Gt30 Low Mount Tune Results

[Lithium]

Wouldn't the tiny R33 turbine housing (~.48a/r) end up creating HUGE amounts of back pressure, and resultantly heat when the exhaust gases from an RB25 breathing 19-20psi of boost at high revs is trying to force its way through?

I would just not try to run that kind of power through the RB25 turbine housing.... I wouldn't be surprised if swapping to a VG30 one would make the world of difference.

[paulr33]

yeah it certainly does make sense. but it is a highflower rb25 housing and they can make 250rwkw on 1.3bar ish. 19psi is around 1.4bar so he should be expecting around 250rwkw i would expect ? but with more lag as the front comp housing is much bigger

[Lithium]

Yeah - I wasn't 100% sure on that one, I thought the 250wkw cars were possibly running the VG30 turbine housing. There is definate varience between dynos though, is this reading done on a dyno which reads consistant with other ones which have run 250wkw?

I know this could sound stupid - but were any runs tried at lower boost - such as the 1.3bar mentioned by paul? Maybe exhaust gas temperatures are becoming insane at 1.4bar, the thing might even be able able to match the power level on a slightly lower boost level?

Do you have a decent dump pipe?

What kind of intake/intercooler system are you using? Is there any chance that there could be an air leak somewhere?

[GunMetalR33]

NO air leak and my zaust is just a straight pipe out from the turbo with a canon like tip (no cat or anything like that). I am currently running 1.3 bar, what is that in PSI????

I have gotten rid of the knock by fixing a few cells in the ignition map. I think the zaust housing on the turbo is bigger than standard as it has been hi-flowed...

So far the story is that I have about 247rwkw on 1.3 bar with no knock but I cant increase the timming as this will cause knock.

I will put the dyno graph up at lunch time, just need to find a scanner

[GunMetalR33]

Here is the dyno Graph:

[The Mafia]

man, 19psi? I that a stock bottom end? If so.. thats gonna kill it!

<{POST_SNAPBACK}>

[GunMetalR33]

It will kill the head gasket before the bottom end...

[paulr33]

psi wont kill the engine, heat and the tune will

[The Mafia]

just thought you might bend a rod running that high of boost.

Good luck anyway, hope its tuned safely.

[GunMetalR33]

just thought you might bend a rod running that high of boost.

Good luck anyway, hope its tuned safely.

<{POST_SNAPBACK}>

Yea, cheers mate.

She is running a fairly safe tune, thus lower power figure from expected.

I just though of something else, could it be that my FMIC is at its limits now.

Its a Bar and Plate design and is about 600mm long by 300mm high and about 60mm thick??? It might even be a GTR one but not sure as I bough tit second hand.

How could I check that this is the case, inlet temps??

[paulr33]

the most likely answer is no. airflow makes power so look at the air outlet system. what size a/r is the turbocharger? did u try a dyno run with exhaust dropped to see if that made a difference? the gt30 comp is usually fair strong and flows stacks loads and you may find the hiflowed rb25 rear is too small. its good cos it will reduce lag but youll lack in top end, which is what you are seeing as it cant flow enough gas (or it could be spinning out of efficiency)

[paulr33]

if you wanna try it check pressure before fmic and then at throttle body

shouldnt be much difference. 600x300 is fairly standard and it should flow ok.

[GunMetalR33]

if you wanna try it check pressure before fmic and then at throttle body

shouldnt be much difference. 600x300 is fairly standard and it should flow ok.

<{POST_SNAPBACK}>

Its not so much the flow but the cooling efficency that I am worried about. At 19 psi the air after turbo compression would be very hot, I though that maybe my cooler is not good enough to get the temps back down.

I did notice that when the car has been sitting in the the sun for awhile the preformance is lacking until I do a few km's to let the FMIC cool down from the heat soak, when at least that's my theory.

[MattSR]

"Its not so much the flow but the cooling efficency that I am worried about. At 19 psi the air after turbo compression would be very hot, I though that maybe my cooler is not good enough to get the temps back down."

Nup - this side of things is probably fine. Ive seen this before and im 100% positive that its the turbine housing causing backpressure which is making it overheat.

Id be tapping the exhuast manifold and measuring that pressure in there. With a GT30, anything more than 1.5:1 ratio of backpressure to boost is too high.

Cheers,

Matt

[MattSR]

Look at it this way, you're trying to use a 350hp turbine housing on a 600hp turbo. It just aint going to work to its full potential.

[GunMetalR33]

Look at it this way, you're trying to use a 350hp turbine housing on a 600hp turbo. It just aint going to work to its full potential.

<{POST_SNAPBACK}>

OK, so it looks like this is the maxium power that I will get without changing the zaust housing to a VG30

How much help would an zaust cam be in this situation?

[R31Nismoid]

none

[MattSR]

It may help a little if you advance the cam timing, but this is only a band aim solution that will have to be reversed if you address the cause of the problem (turbine housing)

[GunMetalR33]

How much help would an zaust cam be in this situation?

<{POST_SNAPBACK}>

I was under the impression that a lumpier exhaust cam would help the engine breath thus making more power at the same boost level????

[MattSR]

You are correct, however its better to have the turbine housing matched to the application. you can then use a more conservative cam and get a better spread of power.

Using a BIG cam to fix a SMALL turbine housing isnt a good combo. while it will help, you will find that the turbine housing only wants to work well ion the lower half of the rev range, while the longer duration exhaust cam will naturally want to work in the higher rev range.

Its all about the combo