nakagusukumike Posted April 15, 2009 Share Posted April 15, 2009 I want to build a medium to high HP SR20 and was looking at the following: 2.0L SR20 is 86x86.0mm DOHC CHAIN Timing 2.5L RB25 is 86x71.7mm DOHC BELT Timing 2.6L RB26 is 86x73.7mm DOHC BELT Timing 2.8L RB26 is 87x77.7mm DOHC BELT Timing I've got a 2.8L RB26 and I used to have a standard capacity RB26 as well. I've also had RB25's and RB20's. Quite franlky the stroke on the stock SR scares me. I want to build a high reving, high boost SR. I'm wondering if this has been done and what the limits are. I calculated the following: 86x73.7 (4 cyl) is 1712.5cc or 1.7L. This is the stock RB26 stroke on an SR. 86x71.7 (4 cyl) is 1666.0cc or 1.7L This is the stock RB25 stroke on an SR. Is there such thing as a down capacity crank for the SR? If there was, it might be possible to build a motor that would spin 5 figures. Build it right, good strong internals, gaskets, bolts, springs etc.... Throw a TON of boost at it. What do you think? I CAN'T be the first person to think of this! Quote Link to comment Share on other sites More sharing options...
nakagusukumike Posted April 15, 2009 Author Share Posted April 15, 2009 SR16 or SR18 crank and get it worked? Quote Link to comment Share on other sites More sharing options...
slown280z Posted April 15, 2009 Share Posted April 15, 2009 I'm pretty sure that a fully balanced SR crank with a VERY nicely worked head (like TOMEI shimless buckets and a nice cam setup) and proper timing components (plus rocker arm "retainer/guide thing" to prevent them from popping off) are known to survive 9k plus RPM. How high are you thinking about going? Also, L4s don't have to deal with as much crank harmonics as L6s which is probably which they can rev high initially with a longer stroke. Don't SR16VE's rev 8k (or higher) stock? Quote Link to comment Share on other sites More sharing options...
nakagusukumike Posted April 15, 2009 Author Share Posted April 15, 2009 I'm talking something stupid like a 9-12K power band. How about the chain timing though? Not sure if that's a good or a bad thing at high RPMs. Quote Link to comment Share on other sites More sharing options...
PanzerAce Posted April 15, 2009 Share Posted April 15, 2009 9-12k is going to cost $$$$, but I'd think you would be ok with the stock stroke. Chain vs. Belt: IMHO, chain is WAY better. I have no empirical evidence of this, but hearing about a buddy's horror stories of belts makes me glad the L is a chain. Quote Link to comment Share on other sites More sharing options...
AkumaNoZeta Posted April 15, 2009 Share Posted April 15, 2009 I've heard more horror stories about chains breaking than belts. But I've never had experience with either breaking. From what I understand the stock SR stroke/bore will make and survive high RPMs but have the oversquare, bigger bore with less stroke, makes it more rev happy and rev quicker. I too had a fasination about making a high RPM SR20DET until I was informed about the CA18DET and the more I read about it the more I liked it and I now find that as a better engine for my personal tastes. If you were really set on doing it, what I would do is find out the maximum bore you can safely have in the SR block and get a custom crank made if you still want it more oversquared. It doesn't have to be by a lot, just a little oversquare is good. For durability sakes I would think a custom crank without boring out the block would be better so you have more cylinder walls to keep everything from exploding and you would have more walls so you can bore it out if you find its ovaled or hourglassed when you rebuild it in the future. Quote Link to comment Share on other sites More sharing options...
blueshark123 Posted April 15, 2009 Share Posted April 15, 2009 The 86x86 is a perfect motor to rev high as it is a square motor. People have revved the sr20 really high. All that needs to be done is build the bottom end(pistons, rods, steel sleeves) and head (solid lifters, big cam, springs, retainers, etc) to support the revs and actually have a cam/turbo setup that will make power up there. No sense in revving 10k+ unless you are going with a 70mm+ turbo imo. Quote Link to comment Share on other sites More sharing options...
(goldfish) Posted April 15, 2009 Share Posted April 15, 2009 I'd use the timing belt. The lighter weight of the belt will be easier to control orbiting at those rpms. Quote Link to comment Share on other sites More sharing options...
slown280z Posted April 16, 2009 Share Posted April 16, 2009 I'd use the timing belt. The lighter weight of the belt will be easier to control orbiting at those rpms. I don't think there's a way to do this without lots of fabrication. If you're set on that RPM, why not get a Busa motor, stroke it, and adapt it to a car trans? It'd probably be cheaper then doing an SR that can survive that RPM. Quote Link to comment Share on other sites More sharing options...
jc052685 Posted April 20, 2009 Share Posted April 20, 2009 Its called a ca18det Quote Link to comment Share on other sites More sharing options...
The love of JDM Posted April 20, 2009 Share Posted April 20, 2009 Whats the reason of having a higher reving sr then what normally is there? Are you planning on using this for a track for sliding? Dont get me wrong, just wanting to understand... Theres a fellow I know for many years who swapped out rb20 for heavy built sr20 specific track setup pushing 450ish in a skyline 32. His 1 and only reason to do it was to keep up very high speed along the banks of Irwindale. and then a crash lol http://www.wreckedmagazine.com/watchvideo/vaughn-gittin-jr-vs-sammy-tiger Quote Link to comment Share on other sites More sharing options...
nakagusukumike Posted April 20, 2009 Author Share Posted April 20, 2009 I've got a 32 GT-R that's an HKS 2.8L stroker touge car. I want the opposite characteristics for the Z. Free revving high boost. I'd like to stick with the SR because they are the price of a can of coca-cola. However, this is mostly just entertaining a thought. Car will be for spirited cruising and occasional midnight drag. Quote Link to comment Share on other sites More sharing options...
