Well, thought I'd post this here rather than DIY PROM.

My current setup is an '86 Trans Am, equipped with a 1990 and above Speed Density ECU "7730". This is a TPIS setup with a Miniram, AFR 195cc heads, LT4 HotCam, true duals, etc, etc, etc.

I've been working with my Diacom Plus lately, and I've noticed something strange. When I display a graph of my runs (picture below), I notice that the MAP sensor Hg goes WAY UP on heavy throttle rather than down.

Now, correct me if I'm wrong, but shouldn't the vacuum go DOWN on heavy throttle rather than up??? I have the MAP vacuum hose hooked up correctly (manifold/plenum fitting rather than a "port" vacuum source on the throttle body).

Keep in mind that this is a Speed Density setup rather than a MAF setup. When i first got things running a couple years back, I would throw a SES code when I used a MAP sensor for a '90 Firebird, so I returned it and got one for a '93 bird instead. The newer one registered 5-volts continuing on down to 0-volts upon administering vacuum, and the older one that threw the code registered 0-volts climbing to 5-volts during the addition of vacuum.



Any ideas guys???

Thanks

------------------
86 Trans Am WS6 Black with tinted windows, shaved door handles
ZZ4, Mini-ram, true duals, LT4 HotCam, AFR 195 heads.
***Too many other mods to mention***

"In the future, cities will become deserts,
roads will become battlefields, and the hope of mankind
will appear as a stranger" The Road Warrior

 

Your Graph is absolutely fine. WOT = no vacuum = high pressure = greater MAP reading.

Tim

------------------
TRAXION's 1990 IROC-Z
Best Time = 12.244 @ 112.51mph (1.778 60' / 7.819@88.32mph in the 1/8)
All Natural. No Force. No Drugs. Stock Bottom End. Stock Body Panels.
Gunning for NA 11's with bigger cam, bigger stall, and bigger exhaust.
-=ICON Motorsports=-
Moderator: PROM board at thirdgen.org

 

Yes, MAP is Absolute Pressure, which is opposite of vacuum. If you are at sea level (30" hg) and just idling, you may have a vacuum reading of 19" hg, so your MAP would be 11" hg (Baro_Pressure@Your_elevation - Vaccum = MAP). Thus @ WOT, you MAP value will be close (never exactly though) to whatever the Baro Pressure of your elevation.

PS, for eprom burning, it is best to use Metric as all the MAP load tables use KPA instead of In. Hg. KPA is a little "finer" than In. Hg. due to no lack of a decimal point being displayed by most scan tools.

 

Thanks TRAX and Glenn. The help you guys give is awesome.

Steve

 

I want to know how you got a picture of the graph so you can post it!

------------------
West Coast GM Shootout 2001!
1991 Camaro Z28
5.7L 5-Speed (originally 305)
13.25 @ 107.18 MPH
Southern California
Member: SoCal 3rd Gen F-Bodies
Webmaster: SoCal F-Bodies
-=ICON Motorsports=-

 

Kevin....I'm sure you have Diacom Plus, so here is what you do.

1) Start up Diacom and trend a couple parameters in the "Graph" feature.

2) When you have the trends displayed, press the "Print Screen/SysRq" key on the upper right portion of your keyboard. That key will copy a screen shot of anything your computer screen is showing into your clipboard.

3) Now, go to "Paint" via your Programs to acessories menu and start it up.

4) Once you are in Paint, click on "edit" and then on "paste" and your screen shot will appear in the paint field.

5) Save it as a .JPG, and you're on your way to posting it on the message boards or whatever you want.

 

...But you have some "hiccups" between blocks 2270 and 2290 in first gear...wassup wif dat?

------------------
Later,
Vader
------------------
"What a Day..."
Adobe Acrobat Reader

 

That's probably traction problems Vader. I see the same thing on my graphs. Notice how the engine RPM also climbs and then goes down a little when traction is regained ?... Then if you look at the voltage of the TPS sensor.... it's flat in that area instead of rising which tells me he stopped pushing the throtle in an attempt to regain traction.

------------------
92 Z28 5.7
------------------
Trick Flow 23° heads, Comp Cams XR270HR-10 cam, Accel intake base + ported TPI,
TES headers, Flowmaster catback, MSD ignition, #24 SVO injectors, 1LE aluminum driveshaft.

Click here to see pics of my car.
Check out our car club Truspeed
Check out the Bin Archive for all your .bin needs

[This message has been edited by Synergy (edited April 18, 2001).]

 

Another reason for the Engine RPM increase decrease could be in between shifts. That happens when i'm giving it hell in my car.


Brendan

------------------
1987 IROC-Z L98,SuperRam,EB 6085's,LPE 219/219 Roller, Crane 1.6RR, EB TPI Base, 58mm TB, ADS 24#, AFPR, K&N, EB TES, Catco Cat, 3" Borla Cat-Back, Accel cap,rotor,distro/other crap, MSD 6AL, MSD Blaster 3, Aluminum DS, 94 Disk Rear, Adjustable Valve, Precision 3.73 Gears, Sub-Frame Connectors, Hotchkis Lower Control Arms, KYB Shocks/Struts, Suspension Techniques Lowering Springs, Polyurethan Bushings all over the place, Moog Upper/Lower Ball joints and Tie Rods ends/Idler Arm,

To see the ROC, Check out the webpage Here

 

Vader,

Synergy hit it on the head. I lost a bit o' traction, so I let off the throttle a slight bit.

Notice that the linearity of the TPS is non-existant. I was trying to keep traction, which wasn't an easy thing to do.

I should have posted a different run, where I maintain linearity across the board. That one above makes me look like a mere novice!

 

Synergy/Steve,

Thanks. I could see the shift points plainly, but didn't consider that the rear tires lost it and the driver compensated. That makes it clearer.

------------------
Later,
Vader
------------------
"What a Day..."
Adobe Acrobat Reader