AngryRB

Picked up a GT3076 thanks to STT, and pulled the head off the RB30 to inspect the clearances, safe to say this isn't a 120k old engine as I was told, piston to bore clearance as double checked checked by the old man is 20thou. Must of been had a turbo on this and used at the track to get that much wear. Considering going down the forged rods and pistons route so I can wind up the boost, im assuming I could run 25psi and it will choke off to 20psi up top.. thinking maybe I should of gone a bigger turbo but im sure ill be happy for a while. anyway some pics, not sure why the pistons have a shiny mark on the top edges, im assuming that's from pinging?

If you look at the power and boost curves, it looks like once the gate opens around 3800rpm, the power curve chokes then recovers after a 1000rpm, I would guess this is gate return pipe merging gases at a 90degree angle causing back pressure on the turbine wheel, both flows are fighting each other If you have a proper dump, you'll probably gain 30kw's at 4000rpm, if you wind the boost up to 20psi at that point you might see 40kw's, both gate return and dump should flow in the same direction, probably has the effect of making it more like a 2.5inch dump.

I had to check my GT30 housing as I found that hard to believe, I don't remember even checking with my last GT30, glad you mentioned it, that's unexpected.

If its a track car then the rules change, it will spend a lot of its time in the top end, this is where a GT35 sized turbo and some 1000cc topfeeds come in along with the usual support mods, later when the motor blows, consider slapping a RB30 in there and you'll be able to re use these parts to push 400kws. You could use a 0.63 rear for the RB25 and a 0.82 for the RB30, win win..

If it stalls when coming to a stop then id start looking for vacumm leaks, and if not using a stock intake pipe with stock bov then id suggest your getting reversion. Both issues I have had, seemed worse when coming to a stop quickly rather than a gentle coast to a stop.

so you have a dodgy AFM by looks of it, your OEM coils were cheap, your BOV returns on the wrong angle, you have leaks and using a gates timing belt. Its no surprise that it doesn't run perfect, best just to buy the stuff quality and new to avoid all this stuff around with it,

You had the car tuned and apparently it is fine they keep saying, when they tune a car they have an probe up the exhaust yeah? So its hard to understand this fuel consumption problem unless they just tuned it mostly on a full throttle. To get 18-20L/100km you'd have to be on the gas pretty heavy, if most of your driving is normal then surely the injectors arnt putting the fuel in, not sure if a car would run if its injectors were open 70% all the time, you have 600ish cc injectors so unless they are more than 50% open all the time then it doesn't make sense. The only way to use this much must be from somewhere else. If the reg is leaking and getting worse, you'd have a a few very rich cylinders and maybe some very lean from less pressure ,eg cylinders 5 and 6 leaning If the fuel return was hooked up wrong you could have a build up of pressure from fuel not being returned to the tank, at full vacumn this build up could be relieved by being sucked thru the reg into the manifold from a shit reg and getting you your high fuel consumption. If the O2 sensor appears to be acting weird then surely this is an indicator of an outside factor ( REG) that is leaking independently to the other sensors etc, so trys to fix the overfueling but only adds to the roughness. A continual changing of the system to try and normalise and outside fault? On the dyno they assume that there is no leaking reg, and that each cylinder gets the fuel they are programing, not sure but if they are using the exhaust probe to check the fuel mixture they could be tuning it thinking its ok but in reality its false because the regs adding fuel too. When on dyno you'd think this sort of fuel consumption would be obvious, and could diagnose it by engine braking and checking the fuel mixtures etc. just a few ideas

so is the standard BOV still considered adequate for these size turbo's, eg GT30/GT35.. Ive seen aftermarket ones and they come with a range of springs, eg 6psi , so if using that then boosting under 6psi would give a shhhzutututu which might be a way around the legal side for people that want that, but you'd still have some reversion is that right? On a stock rubber intake, the BOV return is quite close to the turbo inlet, so maybe modify the intake pipe to mimick that, so the entry point is close to the inlet and theres a couple of turns before the AFM is connected.

