Just 4fun, dyno run of the rebuild M20B25 in our FP car

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Daryl Lane
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Just 4fun, dyno run of the rebuild M20B25 in our FP car

Post by Daryl Lane »

Finally got it running it is an 85 BMW M20B25 six with a mix of older parts on it. This is not a killer HP engine but 67 more HP then our last engine.

176.55 HP at 6,600 rpm - the pull is from 3,000 to 7,500 in fourth gear. Hope to be out at El Toro on the 18th - still need to work on the brakes.

https://www.youtube.com/watch?v=rMrdh8F ... e=youtu.be
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Daryl Lane
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Re: Just 4fun, dyno run of the rebuild M20B25 in our FP car

Post by Daryl Lane »

Also we need help with exhaust/mufflers this thing is most likely currently above 100db's and not fun to be inside of for long runs. Any ideas or help will be greatly appreciated. Currently the system is two into one (2.5") at the flywheel, into an 18" long Cherry bomb glass pack and then into a 3"in 3" out Flowmaster hushpower muffler. We are currently too load for Qualcomm and maybe more.
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Mark DeShon
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Re: Just 4fun, dyno run of the rebuild M20B25 in our FP car

Post by Mark DeShon »

Sounds good! Talk to Toby Larsson. I believe he was running a Burns muffler on his (now Henry Bjoin's) FP car. I don't know the details, but it sounded good and was loud, but not too loud.
Mark D.
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Bill Martin
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Re: Just 4fun, dyno run of the rebuild M20B25 in our FP car

Post by Bill Martin »

This is the one recommended to me by tech support at DynoMax. Have two of them on my 505 bhp CP Mustang which doesn't even come close to max at San Diego. But I also have an X-pipe, which might do part of the silencing. It's also available in a 2.5", but you have to stay with the offset/offset outlets.

http://www.summitracing.com/parts/wlk-17229/overview/
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Daryl Lane
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Re: Just 4fun, dyno run of the rebuild M20B25 in our FP car

Post by Daryl Lane »

I agree Mark Toby should know some things about making this screaming BMW six's quiet. I hope to talk to him soon just need to find time.

Bill is that a filled muffler or like a flow master with plates inside it? I think it is a filled "S" inside?

Also I e-mailed the San Diego BMWCAA in San Diego and asked their requirements - they said 80db before 12pm and 92 after?
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Bill Martin
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Re: Just 4fun, dyno run of the rebuild M20B25 in our FP car

Post by Bill Martin »

It's a straight-through perforated tube with packing in the case. Part of what makes it a bit quieter are the two shallow bends at inlet and outlet.

They also have the muffler I think you're describing called the SuperTurbo. It's rated for lower horsepower levels, so must produce more back pressure.

The muffler I linked is the non-polished version of the Ultraflo which as I recall is rated for 1000 horsepower (maybe higher), meaning that backpressure stays below some limit. Even the 2.5" is rated that high, so I'd use that if sound level is your objective. I'm confident it will be quieter than the Hushpower, but if you're really over 100 now, I don't know if it will be enough.
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Jayson Woodruff
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Re: Just 4fun, dyno run of the rebuild M20B25 in our FP car

Post by Jayson Woodruff »

Daryl Lane wrote:Also I e-mailed the San Diego BMWCAA in San Diego and asked their requirements - they said 80db before 12pm and 92 after?
The Qualcomm contract is something like that, but they've got their numbers a bit wrong (especially in the morning).

dB is serious stuff in San Diego though. Don't go until you've got it figured out and quite like a street car.

Jay W
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Craig Naylor
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Re: Just 4fun, dyno run of the rebuild M20B25 in our FP car

Post by Craig Naylor »

Jayson Woodruff wrote:
Daryl Lane wrote:Also I e-mailed the San Diego BMWCAA in San Diego and asked their requirements - they said 80db before 12pm and 92 after?
The Qualcomm contract is something like that, but they've got their numbers a bit wrong (especially in the morning).

dB is serious stuff in San Diego though. Don't go until you've got it figured out and quite like a street car.

Jay W
SCCA self implemented sound rules over 2 decades ago at the Q to appease the powers that be, to quell sound issues from neighbors. This was before the before Lowes/Costco complex, or the apts to the north of the stadium were built. It actually came from complaints from homes on the hill above the south side of the I8. How they could differentiate Solo sounds from the drum of the traffic on the I15 & I8 are beyond me though.

The sup's used to list a before 11am, and after 11am sound rule. I believe that went away a few years ago. Currently it is 93dB for SCCA events. Friday night drags have no sound limit, BMW & other clubs may have different internal rules than SCCA.
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Daryl Lane
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Re: Just 4fun, dyno run of the rebuild M20B25 in our FP car

Post by Daryl Lane »

Thank you all again for the advise - at this point I am thinking two different back halves one for tracks one for Auto-x. are there low sound limits at EL Toro? I do not remember being told we were too loud there with the car - old engine.
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Craig Naylor
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Re: Just 4fun, dyno run of the rebuild M20B25 in our FP car

Post by Craig Naylor »

Daryl Lane wrote:... are there low sound limits at EL Toro? I do not remember being told we were too loud there with the car - old engine.
All SCCA events have a 100db limit unless otherwise limited lower. Currently we don't have lower limits at LA region sites, but that can always change.
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