Landracing Forum
Tech Information => Technical Discussion => Topic started by: racer x on May 29, 2011, 10:35:43 AM
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I have been having some problems with detonation. Particularly with Nitrous. What would be the best way to combat this.
Higher octane gasoline?
retard the timing some more?
lower the compression?
reshape the combustion chamber? Like deshroud the valves
cooler spark plugs?
Methanol fuel?
my Nitrous mix is very rich.But I can hear some knock in first gear before I even push the button.
I plan to do ALL of the above .But I am curious what is the best or most important thing to look for.
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What's the compression? First thing I would check is timing and consider uping the fuel octane,ie. no cheep fuel from JD's pawn,bait, hardware and 24hr. adult gift shop. :-D
PS JD's is having a sale on shotgun shells
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CH3OH
Bill
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I have run 13.25 to 1 then 12.5 to one I pulled a couple deg of timing and plan to pull more. I run Rocket 111 but will try 118 next time.
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A few thoughts -
250 Kawi, water cooled, right?
Classic troubleshooting approach. Baseline - make sure everything is spot on before you start changing variables or grinding.
Two things you didn't mention -
How is the temp?
Both cylinders knocking? Fuel distribution. Make sure the mixture is right.
If you deshroud the valves and do nothing else, you will loose a bit of compression, and the knock might go away, but you'll never know for sure if it was compression related or combustion chamber related.
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A few thoughts -
250 Kawi, water cooled, right?
Classic troubleshooting approach. Baseline - make sure everything is spot on before you start changing variables or grinding.
Two things you didn't mention -
How is the temp?
Both cylinders knocking? Fuel distribution. Make sure the mixture is right.
If you deshroud the valves and do nothing else, you will loose a bit of compression, and the knock might go away, but you'll never know for sure if it was compression related or combustion chamber related.
The engine is water cooled . The top temp I got was 209 deg F. There is no "rainbow" on the plug threads or even any darkening at all.Ex the tip of the damaged plug was gone .The insulation was white.The pistons bottoms .Looking at the dome from underneath is normal with no discoloration.
I don't think I am melting down the pistons . The parts are like marbles like it was smashed .Not melted.
My thinking with deshrouding the valves is to remove the sharp edges.I would not do much .If I loose some compression I can go back to the 13 to 1 pistons. They have a thicker crown anyway.
I don't know if both cylinders are knocking . The damage is always on the right side#2 piston.
My main assumption is the mixture is off on the right side .
I will be checking and test everything for next time . I also will be adding exhaust temp gauges with high speed sensors for both cylinders.I am also thinking of building a dual exhaust so I can monitor both sides seperatly. with dual O2 sensors.
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CH3OH
Bill
Bill.
I have a system that will allow me to run a nitrous and Methanol mix and still run the engine with gasoline through the carbs. I really like this idea.BUT the smallest shot I can get is 15 hp on each side, That is a 30 shot. I was having clutch issues with the 20 shot I run now. It is the least amount I can run with my system. I "think " I have the clutch problem fixed .At least till I get more power .Then it starts all over again. :-D
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The tip of your plug missing is your key clue... that is where the hotspot is. Those electrodes make N20 torch the incoming charge. After you test your mixtures find retracted gap plugs. If your motor uses 10mm plugs your should be able to find retracted gap.
Do you know the weights of the N20 and gas you are adding? 5:1 is slightly fat, 6:1 is a little too lean for long button pushes.
Test...test...test
good luck
Yes I do have thousands of dollars worth of N20 experience..... :| :roll:
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The stock plug is NGK cr7e cr8e I run cr9e .But I will get the cr10e OR iridium if I can find them.
Am I correct in thinking that as the cylinder pressure goes up the resistance goes down? SO I should go from .028 to .019 as a gap . AND shim the plug up some to get it out of the chamber.
Am I also correct thinking that as the piston is going up the glowing hot plug fires off the mixture before the spark happens? and that is the same as advancing the timing?
I don't think the glowing plug is my PRIMARY problem though .Since I am getting detonation before I spray, Know I now if it is knocking in first gear don't spray.But it is a steep learning curve.
