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Stroked Engine Building Questions For The Pro's Out There...

GTRNUR

By GTRNUR,
in Engines & Forced Induction

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GTRNUR Grand Master

GTRNUR

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So my plan is to build a stroked RB26 and make a torque monster of an engine. Ive read all there is to read about stroker engines on the forum and have been particularly interested in Mark99 and RPMGTR's RB29 builds and their successes in achieving what they set out to do.

This would be my first GTR engine build, though i have all the tools for engine assembly and am not a stranger to assembling performance engines. I will be getting assistance from someone who has built 500kw engines before but intend to do 99% of the work myself. My goals are to keep the RB26 block size to make fitment not a problem. Im aiming for max capacity, highish compression (9:0 or more), and a moderate size turbo system. (2530's/T517z's)

I want monster mid range torque, dont really care about power at the end of the rev range because thats not where most of the driving is done. I will sacrifice top end RPM to gain mid range torque... so i dont have to rev it as hard. It should make 350kw as a maximum goal realisticly. Anymore than that i think is getting a little un-practical for the street. Im planning on using some CP raised pin pistons and a long rod, probably pauter and some sort of aftermarket crank either HKS or a GT500 spec crank. I have access to a great machine shop that can add a 2-3 mm to the crank stroke (80mm max im thinking), and then run a smaller big end bearing in the pauter rods (1.85" rod big end bearing). As its not going to be a huge reving engine i doubt a few mm will reduce crank strength too much that its a worry. 80mm will give 2850cc as opposed to the 2770cc of the HKS/tomei cranks. A real 2.8lt.

Ive done the math on various engine combinations and it would seem (but i dont really know...) the upper maximum is possible around 43-45m/s, with a safe limit of around 40m/s. This was based on an RB26 at 10,000 - 11,000 RPM. This data is assuming a full drag engine of course. I just want reliability for the street so I like to factor in some over engineering. Data from CP about what is safe seems to be hard to come by.

So my questions for the pro's out there that want to share some information...

1. What is considered a safe piston speed, assuming your using a CP piston ?

Ive read that 450hp is a more or less maximum for the 05u R32/R33 block if its driven like a mad man. Above that they aparently have a reputation of cracking along the side of the block due to the block twisting... according to my "search engine results"... is there any truth in this. Who can say...I am not sure whether to build use an R34 RB26 engine as a core, or if I should build a bottom end in a 24U block and just source a complete head instead.

2. Will the 05u support a 350awkw engine that will be making considerably more torque than the average 2.8lt, or should I just get a 24U block and be done with it? What about R34 GTR blocks...?

3. Engine assembly tolerences. When assembling engines of a "built" nature, are all the specs kept to be fairly standard, or is are a few of the tolerences loosened up a little, such as main and big end bearing clearences to improve oil flow and bearing cooling etc? What about changes to end float thrust to allow a little more oil flow , so the thrust bearing isnt carrying too much load from that heavy clutch when your foot's on the pedal and your about to launch?

4. What about piston - bore clearances? Does everyone generally machine their blocks for 87mm if using an 87mm piston (assuming the piston manufacture's built in clearance 0.003" or whatever will be ideal)?

5. Internal engine parts coatings.... Specifically teflon coatings for the piston side skirts to reduce piston/bore wear due to the nature of the stroker engines having more piston rocking. But also teflon coatings for main and rod bearings, and ceramic coating piston crowns. Ive had competition coatings in brisbane do coatings for quite a few engine parts for me, but ive not heard of the GTR croud getting in on this yet. I figured I'd give the ceramic crown coatings a miss due to the RB26 having oil squirters for piston cooling so why bother with ceramic coatings, but what is the general concensis on teflon coatings?

I think thats about it for now. Im sure there will be many more questions to come.

Cheers,

Ian

Edited by Vspec R33

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