shinjuku

And your point is......?

bill Shurvinton

Old ones are often the best.

Dunno why you think chamber wall cooling should be any different with water to petrol. If you are running proper water injection then you will still have atomised droplets in the chamber which vapourise during the compression stroke, reducing the pumping loss in compression and helping cool everything.

My theories and Pete's vary on whether uni-stage or dual stage is better, but he has an awful lot more miles on real WI setups than I have, so on empirical grounds he is right.

Me I still prefer a light misting pre-turbo to up the compressor efficiency and a second stage into the rotors to provide the anti-knock.

YMMV of course.

shinjuku

Hey Bill,

I had pictured that the WI system would have completely vapourised the mixture by the time it enters the CC but I suppose if you were injecting enough water (ie beyond the saturation point) then there would be droplets that would reach the CC and, as you say perform that liquid to surface cooling effect that the petrol did, only probably better.

That would mean injecting a lot of water though. LOL

rotarygod

iTrader: (1)

You dig up an old post and someone wonders why. If you start a new one someone just calls you a noob and tells you to do a search. Just can't win around here apparently.

bill Shurvinton

Not that much water. And if you inject post turbo it will not have had much chance to atomise before injestion.

shinjuku

Well if that's the aim, ie providing liquid in-cyclinder cooling and liquid to be vapourised during the compression stroke for less thermal input work, then injecting just in front of the T/b would probably be the best pratical option then?

RETed

It shows how ignorant you are.
There were points that hinted a wide-band is not something to totally rely on, yet it's the basis of your reply.
So that makes you look even more stupid...


-Ted

bill Shurvinton

Well really it makes you look arrogant and condescending. Especially as the comment was related to the fact that piston AFR and rotary AFR are not always comparable. The wideband is still one of the most valuable tools for the tuner.

You have not added to the discussion and have just tried to drive away someone who has questions and wants to learn. Are you normally this much of berk?

shinjuku

Well Ted I must thank you for being extremely gracious in taking a moment from your life in order to communicate with such an ignorant fool as myself.

Now, given my extreme ignorance, perhaps you might like to explain what my original question had to do with wideband AFR meters? This is assuming you are able to again communicate with someone so ignorant

RETed

The answers are all on here.
You need to do a search for them to find them.

The wide-band has been proven to be inaccurate.
AFR's can fluctuate as much as 0.3 points (or MORE) - that's a LOT considering if you're going to tune to the ragged edge.
Water injection is all about tuning to the ragged edge.
If you're ******* with water injection and not going to the ragged edge, I dunno what to tell you...



-Ted

RETed

I'll just repost one of your replies...

So tell me, how do you know it's "overly rich AFR's"?


-Ted

shinjuku

My post was about determining the reasoning behind tuning using richer mixtures than what is required for maximum power. That is richer mixtures that will likely lose power and consume more fuel, but done in the interests of engine life ie avoiding pinging and thermal meltdown etc. I wanted to try to find out HOW exactly the richer mixtures will increase engine life in a highly stressed force induction engine.

It was not about AF meters as such and their accuracy etc.

As you asked you would surely know that the AFR can be determined via many means including, but not limited to o2 sensors. Either way I wasn't talking about a specific case where I KNOW the mixtures to be rich just generally about the rich tuning philosphy.

If you have something to add to the discussion great say it. I want people to comment as I want to learn more, which is why I dragged up the old post after searching rather than creating a new post.

But if you simply wish to diss me, not that I understand why you would bother to, then maybe PM might be better for the sake of not boring the hell out of others?

bill Shurvinton

And you have the gall to call others igorant. Even someone with a very basic knowledge of the otto cycle realise that AFRs Vary. They vary within a cycle for goodness sake. Tuning to the ragged edge requires a knowledge of this and how to handle it.

So I don't believe that a well designed wideband is innacurate. It gives a very accurate snapshot of the exhaust gas as it passes the sensor. Cheap ones may lack consistency but the good ones are within 0.1AFR.

But ragged edge was not what shunjuku was asking about. He was, quite rightly, asking why you run significantly richer than the text book 13:1 ratio at which all the oxygen is consumed. This is a perfectly valid question for someone who is new to the theory and practise of engine tuning. As such the more experienced members of the forum should surely step to the plate and help them learn, rather than play the local bully boy, or worse technical eliteist.

I don't know why you bother, and wish you wouldn't

RETed

Think about it...

There is nothing mysterious about forced induction.
What happens when you raise compression ratios and intake air temps?
What's happens when you raise piston engine compression ratios up to 15:1? 20:1?
Then add more heat to the intake charge?
This is basically what you're doing with a turbocharger or a supercharger.

This should explain why you run richer...


-Ted

shinjuku

See that's just it....I've known for a long time that with FI applications that richer than n/a mixtures are used around 11s for rotaries and this is to stop pinging and thermal overload of components. But I wanna dig deeper into it.

What I'm interested in finding out more is exactly HOW and WHY this helps. Not just simply that it DOES help due to the excess heat, cos everyone knows that.

