VWDiesel.net The IDI, TDI, and mTDI source.
Engine Specific Info and Questions => IDI Engine => Topic started by: Jetmugg on October 21, 2013, 12:21:30 pm
-
I'm going to start a thread, and attempt to document this process.
I'll be picking up a 9a (2.0L, flat-top pistons) this evening, with the goal of building a hybrid gasser/diesel engine, probably with an AAZ head.
Wish me luck.
Steve.
-
Been done, the pistons are NOT NEARLY tough enough..
the last one i saw, was a 1.8L gasser, diesel head, and it lived all of 300 miles..
-
If this one lives 100 miles, I'll be happy.
Did the 300 miler melt down a piston, or break it?
Thinking about thermal coating the top of the pistons.
Steve
-
What's the bore/stroke on the 9A? Actual diesel pistons are a near necessity. If you can find a set of diesel pistons you can somehow cram in to the block you might be able to do something. Remember, all the VW diesel pistons actually protrude from the block a small amount to fill up the area of the head gasket. Most gasser pistons are the opposite. All the IDI pistons also have an area cast in to them to direct the flame out of the prechamber too. TDI pistons of course are completely different as they have the combustion chamber in the piston itself.
The other one we saw on here a while back had dropped its compression down to around 130 PSI, not enough to light diesel anymore.
-
Bore and stroke of 9a are 82.5mm and 92.8mm respectively.
The 9a pistons are essentially flat-topped, and protrude from the block a small amount, albeit not as much as diesel pistons. The values I've seen are in the range of 0.016" of protrusion.
Modifying some other pistons is definitely a possibility, as is "decking" the block a bit. I'll have to do some calculations to figure compression ratio.
My 1.5L / AAZ "Franken" engine has somewhere in the range of 17.5:1 compression. While it's certainly smoky on a cold startup, it is making good power on 30psi boost.
-
If this one lives 100 miles, I'll be happy.
Did the 300 miler melt down a piston, or break it?
Thinking about thermal coating the top of the pistons.
Steve
Broke the ringlands and rings..
Gasser pistons dont have much "meat" between the ringlands, and they dont have the stainless steel insert in the top ringland either..
diesel pistons are MUCH beefier than gasser units, and have over twice as much material between the top, and second ring..
you HAVE TO use diesel pistons, and they dont make one in the 2.0L bore size AFAIK..
if you want a 2.0 diesel, then bore out an AAZ...
-
This is CRSMP5's back woods home-brew idea of a cheap stout way to build a fire breather.
I think you'd be 20 steps ahead to START with an ALH block and rotating assembly and upgrade from there.
-
Yeah, find a diesel bottom end. Gasser is waste of time and money.
-
Thank-you/
-
1.8 is not flat top... has a V milled into it and makes a weak spot...
they make forged 9a pistons.... $$$$ yes.. but if it pulls good #s on the stock ones... why not then invest? pre testing fun...
it is cheap experiment.. 9a value very little vs a aaz bottom end.. hell cheaper then worn out 1.6 diesel ones...
i think will last a few thousand... i think 5-30 with stock 11mm tty headbolts and 30psi... im going to try to greanade mine with nos/propain mix though before that... i want to see what is the weak part.. :P
-
Could you find a used set of diesel pistons and get the cylinders machined for inexpensive sleeves???
-
The conventional wisdom may be correct, that this is not a worthwhile adventure, but it still doesn't cost anything to dream.
I'm poring over lists of commercially available pistons, rods, etc, trying to come up with a combination that's worth trying.
Those Ford 1.8TD pistons look reasonable. Finding a set of connecting rods suitable for that application is a different matter.
For now, the fun is in the search.
Steve.
-
The conventional wisdom may be correct, that this is not a worthwhile adventure, but it still doesn't cost anything to dream.
I'm poring over lists of commercially available pistons, rods, etc, trying to come up with a combination that's worth trying.
Those Ford 1.8TD pistons look reasonable. Finding a set of connecting rods suitable for that application is a different matter.
For now, the fun is in the search.
Steve.
there was someone who put a set of these in an aaz a while back.
