Try and get a few of them in here...
The double spring injectors are all about reducing noise and improving the burn (less smoke), but not really in a performance way. They do a pre-injection before the main injection to get the fire started so to speak - this reduces the knock when the main injection happens since it's not such a shock. Good for emissions, good for reducing noise, but extremely difficult to calibrate without pro level tools and difficult to find nozzles for. So yes, the Germans had some good reasons to go that way, but nothing that's really relevant to what you want to do.
How the larger prechamber volume will react and how to best make use of it is anyone's guess. At the very least I'd say it gives you an opportunity for more fuel since there's more room for air in there, but without getting the engine running it's hard to know. You might find the AAZ injectors are better matched to the AAZ prechambers, or you might find it makes no difference - it's honestly fairly uncharted territory. From what I've read on here the 1.6 nozzles are capable of flowing as much fuel is you could possibly use without issue so there's not really a lot of gains to be had there. Now, where the 1.9 injectors MIGHT be relevant to you is actually their starting abilities - the preinjection MIGHT help start with your low compression, but until you have the motor together and actually see what happens, well... who knows?
The VE pump definitely has its limits - Giles can make pumps that are happy to above 6K RPM but what he does is top secret. He's got access to the complete world of Bosch parts from just about any engine you can imagine, plus a test bench and a ton of training, so he can mix and match pump parts to get what he wants. We all don't even know enough about what we want given the massive number of variables (cam plate shape, cam plate lift, plunger size, etc etc)... Giles does machining to the pump body to allow it to have more dynamic advance, he tunes the actual dynamic advance curve, he creates a governor that doesn't limit fuel, I'm fairly certain he's changing the camplate (who knows what to though) and any number of other things. When you actually look at what all he's doing his price is extremely fair - even if we knew exactly what parts he was putting in doing all the machine work and tuning is worth it big time. If there's any single thing you spend money on with your build it should be the pump. And yes, Giles can pretty much do up the dynamic timing however you want, including having retarded idle timing and crazy advanced higher RPM timing. There's basically no way to do this on your own - you really need a full test bench. And understand that when you order a superpump from Giles you're also buying a consultation with him and his advice tuning your engine after you've bought the pump, not just some replacement part made for an anonymous customer by an anonymous factory worker somewhere.
I think the 5K limit for the VE pump really comes from the versions for engines with 6 or more cylinders, with 4 bangers we can get a bit more RPM out of them before they start to float. Seems quite a few people have done nothing but the governor mod and gotten 5500 RPM without too much trouble. At that point though I think you're out of dynamic advance on the pumps the way they come - back to needing Giles again.
So yeah, lots of words but what it comes down to is:
- Bite the bullet and get Giles to do your pump. The $$ per HP gain is probably better with him than anything else you can do
- Get the coldest air you can in to your engine
- pull cold air in to your turbo,
- find the best intercooler you can
- Get as much air as possible in
- Make sure your intake is unrestricted
- Port your head, even just gasket matching will help
- Stock intake is crap, there's nothing aftermarket available, this is a good place to spend some efforts making something yourself
- Get the exhaust out
- Don't run your boost TOO high or you're just putting too much restriction on your exhaust and pumping in air that is too hot
- Get the best downpipe and exhaust you can afford
After all that you're in the upper ranges of what you'll ever get out of these engines before you blow the head off the top.
