M104 engine specs. - Page 2 - PeachParts Mercedes-Benz Forum

MAG58 · #16 11-28-2011, 02:18 AM

Quote:

Originally Posted by 400Eric

Thanks Bob.

I was amending my post when you posted. There is a new fourth paragraph now. Would you happen to know about the R129 M104s?
Regards, Eric

Not much past the information I can scrounge in the FSM. The FSM does show output of the .980 and .981's to be exactly the same, so perhaps there is no difference in intake cams of the .981. That was just conjecture anyway, I didn't have any factual information. The FSM lists them both at 10.0:1 compression, 170kw output at 6200rpm.

The .991 appears to be identical to the early LH .990 internally with the 10.0 SCR as opposed to the 9.2 of the E class. Actually it appears that the W140, R129 and W210 (1 year only) were the only cars to receive a 3.2 that's a 10.0SCR all W124 2.8's and 3.2's are 9.2 SCR.

400Eric · #17 11-28-2011, 04:27 AM

But what about what year the R129 M104 got the HFM system? Was it 92? That was the question that I posted in my fourth paragraph of the earlier post.

About that funky compression ratio spec, I honestly believe that ALL factory M104s (except for the 3.6 as you noted) have 10 to 1 compression. I think that 9.2 stuff is just a typo. Somebody put the M103's spec where the M104 spec should have gone and the error just kept getting re-perpetuated.
Regards, Eric

MAG58 · #18 11-28-2011, 08:13 AM

Sorry, W124 changed to HFM in 1993 while the W129 held out all the way until 1994. There was no 320SL. They went straight from the 300SL-24V to the introduction of the 104.991 in 1994 in the SL320

400Eric · #19 11-28-2011, 11:50 PM

So this means that there are no 92 HFM M104s which means there are no HFM M104s with WOT fuel enrichment. That's a serious drag. I know Old Sinner is gonna be disappointed to hear that too.
Regards, Eric

whipplem104 · #20 12-03-2011, 08:06 PM

Check this out the specs do not make sense to me the duration and timing just do not seem correct. 180-167 degree cams just seem way to short. These specs can not be right. Exhaust maybe but intake seems all wrong.
So someone check my math on this I was looking at cam timing. Joreto and I have been talking about this on our cars. According to the pdf that MAG linked to the Cam timing is 36-36 for the intake and 30-13 for the exhaust. Or 34-34 and 31-14. I calculated the centerline for each cam at 134 degrees on the intake and 233.5/234 for easy math, for the exhaust. That leaves 100 degree separation on the cams with the intake retarded. I have already tried advancing the exhaust with power loss. I had been thinking that retarding the intake may work better with boost. This would be used with the intake advance on. This would give roughly 110 degrees of lobe separation. Which is supposed to be good for blowers. I still think on paper that the exhaust advanced should be better.
So with the intake retarded on tooth it would be 46,O-46,C. With the advance on it would basically cancel out. As I right this I am starting to think that the timing is as good as it gets and that really just higher lift is the only thing that will help. I just do not know.

whipplem104 · #21 12-03-2011, 11:17 PM

I was thinking about it and it has to be 36 degrees btdc with the advance on. 36 degrees abdc close with advance off. With 28 degrees of advance that would be 8 degrees btdc open in the retarded position. That would give a 224 duration intake and a 223 exhaust with EO at 30 degrees bbdc and EC at 13 degrees aftdc. That would give 21 degrees overlap with no advance and 49 degrees with advance. I have seen a few different specs on advance degrees and cam timing. I also looked at shrick cams info and there cams are 240 and 252 durations. At 0-60-28-32 for IO-IC-E0-EC. And 0-60-59-32 for the 252 cam. These numbers make more sense. SO retarding the intake one tooth would put the intake at roughly 2 degrees atdc open at retard position and 26 degrees btdc advanced. And 46-18 IC respectively. This would allow for good exhaust charge clearing and lower overlap and good intake filling at the same time. Any feed back welcome.
The stock timing could also be 36-36 on the intake and then 8-8 with advance on. And 30-13 on the exhaust with 13 being after tdc. That would at least make a little sense with a little overlap with the advance on. But I know from experience that if you advance the intake cam 1 tooth that when the advance turns on, valves hit. So that does not jive with Shrick or the late opening. The exhaust is about right from what I looked at before at 30-13 if 13 is after tdc.

