single vs. four poll

[illiterate]

I was pretty much a single-cylinder guy until i went over some earlier posts. So, I just had to ask. How many of you decided to go 4 cylinder after doing single for a year. how many chose to do the opposite. Also give ur reasons for doing so

[Jersey Tom]

Now, I'm not much of an engine guy, but..

Single cylinder, like a 450cc single cylinder that are in Honda ATVs? I'd think you'd need to be revving that at 15000rpm to start choking the restrictor, as opposed to ~10500 with a 4 cylinder 600cc bike engine. I have no idea if those engines go up that high. That's getting into redline for the F4i. I'd think the 600cc 4cyl would be more driveable, if a little heavier.

I could be totally off base though.

Wonder what the torque curves look like.

In any case the single cylinders just dont sound sexy.

[kwancho]

I got the impression that most single cylinder cars run FI to compensate. Is that true?

[Jersey Tom]

Compensate for what? I'd say EVERY car at competition, 1 and 4 cyl, run EFI. All that I've seen anyway.

[BeaverGuy]

Having run a 600cc four during my involvement with FSAE and looking at what I think would be ideal, I would select a less than 600CC single if I was to do a clean sheet design. The restrictor will not really affect the singles meaning that what works on the unrestricted engine should work on the restricted one too. They weigh considerably less. Their natural redline with primary reduction and 1st gear factored in is lower, which should mean fewer compromises with sprocket selection. And finally, their torque and power curves can be very comparable to an N/A 600cc four.

[Homemade WRX]

Originally posted by Jersey Tom:
Compensate for what? I'd say EVERY car at competition, 1 and 4 cyl, run EFI. All that I've seen anyway.
I think he meant force induction when he said FI...not fuel injection http://fsae.com/groupee_common/emoticons/icon_wink.gif

[kwancho]

Yeah, I did.

[John Valerio]

we're switching from a turbo single cylinder (suzuki ltz, bored to 470cc) to a cbr this year and our engine guy was pretty damn happy to do so.
i'd be careful when saying you can turbo a single to compensate for the power loss because you're not taking everything into consideration. cbr's are sweet and bulletproof because stock they make 110hp+ but we can only get 75-80 out of them. when you take a single with relatively low hp numbers (stock) and turbo it, you can make alot of power (we made more than twice stock power), but it won't do you any good because you'll bust transmissions and smoke clutches. also with the turbo we were having trouble shifting (having to get off the power for far too long). with 65 hp on a 378 lb car we had a pretty good power/weight but it wasn't much good if you couldn't get that power to the ground fast enough.
so you just have to remember that ultimate power isn't necessarily the goal. we're in an autocross-style race, not a dyno challenge.
oh and i also know that most single teams do not run turbos to compensate because to the best of my knowledge we were the only turbo single team at detroit last year.

[Homemade WRX]

Originally posted by John Valerio:
we're switching from a turbo single cylinder (suzuki ltz, bored to 470cc) to a cbr this year and our engine guy was pretty damn happy to do so.
i'd be careful when saying you can turbo a single to compensate for the power loss because you're not taking everything into consideration. cbr's are sweet and bulletproof because stock they make 110hp+ but we can only get 75-80 out of them. when you take a single with relatively low hp numbers (stock) and turbo it, you can make alot of power (we made more than twice stock power), but it won't do you any good because you'll bust transmissions and smoke clutches. also with the turbo we were having trouble shifting (having to get off the power for far too long). with 65 hp on a 378 lb car we had a pretty good power/weight but it wasn't much good if you couldn't get that power to the ground fast enough.
so you just have to remember that ultimate power isn't necessarily the goal. we're in an autocross-style race, not a dyno challenge.
oh and i also know that most single teams do not run turbos to compensate because to the best of my knowledge we were the only turbo single team at detroit last year.
true...you guys did have an issue with the exhaust pulses for a turbo...and manifold pressure

[illiterate]

for a while forget the high power outputs and turbos. Isn't it simpler for first timers to get a single cylinder up and running. And also tuning and maintenance will be much simpler.

