are 2.7 and 1.8t pistons the same dimesions????

[goohead]

anyone im trying to find is 1.8t pistons will work in our cars

[generationjdm]

i herd they were, but not 100% certain

[goohead]

1.8 pistons diameter and cylidner wall are the same ... 80.950 and 81.01 this is on the awm 1.8t

[goohead]

so far i know they are the same:

bore 81mm
stroke 86.4
CR 9.3:1

.....

[MacDaddy]

1.8 / 4 * 6 = 2.7

I would have to say yes.

go 2.2 / 5 * 4 or 6 and you'll find out audi dosn't make new engines at all.

oh, and 4.2 / 8 * 6 = 3.2 TT engine

[goohead]

huh never thought math would have real world use, jk

im just wondering why people pay $$$ for pistons, some dealer i wont name who sells piston kits for our cars for $1400-1700

you can get a set of 6 custom pistons from ross starting at 650

if off the shelf 1.8 will work then thats even better, shorter lead time,

i have listed the above info.

i just need to find the rod length and compress height (ch)

if anyone can help we can all have a much cheaper solution for pistons

i cant stand how much we pay for parts for our cars

[Pete@IE]

They are not the same. The compression height is different and the s4 pistons have valve notches in both sides of the piston so you can turn them around backwards and get the pin offset correct on the other bank. We just finished measuring them all up and are going to have a bunch of sets made and in stock.

[goohead]

hey thanks pete, the 1.8 i thought have 2x valve notchs too but i just found out from searching catalogs that the 1.8 have 20mm wrist pins and the 2.7 have 21 mm wrist pins, that would make sense for the CH

can you confirm?

are you getting some custom pistons made? what price range and brand i might be interested. what kinda of lead time are you guys looking at? ,maybe some special sale w/ your rod combo :)

[Knight_Rider]

They are not the same. The compression height is different and the s4 pistons have valve notches in both sides of the piston so you can turn them around backwards and get the pin offset correct on the other bank. We just finished measuring them all up and are going to have a bunch of sets made and in stock.

coulda swore the 1.8 and 2.7 MAHLES were the exact same, minus quantity per set. i could be wrong, but that's what i found when i was doin my HW.

[Shomegrown]

I wouldn't even think about this. It's just stupid.

Even if the nominal dimension (diameter) was the same, there are possibly subtle differences (pin offset, land clearances, ovality, material, etc) which you'd never see. Those differences are engineered in for a reason.

[JaredVL]

not even close, pin dia. is also different

[dougyfresh]

hey thanks pete, the 1.8 i thought have 2x valve notchs too but i just found out from searching catalogs that the 1.8 have 20mm wrist pins and the 2.7 have 21 mm wrist pins, that would make sense for the CH

can you confirm?

are you getting some custom pistons made? what price range and brand i might be interested. what kinda of lead time are you guys looking at? ,maybe some special sale w/ your rod combo :)

The factory 1.8s only have one relieve cut into them. That is for the center intake valve. The factory 1.8s also use a 19mm wrist pin (except AEB & AMU which use a 20mm wrist pin).

I am unsure what the factory 2.7Ts use.

[goohead]

lol reading is underrated i guess i already posted the wirst pin diff is 19 or 20 vs 2.7 21mm

why would it be stupid? if it was the same wrist pin diameter dome volume and ch is the same then its good to go both are forged

guess its up to pete to post out an awesome intro price for his customs or im order some

[Shomegrown]

why would it be stupid? if it was the same wrist pin diameter dome volume and ch is the same then its good to go both are forged

I could write you a list of reasons why it might not be a good idea, where do you want me to start?

[goohead]

yes please if all things being equal why would it be a bad idea? ch, dome, bore, stroke, rod length, etc. i would love to know,

[Shomegrown]

Like I said, where do I start...

-A V6 block has a vastly different structure than an I4 block. The bore distortion patterns will be different. As a result, the piston ovality profiles are likely different. Use the wrong skirt or land ovality and it's certainly possible to scuff under the wrong conditions. Pistons aren't round...they have very specific shapes depending on the block shape, block cooling, and thermal loading.

-The cooling jacket and cooling system is not the same between the 1.8T and 2.7T. As a result, there may be subtle differences in the piston.

-The ring grooves may be different, and would be very difficult for the average person to measure. One may have uptilt to help with blowby and the other might not. You won't be able to measure this.

-The pin bore profile (also not round) may be different, you probably can't measure this.

-The ring groove heights may be different.

-The piston land clearances and shape may be different. This can have a large effect on oil consumption, blow by, carbon buildup, and high temperature durability. Using the wrong land clearances can mean ring instability, oil consumption, or even scuffing at high temperatures.

-Can you be sure that the thickness of the material in critical sections like the piston crown and skirt is identical? The 1.8T has a lower redline than the 2.7T so it may use less material on the pin lugs and may be weaker.


-Lots of materials can be "forged". You'd have to check the alloys are the same too.

