Turbo...Question about the rules

[rjb2968]

Good day All,
I was reading through the 16 rules and stumbled across the compressor section and have a couple questions I was hoping that someone can answer. The first one being the placement of all the components, I have seen the picture but want to make sure I get this right....

1) Restrictor
2)Turbo
3)Throttle body
4)Optional intercooler
5)Charge pipe to engine

The second question I have is about this rule IC 1.7.4

"Plenums anywhere upstream of the throttle body are prohibited. For the purpose of definition, a “plenum” is any tank or volume that is a significant enlargement of the normal intake runner system. Teams are encouraged to submit their designs to the Rules Committee for review prior to competition if the legality of their proposed system is in doubt"

I am wondering how on earth is someone supposed to turbo a 4 cylinder engine? There has to be some sort of log plenum that is MPFI style that has one inlet so that the charge pipe connects to.... Or are you supposed to create an "Intake header" type manifold.

Anyways I was hoping that someone could answer these questions with picture examples or something very clear so I can wrap my head around this.


Thank you for your time.

[Jay Lawrence]

When I was involved, you had to have the restrictor and throttle body before the turbo, which created issues (such as sucking oil through the turbo into the intake off-throttle). I believe this is changed now, as per your 1-5.

For the second question: yes, you pretty much have to have some kind of plenum with a charge pipe connected. So the order is something like: Air filter - Restrictor - Turbo - Throttle Body - Intercooler (in reality only optional if you're running E85) - Charge pipe - Plenum - Head. As for fuelling, there's nothing wrong with keeping the factory bike injector location, but if you're running E85 you could think about a secondary spray injector in the plenum.

As always, if you want to be properly sure, write to the rules committee

[Claude Rouelle]

And who are you? Simple courtesy to introduce yourself? Not necessary?

[rjb2968]

Sorry Mr.Roulle while I do greatly respect your work and all you have done for the racing community I do not feel comfortable revealing my identity. The reason being is that with facebook these days anyone will be able to find me instantly.

Jay, thanks for answering that.... So there pretty much HAS to be a plenum as I thought... that rule is really bothering me. I cant understand what it means in terms of 4 cylinders.

Thanks again

[Claude Rouelle]

So ?

Anyone can find me easily too.... How can you have an opinion or a question and not the guts to present and/or defend it? You would, I imagine, introduce yourself in a public face to face meeting, no? What is the difference on the internet? What do you have to hide or protect that is so important?

[Menisk]

Why the hell should you care who he is? If he has an interesting question and you feel you can contribute to his learning, then help. If not, bugger off. Way too many of your posts to this forum are you bullying newcomers to tell you who they are. Do you have a post count where you deem it acceptable for someone to stop introducing themselves? Do you feel like knowing who he is and where he comes from is going to change the course of this discussion for the better? Do you know or care who I am without going back through my post history to connect the dots. Leave him alone and work by the rule of, "If you don't have anything nice to say, don't say anything at all."

This is not a written rule of this forum and you and Pat Clarke need to stop trying to enforce it like it is.

[Menisk]

In response to your question rjb2968, they're trying to avoid a situation where people make a massive chamber they can boost up before the throttle to essentially have a boost reserve.

You can have as much plenum as you like after the throttle and this rule shouldn't make designing a turbo 4-cylinder any trouble. I think you're getting caught up on the placement of the stock throttles on the bike. You're only meant to run a single throttle on these cars rather than the ITBs the manufacturer runs on the bike.

I think the better question for you at the moment is why you're choosing to run a turbo. My team has a car with a 60% rear weight bias (very uncommon in this competition) that puts power down far better than the vast majority of cars and our N/A 4 cylinder still has too much power. Maybe you're chasing efficiency gains, maybe you're just doing it because it's an interesting thing to learn about (perfectly good reason). Just make sure you have a good think about whether you want the added complication and headaches as well as how you intend to justify your decision come the design event.

[Bemo]

While I don't care that much as Claude and Pat about people introducing themselves, I'll never understand what the big deal is introducing yourself. What are you afraid of when people know you're asking questions about a turbo?

