Thursday, August 30, 2007

An interesting Q&A

Taken off the SG Evo Club Forum:

cavallino wrote:
guys, what's the difference between:
1. slapping a HUGE turbo onto a stock engine
2. stroking up the engine to 2.4L and using a stock turbo.

Response by a senior member with a very good understanding of tuning principles:

Area under the curve.

You NEVER look at just peak figures. You want to know what's the percentage of peak torque available throughout the rev range.

A small turbo with large engine will give you peak boost from a lower rev and sustain that through a pretty large rev range. Think GTR 2008 or 997 Turbo engine for instance. Peak torque from <2000rpm style="font-weight: bold;">heating and reliability

both have shares of issue in terms of reliability. Basically once you modify, be prepared to reduce yr service interval periods

Depending on who builds yr stroked up engine, you may have reliability issues.

Big turbos will need a lot more upgrades to cooling as well.

torque curve (one is better at low end and the other at higher end?)
See earlier paragraph

fuel consumption
As usual it depends on how you drive. If you need to hit the high torque range all the time, the stroked up engine is probably better since you get it at lower revs. If you are a more disciplined driver, and can drive the car offboost, the larger turbo is better for FC.

As usual, I find it silly to discuss FC when you are concerned with power.

pick up, response, lag
Torque under the curve. Bigger engine better

Depends on whether you put stuff like external wastegates, BOVs etc

Monday, August 13, 2007

HOW-TO : Tuning the GReddy Profec B Spec-II electronic boost controller

Many Team Fruity members know that we recommend the GReddy Profec B Spec-II electronic boost controller because it is not only good value for money, but also holds and controls boost well. However, most people have no idea how to tune this boost controller, and the user guides are usually in Japanese. We were fortunate enough to have come across this article in the EvolutionM forums and we found this to be accurate and useful information for Evo owners running this boost controller.

Tuning the Profec B spec II

I was looking around online and found that there are still questions about dialing in the Greddy Profec B spec II even with the great write up we already have on this website. So I thought I would post up my findings in how I understand things in an effort to make things a bit simpler for those that still have questions or want a quick reference guide.

Here is a basic chart type setup to aid in figuring things out
(I personally chose to use PSI instead of KPa.)


Set -- % -- “Desired boost psi”
(Use to set general boost level)

Gain -- % -- “Boost consistency”
(Use to minimize boost taper—proportionately affects the overall boost level)

Set Gain -- psi -- “Boost response”
(Controls when the wastegate starts to open–use to maximize turbo spool up)

Warning -- psi -- “Maximum boost level”
(Sets the maximum boost that you do not want to exceed)

Limiter -- % -- “Maximum boost modifier”
(Sets the amount to reduce the boost psi if warning level has been reached)

Peak Boost -- psi -- "Highest boost achieved"


Initial setup: (I was looking for 22 psi)

Set 30% (this should put you at roughly 12-15 psi of boost)
Gain 5 % (this is the lowest setting available)
Set Gain 18 psi (desired amount minus around 4 psi)
Warning 23 psi (I was already running 23 psi w/ ECU control)
Limiter 1% (there’s really no reason to do more than this—the car can easily handle 23 psi with a stock turbo)
  1. Turn off the unit to set it to PSI, then turn the unit back on and turn PEAK BOOST to "on".
  2. Set the WARNING to one above desired boost, and the LIMITER to 1% (or whatever you want).
  3. Start to increase the GAIN first to minimize or remove the taper. In most cases you will not be able to completely eliminate the taper. Increase gain in small increments until boost is held pretty much to redline. If boost spike/surge occurs – go back down in value until it subsides (at this point you’re done with the GAIN).
  4. Adjust for the SET value next—simply by adjusting the percentage until you reach your desired boost levels. In my case that was 22 psi.
  5. Set the SET GAIN value last—the reason for this is because you want to get it as close to the SET value as possible to maximize spool up. Once you hit a boost spike or surge—lower it down till it subsides.