Ok Turbo Cam Masters!!
Joined: Nov 2001
Posts: 8,484
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From: Cecil County Raceway!!!
Stock stroke + 4.010 bore. Target boost is 3bar (29-30 psi).
Here is the compressor map:
http://www.turbobygarrett.com/turbob...pmap_large.gif
Consumption for a 364 @ a PR of 3.0 (3 bar) @ 7500 rpm is ~130-135 lb/min, putting it right on the ragged edge of that compressor map
Backpressure will probably be pretty brutal up there due to the smallish turbine...which I think will allow the slightly later IVC.
Here is the compressor map:
http://www.turbobygarrett.com/turbob...pmap_large.gif
Consumption for a 364 @ a PR of 3.0 (3 bar) @ 7500 rpm is ~130-135 lb/min, putting it right on the ragged edge of that compressor map
Backpressure will probably be pretty brutal up there due to the smallish turbine...which I think will allow the slightly later IVC.
Originally Posted by CHRISPY
Very interesting information guys!!
Fireball,
You kept the same stroke but increased bore right? What is your target boost level with the new setup and where does it shake out on the compressor map and consumption chart for your motor? I think that cam looks pretty good but you might peak a little higher with the 48ivc versus 46 provided the turbo is still in its efficiency range and backpressure not too high.
Fireball,
You kept the same stroke but increased bore right? What is your target boost level with the new setup and where does it shake out on the compressor map and consumption chart for your motor? I think that cam looks pretty good but you might peak a little higher with the 48ivc versus 46 provided the turbo is still in its efficiency range and backpressure not too high.
once I get my twin setup running I will test some cams on it
I am starting with a 234/234 598/598 116+4
the engine is a 403 CID with AFR 225 heads
turbos will either be the APS kit or twin 66mm
I am starting with a 234/234 598/598 116+4
the engine is a 403 CID with AFR 225 heads
turbos will either be the APS kit or twin 66mm
Originally Posted by Darren P
once I get my twin setup running I will test some cams on it
I am starting with a 234/234 598/598 116+4
the engine is a 403 CID with AFR 225 heads
turbos will either be the APS kit or twin 66mm
I am starting with a 234/234 598/598 116+4
the engine is a 403 CID with AFR 225 heads
turbos will either be the APS kit or twin 66mm
Peter
TECH Senior Member
Joined: Nov 2001
Posts: 10,341
Likes: 1
Originally Posted by Fireball
Stock stroke + 4.010 bore. Target boost is 3bar (29-30 psi).
Here is the compressor map:
http://www.turbobygarrett.com/turbob...pmap_large.gif
Consumption for a 364 @ a PR of 3.0 (3 bar) @ 7500 rpm is ~130-135 lb/min, putting it right on the ragged edge of that compressor map
Backpressure will probably be pretty brutal up there due to the smallish turbine...which I think will allow the slightly later IVC.
Here is the compressor map:
http://www.turbobygarrett.com/turbob...pmap_large.gif
Consumption for a 364 @ a PR of 3.0 (3 bar) @ 7500 rpm is ~130-135 lb/min, putting it right on the ragged edge of that compressor map
Backpressure will probably be pretty brutal up there due to the smallish turbine...which I think will allow the slightly later IVC.
You are right on the bleeding edge of the compressor map hehe
That combo is going to be nuts man you must be excited
Joined: Nov 2001
Posts: 8,484
Likes: 0
From: Cecil County Raceway!!!
Originally Posted by CHRISPY
You are right on the bleeding edge of the compressor map hehe
That combo is going to be nuts man you must be excited
That combo is going to be nuts man you must be excited
30 psi + 9:1 compression should be pretty nuts....can you say goodbye headgaskets
Originally Posted by Fireball
This is a very interesting thread. Its really got me thinking about my application...midframe 88 (GT47) on a 366 ci engine. Previous N/A testing with the Vic Jr manifold (at 346) suggested I wanted an IVC of ~46* ABDC to peak at 7200 rpm. Now that I've bumped up 20 ci, I think I can add ~2* to that value to keep me in the ballpark, so lets assume 48* ATDC. I know that the turbine side of the GT47 is a bit small, so 2:1 (maybe 2.5:1) pressure ratios are quite possible. So I probably want to minimize my total overlap at .050. For this argument, lets assume 0*. EVO of 56* seems to be a typical number for larger higher rpm cams (Trexish), so I'm going to keep it since these motors seem pretty forgiving when it comes to EVO. So if I want to close the exhaust a few degrees BTDC (4* for instance) gives me the following specs:
232/232 116+4
Any opinions?
232/232 116+4
Any opinions?
Originally Posted by Pro Stock John
Interesting logic stream but sadly I don't know all the terms you are using. Could you break the the acronyms down and dumb down your post for me? I am running a 234/234/113 cam, not sure if it's straight up or advanced. I think that converter and gearing are more important than the cam, assuming that some thought was initially and that the car is not extremely over or under cammed. I think it's a given that you would run more cam than a stock one for a stroker. I think the rationale behind not undercamming a stroker is that the smaller cam would decrease the efficiency of the bigger engine. If an engine can make 425rwhp with a bigger cam, then you can make all the right downstream choices like the turbo size(s).
Yeah, I was just thinking about it, and was like, if you build a 402ci 9:1 engine and then under cam it, so instead of a big 236/236 you put 206/218, what are you trying to accomplish. You keep a nice idle, but your engine horsepower is now the same as a smaller engine. So you might still need to boost up that bigger small-cammed engine as much as you would a smaller engine that makes as much power (though less torque).
