s4 na Rtek7 2.0: how does it handle boost?

[Unseen24-7]

I have reached my first UNEXPECTED problem in my na-to-turbo conversion and that is the boost/pressure sensor. I have a N327 boost sensor (if that matters), and I've been told that it only reads up to atmospheric pressure. Now does that mean that my ECU will crap its pants if I boost 10psi or [how] will it compensate?

This ad is not displayed to registered or logged-in members. Register your free account today and become a member on RX7Club.com!

[turbo2ltr]

You have to run Turbo ECU, MAF and MAP sensors.

[Unseen24-7]

What if I just replaced the Map sensor with a turbo map sensor...couldn't I tune out the difference with the Rtek?

From what I've read so far the na MAP outputs 5v @ atmo pressure, and the turbo one puts out ~2.3v at atmo pressure so I'm thinking it should be possible to just adjust the RPM vs MAP table on the Rtek and it should work.

[gxl90rx7]

Im not sure if you can enable boost- based timing on the n/a rtek, but i think it will be fine if you just use your n/a pressure sensor, as long as you set the 0psi timing value to what you would want at max boost. eg, just set 0psi timing to 20 degrees advance if running 10 psi, 15 degress if 15 psi, ect. I would be curious to see where the n/a afm maxes out, i think that would be more of a problem

[turbo2ltr]

I would not recommend running the turbo MAP sensor on an NA ECU.

[Unseen24-7]

Im not sure if you can enable boost- based timing on the n/a rtek, but i think it will be fine if you just use your n/a pressure sensor, as long as you set the 0psi timing value to what you would want at max boost. eg, just set 0psi timing to 20 degrees advance if running 10 psi, 15 degress if 15 psi, ect. I would be curious to see where the n/a afm maxes out, i think that would be more of a problem

doesn't the na MAF max out at like WOT anyway? how would that be different if its boosted?

[turbo2ltr]

If you use the NA MAP, then the ECU will not know you are in boost. So you will not be able (nor will it be able) to adjust timing as boost goes past zero PSI....BOOM. Have fun rebuilding.

If you use the turbo MAP, then the scaling is all off.

If you want to:
1: graph the pressure vs voltage function of the NA MAP sensor
2: graph the pressure vs voltage function of the turbo MAP sensor
3: Get the turbo timing tables into excel
4: compare the difference between the voltage output at different points of the graph and use that to shift/edit the turbo maps for use in the NA ECU.
i.e. if the turbo MAP puts out 3.5v at 5PSI, then you'll have to look up the timing value for 5 PSI on the turbo map, find the cell on the NA table that will relate to the voltage output of 3.5v, and insert the turbo timing value into the map.

Now repeat 797 more times.


Of course the turbo timing maps are LOAD based, so you can't directly equate them directly to a MAP sensor reading which even if you did the above, it would still be wrong.

So like I suggested...do like everyone else before you has done when they did their swap...get a turbo ECU, MAP and MAF. The car will run much better and your motor will thank you for it.

[Unseen24-7]

Okay I'm probably F'd but I got one more question...doesn't the na ECU primarily rely on the MAF for fuel calculations and not the MAP?

And if the MAP is used to advance the timing, once the MAP reads 0 it won't advance anymore, so if I set the timing advance @ 0 back to retard, it would hold that till max boost.

[Henrik]

All 2nd gen RX7 ECUs rely primarily on the MAF for fuel and timing. You can't mix and match ECU/MAP and MAF components without problems. Max rpm/boost is only one point in the maps, consider the other 797 as turbo2ltr has pointed out.

Use the turbo ECU, MAF and MAP. They can all be had for cheap these days. Others have gone this way for a reason.

-Henrik