Harey

In my scenario, adding a boost controller only increases boost between 4,000-5,000rpm after that it drops to the same level. This means that even with the actuator receiving almost no boost signal (boost controller) the wastegate flow is still pushing the wastegate flapper open and overpowering the actuator spring.

These are the ones you want: http://www.kudosmotorsports.com/catalog/nismo-fuel-injector-nismo-740cc-nissan-rb25-vg30-0993-p-887.html

The fact that the boost level is dropping as the rpm increase means that the wastegate flow is overcoming the actuator spring and pushing the wastegate flap open. Is this what you mean by wastegate choking? It will only cause a boost increase if the actuator cant control the boost.

Not sure if "dull" is the correct word to use. The 1.06 housing will have some lag and then hit harder. I would personally choose a GT35 0.82 for an RB25/30 if I ever do one.

If less timing means more energy out the exhaust, the extra exhaust flow would push the wastegate open (lowering boost) as the spring is already beyond its limit. If less timing means there is less pressure spinning the turbo then it all makes sense as we said.

I suppose it was just the way I read the opening post too. The emphasis sounded like it was on response. The major thing that affects the response is the turbos so its just the logical answer. For that amount of power (330rwkw) you can use a smaller turbo and stil achieve that power. Changing turbos is expensive but if you go spending 1000's on other ways to improve response you are really doing things backwards. As other people have said, get some injectors, a 3.5 or 4" metal cat and retune.

I made up a cheap one with some pvc pipe caps and a $20 hand pump. See below photos. I blocked off the pipe going into the throttle body, hooked up the pump to where the pod filter was and pumped away. The advantage of the hand pump over an air compressor is that because it is quiet it is very easy to hear even the smallest leak. Do you mean the intake manifold or intake piping? Mine was for the intake piping.

Congrats HEKTIK!! Great result, such good response and still 280rwkw! Post up the dyno in the dyno results thread, its just teasing without seeing it.

If you decided not to go any further it would be a poor package imo. You bolt on large turbos -5 turbos and then limit them to 280rwkw, so you get more lag and the same top end so no advantage. I would only get the -5s if you plan to change the AFM and injectors one day. Until then it will be far less than perfect. -9s are what your after, they would be good with the stock AFM and injectors but will also reap big rewards if you do change them. If you dont have plans to change the AFM and injectors, and dont care about the reliability of ceramic wheels (from the fact you want to buy R34 BB turbos) then just get some cam gears, catback exhaust and a tune. You should get ~250rwkw out of that and leave it.

The helper spring also makes a lot of sense because it is not affected by the pressure received at the actuator.

In my current situation with only the actuator (no boost controller) it makes 17.5psi and then drops to 15.5psi. When I hook up a boost controller it will make say 20psi and then drop to the same 15.5psi. I believe that in my situation it does not matter what pressure the actuator is getting it would still only make 15.5psi up top. To test this I could take the hose off the actuator so it never sees pressure but it would prob make 25-30psi for a quick moment and then drop to 15.5psi. In my case the wastegate flow is completely overcoming the actuator spring. What we need is a super stiff spring that still moves at the same rate with the same pressure. This is what I am hoping the holset actuator will provide as they frequently run 20-30psi with internal wastegates. If you read that EVO link a lot of people were having the same problem as us and solved it with the holset actuator up to about 23psi, above that they were still getting some boost drop off.

Hmmm so the extra timing up top was causing more wastegate flow causing the wastegate flap to hold open more?? When timing is dropped so is the wastegate flow and the spring can once again pull the wastegate closed a bit to increase boost. Its annoying cause an 18psi actuator is supposed to make a flat 18psi and then a boost controller make a flatish 6-10psi above that.

