I've got an 88GXL with a RB "True" dual system. Looking to throw a 125 shot on it. I also have a MegaSquirt I v3 ready to go next monday. Just wondering what exactly the TB mod is, i hear about it everywhere, but with porting pictures speak more than words.. Port matching the L/M/U Manifolds is cake, I've got a spare set, and throttle body. Now if I go direct port to the middle manifold, is this a good idea or bad idea. Should I be using the MegaSquirt to handle the fuel side of this or go wet. Will my stock S4 trans hold to this if I don't launch with the jets active?

Hell I dont think your engine will hold up.

And youre the expert, despite what the experienced users posting in the FAQ have to say?

You mean to tell me you think a stock rotary engine will hold up to 125 shot of nitrous? Even on a wet shot I dont think it will.

What experience do you have otherwise? What makes you an expert on the topic? So far all you have is an assumption, and not exactly a researched or well thought out one at that.

I was gonna say to go dry with the megasquirt with that high a shot. But since your going direct port, go wet system. Id recommend you install them in the lim because that part of the manifold is the "wet" part. Meaning it is designed to flow air/fuel and doesnt have any dead spots where fuel/n20 can accumulate and cause an explosion back through the intake.



You also need to bring your timing back, but im sure you already knew that.

its definitely possible. Id say to follow ronin's advice. Use the LIM to do your direct port, and obviously start small and work your way up to the 125.



almost everyone in PR runs crazy N/A w/ NOS setups, might look for some of them on the forums.



kevin.

Oh I forgot, Im a dumb kid that was born yesterday.





If it last congats.

I would never recommend a dry shot above 50 hp on a rotary. The MS doesnt have any effect on the dry nitrous kits. Dry kits raise the fuel pressure when spraying to add the extra fuel. Wet kit, direct port would be the ideal way to go, but a single fogger in the TB elbow will work adequately as well.

I just dont really see it holding up, yeah it will probably work for awhile, but long term, I just cant see it.

Why not? Be specific, what do you think wont hold up and why? Youre not exactly helping your case by not providing anything more than an assumption.

Adam- How long do you think the N/A tranny would hold up for? Or even the rear end differential? I always forget how much hp they can handle exactly!!



I think N20 is awesome, but you have to have other supporting modifications done to the car as well. Can't just slap a kit on and go to the strip.



Might want to upgrade flywheel also? I am not sure of the specs that the stock components of an FC can handle.

he'd have to be roping and stomping on it everyday to do some major damage to the motor. The rotary has its downfalls but its not glass. I've been told that the fc tranny and rear end are pretty damn strong. They could have been wrong.

Flywheel isnt something that has a problem with hp.



The n/a rear end isnt that weak. Probably wouldnt be a short term issue unless he did a lot of drag racing with sticky tires(DOT or slicks).



Transmission, well, is very dependent on the driver. Be nice when on the bottle(not slamming gears or dropping the clutch) and it will be fine. Ive broken enough trannies to know 2 things. Mazda transmissions dont like high rpm, and the n/a trannies can take abuse or power, but not both.

The TII tranny and rear end is super strong, but I don't think the NA fc trannies are very good at yielding alot of power, or even alot of abuse.

the biggest thing to rememebr is not to blow the welds on the intake.

And do be sure your floor plate is securely attached. You wouldnt want it to fall off when running from the cops.

This is where i disagree...



Dry kits are made for people wanting to run a big shot and have engines with manifolds that are designed only to flow air "dry manifold". Meaning the injectors are at or near the engine and no fuel actually goes through the manifold. (unlike a carbed manifold) You need to add your own fuel with a dry n20 kit. Like with an EMS or the MS whatever.



Dry manifolds have dead spots and places where n20/fuel can accumulate, cause issues, and even have a backfire through the manifold that can blow it appart. Running a TB nozzle with a high shot is not very safe on most modern cars

Only use a wet kit. 100 extra horsepower on a dry kit will require a LOT of extra fuel pressure when the nitrous comes on. This puts a strain on the fuel pump. Only use two nozzles, easier than plumbing 4. 100 shot should be ok, but its always smart to start small (like a 50 shot) and slowly work up to the 100 or 125 to sort out any problems that might come along the way. Use race gas (which means not cat), and find a way to retard the timing. Run 20 degrees total lead (tested with the engine revving up) on a 100 shot. 10 degree split. You will also need to run a race plug. I run NGK 10.5 heat range. On a big shot, you will want a 11.5 heat range. I dont see why the stock tranny wont live on a 100 shot. You'll need a clutch though. Put slicks on the back, bounce the car off the limiter, step off the clutch and bang the nitrous. It should leave hard, and any weak parts will end up lying on the ground, so you'll know right away what you need to replace next. Ha ha, just joking.

at the 170rwhp we have the following problems with the na drvetrain.



1. 3rd gear synchro goes first

2. the gear oil in the rear end wears out/gets burnt really fast



this is roadracing for up to 3 hours a session. little bit more power shouldnt affect much....

Okay after doing some searching I am revising what I was thinking.



