I havent come across this topic before and its only for my personal information but main reason for people not running turbo's on an NA engine is the compression ratio (being much higher for an NA to a TT) isent it? Whats the process of lowering the compression? thicker head gaskets, different pistons? Cant think or dont know of anything else, like I said just for me (And anyone else wondering) out there. Ta.
for what purpose. a low comp NA will be a slug. unless your going 2 super or turbo charge it.. then you might aswell just use a TT block.. larger headgaskets will bring the compression down a Bit... not huge numbers .. my TT is a 3.2 bored out with metal headgaskets and still pulls between 145 and 150 compression.. a good TT would pull 160 stock
It's the NA pistons that give the VG30DE the higher compression ratio. You can run turbo's on a NA. I did a write of it in a thread somewhere from someone asking a similar question. Buggered if I can find it. But in a nutshell, 9psi on stock turbo's with good intercoolers and TT injectors is about as high as you'd want to go with 98 octane. Make good power though. To drop the compression into the 9's without changing the pistons, you'd thicken up the HG and run long duration and high lift cams.
Like Andy said with the cams. The cam overlap (if there is any) on the NA is different to the TT. Might be able to get away with TT Pistons, cams and copper gaskets (get thicker ones if you can), Re-honing and fitting new rings and bearings would be a good thing to do while it's apart, 100k kit too of course. Might as well make a fresh recon engine out of it. Also need to consider oil feed to the turbos and drilling into the sump and adding oil drains, or fetch a good TT sump as well as running water feed and return lines. Then you'll need a bigger radiator, TT manifolds, dump pipes and a TT ecu. There's probably more but I can't think of anything else right now. Maybe on other more basic engines, would this be process be ok but not on VG's. In the end you will have either a limited NA engine with turbos or a fully built turbo'd NA resulting the same specs as a TT (in regards to being built to handle boost without blowing). If doing this is more cost effective than just swapping the engine then go for it, otherwise do what everyone else does and just swap in a TT. Less work and less of a headache. Or buy a TT and rebuild that. Or you could Raise compression. Shave the heads, Stainless valves and heavy springs, cams, copper gaskets, bore the block, run stroker kit with rods and High comp pistons and port the crap out of everthing. UDP, lightweight flywheel (if manual). That should see some numbers.
so if you run bigger cams does that have the same effect as lowering your compression ? as in 8.5 comp with stock cams would be similar to 9 comp with big cams?
Yes an no with the rebuild, as soon as you change to TT pistons your back in the TT's compression ratio around 8:1. What he's asking is can you slot a pair of blowers onto an VG30DE motor without the ground up build, yes you can. It's not a simple bolt on affair. As Sticky mentioned you need to re-route oil feeds to the turbo's and drains to the sump. Can be done by adding a tree to the oil filter and running feed lines from there, and then drilling returns into the sump. Water can be routed from the heads. Then you need to fabricate intake piping and IC brackets. You can keep the NA radiator as the piping would be custom. You can keep the NA ecu, might want to retard the timing a little till you get it on a Dyno, but should be fine. Your extremely limited to power hunting with hi compression motors and available fuel (unless you run E85), There is a fair amount of custom work to be done, and is really in the realms of those looking for a challenge and who would do all the work themselves.
Other way round, larger cam lower comp. It's the difference between static compression ratio and dynamic compression ratio. Manufacturer Compression ratio's where it be written on pistons or on engines, are based on a basic formula using bore, stroke and chamber volume and assumes the cylinder is sealed from the bottom of the compression stroke to the top. This is static compression ratio. That's where cams come in with over lap and valve timing, etc, etc and you end up with a chamber that is no longer sealed and this is your dynamic compression ratio. When you increase your overlap with valve timing, or larger intake cams, etc then your decreasing your dynamic compression ratio. I can go on, but it's easier to understand with specific examples, and I don't want to be writing all day, so go google
think you miss understood what I meant 9 to 1 comp engine with big cams would be similar to 8.5 to 1 comp engine with stock cams ....as big cams would lower the comp is what I was asking
Overlap is the same as the cams are the same I'd like to try turboing a NA VG oneday, be interested to see how good it would turn out...
Static compression no, as it's a formula based on bore, stroke and volume. Dynamic compression, cams have everything to do with it, so does boost pressure.
Maybe I missed it somewhere in this thread but I didn't see anyone mention the oil squirters that pump oil up under the TT pistons so they dont melt, and the wrist pins (I think thats what they are called) are much larger on TT pistons, I cant remember who the member was over on twinturbo.net that raced an NA with turbos, did ok for a while then he turned the boost up a bit (nothing outrageous) and the engine went bang... I really think it is pointless putting turbos on an NA engine, it wont last as long and you end up spending probably the same money getting all the parts you need... buy a TT or convert to a TT proper... I just wish I had bought a TT instead of my NA all those years ago lol
i used to see people all the time stick a huge cam on a stock compression motor and wonder why the gains were minimum
i should add, big cams as in long duration, not lift. thats why alot of the V8 cam manufacturers were offering massive lifts with short duration, they were able to do this once they went to roller followers. short duration meant no loss of idle qulaity or drastic compression change
The NA's have squirters as well... I thought that the TT and NA con rods where the same (hence the wrist pins).
