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1978 280SLC, 5 speed, no electrics, no AC, pure 107.
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Discussion Starter #1
I'm sure that there are a few of you out there that think taking an SLC on the racetrack is sacrilege, but I regularly thrash my old beast in Classic Racing.

This week I finally installed a proper racing seat and harness. It has been a long time coming and it sure feels MUCH more secure cornering. I have a race event this coming weekend so I thought it would be a good time to get it all sorted.

The SLC surprises quite a few people on the track with its capability for such an inappropriate car and each time I take it to the track I drop my times a bit. It's a really good way to learn exactly what the car is capable of. The car is still far better than I am. :)

One of these days I will try and put together a video of some in-car stuff that I have recorded over the years.
 

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1978 280SLC, 5 speed, no electrics, no AC, pure 107.
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53 Posts
Discussion Starter #3
ohh nice :)

Have you done anything to the engine or have you just stripped it abit to lower the weight
The engine was rebuilt about 10 years ago and is standard internally. I have just opened up the air flow in and out - replaced the stock air filter with a pod and the exhaust with a 2.25" single straight through system. It takes off when it hits about 4000 rpm and makes an absolutely glorious howl right through to the limiter at 6650.

Medium term plan is to do a bit of head work on the M110 and potentially a Megasquirt EFI conversion. The K-Jet is super reliable and tough, but the scope for playing isn't really built in. The theory is that a fully mapped FI/ignition system will give the old beast a bit more usable torque and hopefully rev a little higher at the top end.

I've also converted it to manual gearbox (Getrag GL275 from a G-wagen..), and tinkered with the suspension and wheel alignment. I have some proper race tyres that I use at the track and I am still getting used to pushing them. They are VERY different to road tyres - I just need the courage to find their limit. :)

As far as lightening goes, I use the car as my daily driver, so any lightening is temporary - the back seats are a 5 minute job to get out and I just make sure I have no toolboxes or luggage in the back! The handling is quite different without the spare wheel in the back as well - so that gets ditched too.

Basically it is primarily a road car that sees that track every so often - not the other way around.
 

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Always Remembered RIP
1973 450 SLC AMG, 1995 Chevy Tahoe
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3,381 Posts
What tracks have you raced? at and what classes? What are the car restriction? etc.
 

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1978 280slc
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3,198 Posts
That kicks ass! I'd love to hear about you top end plans for the engine also, the sweet 6 loves to rev. That is cool and keep up the good work!
 

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1978 280SLC, 5 speed, no electrics, no AC, pure 107.
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53 Posts
Discussion Starter #7
The right hand vent has been replaced with a vacuum gauge. It serves a few purposes - when pottering around it is an economy gauge, when giving it heaps it shows when vacuum is dropping (no more power for the engine to give), and it is a good indicator of general engine condition and tune.

As far as tracks I have raced - I have only been on Manfield Park here in NZ. It is about 3 km (about 2 miles in old fashioned US speak..), and is often considered the most challenging NZ circuit with lots of corners and pretty aggressive camber. I lap at about 1:34 where the single seaters do it in about 1:10, so the SLC isn't fast, but it is challenging.

I have also competed in quite a few club sport events - hillclimbs, tarmac sprints and autocross. Below is a photo after a particularly muddy autocross event. Seriously good fun getting the old beast VERY sideways on a dirt track!

:)
 

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450SLC
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ROFL looks great covered in mud :) I have to get my car down to a track at some time to see how well it performs with the MSII controlling it on a track. I finaly bit the bullet and tuned my advance controlled by the ECU.. on cruise its like 50degrees advance with a AFR of 18.5-19 rofl.

But back to your car, a aftermarket ECU like MSII is the BEST thing you could do to your engine, i would say a 10% increase in power, better fuel economy and best of all sets it up to handle any later modification you would want to do. :)
 

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Always Remembered RIP
1973 450 SLC AMG, 1995 Chevy Tahoe
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3,381 Posts
I have also competed in quite a few club sport events - hill climbs, tarmac sprints and auto cross. Below is a photo after a particularly muddy auto cross event. Seriously good fun getting the old beast VERY sideways on a dirt track!

