No boost control after 3" exhaust

[shackwrrr]

Tested diaphragm and it is fine. Took actuator completely off today and drove it, still went over 15 psi very easily. I just cant believe that back cut valves and very lightly cleaned ports is causing this. Even has an un touched 1 piece intake with the stock throttle body.

here are the ports

[cordes]

That's really crazy. I'm with Ken though. Time to open up the WG hole.

[85boostbox]

What kind of boost control?

[Rrider]

Also, when you lower exhaust back pressure there's less need for spark advance. Consider reducing spark - not for the boost but for your engine.

How many degrees does it usually take?

[shackwrrr]

just a line strait to the WGA, thats it.

[Tempted]

Older post, but figured I'd mention this. Opening up the exhaust will decrease the psi and increase the power at the same time. Its a win/win. Bigger exhaust = more flow, more flow = lower system pressure, lower system pressure = less stress on the entire engine.

Simple demonstration:

Take a drinking straw and tape a coffee stir straw to the end. Now blow on the drinking straw. Lots of resistance and the air pressure in the drinking straw is high(lets say 10 psi). Now remove the coffee straw and blow. Almost no resistance and the amount of air going through it is very high but the air pressure in the straw is very low(closer to 1psi). Less boost pressure, yes, but boost pressure does not make horsepower. The fact is the higher the boost pressure, the less efficient the system is. When you opened up your exhaust, you removed the coffee straw. Now your drinking straw(turbo exhaust out) can flow more volume with less restriction meaning less psi and a more efficient, free-er flowing and more powerful system.

Higher psi = higher intake air temp, higher load on the turbo and more stress on all of the parts under pressure.
Lower psi = less stress on everything and lower intake air temp.

[Tempted]

Some dude on Youtube is arguing with me about this. He says he hits 30psi with a stock TII turbo and wide open exhaust. Not a chance unless he has the world's worst intake tract and a super worn out cam with round lobes.

[GLHNSLHT2]

Didn't gary D hit 28psi on his stock T2 turbo on the daytona.

[shackwrrr]

I ended up kinda fixing this, only by adding the supporting mods to handle a boost higher than 15. Im running a steady and happy 18psi everyday.

[Tempted]

You can hit 30psi with a stock TII and stock exhaust by disconnecting the wastegate but once the exhaust is opened up the psi goes down while the cfm goes up. My stock TIII Garrett will hit about 30 with the full exhaust system but with the exhaust opened up it won't hit 20.

[Shadow]

Something def weird and wrong going on here. I have Never ported a W/G hole on Any of the T3 turbo's I've run on Any of the cars we've built including the mid 11 second full 3" mandrel exhaust (no mufflers) S/C with 46 trim stage 1 .63 A/R housing.

This also includes the 57 trim that I ran on the Charger up to 39psi boost. Actually, it Also includes the current Holset I'm running now! lol

I've only ever seen the mitts turbos boost creep with open exhaust.

One thing I will add though, all of the higher HP cars had the 3" mandrel S/V, so much better W/G flow.

[Force Fed Mopar]

If I unhook the wastegate can on my Lebaron it'll boost up pretty high. Full 3" exhaust w/ hi-flow cat and resonator, ported exhaust manifold, stock T3 w/ a ported turbine and wastegate hole, stock head, stock valves, stock cam, 2-piece intake. It'll hold 20psi on the MBC. Spikes will go way up there though, when my wga line was bad it was spiking 25psi easily.

[GLHNSLHT2]

going to the ATP piece and full 3" mandrel bent exhaust would cause my friends van to hit cutout by 4800 with the WG flapping in the breeze. Porting the WG hole a bit keeps it just under 14psi.

[The Pope]

Some dude on Youtube is arguing with me about this. He says he hits 30psi with a stock TII turbo and wide open exhaust. Not a chance unless he has the world's worst intake tract and a super worn out cam with round lobes.

Didn't gary D hit 28psi on his stock T2 turbo on the daytona.

He talked about that on his site and ran 3" exhaust. BUT it did have a poor trap speed for the boost and it did run a 1 piece intake, stock 89 T2 setup. Same car he added just a 52mm TB to and converted the stock core IC to water to air to test whether either help.