-
he is doing speed passes on salt flats.. 100 miles = 10 years of life...
i am the idiot who plans to dd one... and i am not worried on the pistons...
knowing how a 8v piston is.. for a 9a style block.. audi engine.. if that material is in the piston.. aka they have dish.. i see no reason a flat top piston will have a issue..
to diesel the pistons = different rods of custom make.. rember this block short like a 1.6.. not tall like a aaz/tdi...
audi short block 2.0 revs better then same set up with a 2.0 tall block.. but the torque on the shorty is less then the tall one.. ive built both on cis with no knock sensor.. why they went to the taller block..
for the at the wheels #s of his 1.5 set up.. which is impressive.. i think him just changing bottom ends will be much like when the gas crowd went from 1.6 to 2.0 modded bottom ends back in the early 80s by people at tt and such.. they had the 1.5/1.6 mastered.. but worked the bottom end up to 2.0... had crank failures and such... with a real 2.0 bottom end.. those weaknesses resolved..
the 1.8s i know were tested had issues of blowing fiber head gaskets by the areas of the piston V cut.. this predated metal aaz gaskets.. then aaz born.. so no one went down 2.0 that i know of... but 2.0 resolved the v cut piston...
its a giggles test.. very cheap to try.. 9a 1/4 price of aaz needinf a rebore... he would imo be foolish to not swap oil pump, im shafts and add the vac pump.. bolt his current goodies to it and give it a test to see how it runs.. then decide if he wants to chase it and throw $ at it..
i would be very suprised if it did not work... question is how well.. sad part is if it works very well... and vs gold dipped diesel crap be nice to have a cheap option.. you all shpould incurage him... he will do way more # proving then i will.. im going with drive it to break it aspect... not going to dyno mine... unless i cannot blow its head off... then i will to see where nos and propain take the numbers... while still tryimg to blow the head off... that will be vid day as till blown ill feel as if i failed..
his #s with the what did it take for me to break it = win.. mine will not be rebuilt... stock rings and all.. mine was running bottom end...
-
http://www.vwdiesel.net/forum/index.php?topic=19163.0
-
Thanks for the link, RJ.
Based on the dimensions that I have found, the compression height of the Ford 1.8TD pistons is 45.65mm. To work in a 9A block, I think that would require a custom set of "shorty" rods, regardless of which crankshaft is used (86.4mm stroke or 92.8mm stroke).
Not impossible, but not regularly available, either.
Using the ABA block, it appears to be plausible.
-
Why not to use 144mm AAZ or TDI rods? When using 92.8 stroke crank, pinstons would be placed only 1,35 mm lower compared to AAZ. That depth can be easily milled off from the block deck. Been there done that! Maximum depth, what I have seen was 9mm :). It was 1,6TD block used to make small displacement gasser racing engine.
-
Perhaps I'm missing something in the dimensions, but I don't think so.
The 9a block is 220mm from c/l of crankshaft to the top of the deck.
With 92.8mm stroke, 144mm rods, and 45.65mm compression height of the Ford 1.8 piston, that shows me.....
(92.8/2) + 144 + 45.65 = 236mm, which would put the top of the piston 16mm up past the top of the block.
-
You are missing the point. If you go with all the custom stuff it would probably be less expensive to go full on aaz with a bore job to get to 2.0. The 16v pistons are flat top not notched like the ones RoR was talking about. If you get a cheap decent condition 9a bottom throw your head on and run it before and see if it works out. If it does then get the forged pistons that crsmp5 is talking about for 600 and let it rip.
Otherwise I think aaz will be cheaper than the 9a hybrid ford piston thing that might or might work.
-
my mistake! I thought that 9A had also 236mm height block like ABA.
-
http://www.vwdiesel.net/forum/index.php?topic=12486.20;
http://www.vwdiesel.net/forum/index.php?topic=15610.0;
-
You are missing the point. If you go with all the custom stuff it would probably be less expensive to go full on aaz with a bore job to get to 2.0. The 16v pistons are flat top not notched like the ones RoR was talking about. If you get a cheap decent condition 9a bottom throw your head on and run it before and see if it works out. If it does then get the forged pistons that crsmp5 is talking about for 600 and let it rip.
Otherwise I think aaz will be cheaper than the 9a hybrid ford piston thing that might or might work.
I get it - the only real way to make the 9a deal cost-effective is to run it basically as-is and see what happens. I was just checking around to see if there was some combination of oddball parts that might also work. As you said before, it will run - but how well and for how long.
On a somewhat related note, for next year, I'd like to up the ante on my AAZ head. I'll send you a PM about the cylinder head guy you used in Ohio.
Steve.
I think I have enough parts to assemble a complete AAZ head, in addition to the one that's already on my 1.5L, with the exception of 1 hydraulic lifter.
