A simple way to measure VE (Volumetric Eff)

[Dunkster]

Hi guys
My first post so please laugh at me as much as you like.

I'm going to be carrying out improvements to our engine test rig next year. I was thinking of a cheap way to measure VE without having to go about modifying the intake manifold to much. Here is my idea please tell me if you think it is worth continuing my train of thought.

Instead of drilling holes etc into the intake manifold you fashion a tube out of pvc or something which can fit over the bellend of the throttle and give a good seal. Making the pipe 250mm long should give a nice smooth flow across its cross section. Now because total pressure is atmospheric, can I assume that down my pipe I have very negligable head loss compared to the rest of the intake manifold. So i can simply measure static pressure with a simple preassure transducer. (low pass filter to average out fluctuations??)
Therefore total pressure - static pressure = Dynamic pressure. Tada I should be able to get velocity and mass flow rate into my engine??

Am I crazy??
Hopefully from these results I can verify WAVE/Vectis models and have some pretty experimental graphs that people can ooh and aah over?

[Dunkster]

Hi guys
My first post so please laugh at me as much as you like.

I'm going to be carrying out improvements to our engine test rig next year. I was thinking of a cheap way to measure VE without having to go about modifying the intake manifold to much. Here is my idea please tell me if you think it is worth continuing my train of thought.

Instead of drilling holes etc into the intake manifold you fashion a tube out of pvc or something which can fit over the bellend of the throttle and give a good seal. Making the pipe 250mm long should give a nice smooth flow across its cross section. Now because total pressure is atmospheric, can I assume that down my pipe I have very negligable head loss compared to the rest of the intake manifold. So i can simply measure static pressure with a simple preassure transducer. (low pass filter to average out fluctuations??)
Therefore total pressure - static pressure = Dynamic pressure. Tada I should be able to get velocity and mass flow rate into my engine??

Am I crazy??
Hopefully from these results I can verify WAVE/Vectis models and have some pretty experimental graphs that people can ooh and aah over?

[mk e]

Well yes.....but the problem is that if you have enough pressure drop in your tube to measure you have enough pressure drop to alter the engine's performance and it's VE. High VE engines are VERY sensitive to pretty much everything.

Here's a better and easier way. Measure the fuel flow rate then look at the AFR off the O2 sensor, plug in the fuel flow rate and out come the mass air flow rate without disturbing the intake or exhaust gas flow streams, and your engine's performance along with it.

I see WAVE is the preferred modeling software but it came after my FSAE days so I haven't messed with it but it sounds impressively powerful. I use Dymomation5 which is specifically design for high performance engines and seems to do a really nice job. On the engines I've built and tested it hits the numbers within 1-2% every time. I model it, design my cams, design the intake and exhaust (burns stainless is FANTASTIC at modeling exhaust and it's a free service), set my cams then use the ignition and fuel numbers to build the ECU maps and the engine does what it's supposed to do and requires very little actual dyno tuning (I have a speard sheet that calculate all the low power fuel based off the high power dynomation results). It's a beautiful thing.

[Dunkster]

The pressure drop I measure is just the reduction in pressure due to an increase in velocity. The pressure is regained (mostly)as soon as the fluid stagnates i think.

WE measured the flow rate of our injectors and i think it came out around 195cc/min at 50psi. Would I just read off the pulse width from the ECU output multiply it by 195cc/min, fuel density and afr to give me mass of air??

How sensitive do you think this kind of experiment is to battery voltage and fuel pressure. The fuel pressure gauge we have on our reg is heavily damped and doesnt fluctuate very much. Is this a good representation of fuel pressure or is it bouncing up and down wildly in the rail?

Cheers for your reply

[Dunkster]

reduction in *static*!! pressure sorry

[mk e]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Dunkster:
The pressure drop I measure is just the reduction in pressure due to an increase in velocity. The pressure is regained (mostly)as soon as the fluid stagnates i think. </div></BLOCKQUOTE>

In theory what you're saying is right, but it's way harder in practice. To get a pressure change that you can actually measure you need to generate a pretty high velocity....I'd guess you'll want to be no more than about a 50 or 60mm tube ID then once oyu have the air moving you need to slow it back down without losing any energy so a venturi and you'll get to what 90+%, but that's not 100%.

You might/should be able to get a good reading by putting your pressure tap at you flow restrictor so you aren't adding another restriction or additional tuning or anything else to the system.


