so i have a mk1 coupe td, and i'd like to drive it - page 4 - IDI Engine - VWDiesel.net The IDI, TDI, and mTDI source.
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#45 by RabbitJockey on 08 Aug, 2011 08:38
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I wouldn't worry about that nick down by the oil ring, too far down to matter much, but mark it with a spot of felt tip, and avoid aligning middle ring gap with it to be sure.
thats a good idea with the ring gap, i usually just face top ring away from the exhaust side and the precup since that is the hottest 2/3 of the engine i would assume -
#46 by keaton on 08 Aug, 2011 10:53
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been working on porting here and there as i have time, just gasket matching and cleaning things up, i wanna try to take the harshness out of the turn in the exhaust ports but its hard to get in that angle
look how much the exhaust needs opened up holey moley
the intake and what i have done so far, just cleaned it all and smooth transitions i'm not gonna mess with the guide hump just run over it to resurface
stock intake
sorry, not to come in here and piss on your parade but your not suppose to gasket match your ports. you want to port match. going from small cross sectional area to a larger cross sectional area slow the air velocity and hurts performance (intake side).
as far as the exhaust you want to make sure your manifold is not small then your ports. diesels don't have much valve overlap so you don't have to worry about exhaust reservation
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#47 by RabbitJockey on 08 Aug, 2011 14:53
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i have matched the intake manifold to the gasket as well, so the parade has not been peepeed on
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#48 by RabbitJockey on 10 Aug, 2011 19:59
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got the head back today, cost me 385 for all new valves, guides, and seals, plus they setup the valves for me. they also sand blasted the ports, which really let me see a lot of stuff i could have dont better, regardless tho the head will flow better than it did. the mistake i have made, is i forgot to tell them to not resurface the head, and they did. ugh. i really didn not want them to mess with the deck at all. i don't think its their fault but i have also noticed cracks in the prechambers, had they not resurfaced the head this would be an easy fix since i could just swap then out for the prechambers from my old cracked head.
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#49 by RabbitJockey on 11 Aug, 2011 15:46
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ok so here are the pictures of the pre cups, its hard to take pictures of little hair line cracks, but i did my best, what does everyone thing? i don't want a hunk of inconel to ruin my engine after i finally get it back together. and i still have the prechambers from the head i cracked, im not sure of the condition though.
number 1
number 2
number 3
and cylinder number 4
also here is a picture of the head, i was pretty happy with their work and price, aside from them shaving the head i'll have to call and see how much they took off.
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#50 by RabbitJockey on 11 Aug, 2011 20:40
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i would quite love some commentary on the prechamber cracks
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#51 by Patrick on 12 Aug, 2011 03:19
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I wouldn't leave them, I had one come apart once. Not a pretty picrure.
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#52 by RabbitJockey on 12 Aug, 2011 04:15
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I wouldn't leave them, I had one come apart once. Not a pretty picrure.
yes this what i am leaning towards, i don't plan on making this some monster engine since i just wanna get it back together so i can drive the car, but at the same time i am certainly going to run this car hard. -
#53 by R.O.R-2.0 on 12 Aug, 2011 15:16
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those cracks are NOTHING..
ive seen heads come off it MUCH WORSE shape than that, with no ill side effect.. -
#54 by RabbitJockey on 12 Aug, 2011 17:57
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those cracks are NOTHING..
ive seen heads come off it MUCH WORSE shape than that, with no ill side effect..
i spoke with one of the local diesel gurus, he rebuilds tons of these engines. i showed him the head before i took it to the machine shop so he knew it didn't need machined. anyways he said a few hair line cracks are no big deal because the prechambers are made from really good metal. he was a machinist by trade so i definitely trust him. it still really bothers me that they shaved the head just to clean it up, when it wasn't warped and there was nothing wrong with it, but oh well they can't put the material back on -
#55 by RabbitJockey on 09 Oct, 2011 09:46
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well adam and brandon came down, and are helping me with rebuilding the turbo, adam used to work for a diesel shop so hes rebuilt a ton of turbos. What were doing is using the exhaust side, and center section from the vw t3, and then using the back plate, compressor wheel and compressor housing from a mercedes diesel t3. the mercedes compressor is a 45 trim, the a/r of the compressor is .42 but on compressor housings the a/r is quite irrelevant.
