The spot where my kit is fabbed up for a wastegate is too close to the eingine compartment wall, the wastegate is too big and wont fit. I'm going to be running a T76 GTQ and want to run about 20-21 psi anyways so will i need a wastegate or can i just run without one? Will i run into any problems with this?


My motor is a R-blocked, all billet internals anyways so i want as much power as possible anyways. Thanks!

 

Can you go sky-diving w/o life insurance?

 

haha, point taken...

 

You won't be able to control boost, and you'll over-spin the turbo. Basically, without a wastegate that turbo will become a nice Christmas mantle piece decoration.

 

can you cut up a little sheetmetal?

 

I had the wastegate on mine stick closed.... once.

I saw 30psi of boost (very briefly) before the block developed "windows". Running without a wastegate would essentially be the same as trying to run without a throttle return spring. Somewhere along the way something BAD is gonna happen!

 

I agree, even on a motor that could take high boost, you're going to over spin the turbo. Even if that doesn't happen, you will see outrageous boost levels at low rpms.

Nearly impossible to tune with no wastegate. You won't have a consistent boost level throughout the rpm band.

 

That doesn't make sense. If you want max boost/power out of a turbo, close the gate. That's what I did on my twin 60-1 and twin 66 setup. Ryan Woon does the same thing on his supra.

 

I'm sure you will get max boost/power, but at what expense. I mean at some point you would be surpassing the efficiency rating of the turbo, cause extra wear on the bearings, and create excessive heat.

At that level it would make more sense to upgrade the turbo than working it to death to get max power. For example, let say my goal was to make 550RWHP. Would I use a T44 and "max it out" to reach my goal, or find a turbo that will efficiently get me there?

 

I've seen a few full race setups with no wastegates. Mike Dees and Griffey had the wastegate welded up on their drag radial machine at one point last year with one of the very large turbos. It actually does work on SOME applications. You have to be willling to chance things and keep track of boost in testing because every setup will be a bit different. I've run with the wastegates completely unplugged on mine and if I hadn't made the boost I wanted, I would have probably tried blocking the wastegate off. I wouldn't necessarily recommend that for 99% of the cars and drivers out there with turbos, though.

 

Ive seen some twin cars with the waste gates locked shut. One guy running low 9's had his gate arms flipoped so that it would pull shut and had the hoses routed to keep them shut. He saw 33# with no muffs, and 28# with 4" muffs on it.

 

How do you know if you are overspinning the turbo? I have a T64 and am producing around 8-9 PSI with the wastegate. I just dyno'd it at 422 HP at 5K and 466# at 4K RPM. (this is with one cylinder with 85# of compression and the others at 150#)

I then wanted to know what it would do without the wastegate, so I unplugged the boost line to it. I slowly brought up the boost and found out that I max out at 14#'s. I then did several tests and 14# is all it produced (this is all below 4K RPM, I need to do some Tweecing before I go about 4K). If I run the wastegate disconnected at producing 14#'s, am I over spinning my turbo?

Craig

 

I guess it all depends on the exhaust systems' efficiency, and the stength of the wastegate itself.

I have run mine unplugged as well and could only get 15 lbs. I then shimmed my gate tighter (long story) and it climbed to 20 lbs still unplugged. I'm confident that if I tighten up my gate even further I will see more boost.

There are a few variables to consider before deciding if your turbo is over spinning or not.

 

you are definitely not over spinning a T64 at 14 psi on that engine. You could have been forcing the gate open. Sometimes to keep it closed you have to apply positive pressure.

 

I had one of the turbo kits manufactures at this years World Ford Challenge tell me, there is really no such thing as overspinning a turbo.. I had ask them the same question as you did.. I want the absolute max power from my T76 / 383 combo and I felt that the waste gate that came with the kit is too small.. He said for what I'm trying to do, a small waste gate is all I'll need.. And that I may end up disconnecting it.. That's when I asked about overspeeding the turbo and got the answer I did..

Look at a T76 compressor map.. The max power is made at like 38 lbs of boost (3.6 pressure ratio) and 95,000 + turbo rpms..

 

You can definitely overspin a turbo. I have seen grenaded turbos. The wheel material and structure primarily determine the max RPM before failure. Many compressor maps indicate a max RPM limit. There are some applications where you can run without a wastegate. It mainly comes down to sizing the exhaust housing correctly. There are a number of diesel applications that do not use wastegates. If the exhaust housing is sized so that the exhaust does not build too much pressure behind the turbine at the boost level you desire, then you should be OK as long as the compressor is sized to move that much air at that pressure. For example, if you use a .61 A/R turbine housing on a GTS76 on a 400 cu. in small block, you will probably build boost until the motor breaks. A .83 A/R housing would probably be about right. A 1.06 A/R housing would probably limit you to 20psi boost, or something like that, because you wouldn't be able to build enough pressure behind the turbine to spin the compressor beyond 20psi. So basically, you can run without a wastegate, but it will take some experimentation with turbine housings to find the right one.

 

I see you point !!

 

Well, it's not really fair to compare turbocharged diesel engines to turbocharged gasoline engines, due to their vast differences in air/fuel delivery and the ignition of the air/fuel mixture. Diesels do not have throttle bodies, but basically have a TPS on a "dummy" gas pedal. The fuel system injects fuel directly into the combustion chamber at TDC. Regulating this amount of fuel controls the energy in the combustion chamber, which can ultimately affect the amount of boost. Less fuel, less combustion energy, less exhaust volume, less boost.

Besides, my buddy's stock (wastegateless) 1997 F250 Powerstroke diesel only makes about 12 psi boost. If I took that same turbo and put it on my 1994 GT, I assure you that I could blow that sucker up easily with a ton of boost due to the lack of a wastegate. Diesel vs gasoline is sometimes apples vs oranges.

Diesels use a higher AR exhaust housing because they don't really care about spooling up quickly for a good 60-foot time (nobody drag races semis? hmm, weird). They are concerned with continuously hauling a full load up a steep highway incline, and you would want less exhaust restriction here.

Mark

 

About a year ago, my machine shop had a 500 cu big block chevy with twin t66, p trim with .81 on center housings. The motor had so much backpressure it was scary. They swaped out the .81's to 1. something and it made 1250 hp with the gates forced shut. The same guy that owned this big block also had a small block ford with a cartech twin system. The same turbos were used except the ford used the .81 turbine housings. The ford made 1225 hp at 25 psi with the gates forced shut. The dyno is a superflow 901, all numbers are corrected.

This is just food for thought.

 

The owner previous to me on my Incon 1000tti kit wired the gates shut with no ill effects. Now hot cycling the thin housings did a number on them.