Overboost eliminator confusion

[Bossman429]

So now that it is getting colder out my GTS is hitting the overboost cut out. Rather than turning the Grainger down, I decided to just get rid of the overboost all together. I have an A/F gauge to monitor O2/fuel.

So, I've seen two "overboost eliminators" around.
I actually ordered an adjustable zener diode from M&M Racing here:
http://www.mm-racing.com/zener.htm
I know how this works, it just limits the amount of voltage that the map sends the ECM.
THen I also see the modified g-valve on TU:
http://********************/shop/prod...products_id=64

So are these just 2 different methods of achieving the same goal of limiting the amout of boost that the MAP thinks it sees? One just seems to limit the vac signal, whereas the other limits the voltage signal. Correct?

________________
-David
89 Lebaron GTS TII/A555
90 Grand Prix Turbo STE
91 Beretta GT

[iTurbo]

Yes, you could think of them as a limiter. The electronic one limits MAP voltage seen by the computer while the G-valve limits pressure seen by the sensor. Theoretically it accomplishes the same thing. I would use the electronic one because it won't be affected by ambient or underhood temps, and is much more precise and reliable. Set it and forget it.

I use the MM Racing electronic overboost eliminator on both my Omni GLH Turbo and Shelby Lancer. They've always worked great. I have the MAP voltage set about .05 volts below overboost, which occured at about 4.2v on both my SL and GLH. The SL uses a stock TII logic module while the GLH has an '89 2.5L TI SMEC from a Caravan.

[Bossman429]

Thanks iTurbo!
I was sure they did the same thing, but wanted to confirm with someone to feel confident I bought the right thing.
I bought the adj zener because I found in another thread that you said you run one in your cars. I figured following the guy who knows is the way to go!

[iTurbo]

I didn't even realize it was you until after I replied! I was trying to get Josh to install one on the GTS, but it really needs a BOV first. When it was on the dyno, it was off-the-scale rich as soon as it spooled up. I would think the fuel system would be OK up to ~16 psi, but I would not go any higher than that with those injectors.

Dialing in the overboost eliminator is a two person job. When I install them on my cars, I run long extension wires from the MAP sensor to inside the car so that MAP voltage can be monitored while driving. I drive while Josh monitors the MAP voltage. The MBC (grainger) must be adjusted so that it will just barely hit overboost in the 4th gear. If the boost is set too high, it will hit overboost before you can zero in on what the MAP voltage is. After hitting overboost a few times, it should be easy to tell at what voltage overboost is occuring. On my cars, it seems to be around 4.2v, but your mileage may vary. Next, splice the overboost eliminator onto the long MAP extension wires. Go for another drive and have slowly turn the overboost eliminator down so that the maximum MAP voltage goes down until it is just below the overboost voltage threshold, say 4.15v.

I housed the overboost eliminator circuit in an old gutted keyless entry module from a GM W-body and stick it to the inside of my glove box with a piece of sticky back velcro. After the overboost eliminator circuit is dialed in, you shouldn't have to adjust it ever again, but you might want to check that it's functioning properly every so often just to be sure.

[Bossman429]

Yeah, I'm selling stuff on Ebay right now to fund my RFL BOV for the GTS campaign. I will probably just get a K&N cone filter for now, and put it on the end of the intake pipe, then put the BOV in place of the air box up top. Probably not the best setup, but will work for now.
I have my eye on a single side intercooler on Ebay for ~$200 that is similar to the Spearco unit in shape at least. I was considering an NPR intercooler, but I'd rather get a same side in/out intercooler for piping ease, and so I can add the Spearco unit later when my needs/budget increase.

I was going to PM you about injectors... I think Josh said you have +20s on your cars, why didn't you go with the +40s? I'm probably going to go +20s on the GTS once I get an AFPR. I have read that cars with the 3 bar and +40s seem to run poorly when cold. I was just curious why you went +20s over the +40s.
Still learning about this whole new world.