for comparison, the vw and mercedes compressor wheels:
the mercedes wheel is on the left, u can the see the small diameter is quite a bit larger, the big diameter is the same. the vw compressor is 35 trim.
and just for comparisons sake, here is the mercedes turbine next to the vw turbine, the mercedes turbine has the same small diameter, but a bigger large diameter. the vw turbine is the standard t3 size, and is the same as t3 fords, saabs, grand nationals, and most anything else that came with a t3. for what ever reason the mercedes t3 is the odd man out with the larger wheel, what effect this has on spool up and flow i have no idea. but i am using the vw turbine wheel and vw .36 a/r exhaust housing so it doesn't matter haha.
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#56 by RabbitJockey on 09 Oct, 2011 18:08
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here is how i have mapped it at 30 psi and reving to 6k, volumetric efficiency at 80% supposedly some where around 180whp, how ever i doubt it will do that much, unless i have good intercooling and very good flowing intake manifold with giles pump. it goes off the map some in the higher rpms, not ideal but the high pressure ratio areas of the compressor maps, are not always mapped because the compressors were not meant to be used on applications with this low of flow and this high of a pressure ratio, so its not necessarily inefficient in those areas, also the choke limit of the maps is generally just where the compressor becomes less than 60% inefficient. loads of people run turbos past the choke limit on here with no ill effects, if we drove gassers where super hot intake air temperatures caused pinging and stuff it would be alot more crucial, but since we drive diesels we can get away with passing the choke limit a bit.
the points on the map represent these rpms in order 1000, 3000, 3400, 3800, 4400, 5000, 5500, 6000
im hoping to have the spool of the vw diesel, with the efficiency and flow of the mercedes turbo. i know a few people have built the
k26/k24 hybrids with poor results, ive looked at the k26 map, and although the 1.6 stays well within the operating range of that compressor it is never in a very efficient part of the map, this coupled with the k24's smaller exhaust housing .30 a/r i believe is what created excessive back pressure which lead to excessive egts. vw t3 exhaust housing is .36 a/r so slightly bigger, and it also has one less blade in the turbine wheel. -
#57 by bgbmxer on 09 Oct, 2011 18:56
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been working on porting here and there as i have time, just gasket matching and cleaning things up, i wanna try to take the harshness out of the turn in the exhaust ports but its hard to get in that angle
look how much the exhaust needs opened up holey moley
the intake and what i have done so far, just cleaned it all and smooth transitions i'm not gonna mess with the guide hump just run over it to resurface
stock intake
sorry, not to come in here and piss on your parade but your not suppose to gasket match your ports. you want to port match. going from small cross sectional area to a larger cross sectional area slow the air velocity and hurts performance (intake side).
as far as the exhaust you want to make sure your manifold is not small then your ports. diesels don't have much valve overlap so you don't have to worry about exhaust reservation
some of this is correct but there is much more to it when boost is involved and other variables. when both sides of your ports are both smaller than the gasket itself matching it to the gasket is fine. smooth transitions will help you more than anything else.
have you ever looked how much material can be taken off just the exhaust? it looks just like that picture you put but going the opposite direction. the air hits a wall. and with the intakes and exhaust manifolds on these cars. even if its not ideal its still going to be better than stock.
one thing i think travis and i both did wrong with are heads is the ports are too smooth. they should be more like a golf ball and have dimples. thats the ideal way. -
#58 by RabbitJockey on 10 Oct, 2011 10:34
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mine were pretty rough but they sand blasted my ports at the machine shop, i'm not bothered by it
http://www.vwdiesel.net/forum/index.php?topic=21630.0 -
#59 by RabbitJockey on 17 Oct, 2011 08:50
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here is a link to someone that built a similar turbo as me, but he used the mercedes turbine wheel in a machined vw turbine housing, im not a machinist so i can't use the mercedes wheel, how ever it looks like he just used a hand grinder to get it right
http://www.vwdiesel.net/forum/index.php?topic=21630.0