Measuring stock exhaust restriction

[Highboosted]

Originally Posted by RobBeck

Even though it sounds like a good idea, I think its just easier to run a heavier spring... unless you find yourself having to purchase an extremely heavy spring to fix the issue. What kind of pressures are you guys running to get this dropoff?

Rob

Thats the thing, their turbos drop off like that under any boost. It only gets worse the higher the pressure. And I think we already confirmed the wastegate arm moving due to backpressure. I think everyone is running the stock springs.......so now another Q: Who is running higher springs in their actuators? Whats your dropoff? You blowing the gate open visually?

[Multiades]

Originally Posted by Highboosted

Thats the thing, their turbos drop off like that under any boost. It only gets worse the higher the pressure. And I think we already confirmed the wastegate arm moving due to backpressure. I think everyone is running the stock springs.......so now another Q: Who is running higher springs in their actuators? Whats your dropoff? You blowing the gate open visually?

Visually?

I think the only "visual" you're going to get is your boost gauge going down, down, down, as your revs go up.

[Highboosted]

Originally Posted by Multiades

Visually?

I think the only "visual" you're going to get is your boost gauge going down, down, down, as your revs go up.

Stupid database errors......

I said something about checking it on a dyno, or somehow use a video camera, but I dont feel like typing it all again.

[RobBeck]

Damon, here is some TD04 info from a thread I was considering increasing the flapper size (which very well could be a bad idea)... if you could plug in the math I would be interested to hear what you come up with. You might also want to consider that the Turbine pressure will likely be substantially higher than what FWombat noted with his TD05s.

Originally Posted by RobBeck

Stock TD04 Flapper is 27mm. Stock Wastegate hole is 20mm. If you want to retain the stock flapper you can port the hole to 22-23mm safely.

It appears you could also get a 34mm flapper from TRE (http://www.teamrip.com/accessories.html). Not sure what it is made of but hopefully it is a high grade steel.

http://www.teamrip.com/images/34mmWGV.jpg

Machine this from 34mm down to 31mm Max.

Then port/blend actuator hole to about 26-27mm (essentially the size of the stock flapper, so you could use the stock flappers contact mark as a guide). So doing this housing mod could get you from about 20mm to about 27mm MAX with the new flapper... or get you about 4mm more if you just port what you have and keep the stock flapper. I have never tested the flapper swap but doing it has crossed my mind.

Rob

Basically, stock flapper hole is 20mm and can be ported up to 22-23mm with stock flapper. Let me know what you come up with.

Rob

Originally Posted by twiceblown

Anyone have the sizes of the flapper and diameter of diaphragm of the TD04 stuff? I'm curious for what i need. I know 9# springs are much better than stock 6#ers, but i'd dying to know what would be ideal.
Damon

[Multiades]

Honestly, I'd say you DON'T want to port the stock TD04 flapper. TD04 turbine backpressure will be very high, and every TD04 I've ever experienced has had boost falloff already. There's no concern of boost creep if it can't help but drop pressure to redline already.

[RobBeck]

They are also very weak 6# actuators... and there is not much that can be ported since the flapper is only 26mm (can maybe get 3mm out of it). Aside from that there are several who basically locked the actuators by shoving 4-5 washers behind them and retain boost falloff to the same degree as before... so I am not yet convinced that is the ONLY thing causing falloff; I have some concerns about the pressure source being so far upstream at the y-pipe (IC losses??) rather than direcly on the comp housing (like alot of other turbos volvos/wrx/etc) along with possiblity of controller insufficiencies. Also there is some advantages to having a bigger flapper hole... better flow out of the turbine housig if the compressor is not maxxed out.

That said, I still would like to see the calcs for a 20mm (TD04 stock) and 23mm (TD04 ported) hole... and even a 27mm (TD04 modified flapper/ported) hole.

Thanks,
Rob

Originally Posted by Multiades

Honestly, I'd say you DON'T want to port the stock TD04 flapper. TD04 turbine backpressure will be very high, and every TD04 I've ever experienced has had boost falloff already. There's no concern of boost creep if it can't help but drop pressure to redline already.

[Multiades]

I agree that some portion of the fall-off could also be a control problem. I'm very dissatisfied with the boost controllers currently on the market. All of them are overly simple, designed to be used by someone who wants zero setup time, and they even fail at doing THAT well. I could design a rock-stupid control scheme that would get better results than what's currently on the market (I just couldn't build it because I'm shite with electronics).

Anyhow, why the interest in larger wastegate flappers at all? It WON'T decrease the turbine backpressure for an underutilized compressor because any reduction in pre-turbine pressure would result in some decrease in boost pressure - the two are intrinsically interrelated. If your boost creeps up, you need more flapper area, if it falls off or stays constant, you don't. Simple as that.

What is the diameter of the actuator cylinder on a TD04? I mean the smallest diameter -- not the lip on the can, but the can itself.

Calcs are impossible without that information, but we also don't have TD04 backpressure numbers.

[RobBeck]

The ID of the TD04 can is ~2.000".

Rob

Originally Posted by Multiades

What is the diameter of the actuator cylinder on a TD04? I mean the smallest diameter -- not the lip on the can, but the can itself.

Calcs are impossible without that information, but we also don't have TD04 backpressure numbers.

[RobBeck]

Agree, however the better flow out of the flapper hole should allow flapper/control adjustments via the actuator rod to require less "slow" mechanical movement and retain better boost control (aside from possibility of flapper blowing open), that is where I was going... but the actuator rod may move plenty fast enough and this all be negligable.

Also, it is possible that when you start dealing with modified housings (bore/diffuser/clipping/etc)... that the flapper size needs to be increased to have an equal affect on control; this thought I am still experimenting with though.

So, if there is anything else needed to formulate this let me know... but 20mm/23mm/27mm (actual hole size) is what I am after.

Rob

Originally Posted by Multiades

Anyhow, why the interest in larger wastegate flappers at all? It WON'T decrease the turbine backpressure for an underutilized compressor because any reduction in pre-turbine pressure would result in some decrease in boost pressure - the two are intrinsically interrelated. If your boost creeps up, you need more flapper area, if it falls off or stays constant, you don't. Simple as that.

[Multiades]

Originally Posted by RobBeck

The ID of the TD04 can is ~2.000".

So then the diaphragm area is approximately pi square inches. If 6psi is full open, 6psi * 3.141592653589793238in^2 (that was off the top of my head, btw ) = almost 19lbs. So if the wastegate port is 20mm diameter, that's about 0.5sq in area, and it would take 38psi of exhaust pressure to force it open.

Now, we're talking fairly vague figures here. If the wastegate actuator cracks the flapper off its seat at 6psi, those numbers are accurate (I've simply solved backwards to find for the force holding it on its seat). AS SOON AS the flapper lifts from the seat, exhaust pressure is reduced somewhat, and continues to be reduced as the flapper is opened further.

With a 23mm port, that number is reduced to 29.5psi exhaust pressure.

With a 27mm port, that number is further reduced to 21.5psi exhaust pressure.

Why go bigger? Personally, I'd recommend a 10psi actuator and a stock wastegate port to just about anybody, and higher than that would still be quite reasonable.

Again, the biggest reason dual-port externals work so well is because of the large diphragm and pressure exerted to keep the valve closed. How effective they are at negating the effects of high exhaust backpressure are related to the ratio of the areas (diaphragm to exhaust valve) and the ratio of intake boost pressure to exhaust turbine backpressure. Of course, this effect is DOUBLED if you mount the wastegate so that exhaust pressure forces it shut instead of open, in which case you could have a creep problem without good boost control logic.

-Chris