What are the opinions on external wastegates? Anybody like a particular brand and why?

 

yeah Im kinda curious as to why as well. the twin turbo kits I put on cars at our shop (incon, TDC, etc) always had the intergal waste gate, I see guys building some here and eliminating the one on the turbo, why is that? It seems contrary to the conventional simplicity? Please edumacate me on why this is done or why some of you have chosen to do it.

 

I could give a couple of answers to this. First, most of the turbos that we’re talking about are a combination of parts that were usually used on larger dieses which were designed to run at pretty much a steady rpm. These turbines were sized exactly for the needs of the engine, so a wastegate wasn’t used, and spooling speed didn’t matter. When used on a gas engine, usually a smaller turbine was combined with a larger compressor to spool faster and then a wastegate was needed to keep it from overboosting.

External wastegates have other advantages also, mainly that they can be sized larger to better control boost, often are easier to package, and some might argue increase efficiency by not forcing all the exhaust to travel through a smallish compressor housing as with an internal wastegate.

 

simply stated.....flow and horsepower

there is only so much air that can be bypassed internally before it becomes a restriction and creates other problems

 

is it the ability of a certain amount of HP in an engine to be able to surpass the capabilities of a built in wastegate as far as exh flow goes? where as the built in wastegate would be unable to release enough exh gas to stop boost from building?

 

It’s not like you reach a certine HP and you need a specific size wastegate, no matter what turbonetics, PT… want you to believe. I know someone using a deltagate (usually recommended for up to about 350hp) on a car running 9’s at 140mph with no boost creep.

Basically, the smaller the turbine and/or the more exhaust gas the engine produces the larger the wastegate you need. You’re pretty much stuck making an educated guess for most engines.

 

That goes for the "built in" wastegates as well? I see guys building home made turbo setups with T3's and mild steel but they still got through the extra hassle of puting those delta gates on, is it because those turbos are so small? The T3 powered callaway vettes didnt have those. I have seen one of those Callaways where I believe the guy modified the short block because he was cranking up the boost and running high 10's when he rented the track, and 12's on the regular bracket nights. He was still running the T3's and no exernal wastegate. I'm just trying to understand what happens if you dont run external? When do you say well Im going external when I build mine because of X?

 

As Mark mentioned, it's not a matter of you need an X wastegate at Y amount of HP. Folks go from no wastegate to an internal wastegate for the same reason they go from an internal wastegate to an external, and then from a small external to a large external. If you're creating more boost than you'd like (overboost, boost creep, etc...) you need to have some of the exhaust bypass the turbo, which is what the wastegate does. A wastegate that's too small won't let enough exhaust bypass the turbo, so you'll still be overboosting, so you upgrade to a larger, or freer flowing wastegate system (such as open dump pipes from the wastegates).

 

Is it possible to "over-wastegate," per se?

 

Sort-of. If you only need to bleed off a little exhaust, having a huge wastegate would not give you enough control, similar to using a firehose out of a hydrant to water your flowers All wastegates that I'm aware of are actuated by vacuum (whether the vac is electronically controlled or not). If the WG is huge, and opens all the way, the boost might drop below the desired level. That all being said, I haven't heard of anyone having to switch to a smaller one.

 

Gotcha, makes sense

 

Pressure, not vacuum…

I’ve heard that explanation before, but I’m not sure I believe it and have never seen it happen even with something obnoxiously large. After all, it’s just a simple feedback system, boost goes high enough it opens the valve, valve opens, boost drops, valve closes. Unless you’ve got an excessive amount of volume or a restriction in the signal hose going to the wastegate, I would be shocked if you ended up with a problem.

 

Doh... I meant air actuated.

When I had the wastegates run off about 4' of 1/8" rubber tubing, T'd off another connection, there was major boost creep. I changed it to about 1' worth of larger ID tubing, with individual lines from the intake piping to each wastegate, and no more problems. I'm sure I'll need some larger wastegates with the new engine, since twice the HP, means twice the exhaust energy, and the original Deltagates probably won't be large enough.

 

my brother has a t3 turbo on his 4 banger ford thunderbird, he uses a hks super suquential blow off valve. is cam with a waste gate but he apparently replaced that with a "blow off valve". it makes a cool sound, and its loud..