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bigdawg500 · April 13th, 2008, 08:20 AM

some feedback from my tuner.....looking for any feedback I can get

Hi Josh.

I will check. I can put an optical tachometer on the blower pulley and directly measure belt slip. It is a little more difficult to measure crank pulley slip, but I can investigate it if I don’t see any belt slip. This should tell me a lot.

I check all of the vacuum lines and fittings and everything looks ok. I even te into the power brake booster line to get a better signal and the reading was the same. The pressure transducer that I use in the shop is laboratory grade instrument and is calibrat and verifi. It is ok.

If I can’t find anything then I will start to dig further. I can log inlet pressure and temperature to the blower and blower outlet temperature. This will give me the blower efficiency. With that data I can plot the points on the performance chart and see if everything looks reasonable. This will also be a good measurement of any inlet pressure drop issues.

I fairly certain it is just belt slip on top end. Check out the data. This is not the final tune and the fuel is slightly rich. You can see the boost is falling off a bit on top end.

I attach a cobra file. One plot has a centrifugal blower and the other a roots blower. The tests are from 2 different Cobras, but you can see the torque shape from the higher boost at lower RPM. This is why I suggest to crank up the boost and limit the RPM. You will gain a pile of torque at the RPM in the mid range without a bunch of stress on the engine.

Again, our altitude is 1200ft. The boost will be lower than the cars at sea level.

Thanks for all of the input. I will see if I can get is straiten out.

Maybe it will stop snowing soon…..

http://i270.photobucket.com/albums/j...g?t=1208091226

April 13th, 2008, 08:20 AM	#18
bigdawg500 Enthusiast bigdawg500 is offline Join Date: Sep 2007 Posts: 84 Rep Power: 0	some feedback from my tuner.....looking for any feedback I can get Hi Josh. I will check. I can put an optical tachometer on the blower pulley and directly measure belt slip. It is a little more difficult to measure crank pulley slip, but I can investigate it if I don’t see any belt slip. This should tell me a lot. I check all of the vacuum lines and fittings and everything looks ok. I even te into the power brake booster line to get a better signal and the reading was the same. The pressure transducer that I use in the shop is laboratory grade instrument and is calibrat and verifi. It is ok. If I can’t find anything then I will start to dig further. I can log inlet pressure and temperature to the blower and blower outlet temperature. This will give me the blower efficiency. With that data I can plot the points on the performance chart and see if everything looks reasonable. This will also be a good measurement of any inlet pressure drop issues. I fairly certain it is just belt slip on top end. Check out the data. This is not the final tune and the fuel is slightly rich. You can see the boost is falling off a bit on top end. I attach a cobra file. One plot has a centrifugal blower and the other a roots blower. The tests are from 2 different Cobras, but you can see the torque shape from the higher boost at lower RPM. This is why I suggest to crank up the boost and limit the RPM. You will gain a pile of torque at the RPM in the mid range without a bunch of stress on the engine. Again, our altitude is 1200ft. The boost will be lower than the cars at sea level. Thanks for all of the input. I will see if I can get is straiten out. Maybe it will stop snowing soon….. http://i270.photobucket.com/albums/j...g?t=1208091226 __________________ TOYS - 05 Black Vert. Paxtonized!! 74 Chevy Nova 04 Ram Hemi 05 Yamaha RI 04 Yamaha Raptor ATV 02 Yamaha Raptor ATV 07 Yamaha Apex Attack 02 Yamaha SRX 700 00 Ranger Ski boat (not much use)