Need some help. rb20 is slow as a dog when out of boost.

[dawgmode]

im messing with a 20 with a 3071r (small back). stock bottom end and a modified intake man. she doesnt hit full boost until 5k. After that she is a beast. she makes 370 at 19psi. BUT the problem is anything under 5k, theres nothing going on. We just bought some tomei 270's so that will bring the spool down a few hundred rpm but i still need to get her more responsive for the bottom end power...do you think bumping up compression will help with the bottom end OR should i not be worrying about that and focusing on building the head to be able to rev higher?

[Supraclean]

What are you using for an exhaust manifold? The size of your intercooler piping?
Check out M13s build in the gts section, he is running a similar turbo and hits boost sooner.
There is a couple of threads that cover things you can do to increase your spoolup time already. Off the top of my head is good tune, adjustable cam gears, poncams or procams with headwork. Port and polish would defiantly help along with a twin scroll or equal length manifold made by a company that isn't ebay.

[dawgmode]

can you post a link to the thread?

thanx

[Supraclean]

http://forums.gtrcanada.com/gts-discussion/43736-gts-upgrade-list.html

Read threw that. Altho most of it is Rb20 there is some 25 stuff in there and the same idea applys.

[M13]

that's weird, mine hits 16PSI around 4100.

boost starts building around 2100

[Skym]

Probably running a bigger exhaust A/R. Response, spool times drop with bigger A/R.

Best cams for response are stock cams with adjustable camgears. Even Tomei Poncams probably would work better if adjusted correctly with camgears to get more hp down low.

For example with Greedy / Trust TD06 turbo kit on stock RB20DET with stock cams, adjustable camgears (around 370hp at engine in videoclip below) -

http://www.youtube.com/watch?v=dKcqwovVnZw&feature=related

Adjustable camgears do help to produce more hp, torque throughout powerband or more at lower revs or more at higher revs (playing with powerband shape or basically where you want the hp, torque to be). For example on RB20DET when adjusted to get more hp throughout powerband, including high rpm's (more for street, racetrack use) and bonus is boost builds 300-400rpm?? or so earlier -

http://www.uniqueautosports.com/Dyno/yx32gtstdyno.gif

Porting, etc slows velocity of air down at lower rpm's, so stock ports are best (slightly polishing ports probably could help increase velocity of air).

Also shorter exhaust runners help, as get more low to mid hp. Longer runner exhaust manifold runners = mid to high with loss of hp down low.

On intake side it's the opposite, where shorter runners = more mid to topend hp. Stock intake manifold is best for more hp at low to mid.

[M13]

Probably running a bigger exhaust A/R. Response, spool times drop with bigger A/R.

Best cams for response are stock cams with adjustable camgears. Even Tomei Poncams probably would work better if adjusted correctly with camgears to get more hp down low.

For example with Greedy / Trust TD06 turbo kit on stock RB20DET with stock cams, adjustable camgears (around 370hp at engine in videoclip below) -

http://www.youtube.com/watch?v=dKcqwovVnZw&feature=related

Adjustable camgears do help to produce more hp, torque throughout powerband or more at lower revs or more at higher revs (playing with powerband shape or basically where you want the hp, torque to be). For example on RB20DET when adjusted to get more hp throughout powerband, including high rpm's (more for street, racetrack use) and bonus is boost builds 300-400rpm?? or so earlier -

http://www.uniqueautosports.com/Dyno/yx32gtstdyno.gif

Porting, etc slows velocity of air down at lower rpm's, so stock ports are best (slightly polishing ports probably could help increase velocity of air).

Also shorter exhaust runners help, as get more low to mid hp. Longer runner exhaust manifold runners = mid to high with loss of hp down low.

On intake side it's the opposite, where shorter runners = more mid to topend hp. Stock intake manifold is best for more hp at low to mid.

How do you want to adjust the gears? Intake and exhaust retarded or advanced?

