Announcement

**Mihnea** · 27 December 2003, 10:11

Josh,

the VMAP uses a 500kPa pressure transducer and special circuitry to be able to put out a "normal" output signal.

The Bosch sensors (3 Bar especially) are starting to disappear or sell for incredibly high prices but so far I'm not worried as I still have reasonable supplies of 2 Bar units that can be recalibrated for perfect emulation of a 3 Bar's output curve.

The problem with the Motorolas MPX 4250 is that its output curve is 0.2~4.9v whereas a Bosch reads 0.1~4.8v, and the output voltage at idle is very likely to throw out fault codes like "pressure sensor, signal too high" and stuff like that.

So, the Motorola 250kPa sensor is definitely a no-no, plus 250 kPa Bosch sensors are still not so hard to find, new or used.

The VMAP isn't a bad idea, but just think of it this way: I sell you a chipset with a VMAP and you install the chips, no problem. A few months later, you start messin' with it because you want more boost (you've already got used to the HP/torque, which is usual) and, you set it to 4.0 Bar operation accidentally..... Now suppose for an RS2 setup boost is programmed at 2.7 Bar absolute (1.7 gauge) on a 3 Bar MAP operation, this means that on 4.0 Bar MAP operation you'll have 3.6 Bar absolute pressure or 2.6 Bar boost.

It's very easy: the turbo will break its shaft at 2.4 Bar and most likely, one of the rods will let go around ~2.3 Bar too.

HTH,

Mihnea

**Josh-stateside** · 27 December 2003, 13:52

See this is what I like:

I read.... wonder, think, and post.

and I get real honest answers.

So Cool!

Thanks
Josh

**Graham** · 28 December 2003, 02:00

I think its great aswell

, everybody is so helpful, my mate is a member of the E30 BMW site and on there there is arguments gallore, fights and alot of cloak and dagger stuff with reguards performance upgrades

. No one on there likes to share their knowledge and BTDT's, and most kick u when your down

. This site is obviously abit more mature and grown up

than the E30 site, hope it stays this way (and i think it will).
Graham

**layuca** · 6 February 2004, 03:27

Upgrades and pressure transducers

My CQ has a 3b motor, a K26 6412 and an RS2 exhaust manifold. No other upgrades so far. Though, I have been accumulating pieces for an upgrade. So far, I have the following items:

* mtm chip
* 3 bar pressure transducer
* harder wastegate spring
* 7A exhaust cam
* RS2 MAF

I am not into changing rods voluntarily or involuntarily, my goal is not to exceed 325 horses.

I have been reading posts on different forums regarding pressure transducers and the concensus seems to be that a 2.5 bar pressure transducer is sufficient for a 3b engine with stock rods.

My questions are:
1. I am not sure the basis of my mtm chip; I pressume that it's to be used with the stock turbo and fuel system. If this is correct, would the car run properly if I use the mtm chip with the 3 bar pressure transducer or should I install a 2.5 bar pressure transducer instead? Also, is there any way for me to tell what the requirements under the mtm chip, i.e., 2 bar transducer, etc... I was going to purchase a 2.5 bar pressure transducer until I read this post.

2. Considering the goal of 325 horses, of all the items that I listed above, which items would be recommended to be used? Please comment on appropriate fuel system changes as well. I have been thinking about a 7A pressure regulator without larger injectors, if I can get away with it. Otherwise, I'll get a set of 42 pound injectors.

Thanks for your comments,

Pedro

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