[Jersey Tom]

Take 4 F4is.. cut the stroke down to a quarter of what it is, weld 4 of them together and make a W16 or something close. It would be sweet, dudes.

[Homemade WRX]

Originally posted by Jersey Tom:
Take 4 F4is.. cut the stroke down to a quarter of what it is, weld 4 of them together and make a W16 or something close. It would be sweet, dudes.
someone call WWU...we have new one for them...:lol:
if only we had a CNC...

[Big Bird]

Fourth year of building a single at RMIT, no intention of changing at this stage. We've never considered doing forced induction because that has always been diametrically opposed to our design goals - that being to build something light, simple and within the means of an amateur student manufacturing crew.

I think if you are going down the single route, and then feeling as though you need to "compensate" with complications such as forced induction, then you have missed the point. It is no use adopting a concept whereby you sacrifice some power for weight - and then turn around and try to get all the power back again. Good design is about understanding your compromises, and in our case we knowingly compromise our straight line acceleration (believing it to be a minor factor in this game) to buy advantages in terms of handling and manufacturing / development time, (which we consider to be crucial factors in this game).

Since adopting a 450cc single we have had no trouble at all with competitiveness, and have picked up a few fastest endurance laps on the way. I think Rotor set fastest lap at Detroit last year too, and by all accounts our dyno reading for that event was somewhere around 30kW (although i think there were some problems with the way the car was tied to the dyno from what I've heard). Anyway, I'm not too sure that there is any established need to "compensate".

I've been known to waffle endlessly on this subject, so shan't bludgeon you all with more. But if you would like some background info into our initial decision to choose a single, please have a look at a thread called "Life, The Universe and our curious obsession with engines" that I started on here about six months back.

Cheers all,

[BeaverGuy]

Big Bird,

You guys only got 30kW on the dyno at Detoit? That is around 40HP yet, your design boards claim something considerably higher why?

[Big Bird]

Josh,

Yeah, not sure what the problem was, (I wasn't there and heard it all second hand). But someone was saying that there was a problem the way the car was tied onto the dyno at Detroit - maybe not enough traction or something.

We were good for around 50-odd hp when we first used the WR in 2003, and got up to around 60hp (rear wheel) from when we took the first steel-frame car to FStudent in 2004. The following cars were around the same mark. Those figures were on our dyno at uni, we think it is reasonably accurate.

Who knows if the Detroit figure is accurate (or whether our uni dyno is accurate). I guess a better indication of the point i was making was that even our heaviest single car (the first one, around 200kg) was as quick as anything else in the comps it entered - so i doubt the need for "compensation" is really there.

Cheers,

[terra_dactile]

Hi Geoff,

I was wondering at which rpm you were able to get 60 hp at the back wheels, 10K plus ? Also do you guys actual have a custom cam shaft, because it is weird to see such a high value at the wheel,that would mean you have roughly 67-70 hp at the crank!
Torque wise, we usualy have around 32-34 Ftlbs how does that compare to your value ?

We use a land and sea dyno built for testing ski-doo engines, and it is attatched to the end of the transmission of the WR 450 F.

Jude Berthault
ETS FSAE
Steering System Leader
Brake System R&D

[Big Bird]

Sorry Terra - I planned to respond once I had been out to uni to check it out - and then promptly got distracted. Hope you haven't been holding your breath waiting for me.

The max hp was around 10,500rpm from memory, maybe a little less. The reading was taken on our chassis dyno which is big enough for a full-sized car - so it might or might not be accurate for a little kid's toy like our thing.

Engine is stock internally, just our own intake and exhaust.

Anyway, we now have a new engine dyno setup which is a bit better and more appropriately sized. The lads are working on getting some graphs as I write. I'll let you know what comes of it.

Cheers!