IDI vs DI when turboed

[oracle1]

Was hoping someone could chime in on IDI vs DI when a turbo is fitted. I have a reason I prefer IDI because I burn various fuels in my engines and they are more tolerant of thicker fuels. Now I have the Mark 1 running sweet with the five speed and registered, now I want to build a faster donk. Examining various websites I have seen arguments that the 1.5 engine when retrofitted with turbo cooling mods (oil sprayers, oil coolers) and heavier internals can make big mumbo using IDI to instigate an earlier burn as the piston rises on compression stroke. Any info regarding IDI vs DI and the comparisons between the earlier small 1.5 1.6 engines and the later 1.9 would be appreciated.

Also stay tuned for economy figures from the 1.5 and the five speed. I suspect that economy for the 1.5 gld was calculated with a 4 speed in the car. Stay tuned I have only burnt one tank and the odo doesn't work but Ive estimated the K's and it made some very good numbers. Soon I am going to do an economy run with my GPS and lots of K's on the highway and I reckon this little thing is going to be competitive.

Over to the forum

[Preen59]

From what i understand, the 1.9 has the best, strongest internals and the best block. If you mate that with the mechanical gear from the earlier engines like Aydan and Mollins did, i reckon you'd be on fire. I've spoken at length with Aydan about it and it would appear that the 1.9 is definitely a good option. Plus, you can't beat cubes, right?

[gldgti]

The 1.9 is definately the stonger option, but there is a late school of thought that has emerged over on the VW GTD forum that pegs 1.5's with some amazing ability to produce good top end. I will have to investigate this myself (will be shortly anyway, when i turbo the 1.5D cabriolet). In any case, what it ultimately comes down to on our side of the planet is availability and the depth of your pockets.

I suspect the best knowledge for this stuff exists in the nordic wastes, but I cant read any of those forums since in my ignorence I only speak english

The basic thruths however, are these:

>the 1.5 block definately will like to rev a lot further (like, to atleast 6500rpm), but certainly cant take big boost at low rpm
>the 1.6 doesnt respond so sweetly as the 1.5 at the top end of the scale but is quote a bit stronger
>the 1.9 really wont want to be revved much past 5000rpm but will take the most punishment, by far, at the bottom end of the rpm range. unfortunately, the lower end of the rpm range is not where IDI has any advantage over DI.

In my personal expereince, I find that the 1.5 is a much nicer engine to actually drive - smooth delivery of torque. The 1.9 is a bit of a lumpy bastard and seems to make the most of things right in the midrange, making it a great highway car, lots of hillclimbing and overtaking power but not spritely around town. The only time I've driven on a 1.6 was in a Mk1.5 Passat, and it didnt give me much of an idea of the potential for performance since the IP wasnt tuned very well.

I hope that helps some.

BTW - did you ever sort out your brakes?

[oracle1]

I am just going to stick a turbo on the 1.5 and see what happens. I will probably buy a 1.6 block and transfer all the manifolds over. I like the 1.5 it has such a sweet nature. Then I will zero time the 1.6 and put it in. That way everything fits. In the end I bought various second hand brake bits and archived the excess parts, they all fit together. Its running well and very economical.

[gldgti]

good to hear - hope you are enjoying your GLD

[hiho]

My understanding of the 1.5 is that when it is overboosed or cooked, it will almost always crack the block between a head bolt and the water jacket or oil gallery. I recently measured the bolt/head/block dimensions and there is an unused 7-8mm of thread into the 1.5D block that im sure would go some ways to increase the durability of the motor if it was utilised. This is most easily done by replacing the head bolts with studs that go all the way into the block. Oil squirters would be nice too, that is if you are happy to file a slot in the skirt of your piston.

The other issue with the 1.5 is the availability of replacement pistons. Standard size are rare but available however i dont know of oversize pistons anywhere.

I have a baby T2 and k-jet intake manifold that i am tempted to fit to my 1.5D, also I have a 1.6TD project that is getting interesting....

[gldgti]

haha hiho, you thinking t2 on the 1.5 aswell

I agree studs are the go. I also think I wouldnt dream of more than about 15psi and not too much fuel at all (for the EGT's). But if you can go from 50hp to 70 or 80hp even, that would be a huge difference .

My dad has bought oversized 1.5 pistons, I think he ordered them through HSY.