Does AFM bluetop have lower comp pistons than the MAP bltp?

[dreja]

Get the Hungarians chasis VIN and model number and we can look in EPC what market does it belong to. There were the following markets in Europe:

EUG (Europe General)
FRG (Federal republic of Germany W/Emmision control device)
SDZ (Sweden or Switzerland)

[Bad_Dog]

Additional info about pistons.

I measured the bulging in the moddle of MAP bluetop and MAP redtop (non-TVIS) pistons.

The result:

BlueTop - 0.5mm height;
RedTop - 1.5mm height;

I didn't bother with calculations but I would guess that 1mm brings more that 0.3 difference in CR.
So possibly bluetops do not have 10:1 CR.

[firehawk]

Quote:I didn't bother with calculations but I would guess that 1mm brings more that 0.3 difference in CR.

Hmm, let's check that out. The swept volume of one cylinder is 397cm^3, so on an engine with a known 10.3:1 static CR, the effective combustion chamber volume is 397/10.3 = 38.5cm^3. For 10.0:1 CR on the same engine, the volume would have to be 397/10.0 = 39.7cm^3, giving a 1.2cm^3 difference.

If we spread that 1.2cm^3 into a slice 1mm thick, the slice's area should be 12cm^2 - like, say, 2cm x 6cm. Pretty close, but actually feels a bit smaller that what it really is. I'd estimate the dome's top to be something like 7cm x 3.5cm, in which case the difference in volume would be about 2.5cm^3 and CR would be 9.7:1.

For comparison, with 9.4:1 CR the effective combustion chamber volume should be 42.2cm^3 and thus the difference in dome volume 3.8cm^3. Assuming the same area of 7cm x 3.5cm, the height difference to a 10.3:1 CR piston should be 1.6mm, meaning that it would actually form a small dish 0.1mm below the piston's crown. The dish does look a bit deeper than that on the photos, though..

Anyway, I'm not really sure if I got my calculations right so it might actually be a good idea if someone could double-check these in case I made a blunder somewhere.

[Ivan141]

firehawk whipped out the math! Lol.. point is made as far as I'm concerned..I'm putting my money on 10.3:1 c.r. for euro bluetops..

[Apolan]

10.3:! now??!! cmon, we almost setlled for 10:1?! And dreja still says all AFMs have 9.4:1.. this is getting rediculous..

[Ivan141]

dont get so anal about the numbers Apolan...who cares if it's 10.1 or 10.3, it's not like we're professional racers or something. It's the trouble that plagues me very often.. getting to obsessed with little details and numbers that mean next to nothing when you're actually driving. Just be happy if you have a good engine, bluetop redtop whatever, they all are fun enough, and the difference is not worth throwing a fit about imho.

[Apolan]

I need to get anal, as i dont have money to waste. It is a big deal for me to spend money for an engine with 9.4, only to discover that it doesnt work with my 10:1 ecu.. i dont give a fuck about +-3 horsepower, i just need to know wether 10:1 ecu will work strong and flawless on a 9.4:1 engine. thats all. and since nobody can give me a straight-up answer and be 100% sure about it, i will continue to anal-ize this matter. :wink:

[dreja]

Apolan Wrote:10.3:! now??!! cmon, we almost setlled for 10:1?! And dreja still says all AFMs have 9.4:1.. this is getting rediculous..

Take it easy, man

I'm just saying that piston's part numbers of my 4agec bluetop (SDZ market) are different than piston's part numbers in 4age EUG market bluetop...

Considering the El Camino's post (the link is in my first reply) I think that differnent part numbers MIGHT point to 4agec's lower compression.
But I can't say it for sure as I'm not able to prove it...

[Apolan]

thats the thing, nobody can say for sure.

[Ivan141]

Apolan, the difference in compression isnt staggering.. It'l most likely work okay. Especially considering you might be moving to lower compression, which has less risky than higher comp.
Do you know how many people have milled their heads down a bit and used thinner headgaskets with a stock ecu? I can think of plenty.
You can adjust for detonation with the static adjustment of your distributor, so I dont see the problem. Should you get in trouble, I do have a complete kit of 4AGE AFM stuff + ECU collecting dust here.....Which reminds me, my previous engine was originally an AFM engine too... ran just fine on ae86 map ecu and injectors..