Lost in Computer Aided Engine Building
Thread Starter
Racer
Joined: Oct 2000
Posts: 491
Likes: 12
From: Los Altos Hills, CA
Lost in Computer Aided Engine Building
I have using DD2000 to design a 374 small block (4.125 bore x 3.5 stroke). I am seeing really nice numbers with AFR 210cc heads (full competition port), a single plane, and just about any roller cam with .575ish lift, 238ish duration, and 112LSA.
In fact, the numbers are so good, I don’t believe them. I know DD2000 is optimistic, but 560HP at 6500RPM yet still providing 400 ft-lbs at 2000RPM???
I have a friend running EA3.0 on the motor and those numbers are not even close to DD2000, but we may not have the right parameters for things like flow efficiency for the heads.
I’d like to start tweaking the cam specs for the motor, but I don’t have any confidence in the numbers. Garbage in, garbage out.
Any words of wisdom from cyber-engine builders out there?
In fact, the numbers are so good, I don’t believe them. I know DD2000 is optimistic, but 560HP at 6500RPM yet still providing 400 ft-lbs at 2000RPM???
I have a friend running EA3.0 on the motor and those numbers are not even close to DD2000, but we may not have the right parameters for things like flow efficiency for the heads.
I’d like to start tweaking the cam specs for the motor, but I don’t have any confidence in the numbers. Garbage in, garbage out.
Any words of wisdom from cyber-engine builders out there?
Melting Slicks
Joined: Oct 2002
Posts: 3,193
Likes: 1
From: Cincinnati Oh
You can edit the flow numbers for the heads - but one common mistake is not getting the cam specs inserted right so you might want to double-check whether or not you need to insert seat-to-seat duration relative to the intake opening, etc. I know when I used it I had to tinker a bit to get more realistic numbers...
take it with a grain of salt though. I think it's more of a relative comparison than "actual" - but I threw in some numbers of my last build and it was a reasonable approximation (still a little high though).
take it with a grain of salt though. I think it's more of a relative comparison than "actual" - but I threw in some numbers of my last build and it was a reasonable approximation (still a little high though).
Thread Starter
Racer
Joined: Oct 2000
Posts: 491
Likes: 12
From: Los Altos Hills, CA
Danno85: I'm running the intake and exhaust lobe center angles at 112 degrees. Compresssion is 10.6:1, the motor is carbed with a 750CFM and a single plane intake. Exhaust is large tube headers through mufflers.
Ramanstud: After reading the manual, DD2000 does all their simulations with seat-to-seat numbers. If you input .050 numbers it does a calculation to get the seat-to-seat numbers. They recommend using seat-to-seat for the most accurate simulations. I've tried fooling with seat-to-seat numbers and you don't have to work too hard to see the same high numbers. I'll play with this a little more to try to understand the differences.
Ramanstud: After reading the manual, DD2000 does all their simulations with seat-to-seat numbers. If you input .050 numbers it does a calculation to get the seat-to-seat numbers. They recommend using seat-to-seat for the most accurate simulations. I've tried fooling with seat-to-seat numbers and you don't have to work too hard to see the same high numbers. I'll play with this a little more to try to understand the differences.
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,444
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
use cam type of dual purpose and use the cam cards .050 valve event numbers. Plug in the CFM air flow for your heads at all the lift points.
Even if it's 5-10% high who cares, it gets you thinking about how the cam and heads work.
Even if it's 5-10% high who cares, it gets you thinking about how the cam and heads work.
Thread Starter
Racer
Joined: Oct 2000
Posts: 491
Likes: 12
From: Los Altos Hills, CA
gkull:
I'm just concerned that the shape of the curves is right. I'm OK with the numbers being shifted up or down (more likely down) 5 or 10%. If the 374 can get the torque up at 2000RPM with AFR210's that would be great.
I'm just concerned that the shape of the curves is right. I'm OK with the numbers being shifted up or down (more likely down) 5 or 10%. If the 374 can get the torque up at 2000RPM with AFR210's that would be great.
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,444
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
Do all your sim. runs with know values from cam cards. I do know that DD2000 overly awards the use of high amounts of split duration on the exhaust side.
