Mercedes-Benz SL 107 series versions, models & types in the catalog of cars
Mercedes-Benz SLC 107 series versions, models & types in the catalog of cars

I think Dave posted these a couple of months ago
I recently argued '72v'73 ratings on another forum because someone insisted the '73 was less than the '72. The only difference is the way the model years were measured.

 

Yeah... I recall these and remember disputing the specs myself. I think some assumptions were made when those web-pages were authored.

 

Thanks!

Reading the full article, I found the magazine citing (at the top of the image below) that the "Addition of the catalyst also required that the engine be retuned to compensate, resulting in a net horsepower decrease from 195 to 180." So it sounds like the ~190 HP number ("195") is jiving more with even the Car Collector magazine.

 

OK. Maybe I'm getting down to it. This specs page for the 1972 U.S. 350sl shows Net HP at 192, but gross HP at 230.

1991 BMW 850i Automatic

 

Well that did not work well.:big laugh:

 

And the 1972 Euro 350 SL reports 197 Net and 227 Gross. Wikipedia reports 200, so I assume Wikipedia is reporting NET, and most likely Wikipedia is then reporting correctly.

 

The first place I should have looked... Wikipedia for the definitions.


SAE gross power

Prior to the 1972 model year, American automakers rated and advertised their engines in brake horsepower (bhp), frequently referred to as SAE gross horsepower, because it was measured in accord with the protocols defined in SAE standards J245 and J1995. As with other brake horsepower test protocols, SAE gross hp was measured using a stock test engine, generally running with few belt-driven accessories and sometimes fitted with long tube (test headers) in lieu of the OEM exhaust manifolds. The atmospheric correction standards for barometric pressure, humidity and temperature for testing were relatively idealistic.


SAE net power

In the United States, the term bhp fell into disuse in 1971-72, as automakers began to quote power in terms of SAE net horsepower in accord with SAE standard J1349. Like SAE gross and other brake horsepower protocols, SAE Net hp is measured at the engine's crankshaft, and so does not account for transmission losses. However, the SAE net power testing protocol calls for standard production-type belt-driven accessories, air cleaner, emission controls, exhaust system, and other power-consuming accessories. This produces ratings in closer alignment with the power produced by the engine as it is actually configured and sold.


EDIT: The fast that BHP fell out of use around the same time these cars were being produced might explain why 230 HP (BHP) was reported on some earlier years, when the net was closer to 190 HP, which was used for the mid-70's models undoubtedly.


.... damn those links! I got to the details by clicking the buttons under individual models. I'll see if I can fix those links later. Gotta run now.

 

Fonzi:

I just came across your post with questions on the power of the Euro and U.S. 450 SL and 450 SLC. This is a topic I have done a lot of reasearch on. If you're still interested, I'll chime in. I have enough MB literature to fill a library with. I've been reading about Mercedes cars for decades, and being from Europe, I am familar with PS, hp, DIN SAE hp, etc.

Dan

 

Chime in

 

Numbers on paper don't mean shit... put that sumbitch on the dyno and then you'll know!

 

:thumbsup: With the air on or without?

 

I have done a little research on 4.5 euro power myself. The early euro 4.5 were higher. Like 218-225 I think. That comparable to a US 560sl. The later ones had a tiny bit less power. Perhaps at the lower end range like 215-218 I think. Don't quote me.

I know the euro 380 had 200 HP, more than any US 450 ever had.




Sent from AutoGuide.com App

 

Hmm--mine has become very peppy these days. Of course there is no Cat, no O2 sensor, EGR, smog pump or anything else. When redoing the FI, I set the WUR to Euro specs as well. Can't say how much it helped, but the car is smooth as silk now, much more powerful and it gets way better mileage.

I also set the throttle linkage up and continue to experiment with it. For instance, some of that problem you had with shifting may have been from improperly adjusted linkage. I noticed it can change the behavior of the tranny.

 

Some of this has already been commented on by Fonzi above, but here it goes.