:)
:mad:I'm jealous
 

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'09 E350 4-matic sport, '83 240D 4-speed (sold), '77/'78 450SLC (junked), '81 500SLC (junked)
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845 Posts
Sweet! I might have a set of comfy recaros with matching door panels and rear seat up for grabs soon... ;)
 

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1974 450SLC and 1973 350SLC
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[/QUOTE]ROFL looks great covered in mud I have to get my car down to a track at some time to see how well it performs with the MSII controlling it on a track. I finaly bit the bullet and tuned my advance controlled by the ECU.. on cruise its like 50degrees advance with a AFR of 18.5-19 rofl.
But back to your car, a aftermarket ECU like MSII is the BEST thing you could do to your engine, i would say a 10% increase in power, better fuel economy and best of all sets it up to handle any later modification you would want to do. :)[/QUOTE]

wow my car with megasquirt does not like that lean at allll...I changed my AFR targets for the EGO to 14.1 and 13.7 ...you should try it ...not as good economy but it likes gas..much easier for it to mantiain the VE tables more toward the required setting..But i did use the yellow injectors from my '73 350 SLC which flowed at 340cc compared to the blue ones at 480 cc .Jeff
 

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1974 450SLC and 1973 350SLC
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162 Posts
Yes stock Dist.and using the ignition from the extra code 29Y...Now in the EGO settings page if you have 255 set then your not using the targets...its actually off..and with MSII like your running are you using this> Jeff

There is an adaptive learning algorithm called "Automatic Mixture Control" mode in the MegaSquirt-II code (V2.6+). It updates your VE table while you drive based on when you are at a stable vertex in the VE table and averages your ego correction. If it stays in this state long enough the VE table will automatically be updated, so the ego correction should quickly drop to 0. On a schedule which you can determine it will update the VE in flash - you can set this to be fairly frequent when the car is first being tuned, then set it to very seldom or never.
 

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1978 280SLC, 5 speed, no electrics, no AC, pure 107.
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53 Posts
Discussion Starter #14
So, the SLC and I survived a good old thrashing at the race track on Sunday.. :)

Pics are still to come once I get them off one of my friends (kind of hard to take pics of yourself driving..).

I had a great time and had some great battles - the best of which was a nose - tail duel with me chasing an Alfa Romeo Sprint for about 3 of the 5 lap race. I finally managed to pass him on the 4th lap and managed to open a bit of a gap. Quite intense heading down the main straight at about 160 kph (about 100 mph) when you are about a metre away from touching whilst wondering who is going to brake first... Much fun.
Another race was me chasing another Alfa (I think a GTV? - the one that always reminds me of a hyena..) - this time I couldn't pass him, but managed to hold on to him for the whole race.

I managed my fastest ever lap, decreasing my record by almost 1 second - quite a lot when a lap is only 1:30ish and 3 km.

The Mercedes-Benz flag was well and truly waved and the old beast got more than a few comments. :)

Most of the improvement over the time I have racing is learning how to use real track tyres - they are extraordinarily different to road tyres and the limits are far beyond my bravery at this point. The first 2 runs of the day I did were on my usual road tyres (the track ones were in transit in a van at the time - long story..), and the best i could do was a full 3 seconds off the eventual track tyre time. They were only just hanging on for dear life and I was really on the ragged edge to even achieve this as well. My road tyres are considered ultra high performance jobbies as well - Dunlop Formula FM901. I am super tempted when the time comes to just replace them with track tyres for normal use. The life will be crap, but the grip, oh the grip! :)

I think the next upgrade will be proper race pads for the brakes. There wasn't any discernible fade on Sunday, but I did use quite a lot of meat off the pads during the day and I am always a little reticent about using the full capability of the brakes just in case I completely cook them. At the moment I am braking at maybe 80% and still the brakes are far better than a lot of the other cars on the track. Should be fun when I can use them properly!

Anyway, enough. I will post photos when I get them.
 

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1978 280SLC, 5 speed, no electrics, no AC, pure 107.
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53 Posts
Discussion Starter #16
What size rims and tires are you running? Have you done any major mods to the suspension
Hi again,

My road wheels are 215/60-15 Dunlop Formula FM901 on BBS RA rims and my track wheels are 225/50-15 Yokohama A008RS on 15" Bundts... ;-)

Suspension is pretty much standard. Just new Bilstein HDs and new bushing all round. I tried to find urethane bushes but it just got too hard so i stayed with rubber. Alignment has been tweaked (kind of by accident), and now has about 1.5º negative camber on the front and is slightly toed out from specification. It turns in far better than before and is very neutral in hard cornering. Before the tweaks it tended to understeer slightly at the limit. Now it just just grips without drama no matter how hard I push.

