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Not Happy With My Rb25 Builds Figures

chrislesnar

By chrislesnar,
in Engines & Forced Induction

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l0WRB Mentor

l0WRB

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larger actuator will only allow you to run higher boost, perhaps it might help you hold 16psi thru to redline as for now it seems 2 be dropping down as u go thru the rev's

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KiwiRS4T Grand Master

KiwiRS4T

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Yes, we had a chat today. I did advise before hand that i only wanted 16psi but i thought it would have pulled a bigger figure on that. I mentioned adding a high pressure actuator but he said that the 18psi actuator on it initially was to large and a 12-14psi actuator would be better suited for my build. Atm i happy with how the car is running but just think it could have pulled a larger figure. Will this high pressure actuator increase the hp by that much?
Well you've just answered the question why did they pull out the 18psi actuator - because you said you only wanted 16psi!!!!! Tell them to put the actuator back you will be happy to run 18psi and make some more power!
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GTScotT Grand Master

GTScotT

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Truth is 18psi is a rough limit of the stock valve springs, so he may actually be avoiding causing you valve float.

Hypergear (Stao) himself found this issue, I have also seen it across many over results.

You may want to swap out your valve springs and retune.

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hypergear Grand Master

hypergear

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the Arias 20thou over sized pistons would be 8.6:1 using stock head gasket. With cosmetic gasket depending on what it is, would set your engine below factory compression ratio.

Which means more boost is required to produce the same amount of power with laggier response as the whole power band shifts towards the right. How ever this setup is ideal for larger turbos with plenty of boost. So this baby high flow might not be the exact turbo for your application.

With the stock valves and valve springs, I'm unsure at what psi they floats, conditions of it varies. Unsealed valves acts like vacuum leaks (with fuel)affecting response, power, and make the car feels hopeless pre-boost. I would definitely recommending stronger valve springs for high powered applications.

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Harey Veteran

Harey

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Truth is 18psi is a rough limit of the stock valve springs, so he may actually be avoiding causing you valve float.

Hypergear (Stao) himself found this issue, I have also seen it across many over results.

You may want to swap out your valve springs and retune.

You think its a boost pressure limit and not a power limit? Its probably a combination but I dont think you would get valve float at such low power.

Tao's car cops constant abuse at mostly over 300rwkw, surely the high power has a major factor as well.

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zebra Grand Master

zebra

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The valves have to close against the pressure in the intake ports, the more pressure in them the harder it is for the valves to close, hence valve float, also depends on how hard he is revving it.

Power has very little to do with valve float.

But the dyno chart has no big dip in the power to suggest valve float, but boost does bleed off to 13-14psi like 99% of Hypergear turbos.

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hypergear Grand Master

hypergear

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I wouldn't care if its just valve floating. Its the damage it does. 24 leaking valves will affect lots of thing.

But the dyno chart has no big dip in the power to suggest valve float, but boost does bleed off to 13-14psi like 99% of Hypergear turbos.

Not 99%. 100% high flows without high pressure actuator will result in boost drop. This also apply to inlet and exhaust restrictions.

Read the thread, High pressure actautor I supplied was removed by user.

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zebra Grand Master

zebra

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I wouldn't care if its just valve floating. Its the damage it does. 24 leaking valves will affect lots of thing.

Not 99%. 100% high flows without high pressure actuator will result in boost drop. This also apply to inlet and exhaust restrictions.

Read the thread, High pressure actautor I supplied was removed by user.

I read the thread, OP says its running 16psi, It isnt.

You wouldnt care if its valve floating?!?!?! I would certainly care if a valve seat cracked and fell out, or a head broke off the valve stem.

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Harey Veteran

Harey

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Funny how you guys look for any chance to get at Tao even if it doesnt make any sense (above) but dont comment on him possibly solving the issue the OP is having, low compression and incorrect turbo selection.

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zebra Grand Master

zebra

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Funny how you guys look for any chance to get at Tao even if it doesnt make any sense (above) but dont comment on him possibly solving the issue the OP is having, low compression and incorrect turbo selection.

Might be because he is so quick to blame everything but the products he supplies, im sorry but 0.4:1 comp wont make 20-30rwkws difference, the engine would need maybe 2 degrees more timing to make up the difference, if he was running 7:1 comp than yeah sure it would make a big difference.

For all we know the tuner has a low reading dyno or it was a hot day or the cam timing is out, or there is a leak somewhere.

There are a million things it could be, but saying that having lower compression will mean that the dyno curve moves to the right is just a bit silly, especially with standard cams, sure off boost it might be a little bit softer, but with a good tuner the difference should be able to be made up with fuel and timing changes.

Of course Tao isnt going to say his turbo is at fault, because he builds/sells them.

*waits for all the fan boys*

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GeorgesR34 Collaborator

GeorgesR34

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Might be because he is so quick to blame everything but the products he supplies, im sorry but 0.4:1 comp wont make 20-30rwkws difference, the engine would need maybe 2 degrees more timing to make up the difference, if he was running 7:1 comp than yeah sure it would make a big difference.

For all we know the tuner has a low reading dyno or it was a hot day or the cam timing is out, or there is a leak somewhere.

There are a million things it could be, but saying that having lower compression will mean that the dyno curve moves to the right is just a bit silly, especially with standard cams, sure off boost it might be a little bit softer, but with a good tuner the difference should be able to be made up with fuel and timing changes.

Of course Tao isnt going to say his turbo is at fault, because he builds/sells them.

*waits for all the fan boys*

You just said valve float does not affect performance and minut later you giving all the affects of valve float. answering your own query.

There are a million things it could be said your self.

Read ths OP's post. He's got low compression pistons with "cosmatic head gasket". Could be in 1.5 or 2 mm in thickness. who knows. might be below 8:1.

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GeorgesR34 Collaborator

GeorgesR34

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The valves have to close against the pressure in the intake ports, the more pressure in them the harder it is for the valves to close, hence valve float, also depends on how hard he is revving it.

Power has very little to do with valve float.

But the dyno chart has no big dip in the power to suggest valve float, but boost does bleed off to 13-14psi like 99% of Hypergear turbos.

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