2.6 stroker 16v owners and technicians! - PeachParts Mercedes-Benz Forum

190evol1 · #1 08-15-2002, 07:37 PM

My friend, Fred, and I dynoed the Bekkers 16v stroker kits and found the numbers quite disappointing. Do the W201 drivetrains lose a certain percentage over 15%? My car read 169.3 SAE NET HP (@ 6200 RPM) while Fred's was 157.4. Choosing that 15% loss, both our cars are just under 200 SAE HP. I thought Bekkers quoted their kit @ 235 as well as being compartive in bore and stroke to the evolution cars.

The only differences between our setup were 272 degree cam versus 256, stock 2.3 headers versus evo 2.5, and stock versus lightened flywheel. By his dyno and cam characteristics, one can tell that his car would 0-60 and quarter mile faster, but mine takes off around 5000 RPM. So for those master technicians that I know race their 16v and the countless other strokers out there, are these really rated below 200 SAE HP? Or are M-B drivetrain loses significantly more than 15%?

Please advise.

Thanks,
Joel

Speedtek · #2 08-16-2002, 01:50 AM

There are too many factors involved in tuning a motor. I can take a wild bet that your fuel curve is off. If it is too rich you will lose HP, If it is too lean you will lose HP. also are your cams dailed in for the RPM range of the stroker kit and also compression is a major factor. Bekker's had their engine finely tuned before it went on the dyno. Some companies run a hair lean to bum up their HP figures. If you give me more info I can tell you what to expect.

Stroke:
Rod Length:
Piston Diameter
Head Chamber CC
Compression Ratio
Camshaft timing
Compression test results
Transmission Gearing
Rear End Gearing
Tire Size and Diameter
Weight of Vehicle

190evol1 · #3 08-16-2002, 07:44 PM

Hi Speedtek,

Unfortunately, I am not running too lean (@14.3 A/F ratio), but it's not ideal.

To answer some of your questions at the top of my head:

87.2 mm stroke
97 mm piston dia.
2576 cc
10.5:1 compression ratio

camshaft spec's:
276 duration
11.1 mm valve lift (max)
2.7 mm valve lift (tdc)

(on my way to get a compression reading)

tranmission gearing (stock 16v getrag - don't remember of hand)
3.07 rear end
215/35-18 tire size (i attribute some loss to the large wheels)
3180 lbs for weight (estimated)

mahalos!

Speedtek · #4 08-16-2002, 08:48 PM

I would measure the drive train loss at 20%.

I believe that running 11 to 1 compression on the 276 cams would be more effiecient. Exhaust may have some effect too not knowing your size.

It would also be good if you could get an A/F ratio per 1k RPM.
also ignition timing. Since it is running slightly rich you could bump the timing 2 degrees more advanced to see what results would be. (what is the TOTAL advance now?)

If you have adjustable cam gears on your car you could play with them to achieve more initial compression.

Good luck!

190evol1 · #5 08-26-2002, 09:18 PM

Here's what Tony @ Bekkers responded with:

Quote:

The 2.3-16V stroker engine with 10.8 CR, 276 cams should deliver 235HP@ 6800RPM at crank, 192HP at rear wheels. If the car is not attaining these ratings check a variety of things, such as air-fuel ratio at WOT ( through oxygen sensor) ignition timing 28-29 degrees, cylinder compression test (220lbs) and leakdown test, cam timing, valve clearance, spark plug gap,etc.

Oh well, back to the drawing board... It's time to fine tune...

I just didn't understand why both mine and my friend's stroker showed similar "gains" from different head technicians...

bjfhmd · #6 08-27-2002, 07:55 AM

FYI:

Model 2.3-16 2.5-16
Cylinder head intake ports 26 mm 28 mm
Header pipe diameter 42 mm 55 mm
(Primary and Secondary)

Your headers, assuming that they are stock, are not helping you much!

190evol1 · #7 08-27-2002, 04:22 PM

Thanks for the input Bernie,

However, if you check the dyno graph - the blue run is my friend's Fred. The major difference between our cars is the cam (as you can tell by the characteristics of the run) and the headers! Can you beleive it? There was no major difference in throughput with the 2.5 Evolution II headers!

bjfhmd · #8 08-27-2002, 08:52 PM

I see what you mean. Hard to believe though. I remember MBDOC mentioning in one of the threads that these cams produce most of its usable power at above 7,000 rpm. At this rev, you can expect decreased engine life.

From my research, I also found out that:
Some differences btw 2.5-16 vs. Evo II
Compression ratio: 9.7:1 vs 10.5:1 (you got this covered)
Rear end: 3.27:1 vs. 3.46:1
Max. RPM: 7000 rpm vs. 7700 rpm
Horsepower: 204/6750 vs. 235/7200
Torque: 240/5500 vs. 245/6000
Top speed: 147 mph vs. 155 mph
0 - 60 mph: 7.5 sec vs. 7.1 sec

I got these figures from a British car magazine long time ago. It appears that in your dyno, you haven't reached the peak of your rpm range when you stopped. (or was it the stock rev limiter?).

