Feul Injection and Altitude Power Loss

[dr1ft3r]

Okay, so I'm pretty new to bikes. I know all things considered equal, an engine will produce less power in higher altitudes because of the thinner air. Cars, bikes, even lawn mowers generate less power up here in Denver than it would at sea level. My first thought on this topic is why do cars retain better power up here than bikes. I've seen dyno charts on cars that have around a 10-15% power loss when dyno'd (uncorrected) in Denver as compared to the same dyno at sea level. Bikes on the other hand have like a ~25-30% loss. In many instances these bikes are carburated, as compared to most cars being fuel injected. I've heard the most common reason for this discrepency is in the higher complexity of the fuel/timing management system in fuel injected cars. Well, even in the newer fuel-injected bikes (F4i, Ducati Monster, etc.) with modern computer management systems there's still a larger power loss when compared to fuel injected cars. Why is this? Is there a bike on the market that defies these numbers and has a computer management system that matches up with those computer management systems of cars? I know I haven't backed up any of my numbers with actual proof, so please correct my numbers as necessary.

Just wanted to see if anyone could help me better understand. Thanks.

James

[Hoopty]

I dunno, but it may be that bikes are so high-tech/high performance that taking the oxygen away makes a bigger difference on a bike. :?

[Anonymous]

Just a guess ... but cars are able to get away with larger airboxes and intake systems, which can help compensate for that more. Also, I think cars are detuned at the factory, so the EFI system has more room to adjust for the difference. If you were running your car at the limits of it's performance, you'd likely notice a similar drop in power at altitude. Bikes are set more for what they are capable of (still a detuning from the factory, but not as severe as the governmental regulations are not as bad) so when you make that drastic of a change in air density, it doesn't have as much room to adjust.

[Anonymous]

I don't know for sure if this has anything to do with it (or if it even makes sense), but here ar my thoughts:

The power band for a bike (especially peak HP) is usually at a higher rev-range than for cars, meaning the engine is spinning faster, the pistons are pumping faster & trying to suck air in faster. Perhaps the effect is parabolic in that at, for example, at 6000 RPM, the power loss would be 10-15% (the way it is for cars), but when you get closer to the top of the rev range, the lack of oxygen takes its toll, increasing the power loss.

Or, it could just be like the saying goes:
"There's no replacement for displacement." :D

[Anonymous]

Or, it could just be like the saying goes:
"There's no replacement for displacement." :D

Doubt that ... I could go build a 400HP busa engine right now on 1300cc (1.3L), or maybe 1380cc or so with a big bore kit with nothing more than a good turbo/exhaust kit and some reinforced engine components, whereas my 3.4L 4runner would be at 245HP with a supercharger and exhaust system. (Of course those HP values are for standard atmosphere i.e. sea level, would be much less up here.)

The power loss would be as you suggested Bob, in terms of absolute loss. i.e. let's say you lose 10%, and at sea level your 3k RPM HP is 80, your 8k RPM HP is 120. So here your 3k RPM HP would be 72, 8k RPM 108, etc... The percentage loss would be linear for the most part, of course this could vary somewhat with intake design but it's a good base to start from.

Air usage in an engine naturally increases with RPM, linearly as well. It would follow the same percentage curve.

[MattTLS]

The loss in power will be the same no matter what the vehicle-type. And I believe that loss is approximately 3% per 1000' rise in elevation. Of course, this is assuming the air/fuel mix has been properly adjusted. In other words, with any given engine, that loss will be about 15% in Denver as compared to at sea level.

However, one advantage to being at higher elevation is that octane requirements for a given compression ratio will be less than those for the same engine at sea level.

Matthew

[Bryce]

cars run a closed loop system and can adjust air fuel mixture with more percision due to the ability to monitor exhaust gas composition and correct bikes do not have o2 sensors so they connot monitor exhaust gasses in other words the high tech bike fuel injection is low tech leftovers from 70s car technology and runs blind folded. if it wasn't, there would be no need for fuel commanders etc.



Bryce Random racing #418

[MattTLS]

cars run a closed loop system and can adjust air fuel mixture with more percision due to the ability to monitor exhaust gas composition and correct bikes do not have o2 sensors so they connot monitor exhaust gasses
Bryce Random racing #418

Exactly. And until bikes' fuel injection technology catches up with that of cars, there will be a continued need to be able to adjust the A/F mix some other way.

I think it's strange how bike technology can be so far ahead and ever improving in some areas, but in others, it lags behind that of even mainstream American automotive technology.

