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You can do that with any big bore. Just order a lower compression piston. You can buy pistons in any configuration you want. Kind of pointless though, because if you do that, the only thing the big bore will do for you is increase torque a little. Kind of a waste to go through all that work of a big bore and run low compression. You can increase stock bore compression and still run pump gas and I'm sure it would be a lot cheaper with the same out come. ;) You should easily be able to go 12:5 compression and run 93.
 

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:3question: :3question: :3question:

I have 12:1 and everyone that I have seen and heard of suggests 100 octane.

I think compression dictates the amount of octane or am I wrong?
 

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Octane is rated with measurement of ignition resistance and burn speed. Higher the octane, the less chance of having fuel can pre-ignite. Running the lowest octane you can with out having pre-ignition(denotation) the better. Another thing that people do is to run a colder plug.. say in turbo/supercharged applications for example. Increase the compression, hot plugs can pre-ignite, so colder plugs are installed.

Here is a good read if interested in how the octane ratings work > http://en.wikipedia.org/wiki/Octane_rating

Ignition timing, fuel maps etc.. all play a part in what octane you can run.

More info on why and really to answer your question > http://www.faqs.org/faqs/autos/gasoline-faq/part3/section-1.html

And as you can see by the chart they list 9:1 compression should be over 93 octane but because of how the motor is setup we can run 87 on a stock engine. :)
 

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so should us stockers be running 93? would it be better? I've always ran 87
 

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I ran 93 when mine was stock(didnt have to but I did) and I run 100ish octane now(3gal. 93/2 gal. 111 in a 5 gal. jug) with my 11:1. I have ran 93 with this setup a couple of times but it gets hotter faster when I did. I wouldnt even consider running anything less that 98-100 with over 11:1
 

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VelociRaptor said:
I ran 93 when mine was stock(didnt have to but I did) and I run 100ish octane now(3gal. 93/2 gal. 111 in a 5 gal. jug) with my 11:1. I have ran 93 with this setup a couple of times but it gets hotter faster when I did. I wouldnt even consider running anything less that 98-100 with over 11:1
Running 93 did nothing for you at all and actually probably would performed better with 87.

Guys have run 13:1 compression with 93... I persoanlly wouldn't do that, it but 12:1 -12:5 shouldn't be an issue. Check the z400 central guys with the z400 big bores @ 12:1 running 93 with no problems. Once again I think you guys should real the last two links I posted.

Here are few links I just dug up:

http://www.z400central.com/invision/index.php?showtopic=69210&hl=93+octane

http://www.z400central.com/invision/index.php?showtopic=69210&hl=93+octane

http://www.z400central.com/invision/index.php?showtopic=67420&hl=93+octane

http://www.z400central.com/invision/index.php?showtopic=68874&hl=93+octane
 

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You guys are too fast for me. I just updated all the engine kits with new prices and info on them. I was gonna make a post this morning about it.

As far as the octane level to run in you engine it depends on a lot of factors. Just because you can run 12.5:1 pistons with 93 octane in a z400 motor doesn't mean you can in a raptor engine. Bore size, combustion chamber shape, piston dome shape, and a bunch of factors will ultimately determine what octane to run in an engine.

Heck YFZ 450's come with 12:1 compression ratio from the factory and run on pump gas just fine. This doesn't mean a Raptor at 12:1 should also run on pump gas.....

It is true that if you run higher octane than needed you are loosing power. At the same time I would rather error on the high side than run too low of an octane fuel and destroy an expensive engine from detonation.
 

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Yes, camshaft/camshafts profile, overlap, duration all play a part as does ignition timing. If you just change compression(and everything else in the engine stays the same) the octane requirements will have to change accordingly. Sure, you can run pump gas on 15:1 with a cam that bleeds off alot of cylinder pressure and the ignition turned way down but then whats the point in running that much compression. For optimum power you need to run the lowest octane you can until preignition occurs but like what was just sayed I would rather run what I know what will work instead of what should work. Ive been building engines for over a decade and I just go by what I know to be the case. Even porting and the grade of materaial the cylinder and head are made of plays a part. Like in the late 60s muscle cars that had 11:1 compression engines with cast iron heads, they had camshafts that were designed to bleed off cylinder pressure and we had leaded gas that had better octane ratings than today.
 

