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I am helping a lemons team run a few chump races this year. For my consulting i get a seat in return, although it seems to be costing me almost as much as renting. If anyone else wants some top level tech advice in exchange for seat time let me know.

 

Anyway the car is a 98 mercedes slk 230. The ecu is a nightmare. Throttle by wire, electronically clutched supercharger with electronic bypass valve and traction\stability control "vectoring" which tries to stop all skidding. 

 

They have welded the diff shut (it was open) and i have almost got them to give up on the idea of the abs ever working, because it has been hell trying to divorce the throttle cut stability crap out. The car literally turns off for 1-2 secs when the wheels slip. I have pulled a wheel speed sensor to disable abs\stability\tc and the car is actually a decent natural driving car, so it might just stay that way. Their biggest nightmare is the ecu going into limp mode and opening the recirc valve all the time (no boost). This happens regularly and we have only been able to fix it with full bootstrapping of the pcm (full reset). This works for about an hour and a half, then something gets hot and upset turning on limp mode. We get a maf code (airflow fault) but can never really trace it to a sensor. I have locked the supercharger pulley solid and wired the clutch in to look like it is there (in testing the clutch didn't last long....)

 

This is also a 500 point vpi car with zero mods....add that to the pile....

 

I am leaning towards a stand alone ecu, but to get throttle by wire ecus we are talking 1,400 dollars. I am going to lobby for an equal to stock sized manual throttle body as a zero point engine control item. I could also maybe weld an arm on the stock butterfly, but i really hate hacking up safety stuff like throttle, brake or steering...

 

The blower is before the throttle, so i either need to move the throttle to before the blower or use a recirc\blow off valve. I can try to control the stock one, but yet again what a nightmare. I am going to see if tech will consider blow off valves as engine controls (open) or if i am forced to get an ecu capable of running the stock one (assuming i can figure out the pin out). 

 

They have tried the "reflash, i know a guy" path and the car is still a disaster, so i am leery of that path ever panning out. Maybe if i control the recirc valve on my own...

 

What do you guys think? Open to suggestions on what to do. The car is pretty decent when it runs, i could get it to the 1:46 mark at clt with only a few laps before the blower quit on me. 

Edited by Black Magic
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Chopping up the stock throttle body should be straight forward/safe, but even with a dummy unit plugged in, it will likely increase the limp triggering.

 

Borderline call on the BOV, you prob could get away with 0pts for aftermarket control of the stock unit.

 

I have a super simple on the fly mod to our (relatively stupid, standalone) ABS for when it faults from magnetic track debris or a bent wheel, not likely to work on a complicated system.

 

Any chance you can buy/learn the software to change it as it should work rather then default all the time?

 

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I had thought about window switch to control recirc valve, but it is pwm control and i am not sure if i can just give it steady 12v and not blow it up. I still hate having to hack such a vital part when mechanical systems are bulletproof and cheap..

 

If that works i can cross my fingers limp mode doesnt have a crap fuel and spark trim....

 

Thanks for the help. Keep it coming.

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Was it doing the limp mode thing before you locked the supercharger clutch?  What have the codes been coming up as specifically?  That could help point you in the right direction.  There could be something actually wrong that even a street car would run into.  I've had bad MAF sensors that the ECU would forget about every time I'd let the car sit over night.  All the codes would clear, and after a little bit of driving the next day they'd come back.  Not really a limp mode scenario, but just a thought.

 

Worst case, I bet a clever person could figure out how to make a Megasquirt run it all.  And I would argue going to a mechanical throttle, even modifying the stock one, is every bit as safe as a DBW if not more so as long as you don't just totally screw the linkage up.

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Press the ESP disable button on the dash ... :)

 

I took my son's '99 C280 Sport to the local track and it was quite good despite the garbage tires that were on it. The handling was predictable and fun, lots of power-on sliding with the ESP shut off.

 

There are quite a few helpful and knowledgeable people on the MB forums.

