55 Trim or HX30 - PeachParts Mercedes-Benz Forum

awsrock · #1 05-28-2014, 11:54 AM

I've been gone for a while but I am back with a "new" 87 300SDL. I used to have an 87 300D and had plans for a VNT but ended up abandoning that. Anyway, now that I am back in the game I am thinking about doing a few things, along the lines of GSXR and Babymog.
The question is, for maxing the IP I have, would I benefit at all from going to the 55 trim T3? Or one step above that, an HX30? I may one day try to get some 6 or 7mm elements but for the time being I am not looking at that route.
It sounds like there is indeed some benefit to the 55 trim, and it would be an easy swap. I just don't want to waste the money and time if it is going to be negligible. I used to have a late model .97 exhaust manifold that I sold, man am I kicking myself for that. Oh well.

awsrock · #2 05-28-2014, 05:33 PM

I am partially basing my theory on the fact that GSXR got about 15 more hp from switching from the KKK to the 55 trim T3. Granted, that was with the 6mm pump, but it was also only a 2 psi difference between the turbos. I am guessing that there would still be some gain, maybe 6-8 hp with a maxed stock IP, and possibly more low end due to the better compressor wheel. HX30 might be a whole different animal if it can spool faster?

awsrock · #3 06-02-2014, 11:41 AM

Well, as an update, I ended up getting a 55 trim in good shape. Not sure when I will install it, but I'll let everyone know what I find as I go through the various tuning stages.

cho · #4 06-03-2014, 04:16 AM

.

let see what 2.5mm inducer difference can do

.

awsrock · #5 06-03-2014, 09:21 AM

Lol, well, probably not much, but at least we can test to see if folklore of the 55 trim compressor map is really due to it being more efficient.

winmutt · #6 06-03-2014, 03:01 PM

I was very happy with my HX30W with and without upgraded elements. My first was non divided and my current is a divided scroll. I would have gone with the HX30W, it would have given you the opportunity to budget for 3" exhaust as well.

awsrock · #7 06-03-2014, 09:29 PM

Winmutt,

I may still change some time in the future, I did not pay a lot for this turbo so I can probably resell it down the road for the same. It's too early for me to know whether I am going to upgrade my IP elements or not...if I do, I will likely need something more.

How much was involved in getting the HX30 to fit? Did you still have the US spec manifold? I think I read you saying it just needed a new oil fitting and some exhaust pipe work?

winmutt · #8 06-03-2014, 11:27 PM

No, I have a euro manifold. The only hard part was finding an oil feed. I ended up going to a hydraulic shop and they brazed the fitting on.

awsrock · #9 06-13-2014, 07:46 PM

Well, it turns out that I have a KKK turbo, so this swap may actually benefit me a bit. When I had my 300D I had the Garrett 50, and I put in an MBC and had the boost running around 14 psi. The power / curve was much better than what I have now. This KKK on the SDL is running 11-12 and even though everyone says it spools better than the Garrett, I disagree. Perhaps I have some wastegate creep going on, who knows. Boost starts around 1900, and I can get 5 psi around 2200-2400 when accelerating "normally". It does seem to act inconsistently via the butt dyno in my day to day driving.
At the very least I will gain that 5mm extra on the turbine side, lol. I'll probably add an MBC to the 55 trim as well, it seemed to lower the onset of boost by 1-200 rpm when I used it before, and also made it stronger when shifting into higher gears. Since I shift at or into the 1900-2100 range, that does make a difference in daily driveability...just my opinion! I will have a range of boost info to compare once it is installed. I might skip the MBC too since the 55's wastegate did not budge at all to at least 12 psi when I tested it.

awsrock · #10 06-16-2014, 10:11 PM

Turbo is in...took me a most of the day. Will have some actual data tomorrow, but overall I am happy. It seemed not as good at first, but after a few short trips around today, it actually seems much better. The power band seems much more linear, vs the quick onset of boost with the KKK. I have not done a WOT test yet. I am also using less throttle to go around town slowly so I might actually be building some boost earlier...or the larger turbine is just breathing better.

awsrock · #11 06-17-2014, 09:58 AM

Ok, got some rough data now. Here goes:

(Car is stock, slight ALDA adjustment, but could probably be adjusted a bit more)

Boost begins (under normal acceleration)
KKK: 1-2 psi by 2000
55: 2 psi around 1800-2000 (with torque converter slip I can get a solid 2 psi while accelerating lightly in 2nd and 3rd below 2000 rpm)

Cruising at 55 mph
KKK: 3.5 psi
55: 3 psi

Max psi:
KKK: 12
55: 13.5
-Did not make adjustments to either wastegate

The KKK definitely got to max boost faster once it began spooling, but the 55 is not far behind and pulls harder even at a lower psi. It is much better above 3000 rpm as well, but that might be due to the extra 1.5 psi it is producing.
Another thing I noticed is that with the KKK, I had to give it a good amount of pedal to get going from a stop and then the boost would kick in pretty hard, whereas the 55 seems to take off better and the boost builds slowly but overall it feels like I am using less pedal to get to the same speed.

Anyway, if you come across one of these for a good price, it would be a decent swap. I am planning some mild IP work in the future which was one of the main reasons I got this turbo, but also did not want to fabricate too much (i.e. Holset)

I'll do an MPG update down the line, but I have only calculated once since I got the car, and I got 28.7. At around 520 miles per fill up, it takes a while to get new readings!