Being an owner of a 16v myself, I am routing for you guys to create the ultimate M3 killer. More power to you guys!

Speedtek · #9 08-28-2002, 12:30 AM

Here are the engine specs from the racing version:

1992 AMG EVO II 190e

Compression 11.8 to 1 (short track engine)
Max RACE RPM 10,500 (10,800 is the absolute MAX)
Valves Titanium Alloy - Very thin Tulip
Camshaft Timing 310

HP
During Qualifying 380 HP (shortens the life of the engine)
During Race 335-350 HP

The crankshaft was not fully counterweighted. The counterweights were very thin and strange looking.
They looked like blades. I was told this was to reduce drag.

Valves and rods are "thrown away" after 4 days of racing (2 weekends). recycled metal....I should have grabbed them!

Another important note: Car weight 2180 lbs with driver
1/4 mile time 11.2 @ 135 mph
0-60 2.6 seconds

yhliem · #10 08-29-2002, 05:04 PM

Quote:

Originally posted by Speedtek
The crankshaft was not fully counterweighted. The counterweights were very thin and strange looking.
They looked like blades. I was told this was to reduce drag.

Typically the 2.3/2.5 crank has 8 counterweights on it. in order to reduce inertial mass 4 of these were removed from the EvoII crank.

Less inertial mass requires less energy to rev up and down. this makes it easier/faster for the engine to get to the sweet spot in the powerband. It also helps the engine drop revs faster.

This was all accomplishable because machining technology had gotten to the point where they were able to be far more precise and could afford to 1/2 the number of counterweights

Dan16V · #11 08-29-2002, 06:38 PM

Wow! Those EVO II racecars were amazing!

But, how is an engine like that balanced when the counterweights are removed?

Later,

Speedtek · #12 08-30-2002, 04:25 PM

The counterweights were not removed. They were just (4) odd shaped ones, instead of the normal (8). They looked more like a Medieval Axe blade. Then some of them had cookie bites in the counterweights for balancing. There was something also about crank harmonics that they were just discovering which is why bearings spin at high speeds. It seemed on a 4 cylinder motor the smoothness was not like a 6 or 8 and was very buzzy at high rpms with long stokes and big piston bores. So they did a lot of analysis on the crank and found that to be the culprit. The MB EVO II racing engine is very smooth it doesnt feel like a 4 cylinder. The BMW M3 EVO (4 cyl) engines felt very buzzy at high RPMs also you could tell by the pitch of the exhaust of the MB, The M3 was more raspy. The Benz had a super smooth sound for a 4 cyl.

I miss the EVO racing...

190evol1 · #13 09-05-2002, 11:22 AM

Quote:

Originally posted by Speedtek
The Benz had a super smooth sound for a 4 cyl.

I can imagine! My car stock was almost anemic, but once I stroked it, I swear the engine is "singing". It does live for the higher rev's... But I couldn't believe:

Quote:

Originally posted by Speedtek
Another important note: Car weight 2180 lbs with driver
1/4 mile time 11.2 @ 135 mph
0-60 2.6 seconds

...that they were that fast off the line! You mean there's hope for me? lol...

yhliem · #14 09-05-2002, 05:19 PM

Quote:

Originally posted by Speedtek
It seemed on a 4 cylinder motor the smoothness was not like a 6 or 8 and was very buzzy at high rpms with long stokes and big piston bores. So they did a lot of analysis on the crank and found that to be the culprit. The MB EVO II racing engine is very smooth it doesnt feel like a 4 cylinder. The BMW M3 EVO (4 cyl) engines felt very buzzy at high RPMs also you could tell by the pitch of the exhaust of the MB, The M3 was more raspy. The Benz had a super smooth sound for a 4 cyl.

I miss the EVO racing...

A simple matter of physics. "Natural" harmonics are easier to achieve in engines whose numbe rof cylinders are multiples of 3. which is why the 6 is so smooth. the 8, though smoother than the 4 is still a little uneven.

The Evos were also short stroked, oversquare engines. made it easier to gain revs and generated more power. Bekker's kit is a straight stroker.

Robby Ackerman · #15 09-09-2002, 12:23 AM

Joel

I recently put my '84 Euro model 2.3-16 on the dyno. You are developing quite a bit more power than my stock euro model.

The Euro model has a 10.5 to compression ratio and new was rated at 185 H.P. Mine has 160,000 miles on it.

My max power was 142.5 and max torque was 141.6. Using a 20% loss factor it is developing 178 HP. Not bad considering the mileage, that the car is 18 years old, and the valves can use adjusting. Peak power was between 4200 and 5000 RPM. One advantage my car has is its weight ... according to the EPA certification they weighed the car at 2,560 lbs.

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