THDP Porting
- Thread starter BarnesGN
- Start date
tminer
Not quite normal
- Joined
- May 25, 2001
When I did mine it didn't look like just drilling it was the ticket. I used a die grinder to enlarge the hole and blend in the backside. A dremel will work too. I definitely went in from the backside so taking it off was necessary. I also smoothed the inside of the housing while I was at it.
HTH,
Tom
HTH,
Tom
When I added my THDP I ported the wastegate hole, and I think I went a little too far.
I think I went out to about 1 1/4"...maybe a little smaller. I know there is right around an 1/8" of material for the puck and housing to seal.
Bad thing is I've had a hell of a time getting boost to stay consistent. It'll spool up great, and I have no problems in 1st or 2nd but once I hit third boost would drop like a rock.
I ran out of adjustment on the stock actuator so I added a HD unit.
Only way I've gotten rid of this problem is to have the HD unit really tight!
I think it's because I went too big on the wastegate hole...?
I think I went out to about 1 1/4"...maybe a little smaller. I know there is right around an 1/8" of material for the puck and housing to seal.
Bad thing is I've had a hell of a time getting boost to stay consistent. It'll spool up great, and I have no problems in 1st or 2nd but once I hit third boost would drop like a rock.
I ran out of adjustment on the stock actuator so I added a HD unit.
Only way I've gotten rid of this problem is to have the HD unit really tight!
I think it's because I went too big on the wastegate hole...?
QuickWrench
Don't Read This
- Joined
- Jan 28, 2002
It's likely a combination of that, and the alignment of the puck (when closed/closing). It's tough to get the downpipe to align just right with the wastegate hole in the turbine housing (trust me...). I can always move the pipe at least 1/8" in any direction with the fasteners loosely attached, so lining it up is key.
What I usually do to ensure proper alignment is lightly squeeze the downpipe in the bench vise [with soft jaws and towels] so that I can have the pipe staionary while I work on it. Then, I put a light coat of Copper Gold silicone on the face of the puck. Fasten the turbine housing to the downpipe with at least 2 of the allen-head capscrews (or bolts). Move the wastegate arm through its full range of motion, so it contacts the turbine housing. Remove the turbine housing, and take note of where the puck is making contact with the turbine housing, in relation to the wastegate hole.
It's best to do this before porting, since the silicone will indicate the optimal porting template. After porting and aligning [in slow steps], scribe small locating marks on the pipe flange and turbine housing to make sure you can line things back up once everything's back in the car.
Canadian SY/TY
New Member
- Joined
- Jun 15, 2001
I enlarged the Wastegate hole on my GT76 to 1.4". This was a big mistake.
By doing this I enlarged the hole by 60%
which brings the back pressure onthe wastegate puck from say 15psi to 24psi.
I have a 19-35 psi accustor and could only get 22 psi out of the turbo. 35psi -60%=21psi so close to the 60% diff.
I added external springs but this messes up the relationship of the size of the diaphram and the spring tension and would cause spikes and stuff.
I will be pulling the housing off and have it sleeved down to 7/8" as that is what the stock PTE housings come with.
Nolan
1992 Typhoon 10.95@123.9 at 4100lbs
By doing this I enlarged the hole by 60%
which brings the back pressure onthe wastegate puck from say 15psi to 24psi.
I have a 19-35 psi accustor and could only get 22 psi out of the turbo. 35psi -60%=21psi so close to the 60% diff.
I added external springs but this messes up the relationship of the size of the diaphram and the spring tension and would cause spikes and stuff.
I will be pulling the housing off and have it sleeved down to 7/8" as that is what the stock PTE housings come with.
Nolan
1992 Typhoon 10.95@123.9 at 4100lbs
twin 93 svt
Member
- Joined
- Jan 23, 2002
Take the ex. housing off, bolt it to the THDP, put the wifes lip stick on the puck, close the puck and you have your template. I then took a 1" flat washer to the center of my mark. marked the center with a permanent marker. I then removed the lipstick from housing and lined up the flat washer with the center mark, drew a circle with a marker and ported half way through the marker. Pretty simple may look like more in typed instruction, than the actual process. Good Luck!
Just a few notes, from my experience with the TA-49 and THDP...
At first, I tried to open up the wastegate hole to just over 1 inch. I think my first attempt was around 1.04". Even though I fully bell-mouthed the inside, that was still not big enough to prevent boost creep. I would also get a nasty boost spike (over 3psi) whenever I nailed the throttle.
On my second attempt, I used the lipstick trick (as somebody already suggested). I then removed the exhaust housing, marked the edge of the lipstick with a permanent marker, and started porting. I used a die grinder with a carbide cylindrical cutting bit. Worked really well, especially when I used cutting grease. I opened up the hole to 1-3/16", as I recall, which allowed over 1/16" sealing all the way around the puck. I also rounded all of the inside surfaces in the housing to as good a bellmouth shape as I could get. That was enough to stabilize my boost - no more boost spike, and no more boost creep.
