Expiremental OM617 build

[R-3350]

this is a cross post from STD for anyone interested in a high power OM617 and what goes into building one Hello i don't post a great deal here. however i have been working slowly on a project i have had in mind for a bit. i have a 85 300D w123 that i have been tinkering with for about a year now. my goal is around 300 HP with some reliability. i am aware that the easy way is to go with an OM606 however that has been done before. very few people have taken the 617 to its limit it seems and i enjoy a good challenge. i also enjoy designing my own systems and parts. So far i have maxed out the stock pump and re-timed the pump to 28* along with reamed and chamfered pre-chambers and increased the boost to ~14 pisg. i then got a new head and aggressively ported it till the port walls were around .150" as verified by ultrasound. the new head is waiting to go on till i can re-cut the valves and seats also need a tiny bit of port geometry smoothing still. all this is along with a HE221W i got and a W115 manifold thats on the way. also trying to find a shop that can calibrate AAZ two stage injectors with DN0SD315's. the long term plan is to get a compound turbo setup running a HE211W or HE200WG as the HP and either a HX35 or 40 as the LP. i am running a rigged water methanol system from the washer bottle right now and i am intending to replace that with a true high pressure injection system. also looking into getting a set of rods made for the engine but thats gonna cost a great deal so its far down the list. also investigating thermal barrier coating companies about the pistons and the pre-chambers. theres a great deal of other ideas too that i intent to explore. the max rpm capability of the engine is a question i am wondering about. considered buying a junkyard tired engine and pulling the high idle governor from the pump than running it in 500 rpm increases followed by compression tests to find the rapid degradation point or just see when the rods go for a walk. pictures to come as i can host them.

[R-3350]

i got the turbine housing discharge flange made by a local shop for me. its got a minimal amount of material blocking the exhaust flow and a 3" v-band outlet. kind of ridiculous but every bit less of restriction post turbo helps.


i also ceramic coated the exhaust manifold. mind you its not a high quality coating but everything helps, and i dont intend on keeping the EGR manifold for long. looking into using a W115 N/A exhaust manifold to feed a twin scroll housing on the HE221W (TD04HL housings fit the hot side of the 221 and there is a 8.5CM twin entry housing for them.)



it kind of amazes me that the HE221W can flow as much air as it can upwards of 36LBS/minute



in other news i am in the process of getting a quote from Pauter for a custom set of connecting rods. not going to need them any time soon but i just wanted to know how much it would be. they make a rod that is almost exactly the same as the 617 but the small end is ~1mm too small. Its for another Mercedes but i cant remember what off the top of my head right now. ill keep posting as more progress and pictures come.

[R-3350]

spent most of today wrestling with the engine. i managed to get the seized nuts off the manifolds to pull the stock turbo after soaking them in ATF mixed with MEK. (this is the best penetrant oil i have ever used it even beats the Boeing stuff i used to have that was banned in most states for toxicity) also i just love the nice residue the EGR leaves behind in everything it touches.



i also found the source of the slight rattle and drone at some speeds. guess i have no excuse now not to have a 3" DP made. i might even "forget" to re-install the exhaust past the DP for a bit just to see how it sounds with the HE221W and a strait pipe.



the next step is to mount the new turbo with the w115 manifold. i would like to get the new head on however it still needs some work before its ready. i did get new valve guides and the porting but it needs valve sealing work and a little smoothing.



i think i removed around half a kilo with all the porting. the port walls are quite thick somewhere around 10-13mm.



i got the w115 manifold in today. also i needed to replace my engine mounts so i got a new set an cast them full of rubber (PR seal if anyone is familiar with it. its horrible stuff its smell awful and gets everywhere but once cured its amazingly indestructible)