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O Young Ninja,,, "if you spray...you must pay" Eric I am afraid your need for speed has gotten you bit by the dark side.. the juice can be poisen.. when I drag raced bikes the juice cost me two engines back in the 80's.. I know N20 is more evolved than it was then,, but man it still hurts parts...!!!
Good luck,,, see you in June.. (oh I just got my F.A.S.T.) Drivers helmet cooling system arrived a few days ago.... ready to unpack the goodie box and install the system in the Stude later tonight or one evening this week (if time permits)...
Charles
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Curious - at what RPM does the knock start? Does the knock go away in the upper revs if you don't add the laughing gas?
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Curious - at what RPM does the knock start? Does the knock go away in the upper revs if you don't add the laughing gas?
The knock comes in a t low RPM and definitely goes away at the top RPM..It has been going on since the beginning. But until the nitrous it was not a problem. I have tried different ignition maps but have not gotten rid of it .
Charles
I am using nitrous to find the week parts of the engine. also it is a cheap way to get speed to develop the bike. These engines are 500 dollars on E bay all day long.Then about that much for pistons and other parts to make it race worthy.So for about a grand I can try again, So far things have gone well . But I don't want to break things regardless of the cost
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Am I also correct thinking that as the piston is going up the glowing hot plug fires off the mixture before the spark happens? and that is the same as advancing the timing?
What you just described is pre-ignition not knock. Knock can lead to pre-ignition but they are different processes.
High plug temps, can be due to too hot of a heat range on the plug, poor torque on the plug screwing up heat transfer to the head, lean fuel air mixture, or too advanced timing.
There is no law that says you have to run the same heat range plug in both cylinders.
Try running that cylinder with one heat range cooler than the other.
As you say check for fuel mixture imbalance, that cylinder may be running leaner than the other.
Many sources recommend retracted gap or short nose plugs on nitrous.
An engines octane requirement drops as rpm goes up, your low rpm knock implies you are running too much spark advance to me. Are you using spark retard when you go on the spray?
Are you sure both cylinders are running the same effective spark timing, if the ignition system has lots of spark scatter or some how fires one cylinder a bit earlier (in crankshaft degrees) than the other you will have a chronic problem with the most advanced cylinder. You will never be able to get maximum performance out of the late cylinder without getting into detonation on the advanced cylinder. Likewise with mixture imbalance the lean cylinder will always limit your power.
Also check your actual valve timing on both cylinders one may have more effective cam timing than the other resulting in higher cylinder pressures in one cylinder than the other.
Another possible cause is actual deck height and rod lengths or piston crown specifications, you might have a tolerance problem where one cylinder has all the short parts and the other has all the long parts so their actual compression ratios are not what you think they are.
If you are using port injection of the nitrous, you could also try running richer jetting of the N2O in that hot cylinder.
Aircraft engines have some of the best research on internal combustion engines. You might find these two articles useful.
http://www.avweb.com/news/pelican/182132-1.html
http://www.avweb.com/news/pelican/182084-1.html
When all the shouting is over, knock (detonation) is a function of peak cylinder pressures and charge air temperatures, those two parameters determine what the octane requirement of a specific engine is, with proper ignition advance and fuel octane, being secondary. Research by NACA during WWII found that with known ideal ignition timing, and a known fuel octane, they could predict the onset of knock in a given engine design, knowing only the intake air charge temperature and peak cylinder pressure. There was a maximum value for both that could not be exceeded without causing knock.
Larry
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I guess I should have called this thread Pre ignition control. I will have to read these links over a couple times to get my head around it.
I have been running my mixture very rich like 10.9 to 1 and it is even richer with the spray. But now I am thinking I need less timing and a leaner mixture.
Data acquisition is the key to not doing the same thing over again. I am going to spend some money on that . I have the innovate LM2 and I can run an O2 sensor for each piston. That with EGT should help. Dyno testing will also be a regular thing from now on.
One thing I did not mention. When I was running 13.25 to 1 pistons I had a head that I polished the combustion chambers on. With the 12.5 to 1 pistons the "pre ignition" seemed to be worse even though I had a little less timing. Dose polishing the chambers help that much?
The second photo is the damaged head from May. I will repair that this week.
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this is the piston from May.
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Eric,
Consider a faulty ICM. IIRC you have an aftermarket adjustable unit now. Maybe it is not doing what you are telling it to do. Consider replacing the stock one for next meet.