<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">
WE measured the flow rate of our injectors and i think it came out around 195cc/min at 50psi. Would I just read off the pulse width from the ECU output multiply it by 195cc/min, fuel density and afr to give me mass of air??

How sensitive do you think this kind of experiment is to battery voltage and fuel pressure. The fuel pressure gauge we have on our reg is heavily damped and doesnt fluctuate very much. Is this a good representation of fuel pressure or is it bouncing up and down wildly in the rail?

Cheers for your reply </div></BLOCKQUOTE>

Again, in theory you can use the injector times but there is a response (or dead) time (that is EXTREMELY dependent on V_Batt) and the flow isn't actually linear, there is generally a slight knee in the curve so you'd have to fully map the injector flow before you could trust it.


There best thing to do is put a flow meter in and meter the real flow.

There is some good injector info here:
http://www.injectordynamics.com/tech.html

[Kirk Feldkamp]

If you go the fuel flow and AFR route, it's probably going to be more accurate to do a direct measurement of the fuel flow. Floscan make a great little inexpensive ($110) fuel flow sensor. http://www.floscan.com/html/blue/accessories.php The 20B is great for a FSAE setup. Don't forget to think about how/where to plumb it with the fuel system (think about what the pressure regulator is doing). They're cheap enough that I'd also put one in the car so you can stop guessing how much fuel you're using in the car under actual driving conditions. In a test cell setting, it could also be enlightening to put an air mass flow meter onto the intake inlet (before the throttle) to confirm and correlate what you're seeing with the fuel flow and lambda (AFR) sensors. In an R&D environment, this may be a smarter approach as it's a direct measurement of the airflow into the engine, rather than a combination of two indirect (potentially higher error) measurements.

At this point there should probably be a discussion about what you're actually defining as VE. It's usually best to define it as the volumetric efficiency with respect to manifold conditions. This will have a major impact in how you measure and calculate it on a restricted (or boosted) engine. This should also tip you off to where you may or may not want to go after targeted gains. For instance, if you're showing poor VE with respect to manifold conditions, you would want to look at things like your intake/exhaust runner lengths and diameters. Alternatively, if you're showing good VE numbers but low manifold pressures, you would probably want to look at your plenum sizing, and/or restrictor/diffuser/manifold geometry.

I played with the Dynomation products a bit back in the day, and I don't know if it really has the capabilities to do what you want it to do. The Ricardo WAVE line of products is a much more technically capable simulation, and I would strongly suggest talking to them about some licenses for your program. This will also be useful tool if you want to continue your engine design career after you finish school. Dynomation is more for your bolt-on small block Chevy crowd. No matter what you do, you're going to need to be able to generate quality dyno data to correlate and refine your simulations. Without closing the loop, the simulations aren't going to be super useful. They may help to understand trends, but dialing in on exact sizing details may prove deceiving.

-Kirk

[Pete Marsh]

Get a regular hot wire AFM from a wrecker, calibrate on a flow bench to suit your DAQ, and you're good to go.

Pete

[mk e]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Pete Marsh:
Get a regular hot wire AFM from a wrecker, calibrate on a flow bench to suit your DAQ, and you're good to go.

Pete </div></BLOCKQUOTE>

Yuu can do that to calibrate the fuel flow/AFR as Kirt suggest but you really need to remove it to do get real HP numbers. Maybe if you select a relatively large MAF knowing that it can't measure the low flow condition you'd be close at a true full power result but generally having anything but the real intake with the real air-cleaner on top gives a bad answer.

[mk e]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">

I played with the Dynomation products a bit back in the day, and I don't know if it really has the capabilities to do what you want it to do. The Ricardo WAVE line of products is a much more technically capable simulation, and I would strongly suggest talking to them about some licenses for your program. This will also be useful tool if you want to continue your engine design career after you finish school. Dynomation is more for your bolt-on small block Chevy crowd. No matter what you do, you're going to need to be able to generate quality dyno data to correlate and refine your simulations. Without closing the loop, the simulations aren't going to be super useful. They may help to understand trends, but dialing in on exact sizing details may prove deceiving.

