Mansour Khan

So here is a little issue I have been having with my boost levels at the moment.

Car is a stock 2003 E55 with all maintenance done on time and all preventive maintenance done as per recommended by a reputed Indy.

Car is currently at 227k kms.
My boost levels logged do not cross 8.7 psi (torque pro). In the hunt of boost leaks. I smoke tested the system. No leaks found. As a precautionary (and relatively cheap) measure, I replaced the surge tank gaskets, throttle body gasket and the IAT sensor below the throttle body.

I was quiet confident during the surge tank gaskets replacement as I noticed there was silicon used on one side (the injector service guy must have done so because he was the last person other than my Indy to open them up).

Still to no avail I see the boost levels STILL at the same 8.6-8.9 psi. I disabled several other sensors on the Torque app and only look up boost and IAT. Noticed I hit 9.2 and then fluctuating between 8.1 and 8.8. I know this sounds like belt slip, however, I should AT LEAST see a 10 psi somewhere even by mistake at any time.

Any pointers?

I’m at sea level in the UAE (Dubai). Boost measured is all the way from the second to the third gear top end.

P.S. I inspected all my intake valves visually when the surge tanks were off, saw nothing abnormal (if this is related in any way)

(I lost to another stock E55 and hence my search for this boost issue)

C32owner

You should see slightly higher boost in 4th gear when WOT from 3rd to 3th gear change. Temps are higher in Dubai so your boost will also be a little less. Did you log the other stock e55 boost to see what he was achieving?

Mansour Khan

I understand seeing slightly higher boost in 4th. However, I am just not making enough power to keep up or even give a slight competition to a regular e55. The other car noted about 11.2 psi of boost on a second run the following day

C32owner

Yeah this is quite a difference then between your 2 stock vehicles giving nearly 3psi difference. That's around 40hp hence he is out front.

bbirdwell

What year is the other E55? If I remember correctly, later models used a supercharger that was geared to produce slightly higher boost. Don't know if this is an issue but it has been mentioned on this forum before...

Anyone else in this Borg collective remember what I'm trying to remember?

Possible belt slippage?

Mansour Khan

The other 55 was a 2005. Mine is an 03.

Mansour Khan

New update on the issue. I used a different Gates belt from the other 55 (green with no bwk) and noticed that I logged 10.4 psi and then erratic logs of 9.4-9.8.

I have the normal black Gates belt which leads me to believe I have a lot of belt slip. Now the question remains, even if I use the green belt how do I take care of the belt slip?

Ordering a bwk is understandable but why such a big diff in the 2 cars? The other car seems to have no belt slip and is consistent on boost levels.

any advice?

C32owner

First obvious question is both belts the same size? The belt wrap kit should help with that problem. However you are stock pulleys, and believe you should not be suffering belt slip. Maybe your belt is older and has stretched with age causing your slippage. Just buy a new belt correct length for your stock setup.

Mansour Khan

My belt is only 2 weeks old. Same length. Other 55’s belt is 4 months old.

GinDistiller

Have someone rev the engine in neutral while you look at the tensioner for the SC belt. If it's really jumping up and down on revs you might want to replace that too. Although the BWK takes some of the job stress off of that too.

And yes, the 03 has a supercharger geared lower (4-5% I believe on gear ratio, can't remember what that translates to in boost numbers). I swapped mine with an SC from an 05-06 when I had to pull it for other work, seemed to bring boost a little faster and harder but I don't have back to back logs unfortunately.

Mansour Khan

So I got everything checked out. Replaced tensioner with a new Febi piece and also adjusted my pulley gap to 0.40 mm. Car is still not making enough boost.

now I have a question regarding my exhaust. I know that the exhaust can have some issues with boost if not right. I only have a resonator delete going into CLS63 mufflers. However, I am now considering the fact that my secondary cats are toast. I saw a little dent on one of the cats today at the garage. However there is no rattling or sorts in any of the four cats that I have installed.

any pointers?

GinDistiller

Back pressure testers aren't too expensive, you'd measure in all 4 o2 sensor bungs to check for clogging in primary and secondary cats. Need to look up 'normal' values but even a noticeable difference left to right would indicate an issue. However...backpressure is also needed to create boost, not sure at what point too much would actually cause you an overboost problem.

What are your MAP readings at idle? You could also have an issue with the sensor if it's reading incorrectly giving you bad data and improper fuel and timing.

Mansour Khan

If by MAP you mean the same sensor that reads boost, I get 19.3 vacuum at idle.

if another sensor. Please point me to it.

GinDistiller

Hmm I see 20-21 so that's close enough to not be a big red flag. I wish our cars had an easy port to tap to read actual physical boost on the charge side, but if your car is running smoothly otherwise I wouldn't break your knuckles tossing a MAP sensor in for no reason.

So if I read this thread correctly, you're now topping at 10.4 and the other E55 with higher geared SC is at 11.2? That might fall within a Mercedes tech's definition of 'acceptable'. Did he also run the same size wheels and tires? That can have an effect on load and may show higher boost in a lower gear as a result, lots of little variables like that.

If it were my car, next step would be a compression and leakdown test, just to rule out internal health of the motor. If you're due for plugs and wires it's a great time to do that too. Wish I had easier suggestions going forward, good luck!

Mansour Khan

Unfortunately I am unable to maintain those high numbers. I get a consistent 8.7-8.9 psi with ONLY the boost parameter being logged (to rule out any possible delay)

other e55 is my own car. Same exact specs with same OEM wheels and same tires. He (other driver) pulley away after 120 mph as if I was in a 4 cylinder car...

I will look into a compression test early next week and update.

Baltistyle

Is your intercooler pump working properly?

do you know the condition of the original pulley clutch surfaces? This is an area that can slip as well.

Mansour Khan

Intercooler pump working as intended. IATs in check.

When I had the pulley off, I did not see any significant wear and it seems to hook well on engagement.

M901324

Hi all,

I have an issue with my MERCEDES-BENZ A-Class (W176) A 220 CDI (176.003) Diesel 170 HP 09/2012. The gear change has been slow and power feels low. The engine light came on and local garage identified 2 fault codes: boost pressure short circuit p023700 and communication with electronic selector level has a malfunction c29100. They advised I take it to transmission specialist which I did, they only found the P023700-Boost Pressure Sensor has a short circuit to ground fault which is probably because the local garage cleared the fault codes prior and this is the only one that returned. The car has never had transmission fluid changed and has done 84000 miles so far, so I'm having that replaced currently to rule this out. Forums point towards the boost pressure sensor being faulty, but has anyone had a similar issue? Any help would be appreciated as the transmission specialist is saying the transmission is fine and take it back to local garage to check the engine side of it out!

Thanks,

SICAMG

Your in the wrong forum my friend.