Chris Wilson

OK, found what it is now, thanks. So next query The turbo is the TCW76LS-P25, having a comprssor wheel size of 56 /82mm and an exhaust housing size of 25mm. Does Apexi give an estimated max HP rating for this unit, running in its efficiancy island? I was hoping to use it on an RB26DET engine at standard stroke on 87mm bore, with 280 degree duration 11.25mm lift Tomei "Procams".

My RB25DET engine R33 GTS-t came with a single, remote wastegate RX-6 series Apexi turbo on it. I know Apexi make 3 different sizes of turbo for that unit, and I need to find out which I have. Can anyone at all help me ID this thing please? Specs are as follows, taken from the IHI turbo ID plate on the turbo itself, and from the casting of the exhaust housing itself. Thanks, really desperate to ID which one this is! Spec: VA4 900 32 9804 Serial No: RHX6 03016C On exhaust housing casting : P25F

As a matter of curiosity are you guys over there allowed to run the likes of Michelin Pilot Sport Cups and Pirelli P-Zero Corsas on the road, legally? Over here in the UK we are, just wondering, your car mod laws seem a lot tougher over there...

Anyone got any accurate info on the porous block episode Nissan had with Skyline RB26 GTR engines? I believe the block castings were porous on the LH (pasenger side on RHD cars), and Nissan at first suggested an epoxy resin repair, then a factory financed short engine change. Thanks.

I want to run a Motec ecu on my RB26 single turbo engine. Has anyone converted from the less accurate cam position sensor to a crank position sensor reading off a crank trigger wheel? Engine will be MAP sensor, not air flow sensored. Thanks.

Stock cast pistons run a tight piston to bore clearance and are expected to be quiet even straight after a cold start. Because of the tight clearance and the need for silence stock set ups usually squirt oil on the bores thrust face to aid cooling and keep a quietening heavy oil film there. You can lightly groove the big end side faces of the rods with a small rat tail file to add more splash if you really want. I wouldn't bother. With a wet sump their is a maelstrom of oil splash anyway...

Need stock head bolt torques for 1995 R33 GTS-t please, these being slimmer than a GTR's no doubt use a different torque setting, and don't seem to be listed in the few RB25DET sections of the Japanese language Nissan service manual I have. Thanks

I am slowly collecting parts for my RB26 engine in my R33 GTS-t chassis job. I have moved away from modding the RB25DET engine due to the better, bigger valved head on the RB26 and superior parts availability for the RB26 engine here in the UK. I now need to address compression ratio choice. Engine spec is as follows: RB26DETT block bored 87mm. Billet steel crank at stock stroke. Tomei Carrillo pattern "H" section steel rods. Tomei 87 mm forged pistons, but NOT the oil gallery type. These pistons run a slightly lower crown height than stock, so I guess out of the box, with a stock head and stock gasket thickness they are about 8.5 to 1 ? Brand new RB26 DETT head casting, which I will mildly port and manifold match, on stock size valves with multi angle seats. Modded RB26DETT throttle bodies with 50mm plates in them. Stock plenum. 700 ish cc injectors. Tomei 270 degree duration, 10.85 mm lift cams in inlet and exhaust positions. Tomei springs. Single Apexi RX-6 turbo on Apexi cast iron manifold, with remote wastegate discharging back into main 3 inch system. Intake will have single large AFM, hot wire type. ECU will be RB25DET Power FC, as it will best match engine loom. I will use the car virtually solely for track days, road manners are secondary, as are emissions et cetera. Fuel will be 98 RON super unleaded. I may do a second map on race fuel, probably Elf turbo, about 102 RON unleaded. What should I configure CR at? I don't want to lose squish by adjusting head gasket thickness, I want to run that quite tight, around 40 thou max, for better det control. I will machine the piston crowns to adjust, and run a 1.2 mm steel head gasket (Cometic). I was thinking that some of you engine builders would have good experience of what CR works. Thanks!