Also I wonder if you have a partially clogged fuel jet/passage for that side carb.
As for the plug, as mentioned by another post, the elctrode can be a problem with NOS. My Wizard of NOS guru in UK recommends cutting the electrode at the same length as the tip and then adjust the gap from the side of the tip by bending the elctrode stump towards the tip.
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One thing I did not mention. When I was running 13.25 to 1 pistons I had a head that I polished the combustion chambers on. With the 12.5 to 1 pistons the "pre ignition" seemed to be worse even though I had a little less timing. Dose polishing the chambers help that much?
I think you are attributing the change in behavior to the wrong thing. The 12.5:1 piston likely had less squish (and less mixture motion) which strongly impacts burn speed. The higher compression of the 13.25:1 would also speed up combustion, and I would suspect due to the higher compression ratio had better mixture motion. The polishing certainly helped, but it was not the only factor.
Detonation is strongly affected by both the ignition timing and the burn speed of the mixture. That is one of the reasons engines require less octane at high rpm than they do at lower rpm. Highest octane demand is usually at the peak torque rpm, because by definition that is the point the engine has its highest cylinder pressures (and most efficient intake volumetric efficiency).
Fuel air mixture also controls burn speed, with mixtures of gasoline near 12.5:1 - 13:1 having highest burn speeds in most cases (varies with specific fuel and engine design). The burn speed slows down if you go either rich or lean of what ever the best burn speed mixture is for your engine.
Looking at your pictures I think you had both pre-ignition and detonation. Detonation tends to break things (piston picture) and pre-ignition tends to torch pistons and heads (cylinder head picture). I suspect you had detonation that rapidly progressed to pre-ignition which only stopped when the cylinder pressure blew the top out of the piston.
For detonation to occur you need to hold the fuel air mixture at high pressure and temperature for a period of time for the detonation sensitive precursors to form as the hot fuel breaks down. This is why octane demand drops at high rpm, there is less time for the detonation reactions to take place.
At some critical heat pressure and time value that fuel air mix that has not yet burned normally, suddenly ignites and burns at near detonation velocities (speed of sound in the fuel air mixture) rather than burning normally along a flame front, causing huge over pressure spikes that break things. The high pressure shock waves strip off the thin insulating layer of gases that helps hold temperatures in check on piston crowns, valves and spark plugs and temperatures of the surfaces skyrocket even though the actual combustion temperatures are lower. This can very quickly make any sharp edge in the combustion chamber like a valve pocket cut out, piston relief edge or spark plug electrode get up to melting temperatures.
The burning/detonation process of knock happens so fast that even at 200,000 frames a second high speed camera speeds NACA had difficulty recording the actual detonation process.
Larry
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You have piston to head clearance issues with the piston closest to the cam chain galley...what is the piston deck thickness and make sure you check piston to head clearance with both pistons..
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So far the only things I have checked is the piston clearance. I checked it with the 13 to 1 Pistons I assembled the engine with out gaskets then turned the motor around. I also had the valves in the head with no springs .I could move the valves at TDC . Then with gaskets the clearance was greater . I hope.
. I don't want to use the stock Ignition control module.it is set at 35 deg. The one I have seems OK at least I know that when I switched maps the knocking sound in first gear went away on the next pass. Stock timing is 35 deg BTDC. I run as much as 42 at 12000 rpm and as little as 32 in the lower rpm range all motor.
I did all my ignition tuning for the all motor part on a dyno. But I have yet to spray nitrous on the dyno because I was afraid to blow the motor. Now I an afraid not to test on the dyno because I might blow the motor. :roll:
With nitrous I was at 32 max.Now I am thinking 25 max I can change maps with a switch on the handlebar.
This week I will go into the carbs then I will do all sort of testing with my nitrous system. I will video that
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Any sharp edge heats quickly and the incandescent surface will cause pre-ignition. Sharp edges on the electrode make the plug work better, but can be a source. Sharp edges can also be microscopic defects in the head or piston. The carbon buildup on the piston is a prime place for this to happen. I wouldn't run an engine that has any carbon visible.