My understanding is that it does it via several mechanisms:

1) The vapourisation of some of the excess fuel cools the intake charge - fairly straight forward.

2) Some of the excess fuel is still raw liquid during the induction, compression and even part of the power stroke, maybe even beyond in some applications ??, hence there is liquid to CC surface cooling.

3) The richer mixture also alters the way the flame front travels. This I don't properly understand as I have read in some places that slowing down the flame front can cause pinging as end gas pockets have more chance to ignite independantly.
Where as elsewhere I have read that slowing down the flame front reduces pinging.

Also which of these three is the most important? I'm guessing points two and three.

RETed

Why does it matter?
Seriously?

The only thing you can do is manipulate flame front (i.e. octane).
How do you control the other variables you mention?
Without modifying the rotor or the rotor housing, this is next to impossible.

So this ends up being an exercise in theoretical guessing?


-Ted

APEXL8T

It seems to keep comming around to the actual thermal dynamic effeciency of the rotary vs the piston.Swept gases as opposed to cylinder head chamber.

APEXL8T

i do have a ignorant question: Which sensor reflects the oxygen/carbon readings from fuel.(which water can impose a higher content value)
So when tunning with the trimix for injection cooling how does this reflect in your tuning the A/F? (I dont know)Does this add another issue in obtaining proper A/F and timing?

shinjuku

Well I'm asking anyone for input as I want to learn more but I can think of these for each points I raised:

1) the intake charge cooling can be altered with WI and other means
2) liquid to CC surface cooling can occur with richer AFRs and WI
3) Flame front - like you said RTed, octane but also richer/leaner mixtures, different fuels, WI etc.

RETed

You're supposed to lean out the AFR when doing WI.
This is why it's scary if the WI does malfunction or runs out of water - almost instant engine death from lean AFR's.
Most popular are wide-bands for reading AFR's.


-Ted

bill Shurvinton

Yeah right, and running out of fuel doesn't do the same. Or maybe the fuel pump failing (it happened with a car I know on the dyno last year at around 400HP). At least you can build a totally passive WI system. Not hard to fit an engine cut on loss of water if you have a half decent ECU.

As for fuel: Don't forget that the vast majority of higher octance commercial fuels have a faster burn rate than lower octane. Boost also increases burn rate. But hey, that's what we have spark retard for. But as long as you can prevent detonation ( which water does very well by cooling the combustion chamber, cleaning the combustion chamber to reduce the chance of hotspots, slowing initial burn AND increasing knock resistance). All of this proven 70 or more years ago by the internal combustion pioneers.

Its not new and its not scary if done properly; just good engineering, with the only downside being 2 tanks to fill not 1. Fine by me if its not for you, but others want to understand.

RETed

There are different ways to attack the execution.

Hugh McInnes describes in "Turbocharging" to reduce the fuel as WI is used.
This is supposed to give best power.

I know many use WI as just an "add on" on top of the regular fuel map.

Personally, I try to keep within the safe parameters of whatever octane you're running.
Try to run the biggest IC core you can get your hands on and properly duct it.
There is no reason to be tuning to the ragged edge on a street vehicle.
I run at least a (narrow band) AFR gauge and an EGT gauge - this will catch most (lean) problem that do pop-up short of a catastrophic failure (i.e. instant fuel pump death).
There is not much you can do when you do run into a catastrophic failure.



-Ted

RICE RACING

I'm not sure on this but I'd say I have a bit of experience on high HP pump fueled rotoray engiens running everyday cheap gasoline and water injection.

I'd like to share these experiences with you !

I have made the same power on 9.8:1 AFR with WI as I have @ 13.9:1 AFR (strong spark obviously) I dont alter spark timing to suit WI, I dont alter AFR to suit specificaly WI, infact the ONLY and I mean ONLY thing I do to suit WI is run about 10 psi more boost !, infact I have not reached a limit "yet" where I have gone thats it WI will not *patch up* any more power........ You just feed it more and more water and more boost pressure and watch the numbers go up and up ! Bit like Dr Harry Ricardo did 70 years ago, simply made more power than the dyno could handle without reaching the limits, well that same thing happens in the year 2000

WI is a science and it can be applied in its extreme, what you need is experience with it and not change anything about your tuning philosophy to directly suit it as such. I can show you dyno graphs of a car heavily loaded with WI (30% to fuel ratio) in the mid range and the diff in power with WI v's no WI at the same boost is minimal less than 3%............ You can simply load the c8nt up and adjust your boost to suit or push the f8ck out of your system to make mega power at lean ratio's if you so wish too as well.

You do need copious amounts of water (single Aquamist jet systems are not enough!) but its all pretty easy and its been done by much much smarter people many many moons ago.

If your worried aobut it failing you need to purchase a fail proof system like I build and sell, no bells and whistles just proven reliability and results and understanding of what it takes to get the most of WI. Like has been mentioned all you need to remember is to fill up the tank, for some people this can be a challenge I suppose?

bill Shurvinton

Sir Harry please Peter ;-)