Kurt Urban made this point to me a few years ago, that 15psi will double the engine horsepower. So if I make 450rwhp NA like say LastLS1, at 15 psi I am making like 900 hp. Shows the value of cubes and running enough turbo. But say you make 375rwhp like me on motor (just a guess, could be lower). At 15psi I am a 750rwhp car.
Seems to me that going up or down a little on cam won't make much of a difference, it's when folks run way too much or way too little cam that you start to reduce the effectiveness of the engine itself.
I'm sure someone better versed in turbos can make the point that its not that simple, and that you want to not go too crazy with turbo cam choices, but I have also heard 2-3 reputable tuners say that is not true, that you run race car cams in race cars regardless of whether they are turbo or not.
Kurt Urban made this point to me a few years ago, that 15psi will double the engine horsepower. So if I make 450rwhp NA like say LastLS1, at 15 psi I am making like 900 hp. Shows the value of cubes and running enough turbo. But say you make 375rwhp like me on motor (just a guess, could be lower). At 15psi I am a 750rwhp car.
Seems to me that going up or down a little on cam won't make much of a difference, it's when folks run way too much or way too little cam that you start to reduce the effectiveness of the engine itself.
I'm sure someone better versed in turbos can make the point that its not that simple, and that you want to not go too crazy with turbo cam choices, but I have also heard 2-3 reputable tuners say that is not true, that you run race car cams in race cars regardless of whether they are turbo or not.
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Originally Posted by Pro Stock John
Yeah, I was just thinking about it, and was like, if you build a 402ci 9:1 engine and then under cam it, so instead of a big 236/236 you put 206/218, what are you trying to accomplish. You keep a nice idle, but your engine horsepower is now the same as a smaller engine. So you might still need to boost up that bigger small-cammed engine as much as you would a smaller engine that makes as much power (though less torque).
Kurt Urban made this point to me a few years ago, that 15psi will double the engine horsepower. So if I make 450rwhp NA like say LastLS1, at 15 psi I am making like 900 hp. Shows the value of cubes and running enough turbo. But say you make 375rwhp like me on motor (just a guess, could be lower). At 15psi I am a 750rwhp car.
Seems to me that going up or down a little on cam won't make much of a difference, it's when folks run way too much or way too little cam that you start to reduce the effectiveness of the engine itself.
I'm sure someone better versed in turbos can make the point that its not that simple, and that you want to not go too crazy with turbo cam choices, but I have also heard 2-3 reputable tuners say that is not true, that you run race car cams in race cars regardless of whether they are turbo or not.
Kurt Urban made this point to me a few years ago, that 15psi will double the engine horsepower. So if I make 450rwhp NA like say LastLS1, at 15 psi I am making like 900 hp. Shows the value of cubes and running enough turbo. But say you make 375rwhp like me on motor (just a guess, could be lower). At 15psi I am a 750rwhp car.
Seems to me that going up or down a little on cam won't make much of a difference, it's when folks run way too much or way too little cam that you start to reduce the effectiveness of the engine itself.
I'm sure someone better versed in turbos can make the point that its not that simple, and that you want to not go too crazy with turbo cam choices, but I have also heard 2-3 reputable tuners say that is not true, that you run race car cams in race cars regardless of whether they are turbo or not.
Originally Posted by Pro Stock John
Interesting logic stream but sadly I don't know all the terms you are using. Could you break the the acronyms down and dumb down your post for me?
ABDC - After bottom dead center
ATDC - After top dead center
EVO - Exhaust Valve open
BTDC - Before top dead center
Thanks Real, and why do folks mess with the numbers, to get more cylinder pressure?
Web, a bigger cam with a blower setup will be worth 20-40hp over a stock cam for sure. Turbo folks however look at the duration and try to curtail the amount of duration if they think they will run out of turbo. Turbo folks are much more focused on efficiency of the system.
Web, a bigger cam with a blower setup will be worth 20-40hp over a stock cam for sure. Turbo folks however look at the duration and try to curtail the amount of duration if they think they will run out of turbo. Turbo folks are much more focused on efficiency of the system.
Joined: Nov 2001
Posts: 8,484
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From: Cecil County Raceway!!!
Originally Posted by Pro Stock John
Thanks Real, and why do folks mess with the numbers, to get more cylinder pressure?
These 4 numbers dictate alot, overlap, where the motor will make peak power, etc...
Joined: Nov 2001
Posts: 8,484
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From: Cecil County Raceway!!!
Originally Posted by Pro Stock John
Cool, so Brian, what values would you need assuming an engine had a peak rpm of 7500 rpm? How about 6500 rpm?
My first post in this thread gave my initial thoughts on the matter...
THe only valve event I really have any direct testing of was the IVC. THe overlap events (IVO and EVC) were based on what I ascertained from this thread as a starting guess.
EVO was based on typical larger cam numbers (though I don't think its a very sensitive number)
TECH Senior Member
Joined: Nov 2001
Posts: 10,341
Likes: 1
Originally Posted by Fireball
Have you ever known me to do something NOT on the bleeding edge
30 psi + 9:1 compression should be pretty nuts....can you say goodbye headgaskets
30 psi + 9:1 compression should be pretty nuts....can you say goodbye headgaskets
Can't wait to see it up and running!