Typo in the title, sump not sumo.... :headspin:

I am building an engine for my RWD R33 GTS-t. I am using an RB26 GTR block and head. I can either use the stock pressed steel RB25 GTS-t sump, with more baffling, or maybe use an RB26 GTR 4WD sump, which has a crack in the diff casing, with all this mess cut off, to make it a cast 2WD sump. It laready has a trust sump extension welded on. is it worth the aggro of using the $WD sump, my thoughts being it may help tie the bottom skirt of the block together better than the tin sump. Thoughts? Thanks.

Thanks again Mick, especially for the auto pinouts, a big help to me. Sorry i can't assist you with the Datascan, way over my head I'm afraid.

The RB26 uses 7mm stem diameter exhaust valves, probably so the stem strength isn't compromised by being partly hollow with the sodium within. RB25 engine has 6mm exhaust stem diameter and they are not sodium filled. The bigger stem diameter also gives a larger surface contact area with the guide, giving a better heat exit path into the head and waterways. Both engines use 6mm intake stem size, AFAIK.

On the Tomei Japan site they are listed at 178,000 Yen, over here in the UK they seem to sell for around 700 UK pounds.

Sorry, no pics, but the rotors were identical (one set would fit the other pump and vice versa, with same number of "teeth". The only way to get more volume is a wider gear set, or (maybe) more teeth or a tooth form change, at any given pump RPM. I had a Tomei one in my hand yesterday, that was a totally different casting with the relief valve accessable externally, not buried in the sump, and with a wider gear set. A nice thing, but at a nice price too....

I have had engines apart with the "N1" oil pump fitted, as well as stock oil pumps, and I have stripped both stock and N1 pumps. The *ONLY* difference i could see and measure between the two was a longer relief valve spring in the N1 pump, giving higher operating oil pressure. the flow must be the same between them as the rotor widths and teeth numbers were identical. Someone said the metallurgical construction of the rotors differed, i find that very hard to believe myself... My question is who makes a genuinely higher *FLOW* oil pump with a totally redsigned rotor assembly, probably a wider one? This would demand a new casting as the stock casting hasn't enough material to accomodate a wider rotor assembly. Thanks.

ace_nz, this was the thinking behind my question. I have a stock Nissan RB26DETT piston, and a stock Nissan RB25DET piston here on my desk, the crown protrusions differ as you say.... Hmmm. I am asking this as i have been offered an HKS 2.8 stroker kit, brand new, at a good discount, and am trying to work out the compression if I fit this kit into my RB25DETT block with RB25DET head.

Can someone post up standard head chamber capacities for stock RB26GTR and RB25DET cylinder heads please? Thanks.

The engine made a genuine 500 BHP at the flywheel on UK pump fuel. That was with the Apexi RHX6 single turbo on a n Apexi cast manifold with external wastegate, and a pair of Apexi hydraulic cams marked LN1, whatever spec they may be. 1.8 mm head gasket, stock appearing bottom end. RX7 FD injectors (550 cc), big fuel pump, conservatively mapped Power FC, big AFM, stock throttle body and intake system, big bore exhaust. Would like 600 BHP, car is track use only, circuit, not drag. I want to keep the same turbo and cast iron exhaust manifold, would like a forged bootom end, and convert to mechaincal cams. Can put up with quite a bit more lag than it currrently has, it makes peak torque at 4600 RPM. Thanks

That would be suprb Mick, as I am transplanting a manual gearbo into an automatic car shell. Cheers, good work!

Excellent stuff, downloaded and saved, thanks. When you get bored an R33 GTS-t auto box loom, and a manual box loom diagram pair would be fantastic.

