boost dropping off

[Ed_RX7]

Any ideas!!!!  I\'ve got a Single Turbo and I seems to be experiencing my boost dropping off at around 5.5 rpm..........so I can\'t feel the true benefits of my large street port...anbody had similar symptoms and what was the cure...........pretty sure I have no leaks before the turbo........could it be the spring on my wastegate.....?...could it need adjusting?

Cheers

Ed

[bill shurvinton]

Sounds like your wastegate controller is hooked up backwards or not at all.

[Ed_RX7]

sorry bill never  heard of a wastegate controller......got a BOOST CONTROLLER....? :confused: and as far as I know it is connected correctly....got a profec spec 2....hi and low boost both work........boost just starts tailing off!!

[bill shurvinton]

Boost control is done by PWM modulation of the signal to the wastegate. If the controller is on the wrong port of the wastegate (if you have a 2 port wastegate) your boost will rise normally to the wastegate setting of (often) 7PSI, then the solenoid will start operating and reduce the boost.

5500 sounds late for full boost unless you have a massive turbo mind, so its unlikely, but short of having completely the wrong turbo for your porting the wastegate controller is the next most likely issue.

Bill

[maximtaylor]

Your profec is not set up right!

I can sort it, or explain in person if you plan on being at Pod next month

You are not the first, if that is any comfort!

Max

Originally posted by elnr_uk
sorry bill never  heard of a wastegate controller......got a BOOST CONTROLLER....? :confused: and as far as I know it is connected correctly....got a profec spec 2....hi and low boost both work........boost just starts tailing off!!

[Ed_RX7]

max you have pm mate

[maximtaylor]

Here\'s a better description of how to set up the unit - far more informative than the manual!

Definitions and things you need to know before you start:

SET This is how you set the boost pressure. Rather than setting it in psi or kPa, the Greddy unit allows you to adjust it as a percentage value, from 0% (greddy unit essentially turned off) to 100% (greddy unit will set the boost as high as it can). This setup demands a certain amount of trial-and-error to properly configure it since you have to make adjustments, then drive under WOT (Wide Open Throttle) and see what the maximum boost pressure achieved was throughout the entire RPM range. SET SHOULD BE SET TO A CONSERVATIVE VALUE WHEN BEGINNING TO TUNE YOUR GREDDY UNIT. 20% SEEMS TO BE A CONSERVATIVE SETTING BASED ON MY EXPERIENCE ON A SINGLE TURBO RX7 AND TAKING INTO CONSIDERATION THE LINK BETWEEN SET AND GAIN (see GAIN below).

GAIN is defined in the manual as the value to adjust the "boost consistency". You don\'t really need to know exactly what that means. You should set GAIN to 0 when beginning, and you will then test the car under WOT while paying attention to the boost pressure. If the boost goes up and then falls off at higher RPM, you will want to increase the GAIN by a conservative amount (5% should be relatively conservative to begin with, then when you want to fine-tune it, you can go down to intervals of 1%). When you increase the GAIN value, the corresponding boost that you will go up to will be higher even if you leave the SET value alone. GAIN SHOULD BE SET TO 0 WHEN BEGINNING TO TUNE YOUR GREDDY UNIT.

START BOOST (also known as SET GAIN because that is what is displayed on the unit when adjusting this setting) is the lowest boost that the Greddy unit will begin increasing the boost from under WOT. You want this to be as close to the SET value as possible, since you want to keep as close to your desired boost as possible. However, setting it too close to the SET value will cause the boost to spike. You should set this to a conservative setting when beginning to tune your Greddy unit. Then you can fine-tune it later to get it as close to the SET value as possible without causing the boost to spike. Fortunately, you can set this in psi or kPa, thankfully Greddy didn\'t decide to let this be adjustable in % like the SET value. START BOOST SHOULD BE SET TO YOUR DESIRED BOOST PRESSURE MINUS 4 PSI (about 28 kPa).

WARNING is the maximum boost that you do not want to exceed. Fortunately, you can also set this in psi or kPa like the START BOOST value. When the boost exceeds the WARNING level, it will kick in the LIMITER, which decreases the boost a certain amount that you can set. WARNING SHOULD BE SET TO YOUR DESIRED BOOST PRESSURE PLUS 1 PSI (about 7 kPa).

LIMITER is the boost percentage that the Greddy unit will lower by when the WARNING boost pressure is hit. LIMITER SHOULD BE SET TO AROUND 10%, which should give you about 7 PSI in the event of overboost.