-Do the oil squirters on the 2.7T and 1.8T deliver the same flow rate? I don't know and I bet you don't either. If they don't, then the pistons may have different shapes once again.

I could go on. Pistons are EXTREMELY application specific. There are many subtle differences which are engineered in after thousands of hours of development. Small changes can have huge impacts on performance. Just a few microns or an angle of minutes can mean the difference of a piston working or not.

Bottom line, if they don't share the same part number, there are likely IMPORTANT differences between them. Car companies are constantly looking to save money, and if it made any engineering sense to have the same piston between the two engines, they would do exactly that. It's stupid to use 1.8T pistons because you're blindly guessing that it will work right, and you have a lot to lose if it doesn't. You're better off using pistons engineered for your application, unless you like to gamble.

Heck, the 1.8T itself has more than 5 different pistons used depending on power output and calibration, even though the bore, stroke, block, compression ratio, and rod dimensions may be exactly the same.

but hey dawg, wut do i no its not like i design pistens or anything

[goohead]

im talking about aftermarket forged pistons for the 1.8 and 2.7, much of your arguement dont apply, if you go aftermarket you will have alot different specs on ring land and such, much of will not make a difference if you have proper specs and clearance.

-The cooling jacket - i dont understand how cooling jackets will effect the piston's cooling?

-The ring grooves may be different - as long as it has proper clearance, it would be fine, use the rings that meant for the piston

-The pin bore - use the pin recommendate from whoever you buy the pistons from, for offset wrist pins just follow manufacture's recommendations for install

-The ring groove heights may be different - if ch is same then it wont be an issue

-The piston land clearances and shape may be different. - ??

-Can you be sure that the thickness of the material- aftermarket


the older 2.7 uses the same pistons as the 1.8, then they changed the wrist pin and ch. for the newer engines call up mahle if you dont believe me



while pistons are not 100% round the acceptable piston roundness is .04mm for oem

any aftermarket piston, wether custom or shelf will have different piston ring lands than the oem.

squirter opens at ~1.3-1.6 bars on both engines

people outside of the audi community swap pistons from similar engines all the time with no problems, alot of the stuff you posted doesnt while has to be looked at, wont make alot of difference if specs i listed are the same.

for example on the 2jz you can swap na and turbo pistons no issues, as they have the same wrist pin size, rod length, ch are different, and you actually go from interference to non insterference w/ the tt's thicker 1.3mm headgasket. the piston ring land are different, but rings still have enough clearance at tdc and bdc to work properly. people been doing this for a long time w/ no issues.

check to see if you have proper clearance to counter weight and squiters and your all set.



again w/ aftermarket just use the manufatur install and ordering guide and you will be fine

[Shomegrown]

im talking about aftermarket forged pistons for the 1.8 and 2.7, much of your arguement dont apply, if you go aftermarket you will have alot different specs on ring land and such, much of will not make a difference if you have proper specs and clearance.

If you're talking about aftermarket pistons (which your original post doesn't specify), then the only reasonable thing to do is contact the piston manufacturer. They'll tell you exactly what the difference is between the 1.8T and 2.7T applications. That's probably more prudent than asking a forum full of numbskulls.

-The cooling jacket - i dont understand how cooling jackets will effect the piston's cooling?

How the bores are cooled will directly effect the bore temperature. Heat input form the piston goes out through the piston rings and the piston skirt (mostly). Differences in bore temp between engines will effect piston expansion shape and magnitude.

It's not that big of a deal on aftermarket pistons because very little engineering goes into those. They just use loose tolerances which are safe, but not the best for performance. Just about anyone I've talked to with a "built" 2.7T complains of oil consumption issues. That's a combination of a loose piston and the crap rings that usually come with them.

-The ring grooves may be different - as long as it has proper clearance, it would be fine, use the rings that meant for the piston

That's fine. Be forewarned though, every piston kit I've seen for the 2.7T has rings that aren't as good as the stock ones, especially the oil ring. Our engine has a nice 2 piece oil ring with a cast iron body and sharp lands, great for controlling oil. Most aftermarket kits come with flimsy 3 piece oil rings with two tiny rails and a cheap crimped expander.

-The pin bore - use the pin recommendate from whoever you buy the pistons from, for offset wrist pins just follow manufacture's recommendations for install

Fair enough.

-The ring groove heights may be different - if ch is same then it wont be an issue

It depends. Groove height effects ring temp and ringland size (strength).

-The piston land clearances and shape may be different. - ??