Detonation is a simple function of achieving ignition temperatures without the benefit of the spark plug controlling the timing. And it is detonation. It happens ahead of the flame front that is rapidly expanding from the spark plug. Instead of a uniform flame front the detonation (think explosion) causes sharp rises in pressure that results in sharp rises in temperature. High temperatures and high pressures are the cause.
Lowering the temperatures by cooling the intake charge, cooling the fuel (rarely done, if ever), water injection, turbulence through intake design (turbulence causes better mixing. Non-uniform mixing promotes detonation.)
Compression ratios and timing as mentioned. Don't bog the engine. Low rpm's promote knock. A different gear ratio might help.
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Reread the post from Stainless 1. If you still do not understand what he is telling. You, talk it over with a friend. It is very good advice,
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Reread the post from Stainless 1. If you still do not understand what he is telling. You, talk it over with a friend. It is very good advice,
O yea that is good advice. I will do all that and test test test everything I can think of .Part of my problem is testing on the track not on the dyno. I need to forget about records and points and just think about speed. That is all that matters anyhow.
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Racer X, many posts ago an iridium plug was mentioned. These have a fine wire center electrode. This might not be what you want for this application.
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I agree with that.
The iridum was sujested by JE pistons . I am going to go with cr10e and trim the electrode like Like DrJ sujests. This will make it more of a serface gap. .and I will make that gap.019. Thanks
I made a couple practice plugs. It is not an easy thing to do. I am afraid to fatigue the welded on tip. So after careful cutting and filing I want to do the bend in one shot. I got this one to .024 I will get a box of cr10e Plugs and make some new ones.
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O yea that is good advice. I will do all that and test test test everything I can think of .Part of my problem is testing on the track not on the dyno. I need to forget about records and points and just think about speed. That is all that matters anyhow.
RX, dont start your motor again till you know what you are putting in it. N20 testing in done without starting the motor. The subject has been discussed here multiple times, so do a little searching and reading and you will understand what I am saying. I hope the plugs you are making work out, if not you will find a picture of retracted gap in one of those N20 threads. Rick at ERC has them. It also sounds like you may have motor problems without N20, work those out first. It also seems to me that you are running too much timing, but your motor may require that much.
We ran a little over 10 lbs of N20 per minute through our 1 liter, pulled 10 degrees of timing.
again good luck with your quest
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..modification..i see stainless and i posted about same time..oh well ill leave it..
..why not save some money and buy a spark plug or two that
is manufactured as you wish to use it...?..(ps really read what stainless
said)....
imo:
you could call Rick Gold at ERC for plug configuration and heat range of your
choice...tell him joe amo sent ya...:).....and while your at it...i "strongly" recommend
you put some proper fuel in it!!!!...Rick can get you that as well..!!! or at least use VP c16...
...you can do all that piston and comb chamber massaging...but again imo.....focus on
nitrous to fuel ratio's and timing and fuel..these cost almost nothing to get right without hurting
anything....if it was me (so take it with large grains of salt)...i would only dyno to get normally aspirated dialed in...
Joe :)
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You may have noted a couple of references to ERC. I would highly recommend running their fuel. Not to mention they have given us a ton of support.
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Thank you all for such sage advice. It will start with the nitrous fuel ratio testing and you can see what I am doing. This is a very different system than many prople use.
I am still thinking the nitrous is not the problem but everything else is.IE to much timing carb tuning and the like . When I was starting out .the engine responded to using a rich mixture and very advanced timing. Now that I have raised the compression I still have not takin the timing back enough. I am going with a blank sheet and starting over with the nitrous tuning.
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My bad earlier - knock/detonation.
We're all thinking ignition timing, but what about valve timing? Seeing that it's apparently just one cylinder, this may not be pertinent, but if you've got it opened up, I'd grab a dial indicator and a degree wheel and double check your valve events on both cylinders.
Earlier I was thinking the intake cam might be advanced a tick, effectively raising your dynamic CR, which would give the charge a prolonged period of time closed off in the chamber on the compression stroke before reaching TDC. Too much time in the cylinder, low RPM, an effective increase of the dynamic CR - sounds like a recipe to me. It's not likely that one set of lobes are off, but it's not unheard of, either.
Ton of variables and no silver bullet in my holster, but keep us posted.
Stainless is spot on - don't fire it up until you know.
