intake problems

[c-west norway]

Hi,

I have just finished my s13 rb26dett conversion and are having promlems around the intake/turbo.

The engine has two new garret gt28r turbos,z32mafs and apexi pfc.

The intake pipes are 60mm ss directly to the turbos.

The problem I am having is that it sounds (and feels) like the intake pipes are blowing air out again in a pulse: front ,1sec, rear,1 sec, front,1sec.... and so it goes on.

Does anyone know why this happens?

Should there be a balance pipe between the intake pipes?

(I dont have the original ones to check)

the engine is running very ritch because the registrered air comes out again.

Here in norway there is not more than around 10 gtr,s so nobody has knowledge on tuned rb26 engines.

Any tip/help will be apprechiated alot!!

[StockyMcStock]

does it do this when it's just idling or what? sounds like reversion (large volume of compressed air being pushed back past the compressor wheel upon gear change) but that shouldn't make the car run rich, maybe just for a sec when shifting.

only other thing i can think of is that your idle is too high, but either way that's a very strange problem.

balance pipe should not make any significant difference if it's on the intake pipes.

[Gts-t]

FWIW

i have seen japanese high mount kits with a balance pipe fitted between the two turbo to afm pipes. Maybe it was done for fun, maybe not.....

[Sydneykid]

The problem I am having is that it sounds (and feels) like the intake pipes are blowing air out again in a pulse: front ,1sec, rear,1 sec, front,1sec.... and so it goes on.

Does anyone know why this happens?

Does this happen when it is idling or when you are driving? What rpm does it happen at? Is it at all rpm's?

Things to check;

Spark plug gap, if is is misfiring it will cause the turbos to surge.

Camshaft timing, if it is too retarded on the inlet or too far advanced on the exhaust you will get surge

Ignition timing, similar to camshaft timing.

Valve clearances, if the inlet valves are not closing you will get combustion pulses back through the inlet. If the exhaust valves are not closing you will get combustion based pulsing of the turbines.

Hope that is of some help:cheers:

[Lithium]

Interestingly enough I was talking with someone recently about GT28Rs on an RB26 - and they reckoned that unless you go a large turbine a/r (and therefore a pretty laggy twin setup) they are quite "surgey" turbos as a twin turbo configuration. If you are running ~.64 turbine a/r, then what he was telling me is true...

[c-west norway]

the problem is there both on idle and driving.

the blowing pulse dont seem to rise when reeving the engine, but it gets stronger the more load you give it.

register belt are checked, plugs, afms and o2 sensors.

I have tomei 260 cams with adj. pulleys but they have not been adjusted yet.

The head has been ported, gasflowed and rebuildt.

I believe the valve clearence is ok because I cant hear any tikking or bad sounds from the engine.

Can I find out more about cams and lift If I take a compression test??

Lithium:

What do you mean about "surgey" ?

The turbos are almost the same as the hks 2510,s so I dont believe that they are the problem.

[r33_racer]

he means when you close the throttle or back off the charged air in the intake blows back out the turbos...compressor surge.

Are there any blow off valves fitted to the piping for removal of surging?

[c-west norway]

he means when you close the throttle or back off the charged air in the intake blows back out the turbos...compressor surge.

Are there any blow off valves fitted to the piping for removal of surging?

ok. thank you for explaining, my english is not the best :whatsthat

Yes, there is a hks racing type bow fitted.

But it doesent only happen when I release the trottle. It happens all the time in both at idle and driving.

Is it possible that the air can come back in reverse when the turbine wheel is blowing the other way?

I believed these turbos have been tested as twin before?

Belive I,we read on this forum that someone used 2x garret gt28rs.

Can anyone confirm this?

Is there a good way to check if they are too "surgey"?

[StockyMcStock]

if it's happening while driving and idling, i'd put money on the problem being your ignition timing or camshaft timing is out, causing pulses back out the intake as sydneykid mentioned

[BHDave]

he means when you close the throttle or back off the charged air in the intake blows back out the turbos...compressor surge.

Are there any blow off valves fitted to the piping for removal of surging?

Thats reversion, not compressor surge. Compressor surge is where the turbo(s) is trying to pump more air than the engine can swallow and so you get the chuffing sound as the air bounces (for lack of a better term) back through the inlet. On a single turbo setup its commonly associated with turbos that have very large compressors in relation to the turbine.

[r33_racer]

oh..whoops..sorry your right..i was lost there. Glad there is someone clearing things up...that makes alot more sense.

[c-west norway]

Checked the compression on the engine yesterday, and it was a pressure of 7 bar on all sylinders.

The engine manual says 12 bar original and a limit of 9bar.

engine is a r33 with only 39000km on it.

It looked like new with original turbos when I bought it so I dont think its the bottom end.

The head has been ported and fully rebuilt With new 3 angle seats.

The man who did this says its been pressure tested too.

But thats without cams and lifters.

Right now I am starting to believe its the valves not closing entirerly and causing the low pressure and engine trouble.

Anyone else with me on this one?

Is there a way to check this without taking the entire engine out?

Is it possible for an engine builder to shim the lifters in the right posision with head and bottom end toghether?

I Must say I aprechiate your help alot!

[c-west norway]

:uh-huh:

[TurboDad]

Got any solution on this issue yet?