Yeah it seems to be major issue. I have been reading up about it a lot recently. (If you already know this just ignore it) My understanding is the wastegate flow is overcoming the tension of the wastegate actuator spring. The actuator spring should compress completely at the rated pressure. Although in our cases I believe the wastegate flow is pushing the wastegate open further causing the boost to drop, then the drop in boost means the spring tries to extend back in order to close the wastegate a bit, however the wastegate flow is too strong and holds the wastegate at this point, causing the boost to drop 2 or psi until redline. I first read this thread about 'helper springs': http://forums.nasioc.com/forums/showthread.php?t=589293 Yes they are quite ghetto and probably not what I would recommend but there is some good info here and if nothing else it at least proves what the problem is. Problems are the springs dont last too long so you need to replace them plus each spring is slightly different and can change boost differently, meaning you prob should check it on a dyno etc. Then I found this, EVO guys using holset actuators: http://www.dsmtuners.com/forums/turbo-system-tech/356977-holset-actuator-20g.html Some more good info here. I have actually ordered a holset actuator from a HX35 from the US. They are supposed to have very stiff springs as they are designed to run high boost on diesel trucks etc. EVO guys have had good success. It will almost certainly require some modification to the rod though. The goal is an actuator with max stiffness to the spring but will still open with 18-20psi of boost. Was cheap so worth a try!

Ok thanks for the info. My standard hypergear actuator wont hold more than 15.5psi at redline even with a boost controller, so I have purchased an upgraded actuator, just waiting on delivery. So the 18lb spring from Pat is only making 15.9psi high in the rpm? Or do you have updated dyno figures?

Yeah keen to hear the result as well!

The fact that you are asking a car forum whether you should modify you car means you want to do it and are looking for reinforcement I think you should save your pennies, get a nice share portfolio, put a deposit on a house... PYSCH! ONLY JOKING! MOD IT! MOD IT! MOD IT! I love my R34 with 280rwkw!

Yeah but its the number of bends and welds that is labour intensive. The price of a 4" 45 degree bend is what $25? Hourly labour rate would be $50-80?

I disagree with the factory airbox, you will loose a signifant amount of power. Its criminal on a 3076 imo. If you are certain on keeping the factory airbox then at least upgrade the intake piping to 3" metal. Someone on here had one made up and it was quite expensive as it must join the airbox at exactly the right location. You will gain power with a 3" metal intake and pod (preferably shielded) when above 250rwkw. See the quoted post above regarding those small injectors. It is criminal using such small injectors on a 3076 turbo, it will limit you. Otherwise, get a smaller turbo. No point having a large turbo running low boost and relatively low power. Sell your current injectors and upgrade to larger ones, shouldnt be more than a few hundred changeover and then you will never have to worry about it again. You can then allow your turbo to do its thing, even run E85, or up the boost if you do an engine build one day etc etc. Not to mention it is safer to run injectors less than 80% duty cycle. Sell you fuel pressure regulator and put it towards the injector upgrade instead.

But obviously a single turbo 4" external wastegate dump is a lot less complicated and intricate then 2 smaller internal wastegate dump pipes. Still good just saying its not really comparable. But I suppose it does at least give you some idea of costs.

5L/100km is what a diesel hatch would use haha. I was saying that I had lost around 5L/100km, so I was using around 15L/100km then it dropped to 20L/100km while I used the 5% ethanol shell fuel (without a tune for the fuel).

I tried it in my previous turbo car and noticed consistenly worse fuel consumption. This was without getting a custom tune with the fuel of course. About 5L/100km worse. Noone seems to mention there fuel economy on it but you guys prob dont care haha

reply to whoops lol

Yup cool, I suppose its easy with the brand names as you can see what the goal is. Then you have the choice to get a local fabricator to do a similar design or pay for the brand.

A fuel pump flows more fuel at a lower fuel pressure. Increasing the fuel pressure above standard will only make the fuel pump run out of flow quicker.

Yup sorry, I agree with what your saying just didnt want people to expect different boost levels in different gears with a well setup actuator/boost control system. You are 100% correct its easier to build boost with more load.