38mm wastegate to small for 80mm
No, I don't have a setup for logging back pressure yet, but I'm working on it for spring.
Well, as far as after the turbo, I have a 3" down pipe to under the truck and a 4" Magnaflow Diesel catback with a 4" x 30" strait though Diesel muffler and dumps after the rear end. I have VERY little back pressure after the turbo. The Gate maintained both my low 6-7psi and high 15psi boost levels with both the MP T70 with .68 A/R turbine housing and the new mp T76 with .96 A/R turbine housing. That's just my experience with it...
Surely you understand the concept of a wastegate and how its surrounding settings have a very large impact on how it performs.
I could run around the internet and tell people that a 38mm gate would work on my PT88.....
but would those people who saw, and copied my setup, realize that I had a STOCK catback muffler? And that when I failed to mention that when I opened the 3" cutout in the mid pipe I picked up 4 psi, and that when I opened the 4" cutout on the down pipe itself, I picked up another 4 psi? Gee, now all of a sudden Im running 12 psi..... where did all of that boost come from? I didnt change turbos!!??
I run the BIGGEST gate I can physically fit. The days of blowing open gates really are not an issue with todays boost controllers and gate designs, but its up to YOU to figure out what YOU need. Sure, If your setup is poorly matched, you might have a severe back pressure issue, but that is where it goes beyond just bolting on parts.
I like to control boost So I run a big gate. If you need more boost, add a bigger spring Its much easier to swap springs, than swap gates.
I could run around the internet and tell people that a 38mm gate would work on my PT88.....
but would those people who saw, and copied my setup, realize that I had a STOCK catback muffler? And that when I failed to mention that when I opened the 3" cutout in the mid pipe I picked up 4 psi, and that when I opened the 4" cutout on the down pipe itself, I picked up another 4 psi? Gee, now all of a sudden Im running 12 psi..... where did all of that boost come from? I didnt change turbos!!??
I run the BIGGEST gate I can physically fit. The days of blowing open gates really are not an issue with todays boost controllers and gate designs, but its up to YOU to figure out what YOU need. Sure, If your setup is poorly matched, you might have a severe back pressure issue, but that is where it goes beyond just bolting on parts.
I like to control boost
So I run a big gate. If you need more boost, add a bigger spring Its much easier to swap springs, than swap gates. From the links in your sig, it looks like you are using a chineese FMIC. Have you measured pressure drop across the core?
My point is, your setup is an anamoly. I would never use a 38mm gate to try and control a 76mm turbo
My point is, your setup is an anamoly. I would never use a 38mm gate to try and control a 76mm turbo
Staging Lane
Joined: Sep 2008
Posts: 99
Likes: 0
From: MI
if he took the gate off, i can garantee you he'd make the exact same amount of boost - the gate is doing nothing because a) it's too small b) it's on a 90 degree angle c) half the engine isn't controled by a wastegate
Surely you understand the concept of a wastegate and how its surrounding settings have a very large impact on how it performs.
I could run around the internet and tell people that a 38mm gate would work on my PT88.....
but would those people who saw, and copied my setup, realize that I had a STOCK catback muffler? And that when I failed to mention that when I opened the 3" cutout in the mid pipe I picked up 4 psi, and that when I opened the 4" cutout on the down pipe itself, I picked up another 4 psi? Gee, now all of a sudden Im running 12 psi..... where did all of that boost come from? I didnt change turbos!!??
I run the BIGGEST gate I can physically fit. The days of blowing open gates really are not an issue with todays boost controllers and gate designs, but its up to YOU to figure out what YOU need. Sure, If your setup is poorly matched, you might have a severe back pressure issue, but that is where it goes beyond just bolting on parts.
I like to control boost So I run a big gate. If you need more boost, add a bigger spring Its much easier to swap springs, than swap gates.
