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| Quicker Steering Ratio | |
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| Topic Started: Thu Aug 13, 2009 4:27 pm (200 Views) | |
| The Gorilla | Thu Aug 13, 2009 4:27 pm Post #1 |
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Hi, I have read a couple of threads on this and the suggestion by Matsellah76 on shortening the steering arms. One thread was looking at changing the pitman arm but there was no conclusion. The 16v steering ratio is approx 3.0 turns lock to lock. The steering on the Evo's is I believe approx 2.7 turns lock to lock. So merc either comissioned a quicker worm or screw what ever is in the box, rumaged through the parts bin, or made the Evo Pitman Arm, and its Idler Counterpart longer for the increase in ratio. So next question, are the Pitman arms and idler Arms same for a 16v and Evo or different, and if different, by how much in length. Back of a cig Packet calculation seems to suggest that if the Pitman and Idler arms were 20mm longer then the steering ratio of the 16v would be quicker by about 10/15% making it approx on par with the Evo. If you look at the DTM car pics posted by JM Motorsport you can see that the DTM Cars achieved this in a similar way by replacing the arm with longer Alloy V block with inset bearings. As the Pitman arm steering principal is ratio of Turns X Length of Arm then extending the arm and idler, will increase the turning ratio. The steering damper may need to be spaced out and its length altered slightly but it seems an easy way to increasing the steering ratio ? Much quicker than 2.7 / 2.5 for a road car is to much for most peoples liking. I'll put me flak jacket on now and wait for the ''incoming'' . Regards, The Gorilla. |
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| NEIL | Thu Aug 13, 2009 4:37 pm Post #2 |
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At the risk of sounding like a smartarse, I would suggest you buy the £7.5k Evolution currently languishing on eBay if only for the purposes of reverse-engineering... |
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| balamb37 | Thu Aug 13, 2009 6:47 pm Post #3 |
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| The Gorilla | Thu Aug 13, 2009 7:58 pm Post #4 |
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Hi, Neil- I did consider it, as its only 7k, but you still get the awful numb steering albeit its a little bit quicker at being awful and numb. No, I will stick to the idea of Rack and Pinion steering, like Merc fit now to most of the AMG Cars. Regards, The Gorilla. |
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| Chris Martens | Thu Aug 13, 2009 8:08 pm Post #5 |
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Danny, EVOs have the same steering gear as the standard (LHD!) valver with i=13.28 I think that Mercedes limited the steering angle (via longer stop bolts?) to 2.7 turns because auf the larger rims / tires.  Next, pitman arm. Extending the pitman arm (and the other one (idle arm?) of course) will give you more steering angle at the wheels for the same angle at the gearbox entrance. Shortening the steering arms will do the same (and should be easier to build I think). Steering arms and idle arm are all the same for W201 from 190D (LHD) up to the EVOs. Pitman arm is not available as a separate part but according to the Tabellenbuch Personenwagen they all have the same number 0115 for W201 LHD. Who can measure some steering arms / idle arms from other cars (W124, R129, W202) with similar front axle? regards, Christian |
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| The Gorilla | Fri Aug 14, 2009 7:59 am Post #6 |
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Hi, Chris Martens- Thank you for the information as it helps me understand what was behind the changes for Grp A / DTM. Would take us Primates ages to discover all thta data and information. The logic to doing the Pitman/idler arm as oppossed the steering arms is that with the Pitman /Idler, its one factor, ie] length. With the steering arms its 3, ie] length of arms, height of arms for steering bump, and shorter arms will alter the steering rake angle of the tie rods. My interest in this was for two reasons, was there a way to obtain Evo steering ratio, without breaking the bank, and was the std 16v steering able to be modified simply. When I get a chance I am going to alter the pitman/idler arms on the 16v test wagen here and see what it does. I am still going the Rack and Pinion route on the project car though. Regards, The Gorilla. |
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| JM Motorsport | Fri Aug 14, 2009 10:54 am Post #7 |
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Chris ive checked the EVO service manual, checked WIS and EPC, but i cant figure out what the differences are. 2.3-16v and early 2.5-16v have aluminium housings just like the EVOs, steering ratios are the same too and as you say pitman arm is the same for all LHD. |
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| Chris Martens | Fri Aug 14, 2009 11:28 am Post #8 |
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Danny, you're right, modifications of the steering geometry are a special task. Pitman arm is only one factor, length? Don't think so. If you extend the pitman arm, the tie rods have to be extended, inner pivot point will be different. This will change the geometry as well. If you change the design of the steering arm you may optimize the outer pivot of the tie rod for better bump steer in case the car is lowered. You may keep the rod length the same if you wish so (via steering arm curved invards) and still reduce the effective length of the arm in longitudinal direction. But if you want to go rack / pinion anyway I will stop arguing now.  regards, Christian |
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| Chris Martens | Fri Aug 14, 2009 11:31 am Post #9 |
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Mikael, there is a stop bolt at the knuckle, limiting the max. wheel angle. 2.3-16 and 2.5-16 have a part with a number A201... while EVO have A129... regards, Christian |
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| The Gorilla | Fri Aug 14, 2009 1:09 pm Post #10 |
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Hi, Chris Martens- Nah, us Primates do not argue we just debate matters !!!! I think there is a way to alter the Pitman/Idler and adjusting lengths without getting to far into Geo angles etc. Bump is better done with spacers on the connecting Pin or bolt at the Hub / tie rod so that it can remain adjustable to suit a cars ride height, if of course its ride height is adjustable as well. I think the effort for R & P should hopefully be worth it, would hate to be in front of them Gas Burners for the last time not knowing !!! Regards, The Gorilla. |
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| JM Motorsport | Sat Aug 15, 2009 7:54 am Post #11 |
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Hi Chris, yeah i have set of 129 steering knuckles in the garage, so basically there is not any differences between steering boxes. |
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| zoomer46 | Tue Sep 29, 2009 8:35 pm Post #12 |
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here is a link to a 190 with rack and pinion steering on the rev http://190rev.net/forums/showthread.php?t=28611&highlight=ls1 http://190rev.net/forums/showthread.php?t=321 http://190rev.net/forums/showthread.php?t=31996&highlight=steering and also similar threads to your own, i am class 1 on the rev btw... |
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