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Want more KW out of my RB20DET

HR31GT

By HR31GT,
in Engines & Forced Induction

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HR31GT Contributor

HR31GT

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I have HR31 Pasage gt serIII, with eccs rb20det, auto, 3", big fmic, 2.5" cooler piping,hks air pod, just recently installed a boost controller and upped it to .9bar, and its a bit laggy but it hits at 3000rpm. Looking to get more go(especcially more torque and bottom end_as funny as that sounds) out of it and thinking of either getting my ecu remapped, put an rb25det turbo, or fmac. And also as I live in brisbane it would be good to know any workshops that dynotune and have much experience with rb20's any help would be appreciated. Any ideas guys as i'm sure we all go through same stages........

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Cubes Grand Master

Cubes

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HR31GT,

So you have the older RB20DET. From memory it has a 248duration inlet cam which gives slightly more top end but causes the bottom end to be gutless. The R32 RB20DET has a 240duration inletcam and a 240duration exhaust cam, I guess this is why the new R32 RB20DET apparently has a little more poke down low and in the mid.

You could try fiddling with a set of R32 cams in it.

Some time ago a few people fiddled with R32 RB20DET NA cams. The only difference is that the inlet cam is a 232 duration which gives more bottom end and slightly more mid range. The car will be faster on the road even though it may pull a few kw's from the peak power figure.

If I were keeping my RB20DET I would slap a 232duration R32 RB20DE cam in to it and leave the exhaust cam the way it is or if I had the money to spend $400 or so on an exhaust cam I would go the 256 duration just to open up the top end a little more. Slap on a RB25DET turbo and pump 17psi in to it.

The only problem with the RB20DET's is lag when you want to make big power, some times even though you end up making more peak power the street speed will be slower.

HR31GT Contributor

HR31GT

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It does have eccs silver top rb20det in it,,,,,,,also i just been rising the boost and it seems to have a boost cut at around 0.8bar, is that normal....unless i unhook the factory bleed valve it wont go over 0.8bar, but if i unhook it starts to idle lower and it dont seem to be right.....any answers on that???

Cubes Grand Master

Cubes

Posted
Posted

nope its not normal to have a boost cut at .8bar unless you are running the non-silver top RB20DET ECU?!?!? Not sure on that one though.

My boost cut is up around 18psi.. It vary's with the day. On a warmish normal day it is around 18psi where as on a cold night if you wind out third or fourth depending how cold it is she will boost cut on 16psi. Damn scary when it does as you think you have broken some thing.

I've bumped my boost up to first 16psi and now i've gone to 17psi which pulls rather hard until around 5500rpm where boost starts to drop to 12.5psi.

I'm also running around 22degree's timing which makes a big difference to power delivery.

Unless your AFM is playing funny buggers causing the boost cut.

I'm not sure what it is with mine but every now and again it appears that boost rises and as it does the power delivery is not smooth. The power feels like it dips then picks up again. If I pull over and remove the AFM plug wiggle it around then plug it back in again all is normal?!?!

MM2death Grand Master

MM2death

Posted
Posted
My boost cut is up around 18psi.. It vary's with the day. On a warmish normal day it is around 18psi where as on a cold night if you wind out third or fourth depending how cold it is she will boost cut on 16psi. Damn scary when it does as you think you have broken some thing.

My 32 is exactly the same.

Scott

WazR32GTSt Grand Master

WazR32GTSt

Posted
Posted
HR31GT,

So you have the older RB20DET. From memory it has a 248duration inlet cam which gives slightly more top end but causes the bottom end to be gutless. The R32 RB20DET has a 240duration inletcam and a 240duration exhaust cam, I guess this is why the new R32 RB20DET apparently has a little more poke down low and in the mid.

You could try fiddling with a set of R32 cams in it.

Some time ago a few people fiddled with R32 RB20DET NA cams. The only difference is that the inlet cam is a 232 duration which gives more bottom end and slightly more mid range. The car will be faster on the road even though it may pull a few kw's from the peak power figure.

If I were keeping my RB20DET I would slap a 232duration R32 RB20DE cam in to it and leave the exhaust cam the way it is or if I had the money to spend $400 or so on an exhaust cam I would go the 256 duration just to open up the top end a little more. Slap on a RB25DET turbo and pump 17psi in to it.

The only problem with the RB20DET's is lag when you want to make big power, some times even though you end up making more peak power the street speed will be slower.

pumping 17psi into the rb25 turbo with its ceramic exhaust wheel is asking for trouble... they are only good at 14psi or below so keep that in mind

Cubes Grand Master

Cubes

Posted
Posted

What is the killer of the ceramic exhaust wheel?

Overspeed is no. 1 and then excessive heat/detonation.

When you increase the engine RPM the engine requires more airflow. As the engine RPM increases so does the turbo's shaft speed in order to keep up with airflow demand. An RB20 consumes less air than a RB25 so for a set boost pressure the turbo spins slower on the RB20 than it does the RB25. In turn this gives you a little more head room to run more boost and possibly match the air flow to make as much power as the turbo did on the RB25.

The other problem that blows the ceramic exhaust turbine is excessive heat. This is caused by running around a track flat out. I've heard of ceramic turbo's blowing with simply 12psi in this instance.

The japs have been doing it for some time now. 1.1-1.2bar on stock turbo's.

I initially had mine tuned at 15psi then I bumped it up to 16psi. For the last year i've been running 17psi. Although that 17psi is only up to 5500rpm where boost starts to drop down.

It also comes down to the turbo its self. Some times you get a good one some times you get a crappy one.

I've had the car for over 2 years now and racked up 60,000km's with the turbo pumping 1.1-1.2bar for a majority of the time.

When a car detonates it can also blow your turbo as its possible for a bit of spark plug to break off and smash in to the exhaust wheel. It all comes down to tuning and ensuring there is enough fuel around to keep things cool.

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