[charlie66]

My PT6870 Precision turbo has the ability to deliver 1100 hp worth of air . Is there a way to figure out what rpm I will need to reach to take advantage of all this air with the 198ci 4 cylinder?

Thanks...

[Tom Vaught]

So your turbo is rated at 1100 hp worth of air mass.
1 pound of air mass basically makes 10 horsepower, so we should be moving 110 pound of air mass (MAX) thru the Turbo.
But then temp comes into play.

So we assume that your Peak HP is 1100
We assume that your air/fuel ratio is 11.5 to 1
We assume that your brake specific fuel consumption (BSFC) is .55
We assume that the charge temp coming out of your intercooler is 165 degrees or about double what ambient air temp is 80 degrees F.
We assume a head flow Volumetric Efficiency of .95
We assume a peak rpm of 7500 rpm
and finally we plug in your engine displacement of 194 CID

And the math say that about 55 psi of boost
115 lbs of air mass going thru the engine (due to the higher intake manifold temps)
and about 1440 cfm worth of air to get there.

So if you spin the engine to 8000 then you only need 48 psi of boost to get there.
So if you spin the engine to 8500 then you only need 45 psi of boost to get there.

So your poor little engine is most likely never going to run out of Turbo air flow capability with your 194 cid engine, Charlie.

Tom V

[JSPONT]

So your poor little engine is most likely never going to run out of Turbo air flow capability with your 194 cid engine, Charlie.


LOL,^^^^^ Build a V8 Show them all how its done!!

[charlie66]

Originally Posted by Tom Vaught

So your turbo is rated at 1100 hp worth of air mass.
1 pound of air mass basically makes 10 horsepower, so we should be moving 110 pound of air mass (MAX) thru the Turbo.
But then temp comes into play.

So we assume that your Peak HP is 1100
We assume that your air/fuel ratio is 11.5 to 1
We assume that your brake specific fuel consumption (BSFC) is .55
We assume that the charge temp coming out of your intercooler is 165 degrees or about double what ambient air temp is 80 degrees F.
We assume a head flow Volumetric Efficiency of .95
We assume a peak rpm of 7500 rpm
and finally we plug in your engine displacement of 194 CID

And the math say that about 55 psi of boost
115 lbs of air mass going thru the engine (due to the higher intake manifold temps)
and about 1440 cfm worth of air to get there.

So if you spin the engine to 8000 then you only need 48 psi of boost to get there.
So if you spin the engine to 8500 then you only need 45 psi of boost to get there.

So your poor little engine is most likely never going to run out of Turbo air flow capability with your 194 cid engine, Charlie.

Tom V

Thank you Tom !

Maybe some day you can show me how you figured that out. I would luv to know the math involved behind that ..

I had her out today revving to 6000 @ 37 psi. It was very angry motor to say the least.. I wont dare push it any more with out a steel crank...

Thanks again Tom!

[charlie66]

Originally Posted by JSPONT

So your poor little engine is most likely never going to run out of Turbo air flow capability with your 194 cid engine, Charlie.


LOL,^^^^^ Build a V8 Show them all how its done!!

I have something in mind don't you worry. Don't have to dough just yet though....

[charlie66]

Another thought.
If I turned the engine to 8500 rpms. I would think the H- beam Eagles with 2000 ARP bolts that are in it now would have to be replaced with something better. What rods would hold up at this level hp/rpms ?

[charlie66]

Also, being im having a crank made and may need better rods because of the rpms , would it be a good idea to take some stroke away so we can keep the block safer?

[Tom Vaught]

Originally Posted by charlie66

Another thought.
If I turned the engine to 8500 rpms. I would think the H- beam Eagles with 2000 ARP bolts that are in it now would have to be replaced with something better. What rods would hold up at this level hp/rpms ?

Carrillo Rads with CARR bolts are about as good as it gets for the normal racer but $$$
They will make any length you want as long as you can pay for the rods.
We have used their rods in a bunch of Dyno durability engines with prototype heads/valvetrains, etc.
We did not want a rod to fail and destroy the $$$ engine.

That being said, Oliver, Crower, and other American Rod Manufacturers can make whatever you need. The Eagle stuff was Chinese 30 years ago but was a good alternative to the Rubber rods or the more expensive 455 SD rods.

Tom V.

[charlie66]

I will look into the cost of all you mentioned. I like the Oliver rods, and that would be my choice if they will hold up for what im doing. What are your thoughts on going with a smaller stroke? Is there any gain in longevity with going that way??

[Tom Vaught]

4" stroke vs say a 4.25" stroke puts less stress on the crankshaft because of the shorter "lever arm" effect during the combustion stroke.

The smaller stroke makes also less torque due to the shorter lever arm which can be an advantage on a vehicle that does not have a great rear chassis set-up for drag racing.
Typically you will never really hurt anything if the tire/chassis is the weak link as far as putting the power to the ground.

