This is the results from the turbo airboat motor I've been working on. We struggled with the boost controller all afternoon and never really got it under control. Furthermore, it would always reach peak boost early, then lose 2 psi. The numbers listed below are based on boost@peak hp. Here's the numbers we got:

7 psi: 590 hp at 5500 rpm, 650 ftlb at 4200
10 psi: 690 hp at 5400 rpm, 770 ftlb at 4200
12 psi: 770 hp at 5500 rpm, 785 ftlb at 4200
14 psi: 800 hp at 5500 rpm, 906 ftlb at 4500
15 psi: 860 hp at 5300 rpm, 930 ftlb at 4700
18 psi: 929 hp at 5400 rpm, 1049 ftlb at 4500
?? psi: 929 hp at 4600 rpm, 1070 ftlb at 4500 (backfired and run aborted)

Yes, we beat the poop out of it today on the dyno. I quit counting when we hit 30 dyno pulls. I really think that last pull would've broken 1000 because the hp curve was rising exponentially when it backfired. Since the customer only wanted 750, he pulled the plug on our playing. Can't say that I blame him. . .

At 14 psi boost, backpressure was 22 psi. At 18 psi boost, backpressure was 26 psi. Not bad for a T-4 on a 377.

For completeness:

377 cid 4.125" bore x 3.48" stroke, bowtie block, 8.5/1.
Ported GM FastBurn heads with 2.02/1.625 valves (Inconel exhaust valves)
230/230 - 114 .590"/.590"
Victor Jr.
CSU 750, CSU hat
Aeromotive 11101 pump and 132-02 regulator
T-76GTS turbo and Precision "750 hp" air/air intercooler

Many thanks to Jose (JZ 97 SS 1500) at ForcedInductions and Kevin at CSUcarbs.

Mike

 

NICE!!. I know one thing, I sure as hell dont want to be on that airboat. Those things are fast enough with just a 350 small block

 

have you got any pics of this thing on the dyno???

looks amazing!

thanks Chris.

 

No pic's on the dyno, though you can see the layout here:

http://www.getonitracing.net/forums/...r=asc&start=30

BTW, I am NOT the guy with the welding goggles on. . . goofy @ss friends. . .

Mike

 

The engine shop called me today to tell me that they went back over the rockers and found 2 VERY loose. He described it as "those 2 valves were barely opening". Hmmm. . . I guess 930 hp isn't too bad for an 850 hp fuel pump, a 750 hp intercooler, and 7.5 cylinders. . .

Mike

 

With only 4500rpm pulls, their is still plenty left. Also the backpressure looks good since their is so little exhaust and the pulls are relatively low rpm. As you pull that engine closer to 6000-6500 the BP will rise fairly quickly. I imagine though he will probably keep the rpms low.

Jose

 

Wow that is some major HP. Congrats

 

Awesome numbers guys!!! funny what a turbo can do to wake up a small engine...=)

 

is that on an engine dyno? And who the hell is nuts enough to run that in a boat

 

I'm sure Jose would.....lol, and obviously this boat dude is crazy.

 

Im with you...... i take it its a engine dyno also.....

 

I'm going to go out on a limb and guess this boat wasn't strapped to a DynoJet guys.

 

Why are they keeping the RPMs so low to begin with? Doesn't that sorta defeat the idea behind a large bore/short stroke engine?

 

ya never know lol...im sure theres a water dyno somewhere...question is how the **** do you strap it down

 

so what the secret to this thing making sooo much power at thoes low revs and not that much boost??

also did you guys build the engine???

can we have a full list of parts please??

thanks Chris.

PS i really want one!

 

The combo was healthy because the piping was not compromised by the limits of an engine bay. The headers are mid-length equal-length 1 5/8" -> 1 3/4" stepped. All the piping uses long-radius bends and the downpipe is 3.5" with a very large (no backpressure) dyno muffler. The straight run of piping going to the turbo is about 3 ft. long which makes the turbine more efficient. Heads flow well, as does the Victor Jr. intake and the huge cone style air filter.

We did build the engine as well as the turbo setup.

Full list of parts:
Bow-Tie block, 4.155", splayed billet 4 bolt mains
Callies 3.48" crank
Oliver 6" rods
JE pistons for 8.5/1 compression
Ported GMPP Fastburn heads, 2.02 intake, 1.625 Inconel exhaust valves
165# seat pressure
230/230 - 114 roller cam with .590"/.590" lift
Port-matched Victor Jr.
CSUcarbs Holley 750, Aeromotive A1000 pump and 132-02 regulator
T-76GTS, .96 A/R
Precision "750 hp" air/air intercooler (30" x 12")
TurboSmart 44mm wastegate
TurboSmart Megasonic(?) BOV

By the way, guys, all the pulls except the last one were made to 5500 rpm. Only the last one was aborted early due to the backfire.

I had some more time to discuss actual intended use with the customer. He only wants the power for when he gets stuck. He says that his current 540 cid Big Block has enough power to make the boat porpoise uncontrollably.

Mike

 

Stuck? I have rode in an airboat that would flat out fly on dry ground. It only had about 425 hp. Is he going to run some sort of under/overdrive for the prop? The pitch on that prop must be unbelievable.I do know that mud will pull them down considerably. I am jsut wonderiing if this is a little bit of overkill, though. I can't see that a 540" bbc would not have the power to spin the prop at what ever speed that he needed. I am by NO means an expert on airboats though. Good luck, and I hope the owner is pleased with the outcome, I am sure he will be.

 

Thats just sick

 

That's just the problem. Sometimes thick mud can act like a big suction cup on the bottom of the boat. Also, apparently there are certain types of grasses or weeds that stick to the bottom of the boat.

His prop is carbon fiber with adjustable pitch.

 

Mike actually the wastegate is a JGT 44. Better then the Turbosmart....new design