how to lower boost

[tassiehunter]

G'day all wise ones,
I have just turbo'd my 2.8 hilux, I made my own kit up using a surf manifold with a new IHI RHF5 watercooled turbo from a mazda bravo, all set up and running now but I have too much boost. The boost pressure shows the wastegate opening at right on 10lb then it drops just under that, the turbo has full boost by 1700rpm, if I keep the foot into it to the goveners the boost pressure will rise to close to 12lb. The egt's get to 520 on a long hard pull, I would like to drop the boost pressure back to around 8lb, any thought on the best way to do this? I was thinking of an external adjustable wastegate running a lighter spring? and just leave the internal wastegate where it is, but I don't know what would happen if it was under water and opened? is there a possibility it could suck in water? would the external wastegate drop the boost like I want? or have I just got the wrong turbo to get it set up like the motor needs? (oh, yea, it flys at the moment too)

[crunk81us]

install an intercooler? would lower ur egt's, and leave boost where it is?

[hulsty]

why do you want to lower the boost?

[tassiehunter]

why do you want to lower the boost?

I think 12lb is a bit much for the higher compression of the non turbo 2.8? The motor has been fully rebuilt and has 35000kms on it, and I didn't think that much boost would give me the reliability? I will be looking at running a water/air intercooler down the track .

[crunk81us]

can you adjust the wastegate on those?
my turbo had a threaded rod to the wastegate which adjusts the opening pressure.

[matts_gemmy]

make sure theres no washers behind the wastegate to space it out so it boost more bit off a tight ass way of doing it but i've seen it done. or probly cheaper and easier than making up a new manifold with external is makin up a bracket to push the external gate closer the the exhaust or jsut bend the bracket closer so that it shortens the shafts movement let me no how u ge ton if this doesnt work

cheers matt

[tassiehunter]

ok, come up with a half assed idea that seems to be working, the actuator for the wastegate pushs the lever connected to the wastegate towards the dump pipe, so I put an anchor point on the dumpipe in line with the actualor rod, (exhaust clamp) and then fitted a tension spring to the wastegate arm connected back to the exhaust clamp, I then tested, moved the clamp to put more or less tension onto the spring/wastegate lever until I had it boosting to a 8lb max, apart from things like the spring coming off or loosing tension over time ect I can't see what other problems it can cause, seems to be working as needed.

[howesy]

G'day all wise ones,
I have just turbo'd my 2.8 hilux, I made my own kit up using a surf manifold with a new IHI RHF5 watercooled turbo from a mazda bravo, all set up and running now but I have too much boost. The boost pressure shows the wastegate opening at right on 10lb then it drops just under that, the turbo has full boost by 1700rpm, if I keep the foot into it to the goveners the boost pressure will rise to close to 12lb. The egt's get to 520 on a long hard pull, I would like to drop the boost pressure back to around 8lb, any thought on the best way to do this? I was thinking of an external adjustable wastegate running a lighter spring? and just leave the internal wastegate where it is, but I don't know what would happen if it was under water and opened? is there a possibility it could suck in water? would the external wastegate drop the boost like I want? or have I just got the wrong turbo to get it set up like the motor needs? (oh, yea, it flys at the moment too)

Turn the fuel back ever so slightly and your EGT's will go lower and it will find it harder to get to that 10lb. I had my lux spiking at 9- 10 lb and dropping back to 7 - 8 lb max spooled up ok with low egt's good economy. Crude but sort of effective

[drr]

You may be able to pull the wastegate actuator apart and replace the spring with a softer one. Then you can just use a simple boost controller to bring the boost back up to where you want it.

That level of boost shouldn't be an issue anyway, just ease off with the right foot slightly if your worried about EGT's until you get your cooler fitted.