-Kirk </div></BLOCKQUOTE>

Now you're going to make me spend a bunch more money http://fsae.com/groupee_common/emoticons/icon_frown.gif

I'll have to say though that I've been really happy with dynomation5. DynoSim, desk top dyno, etc are very much "bolt-on" and just give an idea of what to expect but dynomation seems quite capable, at least within the narrow design widow of "I want to make lots of hp" and is an iterative wave based simulation. I play primarily with 70s-80s Ferraris (naturally aspirated and boosted) and dynomation5 has been spot on.

From what I can tell it does have a LOT of empirical data coded into it. The wave only simulation works well on intake and exhaust design (not as good as the magic burns stainless works, but the burns result do confirm in dynomation), but does not yield an accurate HP estimate like the "hybrid" mode does which is where all the empirical corrections get pulled in.

[Kirk Feldkamp]

I've heard that many teams get student licenses of WAVE from Ricardo. Anyone care to chime in?

My point is that I don't think the Dynomation line of software is not going to take into account the plenum and restrictor effects that you will see with a FSAE engine. IIRC, Dynomation assumes a constant inlet pressure and goes from there. VE is a volumetric measurement, so the mass flow of the air is dependent on the state within the manifold. Your lambda/AFR sensor is a mass-based measurement, so you better know what's going on up in the manifold if you want to properly calculate the VE. If you've got a big open airbox feeding the engine, that's one thing... it's an entirely different thing to put a restrictor on an engine and have it drawn down and eventually choke. Unless I'm mistaken, the Dynomation products aren't going to give you this sort of input flexibility. I'm sure it's fine for many street-based performance applications, but if you're trying to do things "right" for FSAE, I don't think it's the path to go down.

Frankly, I think other than learning about how to work with and develop sims, most engine development in FSAE could be done quicker and better on the dyno or in a car. There is an inordinate amount of mental masturbation that goes on every year when the new engine guy thinks he's going to come up with God's gift to FSAE engines. This is reinvention of the wheel at its finest. I've seen a LOT of teams over the years that were in the ballpark with all of their hardware, but had absolutely no clue about how to calibrate fuel/ignition. If teams stopped running on the hamster wheel of making more power with new hardware and instead focused on tuning, drivability, and reliability, then I think many more teams would be going faster and finish more events, thus scoring more points.

Get it running early, make it drivable, and make it bulletproof!

[Jon Burford]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Get it running early, make it drivable, and make it bulletproof! </div></BLOCKQUOTE>
Agree strongly.

[mk e]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kirk Feldkamp:
I've heard that many teams get student licenses of WAVE from Ricardo. Anyone care to chime in?

My point is that I don't think the Dynomation line of software is not going to take into account the plenum and restrictor effects that you will see with a FSAE engine. IIRC, Dynomation assumes a constant inlet pressure and goes from there. VE is a volumetric measurement, so the mass flow of the air is dependent on the state within the manifold. Your lambda/AFR sensor is a mass-based measurement, so you better know what's going on up in the manifold if you want to properly calculate the VE. If you've got a big open airbox feeding the engine, that's one thing... it's an entirely different thing to put a restrictor on an engine and have it drawn down and eventually choke. Unless I'm mistaken, the Dynomation products aren't going to give you this sort of input flexibility. I'm sure it's fine for many street-based performance applications, but if you're trying to do things "right" for FSAE, I don't think it's the path to go down. </div></BLOCKQUOTE>

I agree that from what I read WAVE is probably better....but dynomation5 seems to handle a flow restrictor fine. I just took a simulation of a 145hp engine,threw on a 20mm restrictor and it popped out 74hp with the intake pressure at around 70kpa which is about what I'd expect and also exactly what the FSAE car I worked on years ago produced. So it seems to handle this condition correctly. It is showing a bit of instability in the intake track, but I'm not sure that's a mistake since the sim conditions are a tad unbalanced.


<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">
Frankly, I think other than learning about how to work with and develop sims, most engine development in FSAE could be done quicker and better on the dyno or in a car. There is an inordinate amount of mental masturbation that goes on every year when the new engine guy thinks he's going to come up with God's gift to FSAE engines. This is reinvention of the wheel at its finest. I've seen a LOT of teams over the years that were in the ballpark with all of their hardware, but had absolutely no clue about how to calibrate fuel/ignition. If teams stopped running on the hamster wheel of making more power with new hardware and instead focused on tuning, drivability, and reliability, then I think many more teams would be going faster and finish more events, thus scoring more points.

