Rb26 Boost Problem

[endless]

Well, i've upgraded my stock turbos to R34 N1, gone in for tune last Friday only to find the car won't boost past ~10psi

the setup is also very laggy - makes 2psi almost immediately then very slowly creeps up to a little over 10psi as it proceeds through the rev range.

Running a profec B which was set to 14psi on the stockers before swapping them out, this was set to max with no change, then later disconnected on the dyno to see if problem - the boost stayed the same.

Was suggested that i check 3 things;

- cat

- pre-load on gates

- cooler pipes

Dropped the exhaust tonight, cat looks fine, both actuators are adjusted as they should be (1/2 hole to full hole tension) only thing i have found is a TINY spot where air may have been leaking from a cooler pipe - though this pipe has not been touched since the stock setup, so would suggest it has always been there. Also a few runs were done on the dyno and surely with the ebc disconnected the boost leaking out would of been easily heard from this?

I will also add that since the tune, aside from the obvious loss of power it runs just as nicely as it did before.

Any other suggestions as to what could be causing my boost problems?

Edited December 15, 2010 by endless

[Moodles2]

Do you have cheap HKS -copy split dumps by any chance? (could be fouling on the dump if so)

Did you re-use the actuators from the stock turbos, or whatever were already attached to the R34 N1's? (Could have turbo shuffle where 1 turbo is doing all the work)

[endless]

No used HPI bellmouth dumps, wastegate flaps move freely.

I did use the actuators that i got with the N1's.. will have to test them. I watched the rear turbo actuator arm whilst doing a dyno run and it didn't move at all - front one obviously a bit harder to see!

Edited December 15, 2010 by endless

[XKLABA]

sounds like the boost controlller has ben put back on the wrong way and your running waste gate presure

[GTRNUR]

Doesn't explain the lag though. They should spool like stock turbo's, or near enough too.

Before any major retune I suggest doing the following:

1. Check the wastegate line pressure that the wastegate flap begins to move at. Adjust them to be identical. The stock actuators lift off at 0.6 bar from memory.

2. Pressure test the intake system from the MAF sensor hoses through to the plenum. The smallest leaks all contribute to LAG and an inaccurate tune. There is no point tuning a car if you can't guarantee your intake system is leak free.

[endless]

Well i've since rechecked all my cooler piping and replaced any clamps that looked a bit worn - this made little to no difference.

Bought a compressor & checked the wastegate line pressure just then. Both don't crack open until 0.6 - 0.7bar (9psi)

Really at a loss at what to do now?!

[MrStabby]

Well, i've upgraded my stock turbos to R34 N1, gone in for tune last Friday only to find the car won't boost past ~10psi

the setup is also very laggy - makes 2psi almost immediately then very slowly creeps up to a little over 10psi as it proceeds through the rev range.

Sounds like a wastegate is leaking or has next to no preload from the actuator (sorry i dont know what the half hole to full hole thing means, but since they open at 9 psi sounds ok). 9 is almost 10... hmm - at what rpm does it hit 10?

I you have a boost leak it will run extra rich.

[endless]

I meant if you were to sit the actuator arm over the mount so it slips on and off, use the length of the hole that the mount goes through worth of tension - if that makes sense.

Doesn't hit 10 until about 5k, which is ridiculous.

[DVS JEZ]

take it for a quick drive with the cat removed and just the exhaust exiting the front pipes, this should remove exhaust restriction from the equation.

if this doesnt fix it, try the old ultimate boost (WARNING THIS CAN BE FATAL TO THE ENGINE IF NOT DONE CORRECTLY) take the boost signal hoses off the actuators and take the car for a drive and in 3rd gear some where safe and legalish, accellerate hard BUT KEEP AN EYE ON THE BOOST GAUGE VERY CAREFULLY. if the boost skyrockets back off straightaway, this will diagnose if its a boost controll issue

[endless]

I didn't mention but i've since had a decat put in - same result.

