SKiT_R31

The turbo does pose a huge exhaust restriction, but my point is that larger exhaust doesn’t mean less backpressure. If the turbo car isn’t making enough power and exhaust gas, the exhaust from the turbo back reacts just the same as it would on an N/A.

You don’t want backpressure on any modern car, N/A or otherwise - needing backpressure started with old carby cars with high overlap cams. Having a larger diameter exhaust’s increase backpressure, as it increases the volume of air you need to move which cools and slows it, this is the doughy feeling or the loss in response/low end power people feel. Having an exhaust suited to your application (cams/compression/capacity/boost) should mean the pipe size is suited for the best exhaust velocity that matches your peak power output (or where you want peak flow efficiency). That said, if you put it on the dyno, there would be f**k all in it. I've driven many N/A & N/A+T cars before and after with small to large exhausts, with turbo's and without and apart from sound and a bit of a doughy feel, it really makes SFA difference. The same could be said for people with stock RB20DET's running 3" & 3.5" exhausts, these cars can make the same power and have a similar exhaust gas output as N/A RB25/30's but just doesn't start this shit everytime someone mentions it.... If he wants to have a large exhaust then let him, it’s his car and his deal, I don’t know why you all care so much.

haha, reading through this you all seem like massive assholes. For starters, its going to do the same damage to an N/A motor/exhaust as it would to a turbo motor and exhaust. And hektic drifters do it all the time for the ‘lols’; I see this as exactly the same (regardless of power/performance). It’s stupid in them and its stupid in this, BUT if its your thing then who cares, go for it. There is nothing stopping you from doing it, a standard one that people use on turbo 'drift cars' will work fine, you'll just have to drop a few rpm on stock ecu (obviously cant have it at the same point as your fuel-cut limiter). Yes its illegal, so I’d recommend leaving it switched off on the street but you will also have to decat your car or it won’t work (and would f**k your cat anyway) which kills puppies but does give a bit of a performance gain. It's not likely going to hurt your motor any more than bouncing off the limiter otherwise would, the main thing it hurts is everything after your engine - aka in your exhaust (cat/o2/mufflers/gaskets) You already have a huge exhaust, and if you get an ignition-limiter, then like a champ you should fit a small wet shot of nitrous to your car for track use as it'd be setup ready for it. (Heaps of people blow up cars on nitrous by driving past fuel-cut rev limiters and leaning out)

ugh... Cheers for the info on power steering and other clearances, didnt even think of accessories - do these all bolt up? I have a complete RB26 in mind, I am aware that running the loom is the best option but it is not the path i want to take, I'd rather leave an rb25 in it rather than change the loom and wiring. Running the RB26 ecu, I cant see what is different... The ignitor is the same (yes the plugs are different but wiring matches), afaik all the idle gear operates the same, cas the same? Only differences i can tell are the injectors (which i will replace that section of loom) and the AFM, which is fine as i have a single Q45 wired in, which the safc can convert into 2x rb26 afm signals. I run an RB26 microtech in my RB25 R31 with an RB25 loom, I jsut cant see what is different... I will probably fit an RB26 powerfc at some point also. With clearances, is it the factory piping that is the issue? Turbo inlet or outlet? I'm pretty handy with a welder and can make my own piping...

Hey All, Long story short, I want to put an RB26DETT into my R33 GTS4. What issues am I likely to have running it on the RB25 loom? Can I just use all the rb25 sensors (inc afm which i can adjust using SAFC), idle gear, ignitor and just swap the injector wiring harness and run the RB26 ecu? Any issues with ATTESSA or variable steering on the different ECU? What other changes would be required...? Also, GTR sump the same bolt pattern as GTS4 RB25DE (which is same as stagea afaik). Ta, -Dan

I'd quickly snap this up if you'd liek to post it, exactly what i'm looking for.... If you can neatly slice it in half (scratch 2 different lines for me to match it up) It could make it possible and I can weld it back together...?

Ugh, I can see how the cost can quickly skyrocket... I can do an N1 RB26 pump, crank collar and 2x 1.3mm restrictors for ~ $450 posted, which is affordable (but I really couldn’t manage the >$1k-$1.5k brand name pumps). The main issue here is that I'll have to get the crank machined & the collar fitted, which means i may as well get the lot sent off and balanced... I might find a Stagea block to build up... As for compression, I was just a bit sick of the higher compression motor but after driving some low comp's I think I'm over it . The way I see it, on my current setup (ignition timing/cam timing/tune etc) on 7PSI the engine should have a dynamic compression ratio of 15.5:1. This is the same as a turbo motor on ~10.5psi, or an 8.0:1 forged motor on 14psi (or 8.4:1 on <13psi). The way I see it, as long as you’re in boost (and are running the difference extra) it should be equally as responsive, dependant on ignition timing possibly better. It’s the off boost that is the worry, especially with larger turbo's and because of this and it being my daily; I am going to run higher compression than I said before.

