MAP sensor moved -- some results

[Sonnyballs]

DISCLAIMER: I am not an expert at this and I cannot guarantee that everything in this is 100% correct. I simply wish to share the results of what I've done and hopefully help someone out in the process.

As most of you know, the J&S Ultra Safeguard v.2 has a MAP limiter function which will limit the voltage on the MAP signal wire to prevent the ECU from throwing a CEL.

Moving the MAP sensor from the inlet side of the blower (on the throttle body) elminates two problems:

1) Tip-in detonation
2) Partial throttle drivability problems

Number 1 occurs because as the bypass valve closes and boost enters the system, the MAP sensor in its stock location momentarily still sees vacuum. While the manifold is under vacuum, the ECU operates in closed-loop operation and attempts to maintain a 14.7:1 air/fuel ratio. This is great for gas mileage and emissions, but it is too lean for boost. The result is momentary lean condition leading to a common problem with the JRSC, tip-in knock. Rafe Jaffey's TPS trick addresses this problem by way of TPS trickery. Moving the MAP is another way to do this.

Number 2 happens when there is boost in system at partial throttle. For example, I can drive the car in such a way that I have 3 psi of boost present with the gas pedal barely pressed down. The ECU still sees vacuum on the MAP sensor and stays in closed loop operation which again causes the engine to run lean.

Moving the MAP sensor forces the ECU out of closed-loop operation as soon as boost is present in the system.

Here is attempt #1. I used a brass tee to do this, but this method did not allow the use of the JR enrichment relay and I was a bit worried about the weight of the tee.



Here is attempt #2. Despite the look, the MAP sensor is actually pretty secure in this location and the use of a short piece of stiff hose allows for little movement. It's ugly, but it'll do until I make another bracket. I ended up redoing it because I wanted to be able to do some tests with and without the JR IAT relay.



As I stated earlier, tip in knock is completely gone now. Partial throttle problems are cured because the new placement of the MAP sensor allows the ECU to into open loop (WOT) operation as soon as boost is in the system.

Some feedback:

I drove around for about 2 days with the IAT relay unhooked (reconnected the IAT sensor wire back to the wiring harness).

I hooked it back up today and can honestly say that the car feels "snappier" at tip-in, but a little flatter at WOT. I think the 15k resistor in the IAT enrichment relay may be a bit too much.

Sonny

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Sonny Van Hook ([email protected])
2000 Supercharged Civic Si @ 6psi
1999 Tonykart/Honda 80cc Shifter

[Sonnyballs]

I just wanted to add that as Mark (B20C5 Turbo) stated, a/f at WOT can be tuned by using the MAP limiter function.

Before I enabled the MAP limiter, my 0 vacuum voltage was 2.874 volts (key on, engine off). This is the value that the MAP sensor will send the ECU at WOT. Increasing the voltage will result in richer a/f ratios and decreasing it will result in leaner a/f ratios. I have not seen how far I can go yet, but others have stated that you can go to around 3.00 volts before you trip the CEL.

To test it, I did a couple of rolling starts yesterday in 3rd gear from 3k to 8k. With the MAP limiter set to 2.874 volts (my "reference voltage"), a/f ranged from 0.85 to 0.89 volts (checked at O2 signal wire at ECU with my Fluke voltmeter) during the run. The higher voltage means richer a/f. I then adjusted the limiter circuit to 2.824 volts (-0.050 volts). Several more 3k to 8k passes yielded consistent a/f ratios between 0.82 and 0.86 volts during the run. Reducing the voltage did lean out the a/f. As you can see, small changes in voltage result in a pretty substantial change in a/f ratios.

0.87 volts corresponds to roughly 12:1 on the J&S a/f meter, but I wanted a precise number, so I used the voltmeter.

Sonny

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Sonny Van Hook ([email protected])
2000 Supercharged Civic Si @ 6psi
1999 Tonykart/Honda 80cc Shifter



[This message has been edited by Sonnyballs (edited May 08, 2001).]

[Holden]

Good data man!

Keep it coming. It looks like this could be a good tuning tool for those with the v2. Also maybe a poor man's AFC!

Greg

[austrian type-R]

Can I make this on my Supercharged ITR too?

One thingy is not clear for me? What is with the JR relay? Where do you plug it in stock?

Has yours a vacuum/boost line?!?! My relay has only 2 wires and one resistor

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98? ITR
supecharged @ 6psi
BTC unit, apexi V-AFC,
K&N ram air filter, skunk2 cam gears, ingalls camber kit

[Sonnyballs]

Austrian Type R: The JR relay/resistor consists of pressure activated switch (you can see it plugged into the back of the "tee" in the second pic) and the resistor box that sits inline with the IAT sensor wire. At 1 psi, it tricks the ECU into thinking it is very cold outside. This dumps more fuel and advances the timing. In some cases, this may hurt you, but it seems to really depend on the car.

