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+--- Thread: Mercedes w123 om606 (/showthread.php?tid=5960)
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RE: Mercedes w123 om606 - soltysrsz - 10-30-2016
(10-23-2016, 09:52 AM)R-3350 the HY40U is a HX40 with a smaller hot side. in the throat feeding into the turbine there should be a number stamped or cast what is it? that turbo will probably work but it might be a bit small for compounding at least if you want to run smoke free at WOT. the HX30 super is kinda rare i haven't heard of people pulling them off of anything. i would message Alcaid about getting one he sells factory new Holsets.
now for the fun math. at 120cc/1000 it works out to 0.102g per injection event. to run smoke free and low EGT this means you would need 1.836g of air in the cylinder in order to burn the fuel cleanly at an AFR of 18:1. an om 606 has 499.3 cc per cylinder with air being 1.29mg per cc at STP this works out to 0.64414g of air in the cylinder with no boost. this means you need a density ratio of 2.85:1 in order to supply the air. this is of course assuming 100% VE and a variety of other variable im not factoring. to get the 2.85 density ratio assuming decent intercooling of around 80% you need 31.5PSIG boost however there is the restriction of the head, intercooler, plumbing, and air filter to work around so lets just say 35 ish psi (or 2.4 bar) should do ok. the next issue is the turbo sizing im not entirely sure of the flow capabilities of the HX/HY40 however the above calculation requires ~60lb/minute at 6000 rpm running 2.4 bar while the 40 could do this i suspect not at the low pressure ratio it would see in compounds. this is similar to the size im currently looking into at least in regards to mass flow vs pressure ratio requirements. i might look into a Borg Warner S300SX-E series for your LP turbo it handles more air at a lower PR than most Holsets can at that same PR. also remember with compounds its quite easy to simply increase the boost to feed more air. at least if you size the turbos with a bit of head room. for example with both turbos running a PR of 2.0 it multiplies the stages so you get a PR of 4.0 or 44lbs of boost. the issue is the mass flow you're trying to pull a lot of air through the LP turbo at low pressure most turbos don't like that so you have to size carefully.
anyways feel free to cross check my calculations. im not as familiar with the 60X engines and by no means assume i didn't make any mistakes. good luck on your build it cool to see a good w123 getting a new heart and more pep.
Thanks for your advice. Now i'm looking hx30, but it is hard to find, what about hx27?? It would be good?? How can i match which turbo will be suitable to my setup?
RE: Mercedes w123 om606 - atypicalguy - 10-31-2016
It is a complex calculation because the small turbo is not at standard temp and pressure at its intake. So it's map needs to be corrected for those conditions, which change with boost supplied from large turbo.
The above comments are useful if the system is to run only in compound all the time. Most setups do not do this however. They just use a little turbo to spool quickly and light the large turbo. The small turbo wastegate is opened by large turbo boost. So as the large turbo comes on line, the small turbo does less work, which is good because its intake air gets quite hot, so you don't want it spinning very fast or its compressor will fly apart.
I have an he451 (non VGT) and it marches right up the middle of the map as a single at 120cc and 17:1. So I plan to run it sequentially. Maxes at 80 lb/min. I was hoping to run 150cc, but that takes 65psi of boost. Need new head gasket etc.
RE: Mercedes w123 om606 - R-3350 - 10-31-2016
the sequential setups seem to work poorly if at all in most instances without very careful waste-gating and control. i read through the thread you referenced and it seems the tactic they are using is to shift the pressure ratio split more towards the large turbo but the small is still contributing a decent bit. Kjewer1 showed in his data logs the at the peak he was running around 3:1 pr on the LP and 1.5:1 on the HP with the hp starting higher and decreasing as the lp came on line.
the HX30 super and the HE221W both maintain a decent position on their maps being fed as a HP in a compound set up at least for the 617 and probably the 606. as an example i plotted the discharge temperature and pressure of a S300SX-E S363 as my LP in the set up im intending to run. at a discharge PR of 2.39 @ 5k rpm its flowing an input of 299 cfm and 21.39lb/min mass flow with a discharge temperature of 162* C this is @ 68% comp efficiency as its running near the surge line. note this is all as a single. now if you correct the air flow for the density ratio of 1.67:1 its flowing 179.042 cfm of air you have to correct for temperature expansion and the associated reduction in density. inputting the air conditions at discharge gets a air mass of 0.119497147lbs/ft^3. now the difficult part is finding a semi reliable compressor map for either the 221 or the 30 as Holset is rather tight lipped with them. best i can tell there seems to be at least one ok map for the 221 that Alcaid posted a while back. plotting this shows the 221 is capable of up to 37lb/min @ a PR of 2.95:1 with very forgiving choke and surge lines. the down side is the peak compressor efficiency is around 72%. i continued to plot this set up at 5 separate points across the rpm and PR range and it works out good as long as you dont bring the lp above a PR of 1.5:1 below 2000 rpm. above 2500 its ok to hold it to 2.2:1 and past 3000 it no longer cares. @ 5k and 45psig the 221 is effectively flowing 32lb/min with an even 2:2 PR split if i were going farther i would want a larger HP turbo however due to the runner size in the head of the 617 this is near the sonic choke point so @ which the PR to mass flow become very non linear.