Honda Rebel 250 & 450 Forum banner

If I were dumb enough ... nitrous oxide?

5K views 21 replies 7 participants last post by  7milesout 
#1 ·
I'm not saying I'm gonna add nitrous. But I am saying I'm dumb enough. How much of a power boost would be safe on a stock engine Rebel?

With only 18 flywheel horsepower at most, I'm thinking +40% would be the max. And even at that, I would be concerned with blowing it up. However, since I can watch the AFRs, I believe I could keep the combustion safe.

40% is approximately 7 horsepower. I tend to believe the mechanical components of this engine could handle that. Imagine a Rebel with 20 - 25 hp versus 13 - 18 hp. I'm just dreaming here. I think it would be inconvenient to attach a bottle that keeps running out. And why would anyone ever need such nitrous power? Beating a Prius to the next traffic light? Almost keeping up with a Harley? The occasional roll down a quarter mile dragstrip?

I started designing a nitrous plate that would distribute nitrous nicely down the intake. So an opening in the intake casting wouldn't need to be drilled and this plate would be a simple install.. But I might as well quit wasting my time. I don't believe there'd be any real use for it.


7milesout
 
See less See more
#2 ·
But it would be so much fun!


My absolute favourite 250 is the Suzuki GT, developed 27HP, 2-stroke, 6 gears.


It was my dad's bike, wasn't legal for me to ride it, but I used to cruise around when he was at work, after I got home from school.
 
#3 ·
If you want power from a 250, try finding an Aprilia RS250 (mid-90's to early aughts). It was a two stroke 90º V-twin that produced 60HP to the ground. Yes, you read that right: 60HP...almost as much as an SV650.
 
  • Like
Reactions: deere245
#7 ·
Yeah I've checked that turbo out already. I can get one for $249. Its a much better option because as much as I'm on the throttle stop I'd probably blow through a bottle every day. A turbo would be, the gift that keeps on giving.

I've checked out the capacity and boost maps of that turbo compared to the capability of the Rebel's engine. That turbo can crank out roughly twice what would be required by our 233.8 cc engine. Which if I understand the boost curves correctly would put that turbo right in its high efficiency zone when paired with our engine. Meaning it should work well for our engine. The problem is the plumbing, and maybe moreso the plumbing of oil to / from the turbo.

I'm considering this design though. Probably just a pipe dream though. I would love to put together a "kit." The mechanical design engineer in me.


7milesout
 
#8 ·
Plumbing of rubber hose from carb and to head is relatively simple.
Oil would be the challenge.


Oh that reminds me the FJ180v Kawasaki on my mower is full pressure lubrication with a spin on filter.
Adding this turbo would be easy on it.......
 
#9 ·
If I had a small enough bottle I would blow some nitrous through my rebel. I would be the first to try it.


Only problem is momentarily dumping enough fuel to enrich the mixture during the nitrous blast.


The engine could easily handle 40% more power. I think the failures would begin occur in the clutch, gearbox, or output shaft. There would also be the possibility of valve float in the higher rpms.


If the clutch didn't slip first I would expect gear or bearing failures in the gear box.
 
#10 · (Edited)
In all my years on various Rebel boards (since Y2K) I have yet to see a single success story involving a turbo. Many have tried, so far only one "finished" and it didn't pan out well (that one is documented somewhere on this board). With that solitary event being the closest thing to a success story, I'd bet on the N2O to fare better.
 
#12 ·
Possibly, it's been a while and I only recall the report stating it didn't produce anything effective. Removing it after three days would certainly support that premise. ;)
 
#13 ·
Would like to change the subject now to "turbo" instead of "nitrous." I'm an engineer. I'm a former automotive engineer. And I'm a vendor on an automotive forum. I like to invent stuff. I like to invent stuff that is non-crappy. Then I enjoy to sell said non-crappy stuff. Not for the $, much more for the, "oh wow, great product" feedback.

So I've been considering making a project out of this cute little turbo, because the turbo alone is fairly inexpensive. I've started doing things that cost me nothing, just looking for a reason to make a turbo kit not feasible. I've roughed out a bill of materials, roughedout sketches, looked for availability of supporting hardware and systems. But today, I might have run into my first real mechanical issue.

First a some reasons why a turbo kit would not sell.

1. Too expensive: With all the supporting accoutrements, I can imagine the kit costing what the bike is worth. Yet not many people ride a Rebel as cheap day-to-day transportation. Most ride it for the fun and joy. Like those who would spend money on bobbing a Rebel, perhaps they would buy a turbo kit.

2. Not effective: I would never buy any mod if it didn't serve a purpose, and serve it well.
Said turbo kit would have to be worth every penny, or I wouldn't buy it ... or develop it.

3. Too complex to install. A shadetree mechanic should be able to do it rather easily.

4. I personally don't want to turn my Rebel into something it is not. It's not a drag bike. And personally I would still want the Rebel to look as much like a stock Rebel as is possible.