[R-3350]

i have been experimenting lately with designing a resonant tuned intake manifold styled after the w115 manifold but with better flow characteristics. the first step was to establish the resonant frequency of the valve acoustics at desired RPM. i chose to model the intake for 2800-3100 and 4000-4500 as two of the primary tuned harmonics. this should establish better airflow at cruse rpm (~3000 for me) and maximum HP which stock is 4350 but i figure i should be able to push that up to around 4500 with some governor tweaks. modeling the intake is two method approach as i am trying to figure out the Helmholtz resonance of the plenum as one volume and the runner resonance as another. so far i have established an ideal runner length of 18.91" (480.3mm) and a cross sectional area of 1.39"^2 (9.02cm^2). this is all rough estimation, however even if it is a bit off the 3rd and 4th order harmonics i am targeting should fall somewhere in the usable power band. based on these dimensions i started designing a manifold with the main goal being ease of construction and optimal air flow. i have access to a CNC mill so i intend to use it for one part of the manifold however most of it is basic aluminum sheet and tube stock.



the core of the manifold is a bar of 6061-T6 16" X 2.5" X 1.25" with a series of bell-mouths into the runners. this is the only part that needs special construction and you could probably get around that with ebay velocity stacks, some plate aluminum, and a tig welder.



i wont be building this manifold for a bit yet as i just got the w115 manifold on. however sometime in the future ill get around to it. once i finish modeling the airflow dynamics and have a good set of .DXF files i will post them somewhere for anyone who wants them. in other news i am waiting for the last parts to get the down-pipe together and some charge piping before i can get the 300D back on the road. i briefly ran it with nothing from the turbo back and its ridiculous. you can't make out the engine tone over the turbo whine above 3K rpm free revving it. i re-clocked it some after this picture to better situate the outlet and the oil drain.




here's how i adapted the drain line to the block not elegant but it works.

[R-3350]

i got the new 3" down pipe on today and finished plumbing in everything. then took the car for a test drive. sounds amazing however i noticed a strange hissing/scratching noise at idle when i got back. popped the hood didn't see anything revved the engine a little. promptly the alternator exploded and shorted the battery managed to get it unhooked fast enough to prevent serious damage but now i need to install a new alternator and redo the wiring harness. yay. i have a new AL129X and 1/0 cable coming soon so ill just redo the entire layout might try to get the battery in the trunk.

[R-3350]

the car has been doing well with the new turbo. it maxes out at 17 psi right now however it doesn't like to make more than 10 psi below 3000 RPM. i would like to drop that to 15 but as it is i think its leaking drive pressure from the WG due to reducing the WG spring pressure too much. i might try feeding it vacuum with a manual boost controller to feed pressure once the set point is reached. ill have to see if that helps. in other news i picked up a new short block to go with the head i have been doing a lot of work to.



the head has been ported as far as i am comfortable with for now. the short side radius on the stock ports is atrocious, also the intake runners decline into the valve while the exhaust is almost a direct 90 degree turn. i contemplated reshaping the chambers and valve reliefs to help reduce valve shrouding but without a flow bench and a few spare heads to play with thats a dangerous move.



i talked to Geoff at Colt cams about a bigger cam to go with the better head flow. He said they have a few profiles for the OM617 that are good for a little more flow without hurting the low down power, so ill be ordering one as soon as budget allows. he also was interested in creating something more extreme when i mentioned the ported head and the other work i have been doing. so maybe once this car is no longer a daily ill look into going a bit farther. i am currently tearing the short block down to see what needs replacing while also getting some ideas for other things to tinker with. something that interested me was the timing advance mechanism, according to the FSM the early models prior to 1980 have 8 degrees of advance while the later have 7.5. i am considering grinding the stops to allow another 1-2 degrees of advance. this should hopefully help increase the usable power band a bit as even if you tinker with the high idle governor it still falls on its face above 5K.

Sorry for the rambling i genuinely enjoy testing ideas and seeing what sticks. if anyone has had any similar ideas feel free to chip in im game.

[R-3350]

i have been taking dimensions from the engine i am taking apart and i figured i would post some for anyone interested. the rods are 149mm center to center, big end is 55.6mm, small end is 28mm ID in the bushing with the bare rod bore being 31.04mm. the big end width is 31.85mm, the small end is 28mm wide. the big end across the cap is 84.58mm wide with the chamfer into the big end bore 58.8mm, and the beam is 22.8 X 14mm in the center. the rod to stroke ratio works out at 1.611 to 1.

i am waiting for the quote i requested from Pauter to come back. they make a rod for the m121 engine (seeing that in their catalog was the mother of all non-sequitur) which is almost exactly the same except for the small end being 26mm ID. so hopefully they could just modify that design and it wont be too expensive. i am still expecting it to be in the range of 1800 for a set so not cheap, nor will i be getting them any time soon but its good to have the option on the table.

