I did a search, and it really didn't come up with anything-- But I am building a b18c motor to take a big healthy shot of n2o-- i was wondering what compression pistons you guys would get?? i was thinking keeping stock c.r.-- Any ideas ?

 

You're better off if you go with lower compression pistons. Maybe SRP or something similar.

 

Actually, nitrious loves higher compression. It's just a bit harder to tune with a higher compression. Forged pistons are the way to go.

 

high compression forged pistons, (I used to run 12.5:1 on pump gas but would only spray with atleast a c12/ 94 mix, do not lower your compression as the motor will only be on juice 2% of the time if its street driven) anyway, billet rods, arp studs, stainless steel valves on the exhaust side, some type of spark retard to come online with the juice and NGK BKR7e-11 PLUGS.

 

yeah, thats what i was wondering-- everyone tells me different about hte CR of forged pistons for nitrous... if i was going higher... i'd do a 10.6:1 --- skunk2 valve train. And how much spray would you guys think-- I've got a direct port NX system to work with here so she can go alll the way up

 

Dude, sleeve it to like 84mm, do what builthatch says and 200 shot DP. I was this close to doing that. Might want to invest in a block girdle and a progressive controller for the shot.
I think it would scream..........Evil, just evil

 

Any other input??? what you would do...how big of a shot...blah blah blah.

 

I'm actually in the middle of doing this.

You may want to look into the Importbuilders' nitrided valve set. I think I paid $250 + shipping for the set of 16 intake and exhaust valves, black nitride coated. Nitride or stainless steel valves give you a little bit more room for error before you burn a valve into oblivion compared to stock valves. Oversize valves might help a little bit, but I couldn't afford the kind of headwork needed to really take advantage of them.

Also, you are a fool to not replace the valvesprings. Importbuilders sell their kit of dbl springs + Ti retainers for $375 I think. I've been happy so far. I think you could use ITR dbl springs (intake) and retainers if you wanted to save a lil money - I didn't bother with this option.

Cams are another touchy subject. Like a turbo motor, you will want to avoid any cams that have a large amount of overlap. I've been told by several reputable people that having too much overlap can cause a lot of problems, although curiously none were able to answer me "Why?" very well. I wouldn't throw anything larger than a CTR/Sk2 stage 1 in there to start with, at least until other tuning was accomplished. I personally will be using CTRs with a JUN3/Sk2stage 3 upgrade in mind.

I've seen many ppl (granted, they were IDIOTS) spray a 100shot on a stock-bottom end LS/Vtec with a fogger kit. I'm planning on starting around 75 and hopefully working up to around 200HP (direct port)

MAKE SURE YOU HAVE ENOUGH FUEL. A walbro 190/255lph pump might be a wise investment. I have the 255lph. Nothing will kill a nitrous motor faster than running lean!

If you are going to go any bigger than a 75 shot, you should investigate highly a direct port fogger kit. I think NOS make a kit that is designed as a direct port kit for hondas. I bought a NOS Pro Fogger kit for a V8 and am splitting it with a friend - we each use 1/2 of the kit.

Be careful about how you tap the manifold - we had to get special foggers so the jet of the fogger could be aimed directly at the valve (ITR manifold - flat runners) by drilling a hole to tap the manifold at an angle almost parallel to the runner. This was very, very, very tricky. You need to worry about nitrous pooling during shifts if you run a direct port kit, but far less than a standard wet kit placing nitrous in the throttlebody or intake. Another big advantage of a fogger system is that you have the OPTION of running 2 fuel systems: one for injectors, one for foggers. The advantage of this is that you can feed you engine pump gas/race gas and still have the option of feeding your foggers methanol, ethanol, turbo blue, super race gas or just about anything and not breaking the bank filling up the tank with super expensive gasoline. I'm running either methanol or 119+ race gas(depends on how expensive alcohol-friendly pumps are) to the foggers and 93 pump gas to the engine. Gotta keep it streetable

If you are jetting any bigger than a 125-150HP shot, a progressive nitrous controller is not really an option. The shock of 150HP+ of nitrous hitting your engine will not be pretty in any shape or form. Progressive controllers gradually increase the amount of nitrous delievered by rapidly opening/closing the nitrous solenoids like they were injectors.

