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Author Topic: Inline-four crankshaft  (Read 129231 times)
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Jack Gifford
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« Reply #375 on: April 15, 2018, 01:22:50 AM »

It went... tediously and stressfully. I had never dyno'd an engine before; the shop had never run such a small engine; the mounting and driveline hardware that I had prepared beforehand needed rework (different dyno 'cart" than the one I had measured); the dyno computer and my crank sensor weren't "happy"; zoomies had to be modified to connect to the cell's vent duct; etc.; etc. On the first startup in the dyno cell I forgot hearing protection and was literally deaf for the next 24 hours. Adding to the stress was the hour and a half commuting to the shop each of four days, plus the cost- $85/hour/man, usually two guys working with me.

Positives: engine is still in one "lump"; dyno data for pressures (bottom end oil, top end oil, fuel) and coolant temperature were fine.

Negatives: first attempted full-throttle "sweep" (3,000-7,000 RPM, 600 RPM/sec) ended quickly (about 3.5 seconds in, 4,430 RPM) with a bang (not severe enough to blow the burst panel).

The manifold pressure data clearly identifies the culprit. My guess at blower drive ratio (80% of crank speed) was totally "out of the park". This billet 14-71 is WAY more efficient than I knew. I was shooting for no more than 30 PSI of boost at around 9,000 RPM; the dyno recorded 25 PSI boost at 4,300 RPM! shocked Since the fuel setup was configured for a slower rise in boost, the mixture was going rapidly lean.

A quick engine check showed compression low on two cylinders, so I need to pull the head and hope it's repairable.

« Last Edit: April 15, 2018, 01:57:05 AM by Jack Gifford » Logged

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jacksoni
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« Reply #376 on: April 15, 2018, 10:33:44 AM »

Shucks, Jack, sorry to hear. I have no experience with supercharges but seems a 14-71 is awful big for a 3 liter. They put them on big V8's don't they? Anyway, hope any damage is small. Have you had anyone really versed in the big blowers help with set up, pulley ratios etc? ( sorry if that be you, not meaning to put anyone down)
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Jack Iliff
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 G/GMS-178.835 2010
wobblywalrus
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« Reply #377 on: April 15, 2018, 03:12:47 PM »

Would a manifold pressure release valve be a fix?
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Milwaukee Midget
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« Reply #378 on: April 15, 2018, 03:51:05 PM »

the shop had never run such a small engine;

I feel your pain there.

Orphan and custom engines are always a PITA getting properly hooked up to a dyno.

In most shops, you can get an LS or BBC bolted in and ready to go in an hour.  It's rare to find a shop that will tackle anything but a common drag motor, or a roundy pounder, and tougher to find a dyno operator with the patience and experience to even touch a combination like this. 

But when you do get this dialed in, it is going top be so much more impressive than any Bow-tie.

It's always better to find the problems before you run it on the track:  It's quicker to diagnose, you've got easier access to the problem not having to pull it out of the car, and you're not under the pressure of trying to get it together before the event closes down.

With the engine back in the shop, you can fix it on your own terms.

Sometimes, a dyno failure is a blessing - a track failure is always a headache.

Press on, Mr. Gifford.  I'm looking forward to seeing this thing go.



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"Problems are almost always a sign of progress."  Harold Bettes
Well, I guess we're making a LOT of progress . . .  rolleyes

We are NOT rebuilding . . . We are reloading.

GOD SAVE MG - The Queen can take care of herself!
Jack Gifford
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« Reply #379 on: April 15, 2018, 11:16:33 PM »

... Would a manifold pressure release valve be a fix?...
No. Besides at each port, fuel is injected above the blower.
There's no need for dynamic pressure relief in a Roots-blown engine, once the correct configuration is established (i.e., the dumbass who set it up should have better researched the blower characteristics)! embarassed

jacksoni- I'm not aware of anyone familiar with a huge blower on a small engine. I tend toward less-travelled paths (at my own peril). In this case, I want to explore a means of reducing heating of the intake mixture without resorting to an intercooler system. Maybe I'll learn something, maybe not...
« Last Edit: April 15, 2018, 11:31:34 PM by Jack Gifford » Logged

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jacksoni
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« Reply #380 on: April 16, 2018, 06:44:48 AM »

..[/quote]jacksoni- I'm not aware of anyone familiar with a huge blower on a small engine. I tend toward less-travelled paths (at my own peril). [/quote]

Well, I have to say, I am personally familiar with this syndrome.  rolleyes wink
Keep at it!!
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Jack Iliff
 G/BGS-250.235 1987
 G/GC- 169.741  2009
 G/GMS-178.835 2010
bearingburner
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« Reply #381 on: April 16, 2018, 09:02:28 AM »

Experience is a good teacher though costly.
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POPS
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« Reply #382 on: April 16, 2018, 09:06:26 AM »

Jack,
We have the solution for cooling the charge.  Our atomizing nozzles will drop the inlet temperature 40 degrees.
Typical manifold temperature drops 20 degrees. 
Power gain for alcohol drag motors is 75 for roots and 85 for screw compressors.
You will see a 1.5 gain in boost, because the case will shrink faster than the impellers. Case will be cold to the touch.
Total EGT spread at WOT in the Flashpoint Streamliner is 35 degrees. 
POPS
Don Jackson Engineering
714-269-9645
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