But to come back to topic. Regarding the plenum the keyword is "upstream of the trottle body". The rule doesn't say anything about plenums downstream of the throttle body, which means you can build an as large plenum as you want. Of course this means, you can't use the original throttle body, but with an N/A 4 cyl. this would be the case, too.

[rjb2968]

Ok sorry I'll introduce my self, I did not realize that with people with such caliber as Mr.Rouelle who has dedicated his life to the online cyberbullying of college students who wish to remain anonymous. Perhaps if I buy optimumassmatics you will respect me more.

Hi my name is Bill Cosby and I am from 1985.

The reason we are looking at using a turbo is because we want to focus on making low end torque over large power and we also believe that the efficiency gained will also help us perform better in fuel. Thanks for answering that Menisk and having my back in the battle field over there, you did answer my question I seemed to have completely read over the "Upstream" portion.

-Bill

[woodmandan2]

You could have picked a less controversial public figure to impersonate...

[MHybrid Josh]

FWIW some teams are very protective of information and like to keep to themselves rather than having an online presence so in my opinion people not wanting to reveal who they are online is something everyone should respect. Sure its nice to know who someone is/ where they are from but it is in no way a prerequisite to asking stimulating technical questions and engaging in productive dialogue.


Josh
2013-2014 MRacing FSAE Aero/Composites subteam member
2014-2015 Michigan Hybrid Racing Front Wing Development Lead
2015-2016 Michigan Hybrid Racing Undertray Development Lead

[Z]

I have spent decades at race-days, car-shows, etc., having very long and interesting discussions with the "strangers" there about the cars and other technical stuff. Most of the time nobody bothers exchanging names, because we all know we will immediately forget them!

The only time personal details ARE exchanged is at the very end of a discussion, and then ONLY if some future business contact is desired. Namely, someone wants to buy or sell something from/to the other party...

Note how the "Interweb" is always asking you for such personal details, and how it is awash with all those annoying pop-up ads, targetted specifically at your interests. Is that what you are after, Claude? Do you want to make money, or just share knowledge?

Z

[rjb2968]

Thanks guys, it isn't even so much as keeping our teams goals a secret but I just literally do not want to share my information publicly outside of facebook.

[apalrd]

Okay some information on turbo FSAE cars:

Rules:
-You can have a pipe between the compressor and the throttle (it wouldn't be practical to connect them directly). You cannot have a pipe >60mm diameter.
-You can have any volume between the throttle and the engine, including a plenum or intercooler or whatever.

Efficiency:
-There isn't really a great reason to turbocharge a 4cylinder engine, you can make similar power with good acoustic tuning. You won't see any efficiency gain of running a 4 cylinder with turbo unless you are running an extremely over-expanded Miller cycle.
-There are a lot of good reasons to turbocharge a 1 cylinder engine, our powertrain package (WR450f+turbo) is considerably lighter than the common CBR600 and makes enough power for our car.
-For an I1 (is it really an inline if it's just a 1cyl?), pulses are massive, be very careful of the design of them. For an I4, still be careful of pulses. Even with a turbo, pulses are still there, so be aware of the acoustic effects when you design your intake and exhaust.
-Depending on what your efficiency is now, you could spend some time with part-throttle engine calibration. Going leaner and advancing spark appropriately does wonders for efficiency. In fact, making sure the spark calibration is good over the entire engine range is extremely important to efficiency.

On low end torque:
-You can make low end torque on a naturally aspirated engine if you choose to match your acoustic tuning peaks. You can actually pick whatever RPM you want. If you utilize the acoustics well (possibly with different acoustics on cyl 1/4 and 2/3) you can end up with an incredibly flat torque curve, if that's what you want. So if you just want to change the shape of your torque curve you should look a lot into acoustic pulse tuning. If you want more information on this, I can point you in the right direction.
-With any turbo, the low end torque is quite bad until the turbo spools fully. With our I1 engine, we can make full boost by 7k rpm, but in FSAE we do not spend any time below this so we are always running with potential for full boost.