There are several aspects of horsepower/torque ratings that seem to still confuse car enthusiasts, to the point that even car magazines still don't get it right.

There needs to be a distinction made between two items that people confuse often. One is the method of measuring power; the other one is the units of power.

In the U.S., years ago (pre 1973) horsepower and torque ratings were given in SAE Gross horsepower and lb-ft, respectively. Gross power is the power of the engine without much ancillary equipment. Since some power-robbing equipment was not taken into account, gross ratings naturally yielded large numbers. Starting with the 1972 model year for U.S. made cars and 1973 for European cars, the power and torque ratings were given in SAE Net. Net power does take into account the power robbing equipment that cars need to run properly. The numbers, naturally, are lower. For Mercedes cars, it is with the 1973 model year that power went from gross ratings to net ratings.

In Europe, the measuring method was defined by DIN. DIN is very close to SAE net. Nowadays, Europe has turned to yet another measuring system, ECE. ECE yields slightly lower numbers than DIN.

The second item is the units of power themselves. In Europe, nowadays, torque is measured in Newton-meters, Nm. In the U.S., torque has always been given in lb-ft. All you need to do to convert from Nm to lb-ft is multiply the Nm figure by 0.737.

When it comes to horsepower it is also simple, but there is one point that leads to confusion. Power in the U.S. is measured in the English-system horsepower unit that was created by James Watt. One horsepower is defined as 33,000 lb-ft/minute. Since this unit was defined in terms of a nice even number in the English system (33,000), it was not that convenient for Europeans using the metric (later SI) system. The Europeans decided to define the metric horsepower unit as 75 kgf-m/second. If you convert this into lb-ft/minute, it is approximately 32,549 lb-ft/minute (slightly less than 33,000 lb-ft/minute.) Compared to the original English-system horsepower of 33,000 lb-ft/minute, the metric-system horsepower is a slightly smaller unit. In Europe, the Germans abbreviate the metric hp as PS, the French as cv.

Because of the small discrepancy between an English-system horsepower and a metric horsepower, there is a conversion factor. 1 hp = 1.01387 PS; 1 PS = 0.98632 hp.

Keep in mind that the difference from hp to PS has nothing to do with net and gross horsepower ratings.

Nowadays, in Europe, you see power ratings in kW. That is just another unit of power. The conversion factors are: 1 kW = 1.34 hp; 1 kW = 1.36 PS.

In my opinion, one reason there is so much confusion between PS and hp is that both mean horsepower but have slightly different meanings. No one confuses Nm and lb-ft because they have completely different names, but when in Germany they call a horsepower PS and when translated into English it becomes a hp, people lose track of the different meaning.

Here's an example. In 1986, Mercedes launched the face lifted W126 models. Among them was the 420 SEL which was rated at 201 hp SAE Net in the U.S. and 204 PS DIN in Europe. Interestingly enough, applying the PS to hp conversion, 204 PS = 201 hp. Therefore, these cars had the same power in Europe and in the U.S.

I'll cover the power of the 107 SL and SLC models next time.

 

I'll cover the power of the 107 SL and SLC models next time.

Excellent summary - Look forward to the next edition

Having the methods of rating HP changed during the early 107 production years has caused a lot of confusion.

 

This is what Sternzeit 107 has posted. Click on the US flag for translation.Sternzeit 107 - Die USA- Modelle in Zahlen

 

As promised, here are the power ratings of all U.S. model 107 SL roadsters and SLC coupes.

SL Roadsters

1972 350 SL (4.5)
230 hp SAE gross (approximately equal to 190-195 hp SAE net)

1973 450 SL
190 hp SAE net

1974 450 SL
190 hp SAE net (180 SAE net in California)

1975-1979 450 SL
180 hp SAE net

1980 450 SL
160 hp SAE net

1981-1985 380 SL
155 hp SAE net

1986-1989 560 SL
227 hp SAE net


SLC Coupes

1973 450 SLC
190 hp SAE net

1974 450 SLC
190 hp SAE net (180 SAE net in California)

1975-1979 450 SLC
180 hp SAE net

1980 450 SLC
160 hp SAE net

1981 380 SLC
155 HP SAE net

 

Great thread! Thanks for that MercFan.

