Placement of Wastegate

gnxtc2

Well-Known Member
Staff member
Joined
May 28, 2001
I have my Racegate mounted on my stock crossover pipe. I bought a set of headers and the header guy said to put the wastegate right before the turbo and route the exhaust into the THDP. He further said I would have better control. I had no problem with it the crossover exept it would dump into the open, but a good way of knowing it works.:rolleyes:

I want tp get my headers, exhaust housing and DP coated, so I would want all the necessary welding done prior to having them coated.

What's your opinions?

Billy T.
gnxtc2@aol.com
 
From my experience, it WILL control boost better if it is mounted just before the turbo. I would tend to think it would keep the engine more "balanced" as well.
 
I was told that letting the wastegate exhaust into the open air instead of back into the exhaust is also worth a few horsepower from not disrupting the exhaust flowing thru the downpipe, It will not create any turbulence exiting into the open air.
Otto
 
Originally posted by EightSecV6
From my experience, it WILL control boost better if it is mounted just before the turbo. I would tend to think it would keep the engine more "balanced" as well.

I agree whole heartedly[although some guys would differ :D].
If you angle the outlet from the W/G back into the D/P properly,it should merge nicely without much turbulence.
Hint: turbulence at the outlet of the turbine housing is not necessarily a bad thing.:)
 
As I read it by Hugh McInnes,the gas should be allowed to expand to go turbulent and then straighten out to flow more efficiently.
Apparently,the turbulence gets rid of the swirling at the outlet faster than just allowing it to straighten itself out.
 
i can see how that makes sense but isnt the gas coming out of the turbine already turbulent. i would think since its only the gas coming out of the turbine housing and not any extra wg gas in the dp then there would be lots of pipe for the little bit of gas to go thru. and since flow is like the pressure difference b/w 2 outlets then if you had tons of psi in the exhaust and none outside the wg the gas would just flow out the fastest cuz its the most psi difference.
 
Originally posted by turbo buicks
i can see how that makes sense but isnt the gas coming out of the turbine already turbulent. i would think since its only the gas coming out of the turbine housing and not any extra wg gas in the dp then there would be lots of pipe for the little bit of gas to go thru. and since flow is like the pressure difference b/w 2 outlets then if you had tons of psi in the exhaust and none outside the wg the gas would just flow out the fastest cuz its the most psi difference.

The gases coming out of the turbine exducer are actually spinning like a tornado at very high speed[turbines typically spin at anywhere from 60,000-110,000 rpm under boost conditions].
That means that the gases are going like h#ll in a circular direction,but not in a straight or linear direction[the direction you would like it to go].
The hole for the exducer on the turbo is typically from 2.250-2.563 for most modified cars.
The typical D/P diameter is about 3".
So as the gases come out,they expand losing their "cohesion" and their spin to a lesser degree.
That's where the gases become turbulent.
Once the pressure of the gases behind them force them further down the pipe,they tend to align in a unified direction and you get even,straight flow.
I take it by the second part of your comments that you see the exhaust pressure as being lower in the D/P than it is before?
Is that correct?
It should be because energy is being extracted by the turbine wheel[from the exhaust].
The D/P is also larger in diameter than crossover feeding the inlet of the turbo.
Now the pressure and volume drop effected by this can be figured out by running the PV/T formula in SI units[I would figure about 200* F temp drop].
With the drop in pressure and the larger pipe on the outlet side,dumping the W/G output into the pipe shouldn't be a problem unless you've got a *real high* H/P car.
At that I would expect to see a power loss over an outside dump for the W/G because of too much exhaust being handled by too small of a pipe.
 
ya i know what ur saying about the pressure in the dp as lower than in the header of course. what i was saying applies to if you are dumping the wasted exhaust gas into open air separate from the dp or anything.
 
i ssay it should flow more gas and more efficiently out of the wg if the wg is left exiting to the open air rather then a dp
 
That would tend to be true with the way most external gates are plumbed,but if you look at the Houston style or stock style W/G arm/puck,that isn't true to a point.
Years ago Lotus engineers discovered an effect they weren't expecting when they were designing the Turbo Esprit.
They were using an oversized turbo[oversized for their engine,I-4,16 valve,2.2L] and were venting the W/G output back into the D/P just after the turbine outlet[similar to the stock T/R].
The problem was getting the turbo to boost properly[we know all about that one in T/R ville].
What they found was that the exiting gases from the turbine created a low pressure votex that tended to "pull" open the W/G slightly causing lag.
The solution was to vent the W/G output through a separate pipe down to the "Cat".
Problem solved,no more tornado pulling the W/G open.
 
that makes sense. i was just thinking in terms of the posters question about placing a racegate. if he was using the stock style setup it would be good the way you are talking about.
 
Originally posted by turbo buicks
that makes sense. i was just thinking in terms of the posters question about placing a racegate. if he was using the stock style setup it would be good the way you are talking about.

Yeah,I lost track of that question for a moment there talking to you.His guy says to plumb the output back into the pipe *like* a Houston setup.
That could cause the gate to open a little too early and cause reduced W/G flow at higher boost as well as a loss of power due to reduced flow through the D/P from handling both outputs[turbo and W/G] all compared of course to the W/G venting to atmosphere.
The dump style is the one I see most faster racers running.
 
coating (when)?

Have all of your welding/fitting complete then go for the coating. Wrapping does't hurt if clearance isn't a problem after coating (anything to reduce heat works).
 
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