Matthew

[dr1ft3r]

cars run a closed loop system and can adjust air fuel mixture with more percision due to the ability to monitor exhaust gas composition and correct bikes do not have o2 sensors so they connot monitor exhaust gasses in other words the high tech bike fuel injection is low tech leftovers from 70s car technology and runs blind folded. if it wasn't, there would be no need for fuel commanders etc.

Bryce Random racing #418

Bryce, great explanation. So who makes an O2 sensor add-on for our bikes? ;)

[Anonymous]

cars run a closed loop system and can adjust air fuel mixture with more percision due to the ability to monitor exhaust gas composition and correct bikes do not have o2 sensors so they connot monitor exhaust gasses in other words the high tech bike fuel injection is low tech leftovers from 70s car technology and runs blind folded. if it wasn't, there would be no need for fuel commanders etc.

Bryce Random racing #418

Bryce, great explanation. So who makes an O2 sensor add-on for our bikes? ;)

It would require a whole new computer for the engine, the current one just doesn't know what to do with it.

I am researching the DIY-EFI stuff though, the kits and plans available offer some *very* featured EFI setups, with open source software and the whole nine. Pretty affordable, and I know of people using them in cars with much success. I'm debating retrofitting something like that to one of those old Yamy's I'm restoring, just for educational purposes. If it works well, I see no reason it couldn't be adapted to an FI'd bike engine along with the benefit of additional sensors. And since the DIY-EFI stuff can be programmed with a PC, there would be no need for a Power Commander or other signal trickery aside from a new EFI computer. I will let y'all know what I find out on it...

[MattTLS]

It would require a whole new computer for the engine, the current one just doesn't know what to do with it.

I am researching the DIY-EFI stuff though, the kits and plans available offer some *very* featured EFI setups, with open source software and the whole nine.

Motec sells replacement ecu's that may work with a lambda sensor to adjust the A/F mix while running. But they're expensive.

Matthew

[jwimbauer]

When you talk to some of the car guys - they experience a similar level of powerloss as bikes do - approx. 25% (I think it is actually 5% per 1000ft) which is pretty much what my Firehawk is registering.

However, it really depends on day and time of year. Having raced two-strokes for so long and wrenched on Nicky's 125 for 3 years, we decided to get a sophisticated weather station. What we found out that there are times in CO where the Air Density ratio is only 5-10% lower than at sea level. In fact, we had days where we ran the bike richer in CO than in a bad TX air environment (hot, lots of humity).

Most performance oriented machines make up with compression ratios that would throw you into a backwards path at sea level. Also the RAM-Air effect is being calculated different (less difference - don't have the formula) with thinner, yet cooler and dryer air.

That opens the question - does anyone in CO have a dyno that simulates RAM-Air???? Most bikes being adjusted on non Ram-Air dynos are way to lean on the main jet/lower right fuel cell block.

We picked up almost 10HP on our R6 (that was jetted locally) above 100mph (calculated upon gearing and accelleration values) by going from the "recommended" 126 mains to a very "don't do this 134" main jets. And we lowered the operating temp by 12 degrees.

thanks



Jurgen

[Anonymous]

Jurgen, remember that air density is based on a "standard day" atmospheric setup, i.e. sea level at a given temperature and RH value. (I can't remember off-hand, but 72 degrees sticks in my memory.) Out here we're colder half of the year and almost always dryer than sea level, say California or Texas. What you saw was definitely possible - I will dig up the link I found which calculates it all for you, very good for determining exactly what's going on.

Your Ram Air jetting makes sense, of course you will lose power at low speeds but once you raise the airbox pressure (i.e. >100mph) you are good to go. This is great on a track, but would be worthless on a streetbike. I'm curious, are those "don't do this" jetting values for street, track, or just a general no-no? Were those numbers recommended by Yamaha? Factored in for altitude?

There are no Dyno's in Colorado or anywhere close that I'm aware of which can simulate Ram Air. This would require wind moving past the bike at 100+mph, which is unsafe to say the least. The only real way around that is to pressuize the intake at the front of the bike somehow, which would be technically challenging. You're carb'd so you wouldn't have to worry about matching the air pressure with rear wheel speed, so that makes it a little easier. I also have a link somewhere to an article where someone measured the actual pressure boost in the intake from the Ram Air system on his bike - that could be used to know just how much air to push through the intake from a blower or something similar to simulate the right speed; I can try to find this if you're interested.

[dr1ft3r]

Simulating the whole ram-air effect would be extremely difficult to simulate as both rfor and Jurgen point out. So when you see a dyno graph for a bike, would that mean those numbers at the rear wheels are higher once at speed or are they already corrected to reflect the fact they are not getting the ram-air effect?

