conclusion-- This option worked better than the N20 alternative given that it is reading pressure off of the manifold. But it's relatively dirty signal made datalogs look a little ugly. The nose was high-frequency enough that it really didn't seem to influence boost, timing and fuel control since the Procede employs an adjustable input signal filter for all load determination. But it wasn't the ideal sensor option.

TEST 3: AEM 3.5 Bar MAP sensor



The MAP sensor signal wire simply feeds right into Pin 7 on the Procede Rev3 harness's expansion port connector. When we designed the Rev3, we accounted for this needed input knowing that it wouldn't be too long before needed a high capacity MAP sensor:


Like the GM MAP sensor, this sensor reads pressure from the intake manifold. Which is great. It is also capable of reading up to 35psi of boost which is a bit higher than the GM sensor (and equal to the N20 sensor). Yes, we are just looking ahead But most importantly, the signal generated is beautifully smooth and noise-free as you can see from the logs below:

2nd->3rd-4th gear NLS run:


Zoom in on a 2nd->3rd gear pull (no NLS):


In the logs above, Boost (stock MAP sensor) and MAP2 (AEM 3.5bar MAP sensor) are plotted in the same graph. You can see them follow each other closely when the throttle blade is wide open. You can also see the AEM sensor reading 0.5-0.8psi lower due to the pressure loss across the throttle body. But more importantly, you can see that the AEM sensor is immune to the pressure spikes/jaggedness caused by throttle movement which is easily seen in the 2nd log at the begging and end of the 3rd gear pull.

Calibrating the Procede to accept this sensor was easy since the Procede allows for a secondary MAP sensor. The calibration data provided by AEM:


Setting up the sensor as MAP2 in the Procede software:


And then I redefining the 0% and 100% (0-255) load scaling (Y axis in procede tables) to now cover 1bar to 3.5bar absolute intend of 0-2.5bar absolute. This allows us to give up any mapping granularity for boost, timing and fuel mapping:


CONCLUSION:
Needless to say, we opted for the AEM add-on MAP sensor over the other options. It provides a cleaner signal than the GM MAP sensor and a far more accurate engine load signal than the N20 MAP sensor. Yes, it requires an extra analog input but we have already accounted for that. Which means better partial throttle boost control, more predictable throttle blade activity and just pain better drive-ability. It took quite a bit of testing to come to this conclusion. But for those looking to make max power with the least amount of compromises, we have your ticket

Cheers,
Shiv

[cupertinosteve]

Boom ... headshot! I'm lovin' it!

Can't wait to run it.

[jpsimon]

700whp! bring it!

[Former_Boosted_IS]

Shiv, have you tested the MAP sensor by pushing your car a little harder now?

[cupertinosteve]

Originally Posted by Former_Boosted_IS

Shiv, have you tested the MAP sensor by pushing your car a little harder now?

he'll be answering that ... shortly.

[OpenFlash]

Originally Posted by Former_Boosted_IS

Shiv, have you tested the MAP sensor by pushing your car a little harder now?

I'm tempted to push harder but I'm keeping it at 20-21psi for the time being. At least until after we get done with our magazine obligations. Once that is wrapped up, I'll be happy to target 700whp/25psi. But even at 630whp, the car is ridiculously fast/fun!

[lamia2super]

So when can we get this ? And see some results from your car

[Former_Boosted_IS]

Originally Posted by shiv@vishnu

I'm tempted to push harder but I'm keeping it at 20-21psi for the time being. At least until after we get done with our magazine obligations. Once that is wrapped up, I'll be happy to target 700whp/25psi. But even at 630whp, the car is ridiculously fast/fun!

630 rwhp on the street is nuts. I am with you on that. I am just curious how much power boost you can run on pump plus meth on this car with your PT62. I am shocked we can run so much boost with our compression. Clearly DI has some HUGE advantages.