I belive it probably would hold up to a 125 or maybe evne a 150 shot. I wasnt thinking about it to clearly, I forgot volume has a big impact on nitrous, and a rotary will act like a v-6 or maybe even a small v8 with nitrous. I am curious to see if this will actually be the case and the "engine" will hold. The drivetrain, yes it will go sooner or later, thats alot of extra stress for the na drivetrain.



I would like to see some dyno results if anyone can find some on a rotary with nitrous, I am curious to see how much tq one can make on a 100 shot.

I amazed can even use the internet because you obviously dont know your a$$ from a hole in the ground.

Wow, someone took their bitch pill, thanks for the input.

Find some PR guys dyno's, seriously they all run crazy N/A setups with huge shots of nitrous. it's like their thing to do. goopy told me of some sick setups.



kevin.

I was talking to the guy I work for, I can get a NX wet efi kit for pretty damn cheap, and hell I get nitrous cheaper than dog ****.

Thats all you see (and hear) at the Import Wars in NH. Bridged, carbed, high rpm, and a whole lotta n2o. And of course the occasional trailer queen RX3 with a 4-link. You see PR guys running 11s with engines they built in their basements.



Makes me wish I had a Puerto Rican grand father or uncle with decades of rotary experience. That way I wouldnt need to **** up as much to learn.

Yes, dry manifolds have spots where nitrous cam accumulate causing it to backfire through the engine. But a good wet kit will still flow perfectly fine through a "dry" manifold provided the shot size isnt too high(and I dont consider 125 on a n/a too high) and you adhere to a minimum rpm limit when spraying. I bet you could make a 50 shot backfire through the intake if you tried to spray at 1k rpm. The risk of backfiring through the intake is much lower than the risk of leaning out with a dry kit on a rotary with a thought-out nitrous system, and a reasonable shot.



I still would not recommend a dry nitrous kit on a rotary, because there isnt a lot of working room with the stock fuel system, and I simply dont see the pros of a dry system coming even close to outweighing the cons.



Worst case scenerio? Whats cheaper to replace, an intake manifold or an engine?

i know its a different car, but on the rx8 the intake is more than the engine, or the intakes are more than the engine.

owned.



kevin.

Stock system bieng key words. Hes gonna be running the MS. If he got it dyno tuned with a dry kit it would be a good system with actual fuel injectors doing the fueling instead of a series of holes drilled in a pipe like i and many others foolishly depend on.



And if you think about it, What engine can really sustain running lean with N20 that would make it OK to run a dry kit? None. You need to compensate however you see fit.



Problem is a blast like that doesnt only kill the manifold. It usually takes your engine and hood with it. Ive seen a exhaust backfire turn a flowmaster into a pillow looking ball of steel.

Who cares what you think?

No one asked what you think.

They asked what you know.

Which, apparently, is nothing on the subject.



So, if you don't know anything on the subject, keep your yap shut.





Dry vs. Wet.



The reason I prefer wet is for several reasons.

Dry shots increase the fuel delivery via an FMU, a fuel management unit. Basically, to get the injectors to pump in more fuel, they jack up the fuel pressure. This would be alright, except that, as fuel pressure rises, fuel flow from the pump decreases. Even with an upgraded pump, this can become an issue on big shots. Throw a fuel pressure gauge on the car with any big hp shot, and watch the fuel pressure skyrocket. Over 100 psi of fuel pressure is not unheard of.



Eep.



This excessive fuel pressure is not at all what we're after. Sure, it adding more fuel, but HOW is it doing this?

Have you ever noticed that the static rail pressure of pretty much every EFI car out there is 35-45 psi? Think there's any reason for this? You know the manifold reference vacuum line? Its job is to maintain this pressure differential.

Below this pressure level, atomization suffers. The fuel just dribbles out like an old man taking a piss. Above this pressure level, atomizaton suffers. Fuel just winds up spraying directly onto the opposing runner wall. The overall combustion is less efficient from the poorly atomized fuel at this high fuel pressure, and the runner walls are literally getting soaked in fuel... this presents a LARGE problem of nitrous backfire.



Eep again.



Laslty, our cars have very high charge velocity travelling through the runners, and with our rotors constantly drawing an air charge (as opposed to a 4-stroke engine's intake valve remianing closed for 3/4 of the crankshaft rotation), we are much less like to see fuel puddling at our valves. And with our VERY long intake runners, we can give the fuel plenty of time to atomize, and completely avoid corners. Most piston engines HAVE to put the foggers right next to their intake valves.

With our such gradual runner corners and our very long intake runners, fuel puddiling is not an isue at all. Nitrous backfire is a non-issue with properly placed foggers.

Notice I said properly placed. All large shots should have the foggers mounted AFTER the TB. The TB, especially in stock form, does tend to collect some fuel, especially with the sharp turn at the throttle body elbow all of the stock systems present.



To sum it all up: Dry shots suck b/c they lower the pumping volume, which can cause you to run lean, and they cause excessive fuel pressures which lead to fuel puddling. Wet nitrous, when properly placed, offers much better atomization and power gains, with minimal risk.

