Is this turbo engine calculator right?

A

Anlushac11

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http://www.turbofast.com.au/tfcalc.html

When I enter in the following specs:

Bore: 3.71 (I have .040" overbore)

Stroke: 3.126

RPM: 5500

Ambient air temperature: 72

Number of cyl: 6

Engine volumetric efficiency: .39 (I based this off a V/E calculator using unported log intake air flow of 129cfm, 203 cid, 5500 rpm)

Boost Pressure: 16lbs boost

Compressor Efficiency: 70%

Water temp: blank (Wont let me input, for water air intercooler? )

Intercooler Efficiency: 70%

The calculator says that I should be making about 178hp and 169 ft lbs torque and turbocharged cfm would be about 231cfm.

I am surprised that the horsepower is so low that even with turbo the engine wont make 1hp per cubic inch?

I was also surprised that the torque would be less than the horsepower. I was under impression, however uninformed, that turbo engines usually make more torque than horsepower.

If this is correct then my engine will make no where near the goal I was hoping for. Was hoping for 300hp/300ft lbs but was expecting in my minds understanding a more "realistic" 250hp and 285ft lbs

If this is true only way to make decent power is to get the aluminum head which I dont see happening any time soon as its teasingly just outside what I can afford.

Even when I enter data using stock out of box aluminum head I show V/E of about .65 and about 296hp and 283 ft lbs torque. That would be close to my goal.
 
Hard to say whether it's right or not in an absolute sense, but it's probably close to right for the numbers it's given... :)

Bad flow and low V/E are going to significantly reduce your power making potential. Turning up the boost will effectively increase flow (though it's diminishing returns) but won't affect the engine's efficiency. You may be able to address both with some porting and the correct cam, but I think hitting 1hp/ci without insane boost pressures is going to be tough given the restrictive design you're working with. Production forced induction engines only crept over the 1hp/ci mark in the '80s using modern (at the time), mostly multivalve heads and better-than-carb'd engine management.

As far as hp/torque ratio, remember V/E (and torque) changes with engine speed. You will probably find hp drops and torque increases if you redo the calculations at a lower engine speed, perhaps 2500 or 3000rpm when the engine is running more efficiently. 5500rpm on a 2v/cyl engine is probably approaching ragged edge on a streetable cam.
 
Anlushac,

I like the Java turbo map calculator on that site better because it will also give you more points and you can see where your airflow fits on a given turbo map.

One thing you might have done wrong, is I believe you have to use centigrade for your air temp.

You can theorize and calculate all you want. I would go by what has actually been done. I think you're calculating the volumetric efficiency of the log head too low because if I reverse calculate what I have actually done, it has to be higher than what everybody says. Of course, I'm talking about the late model log heads, not the dog 60's small round log. The fact is I have time slips from 2 different drag strips - low 10s to 9s with 136-137 mph and a call out of 139. You simply cannot run that kind of mph with a 66 coupe without making around 400hp. The .96 turbo housing I was using was too large. I could only get 8 lbs boost in 1st gear. It would creep up to about 15-16 by high gear (and yes, I checked the gauge). The cam was a solid lifter - 266 deg advertised, 450 lift. The head was a 74 with stock 1.68 intake valves and larger 1.470 exhaust valves. Just pocket porting under the valves and opened up the chambers to unshroud the valves. I was blowing through the single 1.75 carb opening. Your biggest issue is controlling detonation with these engines. You'll definately need methanol injection. Should be a lot easier with today's wide bands. I had to guess and I think I was wrong.

Will and Kelly made pretty decent hp with the log, of course not as much as with the aluminum head. I think we've also already established that the 200 will make the same hp as a 250, just at a higher rpm. Mostly because of the log.

As I remember, Linc didn't do too bad with a totally stock head and blowing through a one barrel. Yes he ran higher boost, but he was handicapped by no cam and no cleaning up of the valve pockets and wore out valve springs. Just do the best you can and have fun with it.
 
Anything the 200 makes will be better than my last couple of Foxes which were 3100lb convertibles with 90hp 2.3L's :rolflmao:

I have had a couple of 79 Turbo Capri's and a 79 Carb turbo Mustang. Those were rated at 145hp and weighed about 2779lbs for the Capri's, never weighed the Mustang. My Coupe is stripped out in places so it will weigh less.

If I can get 178hp thats still comparable to a '84 SVO's 175hp but I will have as good gearing and better suspension.

Im trying to get the Aluminum head.
 
You input the temp in °F you needed to use °C
Your VE number is far, far too low. Try rerunning the turbo calculator at zero boost and vary the VE to get to the stock HP rating. That will put all your numbers on the same basis
 
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