MattSR

"The mathmatical guide that Garrett gives is enlightening" Could you give us a link to this guide? Im interested in what they have to say.

Gday peter - spring binding doesnt depend on RPM - if springs dont biond when you spin then engine over by hand, it wont bing at 9k rpm cheers, Matt

"Hi Roy, for controlling boost the valve is actually a phneumatically actuated - electrically controlled rotating spoon valve 3" in diameter. Was primarily used as a shutoff valve on the Hornet for engine bleed air. It has provision for position sensing and can be locked into any open position electrically. It has a light spring load bias in the closed position and uses differential air pressure on both sides of a diaphram to control the movement of the valve. It's very sensitive to pressure changes. I've got pictures of it, just got to find a spare moment to post them up in my gallery." Sounds like the worlds most sexual wastegate to me

Turbine - It could be useful to measure your backpressure vs boost - this will tell you how well your turbo is matched to the engine

"I know about Mach numbers, flow etc But i thought you would want flow thru the turbine first and foremost not the wastegate." Cant disagree with that one "If there was not pressure in the exhaust manifold then there wouldnt be a pressure differential for the air to bleed off and control the turbine speed." I should clarify this - theres definitely pressure in the exhaust manifold, I just wanted to say that wastegates regulate intake manifold pressure, not exhaust manifold pressure.. Anyways, i think ive said enough Cheers, Matt PS- nice to know people can still discuss things without resorting to a pissing contest

I guess we can respectfully disagree. In a properly matached manifold, the gasses are traveling at at local speed of sound. They really dont want to change direction. Pressure may not be directional, but flow certainly is, and thats what we're trying to achieve. Flow.. Its a nice job thats for sure... One thing - Wastegates work to regulate turbine speed, and boost pressure - not exhaust manifold pressure. The wastegate doesnt care what pressure is in the exhuast manifold - it only knows that it has to bleed off exhaust gasses when a certain amount of boost is present. PS - I Love your Skyline

"Thats the problem. You dont want the air goign straight out the turbine housing." Well, you actually want part going through the housing and a small part going out the wastegate "You want the air to go thru the scroll of the houisng, spin the turbine then out the exhaust. When there is a a certain amount of pressure in the housing you want the wastegate to open and bleed of airflow so that the turbine does not continue to accelerate." Thats right - and to get any semblance of decent boost control, the gasses going through the wastegate need to do it easily. If the wastegate gasses have to turn 90 or 180 degrees to go through the wastegate, then they're going to take the easier path and go through the exhaust housing instead, which will cause overboost. My above post explains why its been done this way. Im sure when Turbine replies he will back me up.

Strange, but extremely well thought out.. The collector is the most important part of a turbo manifold, and positioning the wastegate like this enables a pefectly smooth collector design (ie no funny holes at strange angles that interfere with the gas flow path even when the wastegate is closed) Ive seen several big HP drag cars with this mod - it works well.

Col, would you be able to post up some more info and or pics please? im sure everyone here would love to find out more info

Its perfect - The gasses going out the wastegate have a clear, unimpeded shot stright through the turbine housing. This pic shows it better:- http://www.skylinesaustralia.com/photopost...&cat=500&page=1

How well would a GT30 be suited to an RB20 with cams? I reckon it'd be a good match if the RB20 could handle ~8500-9000 rpm or so Cheers, Matt

The most ive heard of anyone getting out of a GT3540 (on a properly calibrated DD) is 540rwhp.. By the sounds of it, your setup (with some nice 272 cams) should max out the airflow on that turbo no problems.. Cheers, Matt

Amen!

If they're good enough for the second fastest GT-R in Australia, then im sure they'll be just fine for you

" imagin a 6speed trust box.. way over 600kw's" Yeah for about a 1/2 a second before it srays its innards all over the ground

I love open deck engines....

Sodium filled valves are shit compared to one piece stainless Inconel or titanium valves..

Also limits the size of the cams your motor will tolerate.... I agree totally - backpressure is GAY.... I have seen a stock S2000 motor run 6psi boost through a HKS GT3040 - made 240rwkw and run heaps of timing all on 11:1 compression.. The reason why was because of the low backpressure and big overlap of the VTEC high cam... Cheers, Matt

Robocop - I'd love a copy - PM me with an offer

Hughey's book is better than that corksters... especially the bits on manifold design and matching

Ahh I thought you were referring to the RB25 - not 26 for a 26 I reckon the 1.06 would be the go

Its less than that - closr to 80hp. From what sydneykey has told me, you should go for the 0.82. Unless of course you have a built motor that can rev harder (say 8500) and make use of the bigger compressor

Sounds shit with stick cams, with a decent set of largish cams its sounds like a banshee...

Has it got a stock turbo or a "highflow" turbo

Is the car shaking voilently when this happens? is there is lot of whistling and popping coming from the turbo? Sounds like it could be comp surge, but without more info on your turbo i have no idea