Horsepower

[VFR750R]

I think the primary purpose of the restrictor was safety. But once implemented then they could open the rules to forced induction and keep power levels similar. I think when the original rules were written, no water cooled singles existed. The only real choice in the late 80's and all of the 90's were 600 cc 4 cylinder engines.

[thewoundedsoldier]

Missouri is not in the event guide so I don't know what path they took, but your car looks very small. 48/44 track is small.

We all know the weight savings involved, but more important is the dimension difference between large, powerful cars and small, agile ones. I'm sure you and OSU had an easier time in the slaloms, and Missouri had better acceleration off the corners.

I'll bite and provide numbers on our car. The 2010 SJSU Formula Hybrid car had two motors rated at 35kW each. Just thinking of that power number makes me laugh. We probably only realized about 25 HP each.

[TMichaels]

Just to fill the discussion with some data, which is at least a bit feasible: In 2008 we had some cars on the same dyno at FSG. The data can be found here w w w .formulastudent.de/fileadmin/user_upload/all/2008/Results/FSG08_Dyno_Results.xls

The results of the dynamic events from that year can be found here:
w w w .formulastudent.de/events/event-2008/results/

Maybe it helps.

Regards,

Tobias

[bob.paasch]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by EHog:
1st place auto-x at FSAE WEST had ~96HP and the car weighed ~425 with wings.

2nd place auto-x at FSAE WEST had ~48HP and the car weighed ~413 with wings.
</div></BLOCKQUOTE>

... and the 3rd place Autocross at FSAE West had ~45 HP and the car weighed 325 with an undertray.

The same car without the undertray was 2nd in autocross at FSAE Michigan, 1st at FSUK, 2nd at FSG, and 4th at FSA.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">
My question is, how much power do teams have?
</div></BLOCKQUOTE>

GFR, not much...

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">
How much do you believe this helps times?
</div></BLOCKQUOTE>

As Steve and Pat are fond of saying, this is a handling competition, not a power competition.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">
Also, a fundamental question that I simply do not know the answer to... Why was a restrictor of 19/20mm implemented? Was it a safety precaution or more of an engineering design challenge?
</div></BLOCKQUOTE>

The restrictor was implemented primarily a safety precaution, but it certainly has worked out to be a nice design challenge.

My question for you, if you're only getting 48 HP out of that Ape, why bother? The 450 singles are cheaper, simpler, and lighter.

[EHog]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by rp:
My question for you, if you're only getting 48 HP out of that Ape, why bother? The 450 singles are cheaper, simpler, and lighter. </div></BLOCKQUOTE>

To be honest, our peak HP could be anywhere between 45-60. We would have a legitimate number but we have a chain reduction on our dyno because the engine has so much torque at low RPM that the dyno couldn't pull it down.
It was going to go on the dyno at WEST after endurance but... well... lets just say the large cloud of smoke ruined that for us.



Bob,

We ran an F4i for many many years, and in 2009 we decided to switch to the Ape. The two primary reasons for switching was because
A) the ape is ~60lbs lighter
B) we wanted the nearly flat torque curve so that gear selection was much less critical

On a course in which you may need 1st-4th gear on the F4i, suddenly you only need 2nd and 3rd...
I know there are many more reasons but myself not being the engine guy, I won't even try to guess.


Out of curiosity, how much does your single cylinder with tranny weigh Bob? And what does the torque curve look like for such an engine?



NOTE: I am by no means the engine guy and if something in the above text is completely invalid, I apologize.

[thewoundedsoldier]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by EHog:
B) we wanted the nearly flat torque curve so that gear selection was much less critical </div></BLOCKQUOTE>

+1

I think that's a subtle answer to the question this thread poses. Between 450cc singles and 600cc 4-cylinders, one type of engine has a flat torque curve and the other has a sharp torque curve. It's going to be hard to stay in the power band with the latter.

The GFR powerplant is a CRF450. I believe it peaks at like 35 ft*lbs @ 7k RPM, with a decently flat curve between 5k and 8k. I would be very happy to see Dr. Paasch provide tested numbers (i.e. after restriction!) although this might be asking a bit much.

[Demon Of Speed]

On the note of singles having a flat power curve; it makes it much easier for non-professional drivers to drive the car fast(er).

I would bet there is as much time difference in autox due to different drivers as there is to differences in HP. Our fast guy in endurance was 2 sec. faster a lap than the other guy, I can't imagine going from 40-80 HP would make as large of a difference.

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[thewoundedsoldier]

I think the singles will generally have a less flat power curve.

Motorcycle engines are made to be driven easily i.e. flat curves--dirtbike engines focus on that peak torque at the cost of the wide band. While a dirtbike might plateau for a range of 2000-3000 RPM, a motorcycle engine (like the Aprilla SXV) has a range of closer to 5000 RPM.

This is the advantage of a *heavier* motorcycle engine. While durability is a perk, the ability of an inexperienced driver to stay in the band is clutch.

I'm also very much NOT an engine guy, so hopefully other, more experienced members can provide some insight.