James

[Anonymous]

Simulating the whole ram-air effect would be extremely difficult to simulate as both rfor and Jurgen point out. So when you see a dyno graph for a bike, would that mean those numbers at the rear wheels are higher once at speed or are they already corrected to reflect the fact they are not getting the ram-air effect?

James

The numbers would be higher at the rear wheel, but you also need to compensate for it with jetting, i.e. you need to use your mad ninja jetting skills to just know how much richer to jet it, since with the Ram Air you will be leaning it back out some determinate amount (based on speed, absolute baro pressure - NOT "corrected" like you always see which is what weather stations show you, temp, humidity).

It takes a little math, but you could put a small hose fitting on the side of the airbox, as close to the intake bells as you can get. Run that to a boost gauge and measure the PSI increase in the box. From there you can figure out how much more air you are adding to the bike and jet accordingly, but it's still a trial and error process. (cap off the fitting when not used!)

This is one area where FI really excels I think, because you can adjust the map for both standard pressure (i.e. low speed) power, and increased richness for when the Ram Air is doing it's job. Carbs are limited in this fashion. FI can be programmed based on RPM and gear I believe, hence vehicle speed, so you really get granular control that isn't possible with a carb setup unfortunately. This makes for better streetability, though if you spend 75% of your time at high speed/high RPM on a track you can jet for that and still get good gains from a carb setup. You just miss out in the low speeds, i.e. cornering and accelerating out of corners.

[jwimbauer]

Simulating the whole ram-air effect would be extremely difficult to simulate as both rfor and Jurgen point out. So when you see a dyno graph for a bike, would that mean those numbers at the rear wheels are higher once at speed or are they already corrected to reflect the fact they are not getting the ram-air effect?

James

I totally agree with you guys which leaves us with the fact that we can tune a bike when it stands still but not when it is in motion.

I just typed a long response but lost it when my IE shutdown (damned). I believe that a dyno tuned bike will actually LOOSE HP when in motion (> 70mph). The mixture will be too lean on the main circuit which leads to a slower reving and pickup.

To elaburate on my story from last year when we purchased a "dialed in" 2000 Yamaha R6 (which made top HP with that jetting). The bike ran OK (average) - a bit hot for my taste but didn't really have the kick in 4th. 5th and 6th gear. We weren't any slower or faster than the average 600 on the track. I re-jetted the main from a 124/126 to a 134 and raised the needle by a half clip. We then picked up approx. 1100 RPM at the end of Pueblo's straight which made us go from a 50 rear sprocket to a 49 and a gain of 15mph. Nicky could stay in half-drafts of GSXR750 and the typical R1/GSXR1000 was only able to pass under power approx. 500ft later than before and it allowed us to get back by them under breaking.

So, how in the world can we achieve a good Ram-Air dyno numbers. I heard that there is a "on-board" dyno available (kinda like the G-Tech pro, based on lateral G-force measurements :idea: ).

Any ideas ????

BTW - we will do some dyno testing this weekend on our new R6 - any bets????


thanks

Jurgen

[Anonymous]

I just typed a long response but lost it when my IE shutdown (damned). I believe that a dyno tuned bike will actually LOOSE HP when in motion (> 70mph). The mixture will be too lean on the main circuit which leads to a slower reving and pickup.


A Ram-Air bike definitely will, it will be way too lean if you tune it for static air conditions. A normal intake could I suppose as well, though I'm not sure which way that would go. Part of me says the high pressure of the air hitting the front of the bike could transfer inward to the intake which normally just sucks the static air around it and lean it out, the other part of me thinks the bike moving through the air would create low pressure areas aft of the front fairing area (bikes are not clean, aerodynamically) and actually suck air away from the airbox, resulting in too rich of a mixture and incomplete combustion. A good test would be to run a bike at high speed for a while at high throttle (i.e. high air usage) conditions, then without slowing down hit the kill switch and brake to a stop in neutral. Then pull the plugs and see what is really happening. This would let you adjust your jetting accordingly. Any takers? :D

Dyno's only go so far. This is why test and tune days are so important, because what the computer screen at the shop tells you can be vastly different than the real world conditions you ride in. Dyno's are marginally acceptable simulators but are not the be-all end-all tuning god people make them out to be. Experience (which I don't have a lot of, I just pick up on a lot of things and can "visualize" what happens inside an engine and with airflow easily) and a good sense of the black art of tuning go farther IMO.

