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Model specific boards => Golf mk2 => Topic started by: Brighouse-gti on 16 December 2014, 15:40
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So its like this, I want to build an engine up, and am pondering this;
Mk3 1.9 tdi bottom end(1Y)
Mk3 1.9 tdi gearbox(1Y CHC)
Mk2 1.8 gti top end(digi of PB engine) big valves, gasflowed, uprated cam
KO3 turbo intercooler bla bla bla
.... to someday fit into my mk2. My thinking is it should marry up together, (top n bottom) and will just fit straight in (mountings wise), but that's pretty much as far as my amateur knowledge goes! Just looking for some advice, as always, or for someone in the know to say, hold on a minute, that won't work! Or of it does, yeah but you'll have to do a + b or it won't work.
Ta for any info!
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What fuel?! Deisel? Why?
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Diesel, what's that?
Petrol my good man!!
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Unless you know something I don't, you cant run petrol through a diesel bottom end, they work in completely different ways... Hence why people who stick the wrong fuel in their car end up at the side of the road.
Petrol needs a spark, your diesel bottom end has no way of providing a spark. Thats my (possibly very wrong) take on the matter.
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Waspy: sparkplugs (or glowplugs for CI engines) are in the head, not block.
Brighouse-gti: are you sure the diseasel bottom end will physically line up with a PB head? I don't really know why, but my gut feeling is that it probably won't. Spacing of bore centres, headbolt holes etc?
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I'm pretty sure it should work, or there is a combination that should, although I think the combination I've said is correct.... reason being I met a lad a while back who had done such a conversion, and I almost certain he said he'd used the mk3 diesel bottom end combined with the mk2 head, and what he'd done was use the turbo setup from a cosworth. He also said something about it being like s**t of a stick and putting a big smile on your face when you put foot down!!
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Even if it did fit, you would have to put a big spacer between the diesel block and PB head with two head gaskets. Diesels run a 20:1 compression ratio, normal PB is about 10:1 otherwise pistons would hit the valves. Turbo'd engines need compression ratio reduced to about 8:1 as when turbo'd the compression is increased to around 10:1 (you can't get high enough octane fuel to run more than about 10:1 unless you use Avgas) otherwise the fuel pre-ignites (self detonates). You need to reduce the compression ratio for a turbo so using a diesel block would be counter-productive unless you change the pistons & con rods. I think Turbo Technics used a head spacer and double gasket on their PB turbo conversions.......?
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lol my bad.
On another point, why, other than something different?
Sounds like a complex way of getting bhp. A boring old 20vt is also like sh!t off a stick (and is tried and tested)
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The mk3 1Y block is a tdi block so surely it would have a low compression ratio anyway no? Part of the reason behind such a conversion is that I cant see it needing a loom swap, which would be the absolute bonus as when it comes to the electrics side of things with cars I'm almost useless. Maybe a remap or something or very little in the way of electrics but you can see where I'm trying to go with this..
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The tdi block only has the compression reduced to about 18:1, so still very high. Tdi wiring/ecu would have no control for the spark & timing and Tdi diesel injectors are way different to petrol. I'm not saying its impossible but it does not seem a logical way to go, also petrol turbo gasses burn at much higher temperature than diesel so you need special oil cooled pistons to get the heat away.
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Just been having a butchers round other forums, found a post by some geeza wanting to know if he could swap his G60 bottom end for a bigger bore bottom end to gain some bhp....
Originally Posted by gazw
Hi, can this conversion be applied to the G60 aswell?
There was a guide to this in golf+ quite a while ago, iirc you need to use a block from a diesel van and do a slight bit of modding to it, i will see if i can find the mag in question
Maybe I'm going down the wrong route with the 1Y block, and shud be looking at a PD block??
Also as I'm always looking to learn, why is the compression ratio so high in the mk3 tdi block if normally you'd want a lower compression to allow for the extra umff from the turbo? Yes I'm also quite useless with my knowledge on Diesel engines!
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As said really, the max compression ratio in a petrol engine is perhaps 11:1 with modern management, turbo boosting makes the air already compressed so by making it 8:1 it ends up between 10:1 & 11:1 in the cylinder depending on the boost level, normally aspirated diesels are over 20:1, some up to 22:1 so if you add a turbo you need to knock this back to around 18:1 to keep the compression sensible. Diesels need a very high compression as they are a compression/ignition engine, the compression has to be high enough to raise the temperature in the cylinder high enough to ignite the mixture but must not occur too soon in the cycle or it will fire up too soon. When very cold even 22:1 might not cut it for starting hence the need for glow plugs. Diesel blocks & cranks are normally stronger due to high torque from diesels but the pistons are no use at all for a petrol turbo.
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Spot on that Jezza, great description! Had a chat with the mechanic at my work today, he basically said the same thing. He is a bit of a landrover nut job, and he was saying at some point, when landrover was landrover, and not a box with a ford engine, that for some of the engines they built they used the same block for the Diesel engines as petrol engines. The only advantage he said of trying to do such a thing for a petrol engine, is that the bottom end and rods are a lot stronger in diesel blocks, so in theory could handle more abuse, I'd just have to swap the pistons as the diesel pistons arent concaved, which helps lower compression, as you pointed out Jezza. He said he's heard of such things being tried out in Motorsport (when he was a lad, many moons ago). He then went on to say that I could use a dizzy from an old Peugeot, insted of trying to drill out the block, as it fires from the camshaft. By the end on my dinner break, he was more into the idea than I was! But there's light at the end if the tunnel now! Going to search into this some more and see what I can dig up!!
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I've got a G60 large port cylinder head for sale if your interested.
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I've got a G60 large port cylinder head for sale if your interested.
Hhmmmmm maybe interested, depends what your asking for it??
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Just curious, how did you get on with your 3k cut out issue?
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The 3k issue seems to be sorted, I should post up!.. Replacing the air intake boot seems to have done the trick, haven't had any issues since. Have had some heavy rain since so the water in the ECU theory kinda has gone out the window!
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It would make more sense to build a 1.8 bottom end with lower compression pistons
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I've got a G60 large port cylinder head for sale if your interested.
Hhmmmmm maybe interested, depends what your asking for it??
Open to offers on it mate. Have it advertised at 150.