Compression

[Greg]

Does anyone know what the maximum safe compression you can run on a CBR 600 F3 is?
We just rebuild our engine and put a shaved head on it, and we want it to at least last this year.

I belive that we have about 180 PSI at the moment.

Thanks

Gregory Oden
Vandals Racing
University of Idaho

[Greg]

Does anyone know what the maximum safe compression you can run on a CBR 600 F3 is?
We just rebuild our engine and put a shaved head on it, and we want it to at least last this year.

I belive that we have about 180 PSI at the moment.

Thanks

Gregory Oden
Vandals Racing
University of Idaho

[Charlie]

Your psi reading is not a direct compression ratio indicator. All things equal, it will increase with CR, but there are too many variables.

I don't think you can reach too high a CR with the restrictor. That's just a feeling I have with no real testing to back it up. I think you'll run into valve clearance problems before you have too much CR. Check your valve clearances to see how close you are.

While the head was off, you should have measured the chamber volume, piston head volume, etc, so you know exactly what the CR is. I don't know of a better way.

-Charlie Ping
Auburn University FSAE (http://eng.auburn.edu/organizations/SAE/AUFSAE)
5th Overall Detroit 2003
? Overall Aussie 2003. http://fsae.com/groupee_common/emoticons/icon_smile.gif

[Daves]

Maximum safe compression? You can have as much compression as you want as long as the octane of your gasoline (assuming you are using gasoline) is high enough.

The real question is how much can you shave off of an F3 head before the valves get embedded in the pistons.

The best thing you can do is listen to the engine. If you hear detonation, you'll either need to use higher octane gas (petrol for you foreigners) or put a different head on it. There may be other options I am not aware of, though.

The highest octane available at the FSAE competition is 100 octane, but I think normal racing fuel is 118 octane. If you have detonation with 100 octane, run race gas until you can find another head.

As a side note, the nice thing about turbos is that you can adjust how much compression you have. If you dial in too much, just dial in less.

[Greg]

The primary concern I am having is about destroying an engine I put a good amount of time and the teams money into. We told some of the grad students around here about it and they got . . . concerned looks . . .

we did a quick check of how far it was shaved, and we have a good deal of space still, so I am not as concerned about that, though it is always an option :P



thanks

Gregory Oden
Vandals Racing
University of Idaho

[Daves]

In that case, from experience, I know that 14:1 compression on an F4i engine is safe with 100 octane gas.

[Scott Harsila]

I know that in previous years our team has shaved F2 heads all the way to the valve seats without detonation problems, even while running 92 octane pump gas during testing (stock pistons). But as I remember from a few years ago someone wanted to mill the the head at an angle to shave off more because the exhuast seats are lower and there was still material left on the intake side of the head, don't think this ever panned out. The judges will also not be pleased if you have not compensated for the cam retardation due to the decrease in distance from cam to crank, or at least analysed how much effect there is.

University of Washington
Formula SAE 2001-2003

[Greg]

Does anyone know if it will lower the life of the engine by a significant amount? I figure that if it does, these cars will not be run for thousands and thousands of miles, so a slightly lower life for horsepower should not be that big a deal, but I could be wrong.

During our break in time we ran with 92 octane pump gas and carburetors. Now we are running about 94 octane gas with fuel injection, and have yet to run into any major problems yet.

Gregory Oden
Vandals Racing
University of Idaho

[Scott Harsila]

Conisdering that most 600cc sport bikes make more that 100RWHP (maybe 115-120 at the output shaft?), and the record FSAE car is like 84 RWHP (100 at the output shaft? more losses in a FSAE car I am sure) I do not think that an increase in HP from increasing compression will significantly decrease engine life. Although the duty cycle in a FSAE car is much higher, so I am sure the engine life milage would be much less than the bike. In my 3 going on 4 years in FSAE I have seen many engine failures, but no power related failures, mainly oil starvation and overheating.

University of Washington
Formula SAE 2001-2003

[woollymoof]

Why don't people purchase higher compression pistons instead of skimming the head? If you stuff up with the pistons, just put the old ones back in. If you stuff up with the head, you need a new head.

Cheers,

Kirk Veitch
Swinburne University of Technology

[Charlie]

Where can you buy any pistons that will bring you over 13:1 without anything done to the head?

-Charlie Ping
Auburn University FSAE (http://eng.auburn.edu/organizations/SAE/AUFSAE)
5th Overall Detroit 2003
? Overall Aussie 2003. http://fsae.com/groupee_common/emoticons/icon_smile.gif

[woollymoof]

I have no idea

Cheers,

Kirk Veitch
Swinburne University of Technology

[gug]

how much extra compression can you get before you have to modify the pistons to clear the valves? i notice that they already have cut-outs in them, does this mean that even shaving a millimeter off the head requires bigger cuts in the pistons?
TIA.

- if it isnt coming, you need a bigger tool.

[Andy Houk]

We had JE Pistons make some pistons for our F4/F4i. They give an FSAE discount, $500 for a set of 4 with wrist pins and clips but no rings. Much cheaper than the cost of a wrecked head. If you are interested contact Brian Weaver or John Noonan at 714-894-6650. Let them know that the UC Davis team sent you. All you need to tell them is the engine model, the bore you want and the compression you want. You will also need to send this information on university letterhead for their financial department. These guys are not engineers, they are salesmen, so don't go asking a lot of questions. You should already know what you want when you call them. Turnaround time is 1 month. If somebody will tell me how to post pictures I can put up a few shots of our pistons, they're dead sexy.