Juren re: your on-board dyno, I'd suggest something different. We can agree that to get the most power, you want a stoichiometric (ideal) mixture, right? So you just need to watch the richness of the mixture being burned. A portable EGA (they can be had cheap) would do this for you and tell you exactly what was happening inside the engine at speed on your bike, Ram Air or not. One that datalogged would be even better, but would be a lot more expensive. Just have Nicky ride with one for some track sessions and make note of how far rich/lean it is at various speeds around a couple laps once the bike is warmed up, then play with the settings until the mixture is perfect.

[jwimbauer]

I hope we don't bore the other folks with our "geek" thread :)

I doubt that the mixture will be richer under ram-air condition. Some dyno testing (actually some Yamaha Germany white paper if I remember right) under ram-air conditions revealed a whopping 125HP for the new r6 at 140mph.

Our new exhaust system has a plug for an O2 sensor - perhaps I can find something to log data with that.

I've never done plug-jobs (full throttle - kill switch) on 4-strokes since I didn't know how accurate they were. It worked great on the 2-strokes - we'll try that.

Just for grins and giggles - I have a leaf blower that claims air speed of over 100mph. I will hold that damn thing in front of the r6's air intake (heck it's under warrenty <G>) while running it on the dyno and compare top HP. I'll you know if you are interested. Also, I can't wait how our new exhaust system will perform compared to stock.

Or, I do have a bunch of R/C airplane motors with props laying around. These things have power and move air quickly - I could hook it up to the remote and inject air gradually as we roll on the throttle.

And that would make me a propeller head ... :crazy:

[Anonymous]

I hope we don't bore the other folks with our "geek" thread :)

Heh, well this is bike tech forum. :D Actually I'm having fun with this chat. This is the kind of stuff I like to do...


I doubt that the mixture will be richer under ram-air condition. Some dyno testing (actually some Yamaha Germany white paper if I remember right) under ram-air conditions revealed a whopping 125HP for the new r6 at 140mph.

Under Ram-Air, no. It would lean out. My thought is that a static air system (non Ram) could actually richen itself depending on the aerodynamics of the bike itself. You run ram air so it's not really a concern for you, but on non-ram bikes I wonder if making a shell around the intake assembly, so that it then becomes exposed only to the front of the bike, wouldn't actually help since the low pressure would not affect the intake that way.


Our new exhaust system has a plug for an O2 sensor - perhaps I can find something to log data with that.

What kind of sensor? I can point you to some cheap ways to monitor the exhaust levels if you know that...


I've never done plug-jobs (full throttle - kill switch) on 4-strokes since I didn't know how accurate they were. It worked great on the 2-strokes - we'll try that.

Should work fine, just make sure you look at all plugs. I look at plugs even after a normal idle shutoff to tell me what the engine is doing and it says a lot that way, I've never done a WOT-kill thing either but I think it would work fine. It's also free to try... :)


Just for grins and giggles - I have a leaf blower that claims air speed of over 100mph. I will hold that damn thing in front of the r6's air intake (heck it's under warrenty <G>) while running it on the dyno and compare top HP. I'll you know if you are interested. Also, I can't wait how our new exhaust system will perform compared to stock.

Check your PM's...

[MattTLS]

Using a wide range lambda meter and a data logger is probably the best way to tune in real-world conditions. The simplest accurate setup to tune a fuel injected system would have to record the speed, rpm, throttle-position, and air/fuel ratio. Obviously, if no further changes are made to the setup of the engine, this would only have to be done once on a fuel injected engine, but the same isn't true on a carburated engine.

And that bung welded in the exhaust is where the lambda sensor would be hooked up.

It's not cheap, but the professional wide range lambda meter from Motec is $1000, and the four-channel data logger from Czech-Mate Tach-Mate is about $450.

If you want some info on this stuff, I know someone in Wyoming with this equipment. He will also travel anywhere to do the tuning himself so long as there are at least five bikes to tune at a cost of $300 each.

Matthew

[jwimbauer]

Using a wide range lambda meter and a data logger is probably the best way to tune in real-world conditions. The simplest accurate setup to tune a fuel injected system would have to record the speed, rpm, throttle-position, and air/fuel ratio. Obviously, if no further changes are made to the setup of the engine, this would only have to be done once on a fuel injected engine, but the same isn't true on a carburated engine.

And that bung welded in the exhaust is where the lambda sensor would be hooked up.

It's not cheap, but the professional wide range lambda meter from Motec is $1000, and the four-channel data logger from Czech-Mate Tach-Mate is about $450.

If you want some info on this stuff, I know someone in Wyoming with this equipment. He will also travel anywhere to do the tuning himself so long as there are at least five bikes to tune at a cost of $300 each.

