E300TD turbo boost tweaking, possible? - PeachParts Mercedes-Benz Forum

Olivier · #1 08-26-2009, 01:29 PM

Hello, is is possible to play with the Turbo to get the boost earlier? I advanve the pump and the car react better but I love to get the turbo kicking in faster, any way possible ?
Thank you.
Olivier

Deni · #2 08-27-2009, 04:45 AM

Boost controller is the cheapest and easiest thing to decrease turbo lag, but not by much.

KarTek · #3 08-27-2009, 10:34 AM

Since this car has a vacuum actuated wastegate, it's going to be challenging to raise the boost level mechanically.

A switch to a VGT would be an excellent choice to increase the responsiveness on this car.

Olivier · #4 08-29-2009, 04:53 PM

Hiya,
Do you mean that if I was able to block the waste gate, the boost will be there earlier and I'll get more performances?
What would happen if I took the vaccum pipe out of the waste gate? What is the waste gate for anyway?
Thank you.
Olivier

auspumpen · #5 08-29-2009, 05:15 PM

I don't believe there's anything you can do with the stock turbo to induce the boost to come on earlier in the RPM cycle. The only mod I'm aware of would be to find a way to produce a higher amount of boost by delaying when the wastegate begins to open. As has been mentioned, this wastegate is vacuum operated. The valve is normally open and requires a vacuum signal for the gate to shut completely, and thus allow boost to build. The gate begins to open up when the vacuum signal is gradually reduced as the engine computer senses that maximum boost is approaching.

Olivier · #6 08-29-2009, 05:25 PM

Thank you, I look at it tommorrow a little closer, if I take the vaccum out, would that mean that the waste gate would be all close, or all open?
A wee confuse on this.
How about changing the spring on the valve for a stronger one, to delay the opening ( this if the gate is opening to let the pressure out), or the oposite , a stronger spring if the gate need to be shut for longer?
Thank you.
Olivier

babymog · #7 08-29-2009, 09:12 PM

If you're looking for more boost at high RPMs, adjusting the wastegate can do this (although efficiency of the turbo might decrease plus heat). However, the wastegate does not affect how soon the boost builds, as the wastegate will be (should be) closed until boost approaches the wastegate-opening limit (.95bar?).

To build boost faster without changing the turbo or any other mechanical swaps, reducing exhaust flow resistance/backpressure and improving intake flow will create minimal (if any) improvement. Fueling the engine sooner (adjust ALDA) and even slight overfueling will help however as the fuel introduced sooner is heat to the turbo sooner, and expanding/hot air is what makes the turbo spin. Power at the cost of BSFE.

auspumpen · #8 08-29-2009, 09:48 PM

Quote:

Originally Posted by Olivier

Thank you, I look at it tommorrow a little closer, if I take the vaccum out, would that mean that the waste gate would be all close, or all open?
A wee confuse on this.
How about changing the spring on the valve for a stronger one, to delay the opening ( this if the gate is opening to let the pressure out), or the oposite , a stronger spring if the gate need to be shut for longer?
Thank you.
Olivier

You can't really adjust the vacuum actuator (if you remove vacuum, the wastegate will always be open --> no boost ever). The best you can do is replace that unit for a pressure actuated version and then add on a boost controller, which will allow you to custom set your wastegate opening pressures. Having said that, I wouldn't evem bother with the tiny stock turbo MB installed on these; they have a rather narrow efficiency range, so adjusting it will probably just be counterproductive.

Olivier · #9 08-30-2009, 04:36 AM

Thank you all. Interesting about the wastgate as I didn't know when it open or close. Its always open then untill the pressure build up, then shut at a certain pressure and this give the turbo boost.
Auspumpen, the turbo look tiny indeed, and I have to say that I am jealous of Evan's new size, this look like a proper turbo

Olivier

Olivier · #10 08-30-2009, 12:02 PM

If I understood properly, this is not only the RPM that make the boost, but the speed of the gas going out, creating the pressure that will shut the wastegate, is that correct? Then if you want to booster, you need to floor it a wee bit, is that correct?
Today following this tread, I decided to have a look at the wastegate, after removing the engine mount shield, I could understand what was going on there, and found out that you could tweak the bar that commend the wastegate and mve it forward for the valve to shut earlier as its already advance.
I did move it forward about 5mm, and it work a bit, might be the placebo but on first gear, starting, I can feel the boost and the wheels have a little more tendency to spin... Not to sure on third at about 2000 RPM, as it still as a wee lag when you gently press the accelerator ( my first question above?) but if you floor it a little more, the boost is there.
Olivier

babymog · #11 08-30-2009, 01:00 PM

Normally the wastegate is closed. It starts out closed before you start the car, remains closed as you drive the car, only opens if the boost gets higher than the designed limit.

Changing the length of the actuating rod will change the pressure where the wastegate opens, but as this is a safety valve of sorts to protect the engine and turbocharger, you should not adjust this unless you know what you are doing / what the new opening pressure is.

Since the wastegate is closed on acceleration until the boost exceeds the (.95bar?) limit, and that usually shouldn't happen until high in the RPM range at full-throttle, you can now understand how wastegate adjustment will not effect off-the-line performance unless you are dumping the clutch at high-rpm.

If the wastegate is defective/stuck open, this is a different issue and probably not cureable by mis-adjusting the wastegate linkage.

Olivier · #12 08-30-2009, 01:10 PM

Humm, would that be then that my wastegat was not acting properly and by moving it manually few times I put it back in place and that what I did as nothing to do with a little gain on first?
Now I am wondering, if the wastegate is close and only open when the pressure exceed the norm, what I actually did by moving the rod was that the wastegate would open earlier, therefore loss of gain? I am correct?

babymog · #13 08-30-2009, 01:19 PM

If it opens earlier, you have reduced the peak boost available and therefore some peak power.

Olivier · #14 08-30-2009, 01:25 PM

I need to reverse this then

To my understanding it was the other way around.
Thank you.
Olivier

Olivier · #15 08-30-2009, 02:14 PM

Back to reverse the other way around. Now another question, I didn't really try it but it seems a wee moresluggish, I put the screws back the other way about 5mm, will it be a tipping point where you actually open the valve pushing it the other way around or will it shut completly at the end?
Cheers.
Olivier