Yeah cheers, I reckon I will when I get it all started. Head studs are something I've been considering, since they really should be replaced anyway plus they are just more reliable when torqueing, I can source some for $176 posted. GTR rods for Strength? Weight? I can get ARP rod bolts for $110, or "Forged ultra-light I beam" rods which include the bolts for $500, but not really sure if it’s really necessary for my power goal, also cautious about changing rods as I thought the crank would need the counterweights re-balanced? Does anyone know the stock piston and rod weights? Out of curiosity... Really trying to avoid taking it anywhere for anything more than a head shave/acid dip, I'm in Tasmania and most workshops are unreliable and very expensive. And even some basic things (like crank balancing) needs to be sent up to the mainland. Put it this way, if I gave them all the gear now I doubt I'd get it back by new years and I'd owe more than the cost of the original components. So for now I'd rather limit what I did to it to keep it within what i can do myself. I know everyone screams to get a new oil pump for peace of mind, but if I maintain the stock rev limit and just fit restrictors/return, surely I'd get away with the standard pump (After all, I'm not rebuilding because my bearings are shot). Just don’t want to spend the money if it’s not absolutely necessary (I’d at least inspect and fit the turbo pump though). As for compression, I need to do the calculations for compression and clearances, but I'm pondering fitting the low comp forgies (8-8.4:1) and machining the block to sit them above deck height to increase compression and compensate for the head gasket (better squash, remove HG hotspots and more focussed initial pressure - with domed head and dished piston?) Hmm, lots to think about. I like to take different routes to keep things interesting, no point having the same parts and power outputs as every other skyline on the road .

As above...

Do you still have the RB25DET AWD block? This is the non-neo right? Ta,

Hey, Do you still have this?

Yeah, the power I'm after is reasonably tame, somewhere in the mid 200's (as a daily), but I'd rather over build as I've been known to get carried away.... I'm really tempted to have a play with nitrous for the lols as I want to keep a reasonably responsive turbo for track/hill climbs/driving, but wouldn’t mind power on a button for drag days, etc. I've gotten a bit sick of my N/A+t, it makes a healthy 201kW at all four on 11psi, and managed a 13.1 1/4 mile. But I’m bored and want more, it needs a 7GPH 150psi water+meth spray nozzle on any boost above 6psi at stock ignition timing. I'd like to remove the water and just run it on fuel like E10 95ron (cheapest fuel down here, 25c/L cheaper than BP ultimate), run whatever boost and not have the stress of watching my egt's at their limits. I've done the high comp road to the death, I’ve sill got a >~13:1 N/A car, an RB30DET AND and RB30E+T... And I have a feeling this motor has had a headshave before... It doesn't seem to be able to handle as much boost as it should, reads about 190psi on all pots... Meh, regardless I think low comp is the route I'll take this time, plus they are the best value pistons I can get... Stamp duty is only for $1k+...???

Interesting... I could get a WISECO piston and Eagle H Beam rod kit for another ~ US$300 (including "IARP SERIES 2000 BOLTS"), but I was under the impression the crank should be re-balenced with a rod change...?

But i would then need oil restrictors?

Hey All, The time has come to rebuild my RB25DE+T and convert it into an RB25DET (for my 100 thou service). Is the oil pump the same? I've never had an issue with oil supply, but want to make sure its going to hold up (while i have the engine out). I do have an old blown RB25DET block to pilfer shit from, but there is no point swapping if they're the same (esp. since mine has less km plus i know its functional). Trying to do this relatively cheap as I am not loaded, buying pretty much everything from the US since the Aussie dollar has near hit parity, makes things heaps cheaper - Also doing all the work myself. At the moment my shopping list is; 8.0:1 - 8.4:1 CR forged WISECO pistons, inc rings, wrist pins and locks ($750 + $90 postage) ACL Rod & Main Race bearing's ($135 + $40 postage) Full RB25DET gasket set ($90 + $55 postage) RB25DET Timing Belt, Idler and Tensioner ($125, combined postage ^) + Water pump ($70) ^ Parts total is roughly $1500 after random extra's (I'll replace exhaust studs, etc) Is there anything I am missing? I am going to fit the factory RB25DET water->oil cooler (that sits where the oil filter goes) and would like to fit the RB25DET oil squirters to the N/A Block, does anyone know what is involved in this (i.e. does the N/A block have the mounts or whatever??). I'll probably fit an adjustable cam gear for more ideal cam timing (as N/A is supposedly different)... Will get this done before Christmas, possibly run it in on stock turbo then see where I go from there. Down the track I'd like to fit a GT3071, Greddy plenum & PFC, and possibly up the rev limit within a safe range (~7500rpm??) as I have had experience with Greddy plenums and they seem to push power past the limiter (and I could do with the extra top end). Keen on opinions... Ta, -Dan