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Both cams are retarded just a bit. I cut the top of the block down .010. That rolled the cams "some"
I am spending a lot of thinking time figuring out how to set up test to video so we can all see what is going on. Thanks for all the help.
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The iridium plugs should work good when the motor is sorted and flame control is OK. They are my plugs of choice.
Take the head off the engine and move the pistons to 5 degrees ATDC. Push down on the crowns. It is hard to make them move. Try again at 10 degrees ATDC, and at 15 and 20 degrees. Progressively it is easier to push them down. This illustrates a big problem with poor flame control from detonation or pre-ignition. The burn is too near to TDC. The pressure spike in the combustion chamber occurs at a period in the cycle when the leverage ratios between the crank and the rod are not optimum. Best power occurs when the pressure spike occurs more past TDC when piston and rod's leverage on the crank is favorable. It takes a controlled burn to get this.
Stainless and the others on this topic give good advice. My meagre contribution is this. A poorly controlled huge pressure spike from lots of gas and compression may not make as much power as a smaller and more controlled spike at the optimum point to give max power. Dyno testing works best to figure this out.
I think you are on the right track and doing the things you should, This is an interesting problem.
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I hope to solve this problem with careful testing and tuning. Pushing engines to the limit is always interesting.I am looking into getting a dyno of my own. I can use it at work and make money plus save money . The neighbors will like it too.
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That damaged head looks familiar
spark plug selection helped our prob,
initially we indexed the plugs we had, so the gnd side of the tip was between the inlet valves and cooler, (damaged cyls always had the tip near the exhaust valve, we also used an extra washer to pull the plug out of the head more.
but in the end went with a cooler range plug without the extended gnd strap..
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I have gotten my head around what you are saying about a smaller explotion later when the crank leverage is optimal . Thanks for that.
I think a combination of a cooler plug with a different ground electrode shape and gap. Then polish the combusion chamber and recess the plug. With 13 to 1 pistons. Add 118 octane fuel up from 111 .And 25 deg BTDC timing instead of 32 I tried last time. Will be my basic set up. Now I just have to test the fuel and nitrous ratio and volume put it all together with a new exhaust system and try again.
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The suggestion about an iridium plug working good is based on a lot of experience with NA motors. I was not thinking and forgot that this is a nitrous burning setup. Ignore that advice I had about the iridium plug working good.
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I can't ignore anything from this forum.I will save that info for my all motor thinking. I like the idea of them but I have trouble reading them and when as you said .I would not use them untill things are perfect otherwise.
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Well I did some testing.No matter how I test it I am lean on the right cylinder.That explanes the hole in the piston. I will work with the rest to get rid of the ping or crackle I was getting in lower gears. No nitrous till I figure out both of these issues.I am going to work on data logging and testin for a while.
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I sent my system back to the manufacturer. They tested it for me and found the same thing I found. There was a machining defect in one injector.They have had some problems with drawing such a small amount of fuel.
They made me a new set up that they tested. I will test it myself today and see how it goes. Since they are having problems with 10 hp I decided to go with 15 hp. I should have enough clutch for that.
But apparently my problem was not preignition or detonation. At least that was not blowing a hole in the right cylinder. I was dry shotting the engine at least on the right side
I have am still going to do all I can to prevent preignition. First I am going to use cr10e plugs with the tip removed and regapped. I will take the gap from .028 to .019. I also cleaned up the damage to the head and polished it to remove any ruff edges. As for timing.I am a bit gun shy. I have had success with the stock timing setting of 35 deg BTDC, But I will start out with 28 just to be safe. All that with 118 octane fuel should be better than the last run.
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OK I ran the nitrous flow test. I need to do it again to measure the volume out.I hoped it would blow nitrous up and the fuel would collect in the jar, But it is so well atomized it blew the fuel everywhere . BUT it looks even and there IS fuel flow .When I did this before there was no fuel flow at all or a little after it started spraying. This is looking much better.
http://youtu.be/Gr4_azWJ688
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believe me, the fuel is not well atomized coming out of a typical nitrous
injector......ask NOS....about their own testing......(eyeballs dont see
atomization very well).....
why not buy a spark plug such as is available from Champion thru say ERC that
is made for what you are doing such as was suggested a long time ago, rather than carve
on a plug hoping to do better..?..
and yes it was detonation that put a hole in your piston......:)
Joe :)
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Didn't the detonation come from a lean condition? Yes I will look into proper plugs.I am afraid I might fatigue the tip when I bend it.
