bayhas

I have a RENNtech carbon airbox, built for stock 74mm TB, I am trying to modify its inlet, to accept the 80mm(78mm) throttle from S65.

I don't have a full mock up of the setup to measure difference in TB neck height properly, so I am going by measurements with micrometer of components,

However, all of the measurements I am taking are junk if I cant confirm on thing for sure:

Does the 80MM super charger snout keep the TB mating surface in the exact spacial location as the 74mm? or is it different?

carguyshu

the 80mm was used in the 07/08 SL55 and the mating surface was the same as earlier cars. know that to put on the 80mm you will need to get an oem 80mm snout from an 07/08 sl55 or port and retap the holes in the factory snout. if I were you I would sell the renntech box and just go with an 82. an 82 (true 82) with a factory y connection will give more power than an 80 (78) with a renntech intake.

bayhas

The mating surface is not the same between 80mm and earlier 74mm models, thus the snout is different, and bolt pattern is different.

I already have the 07/08 snout, and also have an 80mm throttle body out of a 2010 S65

I did not want to go as high as 82mm, due to concerns with need to alter/raise idle speed to avoid intake manifold absolute pressure CEL reported by many members, as well as reported surging and roughness for daily driving. Not to mention the hassle of fabricating an 82mm mating surface, since spacer raised the throttle body, and makes it near impossible to use a modified Renntech box with it.

The 80 was offered as stock in 2007, so it will offer more civilized fitment and performance. I already got the Eurocharged tune for it.

My question was "is there difference between 74mm and 80mm snouts, in tems of WHERE the throttle body mating surface end up being? AKA does the 80mm snout retract or protrude the throttle body mating surface away from the supercharger body?

This is what I am trying to confirm, in effort to modify the Renntech box neck properly

I know I can take the SC out and measure, but I am wondering if anybody knows before I take the car apart, so I would do all fabrication work first, then take the car apart.

carguyshu

I just told you they were the same as the 07/08 Y is the same except for the diameter and mounts the same.

I also told you if you read carefully that the bolt pattern and port size are the only differences.

To switch snouts requires supercharger removal. Hope you are ready for that & FWIW the CEL issues are primarily caused by an old TB bypass valve rubber collar that gets a small crack in it during supercharger removal and not that the TB is 82 instead of 80.

The 80 or 74 snout can be modified to work by adding material to them and retapping the holes instead of using a spacer, though i'm not sure a the renntech box can be ported large enough to support an 82.

while the supercharger is off you should regrease or replace the rear bearings as well as change out the front case fluid (it is mobile jet oil II). Be careful during supercharger disassembly as the case gaskets for it aren't available anywhere (they are reusable) and if you mess one up you are screwed. upgrading injectors is not a bad idea either since you will be removing the fuel rail to remove the supercharger. On both my E55 and SL55 I had a stock injector fail and get stuck open nearly ruining both motors via hyrolock. Given that you can now get a set of 8 550s cheaper than 1 MB stock injector I think its good preventative maintenance.

Check your wiring on your stock TB. you may also need a new harness #1131500028 if the old one is epoxied in. Here are the part numbers of other things you should replace while taking the charger off:

intercooler to supercharger gasket

7.97
1132381082

EGR to supercharger

21.42
1132380982

EGR to supercharger

25.59
1120310033

vac plug in back of TB snout

3.57
005 153 72 28

map sensor

39.87
1131411080

bypass gasket

3.45
2711411280

bypass gasket

2.02
1131410980

supercharger to head gasket (x2)

5.12
1131410780

80mm snout gasket

5.59
1130980080

surge tank gasket

6.31
1130980190

surge tank gasket

1120780092

fuel damper diaphragm

49.98
2731410680

I don't have the part number for the 80mm TB gasket (as I used an 82mm gasket) so I didn't include it.

bayhas

Perfect! Sorry I misread the reply.


Thank you for the tip, I was debating replacing all rubber in the area while I am in there, as they are getting brittle, now I will do it for sure.


The renntech box has enough meat to take the 80mm in (with custom gasket made of Orings, but not 82. To go up to 82, I will have to rebuild the carbon walls on the outside, then tap the openning; Another reason why I leaned toward 80(78)mm vs 82mm, is it will be relatively plug and play with the parts I have.

I was going to take advantage of the job to replace fluid, my understanding is its really hard to get all fluid out with the SC in place. I was not planning on servicing the bearings though. I will look into adding grease

Indeed, I had that failure last year, I still cannot understand how I didn't bend a rod, but I clearly dodged a bullet. I replaced all injectors at the time, as preventive maintenance

The TB I am trying to use is from CL65 with that harness epoxied to it. I posted in another post asking how to take it apart, to swap pings.
https://mbworld.org/forums/w211-amg/...lug-apart.html

carguyshu

if you are just regreasing you will need to remove all the old grease with brake parts cleaner as the factory grease is not available anywhere, even the original bearing manufacturer (I tried) & you don't want old grease potentially chemically reacting negatively with new grease that might have a different composition. I used rheotemp 500 as this grease is used in other supercharger bearing applications. I believe the factory fill is 30% (can't definitively recall from memory) & at around 80k mine had almost no grease left in them. There is a guy now on the AMG facebook group that had custom replacement bearings made for our superchargers and sells them. They incorporate a shield so they don't have the same problems with the grease coming out over time.

When you refill front oil it only take 150ML. if you refill to hole it will come out slowly over time and make a mess of the front of your engine. It is fairly easy to get the oil out with the charger removed as you can just remove the fill hole and tip the thing.


here is what the charger looks like apart. To get apart remove bolts of front case and remove snap rings on rear of rotors

here is how little grease was left in my bearings

austingtir

Im impressed by the spotless condition of your supercharger rotors. Doesnt look like theres a mark on them.

I used redline cv grease in my rear supercharger bearings and they've been fine since (noticeably quieter aswell). Tried to leave an airgap (very little grease) around the outside of the gap between roller bearings to the housing.

I found a combination of spray degreaser and isopropol acohol cans (helped dry it also) got every bit of grease out and left the bearings and casing looking brand new again before installing fresh grease.

Gutentight11

tried 78mm throttle body on mine and my car wouldn’t idle and kept throwing code p2004 IMRC , put the 74mm stock one back on and it’s normal now , does a larger throttle body require tuning ??