Custom cam actually means getting lobe profiles out of their list of existing profiles. They do allow you to determine your valve event numbers for a given duration lobe. I had a 236/242 with 112 lc made for my 383 because the 240/248 112 lc was to much with higher ratio rockers
I'm sure why you would want a 3.5 stroke. Smokedtires on this forum built a 3.600 or 3.6200 X 4.155 for something like 388 ci. I can tell you now that when the cost to build is the same you might as well make it 440 ci small block and just blow the doors off any of those wimpy sub 396 ci motors
Custom cam actually means getting lobe profiles out of their list of existing profiles. They do allow you to determine your valve event numbers for a given duration lobe. I had a 236/242 with 112 lc made for my 383 because the 240/248 112 lc was to much with higher ratio rockers
I'm sure why you would want a 3.5 stroke. Smokedtires on this forum built a 3.600 or 3.6200 X 4.155 for something like 388 ci. I can tell you now that when the cost to build is the same you might as well make it 440 ci small block and just blow the doors off any of those wimpy sub 396 ci motors
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Thread Starter
Racer
Joined: Oct 2000
Posts: 491
Likes: 12
From: Los Altos Hills, CA
gkull, thanks. I think I'm going to need a dyno plot from a known 377 that I can base my simulations on. It's hard finding all the pertinent data like detailed flow numbers with the dyno data.
I'm going to try the 374 first. I'm a big fan of the bigger motors, I've researched them to death. But I'll start at 374 and move up from there. This is my first motor build so I'll be conservative. If I can scratch out 500HP from the 374 that should be enough.......for now.
BTW, if anyone has a big bore, short stroke out there that has been dynoed, please weigh in. I'll get it on DD2000 and see how well the cyber world matches the real world.
I'm going to try the 374 first. I'm a big fan of the bigger motors, I've researched them to death. But I'll start at 374 and move up from there. This is my first motor build so I'll be conservative. If I can scratch out 500HP from the 374 that should be enough.......for now.
BTW, if anyone has a big bore, short stroke out there that has been dynoed, please weigh in. I'll get it on DD2000 and see how well the cyber world matches the real world.
Le Mans Master
Joined: Apr 2000
Posts: 7,562
Likes: 9
From: B'Ville NY
Cruise-In III Veteran
St. Jude Donor '05
Gkull is correct, mines a 388 (4.125x 3.625). I got a killer deal on a Bryant billet crank which pointed me in this direction for my build. Its been a blast to drive so far, but I haven't yet had it actually dyno'd.
Here's what DD2000 says about my setup:
You can see more on my website in my sig at the buildup page.
Here's what DD2000 says about my setup:
You can see more on my website in my sig at the buildup page.
Thread Starter
Racer
Joined: Oct 2000
Posts: 491
Likes: 12
From: Los Altos Hills, CA
SmokedTires:
Man those are great numbers. I don't see quite those levels for the 374, but the shape is the same. Good low end torque and really nice HP. Does it feel like it has 400ft-lbs of torque at 2000??? Does it really have 14" of vacuum at 2000?
You need to get your car on a rear wheel dyno! Inquiring minds want to know.
Man those are great numbers. I don't see quite those levels for the 374, but the shape is the same. Good low end torque and really nice HP. Does it feel like it has 400ft-lbs of torque at 2000??? Does it really have 14" of vacuum at 2000?
You need to get your car on a rear wheel dyno! Inquiring minds want to know.
we do
Le Mans Master
Joined: Apr 2000
Posts: 7,562
Likes: 9
From: B'Ville NY
Cruise-In III Veteran
St. Jude Donor '05
Hopefully I'll get it on a chassis dyno at some point this summer, I've just had way to many things going on, barely even drove it last year 
I'll be sure to post when I get to it
I'll be sure to post when I get to it
Le Mans Master
Joined: Feb 1999
Posts: 5,877
Likes: 1
From: Park Ridge IL
I used DD2000 to help build a 650hp NA SBC 427 about 5 years ago and a 1200hp twin turbo SBC 427 and the predicted numbers were within 1-2% of the actual numbers from a Superflow 600 dyno. I built a pair of 700hp BBC 540's 3 years ago for my boat and the predicted numbers were within the same tolerance. In both cases, almost all of the predictions were within 5hp or 5 tq at a given rpm point.