While we had it on the dyno the EBC vac line was disconnected completely so the gates would keep shut, resulted in same problem!

You can see why i am lost on this now...

[MrStabby]

I didn't mention but i've since had a decat put in - same result.

While we had it on the dyno the EBC vac line was disconnected completely so the gates would keep shut, resulted in same problem!

You can see why i am lost on this now...

Crank the preload up so they open at 15 psi, then try again (carefully as DVS32R says) with the boost signal disconnected an plugged. Remember that the exhaust pressure on the wastegate flapper also pushes it open (as well as the boost pressure on the actuator diaphram).

[Adriano]

BOV leaking?

[endless]

Crank the preload up so they open at 15 psi, then try again (carefully as DVS32R says) with the boost signal disconnected an plugged. Remember that the exhaust pressure on the wastegate flapper also pushes it open (as well as the boost pressure on the actuator diaphram).

Cheers for the advice. I set the pre-load higher however i was only able to equally set the actuators to 11psi. Reason being is the sleeve fitting that screws on ran out of adjustment, even though there is more thread left on the arm!

Took it for a spin and it definitely felt more punchy like it should. Did a run in 3rd and boost was going a little higher now 0.8bar (about 12psi) i turned the boost up and was heading for 1bar @ 5k before i backed off. Correct me if i am wrong but i should have more boost at this point?

I suppose this tells me it is certainly the actuators / pre-load adjustment.

Does this mean the actuators need replacing? I want to run 1bar low boost, hmmm perhaps i could shorten the actuator arms to use up more of the thread?

Edited January 23, 2011 by endless

[scotty nm35]

It probably means the flap is blowing open. 9psi with the compressor doesn't take into account the exhaust pressure pushing on the flap, it sounds very weak. A stronger wastegate spring is needed to hold it shut better.

I just converted mine to 19psi by adding a simple spring, it used to be a 7psi actuator, it needed 14psi to open with the compressor, now it takes over 25psi.

My boost curve dropped off around 4psi before, now with no controller, I logged a nice flat 19.

The best way would have to be new 1 bar actuators though.

[MrStabby]

I have the same turbos and they come with actuators so i assume we're running the same actuators as well. I didnt do the install or set them up tho so i cant add anything else other than maybe try with the boost controller now with the extra preload and see how that goes.

Here's my setup with boost curve; EBC is an old greddy profec

[endless]

That is very innovative scotty! Not sure if i would trust it as a long term solution though..

Need to go check 4th to compare now i'll have a look at a few more dyno results with these.

MrStabby by any chance have you got a photo of how your actuators are adjusted? I am also running an old greddy profec b.

Edited January 23, 2011 by endless

[endless]

Looking through a few other dyno results, although they are done in 4th looks like i should be able to make 18-20psi by ~4300rpm.

If i was able to pre-load the actuators more i think this would help. What is stopping me from shortening the arms slightly for more adjustment?

[MrStabby]

MrStabby by any chance have you got a photo of how your actuators are adjusted? I am also running an old greddy profec b.

This was as good as i could get from the phone;

Also i made a graph of boost response on my car for stock turbos compared to 34 N1s. 1 bar at about 3900, but i *think* my cam gears are still at 0 degrees. Very few data points so not reliable.

[MrStabby]

That is very innovative scotty! Not sure if i would trust it as a long term solution though..

Looks good to me! Cool solution - should be fine long term as the spring will be nowhere near its elastic limit (that is where it is permanently stretched). Just need to make sure all wires etc are tied clear of it, which i'm sure he's already done.

[XRATED]

Ha ha... I've had this problem a couple of times before.

In all honsty, check your cooler pipe work for rags... check both comp wheels... block off your bov's... check the oil feeds to both thurbos.... has anything else changed other than the turbo's?

If you want to rule out from the wastegates back, wire them shut for testing.

Cheers

Justin