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What's wrong with this motor?
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Author:  bevans37095 [ Thu May 07, 2009 4:18 pm ]
Post subject:  What's wrong with this motor?
OK, just test fired a 2500 type 4 engine running on propane. Sounds OK but my main concern is that when you rev the engine and let off quickly, the engine doesn't drop RPM's as quick as I think it should. I'm used to a high compression gas motor acting like a brake when you let off the throttle. I think the compression ratio is around 8:1. Is this just a characteristic of running propane? Is the compression ratio too low? I know the compression ratio is low for propane, but I thought it would work well with the turbo. I believe a vacuum leak would cause this, and I'll check more, but I think it is sealed up good. Any suggestions or advice?
Author:  vwtravis [ Thu May 07, 2009 10:10 pm ]
Post subject:  Re: What's wrong with this motor?
What kind of mixer do you have? Do you have the turbo on it now? Do you have the mixer before or after the turbo? The 8.1 is still low for a turbo motor on propane. 9.5 would be good for 10-12 # with your dizy lock at 24* and have good throttle response. If its water cooled you mite go 10.1.
Author:  bevans37095 [ Thu May 07, 2009 10:47 pm ]
Post subject:  Re: What's wrong with this motor?
Impco 425 mixer. Turbo is on it now. It is draw through--mixer before turbo. Only oil cooled/lubricated turbo.

I played with it a while this evening. Once it warmed up it seemed to do a little better. I ran into a couple of other problems.
1) It smokes real bad which I didn't think propane would smoke much.
2) It is blowing oil out of the exhaust. I'm guessing it is coming from the turbo but I'm not sure.
3) The evaporator froze up bad. I routed the oil through the filter --> oil cooler --> tee to turbo --> evaporater --> dump into block.

I thought that maybe part of the smoking was due to the evaporator freezing up. The evaporator was getting warm oil flowing through it but it never thawed out after running for about 15 minutes (in the garage). I think I'll re-route the oil and get a better flow from the oil filter straight to the evaporator then dump into the motor.

Any suggestions or problems to look for?
Author:  vwtravis [ Thu May 07, 2009 11:11 pm ]
Post subject:  Re: What's wrong with this motor?
The smoke could be from the turbo compressor seal it has to be a carbon seal. At idle vacuum will pull oil past the seal. If this is happening it will cause your smoke and idle down prob. The best way to heat the evap. is the return line on a dry sump. If you dont have one restrict oil going in (so oil psi isnt lost) by braising a fitting and drilling it like 1/16. The hose going out needs to be higher than the inlet before returning to motor. The reg. cant handle no more than 15 psi of oil so the return cant be restricted. You can blow throw the mixer fairly easy if your turbo's not sealed with carbon seal.
Author:  bevans37095 [ Fri May 08, 2009 8:13 am ]
Post subject:  Re: What's wrong with this motor?
How can I tell if the turbo has a carbon seal? I can remove the turbo and check it. Can one be added if it doesn't have one? If so, where can I get one and can I install easily my self?

Thanks for your help.
Author:  vwtravis [ Fri May 08, 2009 7:22 pm ]
Post subject:  Re: What's wrong with this motor?
This is a carbon seal on ebay http://cgi.ebay.com/ebaymotors/-T-3-tur ... dZViewItem If it dont have one it will look like a small piston ring. You can take the turbo apart and see. I have never installed one not sure if the housing needs machined or not. They say you cant take this turbo apart and assemble it without balancing it. Turbo shops wont sell you parts because of this. I have had several apart and made new bearings with no problems. Why not blow through?
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