[rjb2968]

Thanks for the informative reply, I was wondering why you say that there is not a good reason to turbocharge a 4 cylinder engine.I mean you are increasing the engines volumetric efficiency and with a properly sized turbo there should be no problem on getting it to spool very quickly. As far as moving the torque curve in combination with a turbo there are certainly tricks to be played with the cam timing.

If i'm not mistaken kettering's motor is all stock asides from maybe a forged piston correct? Also if you don't mind me asking out of curiosity what boost levels are you running on that motor?

Input is appreciated.

[apalrd]

Properly sizing the turbo is quite hard for tiny engines. For an I3 and up with a single turbo (or V6/I6 and up with two), and equal length exhaust runners, the pulses all come to the turbine relatively evenly so the mass-flow through the turbine is nearly continuous.

For I1 engines, the pulse is gigantic, and it can choke the turbine temporarily (pulse by pulse), even though the average mass flow isn't nearly enough to choke the turbo. This is good for the turbo (lots of energy is extracted) but really bad for engine backpressure (which drives poorer gas exchange, lower VEs and higher residuals). We found that a MGT1238 (one of the turbos Honeywell gives to FSAE teams) was not large enough and we were severely choking the engine at high RPM. Kettering also develops a high-efficiency low-power 600cc I2 engine for SAE clean snowmobile challenge, we make less power than our FSAE motor (without a restrictor!) and see many issues with uneven pulses (180deg firing order I2 4-stroke) interacting poorly with the turbo. A larger turbo solves this problem but causes you to be in a less efficient area on the compressor, in some cases close to the surge line (because the flows are too low for a compressor of that size to get into the higher boost areas of the map).

On a 4 cylinder it is possible to reach about 85hp naturally aspirated using good NA design (intake/exhaust acoustics, cams, internals, .....). There is little need for more power than that in FSAE. With a turbo you can't make much more power because you will reach choked flow with the restrictor, so the power/weight of the powertrain is worse.


For Kettering's turbo package, we ran a conservative 80 kPa of boost last year at Lincoln. The internals are stock except the cams (which are YFZ stock). We have reached about 65rwhp in testing, at Lincoln we were stable at 61. That is roughly 10hp up from our 2014 NA powertrain, which was 3 years in development. However, peak hp isn't nearly as important as the shape of the torque curve, we were able to reach 60hp NA but with a very peaky torque curve at like 10k. Our NA designs started flattening the torque curve for more torque at all points which are usable in FSAE at the expense of peak power number, but the turbo was able to significantly increase the 'area under the curve' of torque. We had full boost by ~7k rpm. We didn't want to blow it up our first year and have many tricks left to increase power and boost.

[Poe]

The torque gain we saw at lower RPM on a four cylinder was massive. No amount of intake or exhaust tuning would have produced the same results. The advantage with the turbo was being able to choke the restrictor beginning around 6000 rpm. Our car was geared to run the autocross/endurance courses without shifting. The car was very driveable and I wouldn't say it was overpowered by any means. Peak horsepower was roughly the same as our naturally aspirated configuration, but most of that power was available over a wide RPM range rather than concentrated at one speed.

Fuel economy was down from normally aspirated, but maybe BSFC was down, I don't know - we didn't have a good way to measure that.

-NC State '03-'07

[apalrd]

We have designed around 2 gears in an autox. So, 'low end' to us is torque from 7k to 9k or so (redline is 11k). With NA we could have a torque peak at 10k (high power number) or a flat curve from 7.5k to 10.5k, with the turbo it's similar but shifted up. If you're using a much wider RPM range (6k to 14k?) then you could build a lot of boost on the low end for a 'constant power' engine which would perform similarly to a perfectly tuned CVT (powertrain wise).

BSFC is best at around and slightly above MAP = BARO for turbo engines. This is why fuel economy of normal cars goes up (higher mpg = less fuel), since the engine can go down in displacement and cruise at higher MAP (maybe even MAP=BARO) for good FE and jump into the less efficient boosted region for passing maneuvers. For an FSAE car the same would be true, going from a high performance NA engine to an engine which has less power NA and uses boost to build it back up. The MAP=BARO point is lower, so an autox would spend a lot of time close to that (at about 50-60% pedal)