Hi,

I've got a UK 1991 190E 2.5-16 and its blown a valve on cyclinder 4.

Head is obviously coming off to fix this but while its off what else can be done?

Port and Polish?
New cams? If so which ones and do i need new cam springs or followers?
Tappets? Are mine hydralic or solid? How would i fix the tappet noise?

The head is going to have a good inspection and clean up before going on which should reduce the oil consumption of about half a litre every 1000miles.

What else and in what combinations shall i do?

Also what is the main difference between this engine and the 2.5-16 in the Evo 1 and Evo 2?

Thanks

Nic

u should also try posting on www.190revolution.net

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http://www.190revolution.net/mods/tj...gs/ryansig.jpg

To be honest I wouldnt do any modifications to the cylinder head, the ports and valves where originaly optimised by Cosworth here in the UK for the 2.3 -16 and these specs where carried over by MB to the 2.5-16. The only mods being for either reliability or improved low speed torque. The head is really at its optimum for driveability v performance, any further changes will result in poor low speed drivability etc. The Evo cams can be fitted which again give a power improvment above 4000RPM but actually make the car more lethargic below this point, the Evo 1 had a shorter stroke crank with a larger bore size which allows higher engine speeds and the engine to pickup quicker it uses a different cylinder block. The pistons used by the Evo 1 can combined with your long stoke crank to give 2.6L, this gives a usefull torque increase. The Evo 2 engine tuning became more focused on performance , with only a three main bearing crank, single row timing chain and high lift camshafts this again does nothing for road performance unless driven at high engine speeds. Both Evos run lower final drive ratios to keep the engines up in there higher power band. The main improvments available today would be in throttle body fuel injection and engine management which improve reliability, all round performance and fuel economy. Regards Linds

Sorry I forgot about your burnt valve , basically I have never seen one burn on these engines unless you have a very weak mixture( air leak, bad injector,poor fuel supply, or the valve clearence is too tight[the cam followers are solid with shims to adjust, and must be done accurateley and then redone when the cars as run for about 50 miles]

Thanks Linds, so basically theres no real point in trying to get more power out of the std 2.5-16 and i'm just better off getting it running properly?

Nic

I would of course fix the valve then port and polish the head. Then get the valves all adjusted properly and put back together. With a Port and Polish it may even run better than you ever remember it. Of course then again I would love to have a 2.5 16V engine in mine!

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~Jamie
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2003 Pewter C230K SC C1, C4, C5, C7, heated seats, CD Changer, and 6 Speed. ContiExtremes on the C7's.

1986 190E 2.3 Black, Auto, Mods to come soon.....

As I already said theres no more room for improvment on Keith Duckworths head work unless you want to loose power or you are increasing displacement or adding forced induction. The port and chamber design on these heads is far more efficent then the early or late 104 24v engines.Obviously any wear n tear will have to be sorted and spend a few hours getting the clearances spot on.

Hey now there is an idea. Forced induction. Your right about the head. I doubt you could improve it but you could definately have it flowed and mated to the intake and exhaust. Maybe extrude hone the exhaust or intake. But a supercharger might be sweet or maybe even nitrouus.............drift on.

Actually, the 2.5-16 was an improvement on the Cosworth 2.3L design, since it was executed 100% by Mercedes. It got a beefier block, better oil distribution, lighter pistons, better vibration dampening, updated fuel injection system and other bits, it has a much smoother, broader power range engine than the 2.3-16.

Since the head is coming off anyway, now might be a good time to replace the timing chain and tensioner if it has significant miles on it...no change in performance, but a nice insurance policy!

J.G.

What about Mike Costin's??


I don't know much about these engines and have never driven either, but would have to disagree with this automatically making them better. I'm no historian but this is what I learnt:


Reading a book on Cosworth recently, it told how Mercedes were aware of Cosworth's race pedigree engine building experience (Ford GT40 "DFV" V8 anyone?) and asked them to develop the 2.3 for a specialist racing application & more power, as they planned to use it in a rally racing version of the 190E.


Then Audi came along to rallying with the Turbo 4wd Quattro and Mercedes knew the game had moved on, and they couldn't compete. so they didn't make a rallying 190E.


However, having already paid Cosworth to develop a powerful new four cylinder, and still wanting to race the new 190E, they decided to build it into a roadgoing 190E and use that as a basis for Touring Car racing. The book told how this was ideal for Cosworth, as an original contract to build, say, 500 engines turned into a commission to build 5,000. The engines were shipped to the UK for the work.


That's how a Mercedes ended up with a rather unlikely high-revving performance engine - they then made it a little more Mercedes-like by enlarging the displacement to 2.5, and by this time were making the heads themselves, since it was expensive sending engines to the UK to have it done (something that wasn't a problem before they decided to build thousands of roadgoing ones).


So, I agree Mercedes might have developed and improved the engine (in their eyes) later in life, but the original 2.3s have a pedigree the 2.5 doesn't.

I wonder what Mercedes would have developed had they not got Cosworth to do it - probably a heavy iron straight-six mated to a standard auto....


Russ

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190E's:
2.5-16v 1990 90,000m Astral Silver
2.0E 8v 1986 107,000m Black 2nd owner
http://www.maylane.demon.co.uk/190esmall.jpghttp://www.maylane.demon.co.uk/190esmall2.jpg

Look...
Have had several of them apart.
Own an 85 vintage 2.3-16 myself as a daily beater.