I think most of that I could overcome. But here's the mechanical problem I thought into today. Let's say I make this kit and put it on The Piglet. From what I can tell about turbo maps, that turbo should work well on our engines. But what if I'm at maximum boost and I slam off the throttle? With a CV carb... If I push boost into a CV carb, is the slide going to respond well / appropriately? The slide works on pressure differences. Will the slide come down quickly like it does now? Or would there be engine speed decelleration lag? Might this lead to driveability issues? We have a throttle plate / butterfly valve on this CV carb, so maybe it would work just fine ... dunno.

But since this line of thinking, I believe there would need to be a blow-off valve.

Any thoughts on that? And how much money starts to become more than you would spend, even if (let's assume) the kit was VERY effective?


7milesout
 
  • Like
Reactions: Cobra2
#14 ·
I would draw through the carb. Not push through it.
Higher boost might require a larger carb. (dual carbs maybe?)

Lower boost maybe just re jetting.

Figure rubber hose to plumb it. First generation would be simple in this aspect as the carb already floats on rubber hose.
Parts to convert to "floating" carb are easily available on Ebay.

Cost usually works out to horsepower per dollar basis.

What is stock horsepower?

What horsepower can be achieved "reliably" with a turbo?

Can always be "stages" of the turbo kit.
Level 1 = mild for x dollars
Level 2 = more adventurous for xx dollars
Level 3 = too dumb to know better for xxx dollars
 
#15 ·
I prefer to keep my Rebel stock I would buy more cubic inches and another bike before going that route.

This thread reminds me of a buddy who bought a modded Mustang Cobra. We all warned him not to go near it. It's still in his garage 10 years later not running.

I do understand the need to hack. Good luck to all!!!
 
#16 ·
Deere - I think locating the turbo there would be a problem. The amount of vacuum beteen the carb and the turbo when slamming off the throttle from full boost might damage the vacuum slide / diaphragm and/or related components.
 
#17 ·
pdawg - Your reply is very appreciated. I value it tremendously. Generally your mindset and mine are the same. I believe the difference for me in this case is that I find the Rebel to be a fun and relatively speaking, inexpensive hobby (compared to the Mustang example).

It's so much fun, I like the thoughts of making it even more fun. I consider my chances of being able to develop an effective turbo, very low. Like 10% chance. The chances of me trying something are only slightly higher. If I get to the point I believe the chances are higher of success, I might be willing to spend some money. I'm not there yet. I would not want to make something that turns our Rebels into that Mustang scenario.


7milesout
 
#18 ·
Doesn't have to be set to full boost. Different pop off valves would control that I think.

You could try something less than full boost and slowly crank it up until the carb can't handle it.
Then you would know the limits of the carb and at what stage or level a different carb (non CV I would guess) would be needed.


Putting the thing on and instantly maxxing it out is asking to break stuff.

One step at a time. Put it on and try maybe 25% and see if anything breaks, if not then step it up..etc..
 
#19 ·
The most effective and proven mod to getting more power out of a Rebel is jacking the gas cap up and sliding a Shadow, Magna, or Valkyrie under it. All three are direct bolt on mods.
 
#20 ·
Well, my turbo research (prior to spending any money) has come to a stop. I think I'm just going to let my desire to work a project be, Gone With the Wind.

I have concluded (and maybe some of you have considered this as well), that trying to blow boost through a CV carb is too big of a hurdle. What I have read and researched tells me that boost will tend to push fuel around to where it doesn't need to be in a CV carb, and may prevent the bowl from filling properly. Leading to all kind of running problems.

There are ways around it, but it would be too complex and expensive. I was hoping to develop an effective "kit" that others here could purchase rather inexpensively. But to overcome the issues associated with boosting through a CV carb would add too much complexity and expense. I'd be wasting my time. I don't believe many would care to spend the money. So, I'm letting it go.

However, in the spring I will continue to fine tune this Rebel to the best of my ability with my AFR gauge. Those results will go into the Rebel AFR thread. And I still think it would be fun to have a Rebel Drag Race. And further info will go into the Rebel Racing thread.


7milesout
 
#22 ·
Cobra - Thinking back on this thread, the problem I ran into wasn't a matter of if could it be done. It is a matter of complexity, expense and originality. The CV carb would have to be chucked, and it is a fabulous carb to just chuck away. Even putting together such a kit with great instructions would be challenging. Procuring all the correct hardware to create an effective kit would make the cost of the kit likely more than what most on this forum paid for their Rebel. And end the end, it's likely the Rebel would look more like a plumbing experiment versus an original Rebel. And that bothers me personally.

Nitrous is still very feasible. But it my case, I'd have to tow around a 500 pound bottle, because I'd be blowing through it continuously. The cool thing about the nitrous is, an effective kit could be put together and it could be used like a "dry" kit. Because this carb has the ability to run rich, and the Rebel engine seems to gulp down a rich brew (with no nitrous) like it ain't no thang.

Maybe I should put some more thought into it, but I've been fiddling around on my Burgman as of late. But then again, what's the difference between our, say 18 hp output and a 25 hp output on nitrous? Not all that much, unless I'm racing another Rebel … or trying to beat a SmartForTwo to a parking spot. It will only be cool in as much as it is different, and not a stock Rebel. Not a whole lot of value in that methinks.
 
  • Like
Reactions: CMX250 and Cobra2
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top