Uhk bugger, cheers for that. RB26 has crossed my mind, can i run the RB25 loom and just use an RB26 injector loom, and fit an RB26 powerfc and set it to my single AFM? My engine is factory N/A, I can fit low comp forgies but wont have get oil squirters, are they easy to fit (if i pilliage from my RB25DET block?), also does anyone know if the oil pump would be the same? Cheers again,

Hey all, Pushed my car a bit too hard on the weekend (Ran a 13.1 1/4 mile though) and have done some damage to the bottom end, dropped about half the compression on cylinder 5. My car is an R33 GTS4 RB25DE+T, so has a GTR gearbox and AWD sump. I have a normal RB25DET short block spare, just curios if i can pull the top off and just swap the blocks? I know the RB25DET block will bolt up to the gearbox, but is it the same as the AWD sump? I havent done an engine swap in an AWD before, is it possible to leave the sump/front diff in the car, or does it have to come out to manuever the engine into the box etc? Cheers

I think he wants to wind his boost back...? "KnightRiderR33" Are you sure you dont have somesort of boost T in the vauum line for the wastegate? And/or are you sure that the vacuum line is properly connected? To trouble shoot, try running a fresh vacuum line directly from the wastegate to the compressor housing (bypassing the factory 2 stage boost controller). If that doesnt work then a new actuator is a good option as yours could be leaking/seized, if you pull the circlip off the wastegate flap and disconnect the arm your car will drive around on a couple psi (hopelessly slow) but it will same your turbo and your motor in the meantime.

Wind like 30 degree ignition timing into it and then run 98

VN's are soo disgustingly ugly imo... I was talking about power to weight, VN is 125kW to 1300kg (96kW per tonne), VS is 147kW to 1385kg (106kW per tonne). VS also has better economy, IRS (optional) ABS, airbags etc. VN: http://redbook.com.au/used-cars/details.as...id=129F692865E0 VS: http://redbook.com.au/used-cars/details.as...id=129F692865E0 edit: VS II's are even better at 1372kg or a ute at 1350kg (possibly sacrifice handling...)

*with extinguisher and fire blanket handy... Lol, as much as commodores are dirty pushrod Bogan boats, it is a pretty good suggestion. These have the best power to weight out of pretty much all the commodores (light vs chassis, decent ecotec motor) and mod pretty well. I ran a flat 15 in a mildly modded VS (chip, silent lukey exhaust and pod) which had 115kW at the wheels (mates car). He then combined that with a bored out intake (home job, took the mouth behind the tb it thin as it would go and roller rockers and saw 125kW atw. If you were to expand upon that and pull off the (disgusting cast iron) heads and give them a fair shave, manifold spacer, mild cam and some better management and I reckon you could get ~ 100kW per tonne. And that’s without mentioning how easy it is to stroke those engines (which popo would never know about). An IRS model with HD sways, good springs and excellent shocks with some wide wheels and good tyres (easy get some 18x8.5's or something from a newer model without attracting attention), as mentioned the VT-VY brake upgrade and fit an LSD and don’t forget some 3.7/3.9 diff gears, it would be a pretty good daily and track car, and quite quick off the line. But very very bland, and boring, and still quite sloppy compared to an import, anything early or Australian most likely will be though... I’m a big fan of R31’s, and when I was on my P’s the power was good enough, but if you’re after numbers they’re not overly ideal, and the VS mentioned above decimated me time in my original rb30e (with 108 at the treads, exhaust/timing/XF/CAI).

Nah pretty sure the LED's usually go out when you crank

haha fair enough, I drove a TRD 4AGZE MR2 when i was on my P's (fair few years ago now), was a mad fun car just had to be really quick and confident on the wheel.

^ or AW11 MR2 with the 4AGE, same boat but lighter(?) and rear engined.

Do you have 12V at the injectors? Even if they are pulsing from the ECU they need a 12v feed to function, this caught me out both times I've wired an RB25DET into R31's. There is a big grey ugly plug which you won’t have anything to connect to that needs a loop back for power. Just stick a multimeter on your injectors with the ignition on and see if they have 12v, if not I can tell you what you need to wire up.