Solving Boost Spiking On The Gt3540

[DennisRB30]

Does anyone know what size they port the wastegate out to?

And does fitting an actuator with more throw help reduce boost spiking?

[Ralph Wiggum]

I got my waste gate ported apporx 6mm larger than the standard circumference and fitted an 11.5psi actuator. The difference it made is fantastic. Obviously the lowest boost i can run now is 1.5 psi but i can actually use my eboost to create a boost profile now. Before in high gears and high rpm the boost was impossible to control properly. It cost me $50 for the machine work and $117 for the actuator. Some other members also had there flapper valve change and had similar success with that and porting the waste gate as well.

[DennisRB30]

I got my waste gate ported apporx 6mm larger than the standard circumference and fitted an 11.5psi actuator. The difference it made is fantastic. Obviously the lowest boost I can run now is 1.5 psi but I can actually use my eboost to create a boost profile now. Before in high gears and high rpm the boost was impossible to control properly. It cost me $50 for the machine work and $117 for the actuator. Some other members also had there flapper valve change and had similar success with that and porting the waste gate as well.

←

Thanks mate! Please tell me as much info as you can guys.

My boost control is shocking ATM and I get creep up past 1 bar in the top end, and I haven't even fixed my 3" exhaust which has been damaged and is probably restricted to 2.5 inches. How big is your exhaust? Its very difficult to set a flat boost curve how it is.

I can't see how you got it ported out 6mm without a new flap valve though. It appears as though there is only about 2 or 3mm overlap with the stock flap.

[Ralph Wiggum]

There was approx 4mm of over lap on the standard valve so the guy that did the machine work ported the waste gate radius 3mm larger (6mm total on the circumference of the port) My exhaust is a 3.5"dump a 4"cat and 3.5"intermediate pipe, a 3.5" inlet muffler that splits too twin 2.5" and runs to another twin 2.5" inlet/oulet rear muffler. Before i got the waste gate machined and changed the actuator i couldn't get the boost lower than 20-22psi in 3rd and 4th gear. If you want to keep you boost below 14psi you should consider an 8 or 10psi actuator and getting the housing ported.

Sounds like you must have a pretty sweet high flowing intake setup if you got a squashed 3" exhaust and you still cant keep the boost down... got any pictures of your setup?

heres a couple of picture of the Nizpo setup on my car...

Edited 23/01/07 09:36 PM by hiddeous

[DennisRB30]

Looks sweet. My car isn't an XR6 (its an R31 skyline with a 3 litre 2JZ supra engine).

Here are some pics of the exhaust I made. The first pics are the of the original exhaust which joined to the stock 2JZ turbos. The second pic is the new 3.5" dump pipe which I joined to the original system. The 3" part is actually 80mm truck exhaust, so its slightly larger than 3".

I also have a 600 x 300 x 100 intercooler which may be helping it overboost. The restrictive XR6 cooler probably limits boost a bit (if its still fitted that is). Do you have a better cooler?

I made my stock actuator into a 10 psi actuator by joining an external spring to the actuator bracket and a rod I welded to the actuator arm. Something I noticed with the stock actuator is that it does not have enough throw to open the flap all the way. This may be causing some probs too.

Edited 24/01/07 01:22 PM by DennisRB30

[DennisRB30]

Oh and the intake setup.

[BFHOON]

looks like it was ment to be in there dennis ...

with a little bit of polish work it will look awsome

looks neater with the single rather than the factory twins.

Edited 24/01/07 08:50 PM by hooverman

[Ralph Wiggum]

I have a Nizpro cooler and intake setup and with the APS exhaust on my ute the boost was near on uncontrollable up high. As i have said get a decent actuator and get the wastegate ported and you wont look back.....

[RAP1D]

Nice project there mate, but if I were you I'd weld the internal gate shut and use a decent external w'gate... HEAPS better control than these pisspoor internal gates

[DennisRB30]

I have a Nizpro cooler and intake setup and with the APS exhaust on my ute the boost was near on uncontrollable up high. As I have said get a decent actuator and get the wastegate ported and you wont look back.....

←

Cheers mate. Will do.

Most people recommend boring the hole out to larger than what can be achieved with the stock flap, which on inspection of my turbo looks like only a small amount. So considering I am having issues with creep with a kinked 3" exhaust in 35 degree weather I think I will go the whole hog. My brother is ready to do the machining.

Will it matter if I make the new swing valve arm and valve out if tool steel instead of stainless?

It looks like I can go HEAPS bigger. But the larger I go the more probs I will have due to having to bore the new hole at an offset to the old one, which will also require a new swingarm assembly to cater for the offset. So more info on the size required would be a massive help.