This is not a a regular nitrous injector. This system uses nitrous to pull the fuel in (no pump). The nitrous and fuel mix inside the injector.
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you bet...detonation from inadequate fuel supply..:)
wow no fuel pump...learned something again today..thanks for that...out
of my league on that one...we used to use a large graduated burette as the
fuel supply...run system...and record fuel in burette at start and at end...
Joe :)
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Today I was looking at the videos of the nitrous test I did . I wanted to re do it and catch the fuel. When I looked at the video the right side looked like it was flowing more gasses or at least making a bigger cloud. I retested it and it did look different from side to side. I then swapped some parts from one side to the other and not only does it look more even, it looks like it is making a much bigger cloud. When I was swapping the parts fuel was dribbling out of the feed lines. I think it might have primed the system.
I am afraid of bad gas so I remove all the old fuel from the system as soon as I get home. IF the first video is any indication of what I have been doing. Then it might explain why one side is running OK and the other side is damaging a piston .The next time I push the button will be interesting .
test 1
http://youtu.be/62QMp_4KIHY
test 2
http://youtu.be/VpT34a-iBQA
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By the looks of your test, since you have no fuel pump and must use N20 to pull fuel you need to weigh the fuel in the supply tube before and after the test. Run for at least 20 seconds, weigh the fuel and the n20 before and after the test, that will give you the ratio you are running.
Just my random thought... you are getting N20 before you get gas since the N20 is used to draw the fuel. To me that says you are already starting in a lean comdition then it comes back to a ratio, that instant of lean will fry pistons, valves and heads.
scares me and I'm fearless.... no wait, I'm Stainless.... :roll: :roll:
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The nitrous system has what are called nitrous powered fuel injectors. The nitrous powers the injectors that draw the fuel. There is enough draw to lift fuel as much as a couple feet. Though my set up is gravity fed. From the data logger the system starts rich then goes to the proper mixture.
I cant tell how much fuel is coming out. But it did leave an even amount of gas in the jar after I removed the injectors from the manifolds and aimed them at the jar. I did measure the volume though. I sprayed one pound of nitrous and it drew in 40cc of fuel.I think it is 13.5to1
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OK, now we are getting somewhere...
If you are telling me your ratio is 13.5 N20 to 1 fuel then that will burn down the motor every time. By weight the ratio should be 5:1 (rich) to 6:1 (lean). That means your 40cc of fuel needs to weigh 3.2 oz. to be at a safe starting point.
Then get retracted gap plugs and you should live through the long button push.
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This is why I don't sleep well.
After thinking about it all night. I got 13.5 to 1 by converting 1lb to cc and then dividing by 40. That has to be wrong. But the number came out to 13.5. Kinda what I was looking for on a normal AF ratio. :oops: And the measurement was taken with the first test. That test was done with the system operating unevenly as in the first video.Now that things are primed and seem to be working properly I will need to re test.
Thank you for you help. Going fast means going slow some times . This is when I need to take time to be sure it is right.
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Eric,
If you used 1 lb of NOS for 40cc fuel then you are way lean based on Stainless numbers above.
1lb =454gm and even assuming the fuel weighed the same as water then 40cc=40gm. So 454/40=11.35:1 for a NOS:fuel.
But be sure in your test that you are using the same fuel lines as on your tank so you don't restrict the flow before it gets to the NOS powered piston pump.
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racerx, did you measure fuel used via the burret method or are you trying to capture
fuel into something after it falls out of the n20 cloud ..?...
i think if you rig up a fuel holder and measure in cc or by wt the fuel, then run the test
and then decipher how much is missing from the supply vessel you will have better grip
on fuel used....
stainless and many of us are a bit put off by drawing fuel by a nitrous siphoning effect, as
many of use set up our system to have fuel flow first and after this is verified by say a pressure
switch that switch in turn allowd nitrous solenoid to then power up...always having the fuel first...
not saying you need to do this, or that it is even correct...just the view point some are coming from...
