The restrictor has to be before everything but the throttle. And it's 1 restrictor for the entire intake system, but any/all air that may feed the engine has to go through the restrictor. Any kind of forced induction has to be done post restrictor. You can do whatever you want with the intake (material, plenum volume, length, etc, etc, etc are all open, but if you have something extremely unique, you better be able to explain it to the design judges in the design review portion of the competition) and exhaust, as long as all of your incoming air comes through that restrictor.

I agree with you about the built motors being far less reliable. It seems like (from my research on the YFZ forums) that most of the guys running built motors are doing so for ~1/8 mile drags and are running high compression/race gas, which we cannot do. Something will need to be done about the compression ratio. I believe the stock ratio for the engine we're using is around 11.5-12 ish. What the ideal ratio is, I have no idea. I would need to use something like WAVE to model the engine and guess at boost pressures and all that fun stuff to try to pick an "optimal" compression ratio. Then (if we were really ballsy, which my team doesn't seem to be) we could have a piston (or a handful) custom machined to our specs and run them instead of the stocker. With a single, this becomes much more of an option, but we'd have to get the bottom end rotationally balanced, which would add more money to our engine development than I think people would be willing to spend. Now we're back to the spacer since it's the cheap (although less than ideal) way to drop compression ratio in the engine.

As for total power output with the engine, I think if we could get to the 75-80 range and still be very reliable, that would be amazing. How possible that is, I have no idea. I think it would take a lot of time on the dyno getting everything dialed in just right in order for it to work properly with the type of throttle response and reliability we're looking for, but that's something that's completely possible thanks to the in-house dyno.

 

Something I have also thought about is if you ran a similar sized engine but multi cylinder maybe like a 500 twin the smaller displacement per cylinder as long as the compression stroke was on opposing strokes would make the restrictor a little less of an issue... Just a thought. Then run a 2 into 1 exhaust into the turbo. You could even run say a Mega Squirt so you could have EFI? There is a build thread on here somewhere a guy built an old 2 cylinder Yamaha single turbo with EFI, I will try and find it. I know it kinda gets away from the subject but its fun to think about other options.

 

I think the 2 cylinder is the way to go as well, but for whatever reason, the team wants to go to a single. Aprillia has a side by side twin that's really the ideal engine for this competition (in both my eyes and another teammates) but they're extremely expensive and hard to come by. Another thing the twin helps with is the exhaust pulsing. With a single, there's likely to be significant exhaust pulsing, whereas with a twin, firing 180 degrees out of phase with each other, there's no pulsing.

As for EFI, we have a Performance Electronics EDGE ECU and run EFI already. Whether or not we stay with PE is up in the air (they're local, but our team was rather frustrated with the service they provided last year and especially at competition) but that is the system we've been running, and will probably continue to run for the foreseeable future.

If you could find that build thread, that would be awesome info to look through. I would really appreciate it.

 

here it is. Its a 650 but oh well. https://www.theturboforums.com/smf/index.php?topic=147520.0

Have you ever looked into a Mega Squirt? They are pretty cool, and cheap. I have one in my Chevy truck. There are other twins out there that would work. If you had an air cooled motor you would save some weight there too.

As for the pistons, I think JE can build pistons to your specs that are the same weight as stock so you wouldnt have to balance the rotating assembly.

Or how about a Honda 400ex motor, they are single cylinder and have dual exit exhaust and make 1 pipe longer then the other? But they arent know for there big power output either.

 

That's a pretty sick build. I just looked through it briefly (got a nice big homework assignment due tomorrow that I haven't started and I'm putting it off and killing time being on the forums) but I'll definitely take a more in depth look at it at some point.

The info about JE is good to know. That would be very helpful if we could send them a stock piston, and get a lower compression one back. I'd think something in the 10-10.5 range would be much more ideal for the boost, but again, I'd have to run some kind of simulation/calculations to know for sure.

My first year of college I was on an Efficient Vehicles team, and we ran a Mega Squirt controlling spark and fuel on an injected 25cc Honda engine. I'm not sure if it was just the old box or what, but that thing was a piece of garbage. I hated it, from the little experience I had with it. And nobody else on the team liked it much more.

The dual exit exhaust is something to think about. I don't think having the runners 2 different lengths would be a good idea (seems like you would have unequal flow through each leg of the exhaust) but I would think you could create better flow overall to a plenum and then to the turbo. Something to keep in mind, I guess.

 

I know tons of people run the MS. Mine is a MS2 version 3.0. I think they are better then they used to be. I got mine from DIYAUTOTUNE.com, they have them preassembled or build yourself.
What year yzf450 motor do you plan on running?

 

Ya I was just joking with the Banshee, although it would be cool. The aprilla engine whould be perfect for the build they have a 500cc that puts out 70+hp they use in there duel sport but like you say big $. I like the idea of the 450 yami but I think it would be pretty hard to make up the extra hp even given the weight savings. Tourqe would be down a little as well although those little singles do put up good tq numbers to get you moving. What weight would you be aiming for and how much did the 600cc machine weigh? Any chance of just boosting the existing engine I would think a sportbike inline 4 would be hard to beat hp/LB.

 

That's kinda what I've thought/heard about MS. A buddy of mine is going to run one in his V8 swapped RX7, and he highly recommended one to me as well. I guess it'll be something to look into and compare features once the team really gets geared up and running for next season (whenever that will be).