Get it running early, make it drivable, and make it bulletproof! </div></BLOCKQUOTE>

I mostly agree with this point. You do need a well designed restrictor but that is simple math not a simulation. We reversed ours on the dyno just to see and hp went from 74 to 52 or something like that so this matters.

There is some benefit to having a decent intake and exhaust design for the rpm the engine is actually going to work at with the restrictor in place, but getting the think properly tuned is by far the most important.

[Dunkster]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> I've heard that many teams get student licenses of WAVE from Ricardo. Anyone care to chime in? </div></BLOCKQUOTE>

I am pretty sure most uni's could easily get it free. From what I hear they are quite good at supporting unis.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Frankly, I think other than learning about how to work with and develop sims, most engine development in FSAE could be done quicker and better on the dyno or in a car. There is an inordinate amount of mental masturbation that goes on every year when the new engine guy thinks he's going to come up with God's gift to FSAE engines. This is reinvention of the wheel at its finest. I've seen a LOT of teams over the years that were in the ballpark with all of their hardware, but had absolutely no clue about how to calibrate fuel/ignition. If teams stopped running on the hamster wheel of making more power with new hardware and instead focused on tuning, drivability, and reliability, then I think many more teams would be going faster and finish more events, thus scoring more points.
</div></BLOCKQUOTE>

hear hear. The WAVE model that somone developed last year for the team is a waste of space. The restrictor doesnt choke (only reaches Mach 0.8 at 15000rpm on a 610cc 4 pot) which i hear is a common problem with WAVE. WE have never had any capability what so ever to judge the performance of our intakes/exhaust except through torque and power which is sensitive to many other things. Especially when the map changes year to year. It doenst help that the crappy water dyno we have doesnt give enough brake torque to brake the engine so I need to stick an overdrive box between it and the engine before I can do anything.

I'm not trying to reinvent any wheels or masturbate with anything. I just need the basic ways to measure engine performance on a proper rig cheaply.

I already wired up and started our cbr 600 with our Vipec V88 and its been tested in our old CAR. Its my final year disertation to judge engine performance enhancements for the engine, which is going to be focused on:
MAking bits and bobs lighter
and
CAMS
Intake
Exhaust
so basically VE.

I like your idea of VE wrt Manifold conditions. That isolates the performance curve to Cam, intake and exhaust things. Although I dont see any difference in measuring it??? Surely I can just get Map and iat to give me density of the air in the plenum with the ideal gas law?

Anyone ever got pressure plots against crank angle in a runner close to the valves before???
I know run before I can walk!!
Thanks for your replys

[mk e]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">The WAVE model that somone developed last year for the team is a waste of space. The restrictor doesnt choke (only reaches Mach 0.8 at 15000rpm on a 610cc 4 pot) which i hear is a common problem with WAVE. WE have never had any capability what so ever to judge the performance of our intakes/exhaust except through torque and power which is sensitive to many other things. </div></BLOCKQUOTE>

There is a lot of stuff in this paragraph.

0.8 mach at the restrictor sounds about right to me.....you can't get much high because as you try ti increase the manifold vacuum you are also effectively reduce the compression ratio (you've expanded the air before you compress it) and you've also defeated any positive pressure waves in the intake and exhaust systems by running so far below ambient pressure. 74-75 hp is a bout the limit for a naturally aspirated engine with a 20mm restrictor I think. You can get a bit more with an turbo but not a lot more.

The only good way I've ever found to compare manifold and exhaust is same day dyno testing and you have to run each at least twice, 3 times in random order is better.

When you have a lot of factors and you are trying to isolate the effect of just a few you NEED a DOE. There simply is no other way. When you have only 2 options the DOE is automatically a "full factorial" but you still need replicates before the result mean anything. A replicate is very different from a repeat (which you should also have).

Repeat means you take multiple readings on the same set-up.
Replicate means you tear it down, then set up the next test condition.

Now, if you are testing 4 intakes and 4 exhausts a full factorial would mean 16 runs, with 3 replicates and you've got 48 runs to make. You can do a 1/2 factorial DOE and cut that in half, get p values to know if what you're seeing is significant of just noise in the testing and KNOW you've made the best choice.....I know.....I hate statistics too but sometimes it's the only way http://fsae.com/groupee_common/emoticons/icon_frown.gif

[Pete Marsh]

@ Dunkster
I would recomend you keep track of, and think about how, you are going to present this work to the design Judges. I think they like to see the simulation and intelectual masterbation A LOT.

