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87 Euro500HVSEC. 88 Euro 560HVSEC. 89 Euro 560HVSEL
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Discussion Starter · #1 ·
The lads at Carobu Engineering are about to hit the engine dyno again with their own US Spec 560 test mule engine
https://www.facebook.com/pg/Carobuengineering/posts/?ref=page_internal

Their engine has just had the heads freshly re-furbed and new guides etc after they realised the valve guides were worn and the heads needed pulling after the last session on the dyno with the US spec factory exhaust complete bolted up (the whole exhaust right to rear muffler tip was removed from the car and dragged into the engine room and bolted up for testing if you scan down to their older FB posts showing the dyno read-outs as well

This time they have bolted up some AMG spec headers to see how they will perform

This R&D testing is to continue in phases as they work there way through various mods to see what will waken up the engine including swapping in 300hp cams i provided until they design their own cam and it will include mods they want to carry out in due course on the 560 intake to see if they can improve that intake without having to go to the expense a custom designed intake.

I think all of us will be able to closely follow this and enjoy the ride.
End result is they wish to come up with solutions for M117 owners with proven research on an engine dyno to back it all up

That last 560 engine they rebuilt was a full custom job with forged pistons and rods and EFI conversion using a highly modified D-Jet intake and custom AMG spec cams etc so that was an expensive build in the below link
1986 Mercedes Benz 560SL ? Carobu High Performance Parts and Accessories for Ferrari
 

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Outstanding Contributor, Vintage Moderator
450slc5.0cab 280sl5sp 280se4.5 500se+500slAMG +250seStkW108 350sl4spdX3 500secEuro
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I was honored my d-jet intake manifold went to Tate for Pearson’s 560sl. :)

I am glad he is testing the components step-by-step and should be able to document the gains of each.

It seems that with Pearson’s 560sl the intake was a bottleneck. It seems that some boost would probably solve that. I wonder if they plan to test any boost systems.


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Premium Member
87 Euro500HVSEC. 88 Euro 560HVSEC. 89 Euro 560HVSEL
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Discussion Starter · #3 ·
I believe they perhaps might be going to try out the Dkubus Franken-CIS bolt on system for mapping control of spark and fuel amongst the R&D work - would be interesting if they do as it keeps the engine bay looking stock
 

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1986/1990 W126
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Ah it's that SL belonging to Mark P? Awesome.
 

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R.I.P. Never Forgotten
1983-2007 MB's
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They completed their baseline run with both US exhaust and with tri-y's on their 9:1 US 560 motor.

Result, 26hp, 22ft/lbs torque.

Still lots more to come, apparently.
 

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Smoke Silver '87 560SEC, Black Pearl '87 560SEL
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If the tri-y's delivered a 26hp increase, then I'd expect that the Euro Logs with a dual exhaust sitting in my garage would get something in the middle, maybe 15hp. Hardly seems worth the effort. The 3.07 LSD I put in my 560SEC has made a huge improvement though.

Hope they come up with something commercially feasible for a reasonable HP increase!!
 
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Intake air volume (throttle body size, intake manifold design and engine bay hood clearance) will continue to be the primary roadblock to gaining significant performance gains for the M117. Head work, tri-y's, cams, fuel and spark systems (like Franken-CIS), increased compression ratio would get performance up to 325hp or so, but beyond that (assuming SOHC heads) is a challenge. Absent forced induction or quad cam heads, can't squeeze much more out of the M117. And getting to 325 ponies would probably cost $10-$15k.

Agree with Mike - a higher diff ratio is a good way to get noticeable performance improvement (at the expense of fuel economy - higher RPMs). Diff change and tri-y's are a sub $3k investment that would be really noticeable.
 
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So 26 HP gain just from the tri y manifold?
No not just from tri y, look at the two exhausts . One is a full USA exhaust with manifolds , caTalyitc converter , mufflers etc . Just like a stock car.