The key, in my opinion, was using flow bench verified flow numbers, verified compression ratio, and actual cam specs as mentioned. I'm using DynoSim Advance with Pro Tools now to build a twin turbo 427 ci LS7x based off of the new World Products LS7X aluminum block and 12* heads. As soon as the heads ship we're gonna flow them and start coming up with some predictions. Should have real world dyno results next spring.
The key, in my opinion, was using flow bench verified flow numbers, verified compression ratio, and actual cam specs as mentioned. I'm using DynoSim Advance with Pro Tools now to build a twin turbo 427 ci LS7x based off of the new World Products LS7X aluminum block and 12* heads. As soon as the heads ship we're gonna flow them and start coming up with some predictions. Should have real world dyno results next spring.
Thread Starter
Racer
Joined: Oct 2000
Posts: 491
Likes: 12
From: Los Altos Hills, CA
Monty:
Thanks for weighing in. I will flow my heads and cc my combustion chambers for compression.
I'm a design (electrical) engineer so I'm curious to see if I can really design a motor with these tools. After it's all done, I will dyno the motor and compare the results.
Thanks for weighing in. I will flow my heads and cc my combustion chambers for compression.
I'm a design (electrical) engineer so I'm curious to see if I can really design a motor with these tools. After it's all done, I will dyno the motor and compare the results.
Intermediate
Joined: Apr 2006
Posts: 45
Likes: 0
Originally Posted by Cris
Monty:
Thanks for weighing in. I will flow my heads and cc my combustion chambers for compression.
I'm a design (electrical) engineer so I'm curious to see if I can really design a motor with these tools. After it's all done, I will dyno the motor and compare the results.
Thanks for weighing in. I will flow my heads and cc my combustion chambers for compression.
I'm a design (electrical) engineer so I'm curious to see if I can really design a motor with these tools. After it's all done, I will dyno the motor and compare the results.
What you'll want to do is to model a setup of a known engine close to the specs of the engine you want to bluild. Compare notes as to how the DD2000 program differed from the real engine, then figure out why. EA3.0 does a lot better job of modeling the cam-shaft, while the DD2000 will wildly approximate the camshaft. If you plan on using a extreme high lift/high rate cam, DD result will vary wildly. According to DD my engine makes 520 hp and peaks at 6000 rpm. RWHP is at 350 hp and at 6000...needs tunning, excuse,excuse, etc...
One of the things to look at are the $4K investment in AFR 210 heads versus $2K AFR 195 heads. Of course different cams, but start with a reference cam that someone else is running.
You'll find very quickly, that the power available comes from the heads and not the displacement. You'll find that displacement will move the power band down. (EI 327 ci with AFR 210 won't make max hp for 7/8K rpms)
Thread Starter
Racer
Joined: Oct 2000
Posts: 491
Likes: 12
From: Los Altos Hills, CA
Gamewood:
I am trying to pull any data I can find on the big bore, short stroke motors. Since the 383 is at least close in displacement, I have been modeling some known builds on them. The latest is a set of dyno results just published in Chevy High Performance. They are doing dyno tests on six cams. DD2000 hit the peak horsepower number right on but was 15% high on the 2500 RPM torque value. I have also done modeling on a friend's 415 ci small block and see a similar trend. DD2000 seems to overestimate the low RPM torque values. Once you are above the torque peak everything starts to match up nicely.
Not sure about your comments re the 195's and 210's. They are the same cost. However, I've actually switched my order with AFR. They are just releasing their new line of heads. The new 195's are supposed to hit 300CFM at .6" lift. They also use a narrower valve stem for lighter weight. More flow, less area than the old 210's.......sign me up.
I am trying to pull any data I can find on the big bore, short stroke motors. Since the 383 is at least close in displacement, I have been modeling some known builds on them. The latest is a set of dyno results just published in Chevy High Performance. They are doing dyno tests on six cams. DD2000 hit the peak horsepower number right on but was 15% high on the 2500 RPM torque value. I have also done modeling on a friend's 415 ci small block and see a similar trend. DD2000 seems to overestimate the low RPM torque values. Once you are above the torque peak everything starts to match up nicely.
Not sure about your comments re the 195's and 210's. They are the same cost. However, I've actually switched my order with AFR. They are just releasing their new line of heads. The new 195's are supposed to hit 300CFM at .6" lift. They also use a narrower valve stem for lighter weight. More flow, less area than the old 210's.......sign me up.