Rb25de Vct Performance Modifications

[Brentmcd12]

i wanna know other than full 2.5 exaust hiiflow cat extractors.. CAI pipe Custom 3inch intake.. airpod filter...

what throttle body mods can u do ?? ive herd u can upgrade to a XF throttle body ?? the RB25 T/b is pretty big tho.. the xf is like 84mm tho i think...

anyways wat about things like aftermarket camshafts ? what does every 1 use ??

also variable cam gear on the exaust side i herd was good because its too hard trying to adjust the the VCT intake side unless u get both aftermarket camshafts..

and then Aftermarket ECUs what is ther to use ??

im also planning on going RB30DE later on... so these pre mods to the head would be great..

also other than pulling the entire head off for a port n polish ive herd it isnt really worth it...

as much as i want more torque at lower revs for daily driving i also want to be able to have decent top end power too...

and dont say turbo.... hence why im in this topic...

cheers

Brent

Edited June 21, 2007 by Brentmcd12

[Eug]

a throttle body upgrade has always intrigued me. in an NA system the ability for the motor to breath & exhaust un-restrictively will yield the quickest results.

out of the people here; the only one i know that's done extensive intake modification would have to be a man called don (donestoto ??) - his old motor had a twin throttle body intake. you may have heard of him in and around the r31 scene. best bet would be to do a search for his rb30de in his r31 wagon which he used to take to the salt lakes.

aftermarket cam shafts should be sweet, depending on what kind of duration and lift, you can choose to suit your power range. a set of poncams should give you a nice fat midrange and a tough idle. alternatively you can get the stock ones reground for a budget upgrade.

variable cam gear on the exhaust side only, because the intake is variable already; thus there's no point in doing it. unless of course you have a non-vct r32 rb25de, or an rb26 head. best to speak to your mechanic and tuner to see what they are capable of and what they recommend.

aftermarket ecu, some people use the gts-link, i personally use a piggy back safc ii. you can go all out with a microtech or an e-manage which will have loads more functions and tuneability. again speak with your tuner/mechanic to see what they recommend and are comfortable with. the end result is only as good as what your tuner can extract. sit down, speak with them, set out your goals and applications and break it down into individual components, what they do and how to do it.

rb30de would be sweet, i'd love one... just a case of justifying the money. correct with the pre modification... the intake and stuff will all be good for that, all you'd need is a retune to accommodate the added fuel with the bigger block.

in terms of port and polish. i haven't done it, but from what i have spoken with from other people who do port and polish mods (not rb motors though) it's well worth it. that said the rb heads do flow reasonably well, and port matching is definitely well worth it in my opinion. it's certainly something i'd consider down the track, while your there oversized valves, valve springs will definitely remove restrictions and allow the head to flow much better.

the key to getting low rev driving and decent top end is all in cam shaft selection and tune, they will shift the power band where necessary.

me personally, i'm a suspension nut. i've done my fair share of mild power mods with minimal gain, and to be honest at the end of the day its a number. if you want worthwhile mods, concentrate on how to make the most of your existing power, think drive train, shorter (or was it taller?) gearing, lightened flywheel, light 1-piece tailshaft, light weight rims, etc. etc. they will have the biggest impact on seat of the pants feel. you might only be making 120rwkw, but you'd be making the most out of it.

by all means i'm not trying to sway you - just something to think on, a different approach just to add some dimension and adding a bit of context for further discussion.

hope this helps

eug

p.s. - how are the extractors coming along brent?

[GTS4WD]

Eug is right. Work as much as possible on freeing up the engine. Things like Mandrel Bent Exhausts, Hi, flow cats, manifolds, extractors, CAI etc.

I dont know much about this in terms of RB engines, but what about shaving the head? Increasing Comp Ratio?

Cams can reep alot of rewards! It depends on what you will be using the car for. If its just daily driving, I really suggest you get a set of poncams! This will give you alot of midrange and a little high range (not much though). You want power on tap when you need it for street driving, so thats why you want mid range.

there are other ways too to increase the performance of your car, lightened flywheels, brakes, loose some wieght, short shift kits (read a thread where some bloke cut .4 sec off his 1/4mile time just by installing a short shift kit!), coilovers, sway bars, strut bars etc etc.

All these things add to the experience of driving your car.

I dont know much about ECU's but why dont you just re-tune the stock one?

[Eug]

manifolds, extractors

I dont know much about this in terms of RB engines, but what about shaving the head? Increasing Comp Ratio?

I dont know much about ECU's but why dont you just re-tune the stock one?

brent already has a very nice set of extractors

spot on, shaving the head or decking the block would be a good idea if the head is off to do some work... be weiry about piston:valve clearance. again speak with your mechanic, or a nice thin gasket should help also.

rb25 ecu can be reflashed, i am not too clued in on it; but the rom can only be written/flashed once but then needs to have the chip changed if you want to retune. it ends up being an expensive exercise and the flash has to be done first time and done right. rb20 can be reflashed over and over again.

