so on my turbo 305 (gm 4 turbo) i made the turbo external wastegate from internal and i cant figgure it out, ive driven the car on the road 2 times and both are with out boost, the spring i have the gate feels (i dont know for sure what it is) to be about a 9 psi spring, on the gate its self i have 2 vac fittings one on the side and one on the top. what one do i run vac to??? also it sounds like the gate is opening at idle (open dump) what causes this??? and is it related??

THANKS

I'm not quite sure what you mean. Did you install and external wastegate, or are you still using the internal gate? First of all, those 6.5 turbos had several different style of wastegates.

The real early ones were really weird in that they only used exhaust backpressure to open the flapper valve, the WG actuator was simply a spring device that pulled the flapper valve closed with low exhaust pressure. Surprisingly, this device worked quite well at maintaining ~7psi of boost pressure, but it would need to calibrated to each engine.

The newer computer controlled wastegates on the 6.5T used vacuum to open the gate. If you apply vacuum to the actuator, it opened the flapper valve. The ECM controlled boost by regulating the vacuum to the WG actuator via a PWM solenoid.

I'm not familiar with any 6.5T with dual WG actuator ports. On most automotive applications, a dual port internal type WG actuator needs a boost reference line connected to the top port so the pressure on the diaphragm will extend the rod. On external gates, such as Tial, the boost reference is connected to the bottom of the actuator so that the boost pressure acting on the diaphragm will raise the valve off its seat.

I really think if you spend a minute or two looking at it and thinking through how it works, you could figure it out. They are quite simple really. If not, just disconnect all the signal lines to the WG actuator and drive it to see if you have boost. Be careful, because with no WG signal the turbo will keep boosting until you drive over your crankshaft.

i welded the oem flaper door on the gate shut and i am now running a aftermarket external wastegate, what i think is happening is the spring inside the gate isent strong enought to hold the gate shut, tommarow im going to take it back off and drill and tap a hole on the top of it for a bolt to pr load the spring

Connect the one on the side to the boost pipe directly after the turbo and before intercooler (if you have one). The other one should be open to atmosphere.

im going to to go and do that right now so i dont forget, thanks

ok after making a set up for the gate to pr load the spring and welding a nipple into the charge piping after the turbo outlet still no boost, so i hope out of the car (wearing flip flops) and walk to the front and start to rev it and i fell air being blown on to my foot......end of story i hade a .25 size hole on the back side of one of the coolers jb'ed and we will see if it holds tommarow

hey high c i was just wondering if you did all of your own work to your car im interested in your turbo manifolds how did you get that turbo mounted?

yes i did all the work on my car, i used the stock headers but the were modded, i would be more then happy to take some pics of my set up for yea if you would like

Hey, when you get it going I'm just curious how much power you get out of that GM4 turbo and how it spools. Good luck with it.

ok after a quick junt up the road today (took off the intercoolers) im geting 4 psi witch im fine with the turbo starts to spool around 2600 rpm and im at full boost by 3200 i could not be happy at the way it preforms, i cun lunch at 2000 rpm get a little side ways and be on my way, but from a roll (10 mph) in first and i jump on it not a tire spun and she squats and is gone, there is really nothing i would change about it (maybe the external wastgate but we will see) i have a vid of tonight doing my first boosted burn out but im on 56k dial up and the vid is over 30 MB so you see the problum

yea i would like to see some pictures

Your efforts are awesome, but are you familiar with mandrel bent exhaust tubing? For $35 at JC Whitney you can get a 3", 180 degree U-bend. This is just a suggestion.

hey, I just saw something and I hate to razz on you or be an imposition but could you move that fuel line that's right by the manifold and/or put some heat shielding on the manifold? Just sayin, I'd hate to see all that work go up in smoke.

yea i know they hade them but i didnt know they were that cheap, but i dont have a job.....
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thanks man but its a optic eloshion (wow spelling) its really about 5"s away from it

driver side ext pipe gos between the motor mount and the oil pan, the only pic i dont have is the one the conects each to the other

stock header with the ext out let cut off the stock local and a hole cut in the top front side
i know there not the best looking welds but they are air tight but there the best i could do on a 5 degree day in a un heated place

You did a nice set-up for being ultra budget minded and in a 5° shop I love to see people doing stuff with what they have available.

How does she run now with the intake plumbing sealed up?

Edit: Oops, I missed your post above. Great to hear it's working out for you. Do you plan to reinstall the IC's?

maybe down the road when i want to boost around 7-8 psi but until then, i have a n20 kit to install and a one off intake mani to get done. but after that i think ill find a better car to start on (when i got the car its been hit in the front and the floor is starting to rust bad) but i do like the 305 it has

Um, where does a diesel get vacuum from?

I have to ask (please don’t take this the wrong way, just really curious) how old are you and what do you do?

the vacuum pump.

The vacuum pump.

Was that second question directed towards me? If so, I'm 24 and am part owner and a tech at an auto repair shop. I don't do a lot of Diesels, but I rebuilt a '93 6.5TD (mechanical fuel pump) a year or so ago and learned a little about the 6.5 through that process. A few weeks after that, I did a head job on a '95 6.5TD (electronic fuel pump) and learned a little more. Don't ask me why GM thought vacuum or exhaust backpressure was a good source of WG control when you have the intake manifold pressure there to do the same job simpler and probably more reliably.

im 22
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if this is for me, im 22 and have a hand full of ASE's but no job, oh and im CRAZY