legacycentral bbs

I'm waiting in anticipation! Good work, Douglas!
Would you recommend new pistons, rings, and various internals before applying the SC to my NA engine?
I'm having a friend of mine look into getting me an SC from somewhere, as he's a Mercedes junkie.

OK. The stepper pulley is a confirmed nightmare and I think the sixty or so hours I have spent with it trying to get it to work are all completely out the window. Plain and simple the pulley failed again. My fault again, but not as much as the first time. The aluminum pulley inner ring pulled in toward the bolts attaching it to the section of stock power steering pump that I had cut out and mounted. OK, you are all going, “what the hell is he talking about?”, but it doesn’t matter, the damn thing failed. I sheared one bolt and other crap broke, and I was lucky it happened while I was going 20 miles an hour while next to a parking lot.

So……I reinstalled the original setup and I love it once again. And I realized a very important fact. Spend the freaking $250-$300 and just have a larger crank pulley made and instant boost increase. I hate to think how much I lost my doing all the work myself instead of making money (ok, about $1000 in lost labor I could have made working for someone else). So I seriously screw up time and money wise. I did learn a lot about making pulleys though!

What it comes down to is keeping just one belt running the whole shebang, the proper pulley ratio, and belt coverage of the pulleys. Right now I have poor belt coverage of the pulleys and still manage a constant ( now that I repositioned an idler) 8 psi. Had I had this and no boost leak the first time, I would never had attempted the damn stepper pulley. If I move the current idler pulley, I will get MUCH better belt coverage and a possible psi increase just from that. And if I spend the extra money to just have the crank pulley size increase, I will see the 10 psi finally with no horror stories.

Aren’t you glad this isn’t you?

Good news in the end though, is that now that I have reinstalled everything AGAIN, my boost is even higher for some reason (probably belt tension) and I am getting a solid 8 psi, and this is very satisfactory. Not 100% satisfactory, but close.

Night all.

Some more musings.

All psi numbers are based on the numbers I am getting through a 90-94 AWIC into a 2.2 engine.

The m62, if it runs at 2 to 1 pulley ratio, on a 2.2 liter engine, utilizing an intercooler of some sort, starts pushing 6 psi at 2000 rpm, and rises to 9 psi at 6000 rpm. The supercharger is actually designed to run at almost 2.5 to 1 (about 14-15000 rpm to a 6000 engine rpm) which would give a boost increase of about 2-3 psi (so 8-9 psi at 2000 rpm and end with 11-12 psi at 6000 rpm. To accomplish the 2-1 ratio without a stepper pulley the engine requires a 7.25" crank pulley. To accomplish the 2.5-1 ratio without a stepper pulley, the crank pulley must be 9" in diameter. This may sound outragous, but a well turned and balanced aluminium crank pulley causes no problems. Its just exspensive.

Now if you were to do the same thing on a 2.5 liter engine, the boost levels will decrease because the engine is swallowing more air per revolution so expect a decrease of about 1 psi on average. This is probably a good thing considering how the RS 2.5 engines dont like excessive boost. On the otherhand, to a much bigger shit eating grin would be sticking this blower on a WRX 2.0 liter motor, you could expect up to a 1.5 psi increase overall. This could give you a 10-14 psi range, with no turbo lag.

The next step though would be to upgrade the m62 to the m90, which flows 1.5 times as much air per revolution! This would be a HUGE psi boost Since I dont understand the mathimatical formulas for figuring boost I can't give accurate numbers, but I am willing to bet it is a close to 50% increase in boost, so minimum 9 psi to start with at 2000 rpm, to 18 psi at 6000 rpm on a 2.2 liter motor! Huge! This could be as much as 21 psi on a 2.0 WRX block. WoW!

The first pitfall to fitting in a m90 is mechanical. Could you fit the m62 mercedes clutch system to a m90? Don't know but because of space requirements, it is most probably needed. The second pitfall is pulley style. Currenty we use a serpintine 5-6 rib belt. In the right pulley set up and the right belt manufacturer (I prefer Dayco PolyCog), this belt style will hold up to supposedly 12ish psi. If you want to go higher you need a cogged belt which would require some very exspensive custom pulleys.

When you get to the higher numbers, you will start running into a few problems if you are using the electric clutch. The biggest for belt life, drivetrain life and internal life is pure shock load. 0 to 12 psi is a hell of a boost shock. As it is, turning on the boost at 5000 rpm (which gives me about 7-8 psi) the torque hit is hard, meaning you wonder how long stuff is going to last. If you can always start boosting at 2-3k, then stuff will last alot longer. However it really isnt all that fun... On at least a few Mercedes supercharger systems, this shock load is prevented by keeping the supercharger from engaging if the rpms are higher than somewhere in the 3000-4000 range. Now if you somehow mount the Eaton supercharger without the electric clutch, so it is running all the time and you are utilizing the bypass valve, then you would be able to evade this type of engagement shock.

So there are my musings.

Belt wrap and new idler pulley results.

Ok, the original set up was four pullies and one belt. The stock alternator pulley, the stock crank pulley, , the powersteering pulley and the supercharger pulley. I installed one idler pulley. This was without a AWIC and gave me about 3-4 psi. The power steering still worked ok.

The next set involved the custom 7.25" crank pulley, a larger (for matching ratio) alternator pulley, the powersteering pulley and the supercharger pulley. I had the old idler pulley and an extra idler pulley to stretch the belt out since when you get this long a run, belt lengths are limited. Without the AWIC I pushed 12 psi. I detonated horribly and blew a piston. I also did not have any fuel management or upgrade fuel flow. I do not know what was the main cause of the detonation but you do the math. The powersteering pulley barely works.

The setup I have been running since installing the AWIC was the same pulleys but now no powersteering. I was running between 5 and 9 psi, depending upon a few variables I could never determine.

But now.....And maybe for a while..... I finally gave up and accepted that the stepper pulley for boosting psi by boosting the rpm pulley ratio is a damn hard idea to implement. So now my latest effort went into installing another true idler pulley which really makes the belt serpentine and better wrap the two pullies that count, the crank and supercharger pullies.

And it gave me positive results, the first in a while. While my psi didnt climb (which I kinda hoped for), it now really remains steady AND climbs in relationship to the rising rpms. This gives me a very potent and increasing power range as I drive. Boost starts at 6 psi and tops out at about 9ish while at 6000 rpm which is where I shift. I am currently running a 2-1 pulley ratio. If I, and I probably will down the road, spend another $325, I will have another custom crank pulley made so I can up the pulley ratio to 2.5 to 1. This would give up to another 2 psi.

At this point I am going to stay the way I am. The car is plenty fast and is running well. I suspect I will Dyno run the wagon some time withen the next 30 days.

Now off to evade capture from the police!