[Scott Harsila]

Wiseco makes pistons for most sportbikes motors. For F4/F4i I think they claim 12.7:1 compression over the stock 12:1. About $500 per set?

University of Washington
Formula SAE 2001-2003

[Andy Houk]

Wiseco and JE both make aftermarket pistons for the 600 cc engines, 1 and 2mm overbore. A 1mm overbore kit gives a slight compression increase but the overbore increases the total displacementto 618 cc. The rules limit us to 610 cc. That is why we had to have pistons made.

[Charlie]

Wiseco makes a std bore piston for the F4i that increases compression to 12.8:1.

-Charlie Ping
Auburn University FSAE (http://eng.auburn.edu/organizations/SAE/AUFSAE)
5th Overall Detroit 2003
? Overall Aussie 2003. http://fsae.com/groupee_common/emoticons/icon_smile.gif

[Andy Houk]

Well that's news to me, thanks Charlie.

[Scott Harsila]

CBR 600 F4 599cc 67mm - 42.5mm 13:1 W-CK106 $432.95
1999-2002, 4 Valve
Kit includes, 4 Pistons, Ring Sets, Wrist Pins, Circlips and 1 Spring Steel Head.Gasket

From a popular aftermarket website. As far as I know they will fit F4 and F4i.

University of Washington
Formula SAE 2001-2003

[BA]

Greg (the guy who started this thread) and I worked together on rebuilding our engine. Instead of milling down our stock head, we simply got one from another team. It's amazing how many spare parts beer can buy you. The head we're using is shaved about .035" from stock and the combustion chambers went from 12cc to 9.8cc. We have a minimum of .050" between the valves and piston.

Why put a bunch of money into aftermarket pistons? Do these kinds of numbers scare anyone? A racer and mechanic I know told me that .020" of valve to piston clearance was the safe minimum. Is that too close?

Brian Auer
University of Idaho
Vandals Racing (http://www.uidaho.edu/~racing)
FSAE 2003/2004

[Frank]

i was always told 040" was the "bare minumum"

[Charlie]

Is .020 too close? Too close for me.

The F4 and F4i pistons are different because of the changed intake valve angle. They ought to interchange, just pay close attention to the intake clearances.

Brian have you run the engine yet?

-Charlie Ping
Auburn University FSAE (http://eng.auburn.edu/organizations/SAE/AUFSAE)
5th Overall Detroit 2003
? Overall Aussie 2003. http://fsae.com/groupee_common/emoticons/icon_smile.gif

[Kevin Hall]

I believe that the F4 is tighter than the F3. I measured the F4 in stock form, and found there to be about .045 clearance. At that point, I couldn't justify milling a few thou off the head for the minimal change it was worth. Anyone with more F4 experience, let me know if you have succesfully gone forth with this.

Kevin Hall
University of Saskatchewan
'03-'04 Team Director

[Greg]

Charlie

We have run the engine a good deal.
Break in took a few days on the dyno.
We broke it in with carbs.
We got to see the headers turn cherry red too, so that was fun . . . yeah . . . fun.

We now have an experimental intake on it, seeing how good we can get it to run.
The horsepower gain was sugnificant, though we need to test how much of the gains were from the intake and from the shaved head.
During testing we lost a cylinder above about 8000 rpm (we had a bad fuel injector) and it had about as much horsepower as we had at competition last year (if memory serves me).

Plus it just has a nice sound when it gets up into the higher rpms http://fsae.com/groupee_common/emoticons/icon_smile.gif

Here is a question we have been wondering as well, does anyone have suggestions on the temperature rating we should use for our spark plugs?

Thanks

Gregory Oden
Vandals Racing
University of Idaho

[Matthew]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Greg:
Charlie


We got to see the headers turn cherry red too, so that was fun . . . yeah . . . fun.

Gregory Oden
Vandals Racing
University of Idaho<HR></BLOCKQUOTE>

only cherry red? you aren't running rich enough http://fsae.com/groupee_common/emoticons/icon_wink.gif j/k the coolest thing to me about the header glowing on the dyno is if you look at the first few inches of the pipe it doesn't glow very much, because the water jacket is sucking up that heat. Kinda cool. I'm bringing ina camera when we get our R6 back on the stand.

-Matthew Hetler
hetl0020@umn.edu

[Greg]

We need to get a picture of our headers glowing now that we have the fuel injection on. No one seems to remember them glowing before, but I am hoping that we can get them to be nice and red again :P

I did notice the red did not start for a little bit, but it did not cross my mind that the water jacket would cause it.

I think a competition should be started for who can get best color in the headers :P

Gregory Oden
Vandals Racing
University of Idaho

[Eddie Martin]

http://pic7.picturetrail.com/VOL186/1375744/2619075/31819848.jpg http://fsae.com/groupee_common/emoticons/icon_smile.gif

[Matthew]

in '99 our team ran a turbo 250RR on methanol, it was great (i'm told) because the header would glow bright red and the intake would be covered in frost.

-Matthew Hetler
hetl0020@umn.edu

[Jackson]

Greg a/o BA;

Do you guys have a dyno? If not where do you do all your work?

If you have one do you think WSU could use it "for a few beers" a-la your earlier post when you aren't using it? We don't have our F4i yet as it is currently in transit.

Brian
Wazzu Formula

[Sam Zimmerman]

Brian,

Please email me at racing@uidaho.edu to discuss the use of our dyno.

Thank you,
Sam Zimmerman
Vandals Racing (http://www.uidaho.edu/~racing)