I believe we're getting a ~04 YFZ450 engine, that started life carbed and then adding all the goodies to run it fuel injected.

Turbo5point0, I believe our end goal weight is between 350 and 375 lbs dry weight for our entire car. We're changing from 13" wheels to 10" wheels, which allows smaller uprights, and we can run smaller brakes, etc. The current car weighs 466lbs dry at competition, with the RR engine being around 120lbs or so with the dry sump installed. From what little experience we have with the engine, we're thinking just the swap from 600 to 450 will save us around 60lbs.

As for boosting the 600, I highly doubt that would be possible. There are teams that do it (Cornell in particular is one that comes to mind, making 107hp and dominating the acceleration competition running in 1 gear, 2nd, with no launch control or anything) but our faculty adviser and some of the judges at competition have hinted that we should go to a single. Besides, there's a possible rule change that would allow us to run a shorter wheelbase, and that would not be possible at all with the 600. The packaging is already a nightmare with a 61" wheelbase (60" minimum), let alone if we were allowed to shrink it to 55" like the possible new rules state.

 

Related to compression, the 2000-2007 Hayabusa has 11-1 comp. ratio. We run a .080 cylinder spacer to lower the comp. to about 8.5-1. Then we can run about 10-12lbs if boost on 93 octane with no intercooler or water. People do warn not to do long top out runs because of heat build up could cause detenation.

One way around turbo lag is to slip the clutch. An auto clutch is sold for woods/Harescramble racing. It uses balls to lock with increase in rpm. It works very well and it makes gearing a lot less important.


Mark

 

The spacer is what I would do as well. Cheap and easy. It works very well too. I know many guys that run them on turbo Busas.

 

But there are several ways to counteract that detonation, correct? The least of which (in our case) being running E85. We can also dial back the timing to help prevent that. We have a rough idea of the longest period of time that the car should be running at competition, and we can tune to get the most possible power for that period of time (again, we'll have to test this on the dyno) to prove the concept, but I guess there's a way to monitor detonation with a sensor on the exhaust. The University of Melbourne mentioned the sensor and what they used to monitor the their anti-detonation setup in the paper I have.

As for slipping the clutch, we run an air shifter to decrease the amount of time spent shifting over several laps. Would the auto clutch you're talking about still work with an air shifter?

 

If you are running E85 you will be able to run a lot higher comp. ratio and boost levels because it is 105 octane. Spark timing and fuel enrichment will help but, I would have to refer to the car guys for info on that.

The auto clutch locks like a normal clutch once it is above your set rpm but, you can still use the clutch lever if needed. Most air shifters use a spark or spark/fuel engine cut to unload the transmission to allow shifting. Another way to shift is to momentarily cut the throttle back to unload the transmission.

Mark

 

We basically make the entire shifting setup from scratch, and use the spark cut method to allow for the shifting. That auto clutch sounds like a decent idea. The one problem I see with cutting the throttle would be a drop in mass flow through the engine, which would clower the boost level, correct?

 

Yes, you are correct. Anytime throttle is reduced, exhaust output is also reduced. For street riding it is not an issue but, for all out performance it could cost you some acceleration. On the 4 cylinder bikes, 80ms spark cut is usually good enough to allow shifting in most any gear except when the tires are slipping excessively.

Mark

 

Now the million dollar question, can the higher resistance to detonation of the E85 (and therefore higher compression) overcome the 1mm smaller diameter restrictor?

 

1mm is about a 10% decrease in cross sectional area. Thats a big deal. You also have to remember that e85 runs a much richer stoich ratio which means the fuel will be displacing even more air so you'll be losing some significant air volume. On the other hane I'd say that the increase in max boost will more than make up for it. But thats just my GUESS. You'd have to run some numbers to see if the boost increase allowed based on the increase in octane would make it worth while. I don't know if they have a different fuel MPG factor for teams running e85 so you'll have to consider that too for your MPG comparisons. E85 runs about 10-1 F/A ratio compared to gas 14-1 F/A ration stoich.

 

Yes, they do. You calculate mileage points exactly like the regular gas teams do, then multiply that number by 1.4. Makes up for the difference in stoich ratios.

 

Any other thoughts on whether or not E85 is worth looking into with the 1mm smaller restrictor, but ability to run higher compression ratio?

 

I think the E85 is the way to go. And in my opinion I wouldnt use it to run higher compression, I would use it to run more boost. Which yes I understand its basically the same thing, but boost is compression you can lower by turning a knob on a boost controller.

 

In order to make the 70-80 hp we're trying to make, it looks like we're going to have to be running up near 10-15psi of boost as is. This seems like a lot to me (maybe I'm wrong on this one, just a gut feeling), based on the engine size. The more boost idea gets us closer to the power, but could also mean more lag, correct? I just plotted some points on the Squirrel Performance calculator using the GT1241 and guessing at some of the powerband info (I've seen a stock engine dyno with the 20mm restrictor but no tuning, so I have an idea where some of the points are) and the graph looks much better than the last time I'd messed with it (all points inside the 70% efficiency curve, rather than 2-3 being to the left of the surge line). I believe we have a GT1241 sitting around somewhere, and seeing the points on the compressor plot makes me think this turbo may work much better than I had been thinking.

And my thinking with higher compression is that if we don't have to mess with the stock piston/rod/crank, that would be ideal. This means a smaller head spacer, which would be more ideal, correct?