easily and cheaply increasing the boost E300 turbo diesel W210 606 - Page 2 - PeachParts Mercedes-Benz Forum

oldsinner111 · #1 04-21-2010, 04:19 PM

Auto.I'm just saying when I reach max boost it shifts to next gear.I do try and limit boost to 18 when driving normal.

Alastair · #2 04-21-2010, 05:18 PM

Right-

Flaring is a during gear-change phenomenon....

Auto-boxes are designed for soft changes.--The General Public-- demand smooth rides from their expensive motors!
To actually achieve this, at the point of gear-change two gears are actually engaged--At The Same Time!

--The one its shifting Out of, and the one its shifting Into!

The Amount of 'slip' of the clutches/brake-bands inside the trans is carefully controlled while changing gear.

The 'out-going' clutch or band is released slowly and allowed to slip, and the incoming clutch or band is applied slowly and also slips At The Same Time! and in this way one releases and the other Overlaps and takes over....

Now, when summit Upsets the amount of Power the engine is generating for a Given Trans. VCV Vacuum pressure, then either the shift will be Harsh, (Too little power) or will Slip More (Flaring) -too much power--than was intended, for That amount of VCV Vacuum.

--A very bad case of flaring, while changing from say, 2-3, the engine revs instead of dropping smoothly when the 3rd gear takes up, will actually Increase, then 'snatch up' and go back down as the 3rd gear fully engages--This is an extreme case though!....

A Trans is said to flare when there seems to be a 'sluggishness' or hestation of gear-change,--The change actually taking Longer than it should-- whilst the clutches/band slip and slide in and out of gear.

All this slipping and sliding is actually Bad!--All it does do is create heat and wear, But it Does give incredibly soft, and smooth gear-changes!-
-You Could say that the trans is 'Programmed' to wear out due to this, but if the gears changed more abruptly, with less 'overlap' it would be a very uncomfortable ride, as they can literally Bang into gear if the VCV or vac system is faulty, Causing the faster/less overlap/quicker change condition....

--Worth remembering, that when driving an Auto car, the Engine is giving power all the time the accelerator is pressed --even when its changing gear--
-Imagine the result if you did That when in a Manual Trans car, and did NOT release the accel. during a change of gear!
BMW Z-F 5HP18 Auto-trans, actually tells engine to Power-Down during gear-change to avoid flaring and wear,--all by CAN-BUS control via the Trans ECU and the Engine ECU....

m1tch · #3 05-16-2015, 01:10 PM

I just wanted to add something to this thread as I have just done this mod, but with a difference, I have used the same wire on the MAP sensor, however I have done something different with the resistance settings.

The original mod had the different resistors being removed and replaced, I have looking into this slightly more and used a slightly different method which is adjustable. I bought a 20KOhm potentiometer which is usually used to increase and decrease the voltage or indeed split voltage between different pins. I have found that if you use pins 1 and 2 (out of the 3 pins) you get a variable resistor without needing to use a rheostat.

This means I can adjust the resistance between 0KOhms (stock setting) and 20kOhms (much higher than needed). The good thing about my change to this mod is that it can be varied to any resistance meaning that it can be fine tuned.

I have tried a few different settings on my 100% bone stock car and here is what I have found initially with regards to boost and performance gains:

0KOhms - stock setting, initially boosts to 18psi then drops to 14psi.
12KOhms - initial boost is upped to 20psi which then drops back to 18psi.
13KOhms - initial boost is still upped to 20psi dropping back to 18psi.

I haven't had any flaring issues as found by the OP at the moment and it seems that my stock settings are slightly lower although 20 and 21psi on a basic boost gauge can be hard to tell.

What I did however find when I set it to anything about 12KOhms (or indeed around 11.6KOhms) is that there was a definite lag in boost performance, the turbo did spool up as it would do and did hit 20psi, however wasn't as stable (this could be the issues around flaring or the transmission getting confused).

My E300 sleeper project requires me to get an initial base run which should be done in the weekend after next, I will simply install a wire and remove the variable resistor to keep everything 100% bone stock. I did turn the resistance down to 0 which indeed gave me back the 18psi then drop to 14psi stock setup.

I am still working out what exactly is happening with this mod, my feeling is the following is happening:

The MAP sensor signal is being reduced slightly so that the ECU then tries to up the boost to the stock parameters.
As far as the ECU is concerned the initial boost of 18psi, then dropping to 14psi is attained.
What is actually happening is that the wastegate is being held closed for longer giving the increase in actual boost.
The issue comes in the fact that the engine has 18-20psi of boost, however only has fueling for the 14-18psi at that point.
This would mean that the additional performance gain is actually the increase in boost which then uses up any additional fuel usually injected.
This would be why increasing boost any further would not only push the stock turbo outside of its efficiency island but also not increase power due to lack of fuel.

I am also looking into adding a resistor on the rack sensor which would then mean that this mod, plus the rack sensor mod would combine to increase both the boost AND the fueling but still retain the stock ECU fueling curve.

At some point I will be adding some water/methonol injection which I think will set to come on at above 14psi. This will hopefully then give the additional fueling which would match off with the additional boost the MAP sensor mod creates.

I will be updating my E300 sleeper project on a regular basis as I will be using it as a testbed for mods like this to test out what works well on a stock engine for a bit more power.