PEAK is the peak boost value that the unit has seen since the last time it was cleared. To clear it, go to the peak boost display, and hold down the set knob until the unit beeps and "---" is displayed. IT IS A GOOD IDEA TO CLEAR THIS BEFORE YOU BEGIN JUST IN CASE YOUR UNIT HAS A HIGH BOOST ALREADY RECORDED.

LAST BOOST shows you the last boost that was recorded every time the accelerator is released for 3 seconds. TURN LAST BOOST ON BECAUSE IT IS A GOOD DIAGNOSTIC TOOL WHEN TUNING YOUR UNIT.

Keep in mind that when displaying in kPa, it does not show it technically in kPa, but rather misleadingly in bars, which Greddy inconveniently tries to justify by sticking x100 kPa next to the display. Therefore, 100 kPa will be displayed as 1.00 x100 kPa. Psi will also unfortunately be displayed in psi x10 so that 19 psi will show as 190, adding to the confusion.

Another very important thing to keep in mind is that when you first power on your car or the Greddy unit, WARNING will be set to 14.5 psi (100kPa, or 1 bar) until you interact with the Greddy unit by pressing any button. This "feature" is not documented in the manual.

The following steps should be taken in exactly this order, taking into consideration all of the previous information:
1. Change boost pressure units to psi if so desired (see manual).
2. Set WARNING to your desired boost pressure plus 1 psi (about 7 kPa) (see above).
3. Set START BOOST (SET GAIN) to your desired boost pressure minus 4 psi (about 28 kPa)(see above).
4. Clear PEAK boost value (see above).
5. Set LAST BOOST to ON (see above).
6. Set GAIN to 0 (see above).
7. Set SET to 20% (see above).
8. Set LIMITER to SET minus 4% (16% if you followed #7).
9. Test for boost falloff at high rpm. You should probably do this in a wide open area with no other cars nearby and preferably no cops. It is also good to have somebody in the car with you that can watch the gauge while you concentrate on not wrecking your car. If there is no boost falloff, then go to #10. If there is boost falloff, then increase the GAIN by 5% and test again. Keep in mind that when you increase the GAIN value, the corresponding boost that you will go up to will be higher even if you leave the SET value alone. Repeat until the boost pressure does not decrease, or until you feel surging. If you feel surging and the boost pressure still decreases (not sure if this is possible) then decrease to the last level that you did not feel surging at.
10. Increase SET by 2% and adjust LIMITER accordingly, then test again. Keep increasing by 2% until desired boost level is obtained.
11. Increase START BOOST (SET GAIN) by 1 increment and test until surging is felt or the WARNING level is hit and the display turns red, then decrease to the previous setting.

Once you have followed these steps, you will have roughly tuned your unit. To fine-tune it, repeat steps 9 and 10 except this time only increase or decrease by 1 increment.

[20B_boy]

Got that Ed?

[maximtaylor]

Ed, take note of this paragraph:

Keep in mind that when displaying in kPa, it does not show it technically in kPa, but rather misleadingly in bars, which Greddy inconveniently tries to justify by sticking x100 kPa next to the display. Therefore, 100 kPa will be displayed as 1.00 x100 kPa. Psi will also unfortunately be displayed in psi x10 so that 19 psi will show as 190, adding to the confusion.

I think we got the psi numbers wrong in our phone call.

Max

[Ed_RX7]

cheers Max!....lets hpoe this does the trick!!!.....will make interesting reading/playing!!!:rollin :confused:

[rx7veilside]

as max said the profec is a funny one
mine was doing same thing bost to 0.8-0.9 fine lower gears 4th and 5 boost 0.8-0.9 then seesaw between 0.7-0.9:(

[Ed_RX7]

rx7 veilside....how did you get yours sorted?

[rx7veilside]

asked max to play with it at trax..havnt driven much since then so may still need a final tweak.max knows this one inside out but lost me a couple of times and i was standing next to him when he did it..far as i could grasp get the boost to ur desired level first ie max boost u want to run  using just the big silver knob on the right and set it then tweak the other settings until no more fluctuation..if u want pm me and i will give u my settings and u can try it from there..paul

[briancarolina]

mine wide open throttle no boost car hesitates...only when i go easy and then hit it i get boost in every gear...but i cant go easy and then hit it in every gear while racing so i know i got a problem here help!!!!!!!