The other is just tri y with no mufflers or catalytic converters , a completely open straight pipe exhaust . No one would really run a car like that .

Figure 10-15 Hp for the tri y and 10 hp for the lack of catalytic converters and mufflers
 

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The Euro 560 SEL with 10:1 CR came with 300HP from the factory, and 279 with cats.

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Discussion Starter · #11 ·
Intake air volume (throttle body size, intake manifold design and engine bay hood clearance) will continue to be the primary roadblock to gaining significant performance gains for the M117. Head work, tri-y's, cams, fuel and spark systems (like Franken-CIS), increased compression ratio would get performance up to 325hp or so, but beyond that (assuming SOHC heads) is a challenge. Absent forced induction or quad cam heads, can't squeeze much more out of the M117. And getting to 325 ponies would probably cost $10-$15k.

Agree with Mike - a higher diff ratio is a good way to get noticeable performance improvement (at the expense of fuel economy - higher RPMs). Diff change and tri-y's are a sub $3k investment that would be really noticeable.
Al the M117-968 heads flow well stock so that is really not an issue in the equation - although if you have them off for re-furbing then that is the time to tidy them up - but no porting is required other than removing casting dags and minor tough up work. Relieving the valves a tad for a bit more flow will help. My engine shop has just finished working 2 sets of 560 heads but that included swapping in aftermarket Ferrea intake valves to AMG Spec to help a bit more. I have aftermarket springs & Ti retainers but that is not necessary for a basic head makeover.

The intake Manifold plenum design is the main issue to restriction as i see it besides the stock US spec cams which are very mild

The 560 throttle is also not a restriction as proved by Carobu in the 560SL engine rebuild with flow testing done
 

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No not just from tri y, look at the two exhausts . One is a full USA exhaust with manifolds , caTalyitc converter , mufflers etc . Just like a stock car.

The other is just tri y with no mufflers or catalytic converters , a completely open straight pipe exhaust . No one would really run a car like that .

Figure 10-15 Hp for the tri y and 10 hp for the lack of catalytic converters and mufflers
Didn't Henrick aka 48hp do a before and after dyno on his originally GenI 500 US version SEC?

The second was with Try-y's, and high flow dual in/out cat, 2 inline staggered hush puppy resonators (instead of the kidneys), etc.
If I remember correctly the dyno gain was around 28 hp?
 

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Ironically there are two Mark Pearson’s. The one with the 560sl is based in Chicago and San Francisco areas. He has sent the car to Atlanta and SoCal for work. I don’t know the Mark Pearson that I believe is a w126 Guy.


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Today the Carobu guys achieved another 10hp by running the lid off the air cleaner.

Illustrating all the restrictions our cars have in stock form. The CIS lump in the air cleaner restricts flow. Food for thought.

Carobu quote: "Currently, we are developing our piggyback fuel/ignition package that anyone can add. It will come with the control modules, a modified distributor, sensors and wiring harness."
 

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Great to see what caribou is doing for these cars . Much better than the blue Ridge goof In Atlanta who butchered MarkPs sl originally , before it was sent to caribou to correct his shoddy work
 

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87 Euro500HVSEC. 88 Euro 560HVSEC. 89 Euro 560HVSEL
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Discussion Starter · #18 ·
Hendrik is a very smart guy and he replicated the AMG design but in s/steel and i am sure if you purchased his product they would work just fine.
There was never very little difference in performance with the Tri-Ys versus the AMG design as MB tested the AMG version and came up with their own design being the cast-iron Tri-Ys. The internal diameter of the AMG version were slightly larger but that is not necessarily better for lower end street torque band.
 

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Interesting, I guess then depending on how much he asks for them the advantage could be price and availability, as the cast original tri y are not easy to find.



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Discussion Starter · #20 ·
Yes that air-cleaner design proved to also be a restriction to air-flow - so another item that needs a good think tank to come up with a better solution
 
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