I have just come off a year that took a 610cc 4 from about 30HP and running out of fuel 15Km into enduro, to enough power to win Accel and AutoX and also win Fuel! (2.9L)I started with a dead engine dyno and a waste of space WAVE model, and set about doing pretty much the same thing as you.
As Kirk says, the basic hardware was not the problem, and there is plenty of well documented tests and trails of various ideas. What was missing was a good execution of any of it.

Sounds ok? My design event comment -
"Very high knowledge but lacked engineering process"

I did explain where I started the year and how I decide to achieve the goal of a good PT package, and the mods that were chosen to be used and where they came from.

Without a WAVE model good enough to convince the Judges, and dyno verification to go with it, I would start thinking about how you are going to show your "engineering Process" now.

Pete

[Kirk Feldkamp]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Pete Marsh:
Without a WAVE model good enough to convince the Judges, and dyno verification to go with it, I would start thinking about how you are going to show your "engineering Process" now. </div></BLOCKQUOTE>

Realistically, how many points did your team lose for not "showing your engineering process?" Think about how many points you gained by actually producing a kickass drivetrain package that competed strongly in the relatively valuable dynamic events. In my opinion, the design event is a good thing for students to experience because it's a good preparation for defending/selling designs once you're out in the "real world." Unfortunately, I think far too many teams get caught up in pandering to the smaller amount of points they're not securing in the relatively invaluable design event. Dedicating the necessary resources throughout the year to demonstrate "proper engineering process and documentation" are really not worth it if you look at it this way. This is also why the big corporations I've worked for in the past miss deadlines and overrun budgets... they're far too focused on the process than the results!

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Dunkster:
It doenst help that the crappy water dyno we have doesnt give enough brake torque to brake the engine so I need to stick an overdrive box between it and the engine before I can do anything. </div></BLOCKQUOTE>

Are you coupling directly to the countershaft, or do you have a chain drive with a sprocket ratio in between? What gear are you making your pulls in? If you're having trouble with absorber torque capacity, you should be in 6th gear and be 1:1 with the countershaft out of the trans. Even the smallest water brakes I've seen would be more than capable of handling the torque output of a FSAE engine under those conditions.

There was a project I was very loosely involved with a couple years ago that was trying to make BIG power with a turbo 600 for SCCA road racing. The tuner was thrashing on the dyno for a few days and the thing just wouldn't make the power he was expecting. After some questioning, it was apparent that he was trying to make power pulls in 3rd or 4th. This was also on a water brake. Once he was advised to put it in 6th and try it again, all of a sudden the thing started to make some serious juice. Be aware that the RPM rate that you make sweeps at will have an effect on the indicated torque readings. If you want to see this in action, load the engine to a steady state condition at some mid range RPM and medium load (say 50% throttle) condition. Then, take the load valve and quickly jack some load into the engine. If you log the torque output, you will likely see a spike in the output. This is called a "torque flash". You can play all sorts of games to make the dyno indicate high or low using techniques like this. You will also usually see differences in the indicated lambda for the same conditions but different RPM rates. This is why your RPM rate on the dyno should be close to that of in the car if you want to do your fuel calibration on the dyno.

That said, if your intake/exhaust hardware is in the right ballpark, you can "street" tune an entire map from scratch with about 4 hours and a long, flat, straight, vacant area. If you do it right, this will give you very realistic RPM rates across a range of conditions. People like to say the ONLY proper way to tune a car is on the dyno. Hell, I used to think this too... until I had to tune a few bikes/cars like this out of necessity. Now, unless I'm doing some serious back to back hardware testing, I will do this almost exclusively. When dyno time actually costs real money, you start to think about how "necessary" certain methods are. If you can get 95% of the way there with 10% of the effort, you better be damn sure you need that extra 5% to be competitive! I'd take the hours you save and put them into driver training. You will almost certainly net more points at comp versus working ad nauseum on the dyno. Choose some realistic lambda numbers for your lambda map and just tune everything to that. If you want to go more aggressive, you probably can. There aren't a whole lot of ways to blow up a FSAE 600 due to tuning unless you're way off in the weeds on the calibration. These engines can and do run *super* lean in the original application. The combustion chamber designs tend to be very forgiving. Furthermore, FSAE tracks do not present long, sustained loading like you'd normally see in a race car... so the heat loading is actually pretty low. Lots of off-throttle and quick transients mean you can go pretty lean without too many issues.