Get the tire to hook and then you rip out the rear suspension of the vehicle like the Butler/Quillen Tempest did at Norwalk a few years ago to the tune of a 10K+ repair job.

If you had a Moldex Timkin Ball Bearing material crank then the crank would not be the issue. The rods or the block would be the issue. The 3.5"-3.6" stroke forged cranks I have will never be an issue as proven on the Butler and later Welter 440 cid engine even under high boost as the stroke is short vs a 4.5" stroke chinese crank.

Hope that helps, Charlie.

Tom V.

[Torment]

Shorter stroke good for the rod bolts too particularly during the non-combustion 4 stroke event... less piston speed.

I would not be overly worried about a good H Beam rod with ARP2000's at 8000RPM with a 4" arm, at least in a drag racing application that I'm accustomed to.

[Tom McQueen]

Were going to have CP/Carrillo make the pistons and rods for my build. Likely in a couple of months.
The Carrillos have an option sheet that takes some time to go thru. I've never even heard of half this stuff.

http://www.cp-carrillo.com/pt-3508-rods.html ....and then select Features.

[charlie66]

Originally Posted by Tom Vaught

4" stroke vs say a 4.25" stroke puts less stress on the crankshaft because of the shorter "lever arm" effect during the combustion stroke.

The smaller stroke makes also less torque due to the shorter lever arm which can be an advantage on a vehicle that does not have a great rear chassis set-up for drag racing.
Typically you will never really hurt anything if the tire/chassis is the weak link as far as putting the power to the ground.

Get the tire to hook and then you rip out the rear suspension of the vehicle like the Butler/Quillen Tempest did at Norwalk a few years ago to the tune of a 10K+ repair job.

If you had a Moldex Timkin Ball Bearing material crank then the crank would not be the issue. The rods or the block would be the issue. The 3.5"-3.6" stroke forged cranks I have will never be an issue as proven on the Butler and later Welter 440 cid engine even under high boost as the stroke is short vs a 4.5" stroke chinese crank.

Hope that helps, Charlie.

Tom V.

Tom , everything you have ever told me helped and thank you for that...

I'm not really worried about losing any torque power . It makes a lot as is now. Just want to be sure of whether or not going smaller stroke would be a worth while trade off for longevity verse lose of torque . Would much rather have a motor down on torque with a much longer life expectancy . looking for the right scope on this...

[charlie66]

Originally Posted by Torment

Shorter stroke good for the rod bolts too particularly during the non-combustion 4 stroke event... less piston speed.

I would not be overly worried about a good H Beam rod with ARP2000's at 8000RPM with a 4" arm, at least in a drag racing application that I'm accustomed to.

So right now I have Eagle H-beams with 2000 ARP's bolts. This motor is making over 200 hp per cylinder and im shooting for more with a bbc length and 3.75 stroke. Do you think the Eagles will handle this?

Thanks..

[charlie66]

Originally Posted by Tom McQueen

Were going to have CP/Carrillo make the pistons and rods for my build. Likely in a couple of months.
The Carrillos have an option sheet that takes some time to go thru. I've never even heard of half this stuff.

http://www.cp-carrillo.com/pt-3508-rods.html ....and then select Features.

Thank you.

Ill call them and see what they say for what im trying to do..

[Torment]

Originally Posted by charlie66

So right now I have Eagle H-beams with 2000 ARP's bolts. This motor is making over 200 hp per cylinder and im shooting for more with a bbc length and 3.75 stroke. Do you think the Eagles will handle this?

Thanks..

RPM creates the extensive loads when the crank/rod reverses the piston direction at TDC. Power on the other hand creates the compressive loads during the compression and power stroke. Rods are usually rated by HP alone... so I find that a little confusing. H beam rod designs are touted for their ability to hold up to higher compressive loads, I beam designs on the other hand for higher RPM. Different power adders, different fuels, how the engine sees load in the chassis - tire/converter/weight/tuneup/rod length/etc - all have an impact too. You're choice of turbo for a power adder is a good one, they have a reputation for being a little easier on parts at equivalent power levels. Your thoughts on a shorter stroke will help with compressive loads, but you'll likely want to spin higher RPM to offset so extensive loads will need to be accounted for.

Anyway... it sounds like you're specific output is pretty high, maybe higher than mine in terms of HP/CI and about the same in terms of HP/Cylinder - which goes to the compressive load side of the question. I've been running Manley H Beams with ARP2000's, 4.5" arm, shift at 7500RPM and through the beams 75-8000RPM. My brothers twin turbo 565CI, similar power/RPM, never had an issue with Eagle H beams in it. I personally race with others with 632's (4.75" arm) spinning 7500RPM and about 1600HP with nitrous - year after year. This isn't to say sometimes rods don't exit out the side... but I've seen the Oliver/Callies/Etc. rods go out the side just the same. Good machining, assembly and oiling is a must in all cases. Modest RPM's seem to help with durability too - but always at the sacrifice of power.

