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Originally Posted by GX150
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Quote:
Originally Posted by ckau
If you go by the math, CC's ,displacment, stroke and all that other techno stuff it works out to be a total of 14" measured from the end of the velocity tube, through the carb, intake , head tract to the combustion side of the intake valve. Taking into account the thickness of gaskets and couplers. I measured this a while back and came up with a velocity tube of approx. 6.75 ". There's too many variables to nail it down but something in that range works good.
The purpose of the tube is to reduce air turbulance and enhance velocity by straightening out the air flow before it enters the carb. Too long a tube reduces velocity. Too short doesn't give the air enough time to organize. Bends in the tube counter-act the purpose. Playing with the length does give a marked difference in throttle response and final air/fuel ratio.
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The length of the cold air tube comparing 6" to 8" will be so small to worry about.Now when talking 4,6,or 8 cyl engines the science becomes critical when going for the most effficient performance. The important thing on the single cyl. engine or even the 2,or 3 cylinder engine which move the pistons without any variation, in other words up and down at the same time is to rid the intake path of any restrictions. The stock air box restricts due to its long bendy tubes leading into a large air box then restricting back down into a smaller tube actually interupts slowing down the air flow. When converting to a strait cold air intake all restrictions found in the stock airbox are removed. It really won't make any difference if the CAI is 6" or 12" unless you are to be in some competition where 100th of a second can mean the difference between winning and loosing. I run mine @ 10" total including filter so that I get the coolest air possible which will make a bigger difference. As far as the mud concern on the filter you just have to run a quality pre filter. There really nice for you just remove and run under water to clean, shake the water off and reinstall. This will take 30 seconds to do, well maybe a bit more but you get my point. Sand and mud will clog an oiled filter really fast so the prefilter is a necessity in those conditions.
As far as the exhaust goes, the MRP will be a great improvement over the stock exhaust but the price for not being a true tunned exhaust is its problem. But so is the Hammerhead exhaust. I will say this, I have tried the hammerhead exhaust on my 150 and actually lost power as compared to the MRP exhaust, probably due to the scavenging effect lost dur to a much less restriction, but my engine is not the average GY6. I can also say that one of my customers had the HH exhaust with my head and cam on his 250 cc and noticed a huge difference (his words) when installing the TK exhaust. The problem with the buggy world with perf. parts is they were either designed for the scooter or a non exact copy of something once designed for our buggies. The MRP exhaust was to be a cheaper alternative to the Eastside Exhaust of past but is not an exact copy so some of the low end torque gains the Eastside gave were lost in the MRP copy.