I just checked and my canister is doesn't recirculate either, but wont hurt to check that the fuel return hose is hooked to the right nipple on the pump just in case their is a blockage.. Also, what if the fuel reg was cracked/damaged/internally rusting? you could end up with fuel leaking into the manifold, which would make the O2 react, but this would certainly make it thirsty.

Its easy to mix them up, I found this on my falcon, it runs from the fuel tank to the charcoal canister then under vacumn a valve allows the vapour into the manifold to be burnt. Not exactly sure on the skyline but it would be same or similar. The vacumn line outlet on the pump is designed to not let fuel though, mine wasn't on that outlet, resulted in 20L/100km and the manifold was soaking with raw fuel, on deceleration the motor choked and lost power til the fuel was cleared out of the manifold.

If it were me, id take the turbo off and send it to Forced Performance for a 73mm comp wheel modification, cheaper and more effective result than Twin scroll and less work too. Then you can join the HTA thread and brag about how good it is lol... http://store.forcedperformance.net/merchant2/merchant.mvc?Screen=CTGY&Store_Code=FP&Category_Code=Turbo-Upgrade

If some one connect the vacumn line incorrectly on the pump, then you will get 20L/100kms cause instead of allowing only vapour from the tank to the manifold, raw fuel gets sucked thru under vacumn conditions. Who did the pump?

That hose looks like its not a good fit and the pipe even looks oval shaped?

Theres heaps of room underneath and it isn't much harder than having it higher up, mine was on a low mount 6 boost and still was enough room. There was no boost control issue, it did seem a bit laggy though, but not sure if it was just the twin scroll ATP housing or not.

If going forged, is it ok to go 88mm pistons if limiting power to 350kw's or will the block crack? would be extra torque for free thinking about wisecos with the coated skirts, theres a few threads with mention of tightening the piston to wall clearance down to as small as 2thou without issues, so maybe 2.5-3thou for a street application might be doable and the slap might be very minimal. Using E85 the piston would be running cooler than 98, and not being on a track the pistons would have chance to cool down between floggings as you cant be drive flat out on the street anyway or even at the drags for long.

a tad over 300kw on E85? you must be running about 14psi or the tune needs more timing put in, that shouldn't be too boring at all, maybe it just needs another tune with more boost and using a EBC to awaken the turbo more.

what about a worn harmonic balancer/ key if it was moving or loose down there wouldn't that give some of the symptoms?

pulled a piston out today, measured it and it has 21thou of wear on the top side plus 1.5thou on the bore, so that makes about 23thou piston to bore clearance, why would someone sell a good R31 for $400 if it had a good motor in it? I think I must be in the wrong state, need to move down south for the goods..

you guys have a lot of confidence in 26+ year old engines, this engine I have was supposed to be a 1 owner 120k motor, so its a lottery finding that "good one", not sure where you pick them up for a slab cause all wreckers want $700 for a motor.

maybe you should borrow someones splitfires cause those OEM ones you got sound like they could be duds.. hard to believe these issues don't show up on a dyno, if it pings in 3rd then that's a tuning issue isn't it?

Yeah I'm not expecting it to sound as good as an RB, just after a bit of a deep note.. a lot of them sound very droney which im not after. i'll probably just go a catback system with a magnaflow oval or similar then..

I have a Falcon ute XR6 2001model, its very quiet so looking to hopefully give it a good quality note without it sounding stupid. I've read the ford forums but wondering how Jap made exhausts would sound on a falcon 6, are they designed specifically for high revving Jap engine I have a JASMA rated Cannon that sounded good on an R33, so thinking if it would sound good or not. I have a 2 1/4inch system with one resonator, a rear muffler and a 200cell cat currently. also, how does the length of the tail pipe affect the sound?

How do you know they are original? seems too cheap for anyone to make a profit from that sale Splitfires I would think would be better than OEM, when you see 1000hp GTR's i don't remember them using OEM, usually theres a set of splitfires, for example the Mercury Motorsport 34GTR uses Splitfires and that's what was recommended to me.

The block ive bought is worn, if I rebuild it then I can hopefully avoid any issues such as uneven comp, low comp, odd knocking noises, blow by etc etc I don't plan to take the engine out again after this so don't want any suprises or failures, i hate piston slap and noises from worn out engines too if it were for track then id take the chance.