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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > N54 Turbo Engine / Drivetrain / Exhaust Modifications - 335i > Cobb AP Stage 1 + Napkin math!



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      04-04-2013, 04:15 AM   #1
///Macht
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Cobb AP Stage 1 + Napkin math!

Getting closer and closer to pulling the trigger on a Cobb tune, and I've just been fiddling around with some napkin math in order to help predict potential power gains. Just want to make sure I'm on the right track.

I've searched around, and the assumption I've found is that (according to Terry's past posts) a stock 335i will see between 270 and 280 rwhp on a DynoJet. I chose to use 270 as my base so as to underestimate rather than overestimate. So, if I'm sitting at 270 rwhp completely stock, and you adjust for drivetrain loss and convert that to bhp (+15%), I'd be sitting at around 310 bhp, give or take.

According to Cobb's website, a stage 1 aggressive tune (with no additional modifications) should see about a 24% increase in horsepower. A 24% increase over the stock 270 rwhp is about 334 rwhp (384 bhp). Does any of this sound right? I don't have access to a dyno, so I wanted to play around and guesstimate using different sets of numbers, and what I have here sounds pretty good. My endgame is over 400 bhp, so 384 after a Cobb tune sounds pretty worth it, just want to check my math!
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      04-04-2013, 06:55 AM   #2
JStang
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Quote:
Originally Posted by ///Macht View Post
Getting closer and closer to pulling the trigger on a Cobb tune, and I've just been fiddling around with some napkin math in order to help predict potential power gains. Just want to make sure I'm on the right track.

I've searched around, and the assumption I've found is that (according to Terry's past posts) a stock 335i will see between 270 and 280 rwhp on a DynoJet. I chose to use 270 as my base so as to underestimate rather than overestimate. So, if I'm sitting at 270 rwhp completely stock, and you adjust for drivetrain loss and convert that to bhp (+15%), I'd be sitting at around 310 bhp, give or take.

According to Cobb's website, a stage 1 aggressive tune (with no additional modifications) should see about a 24% increase in horsepower. A 24% increase over the stock 270 rwhp is about 334 rwhp (384 bhp). Does any of this sound right? I don't have access to a dyno, so I wanted to play around and guesstimate using different sets of numbers, and what I have here sounds pretty good. My endgame is over 400 bhp, so 384 after a Cobb tune sounds pretty worth it, just want to check my math!
Sounds about right. My Stage 1 dyno'd at 318 whp which seems like forever ago. You will not be disappointed in the flash. The only thing that will disappoint you is realizing that you didn't do it soon enough.
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      04-04-2013, 08:42 AM   #3
///Macht
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Were you running stage 1 with no additional modifications? Right now, I have an intake and a Cobb AP on my list, followed by downpipes and an FMIC (a little further down the road). The downpipes and FMIC are a maybe, as of now. If Cobb and an intake alone provide enough power, I don't see myself having to go any further.
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      04-04-2013, 09:28 AM   #4
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Quote:
Originally Posted by ///Macht View Post
Were you running stage 1 with no additional modifications? Right now, I have an intake and a Cobb AP on my list, followed by downpipes and an FMIC (a little further down the road). The downpipes and FMIC are a maybe, as of now. If Cobb and an intake alone provide enough power, I don't see myself having to go any further.
Lol that’s what everyone says, when I got my current car I had planned on leaving it bone stock. Your goal of 400bhp will soon become a goal of 400whp.
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Last edited by 135Pats; 04-04-2013 at 09:31 AM. Reason: Correcting my apparently 3rd grade level spelling
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      04-04-2013, 10:13 AM   #5
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Quote:
Originally Posted by ///Macht View Post
Were you running stage 1 with no additional modifications? Right now, I have an intake and a Cobb AP on my list, followed by downpipes and an FMIC (a little further down the road). The downpipes and FMIC are a maybe, as of now. If Cobb and an intake alone provide enough power, I don't see myself having to go any further.
yeah right

I thought that as well, ended up going FBO + meth, then getting protuned for that +E85...

sold everything , bought an E92 and it already has stage2+ (stock mods, though drive map, car likes it better for some reason). I'm going to tune it myself for E40
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      04-04-2013, 10:14 AM   #6
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Quote:
Originally Posted by ///Macht View Post
Were you running stage 1 with no additional modifications? Right now, I have an intake and a Cobb AP on my list, followed by downpipes and an FMIC (a little further down the road). The downpipes and FMIC are a maybe, as of now. If Cobb and an intake alone provide enough power, I don't see myself having to go any further.
The only mod at the time of that dyno was the stage 1 flash and Dinan free flow exhaust which adds little to nothing.
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      04-04-2013, 11:45 AM   #7
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Napkin math is pretty good. The typical gain is about 60WHP with just a tune only. Give or take ~10 for octane and other exterior conditions.

Oh and yea every one of my customers says they are done at a tune, if that was the case I would be out of business. You will want more
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      04-04-2013, 12:02 PM   #8
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Quote:
Originally Posted by Jeff@TopGearSolutions View Post
Oh and yea every one of my customers says they are done at a tune, if that was the case I would be out of business. You will want more
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