More data

First, I wanted to figure out how the ECU reads the IAT sensor and what voltages corresponded to what temps. Remember that the Si's temp sensor is in the intake boot and not the intake manifold like most other engines. My testing showed this:

JR Relay enabled
4.60 volts = WOT (it seemed to always be 4.60 volts at WOT regardless of outside temp)

JR Relay disabled (removed resistor pack)
3.97 volts = tip wrapped in saran wrap, dipped in ice water (~40F)
2.70 volts = in the garage, before leaving for work (~75F)
2.50 volts = after 2 miles on the road to work, steady cruise
2.33 volts = under my tongue for 2 mins (don't try this at home, kids! ) (~98F)
1.61 volts = arrival at work in the morning, 8 mile trip, mostly highway cruising

1.87 volts = lunch time, car was sitting in the shade, but outside temp was ~95F
1.26 volts = after 10 mins of city driving during lunch break
1.12 volts = after 2 mins at a stoplight during lunch break
0.93 volts = right before I turned the key off after getting home for lunch break

The trend seemed to be that as I continued to drive, the air temp just kept climbing. I don't know what 0.93 volts corresponds to, but that is pretty dang hot!

I also did some more tests with a/f ratios at WOT by playing with the MAP limiter circuit on my Ultra v.2.

Baseline MAP voltage: 2.884 volts (set the day before during WOT runs without the JR relay)
A/F Ratio at that voltage with no relay: 0.82-0.86 volts (I'm guessing roughly 13:1 to 12.5:1)

First run using baseline map voltage (2.884) from day before with JR relay enabled: 0.93 to 0.96 volts

Installing the relay caused the a/f to jump over .1 volts! (much richer)

0.95 is full rich. I am pretty sure that that is roughly the max voltage that O2 sensor will report.

Map voltage set to 2.834 (-0.050 from baseline): 0.92 to 0.95 (small change)
Map voltage set to 2.234 (-0.150 from baseline): 0.91 to 0.93

During my last session (without the relay), dropping the voltage by 0.050 volts made roughly .04 difference in a/f ratio. Today, the difference in a 0.150 (three times) was only .03 difference. I am guessting that the car is running extremely rich with relay enabled.

From these tests, I can pretty easily conclude that the engine is running substantially richer (very rich initially) at WOT with the IAT relay enabled.

Seat of the pants tells me that the car feels a lot more drivable around town with the IAT relay enabled. So, it appears to be needed to maintain drivability, but it is causing the ECU to dump way too much fuel at WOT. (based on my tests as well as my 10 dyno runs)

If I can't get the a/f to more desirable number with the IAT relay enabled, I may try a smaller resistor (10k ohm instead of the 15k ohm that is in there). Or I may once again try removing it and compensating for it by adding fuel at WOT (via the MAP limiter) and increasing ignition timing (via the J&S BTM function)

Sonny

------------------
Sonny Van Hook ([email protected])
2000 Supercharged Civic Si @ 6psi
1999 Tonykart/Honda 80cc Shifter

[This message has been edited by Sonnyballs (edited May 09, 2001).]

[This message has been edited by Sonnyballs (edited May 09, 2001).]

[00ITR006]

sounds good, can you do this also with the TPS mod in place. I have no tip-in or anything.

[This message has been edited by 00ITR006 (edited May 09, 2001).]

[austrian type-R]

[QUOTE]Originally posted by Sonnyballs:
[B]Austrian Type R: The JR relay/resistor consists of pressure activated switch (you can see it plugged into the back of the "tee" in the second pic) and the resistor box that sits inline with the IAT sensor wire. At 1 psi, it tricks the ECU into thinking it is very cold outside.

WTF
Is it possible that I have no such an relay/resister? I have only a black little box which is inline with the IAT sensor wire!


------------------
98? ITR
supecharged @ 6psi
BTC unit, apexi V-AFC,
K&N ram air filter, skunk2 cam gears, ingalls camber kit

[Sonnyballs]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>
WTF
Is it possible that I have no such an relay/resister? I have only a black little box which is inline with the IAT sensor wire!
<HR></BLOCKQUOTE>

That is the resistor box that I am talking about, so it sounds like you do have one. The red/yellow wire from the wiring harness goes into the box, then another red/yellow from the box goes into the IAT sensor, right?

Sonny



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Sonny Van Hook ([email protected])
2000 Supercharged Civic Si @ 6psi
1999 Tonykart/Honda 80cc Shifter

[pest]

www.gadgetseller.com

Hey Sonny, check this out. I dont know if you know about this site and the products or not, but It might help you.

I hated tuning w/ the voltmeter due to the fact that "hook up," "unhook," hope you stay in place. Using this, I can display the volts for my a/f all the time.

Hope this can useful for you since you like to mess around w/ tuning a lot.

Pete

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NC area Honda/Acura List

[austrian type-R]

Sorry guys, I?m a dumbass!

Since the install is long ago, It seem I have forgotten it. OF COURSE I do have the black box with four wires. The black is pluged to the pressure switch. 2 to the IAC. and one into ground.

peace!