[Nismo_line]

so since i am going to be doing my timing belt should i throw in some adjustable gears? and same question as above?^

[M13]

so since i am going to be doing my timing belt should i throw in some adjustable gears? and same question as above?^

do it.

For me I've done it so much so it takes like an hour to remove my belt so I thought I'd do it when and if I get cams.

[Skym]

From what I understand, with cam gears your adjusting the cam timing or how long valve is open, similar to adjusting duration of cams.

Tomei show what camtiming settings do here -

http://www.tomei-p.co.jp/_2003web-catalogue/e092_adjust-p.html

Also I think overlap between intake, exhaust cams has an effect, as turbo like the opposite of what works on a NA engine.

Stock RB20DET cams have same duration on intake, exhaust cam shaft's (240 duration), which increases response, peak hp. If you stagger cams with lower duration on exhaust cam, higher duration on intake cam, lift to match, can gain more hp, torque at lower rpm's.

Tomei explain that here with Type-A, Type-B RB26 cams -

http://www.tomei-p.co.jp/_2003web-catalogue/e070_cam_RB26.html

This is an example with HKS Vcam (VVT), but same applies to adjusting camgears, where you can increase bottomend hp, torque.

Power -

http://1.bp.blogspot.com/_vhpEGyEVhes/TNDTTwynRSI/AAAAAAAACdM/BAFDs2gYWks/s1600/Vcam26+vs+28+-10.jpg

Boost -

http://4.bp.blogspot.com/_vhpEGyEVhes/TNDTUbxUzCI/AAAAAAAACdU/jx7ASpDvBwc/s1600/vcam26+vs+28+-10+boost.jpg

As you can see RB26 can have more hp, torque down low than RB28.

You can see that RB25DET has an unfair advantage over RB20DET with VVT. It's not just the capacity difference that helps.

I was looking at a modified R34 RB20DE NEO head, as has VVT. Or modding R32 RB20DET head for VVT (oil supply, etc to VVT). Then use R34 RB20DE NEO ECU with Nistune to run engine, VVT (quicker, better stock ECU). It's something I'm still researching at the moment. Still need to find out if NEO head is solid or hydraulic.

[M13]

I was looking at a modified R34 RB20DE NEO head, as has VVT. Or modding R32 RB20DET head for VVT (oil supply, etc to VVT). Then use R34 RB20DE NEO ECU with Nistune to run engine, VVT (quicker, better stock ECU). It's something I'm still researching at the moment. Still need to find out if NEO head is solid or hydraulic.

I did that research before.

The NEO head uses solid lifters.

[Nismo_line]

ok so sounds like i should put some cam gears in so anyone know of a used set for sale would prefer hks but will look at anything lol

[Skym]

Thanks M13.

Foxracingcanada004, modified stock camgears (strongest teeth) and can cost less than $100 to make. Cut out center of stock camgears, drill, tap? holes in middle of each arm that's left over, put a metal disc in the middle with adjusting slots on outside of disc with nuts, bolts holding it together, 4x mount holes + extra hole for front of cam. Cam specialist (or someone with CNC machine) should be able to make them. But probably need to etch some degree marks into camgears.

Adjustable stock camgears -



On some camgears the teeth can wear, make belt slip, take out valves, etc (expensive). Being such a critical part, I would be very careful as to what I use.

About overlap, as far as I know, turbocharged engines likes less overlap and NA engines more overlap. I think more overlap = rougher running engine at idle or I guess a lump as some call it and less over lap is the opposite.

[Nismo_line]

i think i might pick up some hks ones or something of good quality

[Skym]

Not all of above mentioned manufacturer products are good. Airfilters, camgears, BOV's (old technology), sometimes ECU has problems for example. Internals of engine, like cams, pistons, etc are of good quality and proven to be good up to 2000hp with Methonal fuel.

Those stock adjustable cam gears are used on a NA R32 Skyline rally car with upgraded cams.