What's better PSI or RPC pipes

C

crimsonride

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Joined
Sep 29, 2005
Messages
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I have two pipes sitting around for an ex570, which one should I keep, the PSI or RPC? I like the sound of the PSI a little better I think.
 
Are they singles? If so PSI all the way. The RPC single was not the greatest to say the least. Been there and done it. What year Exciter? The 1987-1990 respond to a pipe real well. The Exciter II models from 1991 to 1993 do not.(except '93 SX) The ignition held those model year Exciters back. I think the PSI was probably one of the best pipes made for that sled. Now if they are twin pipes, it gets more in depth.
 
They're singles. I'll try to get more info on the sleds. I'm swaping the engine from one to another, I think the one I'm putting the engine into is a 91 but I think the engine is from a 89. Is there a designation on the vin numbers or a identification plate somewhere in the engine bay. I can't find anything on the donor sled as the tunnel was cut off and replaced with a arctic cat tunnel.
 
You sound like you know quite a bit about these. I have some oil injection questions, are you familiar with those systems?
 
Not sure on the vin numbers. I know who would though. Pat Hauck @ Hauckpowersports. He raced Exciters for quite awhile. Not sure about your oil injection question. What I do know is they mixed the oil in the fuel line before it made it to the carbs. They never had direct oil injection. I did put it on a couple of my Exciters though. A friend of mine at the time had a dealership and used to get me the nozzles to drill into the carb flange area.
 
The RPC had a aftermuffler under the pipe that was awefully heavy. My Dad ran it on his 1991 EXII and it got slower. Now as mentioned it was hard to get those Exciter II models to respond to anything with it's ignition. We never tried it on the older Exciters, but I thought it was awefully heavy. We owned a couple 1987's a 1990, 1991, 1992 and a 1993 SX Exciter. On the 1987's we ran the PSI twins, but they were the good twins which ran at 8200 rpm. They had a nice gradual sweeping design that curved right towards the exhaust holes. Then PSI changed them around 1988 and added length to them to drop the rpm's down to 7750 to better maintain clutch wear on those old YPZ clutches. This was a mistake. We had a set of these too and they didn't even run close to the 8200 pipes. These had kind of a S-curve in them right after the exhaust port area then made a sweep to the exhaust exits, hence being longer. The 1990 Exciter I owned I bought right from Pat Hauck @ Motorsports of Rice Lake where he used to work. It had the porting mod and reworked stock exhaust where he shorted the Y-pipe and gutted some of the internals. I also ran a P-85 Polaris primary on it for better clutch longevity. That sled would actually outrun the 1987's with the twins on them. Then I tried the good 8200 twins on it. For it's time it absolutley screamed, nothing in my area could touch it, but it came with a price. It had a intermittent bog. This leads to the problem the Exciters had back then. A harmonic imbalance right around 8200 rpm. Another reason PSI changed the pipes. The fuel would foam in the float bowls at a certain frequency and cause either lean burndowns or a bog. I quickly remodied this with 38mm flatslide carbs.(a dealer in Iowa remodied it by putting weights under the float plugs; different story) Then the sled ran flawless. PSI also had a remody for the lean spot in midrange. A different set of needles for the 38mm roundslides which we ran in the 1987's. We never did have any burndowns on any of our Exciters but many people did if you were not up on these issues.
 
Well, I think that answers a lot of my questions, the engine I've removed is the kind that mixes the oil in the line and the one I'm planning to place in it looks to have had the oil injection nozzles added to the carb boots. That's not too surprising to me, the guy I got the sled from had done a lot of work to it so I'm sure they changed it over to the true form of injection.

Another question,

All of my sleds have had the coolant lines that run to the carbs bypassed. This sled has all the lines. Under what conditions should I run the coolant through the carbs and when should I bypass it?
 
Never run it unless you are in deep powder or super cold temps. It keeps the carbs from freezing up with ingested snow and also seems to help with real cold conditions when there is a possibilty of some water in your gas.
 
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