VWDiesel.net The IDI, TDI, and mTDI source.
Engine Specific Info and Questions => IDI Engine => Topic started by: saurkraut on April 09, 2009, 12:07:18 pm
-
really? 1.9 rods with shaved 1.6 pistons on them? think it will work? im so tired of looking for 1.5 os pistons, and i really dont want to sleeve my block back to stock. but i dont want to use an 11mm block either. and i have a dead MF block laying around just waiting to get all slutted up..
Yah, thats what I'm currently contemplating. I foreget what the actual numbers are. Best of my recolection is .063" off the top of the pistons, and something to reduce the 26mm holes in the 1.9TD rods to accept the 24mm wrist pins. Its the best of all worlds: short stroke, long rods, TD pistons, oil jets.
see, thats what i wanted, the short stroke and long rods to turn some mad rpms. but i also liked the oil jets in my MF block. i also want to run a 1.9 head. and some crazy single turbo, or a nice set of compounds :twisted:
I've putzed with compression ratio figuring:
The 1.6 head on a 1.5 block yields a CR of: 21.37:1
The 1.9 head on a 1.5 block yields a CR of: 17.68:1
The 1.9 head on a 1.6 block yeilds a CR of: 19.01:1
I wonder if the 1.9 head would have the ignition problems that some folks are experiencing when they put a 3 notch in a 1.6/1.9 head combo. I gues there is only one way to find out....
Rod stuff:
1.6TD rods, center to center, are 136
1.9TD rods, center to center, are 144
Difference: 8mm
1.6 stroke is 86.4
1.5 stroke is 80.0
Difference: 6.4mm
Rod Difference: 8mm
Stroke Difference 6.4
Amount the 1.6TD piston need to be shaved: 1.6mm (.063")
-
im 100% against running a 1.5 block. i wont do it. not for my next build. only reason i used another 1.5 block this time was because it was free. i blew my first 1.5 block to bits with a stock fuel system and almost 40 psi boost. the head gasket even survived better than the block. the gasket blew because the deck of the block got so messed up. i ran over 30 psi to that gasket more than a few times.. and it was just a stock crap fiber gasket.
and why the lower compression? is it that the AAZ head has bigger swirl chambers? i know its not the combustion chamber size, as that is in the piston.
-
My appologies. When I say 1.5 block for the purposes of this discussion, I mean a 1.6TD block with a 1.5 crank and 1.9 rods and shaved 1.6Td pistons. The swept volume will be the same as a stock 1.5 block.
Yes, the swirl chambers get progressively bigger as the displacement was increased. The smallest are in the 1.5 head, the biggest swirl chambers are in the 1.9 head.
Here's a dandy table the Roger Brown put togather:
http://www.4crawler.com/Diesel/index.shtml#EngineSpecs
If the proper thickness head gasket is used, and with the material removed from the top of the 1.6td pistons, the 1.9 head might work. I need to measure the depth of the pockets in the 1.6td pistons. It might be necessary to cut them deeper befor machining the top of the piston as they may dissapear.
-
Would you need to shave the 1.6 deck significantly to use the original 1.5 rods with modded 1.5 pistons?
I've slowly accumulated enough parts to build a second bottom end using the above-described combo.
-
Would you need to shave the 1.6 deck significantly to use the original 1.5 rods with modded 1.5 pistons?
I've slowly accumulated enough parts to build a second bottom end using the above-described combo.
put a 1.5 crank, 1.5 rods, and 1.5 pistons in a 1.6 block. everything fits as it is. no need to modify the 1.5 pistons.. only 1.6 pistons. then you have the beauty of a short stroke 1.5 with the beefy 1.6 block and head. or you could throw a 1.9 head on it..
-
Is there a difference in the pin offset between the 1.6 or 1.9 pistons?
Yes, its in the bently manual. Something like 1.1xmm
-
Would you need to shave the 1.6 deck significantly to use the original 1.5 rods with modded 1.5 pistons?
I've slowly accumulated enough parts to build a second bottom end using the above-described combo.
put a 1.5 crank, 1.5 rods, and 1.5 pistons in a 1.6 block. everything fits as it is. no need to modify the 1.5 pistons.. only 1.6 pistons. then you have the beauty of a short stroke 1.5 with the beefy 1.6 block and head. or you could throw a 1.9 head on it..