-
RJ - that 2.4 piston, 1.6 block stuff is pretty creative. ;D
Those Chevy rods with Honda journals are some pretty trick goodies, too. I'd like to find a set of those in my Halloween trick or treat basket.
Steve
-
You could use your aaz head on the 2.0 deal and get a built 1.6 head for your 1.5 engine. I have a stock cam and at full lift my head is flowing right at 150cfm. Alcaid has an aaz head with a custom cam that ultimately flows more, but at the stock lift my head is flowing 10 cfm more than his. The 1.6 head my machinist and I think have a better port design than the 1.9 aaz. Also IIRC the biggest valves you can put into the aaz are 38mm and my 1.6 head has the 40mm.
-
Honda journal rods are tried. Too small big end for diesel piston pin, exploded one engine.
-
Honda journal rods are tried. Too small big end for diesel piston pin, exploded one engine.
Too small on big end, or too small on small end?
-
Oh, sorry. Too small small end. This is what happened.
(http://www.kotinet.com/matti.farm/Scirocco/Moottori/IMG_2873.jpg)
-
Thank you for the clarification. That photo is an ugly sight. :'( Any ideas about what the details of that build were?
I figured that the big end was probably OK, due to the fact that they are used in NASCAR type applications, very high RPMs, Chevy sized journals.
The large diameter of many diesel piston wrist pins is certainly a challenge. Our VW's seem to be on the small side of what's used in common practice for small diesel engines. The small Ford and Opel diesels are in the range of 26-27mm for the wrist pins.
-
1.8 is not flat top... has a V milled into it and makes a weak spot...
they make forged 9a pistons.... $$$$ yes.. but if it pulls good #s on the stock ones... why not then invest? pre testing fun...
it is cheap experiment.. 9a value very little vs a aaz bottom end.. hell cheaper then worn out 1.6 diesel ones...
i think will last a few thousand... i think 5-30 with stock 11mm tty headbolts and 30psi... im going to try to greanade mine with nos/propain mix though before that... i want to see what is the weak part.. :P
11mm block WILL NOT take 30psi @ 20:1 compression
PCP will be WAY too high, and you will blow the head off/crack the block..
ive done it before! and i used a diesel block to start with!!
the forged gasser pistons will still not have the toughness of a stock diesel piston...
STAINLESS RINGLAND INSERTS!!!
-
Probably not stainless steel, but more likely a Ni-Resist cast iron
On another point, does anyone know the volume contained in an AAZ prechamber, with a glow plug and injector installed? Trying to do some calculations.
-
I used to, it is in the FAQ somewhere. IIRC the volumes were like 1.5 was 18cc and the 1.6 N/A was 18.9cc and the 1.6TD was 18cc and the 1.9aaz was 19.9cc. They varied little between them. I will do some FAQ searching as I think that is where it was and I know it was discussed on here.
I had a friend in ohio with a turbo VR6, 11mm head bolts and it took lots of boost, like 20psi or something. He drove it for almost 50,000 miles and sold it. I have another friend with a 1.8 8v GTI, runs a 12.57 in the 1/4 mile, stock head bolts 19psi from a 18t turbo and a 50hp nitrous shot on top of that. He has raced it for at least 15 years with different power setups. The 11mm bolts and block will hold, just not a 1.6 or 1.5 diesel block, they just seem not to hold up as well as the others.
-
http://www.vwdiesel.net/forum/index.php?topic=12633.0
so I was way off...you will have to look into exactly what they are saying as some used different methods to measure them.
-
Hmm, I tried to determine the volume through dead reckoning calculations and some minor assumptions. I came up with about 20cc's for the AAZ pre-cup volume.
I'm messing around with different pistons that might work in a 9a block, calculating C.R.'s.
I'm actually thinking that the 9a flat-top pistons would give a little bit too much C.R., based on the 92.5mm stroke.
Steve.
-
Sorry, 92.8 stroke.
-
I could tell you what I did to mine, but that would be in PM's :D
-
why i keep commin back to the idea of a new head shim.. :P
a aba metal gasket = min thickness as any thinner pistons would hit the head..
then you have a 1 notch aaz one... a nice new piece of steel or copper in a new thickness = win... zip the silly rivitsd off that hold the gasket and shim together and your set.. :P this is what they did with the turbo vr6 project headgasket... to drop compression..
http://www.cometic.com/ is a place that makes speciality headgaskets and shims... 9a, aba listed there... different thicknesses for turbo apps and such... when me and mr no hair were discussing vr6t stuff.. he hooked me up with this place.. $$$$ yes... but you have a machine shop to do same thing... :P make new shim... :P
what happens if you double up the aba shim?