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Anybody know what type of number they are getting on the 812 low compression kits? What type of fuel is run?
 

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Geisick said:
You guys are too fast for me. I just updated all the engine kits with new prices and info on them. I was gonna make a post this morning about it.

As far as the octane level to run in you engine it depends on a lot of factors. Just because you can run 12.5:1 pistons with 93 octane in a z400 motor doesn't mean you can in a raptor engine. Bore size, combustion chamber shape, piston dome shape, and a bunch of factors will ultimately determine what octane to run in an engine.

Heck YFZ 450's come with 12:1 compression ratio from the factory and run on pump gas just fine. This doesn't mean a Raptor at 12:1 should also run on pump gas.....

It is true that if you run higher octane than needed you are loosing power. At the same time I would rather error on the high side than run too low of an octane fuel and destroy an expensive engine from detonation.
I'm not wanting to start a argument, but I have a few questions, I too... have built motors on more than just single cylinder quad motors. I personally never heard anyone running a 12:1 piston setup in anything that couldn't run fine on 93.

1) How many failure have you saw or heard with guys running 12:1 on 93 octane on a raptor? Also, what was the air/fuel ratio at the time of failure?

2) "Bore size, combustion chamber shape, piston dome shape, and a bunch of factors will ultimately determine what octane to run in an engine" Why?
I can see cylinder wall thickness being a factor due to increase in heat(may cause pre-ignition).... but why the rest? Piston dome shape? Compression is compression.

During a compression stroke it either detonates or it doesn't. I guess I'm kind of confused about what makes the raptor so susceptible to detonation compared to a big bore 400 or even the 450 for that matter.
 

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Chicagoland Atv said:
More info on why and really to answer your question > http://www.faqs.org/faqs/autos/gasoline-faq/part3/section-1.html

And as you can see by the chart they list 9:1 compression should be over 93 octane but because of how the motor is setup we can run 87 on a stock engine. :)
You can't use a chart, especially that one. There are simply too many factors involved to assume that any one chart can encompass multiple internal combustion engines. Now if someone took the time to create one for the 700R then it may be useful, but one could never realistically account for all the variances that any owner could come accrossed. What we do is listen to those who've run a similar setup and try it out ourselves. If it works then we're set, if it doesn't we have to do a little more experimentation.
 

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actually i'm not exacly intrested about the 812 kit, but i want to ask somethink because you are talking about pump gas and cams. I'm intrested for stage one cams and the highest compression piston for stock bore. The question is what's this piston, because i don't understand what you mean pump gas, you are talking for 87 octane and here in Europe standart gas is 97 and super 100. What compression should i choose?
thanks......
Anyway nice kit, but we don't have yet atv dragster :'(
 

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Europe uses a different method for calculating octane pump numbers than the US. In the US it's calculated using the average of the research and motor octane numbers. In Europe just the research octane number is used.

Your 97 rated fuel would be similar in effective octane composition to a 91-93 rated fuel from the US. In other words you'd likely be able to run what we in the US call a "pump gas" setup on the same fuel you get from your gas pumps without concern for damaging pre-detonation.
 

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Exactly Maddog,
I purchased my 734 Kit with 12:1 compression piston. That company has quite a reputation of building Strong running 700's. In fact I understand this company has the Fastest Raptor on the Planet (the white bike). They have been building and tuning 700R motors to get the best performace out of them and the suggested Octane is 100. 50-50 mix. I have no reason to doubt this measurement from them, I'm sure they get feedback from the quads they are working on as well as customers like myself. They have done the research for me (and us 700 owners) with this compression, extreme head port and web 111 cam, LTE's , PC111 and big air intake. If predetination and excessive heat happens it chould shorten motor life, and Nobody wins :unsure:. I'd rather spend a few extra bucks to run hard and protect my investment. :thumbsup:
 

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fuck that kit sounds sick, if i wern't stuck with so many trails up here and still out in cali where i could focus on dunes i would love something like that, i just pictured myself going up the hills, i had to slow down in my head cuz i got scared!
ok if you went that big could you get away with just a +4 swingarm? or would you have to got + what 8? and if you go bigger than a +4 how will it do on trails? i don't think i know of anyone that rides woodsy muddy trails with a +8 or something close? anyone got some feedback ? at 3:30 am?
 
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