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Old 08-22-2013, 08:46 PM   #1
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Default Does Usable RPM Increase In Modified Engines

I have always wondered about this, and I think I remember seeing a video on youtube where a Murnan modified (I think it was) .21 was dynoed and screamed to 50,000 RPM!

So, if an engine has been modified for drag racing, does the power increase with RPM? If so, approximately how much does the RPM increase?

Thanks
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Old 08-23-2013, 08:34 PM   #2
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Originally Posted by Z'Stein View Post
I have always wondered about this, and I think I remember seeing a video on youtube where a Murnan modified (I think it was) .21 was dynoed and screamed to 50,000 RPM!

So, if an engine has been modified for drag racing, does the power increase with RPM? If so, approximately how much does the RPM increase?

Thanks
One of my drag modified 35+21 engines makes its peak power about 1,500 rpm more than the stock one. Stock peak torque is around 38,000. Whereas the modified engine peaks around 39,500+. This is with an on road pipe.

There is no need to rev the engine to 50,000 rpm. I just posted that video because I thought people would enjoy seeing an engine revving like that. In on road racing we usually stay under 46,000 rpm on the race track. We need the additional revs past peak torque due to the long straights, and gearing options available.

Most drag racers use a boat pipe. The engines do not rev as high as when using an on road pipe, but they make crazy torque. That is good for going 132 ft. The boat pipe makes a super narrow powerband compared to a regular pipe. A drag race car clutch engages about 25,000 rpm, and they only rev to about 37,000. The boat pipe is only good for this very narrow powerband, but required due to the massive traction, and power required to go 132ft in around 1.5 seconds in a rail.

I'm not sure i understand your question exactly, but I hope this helps.
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Old 08-24-2013, 09:18 PM   #3
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Thanks, and you answered the question perfectly. Moreover, the explanation regarding the differences between the boat pipe and the on road pipe is very informative.

I have noticed that my on road pipe seems to make more power (car is faster for sure) than the Mac boat pipe, and I have did everything trying to tune the Mac so that the car is quicker and faster. I have custom made three different headers trying to get it to work just right because the car stays straight the entire 132 ft with it, where the on road pipe caused the car to move to the right when it shifts to second. Any ideas?

Thanks again.

Quote:
Originally Posted by Grinder View Post
One of my drag modified 35+21 engines makes its peak power about 1,500 rpm more than the stock one. Stock peak torque is around 38,000. Whereas the modified engine peaks around 39,500+. This is with an on road pipe.

There is no need to rev the engine to 50,000 rpm. I just posted that video because I thought people would enjoy seeing an engine revving like that. In on road racing we usually stay under 46,000 rpm on the race track. We need the additional revs past peak torque due to the long straights, and gearing options available.

Most drag racers use a boat pipe. The engines do not rev as high as when using an on road pipe, but they make crazy torque. That is good for going 132 ft. The boat pipe makes a super narrow powerband compared to a regular pipe. A drag race car clutch engages about 25,000 rpm, and they only rev to about 37,000. The boat pipe is only good for this very narrow powerband, but required due to the massive traction, and power required to go 132ft in around 1.5 seconds in a rail.

I'm not sure i understand your question exactly, but I hope this helps.
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