Originally Posted by 09CobaltSS1

Most of the bosch sensors have a bit of head room built into them, so even though they are rated for xxbar they can actually register a bit higher than that.

For example, the stock 2.5 bar. Technically they are only rated for just that, 2.5bar (250kpa or 21.7psi). However, as everyone is (or should be by now) aware, the 2.5 bar can actually register up to roughly 2.62bar (262kpa or 23.5psi) when monitoring the low res map.

The same thing holds true for the 3bar sensors. They are obviously rated as 3bar (300kpa or 29psi), however they should be able to register up to roughly 3.22bar (322kpa or 32psi) according to the sensor specs if scaled correctly.

As far as your RPD goes. That thing is absolutely useless for monitoring boost beyond 25psi and even up to that isn't always accurate. If you want an accurate boost monitor, get a mechanical gauge and ditch the rpd imo.

Originally Posted by silverbullet08

I have always been able to read up to about 32psi with the low res on hp. The problem is reading beyond that if there is a boost spike and being put into a limp mode. Your right on the borderline. The rpd does crazy things when it sees over 29psi also.I could build a file with the correct map sensor values but its a matter of testing it to see if there are other tables being scaled in the back ground like on the stg1 file. My guess is it will be fine since you can run the 3bar values on a stock file. If anything I could build the tune on a stg1 file with the 3.5bar values. Which would be the same difference as running 3bar on the stock 2.5 file.

Your car should be about ready up at the shop ryan. Now we need to get the extra injectors set up correctly to support that 30psi before you order new sensors. I would bet 30psi with the correct fueling is going to be pretty nasty on the street. Already is on 25psi.. Your really just starting to make that turbo work. At 30psi its really going to start moving some air.

Originally Posted by Matt M

That doesn't make sense. If you boost beyond the limit of your MAP sensor, why would the ECM switch to speed density? Speed density uses only MAP and does not use MAF.

On the LNF, it really doesn't matter if you go past the limit of your MAP sensor. On an LSJ, it is important to have accurate MAP readings because the injector flow varies significantly with a change in boost pressure. The ECM needs to know mass air flow and injector flow rate in order to deliver the correct amount of fuel. On the LNF, it is not as important because you have nearly 3000psi fuel pressure. Adding a few more psi to your boost does not significantly alter the injector flow rate. As long as you have an accurate MAF reading, your AFR will not change much because you raised the boost from 29 to 33.

FWIW, I have run up to 45psi boost several times on the dyno, running mostly E85 as well.(with GMS1 sensors) That's where you run into some real challenges based on running out of both fuel pumps, DI injectors, and 5th injector.

Originally Posted by 09CobaltSS1

Most of the bosch sensors have a bit of head room built into them, so even though they are rated for xxbar they can actually register a bit higher than that.

For example, the stock 2.5 bar. Technically they are only rated for just that, 2.5bar (250kpa or 21.7psi). However, as everyone is (or should be by now) aware, the 2.5 bar can actually register up to roughly 2.62bar (262kpa or 23.5psi) when monitoring the low res map.

The same thing holds true for the 3bar sensors. They are obviously rated as 3bar (300kpa or 29psi), however they should be able to register up to roughly 3.22bar (322kpa or 32psi) according to the sensor specs if scaled correctly.

As far as your RPD goes. That thing is absolutely useless for monitoring boost beyond 25psi and even up to that isn't always accurate. If you want an accurate boost monitor, get a mechanical gauge and ditch the rpd imo.

Originally Posted by Matt M

That doesn't make sense. If you boost beyond the limit of your MAP sensor, why would the ECM switch to speed density? Speed density uses only MAP and does not use MAF.

On the LNF, it really doesn't matter if you go past the limit of your MAP sensor. On an LSJ, it is important to have accurate MAP readings because the injector flow varies significantly with a change in boost pressure. The ECM needs to know mass air flow and injector flow rate in order to deliver the correct amount of fuel. On the LNF, it is not as important because you have nearly 3000psi fuel pressure. Adding a few more psi to your boost does not significantly alter the injector flow rate. As long as you have an accurate MAF reading, your AFR will not change much because you raised the boost from 29 to 33.

FWIW, I have run up to 45psi boost several times on the dyno, running mostly E85 as well.(with GMS1 sensors) That's where you run into some real challenges based on running out of both fuel pumps, DI injectors, and 5th injector.

Originally Posted by PsychoGenius

Is the math in this fucked up, or is it just me. For instance, 250kpa is ~36psi...

Originally Posted by silverbullet08

Subtract atmopheric from than and you got it. But like stated earlier the map sensors have a little wiggle room when you use this formula for calculation of the limit.

Originally Posted by cdnite

I think you are correct about the head room but over 20psi (+-2psi) on the 2.5bar and 26psi (+-2psi) on the 3bar my sensors don't alway match my logged boost gauge. Maybe it's the sensor for my boost gauge... But I thought GMTech and others on HPTForum noticed similar phenomena. They may read higher than rated but the last 80ish% are not accurate.

--Christian