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Discussion Starter #1
I'm trying to avoid this looking like one of those newbie bench-racer questions. We use different multipliers for estimating flywheel hp from rwhp on the dyno for stick cars and auto tranny(locking) cars. But what about non-locking auto trannys like the C4?

Today we tuned my 4.6L 3-valve Mustang and got 850.4 rwhp / 773.7 lbs torque. It has some more in it but we stopped there until we can get it on the track and shake it down some. That was through a C4. What do you suppose flywheel hp might be through a C4? I know it doesn't matter. Its just a number and its on the dyno just for tuning. Just curious.
 

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Discussion Starter #3
I cant answer your question but that thing makes good power and torque. Blower or turbo?
Twin 67 turbos. I'm new to turbos on my own car. 2000 Mustang GT. 4.6L (281 c.i.) 2008 3-valve heads. All built up. Street legal so I can drive it in the True Street classes. It was a twin screw (Kenne Bell 2.8 Mammoth) before this. Trying to get used to the difference between instant boost and this spooling up business!
 

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Converter and rear end will play a big part in how much you loose. Depending on how far from the stall of the converter your peak power is and the size of your converter will play with the % lost. Bigger rears such as 9 inch and danas will cost you more. I would guess your losing about 20-25% in the drivetrain, would put the flywheel hp somewhere between 1025 and 1050. Different stall converters and rears will raise or lower the number.

My street car with an 8 inch converter and ford 9 inch rear was 28% at 5800rpm
 

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Converter and rear end will play a big part in how much you loose. Depending on how far from the stall of the converter your peak power is and the size of your converter will play with the % lost. Bigger rears such as 9 inch and danas will cost you more. I would guess your losing about 20-25% in the drivetrain, would put the flywheel hp somewhere between 1025 and 1050. Different stall converters and rears will raise or lower the number.

My street car with an 8 inch converter and ford 9 inch rear was 28% at 5800rpm
850.4 rwhp with 25% drivetrain loss = 1133 flywheel hp. 20% loss is 1063. (850.4/.75 = 1133.87, or 850.4 / .80 = 1063)
 

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Poppy what does that tach going down the road? Is the C4 going to survive?
 

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We have used as a "general idea" about 16 percent for manual and 19 percent for automatic's when dealing with frictional hp loss through the drive train. As you mentioned, just numbers and rough estimates..........
 

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Poppy what does that tach going down the road? Is the C4 going to survive?
I don't really street drive much. I drive it to the strip (Tulsa) some since it is only 10 miles. I have a 3.55 rear gear so it is OK. My C4 is a PA ProMod model with protree t-brake. Pretty solid I think.
 

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Discussion Starter #10
Apologize. Was doing the math in my head.
Didn't mean to sound criticizing. No apology needed. Also, can you say more on the gap between stall speed and peak horsepower? I am having my converter re-stalled for about 4800 which will get me to about 11-12lbs boost for launch. It peaks hp probably around 6600-6700. Right now it t-brake stalls at about 3700 since the converter was for a twin screw s/c which had instant boost. That's not enough for the turbos though. It's launching like a school bus right now.
 
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