92 300D 2.5 LOW POWER, SOMETIMES - Page 2 - PeachParts Mercedes-Benz Forum

vstech · #16 02-02-2013, 08:27 PM

Quote:

Originally Posted by 300TD/WI

that actuator swap does look rather simple. but i dont have time do it soon. also a bit curious what bypassing the opv will do. its what they call an over pressure valve correct? how exactly do you bypass it. just un hook vac and unplug electrical? i understand that you have to cap off vac line if i unhook.
any advice? Anyone. image of where it is would be awesome too. so i know im thinking of the correct one.thanks

unhooking the opv is as simple as taking the hose that's on it, and putting it directly onto the alda. nothing needs to be done with vacuum or with electrical.
just move the hose that goes from the intake to the opv, and connect it directly onto the alda. done.

300TD/WI · #17 02-03-2013, 05:42 PM

well I believe I have figured out my problem I have reconnected all the Engr stuff and all seems to be normal again. Which leads me to believe that it is time for a pressure actuated boost controller to get rid of all that emission stuff. But I don't have time for that right now that will have to be a Sunday project in about a month or so. In the meantimein the meantime I would like to know if anyone has any more detailed information on bypassing the over pressure solenoid. thanks

300TD/WI · #18 02-03-2013, 07:53 PM

thanks vstech. im going to try that tonight. but it seems like conclusion is i need a different turbo actuator to have any fun do any mods for economy and emission stuff removal.
thanks again for all input

300TD/WI · #19 02-04-2013, 11:50 PM

My occasional low power issue has been resolved. Hooked all egr stuff back up. Took off intake and egr boiled them out and cleaned them. Bypassed ovp as well. Blew out all the vacuum lines to all the emissioms transducers. Now it drives like a spring chicken... fun and peppy. AWESOME!
Looks like when I have time its time for a pressure actuated wastegate actuator. Then to get rid of all the emission crap.
Now its hard to stay out of the throttle... killing my economy... haa but lots of fun.
Thanks to all for all the great help and advice!

LoosBenz · #20 02-05-2013, 07:45 AM

Good job!

vstech · #21 02-05-2013, 08:05 AM

actually, you should notice an increase in economy now that air can flow properly!
no more uneven burns, and the overall fuel use should drop!
better performance does not often equal low economy... it's all about how much fuel is needed to heat the available air to push the wheels... more air, better economy. the kick in the pants is a bonus!

oh, it's usually preferred to keep solutions within the original thread, not start a new one with the solution...
I fixed it.

Chris_ · #22 02-05-2013, 12:24 PM

Quote:

Originally Posted by pmckechnie

The 90 to 93 2.5 engine control system will disable boost if it sees a problem in the EGR system. Restarting will make the problem go away until it test the EGR system again. Most common fix is to replace the vacuum operated wastegate actuator on the turbo with a boost pressure type, or reconnect the EGR and repair what ever problems there are with the rest of the system. This is going to sound crazy but this is what I did. On the cross over part of the manifold between the turbo and the intake side of the engine there is a valve that can restrict the boost going to the intake. It is part of the EGR test system. If it doesn't work, you will get the same no boost condition as the EGR not working. I modified that valve and made it a pressure operated valve so if the boost goes over 15 lbs, it will restrict the airflow which will regulate the boost. I then hooked full time vacuum to the wastegate so it stays closed at all times. It has been like that for about 6 years now. You can find a lot of post about replacing the wastegate with one that can be made to work. If you choose to do this, just leave the engine control installed as it also does the idle control.

Paul

With full time vacuum applied to the wastegate - what prevents it from regularly ecceeding 15 psi ?
and
I may be entirely incorrect but isnt it the case generally speaking that to restrict airflow regularly can promote other issues such as the tendency for the engine to attempt to obtain the air elsewhere causing other failures... could be totally wrong just my perception.
also
I have given serious thought to how to modify the stock setup to fool the computer into thinking that the EGR system is working ..making it "see" the pressures that it is calling for ... but all in all I came to the same conclusion as many that for simplicity sake ..I just ordered the pressure style actuator.

thanks

pmckechnie · #23 02-05-2013, 01:40 PM

I'll try to explain how my boost control works. With vacuum to the wastgate all the time can let boost go to 20+ psi (That is as high as my gauge will go.) So to control the boost, I use the flapper valve in the intake crossover to restrict the airflow some. It is adjusted so that when the boost gets to 15 psi in the intake manifold it will close off a little. This only restricts enough to drop the boost to the intake manifold. It never restricts enough to cause a vacuum in the intake, just reduce the boost. It has been this way for several years now with no ill effect. In normal driving the boost seldom goes over 10psi. At WOT it will go to 15 psi until you let off some. So the wastegate is just a safety device that keeps the boost at a safe level. The pressure type wastegate lets some of the exhaust bypass the exhaust turbine in the turbo to reduce boost. The other overboost system blocks boost from getting to the ALDA. This cuts down on the amount of fuel the engine gets. Less fuel = less exhaust = less boost from the turbo. There is always more than one way to skin a cat.

Paul

vstech · #24 02-05-2013, 01:54 PM

Quote:

Originally Posted by pmckechnie

I'll try to explain how my boost control works. With vacuum to the wastgate all the time can let boost go to 20+ psi (That is as high as my gauge will go.) So to control the boost, I use the flapper valve in the intake crossover to restrict the airflow some. It is adjusted so that when the boost gets to 15 psi in the intake manifold it will close off a little. This only restricts enough to drop the boost to the intake manifold. It never restricts enough to cause a vacuum in the intake, just reduce the boost. It has been this way for several years now with no ill effect. In normal driving the boost seldom goes over 10psi. At WOT it will go to 15 psi until you let off some. So the wastegate is just a safety device that keeps the boost at a safe level. The pressure type wastegate lets some of the exhaust bypass the exhaust turbine in the turbo to reduce boost. The other overboost system blocks boost from getting to the ALDA. This cuts down on the amount of fuel the engine gets. Less fuel = less exhaust = less boost from the turbo. There is always more than one way to skin a cat.

Paul

sounds interesting, you ought to come over and work on mine...