Help !!! I,ve got boost but don't have power :( - PeachParts Mercedes-Benz Forum

Joreto · #1 05-10-2003, 03:46 PM

Ok all you turbo wizards I need your help badly !!! I have finaly fixed the oil problem by drilling the oil pan (thanks to Dan16v for his help). Today I assembled the car and went for a drive, boy was there a supprise in store for me !!! The car felt slower to drive then when it was without the turbo . The boost gauge was reading that I'm gettin 0,5 bars of boost but the car felt like something was holding it back and at higher revs it didn't pickup as quickly as before (before it reved more freely). Where is my problem ?? I use pipes will 50 mm diameter from the turbo to the intercooler, the pipe on the exhaust out the turbo is 76mm. Only the input and output pipes of the intercooler are 40mm and the pipe on the box that is on top of the air intake is also 40mm. I suspect two things :
1. the turbo can flow enough air through its exhaust side and creates too much backpressure .
2. the intercooler is to small and its pipes are to thin to flow enough air for the engine.

Are my asumptions right or am I totaly off ???

manny · #2 05-10-2003, 05:37 PM

First thing that comes to mind, do you have enough fuel to go with the boost?
Secondly, how are you managing ignition timing, I believe it should be 2 degreees retard, for every 0.15 bar of boost.

Jim Villers · #3 05-10-2003, 06:11 PM

Manny is right on. At .5 bar (7 psi) I have my timing at 20 degrees and you need a lot of fuel. Mine is set to a 12:1 air fuel ratio. Get a way to measure your A/F ratio before pushing it very hard. I burned a set of pistons learning the importance of fuel and retarded timing.

Benzmac · #4 05-10-2003, 09:26 PM

Are you running an unrestricted exhaust? IF not, what is the exhuast setup?

How are you manipulating fuel map and timing?

Pics???? post some pics of turbo, wastegate and downpipe. Also of intercooler and throttle body.

I have a turbo car and have fixed a few with problems. I'm sure there is an answer.

Maddog · #5 05-11-2003, 12:48 AM

Sounds like a fuel/ignition problem to me. How are you set up engine managment wise?

Joreto · #6 05-11-2003, 08:56 AM

Thanks for your replys and please keep them coming! I'll post pics very soon. I have to develop them since I use a normal camera. For fueling I'm still useing the normal CIS which I enriched. I hooked up a voltmeter to the O2 sensor and it registers values between 0.4 and 0.9 volts at WOT it's about 0.7 - 0.8, thats why I think that it's an air delivary problem. Maybe the intercooler is to small and can't flow enough air so tomorrow I'll test the car with out the it. I'm running the EZL switch on the S position. When a drove the car I didn't experiance the throttle stickedge problem at 0.5 bars (like Jim did), I've changed the throttle spring to a harder one so maybe thats why. Another thing, when I disconnect the air piping of the turbo to the throttle body I can distinctively hear the turbo whistle (at around 2500) but when I connect the pipes I can't here it. I also don't feel the turbo kick in. The turbo is a Garrett TB2536.

Maddog · #7 05-11-2003, 11:45 AM

It definatly sounds like a fuel problem to me. In order to tell if your really running rich you need an O2 sensor seperate from the CIS-E. If you go to summitracing.com, they sell a cheap mixture gauge and you can buy an O2 sensor to go with it. If you put this in your exhaust pipe and only run the gauge off of it (keep is seperate from CIS-E), you should find out where your really having problems.

Where is your boost gauge hooked up? Is it reading from the intake or the turbo compressor?

I dont' think enriching CIS-E will be enough for a turbo setup. The best way to do it without changing over to stand alone engine mangement is to keep the CIS-E in tact and don't change it. Add some extra fuel injectors that will come in when the turbo starts to produce boost. This way you will not run the CIS-E rich when the turbo isn't producting boost.

Joreto · #8 05-11-2003, 03:04 PM

Maddog, I read the O2 sensor data directly from the wire of the O2 sensor. I plug into the connector thats below the feet of the front passenger. The boost I read is at the compressor, I'm thinking of reading it at the intake tomorrow to check if it's the same as at the compressor.
Also consering the timming retard the S position on the EZL switch gives me 6 degrees retard I'm going to try the 7 position which should give me 12 degrees.

Jim, how did you get 20 deg. of retard on the CIS ?? What did you do for enrichment at boost ?

Jim Villers · #9 05-11-2003, 03:47 PM

Joreto .... I installed a Simple Digital Systems engine management system that controls both fuel management and ignition. SDS is a simpler and cheaper solution that Benzmac's TEC 3 installation.

I tried several times to get the CIS to deliver enough fuel under boost and gave up. I also doubt that the resistor switch will provide the results that you need.

Moving to a digital engine management system is not has hard as installing the turbo. Standard injectors will fit in the manifold holes and you just need to make a fuel rail and plumb you existing fuel pump and regulator valve (beware, fuel pressure is 80 psi). Install a crankshaft sensor and a couple of other sensors and you are in business. You really need an engine management system to tune the engine correctly. The
SDS website.

Alain V. · #10 05-11-2003, 07:36 PM

One other item made by SDS is their EIC box. This is an "extra injector controller" that you can use to run a pair of extra injectors while keeping the existing fuel system. Although I kind of view it as a band-aid solution, it is an alternative choice for those running mild boost levels.

My friend that I did the mosselman set up for has been asking me about this and we are in the process of deciding which will be best for his needs. I'd rather just change to an entire SDS EFI set up, so he can easily re-adjust for upgrades in the future.

Another item ,I'm looking into is watercooling the intercooler.
I think I'll install a tpair of temp sensors in the plumbing before & after the intercooler, then test with & without water to see if it makes a decent difference.

Benzmac · #11 05-11-2003, 09:57 PM

You are running out of fuel!!

I have seen some parts borrowed from early 911 turbo cars that raised fuel pressure and changed fuel maps based on boost using a governor of sorts.

You will HAVE to change/manipulate your fuel system to make this work.

The stock injection system was close to its limits at 200hp.

Joreto · #12 05-12-2003, 02:44 AM

After inspecting the system today I found a big hole in the box we made for the throttle body which leeked a lot of the boost. Today I'll fix it and do a test drive.

Jim, I'll also be switching to EFI some time this year (maybe near the end ). If the car leans out to much I'll be useing the coldstart injector for enrichment in the begining, this will be a temparary solution until I switch to the EFI system.

Dan16V · #13 05-12-2003, 04:27 AM

Hopefully that solves your problem. It's always a good idea to measure boost at the intake because that's where it counts anyways...Have you switched your gauge over to there?

Later!

Joreto · #14 05-12-2003, 04:00 PM

Dan16v, I haven't moved the gauge switch yet, but after fixing the problem with the throttle body box I drove the car. Today the car drove nicely I could feel the boost come on and the car felt very strong in the mid rev range 3000 - 5000. However the car didn't rev so freely above 6000 rpm. Before a installed the turbo the car would rev all the way to the rev limiter without any hesitation now it feels like somethink is holding it back between 6000 - 7000 rpm. Could my exhaust manifold be to restrictive ?? It has the same shape as the mosselman manifold except that it's counstracted from pipes. Another question is how do I tune the car without a dyno machine (we don't have one in Bulgaria yet) ? Could I tune the car with a CO2 meter, it's a small one that works on 12 volts and can be used while the car is moving.

Maddog · #15 05-12-2003, 04:37 PM

I don't understand why you don't think your problem is fuel. Your car won't rev high because CIS-E can't supply the fuel!