[R-3350]

i have been making good progress on dissembling, cleaning, and inspecting the new engine. i recently got a 6L ultrasonic cleaner and its fantastic at stripping the years of crud built up on all the parts.









i also finally got the parts to begin installing the water to air intercooler. i still need a few plumbing bits and a water pump but hopefully in the next few weeks it should be working.





one thing i have started working on is examining the timing advance mechanism and determining how to change the limits and the curve.



the round pucks of steel are the flyweights these ride on two hardened curved tracks in both the upper and lower housing. as the rotational speed increases the weights force outward rotating the outer housing which is keyed to the pump drive intermediate shaft relative to the lower housing with the chain sprocket. the springs fit into two holes in the housings and are retained by the half barrel pins which in turn are held captive by the vacuum pump cam plate. inside the springs are a set of rods these are the limit stops i removed the springs to compare the travel limits with and without the pins installed the housing can accommodate another .125" of rotational travel without contacting anything. i am still working out the pin length vs degrees of advance once i know this ill try to see if i can get it to around 10* total advance. the next step is to measure the spring rate and see if i can find something the same dimensions with a slightly lower rate to increase the timing advance rate.

[R-3350]

i have been having an issue lately with excessive smoking at idle. i did a valve adjustment and re tested the injectors to make sure they were not dripping also changed the glow plugs and inspected the pre-chambers. while i had the plugs out and the injectors i noticed that #1 seemed slightly wet with oil this combined with some slight residual pressure in the coolant expansion tank after sitting for a day confirmed my thoughts of a failed head gasket. it has been smoking for a while and getting steadily worse so i finally decided to pull the head and swap in the new head thats been ported along with the new cam. while i was pulling the head bolts i noticed a few were wet with oil on the threads but dry by the shank two were also covered in soot.





you can see there where it failed the #3 and 4 also had similar failures just not as bad.



the pistons are pristine with no visible erosion or anything. the bores are great too ~.004" wear step with cross hatching still clearly visible. i still need to surface the ported head and have a three angle valve job done. i have been holding off of doing that work until right before i put it on so as to limit the possibility of damage in storage or transport. while i had the old head off i set it next to the new ported one to show the difference. its quite dramatic especially in the exhaust ports.



i should have the new head on and running before too long. i already have the new gasket and bolts all i need to do is get the machine work done and spend a weekend working. ill be interested to see how much of a difference it will make in power without any fueling changes.

[R-3350]

i just recently got the car running again. as with all projects like this it became the death of a thousand paper cuts. i kept finding i needed another part or was missing something. the real kicker was i have multiples of almost every gasket on the engine as spares but i didn't have a timing chain tensioner gasket and it took a week to get one. the new head looked great after i got the modded pre-chambers in and the valves lapped and installed (new bronze guides valve seals rotocaps ect ect).








as for the car now, it has made a significant difference in its personality. all of a sudden the engine likes to rev before i had to give it a good bit of pedal in neutral to get it to rev fast. now about 1/2" of pedal makes it jump right to 2000. i haven't driven it enough to make any concrete observations on spool, egt, and off boost response. however i can say all are better.

the head porting was something i did a while ago while i still had access to the NDT equipment at the airport i was working at. i used an ultrasound inspection probe to gauge the port wall thickness. in some places it was over 1/2". i started by opening the throat of the ports to the edge of the gasket hole while also reducing the center divider wall to around .125" then i raised the roof of the port as much as possible to decrease the short side angle. i also opened the valve throat to around 87% of the valve face diameter while tear drop profiling the valve guide boss (theres not much there to profile but every little bit helps). finally i increased the short side radius as much as i could. all of this was interspersed with ultrasound inspections to prevent breaking through the port walls, the thinnest i went was .125"

i also ported the manifolds and turbo housings to match the ports on the head and optimize flow. the exhaust in particular needed a lot of attention as the stock egr manifold is not good it has lots of large nodules the interrupt flow. in particular the #1 port is very bad.







