How are you mixing...or what fuel are you running in your high compression Raptors?

Also, the YFZ450 has 11.9:1 Compression ratio. It is safe to run 91 octane in these. Why do I have to run race gas in my 12:1 Raptor?

 

Premium should be fine....race gas is only need for comp. above 12.5:1...i believe

 

DO NOT run pump gas in your raptor if it is 12:1 compression. Head design is the reason some quads like the YFZ and Z 400 can run pump gas. If you try to run pump gas in your 12:1 raptor it will prematurely detinate and you will most likely melt down your piston. I have a friend who's raptor is 11:1 and he runs 50/50 mix of VP's ultimate 4 and C112.

 

I had 11:1 before the rod blew. I ran 91 and experienced no detonation problems at all. When I tore the motor down to replace the rod, there was no sign of detonation. I tried race gas when it was 11:1 with no change in performance, so I didn't waste my money.

So, I have a couple questions:

1. Can you actually hear the pinging in a Raptor like you can in a car?
2. Can you see signs of detonation on the spark plug?
3. Will it be easy to tell if I need to raise the octane or will I just melt a piston or something? I would like to experiment with race gas/91 mix ratio to maximize the use of the high dollar race gas. Are there any suggestions?

An easy response is....Dude, you better just use race gas to be safe... I know that already.

Thanks!

 

Cam profile/timing makes a difference as well. This is good info, do not run pump gas in 12:1 on a rap. I run 93-94 octane pump on my 11:1 and still mix with some 110 on warm days.

 

haha, you seriously run vp 4 in your 700 prarie...thats some funny stuff.

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Try 93 octane and look for small black or silver flecks on the plug porcelain.

With a 12.5:1 piston, I have exactly 200 psi cranking compression. That is right on the edge of 93 octane, anything higher needs race gas. I run VP Red just to be safe, it's not too expensive and it's very clean burning.

 

That's good info.

Its got the Hot Cam stg 2. Maybe I should check cranking pressure to see where I am at.

What are you paying for VP red?

 

Your altitude will make a difference also. You will have less compression @ 5000 feet than you will at seal level

 

If you still have the stock decompression mechanism, you won't get an accurate cranking compression reading unless you loosen the exhaust valve rocker adjustment to prevent the decompression pin from holding the exhaust valve open.

I pay about $5/gallon for VP Red.

I'll bet that you can run 93 octane but you'd better check with your builder to make sure.