Edited by mender
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Thanks, i will look and see if they have an esp input. There are differences between the r170 and r171 that might include esp control buttons. Only the older r170 is champ 500 point legal.

 

The mb site has been some help, and i can see they struggle with the engine management as well. The cars eat $400 maf sensors and the no boost fault seems to be the response to nearly every check engine fault. We had a mb guy reflash the pcm to remove sensor faults, and he clearly didn't get them all.

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Pretty sure all MBs with ESP or ASD had a switch. I assume that the dash/console is gone? If so a cooperative dealership should be able to get you the ECU pinout and mode of operation of the switch (ground, voltage) but from the sound of it you/they should get something like this:

https://www.ebay.com/itm/MERCEDES-BENZ-ALL-MODELS-SERVICE-REPAIR-WORKSHOP-MANUAL-FACTORY-DVD-CD-GUIDE/121912282486?_trkparms=aid%3D222007%26algo%3DSIM.MBE%26ao%3D2%26asc%3D50998%26meid%3D9738dbcee9044ae483edcc2908efc5d4%26pid%3D100623%26rk%3D5%26rkt%3D6%26mehot%3Dag%26sd%3D171841662806%26itm%3D121912282486&_trksid=p2047675.c100623.m-1

 

I have one and it was a little awkward to set-up (Virtual Box) but has all the factory info with parts numbers and diagnostics. I worked at an MB dealership for a year as shop foreman in 2002-2003 and I went through a rather exhaustive investigation of the ESP function on a '98 E320 4matic. Actually a pretty robust system.

 

P.S. When I started at the dealership our techs were shortcutting the diagnostic steps and going straight to MAF replacement. MB clamped down on that by requiring the "faulty" MAFs to be returned to the warranty dept for further checking and a checklist that had to be filled out with actual numbers before the techs would get paid. It was easy to see fuel trims out by x%, replace the MAF in 15 minutes and claim 2.6 hours diagnostic and repair.

Edited by mender
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3 hours ago, Huggy said:

Most MB of that era, the switch does not fully disable the ESP/BAS.  The only way to disable it was to unplug the ABS fuse in my W202.  Not a good racecar solution.

True but it does get rid of the DBW interference which seemed to be their main concern.

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47 minutes ago, Black Magic said:

Shifting gears so to say... What are the reasonable ecu options out there than can do a good job with throttle by wire? Aem infinity, halteck ultimate 1500, motec m400, newer link, holley dominator...

 

Anything else i am missing, especially less than $1400

Would one of the myriad Megasquirt options maybe do it? I've seen people claim they've done it, but never actually dug into any of them.

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Not that I'm promoting hacking up the factory set-up, but it doesn't look like it would be terribly difficult or sketchy.  Pull the idler gear off, weld a mount for a cable end on to the gear, fab a little bracket for the cable mount, couple extra return springs, fab up something for the pedal end and there you go.  Easier said than done, but it surely can't be that hard.  Real question is if you'd be charged points for the hack or if Phil and Mike will let you swap to some other non-DBW throttle body of the same size for free.

 

 

Related image

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On 4/23/2018 at 11:36 AM, Black Magic said:

I am leaning towards a stand alone ecu, but to get throttle by wire ecus we are talking 1,400 dollars. I am going to lobby for an equal to stock sized manual throttle body as a zero point engine control item. I could also maybe weld an arm on the stock butterfly, but i really hate hacking up safety stuff like throttle, brake or steering..

 

Tech has allowed us to swap same size throttle bodies from drive by wire to drive by cable for zero points...  its allowed due to its interaction with the chosen zero point ecu swap.

 

Not 100% sure where you would want to blow off valve, but anything before the throttle body is free / open...  (that used to sort of be in the rules, but is no longer there)  I would assume however you can use a boost controller and required sensors / devices as part of your ECU swap.

Edited by Xph
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14 hours ago, Xph said:

 

Tech has allowed us to swap same size throttle bodies from drive by wire to drive by cable for zero points...  its allowed due to its interaction with the chosen zero point ecu swap.

