Wastegates: internal vs external

[technician163]

I'm new to the turbo world and just recently picked up a 1991 turbo talon awd 5 speed for $250. I am a skilled and experianced mechanic in the south central region of PA. We don't see many, if any turbo cars, so this is releatively new to me. My question is: is there much of a difference between the internal and the external mounted wastegates??

 

[Mr Peepers]

Im trying to run a evo III 16g turbo, evo 3 o2 housing, and an evo 3 manifold....so pretty much im stuck with an internal wastegate but i think i can upgrade to a 34mm or 38mm i forgot which 1 but will that be good?

If you mean upgrade the flapper to 34mm, I don't recommend it. If you plan on running higher boost later it may become a problem.

Here, this is one option but it also outlines other options for internal wastegates regarding creep:http://www.dsmtuners.com/forums/art...boost-creep-modified-wga-peepers-mod-how.html

I don't like to link to my own stuff but it may make some things clearer.

If you are going to put an evo3 or any other 16g on and are worried about creep, port it for boost creep first.

Oh, and I'm going to recommend 12 ga. Just because it's a bi*** to solder 10 ga, and the wire inevitably goes to ~14-16 ga anyway at the connector.

 

[GSX4BangR]

I read your link and im pretty much going to port the turbo, o2 housing and manifold but neither of them is flanged for an external wastegate, what would i do in that situation casue i wanna get rid of as much boost creep as i can. I try to keep my car's engine as stock looking as i can.

 

[Mr Peepers]

Port the turbo for creep and keep the internal.

 

[GSX4BangR]

Okay just makin sure, i never ran on an internal wastegate for a long time, my 91 talon tsi awd i ran an external on it and my other dsm's i pretty much ran an external on them so im just trying something new like making an 11 second car out of a 16g.

 

[Mr Peepers]

Boost creep would be the last thing on my mind for a car aiming for 11's. You will likely have problems with the flapper blowing open and boost dropping off to low 20's by redline. I'll give you some ideas once/if you get to that point.

 

[GSX4BangR]

Alright thanks, when i buy the turbo i'll get back to you.

 

[DSMunknown]

If you are going to put an evo3 or any other 16g on and are worried about creep, port it for boost creep first.

Matt, other than being cheaper and easier to do, why would you recommend porting instead of jumping right to your MWGA strategy initially (and skipping the port job entirely (or at least for the time being))?

 

[delta448]

the car is completely stock and has 93,000 miles on it

That being so, I would like to replace the exhaust from the turbo back with 2.5" exhaust. I'm wondering if the bigger exhaust is going to cause me any problems with "boost creep". ...Also, how important is the 190 lph fuel pump?? My plans are not to exceed the stage 1 upgrade other than adding some hard intercooler tubing and a fmic(they just look cool as heck) and possibly a BOV??

I would like to suggest that you consider porting your 14b for better boost control, also, running a 070 turbine housing (think 16g) instead of the 14b's stock 060 housing has been known to both improve performance and help with boost control. If you are able to rewire your fuel pump and keep the 14b from creeping past 16-18psi, you don't have to worry about a new fuel pump/injectors yet.

you will be fine running a 2.5" exhaust on the OEM wastegate setup (no boost creep problems here)...
...get a smaller FMIC (you dont want to outflow the stock 14b turbo with some huge intercooler)

-You should be able to port the turbo enough to use an internal wastegate, but depending on your porting skill and determination you may need a larger wastegate flapper to adequately control boost with any size larger exhaust that is missing a catalytic convertor.
The size of an intercooler does not matter to the turbo, the worst that will happen if you use a big front mount is you will have a split-second more lag.

T25's just plain don't creep. There may be cases, but they are RARE and I've never seen them. The turbine wheel is so restrictive at higher rpms that the exhaust WANTS to exit through the wastegate hole. Hell, t25's have a hard time holding 15 psi to redline because of the flapper blowing open and compressor flow. The flapper also opens much farther than any MHI actuator(14b, 16g etc) will allow.

technician163:
Get an aftermarket boost gauge. The stock one is useless and inaccurate. Then you will know if you are spiking or creeping. BTW, spike is when you have the boost set at say 15 psi, and it jumps to 17 then settles back down quickly after. Creep is when you have it set at 15 psi and it slowly climbs to 20 psi by redline. You'll likely be running 10-12 with a stock setup but you get the idea(the numbers are only relative). With a stock downpipe and especially a cat I doubt you will have any boost issues. Get a boost gauge to be sure.

As for 3" turbobacks, I've had them on both of my awd's. One of them never creeped and the other creeped to 20+ psi in higher gears, exact same turbo(literally), a ported-for-flow 14b.

My suggestion, do ALL of the maintenance first. Then, get a 2.5" or 3" turboback exhaust (makes a HUGE difference in gains compared to a n/a engine), 2g exhaust mani(ported or port it yourself, mbc, and maybe an intake pipe and hard IC piping. A logger would be a good idea for safety as well and only ~$100 on eBay, and maybe a 2g o2 housing now that I think of it. Port the 14b for boost creep just in case, and set the boost to 15 psi and you'll have a fun DD, perhaps 13 second car with decent driving.