I could run around the internet and tell people that a 38mm gate would work on my PT88.....
but would those people who saw, and copied my setup, realize that I had a STOCK catback muffler? And that when I failed to mention that when I opened the 3" cutout in the mid pipe I picked up 4 psi, and that when I opened the 4" cutout on the down pipe itself, I picked up another 4 psi? Gee, now all of a sudden Im running 12 psi..... where did all of that boost come from? I didnt change turbos!!??
I run the BIGGEST gate I can physically fit. The days of blowing open gates really are not an issue with todays boost controllers and gate designs, but its up to YOU to figure out what YOU need. Sure, If your setup is poorly matched, you might have a severe back pressure issue, but that is where it goes beyond just bolting on parts.
I like to control boost
So I run a big gate. If you need more boost, add a bigger spring Its much easier to swap springs, than swap gates.ohshixgoat - pm returned.
Sorry guys 
, don't listen to me. I'm just a dumb truck guy who doesn't know anything about turbos... I'll go back to my corner now and keep working on my own projects that probable won't work either...
, don't listen to me. I'm just a dumb truck guy who doesn't know anything about turbos... I'll go back to my corner now and keep working on my own projects that probable won't work either... Bringing it back. Can some one explain why on a 10psi spring in my tial 38mm I'm only getting 6psi on my comp 8079 billet wheel 1.32ar, 3.5dp. I was getting 8 last year with a tc78 and forged 347.
I have no idea it doesn't make sense. My 38mm turbosmart wastegate would hold my TC76 to around 6-7lbs. It would boost creep to 9-10lbs when it is cold out, than again my engine made 444 rwhp n/a before the turbo. I swapped to a precision 76GTS and the 38mm gate will not control boost at all, I've seen 15-16lbs in 3rd gear.
Have you checked to make sure your blow off valve is not opening or leaking?
Have you checked to make sure your blow off valve is not opening or leaking?
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I had a problem just like this with my jgs 50mm gate with a 76mm.. even though I had a "7psi" spring in there I could only make 2-3 psi. called and talked to the tech at jgs (very nice guy) he explained that psi ratings on most of the spring s dont mean jack.. every set-up is different and alot of times those ratings on the springs are only good in you have a small displacement motor. (sub 2.5l) he suggested a double spring set-up and shipped out 2 springs for me to try. I put one in and boost shot up to 10psi and blew the tires off.. 
then tried a double spring and without any changes to my boost controller,set-up, or tune I could make 6-7 on gate.
not sure if its the fix your looking for, but I had a mp76 q trim with a .96 ar 2.5" up pipes in a homemade set-up. the velocity my set-up was making was enough to push the wastegate open and limit boost..
then tried a double spring and without any changes to my boost controller,set-up, or tune I could make 6-7 on gate.
not sure if its the fix your looking for, but I had a mp76 q trim with a .96 ar 2.5" up pipes in a homemade set-up. the velocity my set-up was making was enough to push the wastegate open and limit boost..
What controller do you have? I would play with some different WG springs for sure. My Turbosmart WG is pretty accurate spring wise. I have done some testing using regulated air pressure from an air hose in my shop.
If I have 15 psi worth of springs in there it takes 15 psi from the air hose to open it. Now that doesn't take into effect any pressure coming from back pressure in the exhaust pushing at the same time.
I sure hope you get this thing up to potential soon as I am waiting to see the results of this comp turbo. I was thinking of getting one for my next build.
thats the same boost controller I was using.. great controller for a good price. I paid less then 20 bucks for 2 springs and shipping.. just becareful with the tials..
my buddy had a tattoo on his forehead after taking the last bolt out of the top..
my buddy had a tattoo on his forehead after taking the last bolt out of the top..
It did 675whp last year on the tc. Now it has 22 more cubes,a bigger cam and the comp 8079 billet wheel.
I don't know if 875whp is possible but that would be awesome. Its going to be around 18psi on 110 octane. Last years was on pump 93
I don't know if 875whp is possible but that would be awesome. Its going to be around 18psi on 110 octane. Last years was on pump 93
