Map clamp voltage on VNT

[ShadowFromHell]

Any idea where to set the map clamp voltage on a VNT CSX? It no longer has a VNT, running a T2 turbo. AFRs were low 11s at 20psi, now they are low 13s! Does it need set at 4.7 like a MP cal? I set it at 4.3. VNT knowledge is limited it seems so ill probably end up finding the number by trial and error. It's just so hot right now I've got a limited window when its cool enough to test it but light enough to work on it.

Thanks!

[ShadowFromHell]

Since no one seemed to know I go thinking about it and I had a appfinity! I pulled up the cal in DCAL to see what the overboost limit is! It seems to be set to 17.18psi, is that correct? To make sure it was correct I pulled up a T2 cal and it was set to 14.3. So obviously I need to run the clamp much higher to get my fuel back. Any idea where 17psi relates to a 2bar map voltage? From what I understand that would be way out of its range, I thought they only read to 14.7? Again I may have to just play with it, I think I am in uncharted territory here with a 89 vnt car, they didnt build that many lol. But getting it to hit OB is a pain, as its on a 13 second timer, the only way it ever overboosts is long freeway on ramps where I hold the car in 4th, in boost timing my merge into traffic. Running it through the gears it never hits OB.

This does explain how FFV injectors were supporting a T2 turbo, FMIC, open 3"dp while on 20psi!

[ShadowFromHell]

Found this chart, not sure how accurate it is but its better then nothing.

http://injector-rehab.com/shop/mapsensor.html

Looking at it I assume I need to add 14.7 (1bar) to the 17.18 to figure out the voltage. Works out to 31.88 which should be out of range... Maybe I should clamp it right at 5v and see what happens? Its just such a pain to test, Im currently setting the car up for a boost leak test then getting the pressure to 16-17psi and then setting the clamp with a DVOM.

EDIT: I know no one messes with map clamps anymore, but its how I know how to "tune" these cars and its always worked well for me. Just not ready to make the jump to tuning with a laptop yet.

[cordes]

A proper cal from www.boostbutton.com sounds way cheaper than a motor. Since you're trying to cap the voltage before cutout I would just do it very close to 5v if you choose to go that route. Dip it down until you don't hit cutout anymore so you get as close to full map value as possible. I think Rob only charges about $30 for just the chip? That's pretty darn cheap.

[Fox]

yea just get a boostbuton cal done and disable overboost and have it set for 3bar map, i have a t2 turbo with a boostbutton cal in my 89 csx and its just perfect, before with he stock cal and vnt it would hit fuel cut all the time and really wasn't too drivable, now you can actually drive it and not worry about exceeding 14.5 psi

[ShadowFromHell]

That's the plan. But I really don't want to mod the stock ECU, I want to keep it as a just in case. So I need to come up with a core. I've got everything else. I know map clamps are old school but you can't deny they work and with a wideband it's ten times safer then it use to be.

At least I'm not using a mechanical overboost eliminator, extra injectors, and a narrowband lol.

[contraption22]

Map Clamps.... flashback to the 1990's