RPM limit

[NintendoKD]

I understand that the principle is different, but what is the RPM range of these engines?  I'm talking about the 1.5 and 1.6 in particular and the difference between the two.  I guess that the real question I am eventually trying to get to is, that is the benefit of a shorter stroke outweigh the displacement of the 1.5.  I understand that there is a power difference in the 1.6 from the 1.5 but there is a method to my madness.  I have been thinking about the frankenmotor, would it be possible to shave the block to achieve higher static compression without valve slap or any other maladies?  or is there a way to essentially reduce the stroke of the 1.6 by way of shaving the piston to give back higher revving capability.  Currently the verdict on building a 1.5 rot. assy. with a turbo 1.6 block and an aaz head is impossible due to too low of static compression ratio, so are the benefits "if any" worth looking into other solutions?

thanks,

Kevin

[Rabbit on Roids]

basically, you cant rev a VE pump enough for it to matter if the bottom end is 1.5 or 1.6. you can get only about 7000 rpms out of a pump if i remember right before rollers start skipping and it doesnt pump properly. think of it this way, they are basically the same bottom end in gas form, but just with different pistons and head (basically), and those engines turn between 6500 (stock redline) and anywhere towards 8500-9000 when they are built to the bolts. so, the bottom end will basically not care if its a 1.5 or a 1.6 or what. the only reason im so partial to the 1.5 is because it seems more like gasser power to me, and it has much better throttle response than my 1.6TD had. but thats probably mostly attributed to the gasser flywheel and really close pump timing. the 1.5 in theory is capable of turning more RPMs tho, because with a shorter stroke and longer rod, the piston speed is greatly reduced, allowing more revs to be pulled from the engine.

my $0.02

[MJF]

1,5 has same length rod as 1,6. Piston is taller.

[TurboJ]

You can make even the 1.9 IDI turn 7000 rpm if you know your pump building, but the difference between the 1.5, 1.6 and 1.9 will be in their rev-happiness, not the max rpm capability as such. A 1.5 should by nature rotate more happily as the moving masses are lighter. But you can modify the 1,9 too, for example a lighter flywheel alone should make a world of difference.

Just a thought: There are some gasser crankshafts that have the same stroke and journal diameter as some of the IDI engines... They are much lighter, and if I'm correct, they aren't any weaker by structure: the weight difference is down to the counter weights of the diesel crankshafts. Material thickness is the same apart from the counter weights.
I have been contemplating using a specific gasser crank on my next build. They are about a third lighter than the corresponding diesel cranks..... If one only knew fore sure they aren't any weaker!

[8v-of-fury]

I have been contemplating using a specific gasser crank on my next build. They are about a third lighter than the corresponding diesel cranks..... If one only knew fore sure they aren't any weaker!

I would think that because there is 1/3 less weight that it would be weaker.. unless the weight is saved by metals used. If the weight is saved because there is less material, of the same material.. then i would assume it will not like the diesel forces to much.

Beauty idea though

[theman53]

My gasser buddy Troy says that ALL vw 8v cranks were good forged stuff. He says a bunch of people want the 16v cranks, because they think they are the only forged cranks and therefore are better...But Troy says no. He has a 13.0-13.1 in the 1/4 mile 1.8 gasser and has NEVER had a crank failure. CVs, R&Ps, stripped 2nd gear teeth off, many clutch fails, but no crank issues yet 

[TurboJ]

Exactly, when you look at the gasser shaft next to a diesel shaft, the only difference that can be seen or measured, is the counter weights. Otherways they look and feel identical.
Besides, I have very rarely heard of a custom crankshaft on any high-power 8V or 16V 1.8 gasser VW. Even the ones with more than 500 hp seem to do with OE crankshafts, which may of course be lightened etc on some cases.

[Rabbit on Roids]

1,5 has same length rod as 1,6. Piston is taller.

check again dude. there different.

[NintendoKD]

so the verdict is that the rpm limit lies not with the internals but with the injection pump.  I will have to agree with rabbitonroids that the response of a stroked motor is different from a non-stroked one.  Can the compression losses be made up elsewhere?  I do not plan to build with the 1.5 bottom end, I already have a turbo 1.6 longblock.  It would be good to know if I can change something like shave the deck etc. to give a higher static comp. ratio to make cold starts easier.  The block is currently at the machinist.


thanks,

Kevin

[vanbcguy]

Not really any room to shave the deck since the pistons are already protruding...  Pretty much all the volume is in the prechamber.

[Rabbit on Roids]

so the verdict is that the rpm limit lies not with the internals but with the injection pump.  I will have to agree with rabbitonroids that the response of a stroked motor is different from a non-stroked one.  Can the compression losses be made up elsewhere?  I do not plan to build with the 1.5 bottom end, I already have a turbo 1.6 longblock.  It would be good to know if I can change something like shave the deck etc. to give a higher static comp. ratio to make cold starts easier.  The block is currently at the machinist.


thanks,

Kevin

you need smaller precups to add compression. the clearances between the head and everything else is already super tight.

[NintendoKD]

Ok, so the head should be here any day now can I use smaller precups in the aaz head?  I have read somewhere that this doesn't work?  adding some volume is part of the build so where can this get me 19/1 area would be about good I think just a couple more points but enough to keep the static low enough to allow for 30+psi boost.  Advice?

[Rabbit on Roids]

Ok, so the head should be here any day now can I use smaller precups in the aaz head?  I have read somewhere that this doesn't work?  adding some volume is part of the build so where can this get me 19/1 area would be about good I think just a couple more points but enough to keep the static low enough to allow for 30+psi boost.  Advice?

you can run 30+ in a stock 1.6 with a aaz head gasket and head studs.

[NintendoKD]

This I know, you, yourself were running that much at one time.  Two problems, I don't have a 1.6 head, and the other is "and more importantly" I don't want a 1.6 head  Oh, it's on baby YEAH!  how far can I push it? limits of not only rpms but boost as well?  will high egts ruin my fun and melt my head?  Keep in mind that I will have an extended oil reservoir due to the dry sump pan and the oil cooler.  I was thinking along the lines of 35 psi max at X? rpms  If I send my pump to the magician will he be able to do something about the limits of the pump?  I know I have lots of questions, but it is because I have no answers that I ask them so please bear with me.

Thanks,

Kevin

[8v-of-fury]

You have a 1.9 head?

All the better, lower Compression Ratio's are better for boosting. If a 1.6 can handle 30+ already having 23.5:1. The 1.9 combo will be 17.5:1 (??) and will be much happier with that much boost.

The magician as in Giles? He can do anything