Map Sensor

[Bbneon95]

DDG- Map sensor trickery

has anyone done this? Will I be able to use something like this safely. The Diode thing of course. Where it is soldered. I just wanted some input.

Thanks guys!

Keven

[detobias]

yes I am running a 4.7v zener ; website you cited shows where to solder it

I was able to insert the diode leads into the backside of the MAP plug such that it made connection there, so no soldering was necessary

be careful - the factory put an overboost shutdown feature into the computers for a reason; the MAP trick disables this, so watch your A/F carefully

and make sure you get a 1W zener ; originally I had either a 1/2W or 1/4 and it made the A/F act weird...

[87turbodance]

Don't forget to ad fuel when going over 15psi - a wideband would be a very good idea at this point! Of course so would a new cal with the cutout raised so you don't need to use a Zener diode. If on a budget MegaSquirt® EFI by Bowling and Grippo might be a good thing to look at.

[UnaClocker]

There are soooo much better ways to do that nowadays. That was written back before people were recalibrating their ECM's. Nowadays, you can just get a 3bar calibration, 3bar map sensor, some bigger injectors and a better fuel pump, and poof, you can go as high as your turbo will let you go, pretty safely. That diode simply tells the computer that you never went over a certain amount, say 14psi. So the computer stops pulling back timing as the boost continues to ramp up, and stops adding fuel to match the amount of boost you are running. It's very dangerous.

[xrattiracer]

actually with the diode it clamps it closer to 10 psi, which is even worse.

[UnaClocker]

5volts divided by 30psi (14.7 is ambient, and it'll read up to 14.7 boost) is .16667volts per psi. 4.7v divided by .16667, -14.7psi shows that the sensor will see about 13.7psi of boost with the zener diode clampin it at 4.7v. Still a bad thing, but unless you're using like a 3.9v zener, your computer should see more than 10psi of boost.

[detobias]

Quote:

Originally Posted by UnaClocker There are soooo much better ways to do that nowadays. That was written back before people were recalibrating their ECM's. Nowadays, you can just get a 3bar calibration, 3bar map sensor, some bigger injectors and a better fuel pump, and poof, you can go as high as your turbo will let you go, pretty safely. snip

Una- you are absolutely right. There are better ways to modify our electronics which are more sophisticated and intelligient; however, they are also more complicated (hardware wise) and expensive.

and, there are still the 'old-school' ways, they still work too, but require more "user" knowledge and 'input' to be used properly (safely)

If you have the money to buy a 3-Bar cal ($125), a 3-Bar MAP ($60), some +20s ($150), and a 190 Lph ($105) - then by all means do it ; you would then have a "plug-n-play", safe, and smart >15psi set-up ...

[all prices from fwdperformance ; of course, used may be cheaper]

I don't have that money ; my TII omni runs a mystery fuel pump, used +20s, a self-socketed 87 LM with a $20 cal from <M>, and a 4.7 zener'd 2-bar MAP... 12-13 psi ; traction limited 13.8s

the MAIN reason I added a Zener to my set-up was to eliminate 'overboost shutdown's which were occurring occasionally... boost spikes.. my Grainger'd 13 psi isn't exactly rock solid, and would sometimes transient up & down and trigger shutdown... very annoying during a run..

my cal was SUPPOSED to have the overboost shutdown disabled, but didn't

Una - you doing cals ? I am planning to upgrade to SMEC and will need a cal .. or 3 .. and <M> isn't delivering ...

[UnaClocker]

I still have the equipment to do the cals, I don't have any blank chips left, pretty much sold them all off. My UV light is nearly dead, I accidentally left it on overnight a couple times, need to order a new toothbrush holder.. hahaha.. But I could order a couple chips, I need to order an 87c257 for the SBEC in my new van (got myself a '90 turbo Voyager Tuesday). Shoot me a PM when you're ready, and I'll see what I can do.
Have you asked Rob? Most of the time I'm just burning one of his publicly available cals for someone, and I hate to do that since it's his amazing work and I feel like I'm taking business from him that he totally deserves for doing all that hard work in the first place.

[Bbneon95]

Ok im confused. Am I not suppsed to do this?

[UnaClocker]

It's a hack. It's not proper. I wouldn't do it if you don't understand it.

[Bbneon95]

it seemed easy, and figured it would be an easy way to up boost. I will take the long hard money road I suppose. Thanks!