A more power

[carsick]

Putting aside the hard-on comment and turning to the stroke, is the torque increase purely a function of larger bore, higher compression ratio and increased V.E.? Or are there stroker mods for FJ's? I like a little extra leverage.

[racerman_27410]

Putting aside the hard-on comment and turning to the stroke, is the torque increase purely a function of larger bore, higher compression ratio and increased V.E.? Or are there stroker mods for FJ's? I like a little extra leverage.

from what i can gather most of it stems from the added displacement and more efficient/complete cylinder filling by using the stock valve sizes  (more displacement = better pump= improved cylinder filling)


you can get the big HP numbers with larger valves but the trade off is a loss of low end torque and i wanted (and got) a torque monster  

i'm only running 10:25 compression so i can use pump gas.... all my numbers could be considerably higher albeit by virtue of adding more compression but TBH i cant really exploit all i've got right now... on the street anyway.

track day with hard bags and still get the holeshot ?  

KOokaloo!

[derbybrit1]

Interesting stuff!  Never have seen that at the track, on sleds nor otherwise with nitrous.  Any concern for strength in a boosted application?  The other question is how fast to react are they to changes?  I mean, you could come up with window switches somehow to turn things off after a certain temp, but the big blue squirt gun can do a lot of damage in a very, very short time if there's a problem with fuel delivery.

An interesting way of ensuring safety came from a gent I met at the track.  Was helping him fix a throttle linkage, and picking his brain on his nitrous install (CBR1100XX, +10" arm, motor had good pistons and headwork, spraying 100hp with a progressive controller... quite quick!).  He said one of the classic cheap tricks to use is to not use the typical cold plugs;  rather than the piston melting, the ground strap burns away and that cylinder drops.  Plugs are cheap to replace and it's an easy repair in the pits.

The good thing about nitrous is that you don't have to run it lean to make power.  Just use a bigger shot with more/excess fuel and keep things safe.  Ryan Schnitz (Schnitz Racing) say to tune nitrous to an 11.8 to 1 AF ration on turbo and supercharged engines, and 11.6 to 1 on normally aspirated. 
That is a lot richer than the 13.2 to 1 that most dynojet operators tune to. Nobody seems to be able to agree on thermocouple temps.  I have run 1400-1450 degrees F for extended periods on my supercharged Aprlia without issue. That was with a 12.4 to 1 AF ratio  But go a little leaner and get up to 1525 and stuff starts to melt.

[Flying Scotsman]

 
Anyone running the $1300 watercooled 1250 billet cylinders on ebay 

Item number: 180559467686

This auction is for a new Yamaha XJR1250  water cooled block . This is a CNC machined block for the FJ Yamaha series engine as seen used in Baby Grand Race Cars. The water cooled block kit includes the head gasket and special dowels needed for this block. The steel sleeves have already been installed and bored and honed to the standard 1250 piston size. We have several different piston kits available for this cylinder block and can be purchased from us as well. We also have the piston kits available in different compression ratios as well. Please note that the crankcases will have to be modified for 1250cc clearance (if installed on a FJ1100/1200 series block). Andrews Motorsports can perform that service for you if needed. 


Please email me at curt@andrewsmotorsports.com if you have any questions!