But as we all know, fresh 1.5 oversized pistons are very rare. And the oil jet notches in the 1.6 pistons have reinforcing around them. So if you notch the unavailable oversized 1.5 pistons for the oil jets, they may crack.
Its unfortunate that the pin hight is lower than the 1.5 piston, as it takes away from the long rod advantages, and makes it imposible to use 1.6 pistons.
-
Well, if the pin bore is offset differently, then you would want to take that difference into consideration with regard to how much the pistons need to be shaved.
Yup. I should have 1.9td rods soon. I have and extra 1.5 crank. I'll figure out how to rebush the rods to the 24mm pins. I have a fresh first over size TD block and pistons standing by. I'll assemble it and measure stuff. It will be essentially de-stroking a 1.6TD. the only 1.5 part will be the crank.
-
Sorry to threadjack, but my buddy has a couple NOS 1.5 Brazilian Metal Leve piston sets w/ rings. He has std, .5 and 1.0 over.
PM me if I can help!
-Brad
-
Makes you wonder why VW didn't just leave the original dimensions for the crank, piston and stroke alone when beefing up the block?..
-
Makes you wonder why VW didn't just leave the original dimensions for the crank, piston and stroke alone when beefing up the block?..
They had already changed the bore and stroke to make the 1.6 before updating the block.
i thought the 1.5 and 1.6 had the exact same bore size, just less stroke?
-
Would you need to shave the 1.6 deck significantly to use the original 1.5 rods with modded 1.5 pistons?
I've slowly accumulated enough parts to build a second bottom end using the above-described combo.
put a 1.5 crank, 1.5 rods, and 1.5 pistons in a 1.6 block. everything fits as it is. no need to modify the 1.5 pistons.. only 1.6 pistons. then you have the beauty of a short stroke 1.5 with the beefy 1.6 block and head. or you could throw a 1.9 head on it..
But as we all know, fresh 1.5 oversized pistons are very rare. And the oil jet notches in the 1.6 pistons have reinforcing around them. So if you notch the unavailable oversized 1.5 pistons for the oil jets, they may crack.
Its unfortunate that the pin hight is lower than the 1.5 piston, as it takes away from the long rod advantages, and makes it imposible to use 1.6 pistons.
why cant you notch the pistons for the jets? i know of some machine shops that ive spoke with that use 1.6 n/a pistons and just notch them for turbo motors. i seriously think we could notch them and not worry about it. there isnt much load or stress down by the piston skirt. thats where they file off material when balancing them.. so why cant we take a little more off and have ourselves a notch? i think i would take the chance of notching some 1.5 pistons.
-
Doesn´t 1,5 crank have smaller con rod journals than 1,6/1,9?
-
Doesn´t 1,5 crank have smaller con rod journals than 1,6/1,9?
no, all the journals are 50.6mm according to someones bently manual. im pretty sure i got those measurements from sauerkraut. so basically, all IDI diesels, and i know atleast the first TDi's had rods that were interchangeable with AAZ rods. so they must be 50.6mm also.
-
why cant you notch the pistons for the jets? i know of some machine shops that ive spoke with that use 1.6 n/a pistons and just notch them for turbo motors. i seriously think we could notch them and not worry about it. there isnt much load or stress down by the piston skirt. thats where they file off material when balancing them.. so why cant we take a little more off and have ourselves a notch? i think i would take the chance of notching some 1.5 pistons.
I agree -- the material is relatively soft, and it's not like you'd need to remove that much metal to clear the jets.
-
Hope that's OK, because that's the exact process done to the new 1.6 pistons going into my modded 1.5 block. The machine shop said everything balanced out fine (they mostly build high-revving race VW gasser engines and had never been asked to balance a diesel before!). Oil pump is a later (higher volume) unit listed for Euro-Audi w. hydraulic followers, so it should easily keep up with any extra oil the piston squirters might consume.
Of course I'll thermal coat & polish the (non-TD) piston crowns before assembly; still thinking about doing the anti-friction moly-coating on the piston surfaces & cylinder walls. I have confidence that the Raceware 11mm head studs will do the clamping.
My question in keeping with the broad range of the topic of 1.5L-building, concerns the rod bolts. While the rods have been (by the same performance-oriented machine shop) checked, found to be straight/re-usable, re-bushed/sized, should the rods get new bolts. Is it really worth going to ARP's or Raceware's rod bolts/studs on an engine that is not going racing (given that its fuel efficiency & longevity are of higher priority than raw power), will be intercooled, likely not be pushed beyond 10-12 boost, but may be called on to do some light trailer towing?