Other than back pressure at the stock type sv like Shadow mentioned, extra high drive pressure can also cause this. Leaking IC lines or a poor flowing intercooler. Most lose the IC line all together, so no boost. A leak though can cause spikes and boost creep though.

[Shadow]

The factory Mitts uses tuned exhaust (calculated BP) to achieve desired boost, the factory Garrett turbo's do Not. I found out through Garrett way back in the day that their turbos where designed to run Wide open (No exhaust) without creep issues.

I obviously had my doubts about this and so, put it to the test. Like I said, in all the years of running/ building these cars I have Never ported a W/G hole and Never had any trouble holding 5psi boost, stable.

Every boost creep issue I ever resolved on one of these Garrets had Nothing to do with the size of the hole. Was always something else, timing belt on wrong or skipped a tooth or two or three, faulty W/G actuator ect ect.

I came to the conclusion that Garrett seemed to be correct, and unless I was to run a well made aggressive cam and/or EQ length tube header to greatly promote exhaust flow, it would never be a problem.

Now I have heard of some castings that were cast with a smaller hole, don't know if that accounts for all the problems ppl have had ?(who hopefully knew what they were doing)

Of course this was a non molested/ported turbine housing as I never screwed with stuff like that, just went to a larger housing/wheel instead.

Reminds me of the BS debates lol Ppl who would say they removed the BS assembly and now their RVM shakes uncontrollably and the whole vehicle vibrates! You try to help and tell them Something Else is Wrong, but they just won't listen and you can't do anything to convince them otherwise

[Shadow]

If I unhook the wastegate can on my Lebaron it'll boost up pretty high. Full 3" exhaust w/ hi-flow cat and resonator, ported exhaust manifold, stock T3 w/ a ported turbine and wastegate hole, stock head, stock valves, stock cam, 2-piece intake. It'll hold 20psi on the MBC. Spikes will go way up there though, when my wga line was bad it was spiking 25psi easily.

When you say "unhook" do you mean unplug the boost sourse, or unhook it from the W/G flapper, cause I took the OP's post as "unhook it from the W/G flapper".

[Tempted]

Reminds me of the BS debates lol Ppl who would say they removed the BS assembly and now their RVM shakes uncontrollably and the whole vehicle vibrates! You try to help and tell them Something Else is Wrong, but they just won't listen and you can't do anything to convince them otherwise

This is the 1st TIII I've had that I didn't remove the BS. Never had any vibration issues. All my issues were trying to run 30psi with wide open exhaust, a giant FMIC, big turbo and no water/meth injection every single time I got behind the wheel. Worst vibration issues I've had are when the bobble strut breaks. That's happened 3 times.

[Force Fed Mopar]

When you say "unhook" do you mean unplug the boost sourse, or unhook it from the W/G flapper, cause I took the OP's post as "unhook it from the W/G flapper".

I meant disconnect the boost source.

[GLHNSLHT2]

On my friends minivan it's a 2.5 with a 2 piece intake, water/air i/c. T2 garrett with the ATP and 3" exhaust. Boost control was fine and low with the stock 89 T2 SV and stock exhaust. Threw the ATP and 3" on it and would hit cutout with the flapper flapping in the breeze.

[Shadow]

I meant disconnect the boost source.

That's what I thought you ment, but wanted to be sure. When you disconnect the boost source on the W/G actuator you are going to achieve max boost for that W/G can IF you stay in it. (also refered to as "running All of it) Only way you can hold more boost is with a dual port W/G can. (1 inlet on either side of the diaphram) This allows you to run a boost signal to the front port of the W/G can which acts like a stronger spring allowing for more boost (if the turbo is capable of it.

A properly set-up Big can should hold 28+psi depending on wether the turbine housing has been messed with. (35+ in an unmolested turbine housing) As the more you port and open up the W/G hole, the lower the max boost capability will become. This is why I never messed with the housings, I always wanted to know that I would have 35+psi boost capabilities. (on a stock TII turbo 28-30 is fine because the turbo has no efficiency above those levels)

This is also why I chose to run the Holset W/G can when Everyone else told me I would have 30psi Min boost and could never get it any lower. lol I knew it was a Strong can and also that it was adjustable, just needed to have someone give it a try!

Getting back to the topic at hand, I believe the OP ment that he removed the entire W/G actuator, so W/G flapping wide open and still boost creep to 15psi, def something Wrong there!