EDIT: Rewire the fuel pump! This involves running a power wire directly from the battery to the fuel pump, and using the stock fuel pump wires to trip a relay, hot wiring the fuel pump and sending all the available voltage at the battery to the fuel pump. Typical gauge is 10-12, although I had trouble soldering 10 ga with a dinky soldering gun. I have to admit I was amazed at how much more flow is available.

^^^Great post!!
Matt (Peepers) has already given you plenty of great advice, I just wanted to add a couple of ideas to the pot.

 

[2gdanny]

i just took a look at this and i have to say i agree 100% with peepers that was my problem befor i whent with the gt35r,
and external gate does really solve the problem" well it did for me"


i have my old set up if intrested "technician163"--pm me

 

[Mr Peepers]

Matt, other than being cheaper and easier to do, why would you recommend porting instead of jumping right to your MWGA strategy initially (and skipping the port job entirely (or at least for the time being))?

There are many reasons actually:

Unlike porting, you can mod the WGA with the turbo already mounted to the car. Modding the WGA doesn't cure creep in every case(neither does porting), but porting and a MWGA almost certainly will. This is why I suggest porting the turbo before you put it on, and if it creeps, mod the WGA. The big advantage IMO for modifying a WGA is that it's only 2 bolts, a vacuum ling, and a cotter pin away from being removed, and you can do a test to see if it will work for you. No gaskets to replace, no oil or coolant to drain, no steps backward.

As for porting being cheaper, modding the WGA cost near nothing in my case, just some paint, threaded rod, and scrap exhaust pipe for the extensions. Of course I have a welder and sandblaster at my disposal as well. For porting, only a Harbor Freight electric die grinder and a carbide burr are required for people without any tools.

It all depends on what resources you have really.

 

[GSX4BangR]

I never knew you could mod the WG with it still on the car. I need to do alot more studying on internal WG's now. So by modifying that i could HOPEFULLY cut down boost creep? Im def. porting the turbo before it goes on the car.

 

[Mr Peepers]

I would like to suggest that you consider porting your 14b for better boost control, also, running a 070 turbine housing (think 16g) instead of the 14b's stock 060 housing has been known to both improve performance and help with boost control. If you are able to rewire your fuel pump and keep the 14b from creeping past 16-18psi, you don't have to worry about a new fuel pump/injectors yet.
-You should be able to port the turbo enough to use an internal wastegate, but depending on your porting skill and determination you may need a larger wastegate flapper to adequately control boost with any size larger exhaust that is missing a catalytic convertor.
The size of an intercooler does not matter to the turbo, the worst that will happen if you use a big front mount is you will have a split-second more lag.


^^^Great post!!
Matt (Peepers) has already given you plenty of great advice, I just wanted to add a couple of ideas to the pot.

Thanks!

Just a little side note: 7cm^2(070) turbine housings are actually more likely to creep for the opposite reason that t25's blow open.

With the larger volute of the 7cm^2 turbine housing, exhaust is more likely to make its way out of the turbine than through the WG hole. This is a theory of why 16g's are more prone to creep than 14b's.

To the OP: You really shouldn't be so worried about creep if you aren't even sure if you have it yet or not. If you get a boost gauge and see that you're creeping, deal with it then. If you replace/port the exhaust mani and/or o2 housing, port the turbo for creep while you're at it. I don't really know what else to say.

 

[GSX4BangR]

Alright thanks, im in the process of getting a jdm cyclone motor anyway and i hope to rebuild that so hopefully everything will be fine.

 

[delta448]

Just a little side note: 7cm^2(070) turbine housings are actually more likely to creep for the opposite reason that t25's blow open.

With the larger volute of the 7cm^2 turbine housing, exhaust is more likely to make its way out of the turbine than through the WG hole. This is a theory of why 16g's are more prone to creep than 14b's.

I'd never heard that before... makes sense I guess, 16gs do tend to have more issues in that area. -Maybe an SAFC, a fuel system upgrade and a lil' bit-o-clip would be nice in order to take full advantage of that housing.

 

[GSX4BangR]

I plan on getting a dsmlink so hopefully that'll help out along with a aftermarket boost gauge.

 

[Grescht]

Better check that car for weed. Get pulled over and the sniffer dogs with ruin you for life.

James

My Girlfriend bought an 03 mustang. While we were cleaning it, i was vaccuming under the seats when something got stuck in the nozzle. It was an aluminum pipe and there was also a bag with some stems in there.... DEFINETLY CHECK IT.

 

[tunermt]

Old thread but I think this is an import topic with some recent developments.
I personally prefer an external wastegate as they are able to flow much better than internal wastegates. For oem turbo (being it already has the internal wastegate) a simple port and aftermarket wastegate actuator (2 port) goes a long ways!
My personal vr4 uses an internal gate evo8 turbo and turbo smart dual port actuator + 3 port boost solenoid.
Check out this article for details and explanations of internal vs external wastegates and boost creep solutions.