I'd never recommend buying something that isn't suited for what you're trying to do, but at the same time a person can break the bank buying what I call 'engine insurance' with the mindset they're going to have an engine that will never blow up. Doesn't always work out that way. Hope this helps even though it doesn't answer your question directly.

[charlie66]

Originally Posted by Torment

RPM creates the extensive loads when the crank/rod reverses the piston direction at TDC. Power on the other hand creates the compressive loads during the compression and power stroke. Rods are usually rated by HP alone... so I find that a little confusing. H beam rod designs are touted for their ability to hold up to higher compressive loads, I beam designs on the other hand for higher RPM. Different power adders, different fuels, how the engine sees load in the chassis - tire/converter/weight/tuneup/rod length/etc - all have an impact too. You're choice of turbo for a power adder is a good one, they have a reputation for being a little easier on parts at equivalent power levels. Your thoughts on a shorter stroke will help with compressive loads, but you'll likely want to spin higher RPM to offset so extensive loads will need to be accounted for.

Anyway... it sounds like you're specific output is pretty high, maybe higher than mine in terms of HP/CI and about the same in terms of HP/Cylinder - which goes to the compressive load side of the question. I've been running Manley H Beams with ARP2000's, 4.5" arm, shift at 7500RPM and through the beams 75-8000RPM. My brothers twin turbo 565CI, similar power/RPM, never had an issue with Eagle H beams in it. I personally race with others with 632's (4.75" arm) spinning 7500RPM and about 1600HP with nitrous - year after year. This isn't to say sometimes rods don't exit out the side... but I've seen the Oliver/Callies/Etc. rods go out the side just the same. Good machining, assembly and oiling is a must in all cases. Modest RPM's seem to help with durability too - but always at the sacrifice of power.

I'd never recommend buying something that isn't suited for what you're trying to do, but at the same time a person can break the bank buying what I call 'engine insurance' with the mindset they're going to have an engine that will never blow up. Doesn't always work out that way. Hope this helps even though it doesn't answer your question directly.

Yes it did help and thank you. Sounds like you are at about the same cyl out put as me with good success . I would imagine the Manleys with the 2000 bolts would be around the same strength as the Eagles so maybe I will be ok with them . Eagle told me there rods would handle 1500 hp.. That would be 750 for a 4 cyl. But if I ever am able to get the whole 1100 hp out of this turbo being a 4 cyl , that would be like a 2200 hp V8 right? Not even sure my motor could ever reach that , but would like to be prepared just in case..

[70 bird]

I think your pushing everything out to the edge. My guess is the block will let go first not the rods. I think your 4cyl. is a cool project, wish you the best.

[charlie66]

Originally Posted by 70 bird

I think your pushing everything out to the edge. My guess is the block will let go first not the rods. I think your 4cyl. is a cool project, wish you the best.

Thanks, I agree with you about the block being the next weakest link. But I'm still going to throw a little more at it.. If you ask me , there stronger then the V8 blocks.. No tug a war between banks going on... So far no signs of fatigue ..

[Tom Vaught]

Originally Posted by charlie66

If you ask me , there stronger then the V8 blocks.. No tug a war between banks going on... So far no signs of fatigue ..

Smart comment, Charlie, and in many ways true.

Figuring Horsepower per cubic inches:

An old Offy (Indy Car Turbo Engine - 159 cid) made 1100 hp in its prime on the dyno.
6.91 HP per cubic inch so a pretty good engine for its time.

For easy math, say your engine could make 5 hp per cubic inch times 194 cid. 970 horsepower for the engine. Your turbo could make 1100 hp (same as the Offy turbo).
No rocket science, maybe more durability today on the turbo.

But back to your deal of 750 -800 HP or 1/2 of a 1500-1600 hp 400 cid engine.
800 HP is 4.12 HP per cid and that is 60% of the HP capability of the Offy Engine which was designed for 500 mile Indy Car durability, so your goal is not that crazy really.

Marty made around 1600 hp with his 406 engine on Methanol (like the Offy Engine) with basic Diesel Turbo parts and cast iron heads (240-260 cfm) and a factory block.
3.94 HP per cid. 57% of the Offy power capability with good durability for 3 years.
A better IA block and it might have lived a lot longer.

So if you get a good Forged or Billet crank in the engine with good rods, and make 750-780 hp for a long time even with the 4 cylinder block and "No tug a war between banks going on..." 3500# Le Mans would run 9.70s at 135+ mph at Norwalk with a 4 cylinder engine.
Dave Johnson went into the 9s with his light weight 63 Tempest spinning the crap out of his 4 cylinder deal. You should have a lot more durability.

Tom V.