[Brentmcd12]

my car is fully decked out suspension wise and handelling and gearbox... etc...

thats why im onto power mods now..

i dont think i would go as far as port n polishing or shaving the head...

i think ill definatly be looking into camshafts and ecus to match..

i have adjustable cam gear for the exaust side comming...

so i think i might leave it at that..

eug extractors are ausome... well they look pretty good .. lol the paint still hasnt burnt off because it never gets driven it just sits in my garage and i do mods to it

they had to cut the end pipe off short to get the clearance but yeah all is sweet... =] i bout a hiflow cat as well.. all the rest is 2.5 cat back with a small hotdog ressie its not mandrel unfortunatly.. i dont think its really worth getting it changed.. well c

4 weeks till i can drive it and find out what it is like and what i should get re cams...

hopefully i will have the adj cam gear on the exaust side...

will i need to change my timming / petrol octane to suit the change from advancing the cam ?

i was thinking i could upgrade to the turbo injectors but i dont even know if these stock ones are maxing out...

i dont actually think a throttle body upgrade is possible.. the design is just too unique for the plenium.. oh yes i just got 3inch pipe too ..

http://i4.photobucket.com/albums/y133/bren...hIntakePipe.jpg

hows that looking bar the shit shots coz my camera lens is broken atm...

ohh i was reading that u can disconnect VCT buy unplugging the solenoid connector.. i was wondering is ther much of a difference or does disconnecting it just stop it from opening up at 3500 4000 rpm or wen ever ?

i guess ill have to find out all these things for my self once i get to drive it

[Cubes]

VCT enables just off idle and disables at approx 5000rpm to improve mid range acceleration. When it disables at 5000rpm ish that then improves top end.

So doing what you say will actually make it feel soggy through the mid range and top end will feel the same. You 'may' think its actually quicker up top as the mid range will be less punchy so gives the feeling of it having better top end.

[Brentmcd12]

ohh fair enough..

the mid range seems shit as it is so i better leave it alone then...

[GTS4WD]

will i need to change my timming / petrol octane to suit the change from advancing the cam ?

i was thinking i could upgrade to the turbo injectors but i dont even know if these stock ones are maxing out...

RB20 det uses top feed high impedance injectors 270cc

RB25 det uses side feed high impedance injectors 370cc these are the same as the sr 20 det.

RB26 uses top feed low impedance injectors. 440cc

And no, you wont have to change your timing. If you advance your timing, you will have to run higher octane. Its a good idea to adance timing, helps a little bit.

Why not get a thinner head gasket? Or just shave the shit out of it? Hi comp NA RB!

[Brentmcd12]

does any 1 know if u can use a Greddy E Manage ultimate with the RB25DE ??

ive herd it works on all cars altho that the Rb25DE isnt listed on there manual... ??

would ther be much benfits from usuing it if it works ?

Edited June 26, 2007 by Brentmcd12

[SKiT_R31]

does any 1 know if u can use a Greddy E Manage ultimate with the RB25DE ??

ive herd it works on all cars altho that the Rb25DE isnt listed on there manual... ??

would ther be much benfits from usuing it if it works ?

if it works on an rb25det it will work with a DE

[are33]

Apexi AFC NEO, These can be wired into your ECU for air-fuel ratio adjustment, and you can control aspects of the VCT. A mate of mine has a non turbo 33 like mine with one of these, adds decent power.

[Eug]

Apexi AFC NEO, These can be wired into your ECU for air-fuel ratio adjustment, and you can control aspects of the VCT. A mate of mine has a non turbo 33 like mine with one of these, adds decent power.

i think the neo controls vtec not vct. two different systems...

[GTS4WD]

i think the neo controls vtec not vct. two different systems...

NEO = Vtech

Whether or not it works on VCT.. another question..

Edited July 5, 2007 by GTS4WD

[Eug]

i think the PCM controls the VCT on the RB engines.

[SKiT_R31]

i think the PCM controls the VCT on the RB engines.

so you cant get it to work with vct? then this makes me asad panda, was looking forward to tuning mine when my car gets going (ive got ACF4)

so theres definately no way to dodge it? what about other methods to change when it kicks it? jaycar tool?

[Eug]

you can include the VCT in your tune.

the way it's done is to tune it with the VCT activated and you get a power graph/tune/whatever.

then you tune it with the VCT de-activated and you get another power graph/tune/etc.

then you put both graphs on top of one another, where the two lines cross is the best place to have it activated.

[Brentmcd12]

so when i go for a dyno tune to get my wolf 3d v3 installed im guessing they will do this to tune it ?

[Eug]

so when i go for a dyno tune to get my wolf 3d v3 installed im guessing they will do this to tune it ?

sit down and speak with the tuner... they might have different ways of doing it.

they should do it...

[SKiT_R31]

you can include the VCT in your tune.

the way it's done is to tune it with the VCT activated and you get a power graph/tune/whatever.

then you tune it with the VCT de-activated and you get another power graph/tune/etc.

then you put both graphs on top of one another, where the two lines cross is the best place to have it activated.

cant the time VCT enables/disables be altered without an aftermarket computer (other than afc4) if so how? cheers

[GTS4WD]

so when i go for a dyno tune to get my wolf 3d v3 installed im guessing they will do this to tune it ?

Seriously mate.. make sure your tuner know their shit when it comes to Wolf 3d.. cos their FREAKING hard and complex ECU's to tune.. see if you can talk to somoene who has had their Wolf tuned by ur tuner and get some feedback..

Had a mate got his 3d tuned on his 4G63 by some bloke who didnt have much experience with the ecu.. engine ended up shitting itself after only 2,000km!!! Had to buy an entirely new engine!

Just make sure you trust this bloke