Theoretical Boost Question

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Theoretical Boost Question

Postby Ole' Blue » Sun Sep 19, 2010 3:09 pm

I've been wondering how much power I'm driving around with now, and there's limited (and expensive) dyno action here in Anchorage. So I have a theoretical question.
All other things being equal, and without a wastegated exhaust housing, can boost pressure be used to determine horsepower? For example, 2 identical trucks with identical mods (breathing mods, same turbo, 366 spring, etc.), can the boost pressure produced be used to compare the 2 trucks power? If one truck is known to be 300hp and produce 35psi boost, can you infer an approximate horsepower on the other truck?
I know it's kindof a strange question, but it seems to me that we could make rough estimations of power based on similar trucks performance. What do you guys think?
'93 W250 Ext. Cab Flatbed Getrag. Tach, boost, EGT gauges. Fuel Screw bottomed out. 366 spring. BHAF. Tims Cooler Tubz. 3" dp to 4" exhaust. Work in progress.
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Re: Theoretical Boost Question

Postby Richie O » Sun Sep 19, 2010 3:18 pm

If everything about the trucks were the same including tranny, tires, gears and all engine parts then I would say it will be close. When things differ from each it will start to change. My 89 is around 35 psi boost with an auto at 297hp when my 93 with a stick is at 301hp at 45 psi.
1989 W250 727, 3.07 L/S, S300, P/S Intercooler, Stans exaust, Pump adjustments, 127k miles,297 hp
1993 W250 extended cab, rag, 4.10 l/s, 6x16's, HTT 62/71/14 piston l/p, Isspro EV series tach, fuel pressure, boost, oil pres, water temp, volt, pryo, 132k/ 301 hp
1992 W250 with NV4500, 3.54's, 16cm 60mm GDS H1C, ground stock cone, Isspro tach, pryo, boost, fuel pressure, slow, rusty, dented,180k
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Re: Theoretical Boost Question

Postby Ole' Blue » Sun Sep 19, 2010 4:22 pm

Cool, thanks. Our 93's are pretty similar, other than your 6x16's and the GDS upgrade. How do you like the GDS? Where's your fuel screw at? 6x16 seems like a large injector for your HP range, are you always watching the EGT gauge? Do you ever tow with that truck?
'93 W250 Ext. Cab Flatbed Getrag. Tach, boost, EGT gauges. Fuel Screw bottomed out. 366 spring. BHAF. Tims Cooler Tubz. 3" dp to 4" exhaust. Work in progress.
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Re: Theoretical Boost Question

Postby dpuckett » Sun Sep 19, 2010 4:42 pm

General rule, up to roughly 300hp, is 10hp per 1psi boost. I.E. 30psi boost converts to 300hp or thereabouts. Of course, this assumes near stock injectors and turbo, maybe some pump tuning.

If you have cranked on your fuel screw, still have a baby H1C, and run 45psi, you are probably not at 450hp.

DP
His- 93 W250 club cab LE, auto to Getrag conversion, piston lift pump, 3.54 LSD. 400k+
Hers- 04 QC 4x4. Built auto, Triple Dog, Air Dog. Funny Round truck that aint so quiet.
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Re: Theoretical Boost Question

Postby Richie O » Sun Sep 19, 2010 6:19 pm

Ole' Blue wrote:Cool, thanks. Our 93's are pretty similar, other than your 6x16's and the GDS upgrade. How do you like the GDS?I guess its ok. Never drove the truck whith the stock set up. I put it on while I had the truck tore down Where's your fuel screw at? 4 full turns out from max 6x16 seems like a large injector for your HP range, are you always watching the EGT gauge?There is no sense to watch it. Its always pegged. Do you ever tow with that truck?Once and a while just for giggles
1989 W250 727, 3.07 L/S, S300, P/S Intercooler, Stans exaust, Pump adjustments, 127k miles,297 hp
1993 W250 extended cab, rag, 4.10 l/s, 6x16's, HTT 62/71/14 piston l/p, Isspro EV series tach, fuel pressure, boost, oil pres, water temp, volt, pryo, 132k/ 301 hp
1992 W250 with NV4500, 3.54's, 16cm 60mm GDS H1C, ground stock cone, Isspro tach, pryo, boost, fuel pressure, slow, rusty, dented,180k
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Re: Theoretical Boost Question