Short of posting a print of a piston, it may be difficult to visualize. Different pistons have different designs. Some are guided by the skirt, some are guided by the 2nd land, etc. If a piston is 2nd land guided, the clearance beteween the 2nd land and the bore can effect the blowby and oil consumption. Tight clearance is good for blowby, but can cause hard contact and even seizure under high temps.

the older 2.7 uses the same pistons as the 1.8, then they changed the wrist pin and ch. for the newer engines call up mahle if you dont believe me

It could be, but you'd have to pull up the part numbers in ETKA to prove it.

squirter opens at ~1.3-1.6 bars on both engines

That doesn't guarantee the same flowrate, only if the shape and diameter is the same too.

people outside of the audi community swap pistons from similar engines all the time with no problems, alot of the stuff you posted doesnt while has to be looked at, wont make alot of difference if specs i listed are the same.

for example on the 2jz you can swap na and turbo pistons no issues, as they have the same wrist pin size, rod length, ch are different, and you actually go from interference to non insterference w/ the tt's thicker 1.3mm headgasket. the piston ring land are different, but rings still have enough clearance at tdc and bdc to work properly. people been doing this for a long time w/ no issues.

check to see if you have proper clearance to counter weight and squiters and your all set.



again w/ aftermarket just use the manufatur install and ordering guide and you will be fine

I never said it wouldn't work. I said it's a risk. Heck, using aftermarket pistons in general is a risk as they will NEVER have the same level of development and engineering as the OEM part. You may get lucky and things work out fine. However, it's certainly possible that you'll end up with a piston that performs worse than stock.

[goohead]

i dont know man, if have used aftermarket pistons in other applications and never had an issue, good compression, minimal blowby, noise was the only drawback on cold start, but forged pistons expand more so wall clearance is different.

3 pieces rings never had problems w/ either. gas ports help with the sealing

im shooting for wiseco cause their ringlands are thicker compared to others, on stock pistons the same ringlands are higher up on the pistons, for better mileage and emissions but not so great for performance and strength. thats why the piston damanges i seem on our cars. alot are related to this

[Shomegrown]

good compression

I never said anything about compression. You'd have to have a hole in the thing to not reach factory compression specs.

minimal blowby

How would you know? You wouldn't...as the end consumer won't notice blowby most of the time. Really high blowby can cause oil carryover though if your PCV system can't separate out the oil. This certainly could happen with aftermarket parts.

A long term side effect though of high blowby is higher crankcase pressures...which will cause oil to leak from seals like the valve covers or rear main.

noise was the only drawback on cold start, but forged pistons expand more so wall clearance is different.

The factory pistons are forged too. However, Audi and Mahle spent enough time designing and developing them that they eliminated excess secondary motion (slap). Aftermarket guys guess and assume a lot of things, which means your chances of a sloppy fit and piston noise is much higher.

3 pieces rings never had problems w/ either. gas ports help with the sealing

I think you're confused here. There are no gas ports in the 3rd groove (where the 3 piece oil ring would reside). If there are holes, it's for oil to drain back into the sump. The oil ring doesn't seal gas, it just scapes oil.

[goohead]

i have always runned a catch can to measure blowby

for the gas ports i was again taking about aftermarket pistons not our oem ones

[Shomegrown]

i have always runned a catch can to measure blowby

for the gas ports i was again taking about aftermarket pistons not our oem ones

You can definitely have high blowby (or higher crankcase pressure) without seeing anything extra in your catchcan.

Blowby is a gas volume. It's often measured in liters/min or CFM. It doesn't have to contain oil. If the blowby is more than the PCV system can separate, it can contain oil. For emissions reasons, modern cars route the PCV system back into the intake. A little oil will carry through and is not necessarily a bad thing.

I know you were talking about aftermarket pistons regarding the gas ports. I was just saying gas ports have nothing to do with 3 piece oil rings (or any oil rings). Gas ports only provide backpressure on the top ring to help seal it to the bore.

[goohead]

huh i guess if you dont have excess buildup w/a catch can you can generally say it healthy. excavate the crankcase pressure w/ a breather and a line from your intake or use your exhaust and you will be fine

im not saying gas ports help with the oil, those were 2 separate sentences, separated w/ a period. i was saying the 3 piece oil rings has worked fine and gas port for compression since you stated there might be compression problems. i think your overthinking it, its been proven to work and provide higher strength. oem makes designs not from a performance standpoint 100%, more like 30% at most, other things they consider are emissions, pricepoint, better gas mileage, etc. some of these piston makers have been doing it for a long time with applications w/ 5x+ more power and stress than our little engine will ever see.

and the blow by and oil consumptions mostly related to your rings and there are alot of people running aftermarket rings without excess blowby and oil consumption. if you want run a gapless 2nd ring and a regular top ring if you want a better seal. alot of domestic guys being doing that for years

but more importantly get the right hone for the application, find a machine shop that has a profilometer so they can give the cylinder the right hone for your ring type. this has nothing to do with the pistons. the roughness (ra) and depth (rz) should be measured. not just guessed. thats why alot of people buy the best of best parts, then go to a cheap machine shop and their engine still sucks. the engine work is just as important if not more important

all im saying is aftermarket pistons work, have been proven to work without alot of negative side effects, i have personally used them without any issues. im not saying the oem pistons are not good

[JaredVL]

I just punched myself in the face

[AMC]

I just punched myself in the face

did it hurt?

it must have.

[goohead]

I just punched myself in the face

why