Careless Posted April 21, 2009 Share Posted April 21, 2009 CA18 would be a motor to look at too... but If you would like to get a better idea of the bore/stroke ratio, and not the rod ratio that is induced by the crank, take a look at the 4AGE engines built by HASSELGREN. They build some 11,000k 1.6 litre motors, but advise that a complete teardown be done every oil change... Something to think about at those RPMs... There are Hayabusa engines making upwards of 500hp that rev to the moon... Have you considered looking into other motors than standard fare SR20 as a starting point? Either way, I respect your decision because I'm doing something sort of the same with my build just cause I think it's cooler. Quote Link to comment Share on other sites More sharing options...
The love of JDM Posted April 21, 2009 Share Posted April 21, 2009 I've got a 32 GT-R that's an HKS 2.8L stroker touge car. I want the opposite characteristics for the Z. Free revving high boost. I'd like to stick with the SR because they are the price of a can of coca-cola. However, this is mostly just entertaining a thought. Car will be for spirited cruising and occasional midnight drag. I understand now, I think it is def. do able, as its been done plenty of time AND with you're location getting the needed parts is almost like going to the candy shop. Are you doing the motor work or having someone do it? Quote Link to comment Share on other sites More sharing options...
echo006 Posted April 21, 2009 Share Posted April 21, 2009 (edited) How is it that we are talking about revs here and nobody has mentioned rod/stroke ratios? The rod compared to the stroke is what really makes an engine rev-able. Look it up if you don't believe me, I swear by it. The square bore/stroke helps, but some of the best engines I have seen for revs and power are overbore, short stroke, and long rods. engine ___ rod ___ stroke __ bore _ r/s rb26dett _ 121.5 _ 73.7 ___ 86 __ 1.6486 rb25det __ 121.5 _ 71.1 ___ 86 __ 1.7089 rb20det __ 121.5 _ 69.7___ 78 __ 1.7432 sr20det __ 136.3 _ 86.0___ 86 __ 1.5849 ca18det__ 133.0 _ 83.6 ___ 83 __ 1.5909 The higher the rod stroke ratio, the better the mechanical advantage the combustion has on the crank and revs better. Granted, there are other factors such as rotating mass, balancing, valve train, and head design that have to be factored in. The Rod/Stroke ratio is a big player though in revving an engine. As far as chain vs. belt timing goes. If they are maintained properly (changed at 100k miles or less) then there should not be a problem. A belt setup is lighter (valve train inertia) than the chain and the belt does not require oiling. The lighter load allows for higher revs (mechanically speaking only, other factors play in). If i remember right, the advantage to the chain is reliability. Stretching is minimal, only is sever conditions can it ever jump the timing off and that is mostly unheard of (this is still uncommon in belt systems though). Hope this helps everyone. Edited April 21, 2009 by echo006 numbers were unclear Quote Link to comment Share on other sites More sharing options...
ZROSSA Posted April 21, 2009 Share Posted April 21, 2009 I wouldnt worry about the stroke. Remember that the cars that used to run in super touring (btcc) ran the same crank and they had a power band between 7000 and 8500. Toyotas 3sg has the same dimensions ass well. Bmw's and fords formula 2 engine used to run to 10500 with similar dimensions and that was in the late 70's. You are just going to need a strong crank and rods + the obvious head work. The btcc engines were converted to gear drive. Cheers, Douglas Quote Link to comment Share on other sites More sharing options...
Careless Posted April 22, 2009 Share Posted April 22, 2009 well start with an RB30, then. 1.84:1 rod/stroke ratio.. much closer to the 2+ that motorcycle engines have! Quote Link to comment Share on other sites More sharing options...
PanzerAce Posted April 22, 2009 Share Posted April 22, 2009 Speaking of motorcycle engines, take a look at the Hartley page if you really want something to rev to the moon, looks like their H2 engine is done/almost done (seems to be basically half of their H1 2.8L V8). Claimed up to 250hp NA, I'd say look at that (and might even be cheaper to grab that then to try to get a 'de-stroker' crank for an SR). http://www.h1v8.com/H2.html Quote Link to comment Share on other sites More sharing options...
roger280zx Posted April 22, 2009 Share Posted April 22, 2009 IMHO revs are much more dependent upon headflow/cam and overall recipricating mass/balance. Look at the honda family, almost entirely undersquare rev-happy engines with technically horible rod/stroke ratios: borexstroke rod/stroke f22c 87x90.7 1.65 b18b 81x89 1.54 b18c 81x87.9 1.58 k20 86x86 1.62 k24 87x99 1.34 All of these engines will rev high and make unbelieveable power once properly modified. I would say spend the money and time in your head and turbo, then stick the longest rod that will fit easily in there... for most engines it is counterproductive to engineer around rod length. Quote Link to comment Share on other sites More sharing options...
nakagusukumike Posted April 23, 2009 Author Share Posted April 23, 2009 I've contacted John about his 3.0L V-8 Busa Quote Link to comment Share on other sites More sharing options...
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