 

Not 100% sure where you would want to blow off valve, but anything before the throttle body is free / open...  (that used to sort of be in the rules, but is no longer there)  I would assume however you can use a boost controller and required sensors / devices as part of your ECU swap.

 

Awesome advice. Thank you.

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  • 3 years later...

HI My friends and I are building a 1999 SLK 230. We have not completed it yet and have some questions if anyone can help.

 

I know this is an old topic but was there any resolution to solving the Limp mode problem? I am now worried we may run into the same problem. I have done some research about defeating the ASR on the car while leaving the ABS on. I'm not sure it will even work. If there is some good work around for this problem please share. 

 

Also I have other questions, but if anyone out there has any experience with these SLK's please reach out. 

 

Thanks, Doug

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Just now, Fastfrog said:

HI My friends and I are building a 1999 SLK 230. We have not completed it yet and have some questions if anyone can help.

 

I know this is an old topic but was there any resolution to solving the Limp mode problem? I am now worried we may run into the same problem. I have done some research about defeating the ASR on the car while leaving the ABS on. I'm not sure it will even work. If there is some good work around for this problem please share. 

 

Also I have other questions, but if anyone out there has any experience with these SLK's please reach out. 

 

Thanks, Doug

 

@Black Magic

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On 2/25/2022 at 1:52 PM, Fastfrog said:

HI My friends and I are building a 1999 SLK 230. We have not completed it yet and have some questions if anyone can help.

 

I know this is an old topic but was there any resolution to solving the Limp mode problem? I am now worried we may run into the same problem. I have done some research about defeating the ASR on the car while leaving the ABS on. I'm not sure it will even work. If there is some good work around for this problem please share. 

 

Also I have other questions, but if anyone out there has any experience with these SLK's please reach out. 

 

Thanks, Doug

 

Doug we run a 98 230 SLK. We have been running the car a handful of years and can offer some help......

 

Your options are to pull a wheelspeed sensor and run the car without ASR and ABS or go aftermarket ECU. We ended up going with a haltech and retained the ABS system (not wired thru ECU)

 

You will most likely need to weld the diff shut to make it driveable on track. We never tried ASR with the welded diff, but maybe that would fix it until the ECU stopped your fun 2 hours into the race....

 

The car will limp mode and cut the boost if run hard long. With the supercharger clutched and the wastegate electronically controlled the ECU has lots of authority to ignore you. We tried thru bolting the pulley and swapping to a manual blowoff valve, but it would eventually go fully limp as it assumed the ecu lost control of the electronic throttle. 

 

Another option would be to lobby for the SLKK 320 to take the same 500 point value as it's identical brother\cousin the crossfire. We are thinking of doing this anyway. You would pull the 190ish hp engine for 215 hp and need to swap to the correct 320 SLK trans and diff, but the rest of the r170 post facelift and pre facelift stuff should be the same. I think with an NA engine you would do far better fuel burn and might have low enough complexity to run on the stock ECU. We would just use the same haltech on the new swap . 

 

If you stay 2.3 supercharged the engines are very reliable. The blowers will not live at boost beyond the stock pully. You will last much longer if you clean up the intake tract and port the blower, both of which get the blower out temps lower (hopefully below 300 F). Once we paid to swap to the haltech, kept the boost stock, bolted the blower clutch solid, ported the blower and stopped hitting things the car has been very reliable, fairly fast and parts are very cheap to get for a good quality German car. Power is decent, fuel burn is not great and large tracks could be a challenge. The V6 NA would help here, so would not running 11.5:1 afr.  We maintain very little on the car beyond brakes and oil changes. Also the "SRT6" and "AMG" stuff can swap on, giving more options for brakes and springs if you want easy bolt on upgrades. 

 

The 5 speed trans will fail 3rd gear if you are the lift\stab sort of driver. The circlip holding it on gets beat if you slam the lash in and out of the gearbox and don't drive smooth. We got 3 or so weekends to a gearbox, they cost $500 to 800. We then tuned the motor better and stopped stabbing the gas like morons and have gone 2 seasons on the same trans. 

