JSH 68
Newbie
I have just mounted an mpi sc on my apex and the boost gauge only shows me about 4.4 psi.. I have 26 on the charger and 22 on motor and drive at sea level so I should see about 6 psi I have understand.. or may I have something wrong with my gauge? Can anyone help me. Thanks
rxrider
Jan-Ove Pedersen
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You may get hold of another boost meter to verify.
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TurboJamie
TY 4 Stroke God
Last I heard people used 26 and 24 tooth sprockets not 22 but I might be wrong. 24-24 gets you close to 7 psi at sea level.
To be honest you should check your boost gauges, if you want to run pump fuel anways by my calculations you should be closer to 10 psi. Are you using a cyberdyne digital gauge by chance? They are totally inaccurate and junk if you are it was out 5 psi on my nytro!!!!!!!!
I use a cheap VDO 0 - 15 psi gauge. About 20 bucks it has lasted the longest out of any gauge I have had on it. And yes I have verified it with 2 other boost gauges and I beleive it to be accurate.
Compressor speed calculations
26 divide by 22 x engine rpm x 12.7 = compressor speed
26/22 = 157595 @10500 = compressor over speed I beleive max is 150000
26/24 = 144462 @10500 = within your limits
24/24 = 133340 @ 10500
So to me you are probably acutally in excess of 10 psi.
Not sure on your elevation and knowledge level but the stock fuel pump can "barley" support 10 psi at sea level so please take that into concideration.
To be honest you should check your boost gauges, if you want to run pump fuel anways by my calculations you should be closer to 10 psi. Are you using a cyberdyne digital gauge by chance? They are totally inaccurate and junk if you are it was out 5 psi on my nytro!!!!!!!!
I use a cheap VDO 0 - 15 psi gauge. About 20 bucks it has lasted the longest out of any gauge I have had on it. And yes I have verified it with 2 other boost gauges and I beleive it to be accurate.
Compressor speed calculations
26 divide by 22 x engine rpm x 12.7 = compressor speed
26/22 = 157595 @10500 = compressor over speed I beleive max is 150000
26/24 = 144462 @10500 = within your limits
24/24 = 133340 @ 10500
So to me you are probably acutally in excess of 10 psi.
Not sure on your elevation and knowledge level but the stock fuel pump can "barley" support 10 psi at sea level so please take that into concideration.
JSH 68
Newbie
I ride the sled with 22 on the motor and 26 on the top and that would be 22 divide by 26 x engine rpm(10500) x 12.7 = 112834 on the supercharger.. and not the opposite.. I would check my boost gauges with another boost gauge. But I think I have leak somewhere in the system. Is there anyone who knows where it might be leaking?
I hope you all understand my English
I hope you all understand my English
rxrider
Jan-Ove Pedersen
- Joined
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- Lakselv - 70N & 25E
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- Snowmobile
- 2014 Phazer XTX, 2013 Phazer RTX, 2008 Apex RTX, 2007 Warrior, 2006 Attak
No problem JSH 68. I would suggest you to verify boost pressure with another gauge.
JSH 68
Newbie
I have now tried 3 different boost gauges and they all show me the same number (about 4.4 psi at 10600 rpm) so there is nothing wrong with the gauge. I also had every singel clamps, hoses and tube checkhed and rechecked and could not find leak of boost at all.
MPI tells me the boost numbers I see is within their tolerances and that is a reasonable boost numbers with that pulley combination. If that is so, there is a huge difference and a lot of horse power between 4.4 and 6.3 psi. Can anyone tell me are MPI right here, or are the boostnumber I have seen to low? Could it be something wrong with the charger itself. Do I have to accept that low numbers of boost?
Anyone who now something about it ??
MPI tells me the boost numbers I see is within their tolerances and that is a reasonable boost numbers with that pulley combination. If that is so, there is a huge difference and a lot of horse power between 4.4 and 6.3 psi. Can anyone tell me are MPI right here, or are the boostnumber I have seen to low? Could it be something wrong with the charger itself. Do I have to accept that low numbers of boost?
Anyone who now something about it ??
