Nelsonmxmarc 1993 GTSt Type-M Build / Tips-tricks for HCR32 (Skyleezy!)

[frankiman]

have you looked into a gearset/synchroset for your rb20 tranny, you wouldn't want to end up like marc-andré

[TW]

Weight.

GTST's main advantage is that it doesnt have to carry around all the extra drivetrain and goodies the 26 boasts, that being said, my only options in transmissions would be an RB25 or z32, both of which weight nearly double that of the RB20. So far, with the basic essentials in my car, i've gotten it down to 1120 kg at the nearby weight station.. 1120kg is freakin nuts. I'm pretty sure the car came stock @ 1300 give or take a few. GTR is around 1450kg.. at the moment, compared to a STOCK gtr @ 280 whp, i'm looking at 4 kg per hp (1120/280), versus a gtr at 5.17 kg per hp (1450/280). So basically you would need a GTR with 362 hp to match my car head to head.

So, if i can make a 360 whp GTST in the same weight range (account for cooler, larger turbo, maybe i'll buy new cd's this winter? i donno..), i'm looking at 1130kg, unless i decided to ditch my AC system, at which point we're laughing with another 40-50 kg loss! (must not give in..)

1130/360 = 3.13 kg per hp.... It would take a 1450kg GTR, 461 hp to match.

So case in point, i want to build the lightest possible car that boasts the maximum hp that can safely be attained before having any serious issues, and i think the 20 is more than capable of that. Since my motor is running a steady 150+ on all cylinders, to bring a 26 into the equation will end up costing me much more in the end, much much much much more, and only get me as far as my 20 would have in the first place!

Plus, how cool is it running around with an RB 20 near 400 wheel? That's pretty epic if you ask me.. It comes stock with what, like 195 wheel?

would be damn epic. might want to look into the limits of the stock rb20 bottom end though

[nelsonmxmarc]

would be damn epic. might want to look into the limits of the stock rb20 bottom end though

That is a good idea.. lol

have you looked into a gearset/synchroset for your rb20 tranny, you wouldn't want to end up like marc-andré

Yup. RHD sells a close ratio gearset that will swap in no problem.

http://www.rhdjapan.com/kameari-super-close-gear-set-s13-s14-r31-r32-58307

Also Skym pointed me to a page that develops gearsets and synchros for the RB20 trans. Same basic idea, but you can vary your gearing.. Not sure i'll sway much from stock though, if i decided to change gearsets ATM. Andddd i fail cuz i cant find that damn link..


I'm going to run my 20 trans this way next season at my target hp and see. I'm interested to know if shearing gears is based on driver error, or if the power itself is sufficient to cause breakage. In theory, once you've managed to slow the trans down with the synchro and the dog teeth catch, sliding into gear should be a smooth transition, at which point all forces are lateral.. I cant imagine either 26/25 or 20 trans gearsets being made of different quality material? The 20 transmission should hold up to 360 whp none the less, or if not, i guess we'll find out

[quadracer111]

selling it? or did something happen?

Selling, as much as I don't want to. I need a winter vehicle. I already have a buyer thats meeting my asking price so I don't know what to do lol.

[nelsonmxmarc]

Selling, as much as I don't want to. I need a winter vehicle. I already have a buyer thats meeting my asking price so I don't know what to do lol.

Whoaaa thurrrr, we'll get you a new box of tampons before the snow hits, and while you're changing it, maybe you can reconsider and keep your car? lawl.

No but seriously. You don't have it as bad as us, since skylines are a lost cause in Quebec, but still. If you like the car, and are invested in it more than a daily driver, than do yourself a favour and keep it. You own a piece of history, and you're also part of a community of enthusiasts who are willing to drive 1200 km to meet. We're a pretty solid group, and without people like us in it, it makes it impossible for the skyline community to live on! So keep your damn car!.. jesus.. lol

[nelsonmxmarc]

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Posted a quick mention in the FAQ section about JIC vs. ISO plugs. BCPR/PFR are JIC, meaning the length of the plug from the seat to the top of the terminal are standard japanese length (specific for our cars), while ISO plugs like BKR7E's like that of which i'm now using, are 2.5mm shorter from the seat to the top of the terminal.

No matter; they both work regardless because 1, the variance is nearly insignificant and 2, the length of the spring inside the coil compresses enough when touching the ISO plug, so there is still contact.

