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Pre engine rebuild dyno run

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RaceDiagnostics

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1979 450SL UK spec
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Discussion starter · #1 · (Edited)
The engine in the car has unknown miles and came from a 1980 450SLC and has now been in the car for 10 years or so.

The wheel horse power was a slightly surprising, only 147bhp (other runs were 144 & 146bhp), using this calculator it equates to ~190bhp at the crank.

Wheel Horsepower to Crankshaft Horsepower Guestimator

www.mk5cortinaestate.co.uk

If accurate, the car has lost about ~33hp over the last 40 years. Of course it is always difficult to know just how accurate the dyno is, so the only meaningful measure will be to compare to how the engine performs next year after its rebuild.

I was pleased about the exhaust, absolutely no smoke at all.


2650110
 
#2 ·
For my 560SL, I got 182HP which comes out to 231HP on you calculator. That is slightly above the advertised 227HP, so I would estimate you probably are down a bit. Yes I am looking forward to the after overhaul results. Make sure you run the car at least 5000 miles after overhaul before doing the second dyno run. The power will noticeably increase as it breaks in.
 
#3 ·
A dynamometer is useless unless it has been properly calibrated. If this test is offered as a service thay should provide a copy of the calibration certificate. Also, there are correction factors that can be applied for intake air temp/density and fuel temp, if either deviate from the standard the power will be off from standard.
 
Discussion starter · #4 ·
roncallo said:
For my 560SL, I got 182HP which comes out to 231HP on you calculator. That is slightly above the advertised 227HP, so I would estimate you probably are down a bit. Yes I am looking forward to the after overhaul results. Make sure you run the car at least 5000 miles after overhaul before doing the second dyno run. The power will noticeably increase as it breaks in.
Click to expand...

Just had a play around with your numbers on the calculator, it has options for 3 and 5 speed, if you average the two (for a 4 speed) the results is spot on for your car, which is probably just luck. How many miles were on your 560 when you had it dyno'ed.

5000 miles could take me years to do.
 
#5 ·
Interesting, thanks for sharing Jim!

I wonder if we have a dyno anywhere in the west of Ireland, I'd be tempted to test my old lady!
 
#6 ·
I see that the OP's car is a UK version 450. With that already in mind, this is just a friendly FYI reminder that U.S. spec cars for 1980 were detuned down to 160hp vs. the 180hp of prior year 450's. 1980 was the first year of O2 sensor (closed loop operation) equipped 450's for the U.S. The camshafts were different, and I vaguely remember (but I could be wrong) that the compression ratio was also slightly reduced.
 
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#7 ·
My understanding that substantial power is lost in heads, where intake makes 90 degree bend in what effectively acts as restrictor plate. It is possible to port and polish some of it out. However, no matter what you do it will never be fast.
 
#8 ·
Is this the engine you plan to swap fuel injection? Any other mods while it’s being rebuilt? Based on your dyno numbers most 450 owners in the USA would be happy campers.
 
Discussion starter · #9 ·
SinSL said:
My understanding that substantial power is lost in heads, where intake makes 90 degree bend in what effectively acts as restrictor plate. It is possible to port and polish some of it out. However, no matter what you do it will never be fast.
Click to expand...
I have no clue if a port and polish will make any improvement to this bad design. My main goal is to paint the engine bay, fix the oil leaks from the crank seals and head gaskets and while i'm in there I may as well sort out the crankk and big end bearings. Regaining a bit of the lost bhp is a bonus. The car in its current form is reasonably fast for a car of its age.

 
Discussion starter · #10 ·
Alphasud30 said:
Is this the engine you plan to swap fuel injection? Any other mods while it’s being rebuilt? Based on your dyno numbers most 450 owners in the USA would be happy campers.
Click to expand...
I have no plan to touch the fuel distributor as it seems to be well set up at the moment, the air fuel mix seemed good on the dyno. It will just be a tear down, inspect and rebuild of the existing engine.

This is the engine as it was delivered ten years ago, it was a bargain £360 delivered to my door. it would have been good to do the rebuild back then but I didn't know one end of a spanner from the other back then.

Image
 
#14 ·
RaceDiagnostics said:
Just had a play around with your numbers on the calculator, it has options for 3 and 5 speed, if you average the two (for a 4 speed) the results is spot on for your car, which is probably just luck. How many miles were on your 560 when you had it dyno'ed.

5000 miles could take me years to do.
Click to expand...
Hard to tell what to use here. I had my stock 560SL Delilah had 4 speed automatic no lockup converter I would estimate 150,000 miles at the time and produced 182 HP at the rear wheels. Samson 5 speed automatic with lockup converter was also tested and produced 348HP at the rear wheels. Neither of them ever got out of third gear, which adds to the losses. I can tell by looking at your dyno sheet you never got into top gear either, not at 85 MPH at wide Open Throttle. In fact that might be second gear only, which will decrease your numbers. Also you numbers are Uncorrected, you should be able to look up the temperature, pressure and RH for the time of day for the area you data was taken and correct. But trying to get an accurate number form a quick chassis dyno run is really only good for showing changes in performance, which is what you are doing. So just try to do exactly the same thing at the same place next time.
SinSL said:
My understanding that substantial power is lost in heads, where intake makes 90 degree bend in what effectively acts as restrictor plate. It is possible to port and polish some of it out. However, no matter what you do it will never be fast.
Click to expand...
SinSL said:
My understanding that substantial power is lost in heads, where intake makes 90 degree bend in what effectively acts as restrictor plate. It is possible to port and polish some of it out. However, no matter what you do it will never be fast.
Click to expand...
RaceDiagnostics said:
Yes, it was a great deal considering now, a single pair of crankshaft thrust bearing shells, cost about the same, ok Euro330. Another case of extreme exploitation of its customers by Mercedes.

View attachment 2650305

View attachment 2650306
Click to expand...
I hope that is for a set?
 
Discussion starter · #15 ·
roncallo said:
I hope that is for a set?
Click to expand...
I wish, that is just for the thrust bearing shell pair, a full set of crank bearings is ~ £600 from MB, since the supply of STD size aftermarket parts dried up they have started to crank up the price.

It will be cheaper to buy the 0.25mm oversize bearing kit (still ~£100) and grind the crank to fit, even if it doesn't need it.
 
Discussion starter · #16 · (Edited)
Just remembered about my "Torque" app that can do a dyno approximation, that will also be good for comparative purposes. Will give it a try on the next dry day we have, and give it a few runs to see how repeatable it is.

Edit oops, Torque won't work without an obd connection but I think there are a few other aps that work independently.
 
Discussion starter · #17 ·
Some good news today, I received the last set of standard main bearings from a supplier in Estonia, having searched the rest of Europe and the USA.I may or may not need them but I am relieved to have them in stock now. The MB price for the set (blue only, no red left) is now more than 600 Euro. I have now almost all the parts I need for a rebuild, however my wife saw a new (old) house today that she wants us to buy, that could put the plan on hold for a year.

2652027
 
Discussion starter · #19 ·
The engine is still in the car, given so many of the engine parts are going NLA at an alarming rate or are astronomically priced by MB, I want everything on hand before starting the job. Anything I don't use can be resold later at a profit the was parts pricing is going.

Just look at the problems Juyma had with parts when rebuilding his 380.
 
#20 ·
Makes sense to your approach. I’m sure you can find a used crank if the crank in your car needs to be turned undersize to clean up the journals. I wonder if MB nitrided the journals which wouldn’t surprise me Given how over built they are.
 
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