Jump to content
SAU Community

Recommended Posts

dont decomp it with a spacer, it ruins the squash, loses you power with minimal benefit for knock resistance. With tech these days, you should be able to make the same power with the higher compression as with lower compression, befrore you need forgies. You'll make more power from stock management, or with aftermarket management and a good tuner you can make just allmost as much power as the stock internals can handle anyway - and a decomp wont make that any better, it will just hit you with the same n/a squash issues (which arent ideal for boost) combined with making less power per psi due to the lower compression.

that said, the answer to your question, you need decompression plate (i think 0.7mm) and 2 standard head gaskets, which will drop you to about 8:1 (which is too low for a 25 anyway, as normal rb25dets are 9:1) thats a 1.7mm increase.

you'd be better off with a copper headgasket, thicker than standard (1mm) at ~ 1.8mm, its a bit of decompression, puts you closer to the rb25det stock compression, combine it with some colder plugs (7's or somthing) and it will be spot on.

Link to comment
https://www.sau.com.au/forums/topic/262987-rb25de/#findComment-4503380
Share on other sites

dont decomp it with a spacer, it ruins the squash, loses you power with minimal benefit for knock resistance. With tech these days, you should be able to make the same power with the higher compression as with lower compression, befrore you need forgies. You'll make more power from stock management, or with aftermarket management and a good tuner you can make just allmost as much power as the stock internals can handle anyway - and a decomp wont make that any better, it will just hit you with the same n/a squash issues (which arent ideal for boost) combined with making less power per psi due to the lower compression.

that said, the answer to your question, you need decompression plate (i think 0.7mm) and 2 standard head gaskets, which will drop you to about 8:1 (which is too low for a 25 anyway, as normal rb25dets are 9:1) thats a 1.7mm increase.

you'd be better off with a copper headgasket, thicker than standard (1mm) at ~ 1.8mm, its a bit of decompression, puts you closer to the rb25det stock compression, combine it with some colder plugs (7's or somthing) and it will be spot on.

i'm at 378bhp atf at the moment at 10.13psi boost and i've fitted meth/water injection and hoping for 400bhp+ when i get it mapped at 12psi boost.i have another rb25de engine i was thinking of lowering the comp to 8:1 and big turbo to push the rb25de to the limit,has anyone tried doing this,thanks in advance john

Link to comment
https://www.sau.com.au/forums/topic/262987-rb25de/#findComment-4504253
Share on other sites

whats the specs on your water meth injection? I've been looking into it, using a siemens methonol injector and a microtech MF-1 Microfueler ecu, cheap as chips.

if you've got the engine out of the car, why dont you just change the slugs? Dish in higher power applications is a big plus, and if your after big power, it would make sense, you might be eble to get some 25det or 26dett pistons, or for lower comp - even 30e pistons would be better...

anyway, i reckon you'll be able to get some good numbers out of it, im assuming its an r32 rb25de?

Link to comment
https://www.sau.com.au/forums/topic/262987-rb25de/#findComment-4504673
Share on other sites

whats the specs on your water meth injection? I've been looking into it, using a siemens methonol injector and a microtech MF-1 Microfueler ecu, cheap as chips.

if you've got the engine out of the car, why dont you just change the slugs? Dish in higher power applications is a big plus, and if your after big power, it would make sense, you might be eble to get some 25det or 26dett pistons, or for lower comp - even 30e pistons would be better...

anyway, i reckon you'll be able to get some good numbers out of it, im assuming its an r32 rb25de?

its a devilsown 150psi pump with 1gph nozzle pre turbo and a 3gph pre throttlebody set to inject at 6psi boost,it works well but i'm only on the 1st washertank of meth/water and i have to use about 3 tanks to clear all the carbon out of the engine,then i'll get it remapped.its my spare engine i wanted to lower the comp on and get it ready for when this one fails and its an r33 rb25de,and i suppose i want to keep to standard internals because over here(england)lots said don't bother putting a turbo on it you'll never get any power,i have already proved them wrong and just want to do it a bit more

Link to comment
https://www.sau.com.au/forums/topic/262987-rb25de/#findComment-4505255
Share on other sites

what else have you done to that motor? how long has it been running at 10PSI? quite interested as i have done the turbo conversion on my RB25DE (1994) just running stock gear, no aftermarket stuff...

pfc,480cc injectors,255litre fuel pump,fmic,25 row oilcooler,fpr,coldairbox with feed pipe,splitfires,good plugs,turbo elbow/downpipe 3" upto 3'75 to 4.5" tailpipe all xs power,decat,r32 gtr clutch,kenlowe electric fan and modified plenum but you have already seen this in the sticky on gts+t its been at 10psi about a year and 8.5psi for 1.5 years before that, i think alot of power comes from cold intake i know shawny as the same mods without the plenum and he's 50bhp atf down and i put it down to all that intercooler pipe over an hot engine, and i have done a oildrain mod

Edited by lammy426
Link to comment
https://www.sau.com.au/forums/topic/262987-rb25de/#findComment-4508487
Share on other sites

there are members of my car club pushing 310rwkw (400hp at the wheels - not at the flywheel) on stock compression rb25de in a street/drift car. also a competitor in d1nz running a rb25de+t at the same power levels in competitive drifting.

set up right, you can run the high compression and put out lots of power. just get the tune right and dont skimp on supporting mods.

