jaymzs66

**Warning , as a preamble to not get angry responses, yes I've read the threads related, my question actually stems from some of them, the threads of interest were:

https://www.rx8club.com/series-i-engine-tuning-forum-63/how-tune-your-electronic-boost-controller-182461/
https://www.rx8club.com/series-i-engine-tuning-forum-63/map-rx-8-turbo-199538/
https://www.rx8club.com/series-i-major-horsepower-upgrades-93/horsepower-vs-boost-pressure-comparison-greddy-based-turbos-201475/page2/

**

...Now stupidly, I got the AEM tru boost ( I didn't know where to put the Greddy one. too bad i know it's better... lessen learned.) Though at least as a gauge the AEM is at least aesthetically pleasing ( all my others are AEM and they have a nice red theme that matches the interior red perfectly)

When I get down to tuning I asked the question on what to set the "Crack pressure" , Which for the Greddy people means I believe how long it holds the WG for the turbo to spool. I was told to take it slowly and observe. Here are the questions I have:

1- What can I log the boost curve with? Aside from setting my alarm at 8.5 psi, it's not like I can real-time take a note of the curve. I'm using the AccessPort for my engine tuning via MM tuning, from what I see though it's using MAF, which isn't that useful for turbo tuning correct? What observable values can I get from the Cobb to tune the turbo in terms of Duty Cycle and Crack pressure? Am I stuck needing essentially another EBC which allows logging?


2- Safe values: for a stock Greddy kit + BHR ingition + NGK plugs tuned via Cobb, what PSI should I not be exceeding? There seems to be a great deal of dispute on that. I set my alarm to 8.5 psi atm. My AFR has never gone over 11-11.1 under full load. What are good SAFE starting points for Crack Pressure and WGDC ( aside from the default 10)


3- Kinda fundamental question here, If say I would want say 6-7 psi as soon as possible, I would still not set the Crack Pressure that high right? I've read the wastegate design is poor on the Greddy kit, so as the rpm increases I could potentially reach a situation where the boost grows way too high? From the graphs I've seen I'd want near 8 psi but drop off after that ( I know this is related to turbo size, but is it also fortuitous since it with stock injectors etc, I couldn't handle much more anyway?

IronTanuki

I have a AEM TruBoost, and yes it is garbage as a EBC but nice as a gauge.

1. There is no way outside of a camcorder, passenger, or another device which logs pressure over time/RPM to log the boost pressure with the TruBoost. Crack pressure is the PSI at which the wastegate starts to open up. Turn the boost controller to off mode and note the PSI the engine holds from 5000-6000RPM then subtract 2PSI to start with. It is a matter of fine tuning it so that you don't get an initial spike. Note as the weather changes and gets more humid and hot vs colder and denser this value may need to be fine tuned to prevent laggy spool vs boost spikes.

Calculated load % and mass airflow are good indicators of power even if they are mostly relative to your own car. By logging these and tweaking the spring crack pressure slowly you can observe the areas down low where you pull more air.

2. I'd say start with the crack pressure at 3 to 4 and work from there. I'll let others chime in about safe levels to run on the GReddy turbo.

3. Correct, for 6-7PSI having the precise setting isn't a huge deal but you will notice a few hundred RPM difference probably if it is set too low and starts cycling while you are still building boost. Since the GReddy turbo is too small and the APV opens up at 6500 RPMish you should notice some pretty bad boost drop off towards redline. There is no way to correct this with the TruBoost since it is garbage and has no gain.

I just picked up a GReddy E-01 last week because the TruBoost does such a bad job at boost control. I found I have to either live with spikes to get any kind of decent power up top or be conservative and watch my boost fall from 11ish down to 8 at redline. With the E-01 not only will I be able to set duty cycle at 8 user defined RPM points but it also logs 3 hours of 3 inputs: PSI, RPM, and I am sending in the output from my AEM Wideband O2, which along with the Cobb gives you all the most vital data points.

jaymzs66

Wow thanks a lot, that's exactly what I was looking for. Hmm, disappointing about the TruBoost, but your setup sounds good, I may... just have to "borrow" that idea. Profec E-01 seems ideal, though i assume you just take out the screen for tuning or logging purposes, hiding it other times. The 3 hour logging that one does looks nice. Pricey, but .. eh... I prefer it to throwing darts at a dart board in the dark... so to speak.