7.8 vs 9 compression ratio

[Lowell Foo]

[Lowell Foo]

Exact same turbo, header, o2 housing, downpipe, cams.  Stock short block with balance shafts vs. 9:1 built motor, no balance shafts.  474whp dyno also had a ported stock intake manifold and SS valves.

[Marke Bailey]

40 whp sounds like its worth it to me... hahaha

[Jordan Kruger]

So the stock block made more?

[Lowell Foo]

Stock block is the solid line.  431 vs 474.  The 9:1 motor should make a little more torque down low, but that might be attributed to starting the pull 500rpm later. 

[KevinBuckham]

Are you detonation limited on both runs?  If you aren't detonation limited I would expect the higher CR to have more power, but this is the *first* time I've seen evidence back to back.  Pretty darn cool! 

Performance books are full of theoretical curves, but it's great to see it on our cars.

I assume you had less ignition timing on the second motor?  In theory the higher CR should need less ignition timing as well, but it's possible you might get away with the same ignition timing in either situation but the higher CR motor the ignition timing is closer to MBT.  (For example it's possible that the 7.8:1 motor needs more ignition timing but it's impossible to give it what it needs on 94 octane because of the potential for detonation increases if you delay the spark.)

[Lowell Foo]

Both cars with methanol spray, so MBT was reached.  Wouldn't have it any other way on my cars.

Ignition timing I'm not sure about, but I would say within 1 or 2 either way between cars.  It's pretty easy to be 1 degree out when setting the CAS.  These two dyno pulls were done a few years apart as well.

[KevinBuckham]

Well I think you just sold us all on building higher compression motors.

[Robert Vorley]

I love dyno plot comparisons!

It would be neat to see a 10:1.

Who's running 10:1?

[Zach Holt]

I love dyno plot comparisons!

It would be neat to see a 10:1.

Who's running 10:1?

when EI stoped fucking me around ill pick up my car and see what she does. Ive been looking forward to it for over 2 years

so once its out of hawk ill share what she does lol

[Ryan Coft]

I love dyno plot comparisons!

It would be neat to see a 10:1.

Who's running 10:1?

I did, but it was stroker and different setup completely. Apples to oranges comparison

[andrew volcz]

As will zachs? 2.4L 10:1 setup

[John Hartman]

great comparison

[Lowell Foo]

Made a few changes and made 449/406 this morning.