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Old 08-03-2005, 12:12 PM   #1
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Default New to 5 port

I have been running an OS 12CVR (3 port) in an Associated Gas Truck on the dirt oval for about a year. It was real simple to tune and seemed to have good power any time I pulled the trigger. Now I am running a Custom Works GSX sprint car on the dirt oval but using an OS 12TZ (5 port). The symptom I'm having is: especially when I've been pacing for about 2 laps at 1/4 throttle and I suddenly pull the throttle back fairly quick, the engine will emit quite a bit of smoke and then flame out. I am running the gear ratio other people are running with my type of car, but I'm wondering if the engine might be lugging when I get on it and thus flaming out. To get up to speed, I have take a straightaway or so to get on up to speed. It is better at getting up to speed after running about 2 or 3 laps at racing speed. Is this an indication of needing a little more gear or do I just need to change my way of building up speed after pacing? Once the car is running up to speed it seems to perform just fine. After about 5 minutes of running it comes off the track around 225 - 230 degrees. I've done the pinch test at idle and after about 2 seconds the rpm's start to increase. Oh, I'm using a P6 plug. Also, the 12TZ comes with 2 air inlets (5mm? and 6mm?). Is there a general rule of thumb as to which inlet to use? Right now I'm using the smaller of the two.
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Old 08-03-2005, 02:07 PM   #2
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It's too rich on the bottom end. Lean the bottom out, since you're basically on the high end needle for oval anyways.

A few of us in NY are running D.O Late Model cars- 4WD. They scream! We are barely letting off the gas to enter the turn then right back on it.
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Old 08-03-2005, 02:16 PM   #3
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Ok!! Thanks, I'll give it a try. We're running foam tires on dirt, and the most we let off is 1/2 throttle in the corners. Sometimes WOT through the corner if you can hit the groove just right.
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Old 08-03-2005, 02:21 PM   #4
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Really there is no need to get a five port motor anymore because most 3 ports are if not faster than they are almost fast as five ports now.
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Old 08-03-2005, 02:24 PM   #5
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After reading these threads I'm realizing that now. Thanks for the info.
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Old 08-03-2005, 02:31 PM   #6
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What about the different sized inlet ports? (sorry I don't know the correct terminology) On the 12TZ, it has 2 interchangeable inlets. One is larger than the other. What are the advantages/disadvantages? I presume by changing the diameter of the air intake you must be changing the characteristics of something.

Last edited by MauriceG; 08-03-2005 at 10:14 PM.
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Old 08-04-2005, 11:16 AM   #7
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Hmmm. No replies. Ok, how bout this. What I'm referring to is the interchangable air inlet on the OS12TZ.

Last edited by MauriceG; 08-04-2005 at 11:30 AM.
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Old 08-04-2005, 08:38 PM   #8
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The smaller one will have a wider power band... easier to tune too.
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