 

Not the answer you wanna year, but pay for an aftermarket ecu and clean up the wiring. The rest of the car can be good and low maintenance , think V6 car if you want better speed. We use corvette wheels on wheel spacers (cheap, $150 a wheel) and using rs4s with a few races on them can turn 1:48xx at CMP. 

 

Drew

Edited by Black Magic
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28 minutes ago, Todd K said:

Sounds like possible swap candidate for Harbor Freight v-twin and call it a day........ or seems like a lot of challenges no matter how you slice it.

Some of the best cars in the series are built from platforms that had a crappy stock motor (and often corresponding low VPI)

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Hi, thanks for the info. Looks like not to many options for us at the moment. We have a good running 2.3 SC engine. We don't plan to change to the V6. I looked up the car and now 475 points correct? 

 

I didn't want to get into stand alone ECU's as we had that on another car and I was just tuning it all the time. It was no fun. We did have the security system removed from the ECU so we could eliminate all the potential security errors. No plans to put a different SC pulley on. I was trying to keep the engine as stock as possible to avoid weird problems. ABS is not necessary so I'm looking at defeating the ABS ASR systems. I read someplace that pulling the ABS lowers the rev limit to 5500. Is that true? Did you guys ever LOG any data and see what was causing the limp mode? Temperature, over speed? Thanks for the info on the trans. I think I will look for a spare now. With 4 different drivers no idea what's going to happen.  

 

Doug

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17 hours ago, Fastfrog said:

@Black MagicI guess one more thing. If we were to go Haltech, would you be willing to share setup and files? I don't want to do this but if I have no other choice. Please let me know. 

 

Thanks for all the info.

 

I will double check with the owner, but I am 99% sure that would not be a problem. We run different injectors (added room incase we needed more) and if you use our tune you may need to copy our injectors, mods on porting the blower and building a better intake to the SC (or scale the maps). The tune we have is decent, I think it is excessively rich in some spots and some on\off throttle richness. That said we have never had an ecu\tune issue take us down, the only motor failures we experienced were oil starvation (big leak in a 24 hour race where you cannot open the hood on pit road, ran motor dry) and I worked on leaning the engine out and adding timing (burned exhaust valves). We made 180 something wheel hp with this setup, car should weight in the 2400-2500 lbs range with fuel. Because of the blower it burns fuel like a 200 wheel hp car.

 

Point value is 475 or 490 if you claim the later car. Both have the same power, engines are same family with variations on parts (newer engine has better head I think, worst blower) but the 490 value would allow you to claim the larger fuel capacity of 16 gal (you would get 18 gal under the +2 rule). 

 

There are alot of ecu options. We used a haltech elite 1500 because it supports drive by wire, which the SLK has. You could remove this with a manual throttle body and run all kinds of ecu's, we just chose to keep the entire car stock. You will be looking at a little over 2k to get ecu, harness and little bits to do it yourself. If you know something else better I think any ecu could do the job. 

 

We do not use electronic control of the recirculation valve. We just got a OEM mitzu evo blow off valve and hooked it to a vacuum line off the throttle. 

 

We didn't have a logger on the car when it would limp, but I think the fact the stock blower out temps are enough to heat the rotors in the supercharger to the point they seize has something to do with it. I bet it is some sort of thermal protection off the air temp sensor. You could power cycle the car enough that it would eventually get stuck in the "send it" mode and you got full power again. This was the car on the stock ecu, welded diff, one wheel speed wire pulled and big wheels from vette on it. Otherwise totally stock. First part of the video you see me power cycling the key, later in the video I get it cycled to the point it won't limp.

 

 

If you want a shop to do this for you steven at mass acceleration in Denver NC did the ecu install and tuning. More than 2k, but the owner was able to drop car off, pick it up and go race. You will lose 1200-1500 dollars for every race you enter and the car can't run, for perspective.

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