The 2.3-at least the early ones-have VASTLY beefier parts in its innards than the later 2.5;s.
have been into discussions previously as to materials aso.
One thing´s for sure...
The OEM 2,5 parts are NOT to be compared to the 2.3.
Con rods for instance...
The 2,5;s look like a damn joke in comparsion...
Slugs...the 2,5;s are "hypereutectic"(or whatever you wanna call em),and the ones in my 85 are most def forged Mahles..
Crank seems to be forged in both instances tho.
Head...got both laying at the shop.No differences as far as i can tell.2*38mm in asf...
Hedder...yup.The 2,3 is in at a 45mm primary vs a 50 pri for the 2,5.(..and frankly who makes a 2" primary pipe for a 600cc cyl@7 grand?)

None the less..
THe 2,3 makes less power..yup.
AT 500 RPMS LESS!!!
Look at the torq figures between the two,and what rpms they´re achieved.

I´ll put it blunt.
I have no idea why Merc F:ed the cossie idea up.

To give you an idea.
Old dragracer over here turbocharged one of the 2,3,s back in the late 80;s.
Put it all in a rail chassis and a vega body.
Boosted the living crap out of it and ran a 7,80@330km/h.
What that turns out in power?
You do the math.
Car weighed in at 2200lbs.

Only thing the dude swapped was the slugs,and cut the cam sprockets to be able to dial LCA in.

Old thread but interesting all the same. Just to chip in my two cents: Cosworth has codes for the 2.3-16 (WAA), the 2.5-16 (WAB) and EVO -short-stroke- (WAC). Which seems to suggest that Cosworth's involvement lasted longer than just the period when it manufactured the original heads.

I have a AUTOCAR magazine article dated 7 August which an interview with Mike Hall of Cosworth who was the cheif designer of the 16 valve. He said "It was a fairly straight forward job.... For a start, that 2.3 block was very strong already. The bottom end was entirely standard." The article goes on to say that apart from extra sump baffles, crank, con-rods/caps, bearings in the 2.3-16 were all standard.

Interestingly the 2.3-16 was Cosworth's first one piece head with integral camshaft beds journals machined into the head. This resulted in shifting the camshaft bearings to in-between each cylinders camlobes, as opposed to in-between each cylinder, which Mike Hall saw as beneficial interms of camshaft flex. He went on to describe how he need to access cylinder head bolts determined the distance between camshaft centers, and this in turn determined the 45 degree included angle of the valves. Previous Cosworth designs being around 40 degrees.

From the article, "That particular angle also left me able to choose a combustion chamber volume that allowed me to use flat-topped pistons to get the 10.5-to-1 nominal compression ratio to ensure good efficiency. In fact the final configuration is extremely efficient."

It goes on that the original brief from Mercedes-Benz was for an output of 320bhp, hence the biggest valves that could be practicably fitted were fitted to the combustion chamber. Cosworth were then instructed to detune the engine to 185bhp for street use. 'Hall went back to the drawing board, but revisions required to bring the Cosworth head down to the required 185bhp were limited to reducing the inlet and exhaust port sizes and adjusting the camshaft profiles to milder settings. Gone was the necessity for the dry sump configuration, special conrods and the specialised Kugelfischer fuel injection gave way to the more everyday electronically-controlled mechanical Bosch K-Jetronic injection.'

Hall also talks about the fact that although the order was for 5000 (this is 1987) were being manufactured at Cosworth, "Mercedes does machine and assemble some of the heads itself because at the moment we are not able to cope with the demand."

No talk of engine blocks being shipped to England, however. Rather Hall says "The (exhaust) manifold is a Mercedes Benz product but otherwise Cosworth delivers to Stuttgart production heads ready to bolt into place."

Much has been posted about increasing the power of over the stock level, and I think I've read most of it. And my summary of it all is that almost any power increase will result in loss of flexibility. This was the certainly the case with the 320-380bhp race engines! However reading a recent road test of a stock EVO II in Mercedes Enthusiast, they comment in how much like a standard car it felt like until revved right out, when it gave extra power very close to redline. So the increased power had much to do with the extra revs afforded by the short stroke motor. But going short stroke isn't really an option.

The head flows extremely well and apart from minor cleaning up and port matching forget heavy modification if you want to street the car. Really there seem to be few areas that can be worked: induction/injection and cams.

Cams are and interesting proposition, as the aim would be to fatten the upper-mid range of the torque curve rather than shift it too much higher. From my motorcycling days one way of achieving this was almost grinding a 'cheater' cam profile. Essentially duration and overlap were left pretty much unchanged but the valves were accelerated open and closed more quickly to increase the duration at or near maximum lift. This type of modification can be hard on the valve train and valve springs may have to be uprated and great care be taken in the design of the ramp section of the profile (this eases the valve off and on to its seat).

Other posts have decribed great success in modifying the induction side of the engine with the most radical fitting ITBs and programmable EFI such as Megasquirt. A friends track car has higher compression (racing fuel) modified cams and still uses the stock bosch CIS-E system with the slots in the fuel distributor remachined to match the timing changes. The car makes about 240-245bhp, after all the stock EVO II uses CIS-E. Although to go further custom ITBs and plenum with EFI is required.

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Cosworth Benz- 16 valve heart, DTM pedigree

if you have a broken valve you will probably have some damage to the piston as a minimum,

good luck

tom w

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.