TIA, gurus
-
Is it really worth going to ARP's or Raceware's rod bolts/studs on an engine that is not going racing (given that its fuel efficiency & longevity are of higher priority than raw power), will be intercooled, likely not be pushed beyond 10-12 boost, but may be called on to do some light trailer towing?
TIA, gurus
i think some of the older vw engines had re-usable bolts, but the newer ones definitely have stretch bolts. using the studs will reduce power robbing 'flex', and give you the added peace of mind of knowing it will last.
-
Doesn´t 1,5 crank have smaller con rod journals than 1,6/1,9?
no, all the journals are 50.6mm according to someones bently manual. im pretty sure i got those measurements from sauerkraut. so basically, all IDI diesels, and i know atleast the first TDi's had rods that were interchangeable with AAZ rods. so they must be 50.6mm also.
Ok, I had to check from book :) Klik (http://www.kotinet.com/matti.farm/img01.jpg)
-
why cant you notch the pistons for the jets? i know of some machine shops that ive spoke with that use 1.6 n/a pistons and just notch them for turbo motors. i seriously think we could notch them and not worry about it. there isnt much load or stress down by the piston skirt. thats where they file off material when balancing them.. so why cant we take a little more off and have ourselves a notch? i think i would take the chance of notching some 1.5 pistons.
Here's a couple of pictures of the oil jet notch in the 1.6TD piston:
(http://i192.photobucket.com/albums/z236/dieselkraftstoff/SSPX0457.jpg)
(http://i192.photobucket.com/albums/z236/dieselkraftstoff/SSPX0458.jpg)
As you can see, the notch is reinforced. It also appears that there is a steel plate just below the notch.
You might get away with notching the 1.5 pistons, but I'm going with the turbo pistons. Heck, I'm even nervious about pulling .063" off of the crown. :shock:
As far as the piston skirt being a low stess area, I don't know If I'd hang my hat on that. What I've seen in raceing two stroke engines, good forged Austrian made Elko pistons would develope stress cracks in the skirts directly in line with the piston pin boses. Right where the oil notch is in the 1.6TD pistons.
Also, I can't pass up the opportunity to use the long 1.9 rods with the short stroke 1.5 crank.
Just because some machine shops would do it doesn't hold water either. Some of the stuff I've seen them do would curl your hair. Like some won't measure piston protrusion and will toss in a three hole head gasket and call it a day.
-
you got it right tho. 2 STROKES!! they turn twice, maybe 3 times what we are going to be turning ours. and they dont have nearly the skirt depth that we do. i think vw pistons are really long for how big they really are. long skirts keep the piston more stable in the bore. less of a chance for piston slap.
as fo me, im going to notch 1.5 pistons and wind the piss out of it. :twisted:
-
I must agree with saurkraut on the piston modding issue...
During my racing days I have seen plenty of cracked piston skirts although on higher reving engines but the last ones was "only" revving just pass 6000 rpm. Anyway after 10 hours you would see cracks going straight down on the skirt. This was a 2 stroker 1 cylinder 650 cc used for sidecarmotocross.
The normal changing interval was 10 hrs.
So I would be very careful to not make any sharp edges or even scratch marks on the skirts.
But as I say this is just my opinion...
-
ok, well you guys have good points. but that doesnt even come close to swaying me not to notch some pistons. i know its been done. and i know it works. this isnt a hair brained idea i thought up, i heard this straight out of a machinists mouth. he used to rebuild lots of VW diesels. i asked him about a new set of pistons for my td motor and he said he uses n/a pistons and just notches them. cut a n/a piston in half.. i bet anything there is steel in those pistons too, just not visible. why is a simple notch going to cause piston failure? honda CRF450R dirtbikes dont even have any damn piston skirts. there piston is just over an inch tall. and thats from the bottom of the skirt to the top of the crown. and there is hardly any material in there. i know theres no steel reinforcements either. and those engines turn 14,000 rpms. and yes.. they are a 4 stroke. i think you guys are just too cautious. maybe ill build a 1.5/1.6 out of a n/a block first. just to make sure things go alright. and i would still notch the pistons just to see if anything happens. then atleast if i break a piston, its not a good one, and its not gonna be my turbo block either. basically an experimental engine. but i have spoken my piece. and im still going to notch my pistons. you wont need nearly as deep of a notch on a 1.5 piston either. lots less stroke.