A friend of mine took some pictures - they are not the most action packed as it's quite hard to get good photos without being on the infield of the track, but they give you the idea of the event.

:)
 

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Outstanding Contributor , Bob's Your Uncle!
-----'83 280 SL----- 5 speed....The PIG
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29,196 Posts
Tell me about the rev limiter. Is it stock?
And how does it work?
I have the M110, 5 speed and I have never pushed it beyond 5500 to 5800 rpms.
3 ird gear between 3000 and 5500 rpms is the best pull and sound in my SL.
 

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1978 280SLC, 5 speed, no electrics, no AC, pure 107.
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53 Posts
Discussion Starter #18
Tell me about the rev limiter. Is it stock?
And how does it work?
I have the M110, 5 speed and I have never pushed it beyond 5500 to 5800 rpms.
3 ird gear between 3000 and 5500 rpms is the best pull and sound in my SL.
Rev limiter is indeed stock. I would be very surprised if yours didn't have one. It is a rather clever mechanical device built into the rotor inside the distributor. If it wasn't so cold and wet and dark outside I would whip the one off my car and get a photo..

Basically it is a calibrated spring loaded device that shorts out the ignition at a preset limit. The limit is engraved on the underside of the rotor.

the M110 loves to rev and when you look at the basic design, it's no wonder. In cross section it looks VERY like 1960's twin cam racing engines from Alfa Romeo, Maserati and the like.

To really use the last 1000 rpm or so, you really need a freer flowing inlet and exhaust system. The sound is extraordinary. Mine will quite happily rev to 7000 with a modified rotor with the limiter disengaged. At this speed it is still pulling but I haven't really had the balls to see how far it can go before it starts to bounce the valves. I suspect not too much further...

I have heard of these engines quite happily running to about 8000rpm with slightly modified cams and/or advanced intake cam timing. Everything would have to be in perfect condition and balance to do this though - 8000 for a 6 is pretty serious.

:)
 

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Outstanding Contributor , Bob's Your Uncle!
-----'83 280 SL----- 5 speed....The PIG
Joined
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29,196 Posts
Rev limiter is indeed stock. I would be very surprised if yours didn't have one. It is a rather clever mechanical device built into the rotor inside the distributor. If it wasn't so cold and wet and dark outside I would whip the one off my car and get a photo..

Basically it is a calibrated spring loaded device that shorts out the ignition at a preset limit. The limit is engraved on the underside of the rotor.

the M110 loves to rev and when you look at the basic design, it's no wonder. In cross section it looks VERY like 1960's twin cam racing engines from Alfa Romeo, Maserati and the like.

To really use the last 1000 rpm or so, you really need a freer flowing inlet and exhaust system. The sound is extraordinary. Mine will quite happily rev to 7000 with a modified rotor with the limiter disengaged. At this speed it is still pulling but I haven't really had the balls to see how far it can go before it starts to bounce the valves. I suspect not too much further...

I have heard of these engines quite happily running to about 8000rpm with slightly modified cams and/or advanced intake cam timing. Everything would have to be in perfect condition and balance to do this though - 8000 for a 6 is pretty serious.

:)
Well, then...thanks for that info.
I guess I'm on the right track.
I pulled out the air filter can and put a K&N cone shaped filter right on the intake snorkel.
I also changed out the exhaust to single pipe flow through ...front to back.
You can hear it here:http://www.youtube.com/watch?v=CqJav8LQslM
and here:http://www.youtube.com/watch?v=Vzn3ytQp3do
 

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1978 280slc
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I'm pretty sure I've run my engine to about 6000rpm but the damned tranny kicks out of 3rd so it won't go much higher. Sounds like quite a howl if you ran it to 7000rpm. This is exactly the type of conversation I like to hear, it is really bitchin that you actually run your car. I'd give it a try but I'm too damned worried about breaking something to go crazy.

I know my buell motorcycle uses hydraulic tappets and if you run it past a given RPM the oil pressure goes up and shuts the valves down, effectively limiting your revs.
 
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