As for the bottom end, you *need* strong rods and rodbolts. I'd go with eagles personally because although crower certainly make a lighter rod, they are not anywhere near as strong as eagles. Numerous ppl on honda tech have been offering very appealing group buy prices. Rocket @ hondasaver offered some VERY appealing prices on a set of custom (longer) Eagle rods. Using a non-standard rod takes some thought/design, but it can really help lower your R/S ratio to a more sane level. (I'm shooting for a 1.63 R/S - better that GSR/ITR, worse than B16)

Forged pistons are definately a MUST too if you're going bigger than a 100hp shot. I'd recommend highly that you talk to Rocket @ hondasaver. He can lay his paws on custom Ross pistons designed for forced induction with super-large ring lands and ACL rings for a very reasonable price. Although designed more for turbocharged apps, the design he has will work well with a larger dome to raise compression. I am personally getting 11.8:1 compression 84.5mm pistons, but I am also a little crazy. 12:1 is probably the upper edge of what you are going to be able to tune. Remember to get pistons that have large enough ring lands for vtec/oversize valves(if you elect to go that route) and whichever cam you are using. Anything bigger than a CTR should probably get clayed.

You might as well plan on either Golden eagle sleeves or a Dart block ($2000 - http://www.dartheads.com/blhonda.htm I think) if you are gonna bang any more that 100/125 for any period of time. I have a dart block on order. ETA 5-7 weeeks

DON'T FORGET BEARINGS! Your bearings will endure torture while you are spraying. You may want to aim for a little bit on the loose side of tolerances to allow for a little extra room for lubrication.

I wouldn't plan on revving the thing like it is a B16. With nitrous, you will have a HUGE powerband and should not need to consistently rev the engine as high as a naturally aspirated setup. I am going to try to keep revs under 9000 RPM when spraying, regardless of which rods, pistons, crank, valvetrain you use. The forces at 9000RPM are more than double that at 6000 RPM. Remember that internal stress on the engine increases by the SQUARE of RPM... I.e. dbl rpm = 4x internal forces.

Last but not least, a MSD digital 6 or other ignition amplification system paired with a colder plug will be a MUST. You MUST retard timing while spraying or you will blow **** up. The added spark strength that aftermarket ignitions provide will only help here.

My car is still coming together so I may be totally wrong about some of these points - I guess we'll see next season when the beast makes it's debut in full racing form. This information was gathered from a mixture of online sources, books from the library, talking with ppl who build honda motors and ppl who build ford V8s for serious nitrous - 200+HP shots. Define your goals clearly at the beginning - it will make the whole process a LOT easier.

good luck!

peace
-Dave

 

Don't forget that you will need a stronger clutch because your stock one(if still stock)will slip.

 

ttt

 

Well the basis behind the argument of overlap+boost = No good is basically that the boost pressure will be lost due to the overlap with bigger cams with longer duration.

Cam gear tuning can cure this easilly but you will lose power in N/A form but you can still have the large lift of the big cams.

I'm not into boost anymore and I'm going all motor/nitrous. I'm going to be seeing if the same thing holds true with Nitous + overlap = No good either.

Here's my theory on Nitrous + overlap:

I don't think cylinder pressure (before the spark plug fires) is much higher than in N/A form, since the n2o must be ignited before it will release it's oxygen. So the n2o should remain somewhat inert(along with the oxygen already present) before the cylinder fires and so I don't think that the overlap would be a problem. Since by the time the cylinder fires all the valves should (better) be closed. So I think spraying with a large amount of overlap shouldn't be a huge problem on a Nitrous engine. Because the n2o isn't escaping anymore than the air/fuel your bringing in in N/A form, and you get that little power lost by the escaping of the unburned fuel charge with the 'supercharing' effect of the leaving exhaust gasses.

This is the opposite than with a FI engine. Where cylinder pressure is sky rocketing before all the valves are closed and thus you're losing pressure before the exhaust valves close.

Any thoughts?

 

nitrous motors, the mixture expands alot quicker when fired due to higher O2 content.

blundar knows the ideas, but yet to run juice.

nos motors like alot of exhaust cam duration to evac the cylinders.

 

Everything blundar said, and I say use a VTEC block, since it has oil squirters, forged pistons or not, nitrous motors run hotter than any other. I reccommend to build a stock spec B18C1 bottom end for nitrous use but with rollerwaves, valves, springs, rods, and sleeves if your gonna run serious nitrous, 150 shot or more.

The valve coating is a good idea.

Use a good oil, the hotter the engine burns, the better oil you need.

Redline or NEO are some real synthetics worth a try, you can get info in the type-r forum thread. Although the Mobil 1 is fine for the street if you are consistant with drain intervals.

Buy an EGT guage

You can set up an AEM on this system, an I bet you could have a damn powerful motor.

As far as heat buildup goes, keep this in mind, you might want to set your pistons compression a little lower than what you desire in the motor, and compensate with a thinner head gasket. Thinner head gaskets are harder to heat up.