Boost Taper Issue
Oct 18, 2015, 05:39 AM
#1
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Boost Taper Issue
Hey guys hoping some one can help me trouble shoot the issue ive been having for a while now trying to tune my car.
I am currently running:
Full-Race Efr 76/70 iwg .92 kit
Turbo smart WGA w 26psi spring
Test pipe
3" single exit
Wally 400 93 octane only
Id 1000's
Ams TMP cams
GSC beehive springs retainer combo
The issue is that after 6k rpm the car will drop from 27 psi down to 22 by redline 7900. This is on 0 wgd and spring pressure only. Even when my tuner is adjusting the wgd we cannot seem to hold 27 psi to redline it will still taper down to 24-25psi. I have done multiple boost leak tests and does not seem to have any leaks. Ive tried to play with the preload on the wga and doesn't seem to help. We initially had this problem when the cams got installed at that point I was using the BW high boost wga and we switched to the Turbo Smart one but it did not seem to help.
Any one have any ideas what this could be or have had any similar experiences that could chime in would be greatly appreciated. Ive been searching like crazy and was wondering if the BW bov could be leaking at higher boost pressures? Could the wga spring be too stiff? Could the 3-port be bad? The turbo only has like 4000 miles on it though.
Thanks!
I am currently running:
Full-Race Efr 76/70 iwg .92 kit
Turbo smart WGA w 26psi spring
Test pipe
3" single exit
Wally 400 93 octane only
Id 1000's
Ams TMP cams
GSC beehive springs retainer combo
The issue is that after 6k rpm the car will drop from 27 psi down to 22 by redline 7900. This is on 0 wgd and spring pressure only. Even when my tuner is adjusting the wgd we cannot seem to hold 27 psi to redline it will still taper down to 24-25psi. I have done multiple boost leak tests and does not seem to have any leaks. Ive tried to play with the preload on the wga and doesn't seem to help. We initially had this problem when the cams got installed at that point I was using the BW high boost wga and we switched to the Turbo Smart one but it did not seem to help.
Any one have any ideas what this could be or have had any similar experiences that could chime in would be greatly appreciated. Ive been searching like crazy and was wondering if the BW bov could be leaking at higher boost pressures? Could the wga spring be too stiff? Could the 3-port be bad? The turbo only has like 4000 miles on it though.
Thanks!
Nov 26, 2015, 07:08 PM
#4
Evolved Member
Step 1. Full leak down test at that pressure +5psi.
Step 2. Connect a pressure source to actuator for IWG and slowly raise pressure (I use compressor with adjustable output pressure control, but you can use a high pressure hand pump if you have one). It should move a bit at 13psi and move the actuator full stroke at 26psi, NOT LESS.
Step 3. Check your tune. If you are BELOW your load target when your boost is falling off then your should see the FineWGDC increase to the maximum allowed upward boost correction. In other words: is the ECU TRYING to reach the load target by raising boost, or is it programmed/tuned to only downward correct? You need to check if the tune for the WGDC is close enough that with upwards correction it can reach that load target. I tune such that the ECU NEEDS to add 10% upward correction to reach the target load. I live in NY where the summers can be 100degF outside and last winter the lowest I read on the car was -8degF. To prevent boost spikes when I jam on the gas I want the ECU to start 10% low and have to add UPWARD to reach the target. Come to think of it, you might want to make this step #0 above.
Oh lastly- the pressure on the IWG flapper area may be too much and it is simply over powering the spring. You would have to change your wastegate setup. Perhaps a new actuator. Unsure about an easy way to solve that.
~Jaraxle
Step 2. Connect a pressure source to actuator for IWG and slowly raise pressure (I use compressor with adjustable output pressure control, but you can use a high pressure hand pump if you have one). It should move a bit at 13psi and move the actuator full stroke at 26psi, NOT LESS.
Step 3. Check your tune. If you are BELOW your load target when your boost is falling off then your should see the FineWGDC increase to the maximum allowed upward boost correction. In other words: is the ECU TRYING to reach the load target by raising boost, or is it programmed/tuned to only downward correct? You need to check if the tune for the WGDC is close enough that with upwards correction it can reach that load target. I tune such that the ECU NEEDS to add 10% upward correction to reach the target load. I live in NY where the summers can be 100degF outside and last winter the lowest I read on the car was -8degF. To prevent boost spikes when I jam on the gas I want the ECU to start 10% low and have to add UPWARD to reach the target. Come to think of it, you might want to make this step #0 above.
Oh lastly- the pressure on the IWG flapper area may be too much and it is simply over powering the spring. You would have to change your wastegate setup. Perhaps a new actuator. Unsure about an easy way to solve that.
~Jaraxle
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