Matthew

That is very interesting information - Andrew Drattlo is receiving a brand-new dyno (eddie current capability) and we are planning on spending some time on it.

The new R6 has several sensors in the airbox (air pressure, temp?) and adjust the mapping according to speed. However, the general mapping of an OEM bike has been traditionally always too lean (for obvious reasons). I've heard good and bad stuff about the power commander series and was wondering what fuel mapping device could be used to change the mapping (teka, fuel nanny, PWIII etc.) - any input?

Thanks


Jurgen
www.teaminfotech.com
(check out our PPIR school)

[MattTLS]

The new R6 has several sensors in the airbox (air pressure, temp?) and adjust the mapping according to speed. However, the general mapping of an OEM bike has been traditionally always too lean (for obvious reasons). I've heard good and bad stuff about the power commander series and was wondering what fuel mapping device could be used to change the mapping (teka, fuel nanny, PWIII etc.) - any input?

As far as I know, the Teka and the Power Commander are the best devices to change mapping -- I don't think the Fuel Nanny is as precise or as adjustable.

Ater recording test runs on the data logger, you'd transfer that info to computer. You should then be able to determine at what throttle positions/rpm the fuel mapping needs changing. The speed is recorded so you can test the effects of the air intake system on the air/fuel ratio. I don't remember whether the Teka unit can adjust according to gear selection, but if it can, that would be ideal. If so, a more sophisticated logger could be used to also record the gear position.

The person who has the stuff I described earlier used it to tune his very well built Suzuki TLS. Supposedly, the bike never ran better. He has since sold that bike -- the engine now belongs to Jim Smooth Brewer.

Matthew

[mikesf4i]

just throwing in another idea.... I remember reading in one of the bike magazines where they were building a bike (an r1?) to run in a horsepower/weight limited racing series ( dont remember which one) and they added a big ram air intake. They ended up pressurizing the float bowls. That way the pressure differential across the jets would stay the same. Therefore the mixture wouldnt change depending on how fast the bike was moving.

[brandon]

So I'm curious.. does anyone know how the volume of air being fed into the intake is measured on modern FI'ed motorcycles? I've never really had to tear down my bike that much to figure it out, but I'd make a guess that its just a mass air flow sensor.. just curious since I know a bit about modern fuel injection on cars, but not on bikes.

For instance I converted my 'race car' from a MAS (which is measured in Karman's) to speed density to get rid of the MAS itself since it restricts the amount of air flowing into the intake.

[MattTLS]

So I'm curious.. does anyone know how the volume of air being fed into the intake is measured on modern FI'ed motorcycles?

I'm no expert, but I don't know of any bikes currently using a mass airflow sensor. However, some are now using an O2 sensor in the exhaust (VFR800 and a Buell ?? I think) in a closed-loop, self-adjusting system. Most FI bikes' systems are composed of sensors measuring intake air pressure, crankshaft position (rpm), and throttle position (along with various other sensors which compensate for differences from the 'normal' conditions) which are used to determine the injection duration/amount of fuel.

Matthew

[dr1ft3r]

I'm no expert, but I don't know of any bikes currently using a mass airflow sensor. However, some are now using an O2 sensor in the exhaust (VFR800 and a Buell ?? I think) in a closed-loop, self-adjusting system. Most FI bikes' systems are composed of sensors measuring intake air pressure, crankshaft position (rpm), and throttle position (along with various other sensors which compensate for differences from the 'normal' conditions) which are used to determine the injection duration/amount of fuel.

Matthew

Matt,

You're right about the Buell XB9R and XB9S. My co-worker rides one and when I was pondering this a couple weeks back, he actually went through his owner's manual and found the part that references to the existence of an O2 sensor in the exhaust. The real world test would be to see how well the closed-loop system adjusts itself when moved from Denver to say Houston compared to a non-closed-loop FI system when doing the same move. Gotta love the competition among the different manufacturers. Us consumers are reaping the benefits of continued technological strides year over year.

James

[Solinary]

Hello,
I just recently returned home to Denver from Alaska (sea level), and I was wondering where the best place to take my bike would be to get a tuneup. I have definatly seen a loss in the bikes over all power as well as a couple other anomolies, such as a sag on quick hard acceleration, and would like to get her back in top shape. I would appreciate any suggestions for a reputable shop. Oh, and I am on the Littleton side of the state if that helps. :)

[Hoopty]

http://www.tfogracing.com/

[Anonymous]

http://www.tfogracing.com/
Yes, TFog comes recommended by one of the local racers (plus some other members). They're located in Golden, near where 6th Ave. hits I-70.