something i did while i was waiting for the tensioner gasket was to look at the coolant flow paths and how i could optimize it to help keep the head cooler. they can crack at higher output due to the inability of cast iron to dissipate heat like aluminum can. i noticed the stock thermostat housing half that bolts to the head is the outlet from the head and there are a lot of sharp corners in the flow path and plenty of excess material to remove to help it flow better. you cant see what i did as its not easy to get a shot of the work but if you get a chance to examine the flow path it becomes obvious what to do.



im also looking into removing the threaded plug at the back of the head to fit a hose to. then run a feed from that through a small aux radiator to an electric pump and back into the front most port on the side of the head. this should help keep the head cool during protracted high power output.


one final not to anyone interested in porting. its at your own risk. it would be quite easy to wreck a head by grinding too far and it's not going to get any easier to find good heads as time goes on. that being said if you are willing to take the risk and accept the responsibility go for it. it can really help these asthmatic engines behave more like a proper German engineered piece of machinery.

[R-3350]

its been a while since i have given any updates on the project. i haven't made much progress on the drive train side of the car lately as i am waiting on my pump to get back from dieselmeken. as for the rest of the car i have been doing a lot of modifications to the styling and repairing the inevitable rust i found at the same time. i found a great deal of rust on the passenger side behind the bumper cladding after i removed it i also found extensive sheet metal damage from an accident a long time ago that had been shoddily repaired so i took a long time welding and hammering out the entire rear of the car to get it right before re-spraying it. i also did a compression test and found the current engine is ok for a while yet which is partially why im putting off building the next one till i have more time and money to spare.









once i had finished the repair i also took the time to mount a w115 bumper and a set of w116 rear over riders as they both fit easily with little modification.





some other little things i have been working on are changing the interior lights to all led and updating the fixtures.




adding a new hood ornament also from a w115 along with the matching front bumper im still looking for a set of w116 over-riders to match the rear however they are hard to find in decent condition






on the engine side of things im working on building a new manifold out of Inconel 625 to feed the set of compounds ill be running in the future i got a pile of plate and filler wire for tig welding the tubes just haven't had a chance to get around to it as work has swamped me for the past few months.





to help make the car less deadly once i get the engine sorted out i got a set of s600 front calipers that ill be fitting once i go to larger front wheels the rotors are 320mmX30mm. i will be fabbing new spindle caliper mounts and tie rod mounting systems to both allow me to mount these beasts up and eliminate bump steer.



and finally the new engine for the car has been under the knife for a while receiving extensive modifications to the block and head. ill also be getting a set of custom forged rods from Pauter soon and a new custom cam that i am prototyping along with a full valve train upgrade (if it works i may end up selling it as a package along side head porting to anyone interested in pushing a 617 to 606 territory) i am working on a new dash system to replace the current second gen one im running im looking at going fully holographic heads up projection using an arduino based data logging system.

[R-3350]

here are the two sides of the w116 over-riders as they are now

[Coolvibes]

Hey R-3350, thanks for sharing. Nice project! I am interested to see how the engine runs when you get your IP back. I have a OM617 I am trying to put into a W110, but the accessories make the engine too long.

[Dan Stokes]

Interesting! You're WAY deeper into this than I am with my race engine but I have to be VERY budget conscious (read, cheap) on mine given limited funds in retirement. It'll be cool to see how all of this works out.

Where in NC are you? I noticed the plate in the one rear shot. I'm in Wilmington and it would be fun to get together and swap lies.

You might be interested in my side-mount engine stand adaptor. It works great and keeps from hanging the engine off that aluminum plate (probably OK but it worried me). If you get over this way I'll show you the mount adaptor - my spare engine is hanging on it as we speak.

Dan

[R-3350]

im in boone, if i visit the coast any time soon ill have to see if i can stop by we can trade stories. as for the engine block as it is it weighs nothing i can pick it up so im not too worried. i used that stand to rebuild a 6.9 idi engine a while ago for my truck all told that beast is 1400lbs so i doubt it will have an issue with the 617 plus im getting rid of the stock end plate to mount a new trans once the new pump comes in.