[OpenFlash]

Originally Posted by lamia2super

So when can we get this ? And see some results from your car

We still want to do more testing before we start selling this upgrade. Expect to see it on all our in-house single turbo customer car conversions first before we start shipping them out.

As for results, there really isn't much more to do with it until we start bumping up the boost which won't happen until after magazine testing.

Originally Posted by Former_Boosted_IS

630 rwhp on the street is nuts. I am with you on that. I am just curious how much power boost you can run on pump plus meth on this car with your PT62. I am shocked we can run so much boost with our compression. Clearly DI has some HUGE advantages.

Yes, DI is huge benefit for such an application. I suspect 21-22psi/630-645whp is the comfortable limit for 93/94oct+meth. Anything higher is best left for race gas plus meth. It's really amazing what this engine is capable of.

Shiv

[marcvtec]

Whats that little breather filter connected to in your photo ?

[OpenFlash]

Originally Posted by marcvtec

Whats that little breather filter connected to in your photo ?

The Forge bypass valves. They are no longer plumbed back into the intake pipes since the intake pipes are gone

Shiv

[klipseracer]

would a flash tuner be able to re-write the algorithm for obtaining actual boost pressure with the N20?

[marv85]

Originally Posted by marcvtec

Whats that little breather filter connected to in your photo ?

I guess it's for dumping boost to atmosphere vs intake pipe.
I had to install one on one of my DVs to fit the helix intake

[OpenFlash]

Originally Posted by klipseracer

would a flash tuner be able to re-write the algorithm for obtaining actual boost pressure with the N20?

Anything is possible I suppose. But they would have better luck replacing the manifold-mounted 1.5bar baro sensor with a 3.5bar N20 sensor and re-writing DME code to compensate. They could leave the original charge pipe mounted 2.5bar MAP sensor alone. Probably a pretty big undertaking given the issues they are having with boost control and calculated torque limits.

[bmwe82]

AEM always had great stuff IMHO...are you running a catch can of any sort by the way since the rear pipe is removed, what did you do with the tube that people run their catch cans on?

[OpenFlash]

Originally Posted by bmwe82

AEM always had great stuff IMHO...are you running a catch can of any sort by the way since the rear pipe is removed, what did you do with the tube that people run their catch cans on?

No catch can. Not needed with this turbo since it doesn't blow oil like stock or upgraded twins. All we do is route the crank case breather to the intake filter.

[Syndicategt]

So when am I getting a ride in this mofo? I'm missing mine desperately. Are your DSS HS's on yet and when are you going to bump up the psi with this new TMAP sensor?

[Slidewayz]

we want dyno pron we want dyno pron we want dyno pron we want dyno pron we want dyno pron we want dyno pron we want dyno pron we want dyno pron we want dyno pron we want dyno pron we want dyno pron we want dyno pron we want dyno pron we want dyno pron we want dyno pron we want dyno pron we want dyno pron we want dyno pron

[OpenFlash]

Originally Posted by Slidewayz

we want dyno pron we want dyno pron we want dyno pron we want dyno pron we want dyno pron we want dyno pron we want dyno pron we want dyno pron we want dyno pron we want dyno pron we want dyno pron we want dyno pron we want dyno pron we want dyno pron we want dyno pron we want dyno pron we want dyno pron we want dyno pron

They have already been posted a while back.

[OpenFlash]

Originally Posted by Syndicategt

So when am I getting a ride in this mofo? I'm missing mine desperately. Are your DSS HS's on yet and when are you going to bump up the psi with this new TMAP sensor?

DSS axles are going on Wednesday. I don't plan to bump up boost beyond 21psi for another 2-3 weeks.

[onesuperboi]

Well, this is a surprise. Everyone was off to the races with the N20 sensor. Now, you flipped the switch to a seemingly better alternative.

[vasillalov]

I can see it coming: Procede rev 3.x! Get ready for the upgrade boys and girls.

Nice work on the research though. This AEM sensor seems very neat!