Link to comment
https://www.sau.com.au/forums/topic/262987-rb25de/#findComment-4508498
Share on other sites

there are members of my car club pushing 310rwkw (400hp at the wheels - not at the flywheel) on stock compression rb25de in a street/drift car. also a competitor in d1nz running a rb25de+t at the same power levels in competitive drifting.

set up right, you can run the high compression and put out lots of power. just get the tune right and dont skimp on supporting mods.

thats great to know,how can i contact them i'd like to discuss mods with them,are they on this site or do you have an email address i just want to get the most out of it ,400atw is great i want some of that,many thanks john

Link to comment
https://www.sau.com.au/forums/topic/262987-rb25de/#findComment-4508508
Share on other sites

tiger white is the name of the drifter who runs a rb25de+t.

he has a few videos on youtube and you may be able to google some information about his set up.

the info i've found so far its 346wbhp but that will do me for now,just got to find out what boost he is at to get 30 bhp more than me ,most of his mods are the same except turbo

Link to comment
https://www.sau.com.au/forums/topic/262987-rb25de/#findComment-4510959
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • Did this end up working? Did you take some pictures?
    • And finally, the front lower mount. It was doubly weird. Firstly, the lower mount is held in with a bracket that has 3 bolts (it also acts as the steering lock stop), and then a nut on the shock lower mount itself. So, remove the 3x 14mm head bolts , then the 17mm nut that holds the shock in. From there, you can't actually remove the shock from the lower mount bolt (took me a while to work that out....) Sadly I don't have a pic of the other side, but the swaybar mounts to the same bolt that holds the shock in. You need to push that swaybar mount/bolt back so the shock can be pulled out past the lower control arm.  In this pic you can see the bolt partly pushed back, but it had to go further than that to release the shock. Once the shock is out, putting the new one in is "reverse of disassembly". Put the top of the shock through at least one hole and put a nut on loosely to hold it in place. Put the lower end in place and push the swaybar mount / shock bolt back in place, then loosely attach the other 2 top nuts. Bolt the bracket back in place with the 14mm head bolts and finally put the nut onto the lower bolt. Done....you have new suspension on your v37!
    • And now to the front.  No pics of the 3 nuts holding the front struts on, they are easy to spot. Undo 2 and leave the closest one on loosely. Underneath we have to deal with the wiring again, but this time its worse because the plug is behind the guard liner. You'll have to decide how much of the guard liner to remove, I undid the lower liner's top, inside and lower clips, but didn't pull it full off the guard. Same issue undoing the plug as at the rear, you need to firmly push the release clip from below while equally firmly gripping the plug body and pulling it out of  the socket. I used my fancy electrical disconnect pliers to get in there There is also one clip for the wiring, unlike at the rear I could not get behind it so just had to lever it up and out.....not in great condition to re-use in future.
    • Onto the rear lower shock mount. It's worth starting with a decent degrease to remove 10+ years of road grime, and perhaps also spray a penetrating oil on the shock lower nut. Don't forget to include the shock wiring and plug in the clean.... Deal with the wiring first; you need to release 2 clips where the wiring goes into the bracket (use long nose pliers behind the bracket to compress the clip so you can reuse it), and the rubber mount slides out, then release the plug.  I found it very hard to unplug, from underneath you can compress the tab with a screwdriver or similar, and gently but firmly pull the plug out of the socket (regular pliers may help but don't put too much pressure on the plastic. The lower mount is straightforward, 17mm nut and you can pull the shock out. As I wasn't putting a standard shock back in, I gave the car side wiring socket a generous gob of dialectric grease to keep crap out in the future. Putting the new shock in is straightforward, feed it into at least 1 of the bolt holes at the top and reach around to put a nut on it to hold it up. Then put on the other 2 top nuts loosely and put the shock onto the lower mounting bolt (you may need to lift the hub a little if the new shock is shorter). Tighten the lower nut and 3 upper nuts and you are done. In my case the BC Racing shocks came assembled for the fronts, but the rears needed to re-use the factory strut tops. For that you need spring compressors to take the pressure off the top nut (they are compressed enough when the spring can move between the top and bottom spring seats. Then a 17mm ring spanner to undo the nut while using an 8mm open spanner to stop the shaft turning (or, if you are really lucky you might get it off with a rattle gun).
    • You will now be able to lift the parcel shelf trim enough to get to the shock cover bolts; if you need to full remove the parcel shelf trim for some reason you also remove the escutcheons around the rear seat release and you will have to unplug the high stop light wiring from the boot. Next up is removal of the bracket; 6 nuts and a bolt Good news, you've finally got to the strut top! Remove the dust cover and the 3 shock mount nuts (perhaps leave 1 on lightly for now....) Same on the other side, but easier now you've done it all before
×
×
  • Create New...