update i have been discussing quite a few issues with graham tektrader and have been trying to determine any issues that my car may be having so far we have come up with a.boost leaks and b. possible wastegate creep from old turbo actuators as it seems that my car cannot make anymore power beyond 6000rpm.
THere are people on tt.net claiming to make > 450rwhp ~330rwkw with stock engines with both GT28R and GT28RS. I believe that the GT28 was the RR on UAS's engine, it's dual ball bearing or something, but that's the only difference. I thought the 28R was now dual ball bearing as well but I am not sure.
yeah i have seen the dyno's tylers tuned by ashspec made 481rwhp with similar mods but i am also not about to go comparing US dynos with our dynos as they are different. I havent given up hope and believe the issue to be more boost related than turbo but i am yet to see a high power figure with straight of the garret dealer shelf gt28r turbos. (high being 280rwkw+) i have seen 256kw, 248kw, 225kw(auto) so far, would love to see a high dyno figure (local) it will restore all faith hehe.
I am skeptical about the claims of the GT28RS. There are a lot of people running them, yet only a few making big power on LOW boost, I don't know if I trust half of the dyno readings out there but I guess strip times prove the power, although I think a 400+rwkw gutted out Z with slicks should still run a quicker time than a high 10. I have sgp ported race heads, JUN 9.5mm lift cams, crower rods, acl pistons, will be buying MS manis once more people use and test them, bigger intake piping, GT28RS turbos, a free flowing exhaust, i'll match port the plenum/lower plenum etc the list goes on. Most likely get the autronic SM4 and a few other things. I know a place with a very conservative dyno (the shop has built many many sub 10s cars) and I will take it there and do a dyno run once the engine is finished. I guess there isn't much more I can do without going stupid on the engine (which I wouldn't do because it is still only a VG30DETT). If a figure no where near 400rwkw shows up, then I don't know what I am missing - as opposed to those making that sort of power. This is why I will be happy with ~350rwkw at a low boost setting.
Power With these turbo's assuming same or very similar we made just over 400rwkw with very mild cams and with stock cams should make 350rwkw easy. When you fitted turbo's to motor did workshop check and calibrate the turbo's as in pressure equalised on both to crack open at same time. Also need to check what boost level the actuators will handle by testing with say 18psi for example PRIOR to putting turbo's and motor in car as if you have not done this then you may in advertantly now have sequential turbo's. As in cracking or opening at different pressures. You will then also probably not enough pressure if upgraded turbo?s as stock actuators won't cope with the higher flowing turbo's, and probably different levels of boost pressure they will hold. If fitted by a workshop they should have known and done this?? As a general rule you will be able to adjust with boost controller around 10psi more than what actuators are set to open at. Sometimes this will hold more or less boost than this in reality.
Its actually more to do with exhaust gas scavenging. Increasing the overlap allows the spent exhaust a bit longer to exit the combustion chamber by using the incoming charge to help push the spent gases out the exhaust. Increasing the overlap to let the exhaust valve stay open longer while the inlet valve is open enables this to happen. Isnt a good idea if you want to meet pollution specs. In a heavily overlapped setup. Some percentage of raw inlet gasses make it out the exhaust. Thats why it isnt like this from factory. Increasing the charge density by not allowing it to be diluted with a percentage of spent exhaust gas is where the extra power and torque comes from.
lol i deleted this post because i had enough of this debate, my post was wrong anyway, advancing the inlet and retarding the exhaust is increasing the valve overlap but not the same as on a N/A motor. exhaust gas scavenging doesnt exist on a turbo motor in the traditional sense, because of the backpressure in the exhaust tract. so a little help from the inlet charge doesnt do any harm
Great thread, thanks muchly! Particularly Tektrader for his detailed and well researched comments I do get easily pissed off with the crap some people talk on tech matters but stuff like this makes up for it :thumbup:
You guys are always going to struggle with smaller twin turbos to make the pretty line go higher, I cant even imagine how hot those little suckers get down there at 30lbs+. 300rwkw is only 402rwhp, it seems way too difficult/costly to crack that with the DETT from what I'm reading here. LOL I just realized this thread is 2 years old! haha nice!
Lol at my argument with Tekkie. I still stand by what i say that a cam upgrade is not essential for 300rwkw. ive done 250 rwkw with stock turbo's and auto cams!!! In terms of improving headflow i think that removing the huge step from inlet valve short radius is a much better bet.
Agreed, especially considering 300rwkw/402rwhp is possible on the SOHC VG with stock guts. The DOHC should do it with ease. TT's aint great for dyno queens as that's not their purpose. Two smaller turbos are for response, nothing more. Their intention isnt really to build insane amounts of power because they dont cut it, not for the money it'll cost you anyway unless you can fit twin GT42Rs in there! lol
Rubbish 300rwkw is only 402rwhp, it seems way too difficult/costly to crack that with the DETT from what I'm reading here.
Go look at Mr. ICERs mod list, that shit is mammoth and the cash spent would be extreme and he hasnt pipped 300rwkw yet and I didn't see too many other people putting their hand up here either who have gone that far. (none?) But you're right I'm totally wrong, must be piss easy eh?
hit the enter button but yes, its rubbish, the people who have that figure+ just dont talk about it, and there's a few off em here!
I bet they have all spent a truck load of money though to get there, shit just the new GT28rs alone are what? A grand a piece? That's not even the start of it either obviously. They're expensive to make fast, I dont care what you say. Just the nature of it being a twin turbo/dohc alone doubles yours costs straight up. You cant deny that. The price of those two turbos ALONE is what I spent on my entire fuel system AND single turbo good for 350rwkw.