Not defending the FMU by any means.

But can you clarify this a little better To me it sounds like your saying the pumping volume is related to running lean in this situation.



And these two statements sound like a contradiction;



To me it sounds like everyone who has run into problems with a dry kit has no fuel mods other than an FMU and a pump. Pulse rate is still at a max of around 60% (+ -) at full duty, and your not effectively adding fuel where it needs it most with this method.

I agree, they do, don't they?

Let me clarify.

When running an FMU, with the higher rail pressures, atomization suffers because the fuel injectors, which face 90 degrees against the air flow through the runner, physically force the fuel to be sprayed onto the opposing runner wall. This is what I meant about FMU's.



The other statement about our high charge velocity was meant to be a comparison to 4 stroke engine's, not to the rotary itself.

Wet systems are known to cause nitrous backfire in piston engines. With our higher air charge velocity, this is never an issue with properly placed foggers.



Make sense now?

One was a descriptive of our fuel systems, the other was a comparison to short-runnered piston engines.





I agree, to a point.

Zex kits are the most common dry kits, mostly due to the simplicity of their install. THIS is what causes so many problems. If you made a bolt-on turbo kit for an FC that only included the turbocharger and adapters to fit the AFM, exhaust, and turbo outlet to the TB, hundreds of people would blow their engines.

Heck... look at FCD's. How many engine's have those killed?

When you install a product, you should always know how it works, and to ensure it is working properly. Dry kits are so simple to install that it requires no understanding of how nitrous works, and without ensuring the system is operating safely, many problems follow.



Ignorance is the #1 cause of all car problems.



Here's the flip side of my point:

Dry nitrous kits work great for 50-75 hp shots of nitrous. Big power shots... the fuel spraying onto the opposing runner walls becomes too much of a problem.

I always reccommend wet. No problems, period.

https://www.nopistons.com/forums/pub...1047683561.gif Still not adding up, Ok, lets say the pump is cavatating but supplying 100 psi. At what point do we get low pressure or volume? When the RPMs go up and consume more fuel reducing the cavatation?



I keep getting double talk, "The fuel cant puddle" "fuel will puddle if..."



Or "Pressures too high!!". then "you cant make enough pressure and run lean"



I guess I will never know why people condemn the system.

Pumping efficiency goes down as pressures go up. A pump which supports 400 hp at 40 psi may not support 400 hp at 100 psi. If we're using a massive pump, that's one thing, but most people are merely dropping in a walbro and calling it a day. At such high rail pressures, the walbro could fall short.

http://216.242.145.16/products/prod_...-1-2-large.jpg

If the engine is basing its fuel calculation at 100 psi, we need 100psi of fuel or we will run lean. If the total volume of injected fuel is higher than the total volume pumped, the rail pressures will drop and the engine will run lean.

All pumps will pump less fuel at higher rail pressures.







We want a ~40 psi pressure differentil all the time between the injectors and the manifold. This is why the pressure drops under engine vacuum, and why it increases under boost. At 10 psi of boost, the rail pressure will increase by 10 psi. This is because the boost in the manifold will also be pushing the fuel back into the fuel rail. At 40 psi of boost, we need 80 psi of fuel pressure to maintain this pressure differential of 40 psi. If we only had 40 psi of rail pressure at 40 psi of boost, the engine would get zero fuel, even with our injectors at 100% duty cycle.

If we jack up the fuel pressure, but don't jack up the opposing force (boost), we end up killing our atomization by spraying all of the fuel onto the opposing runner wall.



We want to avoid excessively high rail pressures.

1. Its hurts fuel atomization and promotes puddling in any engine.

2. It decreases the flow volume of our fuel pump.





When I am saying the fuel can't puddle, you have to realize I am talking about completely different scenarios.



If we jacked up the fuel pressure and ran a wet system, we'd still have fuel puddling issues. What I am saying is that:

On rotaries, with properly placed wet foggers nozzles, and standard fuel pressures, fuel puddling will not occur due to our very high air velocity. This a comparison to 4-stroke engines, where using a wet shot can cause fuel puddling at standard rail pressures.

Our very high air charge velocity can NOT overcome the puddling problems caused by excessive rail pressures.



The entire problem is the excessive rail pressures. Avoid them!



I condemn the system b/c I have seen the failures it has caused on these cars, and witnessed several tests demonstrating what happens to the air/fuel mixture as the fuel pressure differential increases.

s4 or s5 block? stock s4/s5 block can take 300hp no problem, it's been done zilion times with PP setup running alcohol.

With this chart your supplying, and the generally reguarded 0.5lbs/hr of fuel per horse power @100 psi you should have no problem supplying fuel to a rotary with most anything done to it. Do the math , I think you will be surprised..I think you should be condemning the FMU like I have many years ago. There has got to be better ways than to jack up pressures to fuel the system..

how much of that s4/s5 block do you think is stock?

I have always hated FMU's (and RRFPR's). This is nothing new.

We're on the same page when it comes to FMU's.