Postby SNOOT » Sun Sep 19, 2010 8:01 pm

ME ME ME How about 60PSI of boost.... lol
1993 W350
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Re: Theoretical Boost Question

Postby lectro_static » Sun Sep 19, 2010 8:58 pm

Look into a G-tech you can buy them from summit racing, jegs, ebay etc and they are fairly close and it just plugs into your lighter socket so its easy to change trucks to check your buddies
soon to be 1985 Chevy crew cab with 93 cummins running gear
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Re: Theoretical Boost Question

Postby SNOOT » Sun Sep 19, 2010 9:10 pm

lectro_static wrote:Look into a G-tech you can buy them from summit racing, jegs, ebay etc and they are fairly close and it just plugs into your lighter socket so its easy to change trucks to check your buddies



Or you can use your Droid cell phone...


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Re: Theoretical Boost Question

Postby Ole' Blue » Sun Sep 19, 2010 11:03 pm

Hahaha. I love this forum. Thanks guys. I appreciate the responses (even the sarcastic ones!). So with my setup (stock sticks and h1c), I'm running about 29-30psi boost. You think I'm over 250hp? I was guessing 230-240, so I'd be happy with anything over that. I have the DDP stage 1 (40hp) sticks to put in, and I'm trying to guess about what power range I'll be in (for turbo mod reasons).

"are you always watching the EGT gauge?There is no sense to watch it. Its always pegged."

haha. I'm terrified of anything about 1200F for anything more than 3 seconds... I told everybody my truck was a marvel of engineering for longevity, I wouldn't want to prove myself wrong! :shock: Thanks guys
'93 W250 Ext. Cab Flatbed Getrag. Tach, boost, EGT gauges. Fuel Screw bottomed out. 366 spring. BHAF. Tims Cooler Tubz. 3" dp to 4" exhaust. Work in progress.
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Re: Theoretical Boost Question

Postby ahale2772 » Mon Sep 20, 2010 1:57 pm

wish that was true Dpuckett, id be making 450 hp out of my stock hc1 :yuck: ....its a marvel my turbo is still in one piece
84 CCLB W350 project
94' W350 Dually, Diesel, Auto 1080HP/1980FTlbs
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Re: Theoretical Boost Question

Postby PToombs » Mon Sep 20, 2010 6:17 pm

Note to self, if ahale is selling a turbo, don't buy it. :lol:
pete

Just enough power to break everything behind the crankshaft.
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Re: Theoretical Boost Question

Postby dpuckett » Tue Sep 21, 2010 3:39 pm

I forgot one caveat- the boost has to be within the turbo's efficiency map- sorry ahale. And this was about 10 years ago, when 250-280hp was pushing it in a 1stGen.
His- 93 W250 club cab LE, auto to Getrag conversion, piston lift pump, 3.54 LSD. 400k+
Hers- 04 QC 4x4. Built auto, Triple Dog, Air Dog. Funny Round truck that aint so quiet.
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Re: Theoretical Boost Question

Postby Douglas » Tue Sep 21, 2010 5:10 pm

hey-Hey!!!,
Compressor efficiency as well as intercooler temperature drop are quite important. At the same pressure, going from 400F to 150F only makes the cooler stuff 25% more dense. So depending on where on the map you are makes a difference on how much more energy is going into heating the air( beyond the compressive/adibatic effects).
cheers,
Douglas
1990 D250, NV5600, 16cm housing and PAC brake, Powr-Lok'd 3.07's, HX35...IC next

1991 D250, 727 and 16cm H1C.
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Re: Theoretical Boost Question

Postby ahale2772 » Tue Sep 21, 2010 7:35 pm

haha, yeah my poor hc1, i get what yor saying dpuckett, my buddies IDI FURD makes 6psi, he got real mad when i suggested he had a 60 horse motor :lol: the efficiency map of a turbo is clearly the best way to judge its performance and how it will react in ones setup.....no if it wasnt so dang hard to read them :?:
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Re: Theoretical Boost Question

Postby Diesel Dawg » Wed Sep 22, 2010 12:05 am

IDI ford with 6psi. won't Dyno a whole lot more than 60hp at the wheels :P :P
92 D-350 reg. cab,dually,c.t.d.,auto,3.54s,fuel screw 2+turns,smoke screw3 turns,star wheel all the way down,,B.H.A.F.,,gauges,DennyT stage 2 pin,366 spring next!!!
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