But don't take my word for it, these guys know a thing or two!: Motec Newsletter (http://www.motec.com.au/filedownload.php/30JUNE2007.pdf?docid=2639) A quick throttle histogram should tell you which box you're in.

[mk e]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kirk Feldkamp:

Realistically, how many points did your team lose for not "showing your engineering process?" Think about how many points you gained by actually producing a kickass drivetrain package that competed strongly in the relatively valuable dynamic events. </div></BLOCKQUOTE>

Good advice. The year I went we had 4 people on the team. My college had only sent a car once about 5 years earlier that failed to complete a single event so we had basically less than nothing to build on which gave us exactly zero resources to devote to anything except getting the care working....but the car worked pretty well. I think we finished 17th or something like that overall, with a 50-60 place (out of like 110?) in the design comp.

95% of the tuning was done in the parking lot with the total dyno time of about 3 hours. Dynojet had a little dyno shot-out the year we were there....we came in second by something like 0.2 hp

Basically the only prep we did for the design competition was show up because there was just no way to justify spending any time for such a small potential points gain. To win you have to do well in everything, but with limited resources you need to pick your battles and a running car lets you be in the battle, a really pretty design report doesn't.

[Dunkster]

THx so much for your replys your being very helpfull.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Are you coupling directly to the countershaft, or do you have a chain drive with a sprocket ratio in between? What gear are you making your pulls in? If you're having trouble with absorber torque capacity, you should be in 6th gear and be 1:1 with the countershaft out of the trans. Even the smallest water brakes I've seen would be more than capable of handling the torque output of a FSAE engine under those conditions. </div></BLOCKQUOTE>

Its is a land and sea dyno designed for a outboard motor. So in realilty it would go straight on the prop shaft which i assume turn at near crank shaft speed because we are going to have pretty much gear up the dyno to nullify the primary reduction and reduction of 4th gear. http://www.land-and-sea.com/pr...dyno/marine-dyno.htm (http://www.land-and-sea.com/prop-shaft-dyno/marine-dyno.htm)

Lukily we get free dyno runs on the rolling road at our local tuning garage. THey are quite helpful and i am intending to milk them like dairy cows.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> you can "street" tune an entire map from scratch with about 4 hours and a long, flat, straight, vacant area </div></BLOCKQUOTE>

I have already set up our ECU to log lambda so we should be able to do it. The Vipec Ecu we started using should be able to log engine diagnostic stuff for the entire endurance event without a problem. Its quite good actually you can click on a point on your log plot and in the tuning tables there is a cross hair telling you where on the ignition or fuel map you are. Should make it really intuitive.


<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> The technique suggested is good but, it may not cut significantly in expenses.
</div></BLOCKQUOTE>

The main reason for trying my pressure transducer route was that I can get suitable transducers for about 10 pounds. And they respond fast enough to give me good fourier transforms of the pressure trace inside our plenum.

[Kirk Feldkamp]

A rolling road is basically the same thing as the method I suggested. Be careful with a car-sized rolling road, as you can really overwork an engine if your RPM rate is too slow. Just be aware of this and use an appropriate gear to make your pulls. If it's an ATV/kart rolling road, then you're golden.

Why 4th gear? You've got a 6th! It clearly states that the absorber can take 400hp, and these engines don't make a ton of torque compared to, well, anything. The primary reduction isn't that big! Under what conditions (throttle and RPM) are you seeing it unable to hold the engine? Also, the load water brakes generate is very dependent on the water flow into the brake. What is your inlet pressure to the load valve? How much flow is the inlet water pump capable of supplying at that pressure?

[Dunkster]

We have removed 5th and 6th and lightened various other parts othe gearbox on the engine.

I believe we have the 9" dyno which is quite small.

http://www.land-and-sea.com/pw...dyno-load-charts.htm (http://www.land-and-sea.com/pwc-dyno/pwc-dyno-load-charts.htm)

As you can see with the load chart above. A fsa with say 50nm of torque at 6000rpm. would be 2000rpm and 150nm or torque on the dyno if you put it through 4th gear (something like that. Gear ratio is a ball park figure because i dont have the information at hand). The dyno will produce enough torque no matter what I do. Therefore the overdrive.

In terms of the rolling road we have 15" steel rims with cheep tyres on so it should be fine for the dyno in that respect.