whipplem104 · #22 12-04-2011, 03:27 PM

Ok I am a dope. The Shrick timing is IO-IC at 0-60Ret and 28-32Adv. Center line 126 and 92. EO-EC is 59-32. Centerline 113. So I am going to go get a rough idea of stock timing today on a parts motor I have at the shop. I know that before when I moved the exhaust cam I advanced it to get rid of overlap. I ended up with a rough. 180-0 timing on the exhaust valves. I found some old notes from earlier this year. EO at 120 full at 240 and closed at OT. This would support the 30-13 numbers on the exhaust.

JayRash · #23 12-04-2011, 03:36 PM

I read alot abt cams today and I need ur help dude. If overlap increases scavenging and as such should help topend right? How come on na atleast cars retard cams at high rpm to make better top end. From my own experience I know u need to retard the vvt to make topend power.

Maybe I read more than I should and i ended up missing something. Help pls

whipplem104 · #24 12-04-2011, 04:53 PM

I am with you on the confusion. Mercedes has always said and actually run the camshaft this way. But if you read any info on cam specs for race cams they all have a lot of overlap and the saying goes the cam does not come in until high rpms. With all that overlap the motor looses low end torque. I think that a few things effect this though. High back pressure for one would make a high overlap cam bad in the top end. I also think that headers that scavenge the cylinder change a lot also. I am out of my actual knowledge range here but engines all breath the under the same principals. The thing that really gets me is that if stock cam timing is 30-36 degrees at IO and you turn the advance on and have IO at 0-8 degrees depending. That is only a few degrees of overlap and the m104 just flat stalls at that overlap. Look at specs on any normal cam and there is way more overlap than that. But maybe the short duration is a big factor. I am going to spend some time this week with a motor playing with timing. If you look at the Shrick cams then for a n/a motor you should retard the exhaust cam a whole tooth to increase overlap for the high end. But again the duration is so short on the stock cam.
It makes you think that there is a lot of power in the cams if done right.

whipplem104 · #25 12-04-2011, 07:14 PM

Supercharger tuning through cam selection and cam timing | Supercharger Performance and Engine Performance Parts

Here is a decent description of cam theory. So it is the advance that gives the low end torque. Not necessarily the overlap. The overlap helps it breath on the top end only if the back pressure in the exhaust is not to high. Makes me want to try and retarding my intake one tooth. I do not need the torque on the bottom end and maybe this would promote better filling on the top end. Cam advance on of course. The other option is advancing one tooth and leaving the advance off all the time. Would at least give me a good idea where to go.

whipplem104 · #26 12-05-2011, 06:22 PM

Well confirmed today the cam timing on the chart attached by MAG58 is correct. Found it in WIS agian and also did a rough check on a spare engine and it was pretty much right on. Thought of using the exhaust cam on the intake with no advance mech. Little longer duration on the exhaust cam. Or retarding the exhaust cam for some overlap. There is actually no overlap ever in the current setup. I am also going to look into regrinds on some cams since I have several extra sets.

MAG58 · #27 12-06-2011, 01:27 AM

Check the base circle on the exhaust cam, I believe that on a few engines I've heard of the exhaust base circle being smaller than the intake, which would lead to more gross lift, IF the HLA's have enough space to compensate.

whipplem104 · #28 12-06-2011, 09:36 AM

The base is smaller on the exhaust. It also has a shorter lobe. It is not much, like .1 or .2mm. But you are right the lifters need to absorb this. I was thinking of trying this. The duration is just a tad bit longer. I think I have heard that someone has done this before though.