11mm headbolts.. if arp studs used are not a issue.. only a 1.5/1.6 thats been KNOWN overheated to blow a head gasket is weak.. if it cracks the head from heat.. the 11mm block 95% of time cracked... when you goto torque it... supposedly arp studs thread further in then 11mm head bolts...
9a.. i doubt was hot.. not a issue... unlike the mid-lay 80s.. 1.5/1.6 11block histories are gone.. and i knew what it took to see them crack then.. now.. who knows if it been hot.. unless your like me runing ssame 11mm block since 90... and knew its history from previous owner at that.. :P
also if you mill in the micky mouse ears on top of the flat pistons you loose cc too.. so calculate that..
-
I'm currently keeping my eyes open for a scorching-hot deal on a set of forged flat-tops, "just in case".
-
I'm currently keeping my eyes open for a scorching-hot deal on a set of forged flat-tops, "just in case".
the money you will have to dump into a 9A, will probably be MORE in the end, than just starting out with a slightly more expensive 1.9 bottom end...
Forged slugs are $$$, and not designed for 25:1 compression..
i still think diesel pistons would be tougher/more durable than forged gasser slugs..
-
The diesel slugs would almost certainly be more durable. They are engineered to last hundreds of thousands of miles. This deal will not be about durability.
I already have the 9a short block, and I'm not into it for much $$$. It was an abandoned project, has stock sized but honed bores, ARP main studs, ARP rod bolts (re-sized rods), and a polished crank. All new bearings, ring set, and gaskets were part of the deal.
A set of STD sized forged flat-tops, a little time on the Bridgeport, and I'm in the game.
This thing can be a total time bomb and still be a success. If I can get it to last at least 6 miles, 2 of which must be over 129 mph, then I'm a happy camper. I don't want to blow it up on the first pass, but if it lets go on the last pass, that's totally OK.
The goal is to put it in the SCTA record books.
-
The diesel slugs would almost certainly be more durable. They are engineered to last hundreds of thousands of miles. This deal will not be about durability.
I already have the 9a short block, and I'm not into it for much $$$. It was an abandoned project, has stock sized but honed bores, ARP main studs, ARP rod bolts (re-sized rods), and a polished crank. All new bearings, ring set, and gaskets were part of the deal.
A set of STD sized forged flat-tops, a little time on the Bridgeport, and I'm in the game.
This thing can be a total time bomb and still be a success. If I can get it to last at least 6 miles, 2 of which must be over 129 mph, then I'm a happy camper. I don't want to blow it up on the first pass, but if it lets go on the last pass, that's totally OK.
The goal is to put it in the SCTA record books.
Let us know how it runs..
i WANT you to prove me wrong.. but you will need the important parts of an AAZ (head) anyways, so why not go all the way?
that ARP hardware will fit in a diesel bottom end, fwiw..
-
he has head.... he has a150+hp at the wheels 1.5 td.....
he wants to run his 1.5 class and the up to 2.0 class... the shorty block here lets his turbo oil lines, exhaust and all swap right over... with just a bottom end swap...
if he is pulling as much hp/torque as he has pulled on his 1.5 id expect 2.0 bottom end will be well over 200... for no more then playing with bottom end...
p.s. down in classified some ad i saw aaz bottom end for 400... in cali... id snatch it up too... just as it not dipped in gold price most are..
-
Yeah, I have 2 AAZ heads right now. One built with plenty of Techtonics goodies and a Giles cam. The other is bare now, but should get a nice off-season porting before being built up.
-
Just a little update - I sent JE pistons an email to see whether they could provide a set of forged flat-tops (PN #302339), without any valve reliefs. I figured that would be a good starting point. I'll let everyone know what they say.
Steve.
-
Just a little update - I sent JE pistons an email to see whether they could provide a set of forged flat-tops (PN #302339), without any valve reliefs. I figured that would be a good starting point. I'll let everyone know what they say.
Steve.
its gonna be way easier to source a 1.9 bottom end, than to pay out close to a grand for custom pistons..
-
those valve releifs are less dished then the micky mouse ears if they were milled in.. why i do not worry bout them....