 

MauiSL,

Thanks for the kind comment.
One of these days I'll try to tackle the power figures for all the European versions, but there are more Euro versions than American versions, so it'll take some more research.

MercFan

 

Automobile-catalog.com has all the specs I believe. There is very little there that I have found to be incorrect. In fact I can't even remember what I thought they had wrong.

 

I agree that Automobile-catalog.com has few mistakes, but it does have some. I spotted a few in some Mercedes specs.

 

So if you had the decision would you install a '72 4.5l. a 500sl motor, or install the head on the stock block after retrofitting the internals?

 

For a US 79 450sl?
Me personally? Either a 5.0 or 4.5 euro with a matching fuel injection system, or maybe a 5.6, or better.

 

1. low compression allows for crappy and low octane fuel to be used.
2. crappy low octane fuel can have less additives that create polluting gasses
draw your own conclusions as to why the world went to low CR

This had brilliant deferred effect on modern cars. High octane fuel had only one and easy pathway: more displacement. We now have cars that produce 265kW from a 2000ccm engine and produce less poisonous gasses than original Vespa scooter of 50's.

just my opinion...

 

Yeah I only use gas with Techron in it. But your assumption is articulate and spot on I believe.

I read the post about the 350 heads and pistons. But adding the rods and pistons would create a very short stroked engine allowing the engine to generate revs faster which may create more top end hp while reducing torque and that is what these engines were designed to produce.

If I take the time to swap piston I'd rather increase the bore with the 5.0 or 500 pistons making the 450 and actual 5.0. Wonder if anyone has ever taken the time to add the 350 heads to a bored 4.5 and use the euro cam profile?

I'd like to keep the block that is true to the car. The cast irons are durable though they create a great deal of loss to inertia and rotational friction.

I read that adding electric fans helps reduce part of that problem. But I don't know if they were using MB electric fans from a late model......

But if you're going to increase bore why not use the 560 rods and pistons?? Don't know if the block has the tolerance for that.

 

I am doing just. I am building a 5.6L engine based on a 4.5 block. To go to 5.6 the stroke is increased to 94.8mm from 85mm and the bore to 96.5mm from 92mm. Here is the bored (96.5mm) block with the 5.6 crank in place. A small amount of clearancing was required to fit the 5.6 crankshaft. Also the 3.5 stickshift flywheel fits the 5.6 crank and it is even machined for the pilot bearing.
Everything is being blueprinted to new specs. Crank was totally gone through, rods received a performance rebuild, everything will be balanced. My point is to keep an iron block engine that my manual transmission fits and attempt to stay true to the original concept while increasing power.

 

Does seem like a lot of work. I like it though. But look at the 72 sl engine that made 220 horse. What is the real desire in increasing the stroke? The shorter stroked engine should build revs faster. Granted, the bore and stroke is more perfectly squared. (read longevity).

Then there's all the talk about the 350 heads which from what I could read has a smaller quench area. From what all I see the 4.5 engine needs to have a higher compression which can be done in several ways. The emission system robs the engine of a great deal of power that the predecessors created.

I think weight saving is the first priority. I am supposing that any manual tranny weighs less than the auto. But the auto trans is pretty damn durable.

 

Heads

I have done quite a bit of testing different heads. The 3.5 heads are 39cc which would give about 10.0:1 static cr but they can only use solid lifter cams and the combustion chamber is so small it shrouds the valves quite a bit. The 4.5 K-jet heads are 45cc, the valves are unshrouded and they can run hydraulic cams and result in about 9.6:1 cr. The 5.6 heads have 50cc chambers which would result in about 9.2:1 cr but they have larger intake valves/ports and the exhaust valves have larger ports and 9mm stems instead of 11mm. Cams are a whole different matter.