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...just the view point some are coming from...
and those " some "--
seem to have nitrous dialed in pretty well
have been doing it for quite a while
n go pretty durn fast with big mills
I think they are on the right track.
good luck x.
bf
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Hey Guys
Thank you all very much for the help. I am trying not to advertise on the forum But this video will explain how this system works.
When I have captured data from using it ,the system seems to go rich first. The "hit" is very soft when I push the button.
http://youtu.be/pmsJfmnrrNs
http://youtu.be/bUhHUbLpGQI
I am going out in the shop now and re test this . I will weight the bottle before and after.That is how I will measure nitrous volume. I have the fuel is a graduated cylinder. I measure the volume going in to the system. I tried to capture fuel coming out .But that is not very reliable. Seems the fuel goes into the air and I cant catch all of it . But I will video the cloud to try to determine if both sides are even.
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OK nitrous test #3
I set things up again. This time I tried to be more careful and record data better. I liked doing this after letting the system sit to see how it will do at the track. .This is the mixture I plan to spray in September.
http://youtu.be/b_1FFYkROig
This is a link to the test . I sprayed for 5 sec. The volume looks like it should. Notice how quickly fuel begins to move. As soon as I hit the button fuel starts to drop.
Full bottle weight 3lb .6 3/8.oz
After 20cc the bottle weight was 3.0lb
There was a 1/4 oz of nitrous in the lines so there was a little less than .3 3/8 oz of nitrous for 20 cc of gas.I honestly do not know how to calculate the ratio. :-(
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Since you system will not allow you to catch the fuel you flow do it this way.
Weigh the container you put fuel in, weigh the container with fuel in it, the difference is the fuel weight. weigh the leftover fuel, the difference is fuel you put in the cylinder.
Test each side, one at a time... the cloud is N20, you won't see the fuel if it is atomized correctly.
start with the lines full if possible, you want to be as accurate as possible, your pistons are counting on you :-D Rich is your friend, lean is the enemy, 5:1 has always been my goal for a long button push.
I collected data on every jet, I rechecked my math from my data at every jet change, power went up, ratio stayed the same within a .1 or .2. My last N20 engine failure was a Carrillo rod... bent under the combustion pressure until it hit the crank counterweight. :|
We killed lots of parts before we stopped believing the jet selection choices from the manufacturers, did the research, built in our own safeties, and tested, and tested, and tested. Some engines might live through the couple of seconds of button that they get drag racing... if you push the button for 10 to 58 seconds, you better have everything right. The fuel system must be fully sorted without the N20, then the N20 and enrichment fuel must be treated as a separate unit, you cannot look at final AFR and say you are good. Don't forget timing, personally I liked to pull 3-5 degrees for N20 in general and then 1 more for every pound per minute that I sprayed. I really can't offer much more than my own experience with our zx-7 and zx-10 motors, other than I used the same ratios with both.
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Eric,
If you used 3 3/8 oz of NOS then that is 16/3.375 oz X 454= 96gm.
Then you used 20cc of fuel which should weigh about 20gm so then 96/20 so ratio of NOS/fuel is 4.8:1
Should weigh the fuel to see what the weight/volume actually is to be more accurate.
Stainless and Joea,
Thank you both for all your info. Eric and I are both listening. I finally will get to the salt for BUB 2011 to spectate only on Sunday and Monday.
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What sort of air fuel ratio number should I see on the data logger when I run the engine down the track? and What sort of exhaust temp should I expect?
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Just to update this thread
I believe the problem I was having was the engine was going lean.
The problem with the Boss Noss system is basically the fuel lines are two small. The system leans out after a short period of time.
I switched to the Wizards of Nitrous system. Becides the fact that the system worked . The customer support has been over the top . The owner of the company helped me put together a custom system.
In July at Ohio I made a small test . Spraying 90% of ten hp to test the system. I pushed the button at the 3/4 mile marker. The bike went from 92mph to 111.042 mph at the trap. Engine exhaust temps stayed under 1200 deg. F and the plugs looked perfect. Next test will be in September . But it looks like my detonation/ preignition problems are solved.
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The September test went well.I used a 30 shot of nitrous and managed to get 123 mph. I did not have things tuned to optimum power and it was not a clean run at all.
No detonation and EGT stayed below 1250 deg F.
The Wizards of Nitrous system works perfectly. And I have no engine damage. Now that I have that sorted I can move on to tuning.