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1600ti pistons

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Paul -

All I have is from the Autobooks 1600 workshop manual:

Pistons:

Domed oval centre section to crown

Diameter: standard 3.3055"

1st oversize: 3.3154"

2nd oversize: 3.3252"

Piston installed clearance: .0016"

Gudgeon (wrist?) pins:

Offset from piston centre line: 0.0591"

Pin diameter: White: .8662-.00012

Black: .8662-.00024-.00012

Pin clearance in piston: .00012 to .00032

Pin clearance in small-end bush:

White - 1600 only: .00039 to .00071

White - all other models: .00028 to .00059

Black - 1600 only: .00052 to .00084

Black - all other models: .00039 to .00071

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Probably the same as the standard 1600, I believe the main difference is in the height of the dome. The 1600ti domes are taller. There is a chart somewhere which specifies the dome height on the 1600ti pistons. I'll try to find it.

Slavs

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Henry,

Are you sure you have the 1600ti pistons ? vs. the standard 1600 pistons or possibly the same diameter pistons used by the 1800 and 1800ti. The 1600 pistons have domes about 6mm tall while the 1600ti piston dome are about 9mm tall. The 1800 & 1800ti domes are shorter and can only be used with the 1800 or 2002 crank since they are designed for the 80mm stroke vs. the 71mm stroke of the 1600cc motors.

What is the diameter of your pistons ? Standard bore, 1st oversize etc ?

There is a website in Germany which offers one standard size 1600ti piston.

Slavs

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Not home now but these are nos probably from late sixties.

I will have part number later.

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I thought the 1800ti used the same size pistons as a 2002 ? Thats where my confusion is. I have a NOS set of what Mahle is listing as 1800ti pistons but the diameter is same as a 1600, but the wrist pins on these NOS pistons sit higher than 1600 pistons. I guess thats where the 02 crank comes in.

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I thought the 1800ti used the same size pistons as a 2002 ? Thats where my confusion is. I have a NOS set of what Mahle is listing as 1800ti pistons but the diameter is same as a 1600, but the wrist pins on these NOS pistons sit higher than 1600 pistons. I guess thats where the 02 crank comes in.

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Since we are on the subject of 1600 pistons perhaps someone can help identify mine. I have not pulled them out yet so I don't know length and pin height. The piston diameter is 84.47 mm (2nd oversize, +0.50mm) and I measure the dome height as 5.50 mm. They are marked with a downward facing "E" (Mahle Trademark) with "210" on top and "113" below. It appears the valve reliefs have been modified a bit for clearance/unshrouding. Are these just stock 8.6:1 pistons?

Also, can anyone provide combustion chamber volumes for the 118 and 121ti heads? I was told compression of my 1.6L engine (with a 121ti head) was 10:1, but that may be only due to the head and not the pistons.

From the FAQ BMW OEM Pistons Guide:

Stock 1600 pistons

Compression ratio: 8.6:1

Piston length: 85.5 mm

Compression height: 46.6 mm

dome height: 5.7 mm

OEM Mfg: Mahle, KS, Nueral/Alcan

Thanks, Fred '74tii and '69GT3 with 1.6L engine

post-232-13667667470199_thumb.jpg

post-232-13667667471932_thumb.jpg

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This is a link to a German website which pistures a 1600Ti piston and lists the dimensions.

http://www.oldtimer-motorenteile.com/product_info.php?info=p2428_kolben-bmw-1600-ti--67---68.html

The pistons are 'Bathub" designs. There were no "Piano Top" pistons in 67. Certainly not for the 118 head. The dimensions listed above suggest that the piston is almost identical to the standard 1600 8.6/1 piston except in one respect: The bathub dome on the standard 1600 8.6/1CR piston is about 6mm while the dome on the 1600Ti 9.5/1CR piston is 9mm. The pictured 1600Ti piston also has a couple of vent holes on the piston skirt.

The 1600 stroke is pretty short at 71mm, so you need a pretty tall dome to achieve even a 8.6/1 compression ratio. The 1600 is equipped with the 118 head (The same head used for the 1800 and later 1802). Rather than redisgining an entirely new head BMW saved money and disigned the 1600 pistons with these relatively large domes.

BMW first came out with the NK1500 which has a 82mm bore and 71mm stroke.

Then it released the NK1800/1800 ti with a 84mm bore and 80mm stroke. Head used with this motor - 116 and 118

Then it released the NK1600 with a 84mm bore, but a short 71mm stroke(A bored out 1500). The NK2000 followed with the 89mm bore and the 80mm stroke (A bored out 1800). Head used with this motor - 121

In 1968 BMW redisgned the NK1800 motor which now had the 89mm bore and the short 71mm stroke (A bored out 1600). This motor was also used in the 1802. Head used with this motor -118

The 1600-2 used the 1600cc motor except with the 118 head which has intake valves 2mm larger compared to the earlier NK1600 motor.

All motors were equipped with one of 2 style cranks:

1.Crank designed for 71mm stroke

2.Crank designed for 80mm stroke

All motors use the same length connecrting rods and all blocks have identical external dimensions. This facilitated things greatly and lowered costs associated with design, tooling and production. All motors including the "Ti" motors used the same profile cam. BMW built long duration cams only for dedicated race motors. Otherwise, the "Ti" cars just used the same stock cam. Most customers who purchased BMW's were interested in a smooth running motor. That is why BMW was conservative and did not risk selling a car with a lumpy idle. The main reason for the redisign of the 1800cc motor in 1968 was because BMW was seeking to build a smoother running 1800cc. The shorter strokes are smoother.

The quality of all M-10 motors is exceptional as all cranks were forged and hardened. Only the "M" cars have forged cranks in modern BMW's.

The Mahle and KS pistons are exceptional quality. They were cast for all street cars since forged pistons are notorous oil burners and only designed for racing. Mahle also built the forged pistons for race cars and some Alpina motore. BMW used 2 piston manufacturers: Mahle and KS (Kolbenschmidt).

Slavs

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Interesting, Why would someone do this to these pistons ?

They actually look like the 8.6/1CR 1600 pistons, but with cut-out valve reliefs. Their dome height suggests they are 1600 8.6CR pistons. Someone must have used a radically profiled cam and cut out the reliefs to compensate for the long duration on a high performance cam. However, in cutting out the valve reliefs, they actually lowered the CR. But, this motor might have also had a head which was milled below the acceptable limit to achieve higher compression ratio.

These could also be 1800ti pistons which are also 84mm bore. But, this could be easily ascertained with the piston travel or stroke. The 1800ti will have a 80mm stroke versus the 71mm stroke of the 1600. The 9.5/1 CR1800ti pistons use a dome height nearly identical to the 8.6/1CR 1600 pistons. A higher CR is achieved in the 1800TI, though, with the same dome height because the 1800 has a longer stroke. CR is a measure of the total volume of cylinder and compression chamber at bottom of stroke vs. at the top or TDC point of stroke. Dome height is indicative of the CR but only for a specific motor. It all changes once you start analyzing another motor with a diffrent stroke/bore ration and/or head design. Some people are fooled by the relatively tall dome on the stock 1600 pistons. They say"Man those domes look like 10.0/1 or 11.o/1 pistons". Well, that would be the case if they were on a BMW 2.0 liter motor, but not on the 1.6L motor. You can't compare apples to oranges. People sometimes claim they have 1600ti pistons, but in most cases, they are 1600 pistons.

Slavs

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