 

Well 3.5 Tony wrote this:


I have done quite a bit of testing different heads. The 3.5 heads are 39cc which would give about 10.0:1 static cr but they can only use solid lifter cams and the combustion chamber is so small it shrouds the valves quite a bit. The 4.5 K-jet heads are 45cc, the valves are unshrouded and they can run hydraulic cams and result in about 9.6:1 cr. The 5.6 heads have 50cc chambers which would result in about 9.2:1 cr but they have larger intake valves/ports and the exhaust valves have larger ports and 9mm stems instead of 11mm. Cams are a whole different matter.

Tony, thank you! This was awsome to read first thing this morning. To bad the better breathing 5.6 heads won't work on a 4.5 block... bored or not.


Still, why not just swap in a 6.9 motor? It's got every bit of HP as an AMG 4.5 would have had... not to mention the bone crushing torque.

 

I'm not concerned about weight-the 3.5 coupe is a 3600lb car. True-the 3.5 heads have a small combustion chamber (39cc). They would result in a 10.0:1 static CR on a 5.6 but they only run solid cams and the valves are substantially shrouded by the small combustion chamber. I think they would be a waste on a 5.6 due to the low flow potential. The 450
K-jet heads have 45cc chambers and the valves are unshrouded but they still have the same small valves as the 3.5. The 560 heads have larger intake valves/ports and larger exhaust ports+ the exhaust valves have 9mm stems vs 11mm stems found on the 3.5/4.5 heads. The 560 chambers are 50cc so the cr would be 9.2:1. If you wanted to raise the cr on a 4.5 that has the dished pistons(K-jet engines) you could use a 5.6 crank/rods and turn down the pistons to the correct deck height. That would give you a 5.0L engine with 10.0:1 cr and you would not have to bore it. That was my original plan but boring was only a little more than honing for new rings so I went with it. This is really no more trouble than a quality rebuild except you need a good 5.6 engine for the crank/pistons/rods. As a plus you start with new cylinder bores. The 5.6 pistons have a low friction coating that the 3.5/4.5 pistons lack so less frictional losses.
I have proven the 5.6 heads will fit a iron block engine so that is my path for now.

 

Great information!
So from this I am understanding that there are really three options:

1) Use a 560 head and that would equate to 9.2:1 with no other changes;

2) Add the crank and rods only for 10.0:1 CR and increase displacement to 5.0L;

3) Or go hog wild by adding the heads, crank, rods and pistons requiring a good bore and have a 6.0L? With a 10.5:1 Cr?

 

Sorry for the confusing redundant posts-my computer locked up and I did not know that both posts I was writing got uploaded. The figures I gave for CR assume 5.6L of displacement so they would be lower on a 4.5. No 2 in your response is correct but you need to machine about 4.5mm off the piston top. Since the dish is 8mm deep there is plenty of material. I have a picture of a 4.5 piston I machined before I changed my mind and bored it. I don't think the iron block could be bored to 100mm. At 96.5mm there is about .170 wall thickness.

 

Ah well that explains everything. Did you use the stock FI system?

Are those 4.5 pistons for sale?

 

I only machined one 450 piston before I changed my mind but a stroked 5.0 is feasible. I bought a 450 short block at the Pick and Pull for almost nothing on half price day and the pistons/cylinders were in spec so it would have been a good candidate. I would love to build engines but I would not want to do it for profit-too many things to go wrong and I don't have enough time to work on mine.
The engine is not complete yet(it is just one part of a large project)but I plan on running Megasquirt and EDIS ignition. The car is a '71 so no smog check. I am still undecided on what heads I am going to use. I want to use hydraulic cams so the 3.5 heads won't work.

 

Are you using those efi's because the K-jet wouldn't work?

 

As far as the FI/ignition is concerned Megasquirt is a total engine management system and since my car is not subject to smog inspection I can run what I want. I plan on placing the EDIS coil packs where the fuel distributor used to be.

 

Well for those of us that are in no way in love with the myriad of red wires all over the intake area, I'd think that the different 107's had different calibrations for O2 to fuel ratios.