OK, I think I have decided to stay with an RB25 or RB26 block, with RB25 DET head, modded to take solid lifters and under bucket shims using the Tomei stuff. I stripped my RB25DET engine today, expecting to find forged pistons and rods, which is how it was sold to me, but found stock Nissan cast pistons and stock Nissan rods... Oh well! So I need pistons and rods, forged. Current head gasket is a 1.8mm Apexi multi layer steel one. When I rebuild though I want to keep stock squish, so want to run a stock thickness, or close to stock thickness head gasket, I believe a 1.1mm steel one is about the same as a stock composite gasket? So I need forged pistons in 87mm bore format, to give about 8 to 1 compression., witha 1.1 mm head gasket. What's available, preferably not something from the US, as they tend to be heavy out of too big a forging die. Do JUN sell a Cosworth made piston for the RB25 pin height, or should I do the below? It's all quite complicated! Now I have another dilemma. I want to run a steel crank. Do I try and find an RB25DET steel crank (do they exist?) or do I just get an RB26 steel crank and run RB26 forged pistons? I would really like to keep it at the shorter RB26 stroke though. So at the moment I need to balance the desire to stay slightly shorter stroke and 2.5 litre, or get the seemingly more common bits for an RB26 bottom end, and put an RB26 bottome end together, for which I am sure JUN do Cosworth pistons. My final dilemma is the head. I definitely want to keep my Apexi RHX6 single turbo on its Apexi cast manifold with external wastegate. Am I right in thinking that precludes me using an RB26 head casting, as the exhaust port studs spacing are different to an RB25DET head casting? I don't want to get into adaptor plates, I'd rather stick with a modded RB25 head if the exhaust manifold fitment differs... A lot of questions, sorry, but all help eagerly sought, with gratitude. Thanks.

Just my own feel for these engines suggest the RB26 is NOT as smooth as the RB25, dynamics wise. Same as the 2.5 Soarer engine is FAR smoother than the similar, but longer stroke 3 litre Supra TT engine, or even the N/A 3 litre 2JZ-GT units. Anyway, I take what you say about capacity = torque and lower stress, but I am from a race background and I just love the sound of a high revving straight six. For sure, a long stroke 3 litre will pull great torque figures, at low RPM, but there's more to building a special car / engine than practicalities, and I would consider additional cost and leser intervals between rebuilds maybe a worthwhile downside for the "excitement factor" of something that sounds more like a race engine than a diesel, no offence. I may well end up going the "diesel" route, but I feel I should explore bothe options fully before comitting. I just like short stroke engines....

The jury is still out regarding whether I build a stock stroke RB25DET engine, or build an RB30 based unit for my track R33 GTS-t. I fancy a short stroke engine, the RB25 seems a lot smoother than even the RB26 DETT, and that appeals, I was wondering if anyone has built a seriously high RPM RB25DET engine? Maybe around 9000 RPM, built to last at those revs on the track? Is any commercially available stock stroke steel crank available for the RB25 engines? Thanks.

I have a couple of RB25DET heads here, one of which I KNOW has been overheated through water pump failure, the other is of unknown origin. I don't suppose anyone has Brinell testing hardness figures for a known good head available, have they? Here in the UK the Cosworth Sierra engine in turbo form regularly used to overheat and figures for a good head versus a "cooked" head are available. I don't want to waste money and time modding a soft casting. Was hoping someone had Brinell figures for the Nissan castings? Thanks.

I am heavily modding a Nissan Skyline R33 GTS-t RB25 DET engine. Big external wastegate turbo, 280 duration cams, steel internals, Motec ECU, blah blah. My question is idle speed control related. Why did Nissan have 3 separate means of idle speed control? It has a bi-metallic strip cold start idle up device under the plenum, a solenoid for A/C on and PAS load idle up, and a stepper motor device for normal idle speed control (and a throttle butterfly and accelerator pedal of course... :-)) My goal is a track day car, perfect idle control isn't too high on the agenda, A/C is ditched, and with the cams a fairly high idle is needed anyway (1200 RPM or so). Emissions aren't too much of a worry either. As such should i just run a conventional stepper motor idle control and blank off the other 2? I am confused as to why Nissan didn't just use the stepper motor to control the idle though, it seems unnecessarily complex. Thanks.