[nelsonmxmarc]

Head gasket size

Saw this come up in the GTST section; wondering as well what to run for next spring, as i'll be looking at around 20 and over psi boost. Is it worth running a taller gasket to lower compression, or should i be lessening it and do the opposite? OR, do i continue to run the stock height?

Any mentions on compression? GTST is like 9:1 if i'm not mistaken?

[frankiman]

Is it worth running a taller gasket to squeeze out more compression,

a taller (thicker?) gasket will lower the compression

[nelsonmxmarc]

Yea somewhere along the lines i meant that, but "squeezing out more compression" definitely sounded retarded lol.

Fixedddd

any ideas?

[Skym]

Stock is around 8.6 for compression with 1.2mm stock headgasket -

http://www.tomei-p.co.jp/_2003web-catalogue/e105_RB20_gasket.html

Gibson GTS-R has around 7.7 with compression (metal headgasket, forged pistons). Most agree, with stock pistons that can fail (rings lands fail) under higher pressures, lowering compression helps. Especially when running above 20psi with bigger turbo. The Gibson GTS-R was running around 1.7bar x 14.5 = 24.65psi. Gibson GTS-R RB20DET was / is reliable.

Up to 20psi the 1.2mm, 80.5mm Tomei metal headgasket should work and the higher compression gives better offboost performance. But on racetrack where the engine is at higher boost levels, rpm for long periods, lower compression should be better.

[nelsonmxmarc]

Great info, as usual Skym. Appreciate it.

So a 1.5 mm gasket wouldn't hurt in respect to being reliable to the best of both worlds, on and off the track, is basically what you're saying?

1.2 seems sufficient, for what i'm after right now, we'll see how she lasts

Now in question of having my head decked - any reason to when keeping the same block? Any reason to for bedding purposes on a new headgasket? And in the same sense, won't this affect hg height (obviously VERY little but 2 thousandths of an inch, you never know.)

Just wondering on the favoured procedure to alleviate any future problems. Any other key notes for swapping a HG?

[Skym]

Yes, for reliability.

I know of one who's gone into what was said 7's (compression), stock RB20DET bottomend with over 100,000km and thicker HKS?? metal headgasket (might have been 2.0mm???). He used car for dragracing. The head had HKS 256 cams, oversized valves, etc. But like I said above, lower compression would affect offboost performance (Naturally Aspired part of engine). But reving engine, getting onto boost can solve that problem.

On dyno you can run more boost without problems. But add weight of car, etc and stock pistons can fail with higher boost levels, higher compression. More so with RB25DET that has higher compression than RB20DET.

Skimming can even out squish area's / domes in head. Commonly done on Import, V8 heads. Engine builder / head specialist should tell you if thicker headgasket is needed due to head being skimmed too much (due to previous rebuilds). How much skimmed off, depends on how non-square the head is. If you run a ruler diagonally?? across head, should notice no daylight between ruler, deck of head when it's square.

[mitch32]

Compression ratio is Volume in Cylinder BDC/Volume in Cylinder TDC. A thicker gasket like frank said will lower compression.

Compression in a turbo car doesn't give much power, its some like 3-5hp per value (so 11:1 vs 10:1, the 11:1 will have 3-5hp more). Thats what my engine builder told me anyways.

I've heard of guys with rb20's running rb26 cranks to stroke the engine out to 2.4L. I got a crank for sale if anyone wants to try it.

[nelsonmxmarc]

Might take you up on that..

Phil and i were toying with the idea of a 2.4L rb20 block. With a 26 crank and 20 rods, we would run VR6 pistons to match the bore perfectly and get just under 8:1 comp, allowing us to rev it up around the 10k area.. The math works out, its just the block will need a resleave, and even then, we're cutting super close to the water galleries.. we had no idea the walls in the rb20 were paper thin.. the 26 is pretty beefy in comparison.

We'll see.. I have a ported 20 head and bare 20 block. Just needs to go in for a quick check up to make sure there aren't any hairline cracks that could cause future failure. Was thinking of a 2.2 stroker but i think if i'm going to build a block from the ground up, it's going to have to be something pretty random / epic in the end.. lol

[Skym]

Paper thin when you bore short block. Otherwise quick thick when using stock bore. Had a RB26 short block next to RB20 short block and you can see the difference in wall thickness.