Yes, I do have to tighten my wastegate rod tighter to get the same boost. I was able to partially compensate for that by increasing the wastegate DC% in my chip.
HINT: for those of you who are having problems with excessively tight wastegate rods, here's the ticket. Run dual wastegate solenoids. Do a search on this board for "dual solenoid", and you'll find some pictures and write-ups. On my car, plugging in the second solenoid gives me a 3-4psi increase in boost, with no changes to the wastegate rod.
EDIT: Here's a link.
Good Luck,
At first, I tried to open up the wastegate hole to just over 1 inch. I think my first attempt was around 1.04". Even though I fully bell-mouthed the inside, that was still not big enough to prevent boost creep. I would also get a nasty boost spike (over 3psi) whenever I nailed the throttle.
On my second attempt, I used the lipstick trick (as somebody already suggested). I then removed the exhaust housing, marked the edge of the lipstick with a permanent marker, and started porting. I used a die grinder with a carbide cylindrical cutting bit. Worked really well, especially when I used cutting grease. I opened up the hole to 1-3/16", as I recall, which allowed over 1/16" sealing all the way around the puck. I also rounded all of the inside surfaces in the housing to as good a bellmouth shape as I could get. That was enough to stabilize my boost - no more boost spike, and no more boost creep.
Yes, I do have to tighten my wastegate rod tighter to get the same boost. I was able to partially compensate for that by increasing the wastegate DC% in my chip.
HINT: for those of you who are having problems with excessively tight wastegate rods, here's the ticket. Run dual wastegate solenoids. Do a search on this board for "dual solenoid", and you'll find some pictures and write-ups. On my car, plugging in the second solenoid gives me a 3-4psi increase in boost, with no changes to the wastegate rod.
EDIT: Here's a link.
Good Luck,
John Craig
Tech Forum Advisor
- Joined
- Jul 9, 2003
May I add my two cents? When Terry first started building his
pipes we did a lot of experimenting, for him, with different hole
diameters. We found that every time we enlarged the hole over 1", we experienced boost control problems. In the end, we found
that holes .940-1.00" worked the best. We also found that the contour of the hole, on the inside, was the most critical to good
boost control.
pipes we did a lot of experimenting, for him, with different hole
diameters. We found that every time we enlarged the hole over 1", we experienced boost control problems. In the end, we found
that holes .940-1.00" worked the best. We also found that the contour of the hole, on the inside, was the most critical to good
boost control.
John,
I certainly would not argue with your experiments and expertise. However, I can only tell you my experience. At first, my TA-49 had the as-received wastegate hole diameter (about 0.78", as I recall). Boost creep was really, really bad. I then removed the exhaust housing, ported the hole to about 1.04", and radiused the inner corners as best I could. When I re-assembled and tested, I still had a significant creep problem. The boost would go up about 3psi through 3rd gear, and I would get a large boost spike (about 2-3psi) whenever I nailed the throttle.
A few weeks ago, I removed the housing, and I ported the hole to about 1-3/16". I again radiused the inner corners, to get the best bell mouth shape I could. I now have stable boost control (maybe ~0.5psi creep in 3rd), and the boost spike has been eliminated. The only "downside" is that I had to increase the wastegate DC% in my chip and tighten the wastegate rod a few turns to get the boost levels to where they were before I re-ported the hole.
Admittedly, I probably have one of the most aggressively spooling combo's there is: TA-49 with Precision 0.63 housing, THDP, ATR 2.5", and CAS V2. In other words, very little back pressure, and low intake tract pressure drop. That may be why I've had issues with boost control. I should mention that I never had any of these problems until I switched from the stock exhaust system to the ATR. I think the significant decrease in back pressure that I got with the ATR is what made my combo overly spoolable (if there is such a thing).
Just my $0.02...
I certainly would not argue with your experiments and expertise. However, I can only tell you my experience. At first, my TA-49 had the as-received wastegate hole diameter (about 0.78", as I recall). Boost creep was really, really bad. I then removed the exhaust housing, ported the hole to about 1.04", and radiused the inner corners as best I could. When I re-assembled and tested, I still had a significant creep problem. The boost would go up about 3psi through 3rd gear, and I would get a large boost spike (about 2-3psi) whenever I nailed the throttle.
A few weeks ago, I removed the housing, and I ported the hole to about 1-3/16". I again radiused the inner corners, to get the best bell mouth shape I could. I now have stable boost control (maybe ~0.5psi creep in 3rd), and the boost spike has been eliminated. The only "downside" is that I had to increase the wastegate DC% in my chip and tighten the wastegate rod a few turns to get the boost levels to where they were before I re-ported the hole.
Admittedly, I probably have one of the most aggressively spooling combo's there is: TA-49 with Precision 0.63 housing, THDP, ATR 2.5", and CAS V2. In other words, very little back pressure, and low intake tract pressure drop. That may be why I've had issues with boost control. I should mention that I never had any of these problems until I switched from the stock exhaust system to the ATR. I think the significant decrease in back pressure that I got with the ATR is what made my combo overly spoolable (if there is such a thing).
Just my $0.02...
